Programme and Abstract Volume

38th Annual MeetingMineral Deposit Studies Group

Southampton 7-19 December 2014

National Oceanography Centre SouthamptonUniversity of Southampton

United Kingdom

MDSG 2014 would like to thank the following sponsors

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Contents:

Welcome 1 Visitor WiFi 2 Conference Programme 3 Abstract Volume 11 Delegate List 88 Useful Maps 92

Welcome:

Welcome to the 38th Annual Winter Meeting of the Mineral Deposits Studies Group

held at the National Oceanography Centre Southampton, 17-19 December 2014. As

ever the meeting has attracted a great response from industry and academia, with

more than 150 registrants. Included in the registration we have more than 20

different mineral resource companies and consultancies and 35 PhD students from

14 different universities, including delegates from mainland Europe.

Generous sponsorship from 8 major sponsors has enabled us to keep the costs of

registration for the PhD, MSc and MSci Students to a very attractive level and

ensured that in addition to the 7 Keynote Speakers we have 26 presentations and

more than 40 poster presentations, many from students.

Hopefully the meeting will provide an intellectual stimulus as we ease down into the

Christmas Break and inspire your endeavours in the New Year!

Best wishes,

Steve and the “MDSG Team”.

Robert Knight, Alex Webber, Pierre Josso, Katie McFall, Matthew Hodgkinson, Holly

Elliot

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Conference Programme - 38th Annual MDSG Meeting, Southampton - 17-19 December 2014

Wednesday 17th December 2014

18.00 Registration Opens - National Oceanography Centre Southampton

18.30 Ice Breaker

19.15 KEYNOTE : Bob Foster (Stratex)

Science and the City - Status of the Gold Industry

20.00 Ice Breaker Continued…..

21.00 End

Thursday 18th December 2014

08.00 Registration - National Oceanography Centre Southampton

SESSION: TECTONICS AND Pb-Zn MINERALIZATION

08.45 KEYNOTE : John Walsh (University College Dublin)

Structural Controls on Ore Formation; The Irish Zn-Pb Deposits

09.25 Philip Bird (Kingston University) STUDENT

Lithological and Microstructural Controls on Mineralisation at the Kibali Gold Project, NE Democratic Republic of the Congo

09.40 Edward Dempsey (University of Durham)

The North Pennines Orefield - Investigating Early Permian Mineralization and Transtension using Rhenium/Osmium Isotope Geochemistry

09.55 Cyril Chelle-Michou (University of Geneva)

Reassessment of Pb Isotope Geochemistry on the Pb-Zn Deposits in Northern Baltica: Hydrocarbon Source Rocks also Contribute to the Metal Endowment

10.10 Nicolas Saintilan (University of Geneva) STUDENT

Source and Role of Extrinsic Hydrocarbons at the MVT Pb-Zn Laisvall Deposit, Sweden

4

10.25 TEA BREAK

10.50 Welcome Professor Rachael Mills – Head of Ocean and Earth Science

SESSION: ISOTOPES AND ORE FORMATION

10.55 KEYNOTE : Adrian Boyce (SUERC)

What Have Stable Isotopes Ever Done for My Ore Deposit?

11.35 James Lambert-Smith (Kingston University)

Evaporite Derived Hypersaline Ore Fluids in Orogenic Gold: New Boron Isotope Data from Tourmaline in the Loulo-Bambadji District in Mali, West Africa

11.50 Li Yang (University of Durham) STUDENT

Lifespan and Fluid Evolution for Magmatic-Hydrothermal Systems: A U-Pb, Re-Os and O Isotope Case Study from Qulong Porphyry Cu-Mo Deposit, Tibet

12.05 Paul Dennis (University of East Anglia)

Clumped Isotope Constraints on Water:Rock Ratios and the Evolution of Fluids Associated with Late Variscan Hydrothermal Veins and Mineralization

12.20 Kathryn Goodenough (British Geological Survey)

Massive Sulphide Deposits of the Central Jebilet Massif, Morocco

12.35 Mineral Deposits Studies Group AGM

12.50 LUNCH & POSTERS

SESSION: MAGMATIC PROCESSES AND ORE FORMATION

13.35 KEYNOTE : Tom Gernon (University of Southampton)

Diamond Eruptions

14.15 Holly Elliot (University of Southampton) STUDENT

Diatreme Volcanism and Pb-Zn Mineralisation in the Limerick District of the Irish Orefield

14.30 Hannah Hughes (Cardiff University) STUDENT

Sulphide Slumping in Magma Conduits: Evidence from the North Atlantic Igneous Province of Scotland and Greenland

5

14.45 Bartosz Karykowski (Cardiff University) STUDENT

Key Characteristics of the Magmatic Cu-Ni-PGE Mineralisation at Manchego, West Musgrave Province, Western Australia

15.00 Robert Sievwright (Imperial College, London) STUDENT

Magnetite Crystallisation as a Control of Mineral-Melt Partitioning of Divalent Cations

15.15 TEA BREAK & POSTERS

SESSION: FLUIDS AND ORE FORMATION/RECOVERY

15.40 KEYNOTE : Bruce Yardley (University of Leeds)

Metal Transport in Fluids: Brines and Not-Brines

16.20 Iain Pitcairn (Stockholm University)

Regional Carbonate Alteration in the Eastern Desert of Egypt: Fluid Sources and Implications for Formation of Gold Deposits

16.35 Gawen Jenkin (University of Leicester)

Novel Environmentally-friendly Ore Processing Techniques for the 21stC

16.50 Eloise Harman (Natural History Museum)

Toward the Development of Automated Mineral Identification with the Zeiss Mineralogic Platform for the Routine Analysis of Mineral Exploration Samples by Laser Ablation Inductively-Coupled-Plasma Mass Spectrometry

17.05 POSTERS & DRINKS RECEPTION

19.00 Depart for St Marys Stadium

19.30 Conference Dinner at St Marys Stadium

Friday 19th December 2014

SESSION: PORPHYRIES AND THE SEA FLOOR PART 1

09.00 KEYNOTE : Steve Sparks (University of Bristol)

Volcanic Processes in the Formation of Porphyry Copper Deposits

6

09.40 Katie McFall (University of Southampton) STUDENT

Are Re Concentrations in Porphyry Copper Deposits the Result of Hydrothermal Fluid-Country Rock Interactions? Evidence from Stable Isotope Analyses (δ34S, δ18O, δD) of the Muratdere Cu-Mo (Au-Re) Porphyry Deposit, Turkey

09.55 Alex Webber (National Oceanography Centre)

Supercritical Venting and VMS Formation at the Beebe Hydrothermal Field, Cayman Spreading Centre

10.10 Matthew Hodgkinson (University of Southampton) STUDENT

Talc Mounds on the Mid-Cayman Spreading Centre

10.25 TEA BREAK

SESSION: CRITICAL ELEMENTS AND THE SEA FLOOR PART 2.

10.55 KEYNOTE : Phil Weaver (Seascape Consultants)

Sea Floor Mining, Challenges and Opportunities

11.35 Clifford Patten ( Stockholm University) STUDENT

Behaviour of Au, As, Sb, Se and Te During the Hydrothermal Alteration of the Oceanic Crust: a Study Case from IODP Site 1256D

11.50 Robert Knight (University of Southampton)

The Geochemistry and Oxidation of Seafloor Massive Sulphide Deposits: Implications for Global Seafloor Resources and Mining

12.05 Pierre Josso (University of Southampton) STUDENT

Umbers of the Troodos Ophiolite, Cyprus: A Potential Rare Earth Resource?

12.20 Éimear Deady (British Geological Survey)

Valorisation of Waste Material - Rare Earth Elements in Red Muds: The Potential of European Resources

12.35 LUNCH

SESSION: INNOVATION AND MINERAL EXPLORATION

13.25 Linda Campbell (University of Manchester)

Regional Prospecting: Can We Couple Large-Scale Exploration Data with Novel Geochemical Discrimination?

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13.40 Dermot Smyth (LonMin PLC)

Lonmin Plc Exploration in Northern Ireland - The Contribution of Mineral Exploration to New Observations in Regional Geology

13.55 Alan Vaughan (Midland Valley Exploration)

Geological Application for the New Fault Response Modelling Module in Move

14.10 Ryan Bartlett (Barrick Exploration)

The Lumwana Basement-Hosted Cu-Deposits: Recent Developments Following 2012's Largest Resource Definition Program

14.25 PRIZES

14.35 CLOSING REMARKS

14.45 TEA & DEPARTURES

POSTER PRESENTATIONS

Giuseppe Arfé (Università di Napoli) STUDENT Effects of Arid to Hyperarid Conditions on the Secondary Enrichment of the Capricornio (Chile) Epithermal Au-Ag-Cu Mineralization Paul Armitage (Paul Armitage Consulting Ltd) The Amikoq PGE Deposit – Tectonic Fragments of an Archaean Layered Mafic Intrusion in the Fiskefjord Region, Southern West Greenland

Renata Barros (University College Dublin) STUDENT Characterization and Petrogenetic Implications for LCT Pegmatites and Associated Rocks in Southeast Ireland

Robin-Marie Bell (Geological Survey of Denmark and Greenland) STUDENT Structural and Mineralogical Characteristics of Nalunaq Gold Deposit, South Greenland: Implications for Gold Location

Sebastian Betton (University of Leicester) STUDENT

Geochemistry and Origin of Manganese Nodules from the Western Pacific

Philip Bird (Kingston University) STUDENT

Dating the Kibali Gold Project: Contrasting Zircon and Monazite Ages

8

Martin Black (presented by Jon Nadan - British Geological Survey) Recent Hydrothermal Base Metal Sulfide Mineralisation, Milos Island, Greece: A ‘Modern’ Analogue Model for Shallow Marine Arc-Related Deposits?

Delia Cangelosi (University of Leeds) STUDENT

Hydrothermal HREE Enrichment in the Huanglongpu Deposit, China

Olivia Chant-Tuft (Imperial College London) STUDENT The New South West Extension-South (SWEXS) Mineralisation of the Giant Navan Carbonate-Hosted Zn-Pb Deposit: Testing the Sub-Sea Floor Replacement Paradigm

Cyril Chelle-Michou (University of Geneva) On the Role of Petrological Cannibalism in the Genesis of the Coroccohuayco Porphyry-Skarn Deposit, Peru

Jake Clark (University of Leicester) STUDENT Geochemical and Mineralogical Styles of the Low Sulphidation, Epithermal Au-Ag Deposits of Sahinli, Western Turkey

Edward Cromwell (University of Durham) STUDENT Host Rock Characteristics and Controls on Cu-Au-Ag Mineralization at Copper Mountain Porphyry Deposit, Southern BC, Canada

Éimear Deady (British Geological Survey) The Key to Understanding Antimony Mineralisation in South West England — the North Herodsfoot Mine?

Andrew Dobrzański (University of Durham) STUDENT Mineral Textures Produced from a Fe/Mg/Ca-rich Fluid at Low CO2 Pressure (<10MPa) / Low Temperature (<125˚C) Conditions

Maxime Evrard (University of Liège) STUDENT Geophysical Approach of the Lead-Zinc Mineralization the Synclinorium of Verviers (Belgium)

Emily Fallon (University of Bristol) STUDENT

Galvanic Dissolution of Seafloor Sulphide Ore Deposits

Harry Fisher (Imperial College London) STUDENT The Chemistry of Chlorite and Epidote within the Propylitic Alteration Zone of the Lagalochan Porphyry Cu-Au-Mo Prospect, Argyll, Scotland

Benjamin Francis-Smith (University of Leicester) STUDENT Mineralogy of the Newly Recognised Dolerite-Associated IOCG-s of the Western Cloncurry District, NW Queensland, Australia

9

Amy Gilmer (University of Bristol) STUDENT Pulsed Intrusive Activity and Magma Mixing in the Don Manuel Porphyry Copper System, Central Chile

Shaun Graham (presented by Licia Santoro - Università di Napoli STUDENT) Mineralogic SEM-EDS Automated Mineralogy: A Preliminary Study on the Quantitative Mineral Classifications and Measured Assay

Matthew Grimshaw (University of Leeds) STUDENT

The Evolution of Gold Bearing Veins in the Klondike, Yukon, Canada

Cameron Hooper (University of Leicester) STUDENT A New Petrographic Study of Orogenic Gold Mineralization in the Castromil Prospect, Northwest Portugal

Hannah Hughes (Cardiff University) STUDENT Scottish Caledonian Mafic Magmatism: An Analogy to Alaskan-Type Complexes and PGE Mineralisation?

Kate Jillings (Imperial College London) STUDENT Determining the Genetic Relationship between Breccia and Magmatic Deposit at the Sakatti Deposit, Finland

Simon Kocher (Imperial College London) STUDENT Using High Resolution SEM to Identify Daughter Crystals in Fluid Inclusions from the Bingham Canyon Porphyry Deposit, Utah

Claudia Lepp (University of Leicester) STUDENT Lithological and Mineralogical Controls on the Surface Geochemistry of Epithermal and Porphyry Prospects, Kiziltepe Gold Corridor, Turkey

Amaya Menendez (National Oceanography Centre Southampton) STUDENT Geological Constraints on Rare Earth Elements (REEs): Concentrations in Deep Sea Clays from the Nares Abyssal Plain

Nicola Mondillo (presented by Maria Boni - Università di Napoli) Polymetallic Zn-Pb Mineralization in the Cuzco Area (Peru): Lead Isotope Geochemistry in the Accha-Larisa District

Charlie Moon (University of Exeter) Tellus South West: Relevance to Mineral Exploration and Deposit Models, an Initial View

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David Neave (University of Cambridge) On the Feasibility of Detecting Carbonatite-Hosted Rare Earth Element (REE) Deposits Using Remote Sensing: A Work in Progress

Cláudio Paulo (Universidade do Porto) STUDENT A PhD Study on the Controls of Au-As Mineralization at the Lagares Project, Northern Portugal

Rebecca Perkins (University of Oxford) STUDENT The Nature and Origin of Hydrothermal Gold Mineralisation at the Rex Pit, Damang Mine, Ghana

Carmen Pinto-Ward (Imperial College London) STUDENT Controls on the Rare Earth Element Enrichment at the Serra Verde Ion Adsorption REE Deposit, Goias, Brazil

Richard Prasser (University of Leicester) STUDENT Geochemical and Mineralogical Data across the Platinova Reef and its Implications for the Genesis of Discrete, Offset, Precious Metal-Enriched Horizons

Simon Richards (University of Leicester) STUDENT

Chlorine Partitioning in Magmas and the Formation of Porphyries

Licia Santoro (Università di Napoli) STUDENT Stable Isotopes (C-O) from the Supergene Nonsulfide Zn Prospect of Reef Ridge, Alaska

Pertti Sarala (Geological Survey of Finland)

Portable XRF for Mineral Exploration Geochemistry in Till

Robert Selwyn (University of Leicester) STUDENT Regional Geochemistry and Characteristics of Gold Mineralisation in Castromil and Serra da Quinta, Northern Portugal

Rebecca Strachan (University of Leicester) STUDENT Structural and Lithological Controls on Gold Mineralisation at the Wassa Mine, Ghana

Adam Taylor (University of Leicester) STUDENT Geochemical and Mineralogical Characterisation and Ore Genesis of Red-Bed Mineralisation at Gipsy Lane Brick Pit, Leicester

Li Yang (Durham University) STUDENT Lifespan and Fluid Evolution for Magmatic-Hydrothermal Systems: A U-Pb, Re-Os and O Isotope Case Study from Qulong Porphyry Cu-Mo Deposit, Tibet

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Abstract Volume Contents

Author(s) Title Page

Arfé et al. Effects of Arid to Hyperarid Conditions on the Secondary Enrichment of the Capricornio (Chile) Epithermal Au-Ag-Cu Mineralization

15

Armitage and McDonald

The Amikoq PGE Deposit – Tectonic Fragments of an Archaean Layered Mafic Intrusion in the Fiskefjord Region, Southern West Greenland

16

Barros et al. Characterization and Petrogenetic Implications for LCT Pegmatites and Associated Rocks in Southeast Ireland

17

Bartlett and Hatcher The Lumwana Basement-Hosted Cu-Deposits: Recent Developments Following 2012’s Largest Resource Definition Program

18

Bell and Kolb Structural and Mineralogical Characteristics of Nalunaq Gold Deposit, South Greenland: Implications for Gold Location

19

Betton et al. Geochemistry and Origin of Manganese Nodules from the Western Pacific

20

Bird et al. Lithological and Microstructural Controls on Mineralisation at the Kibali Gold Project, NE Democratic Republic of the Congo

21

Bird et al. Dating the Kibali Gold Project: Contrasting Zircon and Monazite Ages

22

Black et al. Recent Hydrothermal Base Metal Sulfide Mineralisation, Milos Island, Greece: A ‘Modern’ Analogue Model for Shallow Marine Arc-Related Deposits?

23

Boyce What Have Stable Isotopes Ever Done for My Ore Deposit? 24

Campbell et al. Regional Prospecting: Can We Couple Large-Scale Exploration Data with Novel Geochemical Discrimination?

25

Cangelosi et al. Hydrothermal HREE Enrichment in the Huanglongpu Deposit, China

26

Chant-Tuft et al. The New South West Extension-South (SWEXS) Mineralisation of the Giant Navan Carbonate-Hosted Zn-Pb Deposit: Testing the Sub-Sea Floor Replacement Paradigm

27

Chelle-Michou et al. Reassessment of Pb Isotope Geochemistry on the Pb-Zn Deposits in Northern Baltica: Hydrocarbon Source Rocks also Contribute to the Metal Endowment

28

Chelle-Michou and Chiaradia

On the Role of Petrological Cannibalism in the Genesis of the Coroccohuayco Porphyry-Skarn Deposit, Peru

29

Clark et al. Geochemical and Mineralogical Styles of the Low Sulphidation, Epithermal Au-Ag Deposits of Sahinli, Western Turkey

30

Cromwell et al. Host Rock Characteristics and Controls on Cu-Au-Ag Mineralization at Copper Mountain Porphyry Deposit, Southern BC, Canada

31

12

Deady and Moore Valorisation of Waste Material - Rare Earth Elements in Red Muds: The Potential of European Resources

32

Deady et al. The Key to Understanding Antimony Mineralisation in South West England — the North Herodsfoot Mine?

33

Dempsey et al. The North Pennines Orefield - Investigating Early Permian Mineralization and Transtension using Rhenium/Osmium Isotope Geochemistry

34

Dennis et al. Clumped Isotope Constraints on Water:Rock Ratios and the Evolution of Fluids Associated with Late Variscan Hydrothermal Veins and Mineralization

35

Dobrzański Mineral Textures Produced From A Fe/Mg/Ca-rich Fluid at Low CO2 Pressure (<10MPa) / Low Temperature (<125˚C) Conditions

36

Elliott et al. Diatreme Volcanism and Pb-Zn Mineralisation in the Limerick District of the Irish Orefield

37

Evrard et al. Geophysical Approach of the Lead-zinc Mineralization the Synclinorium of Verviers (Belgium)

38

Fallon et al. Galvanic Dissolution of Seafloor Sulphide Ore Deposits 39

Fisher et al. The Chemistry of Chlorite and Epidote within the Propylitic Alteration Zone of the Lagalochan Porphyry Cu-Au-Mo Prospect, Argyll, Scotland

40

Foster Status of the Gold Industry 41

Francis-Smith et al. Mineralogy of the Newly Recognised Dolerite-Associated IOCG-s of the Western Cloncurry District, NW Queensland, Australia

42

Gernon Diamond Eruptions 43

Gilmer et al. Pulsed Intrusive Activity and Magma Mixing in the Don Manuel Porphyry Copper System, Central Chile

44

Goodenough et al. Massive Sulphide Deposits of the Central Jebilet Massif, Morocco

45

Graham et al. Mineralogic SEM-EDS Automated Mineralogy: A Preliminary Study on the Quantitative Mineral Classifications and Measured Assay

46

Grimshaw The Evolution of Gold Bearing Veins in the Klondike, Yukon, Canada

47

Harman et al. Toward the Development of Automated Mineral Identification with the Zeiss Mineralogic Platform for the Routine Analysis of Mineral Exploration Samples by Laser Ablation Inductively-Coupled-Plasma Mass Spectrometry

48

Hodgkinson et al. Talc Mounds on the Mid-Cayman Spreading Centre 49

Hooper et al. A New Petrographic Study of Orogenic Gold Mineralization in the Castromil Prospect, Northwest Portugal

50

13

Hughes et al. Sulphide Slumping in Magma Conduits: Evidence from the North Atlantic Igneous Province of Scotland and Greenland

51

Hughes et al. Scottish Caledonian Mafic Magmatism: An Analogy to Alaskan-Type Complexes and PGE Mineralisation?

52

Jenkin et al. Novel Environmentally-Friendly Ore Processing Techniques for the 21stC

53

Jillings et al. Determining the Genetic Relationship between Breccia and Magmatic Deposit at the Sakatti Deposit, Finland

54

Josso et al. Umbers of the Troodos Ophiolite, Cyprus: A Potential Rare Earth Resource?

55

Karykowski et al. Key Characteristics of the Magmatic Cu-Ni-PGE Mineralisation at Manchego, West Musgrave Province, Western Australia

56

Knight and Roberts The Geochemistry and Oxidation of Seafloor Massive Sulphide Deposits: Implications for Global Seafloor Resources and Mining

57

Kocher et al. Using High Resolution SEM to Identify Daughter Crystals in Fluid Inclusions from the Bingham Canyon Porphyry Deposit, Utah

58

Lambert-Smith et al. Evaporite Derived Hypersaline Ore Fluids in Orogenic Gold: New Boron Isotope Data from Tourmaline in the Loulo-Bambadji District in Mali, West Afric

59

Lepp et al. Lithological and Mineralogical Controls on the Surface Geochemistry of Epithermal and Porphyry Prospects, Kiziltepe Gold Corridor, Turkey

60

Macaulay et al. Geological Application for the New Fault Response Modelling Module in Move

61

McFall et al. Are Re Concentrations in Porphyry Copper Deposits the Result of Hydrothermal Fluid-Country Rock Interactions? Evidence From Stable Isotope Analyses (δ34S, δ18O, δD) of the Muratdere Cu-Mo (Au-Re) Porphyry Deposit, Turkey

62

Menendez Geological Constraints on Rare Earth Elements (REEs): Concentrations in Deep Sea Clays from the Nares Abyssal Plain

63

Mondillo et al. Polymetallic Zn-Pb Mineralization in the Cuzco Area (Peru): Lead Isotope Geochemistry in the Accha-Larisa District

64

Moon Tellus South West: Relevance to Mineral Exploration and Deposit Models, an Initial View

65

Neave et al. On the Feasibility of Detecting Carbonatite-Hosted Rare Earth Element (REE) Deposits Using Remote Sensing: a Work in Progress

66

Pattern et al. Behaviour of Au, As, Sb, Se and Te During the Hydrothermal Alteration of the Oceanic Crust: a Study Case from IODP Site 1256D

67

14

Paulo et al. A PhD Study on the Controls of Au-As Mineralization at the Lagares Project, Northern Portugal

68

Perkins et al. The Nature and Origin of Hydrothermal Gold Mineralisation at the Rex Pit, Damang Mine, Ghana

69

Pinto-Ward et al. Controls on the Rare Earth Element Enrichment at the Serra Verde Ion Adsorption REE Deposit, Goias, Brazil

70

Pitcairn et al. Regional Carbonate Alteration in the Eastern Desert of Egypt: Fluid Sources and Implications for Formation of Gold Deposits

71

Prasser et al. Geochemical and Mineralogical Data across the Platinova Reef and its Implications for the Genesis of Discrete, Offset, Precious Metal-Enriched Horizons

72

Richards and Smith Chlorine Partitioning in Magmas and the Formation of Porphyries

73

Saintilan et al. Source and Role of Extrinsic Hydrocarbons at the MVT Pb-Zn Laisvall Deposit, Sweden

74

Santoro et al. Stable Isotopes (C-O) from the Supergene Nonsulfide Zn Prospect of Reef Ridge, Alaska

75

Sarala and Houlahan Portable XRF for Mineral Exploration Geochemistry in Till 76

Selwyn et al. Regional Geochemistry and Characteristics of Gold Mineralisation in Castromil and Serra da Quinta, Northern Portugal

77

Sievwright and Wilkinson

Magnetite Crystallisation as a Control of Mineral-Melt Partitioning of Divalent Cations

78

Smyth Lonmin Plc Exploration in Northern Ireland- The Contribution of Mineral Exploration to New Observations in Regional Geology

79

Sparks et al. Volcanic Processes in the Formation Porphyry Copper Deposits 80

Strachan et al. Structural and Lithological Controls on Gold Mineralisation at the Wassa Mine, Ghana

81

Taylor et al. Geochemical and Mineralogical Characterisation and Ore Genesis of Red-Bed Mineralisation at Gipsy Lane Brick Pit, Leicester

82

Walsh et al. Structural Controls on Ore Formation; The Irish Zn-Pb Deposits 83

Weaver Sea Floor Mining, Challenges and Opportunities 84

Webber et al. Supercritical Venting and VMS Formation at the Beebe Hydrothermal Field, Cayman Spreading Centre

85

Yang et al. Lifespan and Fluid Evolution for Magmatic-Hydrothermal Systems: A U-Pb, Re-Os and O Isotope Case Study from Qulong Porphyry Cu-Mo Deposit, Tibet

86

Yardley Metal Transport in Fluids: Brines and Not-Brines 87

15

Effects of Arid to Hyperarid Conditions on the Secondary Enrichment of the

Capricornio (Chile) Epithermal Au-Ag-Cu Mineralization

Giuseppe Arféa, Roberto Aielloa, Maria Bonia, Nicola Mondilloa, Dominik Soykb, and Vernon Arseneauc

a Dipartimento Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli, Italy,

pepparfe@hotmail.it, b Institut für Geowissenschaften, University Heidelberg, Germany, c Arena Minerals Inc., Cile.

The Capricornio epithermal gold-silver-copper deposit, in the Region II, Chile, consists of

multiple epithermal quartz-adularia-carbonate veins, ranging from 150-200 m a.s.l. to ~ 400 m in

depth. The veins are hosted in Paleocene and early Eocene mafic to felsic volcanic rocks, which

are hydrothermally altered.

The deposition of the primary mineralization at Capricornio was associated with several

Paleocene-Eocene magmatic episodes, similar to those which caused the deposition of the far

greater El Peñon deposit, in which individual mineralized shoots range from less than 1 km to 4

km in strike length, and measure up to 350 m in the down-dip direction. The primary ore

association at Capricornio is represented by base metals sulphides (galena, pyrite, chalcopyrite,

sphalerite, bornite), as well as by electrum, sulphoarsenides, sulphoselenides, sulphoantimonides

and Ag-sulphosalts.

In both the El Peñón and Capricornio deposits, the economic mineralization is mainly

concentrated in the supergene alteration zone. At El Peñon (1300 to 2000 m a.s.l.) the secondarily

enriched interval is developed for more than 350 m, while at Capricornio (980 m a.s.l) the

supergene alteration cannot be traced deeper than 150-200 m from the surface, and gold is

enriched mainly in the first 50 m. The reason for the difference in thickness of the supergene

alteration zone between El Peñon and Capricornio is probably associated with the variable levels

of uplift and erosion in the two mineralized districts, even if their structural setting and epithermal

characteristics were initially comparable.

Measured ages of supergene alunite from El Peñón and from other deposits in the region [1],

indicate that the weathering of the primary ores occurred already from 23 to 17 Ma, under a

semiarid to arid climate, prior to the onset of the hyperarid period. In this deposit secondary

electrum, which typically consists of over 95% Au, was produced from supergene processes that

caused the remobilization of silver.

Supergene processes, whose effects can be followed from the surface down to 150 m in depth,

have also affected the primary mineralization at Capricornio. Such processes have defined a

cementation zone, represented by a mineral association consisting of covelline, chalcocite,

cerussite, electrum (secondary) and acanthite, and an oxidation zone represented by peculiar

minerals, which have been traced from the surface down to 50 m in depth. This particular

association consists of chlorides (atacamite, boleite, cumengeite, herbertsmithite),

chlorocarbonates (phosgenite), chloroiodates (seeligerite), and halides (iodargyrite), which were

all probably deposited in extremely arid conditions. These conditions may have been present in

the area from the beginning of the hyperarid climate period [2] that started at 14 Ma, and

continued up to about 4-9 Ma along the coastal areas of South America.

References

[1] I. Warren et al. ”Geochronology of epithermal Au-Ag mineralization, magmatic-

hydrothermal alteration, and supergene weathering in the El Peñon district, northern

Chile”, Economic Geology, vol. 103, pp. 851-864, 2008.

[2] J. D. A. Clarke. “Antiquity of aridity in the Chilean Atacama Desert”, Geomorphology,

vol. 73, no. 1-2, pp. 101-114, 2006.

16

The Amikoq PGE Deposit – Tectonic Fragments of an Archaean Layered

Mafic Intrusion in the Fiskefjord Region, Southern West Greenland

Paul EB Armitagea, and Iain McDonaldb

a Paul Armitage Consulting Ltd, 1 Aster Drive, St Mary’s Island, Chatham, ME4 3EB, UK,

paul@thinkgeology.com, b School of Earth & Ocean Sciences, Cardiff University, UK.

Map-scale fragments of a layered mafic intrusion are dispersed throughout the Fiskefjord region

of southern West Greenland. A chain of fragments defines the Amikoq complex, comprised of

layered mafics between a basement of TTG gneisses and a roof of foliated amphibolites. Mafic

sheets, up to 150 m thick, are distributed around a north-south oriented, 25 km long ‘keel’ in

which the east and west sides mirror one another. This structure is broadly compatible with the

dome-and-basin architecture of the Fiskefjord region. Sampling in the region by Nuna Minerals

returned significant Pt+Pd concentrations around Amikoq and a joint venture with Impala

Platinum Holdings Ltd identified two PGE reefs.

The igneous stratigraphy is dominated by leuconorites interlayered with pegmatoidal feldspathic

pyroxenites and lenses of peridotite with occasional chromite seams. It is unclear if these are

related to similar ultramafic bodies in the roof amphibolites and basement gneisses. Igneous

layering dips to the west throughout Amikoq, except where folded and later east-west faults offset

the Amikoq stratigraphy. In the west, the basement and roof contacts are sheared at high

metamorphic grade with asymmetric folds indicating a top-to-northeast vergence. By contrast, the

northeast roof contact is a primary intrusive feature. In the southeast the basement contact is less

tectonised than in the west, and in the south virtually no shear is observed along the basement or

roof contacts. Two areas in the east display large-scale tight to isoclinal folds with steep axes.

Thus, strain may be partitioned between predominant contraction in the west and lateral shear in

the east. Despite the intensity of deformation and metamorphism, igneous layering is largely

preserved. In the west, a 2–4 m thick PGE reef occurs in the basal layers of a leuconoritic

package, which has been traced for approximately 2.5 km. In the far south, a <0.5 m thick reef

occurs at the base of a layered package of pegmatoidal feldspathic pyroxenites, which is traceable

over 500 m and faulted out at its north and south limits.

The southern reef shows a chondrite-normalised PGE curve with a peak at Rh. Scanning electron

microscopy of the most PGE-enriched samples, from the western and southern reefs, shows the

PGM to be frequently associated with tiny sulphides. Metal ratios are highly variable and gold

almost absent. Zircons are common in the pegmatoidal pyroxenites, and two zircon ages from the

north and south overlap within error at 2.95–3.03 Ga [2]. The textural relationships of the zircons

require further study in order to ascertain whether they represent the age of the Amikoq mafic

intrusion or a younger magmatic event.

Chondrite-normalised PGE patterns, Mg# and Cr concentrations around the Amikoq complex

reveal that the west and south represent different levels of an original intrusive body, or separate

intrusions. The south is characterised by a primitive mafic composition, whereas the west is

shown to be evolved. A smaller dataset for other parts of Amikoq suggests most of them are more

akin to the south and the west is therefore anomalous. Data for Amikoq-style mafic fragments

elsewhere in the region are insufficient to place them in context. North of Fiskefjord the layered

mafics are more deformed and often micaceous, probably reflecting slightly different post-

intrusion histories across the major Fiskefjord Fault.

References [1] A. Nutman, in P. E. B. Armitage. NunaMinerals A/S quarterly report, 31 July 2009. [2] M. K. M. Nilsson et al. “Precise U–Pb baddeleyite ages of mafic dykes and intrusions in southern West Greenland and implications for a possible reconstruction with the Superior craton”, Precambrian Research, vol. 183, pp. 399-415, 2010.

17

Characterization and Petrogenetic Implications for LCT Pegmatites and

Associated Rocks in Southeast Ireland

Renata Barrosa, Julian Menugea, Alessandra Costanzob, and Martin Feelyb

a School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland,

renata.barros@ucdconnect.ie, b Earth and Ocean Sciences, School of Natural Sciences, National University of Ireland Galway.

A lithium-rare metal (LCT) pegmatite belt occurs along the eastern margin of the Tullow

Lowlands pluton, part of the Caledonian Leinster Granite, in southeast Ireland. Despite the

indistinguishable (~400 Ma) ages of the pegmatites [1] and the Leinster Granite [2], and their

similar initial 87Sr/86Sr ratios [1], it is debatable whether these pegmatites represent residual

liquids after crystallization of the Leinster Granite or formed from separate partial melts from

similar source rocks [1, 3]. This work presents petrographic, mineral chemistry and fluid

inclusion data and their preliminary petrogenetic interpretation for LCT pegmatites and

associated rocks from two localities in the belt, Aclare and Moylisha.

LCT and barren pegmatites have variable grain sizes, from fine to very coarse grained, with

crystals reaching 40 cm. Mineral assemblages include spodumene (only in LCT), white mica,

quartz, albite, microcline, apatite and spessartine garnet, the last three present in minor amount.

Cassiterite, sphalerite and zircon are among the accessory minerals. Spessartine garnet, cassiterite

and sphalerite show zonation due to variations in Fe content. Patches and veins of albite-rich

aplite with accessory apatite and cassiterite are common within the pegmatite bodies. Textural

relationships show that euhedral garnet, subhedral spodumene (when present) and feldspars

represent an early phase of crystallization, followed by anhedral/interstitial garnet, apatite, an

occasional late generation of spodumene and two generations of late quartz.

Fluid inclusion (FI) petrography reveals the presence of primary and secondary liquid-rich two

phase fluid inclusions hosted in quartz, spodumene and garnet, within both mineralized and

barren pegmatites. Primary FIs in Aclare mineralized pegmatites show TH values of 130-310 °C

and salinity of 0.5-5 eq. wt. % NaCl. A barren Aclare pegmatite lacks FIs with salinity <8 eq. wt.

% NaCl, though low salinity FIs were found previously [3]. In contrast, FIs in Moylisha

mineralized and barren pegmatites have TH values of 180-330 °C with 1-26 eq. wt. % NaCl,

though spodumene-hosted FIs have maximum salinity of 10 eq. wt. % NaCl. At both localities,

preliminary TFM data suggest a significant CaCl2 component in FIs.

The Li mineralization is mainly hosted by spodumene and the metal may also be present in other

minerals such as white mica and Mn-bearing phosphates, but further investigation is required.

The presence of cassiterite and sphalerite indicates enrichment in Sn and Zn, which may also be

economically interesting. Fluid inclusion studies indicate the presence of several fluids during

pegmatite crystallization. Further study will be carried out to understand whether differences

observed between pegmatites in Aclare and Moylisha could indicate different genetic origins,

magmatic pulses and/or ages.

References

[1] P. J. O’Connor et al. “Genesis of lithium pegmatites from the Leinster Granite Margin,

southeast Ireland: geochemical constraints”, Geological Journal, vol. 26, pp. 295-305, 1991.

[2] P. J. O’Connor et al. “Isotopic U-Pb ages of zircon and monazite from the Leinster

Granite, Southeast Ireland”, Geological Magazine, vol. 126, no. 6, pp. 725-728, 1989.

[3] M. P. Whitworth, and A.H. Rankin. “Petrogenetic implications of garnets associated

with lithium pegmatites from SE Ireland”, Mineralogical Magazine, vol. 56, pp. 75-83, 1992.

18

The Lumwana Basement-Hosted Cu-Deposits: Recent Developments

Following 2012’s Largest Resource Definition Program

Ryan Bartletta, and Guy Hatchera

a Barrick Exploration, Lusaka, Zambia, ryan.bartlett.geo@gmail.com

Following the acquisition of the Lumwana Cu-deposits (proven and probable reserves of 539 Mt

@ 0.56% Cu, and measured and indicated resources of 487 Mt @ 0.5% Cu)[1] by Barrick Gold

Corporation in June 2011, the company embarked on a large (~300,000 m) resource definition

program on the Chimiwungo and Malundwe basement-hosted Cu deposits of the Domes region,

north-west Zambia. Located in the Mwombezhi Dome, a basement high, adjacent to the world-

class sediment-hosted Cu belts of the Democratic Republic of Congo (DRC) and Zambia, the

Domes region is now known as the “New Copperbelt” thanks to the development of several

large-scale mining projects. The generation of large amounts of drill core as well as freshly

exposed pit faces has enabled numerous advancements to be made on the understanding of the

structurally complex ore bodies. The presentation highlights how newly obtained

geochronological and lithogeochemical data, drill core observations and pit and outcrop mapping

have been used to generate a new model for the emplacement of the deposit. It is suggested that

shear zones in basement rocks which utilize a basal thrust along a slice of structurally emplaced

Lower Roan act as fluid conduits for Cu-rich brines. These shear zones metasomatise and

mineralise the reduced Palaeoproterozoic lithologies generating well foliated Cu-sulphide bearing

micaceous schists. Timing of mineralisation is still unclear however the Lufilian Orogen is

thought to be responsible for coarsening and locally remobilizing sulphides suggesting the

introduction of mineralizing brines pre- or syn-deformation.

1. As of December 31, 2013. For more information, see pages 29-30 of Barrick’s 2013 Form 40-

F/Annual Information Form, on file with the SEC and Canadian provincial securities regulators.

19

Structural and Mineralogical Characteristics of Nalunaq Gold Deposit, South

Greenland: Implications for Gold Location

Robin-Marie Bella, and Jochen Kolba

a Department of Petrology and Ore geology, Geological Survey of Denmark and Greenland, Denmark

rmb@geus.dk

Nalunaq is a Palaeoproterozic orogenic gold deposit located in South Greenland. The deposit is

situated in Nalunaq mountain on the Nanortalik Peninsula, opening as a mine in the early 2000’s

[1]. Nalunaq was Greenland’s only producing mine before ceasing operations in January 2014

having produced 10.5 t Au at an average grade of 14.2 g/t [2,3]. The deposit is characterised by

0.5-2 m wide gold-bearing quartz veins in altered meta-basalt and meta-dolerites. The gold-

quartz veins are orientated 35- 50˚ SE [4], have a pinch and swell form and commonly

incorporate host-rock xenoliths. A combination of thin section and microprobe analysis and 3D

computer modelling has constrained several factors which affect gold grade and distribution in

Nalunaq gold deposit. 3-D modelling of the deposit was undertaken using Leapfrog software.

Drillcore data and sample data from the interior of the mine was combined with geological and

structural data in order to construct the model.

A four stage alteration system has affected the deposit. Plagioclase-quartz alteration form

discontinuous 0.2-20 cm veins with a 0.1- 5.0 cm halo of garnet-diopside ± chalcopyrite ± pyrite

± sphalerite. The alteration distorts foliation within the host rock, suggesting that deformation of

the host rock and formation of the plagioclase-quartz alteration are simultaneous. This alteration

stage pre-dates gold mineralisation at Nalunaq. Gold-quartz veins are the only mineralised stage

in the Nalunaq deposit. Gold-quartz veins contain a c. 20 cm pyrrhotite –arsenopyrite –biotite ±

diopside banded alteration zone in areas of high gold grade.

A retrogressive zoisite muscovite ± pyrite ± haematite ± prehnite alteration overprints the garnet-

diopside-feldspar alteration and the gold-quartz veins. Sericite and clay-like (presumed kaolinite)

mineral alteration forms at the same time as zoisite alteration. An epidote-calcite alteration post-

dates all other alteration stages in Nalunaq gold deposit. Areas affected by epidote-calcite

alteration have a brittle fabric. The epidote-calcite alteration is concentrated in the peripheries of

Nalunaq gold deposit, and is associated with low gold grades and late-stage faults.

The 3D model has revealed a correlation between faulted areas and low gold grades, suggesting

that late-stage faulting has potentially offset gold-quartz veins in Nalunaq gold deposit and

reassessment of structural data may highlight prospective areas for exploration.

References

[1] D. M. Schlatter, and S. D. Olsen. “The Nalunaq gold deposit: a reference sample

collection and compilation and interpretation of geochemical data”, Danmarks og Grønlands

Geologiske Undersøgelse Rapport 2011/31, 2009.

[2] Angel Mining Plc, I. a. T. C., “Progress report to court pursuant to rule R2. 112 of the

insolvency rules 1986 and the insolvency (amendment) rules 2010 and progress report to

creditors pursuant to rule R2.47 of the insolvency rules 1986 and the insolvency rules 2010”,

2014.

[3] S. D. Olsen. Pers comms, 2014.

[4] K. Kaltoft. “Geology and genesis of Nalunaq Palaeoproterozoic shear zone-hosted gold

deposit, South Greenland”, Trans. Instn Min. Metall. (Sect. B: Appl. Earth sci.),, 109. B23-33.

January–April 2000.

20

Geochemistry and Origin of Manganese Nodules from the Western Pacific

Sebastian M Bettona, Andy Saundersa, Akuila Tawake, Christine Prasad, and Mike Pettersonb

a Department of Geology, University of Leicester, UK, sb546@le.ac.uk,

b Applied Geoscience and Technology Division of SOPAC, Fiji.

Manganese nodule samples from deep-sea (>4km) dredges in the exclusive economic zones

(EEZ) of the Cook Islands and Kiribati were supplied by the Applied Geoscience and Technology

Division of SOPAC, Fiji. The aim of the research is to categorise the nodules in terms of

composition, origin and mode of formation. It remains unclear whether the process is purely

orthochemical, or if part of the process is biologically mediated.

All of the studied nodules are spherical to sub-spherical in shape, with no clear anisotropy due to

long-term partial burial in sediment. We have studied the nodules via bulk analysis by XRF, and

direct analysis by LA-ICP-MS. Core to rim radial chemical profiles created by LA-ICP-MS show

unusual patterns for a variety of elements. Elements that have a steady supply to the nodule (e.g.,

Th, Zr, Co, Nb) show an increase in abundance from the nucleus to the rim. In their study,

Puteanus & Halbach (1988), estimated growth rates from the abundance of Co in Fe-Mn crust. A

faster growth rate correlated with a lower cobalt concentration. A major question then is whether

the changes in element abundance indicate that the growth rate is changing, as the nodule grows

larger, or that this is an artefact of internal post growth changes?

High-resolution reflected light and X-ray CT scanner images demonstrate the complex internal

structures within the nodules. An attempt will be made to see how these structures differ with

change in chemistry. New and existing bulk composition data will also be assessed, with the

objective of examining nodule-seawater interactions and potential chemical impacts of nodules

on seawater, or if their formation is simply a response to ocean composition.

Interest in manganese nodules as a potential metal resource has increased in recent times due to

new data on composition and abundance of nodules, with increased interest in the potential of

rare earth elements as a by-product of copper, nickel, cobalt and manganese [1]. With the

increased interest in mining, this study aims to achieve a better understanding of the processes

involved in the formation of manganese nodules.

References

[1] J. R. Hein et al. “Deep-ocean mineral deposits as a source of critical metals for high- and

green-technology applications: Comparison with land-based resources”, Ore Geology

Reviews, vol. 51. Pp. 1-14, 2012.

[2] D. Puteanus, and P. Halbach. “Correlation of Co concentration and growth rate – A

method for ages determination of ferromanganese crust”, Chemical Geology, vol. 69, pp. 73-

85, 1988.

21

Lithological and Microstructural Controls on Mineralisation at the Kibali

Gold Project, NE Democratic Republic of the Congo

Philip J Birda, Peter J Treloara, Carlos A Vargasb, and Joel Hollidayb

a Kingston University, Penrhyn Road, Kingston upon Thames, Surrey, KT1 2EE, pjbird@kingston.ac.uk,

b Randgold Resources Ltd, 3rd Floor, Unity Chambers, 28 Halkett Street, St Helier, Jersey, JE24W.

The Kibali gold project is a large orogenic type gold only deposit located in NE Democratic

Republic of Congo operated by Randgold Resources Ltd. The project is centered around the

Kagaraba-Chaffeur-Durba (KCD) deposit containing an inferred resource of 17Moz Au (Dec.

2013) with significant additional resource in an array of satellite deposits, the principle of which

are Pakaka (1.2.Moz) Mengu (0.7Moz), and Pamao (0.7Moz) ore bodies, bringing the total

resource to 22Moz.

Mineralisation at the KCD deposit occurs within a thrust package composed of altered

sedimentary conglomerates, carbonaceous shales and banded iron formations. The thrust stack is

developed along NW-SE orientated NE dipping thrust faults (S1) and is bounded by NE-SW

orientated east dipping shear structures (S2). Adjacent to fault structures the host conglomerate

has locally undergone ductile deformation, resulting in stretched quartz clasts and chlorite rich

intraclast shear structures. Deformation increases with proximity to the S1 and S2 structures,

reaching protomylonitic levels in the most intense examples. The host lithologies have been

extensively altered with the development of iron rich carbonates, principally ankerite and siderite,

and late aluminoceladonite mica. The degree to which the alteration phases are developed varies

with proximity to the S1 and S2 structures. Proximal to S2 structures ankerite-siderite alteration

reaches its greatest intensity, overprinting all original structures and mineral phases within the

host conglomerate. Moving progressively away from the S2 structures the alteration is less well

developed and confined principally to the intraclast shear zones overprinting chlorite, while the

stretched quartz clasts remain unaltered. Mineralisation is focused on the intersection of S1 thrust

planes and S2 shear structures with mineralisation style varying with both lithology and

proximity to the S1/S2 intersections. Adjacent to the intersection, aurifeous pyrite attains its

highest grade and is confined to brittle microveins. With increasing distance from the S1/S2

intersections grade drops and mineralisation occurs as disseminated sulphides confined to chlorite

rich intraclast shear structures.

In developing a synthesis we have had to account for the varying characteristics observed within

the deformation, alteration and mineralisation. Ductile deformation along the S1 and S2 structures

facilitated a strain softening process in which extensive growth and alignment of chlorite created

intraclast shear structures within the host conglomerate. This accommodated motion and

significantly increased porosity. Deep sourced metamorphic fluids ascended along the S2

structures and moved laterally along S1 structures where they intersected. Fluids infiltrated

stretched conglomerate material adjacent to the S1 and S2 structures through phyllosilicate rich

intraclast shears altering the chlorites Fe-carbonates. This process effectively ‘hardened’ the

intraclast structures prohibiting further deformation and fluid flow through the conglomerate.

Fluid over-pressuring in this hardened system resulted in brittle failure of the S2 structure and

conglomerate, creating brittle vein structures scavenging iron from the Fe-rich carbonate wall

rock to form sulphides and precipitate gold from solution. In distal areas, where alteration is less

developed a degree of porosity was retained allowing fluid flow through the intraclast shear

structures, sulphidising Fe-rich chlorites and precipitating gold.

22

Dating the Kibali Gold Project: Contrasting Zircon and Monazite Ages

Philip J Birda, Peter J Treloara, Nicholas Robertsb, Ian Millerb, and Joel Hollidayc

a Kingston University, Penrhyn Road, Kingston upon Thames, Surrey, KT1 2EE, pjbird@kingston.ac.uk

b NERC isotope geosciences laboratory, Keyworth, Nottinghamshire, NG12, 5GG, c Randgold Resources Ltd, 3rd Floor, Unity Chambers, 28 Halkett Street, St Helier, Jersey, JE24WJ.

The Kibali gold project is a 22 Moz gold only orogenic type deposit located in NE Democratic

Republic of the Congo. The gold resource is primarily hosted within the Karagba-Chaffeur-Durba

(KCD) deposit with additional resource contained within a series of 0.5-1 Moz satellite deposits

spread across the Kibali Granite-Greenstone belt (KGB). The KGB consists of thrust stacked

sediments and sub aerial basalts intruded by multiple igneous plutons. The belt is bounded to the

south by the Upper Zaire Granite massif (UZG) consisting of multiple generations of granitic to

gabbroic intrusions and to the north by the granitic West Nile Gneiss (WNG). Field observations

and geochemical analysis of the three major terranes show that intrusive rocks from the Kibali

belt and Upper Zaire Granite massif are geochemically similar; forming as part of an island arc

with associated back arc spreading. To correctly place Au mineralisation into the context of the

evolution of the Kibali Granite-Greenstone belt we have performed an extensive

geochronological study. This has employed U-Pb dating of magmatic zircon to temporally

constrain the evolution of the greenstone belt analysis of hydrothermal monazite to date the

formation of mineralisation.

LA-ICP-MS analysis was used to generate U:Pb ratios for igneous zircons and hydrothermal

monazites. Zircons were extracted from granodiorites, granites and granite-gneisses selected from

across the three major geological terranes, KGB, UZG and WNG with a total of 439 individual

analyses performed across ten samples. All zircons were imaged by cathode luminescence to

determine their internal textural characteristics. Hydrothermal monazites were analysed in-situ

with a total of 111 analysis across nine samples selected from KCD, Pakaka, and Pamao deposits.

Monazite occurs as 20-50 µm crystals and displays a strong textural association with auriferous

pyrite.

Analysis of intrusive units from the KGB yielded zircon crystallisation ages ranging from 2635-

2643Ma. A single sample of metamorphosed sedimentary material from the KGB yielded a

detrital age of 2673Ma. Analysis of granites and granodiorites from the UZG yielded

crystallisation ages ranging from 2629-2635Ma. Analysis of gneissic material yielded

metamorphic ages ranging from 983 to 1003Ma. All analysis yielded discordant lower intercepts

recording a region wide Pb loss event during the period 500-400Ma. Analysis of Monazites

yielded ages of 530±30Ma at KCD, 545±19Ma at Pakaka and 556±38Ma at Pamao. Zircon dates

combined with geochemical observations indicate that the Kibali Granite-Greenstone belt and

Upper Zaire Granitoid formed during an arc accretionary event at approximately 2.63Ga before

colliding with the West Nile Gneiss during a 500-400Mya window associated with a prolonged

Pan African orogeny and region wide thermal event. Monazite ages potentially place the

development of mineralisation during the early phases of this interpreted Pan African event along

the northern margin of the Congo Craton.

23

Recent Hydrothermal Base Metal Sulfide Mineralisation, Milos Island,

Greece: A ‘Modern’ Analogue Model for Shallow Marine Arc-Related

Deposits?

Martin Black, Catherine J Breislin, Eoin Dunlevy, Matthew R Grimshaw, Hannah SR Hughes, Emma J

Hunt, Bartosz T Karykowski, Dan Parkes, Simon Tapster, Christopher M Yeomans, Stephen Grebby, Luke

Bateson, Jon Nadena

a British Geological Survey, Keyworth, UK, j.naden@bgs.ac.uk

A NERC-funded Advanced Training Short Course on multidisciplinary field skills in a

professional geoscience environment was run by the British Geological Survey in autumn 2014.

In part, it was based around the theme of ‘Natural Resources’, and this aspect of the course

examined the relationship between volcanic, sedimentary and hydrothermal environments and

how these relate to mineralization potential on Milos island, Greece. This presentation outlines

the course outcomes of a specific part of the field investigation, which focused on the mineral

potential of the Triades–Galana area in the west of Milos. The island is a recent, well-preserved

emergent volcanic edifice (< 3 Ma) with associated active and palaeo-geothermal/hydrothermal

systems that act as analogues for ongoing submarine mineralization. These also provide an insight

into a range of volcanic massive sulfide (VMS) deposits in the geological record worldwide.

Initial field reconnaissance was undertaken using a geographical information system (GIS) and

high-resolution airborne remote sensing imagery in a 3D visualization suite (GeoVisionary). This

identified key areas for follow-up fieldwork, such as protruding silicified breccia bodies.

Additionally, clay and FeO alteration maps produced from Landsat imagery highlighted the

potential for field-based use of a Portable Infra-red Mineral Analyser (PIMA) spectrometer to test

vectors for mineralisation.

Field investigations comprised three parts: (1) a general geological overview and analysis of

unmineralised volcanic facies and lithologies, (2) a review of mineralisation on the island and (3)

targeted mapping of a selected mineralized region (Triades-Galana). Mapping of Triades–Galana

located multiple breccia bodies spatially related to a NW-trending fault zone and associated fault

splays. Breccia bodies form prominent topographic features (10–50 m wide) composed of barite

blocks, multiple vein generations, silicified zones and local sulfides. Zones of white clay

alteration were noted surrounding the breccia bodies over variable distances. Spectral reflectance

data were acquired through breccia bodies using PIMA and allowed for broad scale mapping of

clay alteration zones through the analysis of absorption features in the short-wave infrared

(SWIR; 1.3 to 2.5 µm). Mineralogical interpretations based on obtained spectra were compared to

reference spectral libraries and identified mineral assemblages (kaolinite, muscovite,

montmorillionite) indicating argillic alteration resulting from geothermal fluids proximal to the

breccia bodies.

Field-based observations and analyses were combined into a deposit model for this region. Key

components of the model are: (1) sub-seafloor magmatic activity led to the formation of local

dacitic domes and acted as a heat source driving magmatic-hydrothermal and hydrothermal fluid

circulation. (2) Convection of seawater through synvolcanic faults and fractures leached metals

from the basement, and became re-precipitated as near-seafloor vein-hosted sulfates and sulfides.

(3) Fluid boiling temperatures constrain Triades–Galana to representing a shallow marine

environment. Boiling initiated hydrofracturing and formed Zn–Pb–(Cu–Ag) mineralisation in the

breccia bodies.

‘Exportable’ characteristics defined by our Milos model of a shallow-marine arc-related VMS

deposit should adhere to the presence of crustal lineaments (as fluid pathways), water depth

(dictating boiling depth and metallic composition), and volcanic facies (as permeability ‘trap’

features).

24

What Have Stable Isotopes Ever Done for My Ore Deposit?

Adrian J Boyce

Scottish Universities Environmental Research Centre, Glasgow, Scotland, UK

Discovery of ore deposits relies increasingly on improved conceptual models, as targets become

deeper and generally less concentrated than those discovered to date. The treasure hunters thus

need to take information in from as many sources as possible to enhance discovery rates. Stable

isotope analyses can be one very important string to the hunters bow, as it focusses on elements

of direct consequence to the deposition of ore minerals – S, O, H and C. I will prioritise examples

in which isotopic analyses have been useful in shedding light on genetic models for ore deposits,

and/or which have provided a direct exploration tool for the explorationist. There is no doubt also

that stable isotopes can be mis-used; some cautionary notes will be provided.

Basic concepts in stable isotope geochemistry will be explored for their utility to the

explorationist. For example, the potential of O isotope measurements in silicate and carbonate

minerals to (i) provide direct tests of ore genetic models; (ii) provide potential tools for deposit

targetting (and the pitfalls therein!). For S isotopes, I will focus on base-metal deposits, with

examples showing the power of S isotopes to (i) demand a paradigm shift in ore genetic models;

(ii) shed light on the mass balance and dynamism of sulfide ore systems.

The examples come from PhD students who have worked with the Isotope Community Support

Facility at SUERC over the past few years. A signature of all of these successful examples, is that

they are based on high quality geological and mineralogical observations. In contrast, there are

examples in the literature where stable isotope analyses have been less effective because of a lack

of in-depth understanding of the precise relationship of the analysed sample to the geological

evolution of a particular deposit.

A brief future look will discuss (i) the potential of clumped carbonate isotope analyses, which

will be available in ICSF during 2015, and (ii) automated EA-IRMS (elemental analyser isotope

ratio mass spectrometry) S isotope systems for regional surface sample surveys.

Advert for Success (references)

[1] C. D. Barrie et al. “On the growth of colloform textures: A case study of sphalerite from

the Galmoy ore body, Ireland”, Journal of the Geological Society of London, vol. 166, pp.

563-582, 2009.

[2] A. E. Fallick et al. “Bacteria were responsible for the magnitude of the world-class

hydrothermal base-metal orebody at Navan, Ireland”, Economic Geology, vol. 96, pp. 883-

888, 2001.

[3] N. J. Hill et al. “How Neoproterozoic S-isotope record illuminates the genesis of vein

gold systems: an example from the Dalradian Supergroup in Scotland”, Geological Society,

London, Special Publications, vol. 393, pp. 213-247, 2015. (See book on display at the meeting)

[4] D. A. Holwell et al. “Sulfur isotope variations within the Platreef Ni-Cu-PGE deposit:

Genetic implications for the origin of sulfide mineralization”, Economic Geology, vol. 102,

pp. 1091-1110, 2007.

[5] R. McGowan et al. “Origin of the Nchanga copper–cobalt deposits of the Zambian

Copperbelt”, Mineralium Deposita, vol. 40, pp. 617-638, 2006.

25

Regional Prospecting: Can We Couple Large-Scale Exploration Data with

Novel Geochemical Discrimination?

Linda S Campbella, John Charnocka, and Alan Dyerb

a School of Earth, Atmospheric and Environmental Sciences, University of Manchester, U.K,

Linda.Campbell@manchester.ac.uk, b Department of Chemistry, Loughborough University, U.K.

Ores associated with alkaline and carbonatite systems include an array of metals at risk of

supply criticality, such as Nb and the rare earth elements (REE) [1]. Regions that fulfill

established criteria for carbonatite prospecting (e.g. cratons and craton margins,

continental rifts, buried rifts [2]), have potential for added value from exploration drill-

core samples. To demonstrate this, new geochemical data are presented from alkaline

hydrothermal assemblages in surface exposure that contain hydrated Al-silicates ±

calcite/carbonates [3], supported by a novel conceptual model [4,5]. The data from four

continents represent the earliest contributions to a potential global reference framework,

supporting exploration with fundamental understandings of “mineral-rock-fluid-time”

compositional relationships in these systems [6].

Further developments of a prospecting tool require coupling of these mineral

compositions to whole-system geological data and expertise, ideally to be tested and

refined with samples associated with known, relevant mineral deposits. Diverse types of

geological data (field maps, geophysical data, satellite spectral imagery, drill core

mineralogy) with team-expertise are effectively only accessible through the existing

activities of mineral exploration companies. Therefore, opportunity for further

discussion/engagement shall be outlined.

Acknowledgements: Prof. D. Polya (Univ. Manchester), NERC grants NE L002418/1, IAA002,

and the Mineral Industry Research Organisation.

References

[1] British Geological Survey’s “Critical Metals Handbook”, Wiley, pp. 454, 2014.

[2] A. R. Woolley and B. A. Kjarsgaard. “Carbonatite Occurrences of the World: Map and

Database”, Geological Survey of Canada, Open File 5796, 1 CDROM + 1 map, 2008.

[3] L. S. Campbell et al. “Applications of zeolite science to problems in rare earth element

research (Invited Lecture)”, In Zeolite 2014. The 9th International Conference on the

Occurrence, Properties, and Utilization of Natural Zeolites (Eds. Daković, A., Trgo, M. and

Langella, A.), Belgrade, Serbia, pp. 9-10, 2014.

[4] L. S. Campbell et al. “The masquerade of alkaline-carbonatitic tuffs by zeolites: A new

global pathfinder hypothesis”, Mineralium Deposita, vol. 47, pp. 371-382, 2012.

[5] M. Tyrer and L. S. Campbell. “Zeolitic Pathfinders”, MIRO News, vol. 26, pp. 8-9, 2012.

[6] REAMS project website: https://connect.innovateuk.org/web/ree-in-alkaline-mineral-

systems.

26

Hydrothermal HREE Enrichment in the Huanglongpu Deposit, China

Delia Cangelosia, Martin Smithb, Bruce Yardleya, and Dave Banksa

a School of Earth and Environment, University of Leeds, United Kingdom, ee12dac@leeds.ac.uk,

b School of Environment and Technology, University of Brighton, United Kingdom.

The Huanglongpu deposit is situated at the north of the north-western part of the Qinling orogenic

belt. The uncommon Mo and HREE enrichment of the Huanglongpu carbonatites have been

interpreted as a primary feature of metasomatized mantle-derived igneous rocks [1]. The aim of

this study is to understand what may have led to Mid to HREE enrichment at specific sites in the

deposit, by studying the chemistry of fluid inclusions from a quartz vein associated with REE

mineralization (allanite, xenotime and REE-carbonate).

Fluid inclusions hosted in the vein quartz can be divided in four types, described here from the

earliest to the latest fluid stage: one-phase CO2-rich inclusions (Type 1B) Tmcla around 2.5°C,

three-phase CO2-rich, solid-bearing inclusions (Type 1A2), two-phase CO2-rich inclusions (Type

1A1) with Tmcla from 1 to 7°C and liquid-vapor inclusions (Type 2). Most of the inclusions have

Tmice between -7 and -11°C. Only Type 2 inclusions have measureable ThTOT, and these yield a

minimum temperature of trapping between 140°C to 230°C. The solids in Type 1A2 inclusions

have been identified by Raman spectroscopy, and are mainly sulphates with some calcite. In Type

1A inclusions, concentration of sulphate is up to 16 molal which correspond to an inclusion with

30% solid sulphates. SEM analysis of opened fluid inclusions without daughter minerals shows

those inclusions are Cl-rich. Raman spectroscopy has revealed a significant amount of sulphate in

solution in Type 1A inclusions meaning another ligand is available in the hydrothermal fluid in

addition to chloride. LA-ICP-MS analysis shows that the cation load of CO2-rich inclusions

(Type 1) is dominated by Na, K, and Ca, and contain Mg > Fe. In Type 1A inclusions, there is a

significant amount of LREEs (La, Ce and Pr) and HREE > 1ppm; in contrast Type 1B inclusions

only contain significant amounts of the LREEs (La and Ce) (Figure 1).

Chloride and sulphate ligands are believed to be the main transporting agents for REE in

hydrothermal fluids; however the highest HREE levels found in this study are in sulphate-rich,

CO2-bearing fluids, suggesting that these ligands, rather than Cl, were responsible for

hydrothermal HREE enrichment in the quartz vein studied.

Type 1A

X/N

a

1e-6

1e-5

1e-4

1e-3

1e-2

1e-1

1e+0

1e+1

K La Ce Eu Gd Dy Y

Type 1B

X/N

a

1e-6

1e-5

1e-4

1e-3

1e-2

1e-1

1e+0

1e+1

K La Ce Eu Gd Dy Y

Figure 1: Element weight ratios of K, La, Eu, Gd, Dy, Y relative to Na in Type 1A (left) and

Type 1B (right) fluids.

Reference

[1] C. Xu et al. “A unique Mo deposit associated with carbonatites in the Qinling orogenic

belt, central China”, Lithos, vol. 118, pp. 50-60, 2010.

27

The New South West Extension-South (SWEXS) Mineralisation of the Giant

Navan Carbonate-Hosted Zn-Pb Deposit: Testing the Sub-Sea Floor

Replacement Paradigm

Olivia Chant-Tufta, Jamie Wilkinsona,b, Robert Blakemanc, and John Ashtonc

a Department of Earth Science and Engineering, Royal School of Mines, Imperial College London, UK,

olivia.chant-tuft11@imperial.ac.uk, b Department of Earth Sciences, Natural History Museum, London, UK c Boliden Tara Mines Limited, Navan, County Meath, Republic of Ireland.

The Navan orebody, located in the Irish Orefield, is a world-class carbonate-hosted lead

zinc deposit exceeding > 110 million metric tonnes of ore. At Navan (and north-central

Ireland in general), mineralisation is hosted within the Navan Group, which comprises

shallow marine carbonates of Lower Carboniferous age. Two broad models have been

proposed for ore genesis and the timing and depth of mineralisation at Navan: an

epigenetic model whereby mineralisation occurred at significant depth, well after

lithification of the host rocks; and a syn-diagenetic model in which mineralisation formed

near the seafloor during diagenesis of the host rocks.

Exploration in the 1990’s led to the discovery of significant extensions to the original ore

body, in an area now termed the South Western Extension (SWEX). Recently, significant

mineralisation has been intersected to the south-east of the SWEX, in the SWEX-south

zone (SWEX-S). It is unclear so far if this zone represents a continuation of the same

hydrothermal system which formed the ore bodies of the main deposit or is a separate

satellite.

In this study, petrographic analysis has been used alongside fluid inclusion

microthermometry to assess the connection between the SWEX-S mineralisation and the

main deposit, and to test the hypothesis that mineralisation formed by shallow sub-

seafloor replacement.

Preliminary petrographic results show similarities in mineralisation styles and textures to

the main deposit and a comparable carbonate and sulphide paragenetic sequence. Fluid

inclusion data show a spread in salinity values and homogenisation temperatures, with a

weak negative trend between a higher temperature, low salinity fluid and a lower

temperature brine. This suggests sulphide precipitation occurred as a result of fluid

mixing that is consistent with results from the main orebody. There is also evidence that

boiling possibly occurred.

Further work is being carried out to constrain the depth of mineralisation and confirm the

presence of boiling fluids at the time of mineralisation which would support a shallow,

syn-diagenetic model for ore genesis.

28

Reassessment of Pb Isotope Geochemistry on the Pb-Zn Deposits in Northern

Baltica: Hydrocarbon Source Rocks also Contribute to the Metal

Endowment

Cyril Chelle-Michoua, Nicolas J Saintilana, Massimo Chiaradiaa, Jorge E Spangenbergb, Michael B

Stephensc,d, and Lluís Fontbotéa

a Section of Earth and Environmental Sciences, University of Geneva, Switzerland, cyril.chelle-

michou@unige.ch, b Institute of Earth Surface Dynamics, University of Lausanne, Switzerland, c Geological Survey of Sweden, Sweden, d Division of Geosciences, Luleå University of Technology,

Sweden.

Extensive lead isotope studies of Mississippi Valley-type (MVT) Pb-Zn deposits have shown that

metals in these deposits are essentially leached from regional basement rocks or basal detrital

rocks by circulating basinal brines [e.g., 1]. In northern Baltica, Pb isotopic data from the 80’s

and 90’s similarly suggested that metals from a variety Pb-Zn deposits across Baltica were

leached from the local Palaeoproterozoic metamorphic basement [2, 3, 4]. Taking advantage of

the considerable advances in the field of Pb isotopic analysis, we propose a reassessment of the

source(s) of metals in these deposits.

We present new high precision Pb isotopic data from ores samples from the world-class

sandstone-hosted Middle Ordovician Pb-Zn deposit at Laisvall, and from the late Ediacaran

Åkerlandet and Storuman Pb-Zn vein districts in Palaeoproterozoic basement. Leachate and

residue fractions of potential metal source rocks such as the Palaeoproterozoic crystalline

basement and upper Cambrian‒Lower Ordovician organic-rich black shale (the Alum shales)

were also analyzed. The data shows that the source of metals in the Laisvall deposit appears to be

different than that in the vein deposits. Indeed, source model age for ore Pb of the vein deposits is

consistent with derivation from leaching of the Palaeoproterozoic basement, as expected.

However, ore Pb at Laisvall appears to result from mixing between a major component derived

by leaching of Palaeoproterozoic basement rocks and a minor component derived from the upper

Cambrian‒Lower Ordovician organic-rich sedimentary Alum Shale.

These findings suggest that hydrocarbon source rocks may contribute to the metal endowment of

some world-class MVT deposits. Processes of metal extraction and transport from such organic-

rich rocks are discussed in a companion presentation (Saintilan et al., this conference).

References

[1] R. R. Large et al. “Stratiform and strata-bound Zn-Pb-Ag deposits in Proterozoic

sedimentary basins, northern Australia”, Economic Geology 100th Anniversary Volume, pp.

931-963, 2005.

[2] R. L. Romer. “Sandstone-hosted lead-zinc mineral deposits and their relation to the

tectonic mobilization of the baltic shield during the Caledonian orogeny? a

reinterpretation”, Mineralogy and Petrology, vol. 47, pp. 67-85, 1992.

[3] M.J. Duane, and M.J. de Wit. "Pb-Zn ore deposits of the northern Caledonides:

Products of continental-scale fluid mixing and tectonic expulsion during continental

collision", Geology, vol. 16, pp. 999-1002, 1988.

[4] Å. Johansson, and D. Rickard. "Isotopic composition of phanerozoic ore leads from the

Swedish segment of the Fennoscandian Shield", Mineralium Deposita, vol. 19, pp. 249-255,

1984.

29

On the Role of Petrological Cannibalism in the Genesis of the Coroccohuayco

Porphyry-Skarn Deposit, Peru

Cyril Chelle-Michoua, and Massimo Chiaradiaa

a Section of Earth and Environmental Sciences, University of Geneva, Switzerland

cyril.chelle-michou@unige.ch

Recycling of previously emplaced plutons or crystal mush in the upper crust is a common process

in arc-related magmatic systems. In the case where the recycled material hosts abundant

sulphides, this petrological cannibalism might be a key process that can significantly contribute to

the metal endowment of porphyry copper deposits [e.g. 1]. However, the common association of

porphyry deposits with high Sr/Y rocks suggests that the fertility of the magmatic system is

mostly acquired in the deep crust [e.g. 2]. This suggests that recycling of deep crustal magmatic

rocks may be a first order control on the genesis of porphyry deposits [3].

The magmatic suite associated with the Eocene Coroccohuayco porphyry-skarn deposit (southern

Peru) retains evidence of petrological cannibalism: (1) zircon antecrysts, xenocrysts and Hf

isotopes together with Sr-Nd isotopes suggest that upper crustal and proto-pluton assimilation

was maximal at the time of porphyry emplacement; (2) high-Al amphiboles as well as texture and

S-zoning of apatite argue in favour of recycling of a S-rich, water-rich and oxidised lower crustal

magmatic system.

We propose that lower crustal magmatic processes controlled the fertility of magma in terms of

metals, ƒO2, and volatile content (H2O, S). Additionally, sustained magma injections in the upper

crust during ca. 2 Ma before the emplacement of the porphyries and the genesis of the deposit

created a large and stable thermal anomaly that may have favoured efficient fluid and metal

extraction from the cooling upper crustal magma chamber [e.g. 4, 5].

References

[1] J. J. Wilkinson. “Triggers for the formation of porphyry ore deposits in magmatic arcs”,

Nature Geoscience, vol. 6, pp. 917-925, 2013.

[2] J. P. Richards, and R. Kerrich. “Special paper: Adakite-like rocks: their diverse origins

and questionable role in metallogenesis”, Economic Geology, vol. 102, pp. 537-576, 2007.

[3] M. Chiaradia. “Copper enrichment in arc magmas controlled by overriding plate

thickness”, Nature Geoscience, vol. 7, pp. 43-46, 2014.

[4] J. L. Vigneresse. “The role of discontinuous magma inputs in felsic magma and ore

generation”, Ore Geology Reviews, vol. 30, pp. 181-216, 2007.

[5] W. J. A. Stavast et al. “The fate of magmatic sulfides during intrusion or eruption,

Bingham and Tintic districts, Utah”, Economic Geology, vol. 101, pp. 329-345, 2006.

30

Geochemical and Mineralogical Styles of the Low Sulphidation, Epithermal

Au-Ag Deposits of Sahinli, Western Turkey

Jake N Clarka, David A Holwella, Richard J Siddleb, and Tuna Kaskatic

a University of Leicester, Leicester, UK, jnc10@le.ac.uk, b MICROMINE, London, UK, c Eczacıbaşı Esan,

Istanbul, Turkey.

Sahinli, and other epithermal and porphyry systems within the Biga Peninsula district of Turkey,

lie with the Tethyan Eurasian Metallogenic belt. Turkey represents a relatively underexplored

region within this highly prosperous belt although exploration activity has increased significantly

over the past decade. The Sahinli epithermal gold and silver deposit is located 40 km to the

northeast of Çanakkale. The 35 km2 tenement is held by Esan Eczacıbaşı as part of their Mineral

Production License.

The propsects at Sahinli are considered to be of a low sulphidation epithermal gold classification

due to the presence of neutral clays, analogous to deposits in the Nansatsu District of Japan [1],

and low temperature textural relations, observed in outcropping veins and in drill core. Sahinli is

divided into three exploration target areas based on varying wall rock alterations, structural

controls and mineralisation styles; Kovanilik, Karatepe and Sirakayalar. Mineralised and barren

veins trend in various directions, but are predominantly NE-SW and range in width from 10 cm

up to 10 m and dip steeply to the SE and S. Across the three prospects, host rocks comprise

highly deformed Palaeozoic biotite-muscovite schist, exhibiting strong silicification and argillic

alteration styles; and andesite-dacite intrusions.

Soil geochemistry shows distinct geochemical signatures across different lithologies such as

micaceous schist wall rock showing high Li and Bi anomalies, contrasting with andesite-dacite

intrusions which coincide with high Rb, K and U anomalies in the soil. In addition, subsurface

vein structures can be traced using variations in Sb, As and Th anomalies. Preliminary

exploration drilling of NW-SE trending structures has proved that these high As, Sb and Th

anomalies in soils correlate with mineralised veins at depth. Thus, the soil geochemistry is a

reliable indicator of both mineralised structure and also host rock lithology in a region of poor

surface exposure.

Mineralogical analysis show that Au and Ag mineralisation is dominated by electrum. Metal

sulphides such as uytenbogaardite (Ag3AuS2) and acanthite (Ag2S) are common alongside

selenides, tellurides, arsenides, antimonides and bismuthides. In addition, sulfosalts with Sb, As,

Bi, including the sulfoselenide Petrovskaite (AuAg(S,Se)) have also been recorded. Minor base

metal minerals have also been found and mineralogical variations within the prospect areas are

likely to represent variations in P-T-X conditions during emplacement.

References

[1] J. W. Hedenquist et al. “Geology, geochemistry, and origin of high sulfidation Cu-Au

mineralization in the Nansatsu District, Japan”, Economic Geology, vol. 89, pp. 1-30, 1994.

[2] O. Yigit. “Gold in Turkey—a missing link in Tethyan metallogeny”, Ore Geology

Reviews, vol. 28, pp. 147-179, 2006.

31

Host Rock Characteristics and Controls on Cu-Au-Ag Mineralization at

Copper Mountain Porphyry Deposit, Southern BC, Canada

Edward Cromwella, Farhad Bouzarib, David Selbya, Craig JR Hartb, Peter Holbekc, and Richard Joyesc

a Department of Earth Sciences, University of Durham, UK, edward.cromwell@durham.ac.uk, b Mineral

Deposit Research Unit, Department of Earth, Ocean & Atmospheric Sciences, The University of British

Columbia, Canada, c Copper Mountain Mining Corp., Canada.

The Copper Mountain porphyry Cu-(Au-Ag) deposit has a current resource of 282Mt grading

0.33% Cu, an additional inferred resource of 299Mt at 0.28% Cu, with past production of ~200Mt

at an average grade of 0.53% Cu [1]. Given the loss of mineralization through glacial and fluvial

erosion the Copper Mountain mineralizing system may have originally been >1,000Mt. The

deposit is temporally and spatially associated with Late Triassic-Early Jurassic alkalic intrusions

emplaced into basaltic-andesitic, largely fragmental and brecciated volcanic rocks (Nicola

Group). Intrusive rocks include the zoned syenite to diorite Copper Mountain Stock (CMS), and

the largely diorite to monzonite Lost Horse Intrusive Complex (LHIC); which displays a

predominant dike and plug geometry. Post-ore units comprise Cretaceous felsite dykes and

Tertiary volcanic rocks and sediments of the Princeton Group.

Copper-(Au-Ag) mineralization is predominantly associated multiple intrusive units of the LHIC,

emplaced at different depths, which vary from small fingers of <1m to larger intrusions up to 30m

thick. Detailed core logging along two NE-trending cross-sections across the super-pit, in concert

with field and petrographic observations, define at least 3 phases of the LHIC: LH1g is

characterized by a fine-grained feldspar groundmass (<20 µm), low abundance of augite (10-

20%) and the presence of accessory apatite and titanite, LH1b has larger feldspar phenocrysts (up

to 300µm); LH2 is a later phase with an equigranular texture, increased augite (20-30%),

relatively little apatite and no titanite. The CMS intrusive unit is a monophase intrusion,

containing approximately 75% equigranular feldspars (100-300µm), 10% augite (100-200 µm),

minor biotite and fine-grained disseminated magnetite (∽50µm). Mineralization consists of vein-

stockworks and disseminated sulphides, with lesser matrix filling within hydrothermal breccias.

Sulphides include: chalcopyrite, bornite and hypogene chalcocite with pyrite and magnetite

gangue. Molybdenite occurs within veins as massive fine-grained (0.1 to 1mm) fracture coatings

and as disseminations with pyrite and minor chalcopyrite. Preliminary results indicate 78-600

ppm Re in molybdenite, and thus is highly suitable for Re-Os geochronology. Mineralization is

associated with potassic, K-feldspar – biotite, and sodic, largely albite, alteration. Both potassic

and sodic alteration range from veins to large zones of intense pervasive replacement. Potassic

alteration typically overprints sodic alteration and has a closer temporal and spatial relationship to

ore [2,3].

These new data provide a better understanding of the intrusive evolution and associated

mineralization at Copper Mountain and will provide a framework for magmatic complexity of

similar known porphyry camps in British Columbia, Canada.

References

[1] P. Holbek, and R. Joyes. “NI 43-101 Technical Report on Resources and Reserves,

Copper Mountain Mine, BC”, 2014.

[2] C. R. Stanley et al. “Geology of the Copper Mountain alkalic copper-gold porphyry

deposits, Princeton, British Columbia”, In Porphyry deposits of the Northwestern

Cordillera of North America (Ed. T. Schroeter), Canadian Institute of Mining and

Metallurgy, Special volume 46, pp. 537-564, 1995.

[3] P. Holbek, and R. Joyes. “Copper Mountain: An Alkalic Porphyry Copper-Gold-Silver

Deposit in the Southern Quesnel terrane, British Columbia”, Society of Economic Geologists

Field Trip Guidebook, Series 43, pp. 129-143, 2013.

32

The Key to Understanding Antimony Mineralisation in South West England

— the North Herodsfoot Mine?

Éimear Deadya and Kathryn Mooreb

a British Geological Survey, Environmental Science Centre, UK, eimear@bgs.ac.uk,

b Critical Metals Alliance, Camborne School of Mines, University of Exeter, UK.

The BGS risk list [1] identifies antimony (Sb) as having a high risk of supply shortage and it is

also identified by the EU criticality study [2]. It is used primarily in the production of flame

retardant materials and in lead-acid batteries [3]. Security of supply concerns result from 87% of

global production being in China, and a large market balance deficit predicted from 2015–2020 [2

and references therein]. Improved understanding of the genesis and distribution of antimony

mineralisation is key to developing exploration strategies and understanding the resource

potential of the UK, which could ultimately lead to diversification of production.

North Herodsfoot Pb-Ag-Zn-Cu mine was worked intermittently from the early 1700s, with

13 470 tonnes of Pb and 616 590 ounces of Ag produced [4]. Mineralisation occurs in north-

south-trending vein deposits of Mid-Triassic age, known as “crosscourse” type deposits.

Mineralisation results from the remobilisation of metals from nearby volcanogenic sedimentary

reservoirs which were transported by basinal derived fluids along pre-existing north-south-

trending structures [5]. Antimony is associated with the base metal mineralisation, predominantly

occurring in bournonite (PbCuSbS3), although at least four other Sb-bearing minerals have been

identified [4]. Antimony and base metal associations are also observed in “crosscourse”

mineralisation in the Wadebridge District [6].

New samples from the mine waste tailings at North Herodsfoot have been used to study the multi-

phase polymetallic mineralisation. The paragenesis includes galena, (± argentiferous galena),

bournonite, pyrite, arsenopyrite, chalcopyrite ± sphalerite ± pyrostilpnite-pyragarite (Ag3SbS3). A

preliminary paragenetic model of the deposit incorporates previously unidentified Ni-bearing

phases (gersdorffite (NiAsS)), which are associated with pyrite. This in new data in conjunction

with comparative studies with antimony mineralisation in the Wadebridge district and the

Menheniot area will be used to present a new model for antimony mineralisation in South West

England.

References

[1] BGS Risk List, 2012.

[2] European Commission, “Report on critical raw materials for the EU. Report of the Ad

hoc Working Group on defining critical raw materials”, May 2014.

[3] Roskill, “Antimony: Global Industry Markets and Outlooks” 11th Edition, 2012. Roskill

Information Services, 2012.

[4] R. E. Starkey. “The Herodsfoot Mine, Lanreath, Cornwall, England”, The Mineralogical

Record, vol. 43, no. 4, pp. 411-486, 2012.

[5] R. C. Scrivener et al. “Timing and significance of crosscourse mineralization in SW

England”, Journal of the Geological Society, vol. 151, pp. 587-590, 1994.

[6] R. C. Clayton et al. “Mineralogical and preliminary fluid inclusion studies of lead

antimony mineralisation in north Cornwall”, Proceedings of the Ussher Society, vol. 7, part

3, pp. 258-262, 1990.

33

Valorisation of Waste Material - Rare Earth Elements in Red Muds: The

Potential of European Resources

Éimear Deadya, Evangelos Mouchosb, Kathryn Goodenoughc, Frances Wallb, and Ben Williamsonb

a British Geological Survey, Environmental Science Centre, UK, eimear@bgs.ac.uk, b Camborne School of

Mines, University of Exeter, UK, c British Geological Survey, Murchiston House, UK.

Bauxites, mined in large quantities as the main ore of aluminium, contain small amounts of rare

earth elements (REE). Red muds are generated as a waste product from the processing of bauxite

to alumina through the Bayer process. Although multiple types of bauxite exist, those of key

importance for REE resources are the ‘karst’ type. These form as a result of the accumulation of

residual clay minerals in depressions on a karst limestone surface, and their subsequent lateritic

weathering [1]. Karst-bauxites are widely distributed, and a number of deposits around the

Mediterranean have been intermittently exploited over many decades. REE are concentrated in

the bauxite deposits during the process of bauxitisation, and are typically deposited near the base

due to a geochemical barrier created by the limestone bedrock below. Deposition of the REE may

occur through the crystallisation of authigenic REE-bearing minerals, the accumulation of

residual phases, and/or the adsorption of ions on clays and other mineral surfaces [2]. Red mud

waste produced from alumina processing can contain enhanced levels of REE, as it has been

shown that all of the REE pass through the alumina extraction process into the waste, and the

total REE values are enriched by a factor of two from the original bauxite ore [3]. However, the

most efficient way to remove REE is on the first pass through the processing plant rather than

subsequent remining of the red mud waste.

Bauxites and the corresponding red muds from the Parnassus Ghiona region of Greece [4] and the

Seydişehir region of Turkey have been assessed as part of this preliminary study. Red muds from

Greece contain on average 900 ppm REE+Y compared with typical values of >150 ppm to <700

ppm REE+Y in the bauxites. Extraction of REE from red muds has been shown to be feasible [3,

5] although it is challenging due to the heterogeneous spatial distribution of REE in the bauxites

[6] and the need for development of appropriate processing methods. The resource potential of

red muds in Europe is significant with approximately 3.5 Mt of bauxite ore extracted in 2012 [7],

resulting in approximately 1.4 Mt of red mud from the production of alumina. Understanding the

REE potential of both bauxites and red muds is integral to an assessment of European REE

resources, such as that currently being developed by the EURARE project.

References

[1] G. Bárdossy. “Karst Bauxites, Bauxite Deposits on Carbonate Rocks”, Elsevier, pp. 444,

1982.

[2] Z. Maksimović, and G. Pantó, “Authigenic rare earth minerals in karst-bauxites and

karstic nickel deposits”, In Rare Earth Minerals: Chemistry origin and ore deposits (Eds A.

P. Jones, F. Wall, and C. T. Williams), Chapter 10, pp. 257-279, 1996.

[3] M. Ochsenkühn-Petropoulou et al. “Direct determination of lanthanides, yttium and

scandium in bauxites and red mud from alumina production”, Analytica Chimica Acta, vol.

296, no. 3, pp. 305-313, 1994.

[4] É. Deady et al. “Rare Earth Elements in Karst-Bauxites: a Novel Untapped European

Resource?” ERES Conference, Milos, Greece, 2014.

[5] A. Wagh and W. Pinnock. “Occurrence of scandium and rare earth elements in

Jamaican bauxite waste”, Economic Geology, vol. 82, no. 3, pp. 757-761, 1987.

[6] G. Mongelli. “Ce-anomalies in the textural components of Upper Cretaceous karst

bauxites from the Apulian carbonate platform (southern Italy)”, Chemical Geology, vol.

140, no. 1, pp. 69-79, 1997.

[7] T. Brown et al. “World Mineral Production 2008-12”, British Geological Survey, 2014.

Additional resources: www.eurare.eu; www.redmud.org.

34

The North Pennines Orefield - Investigating Early Permian Mineralization

and Transtension using Rhenium/Osmium Isotope Geochemistry

Edward D Dempseya, David Selbya, Robert E Holdswortha, Chris LeCornua, Brian Younga

a Dept of Earth Sciences, Durham University, e.d.dempsey@durham.ac.uk.

The North Pennines Orefield (NPO) is centred on the Alston block, a positive structural feature

overlying the Devonian age (ca. 398 Ma) Weardale granite batholith of Northern England. The

ore field has previously been regarded as an excellent example of a Mississippi Valley Type

(MVT) deposit, i.e., the source of the metals and sulphur are derived by hydrothermal leaching of

the host Carboniferous sedimentary (carbonate-rich) rocks. The vein hosted part of the orefield

consists of linked systems of shear, tensile and hybrid fractures in three regionally pervasive

orientations (ESE-WNW Quarter Point, NE-SW, NW-SE Cross Veins). These vein sets

associated with lead (galena), iron (pyrite, pyrrhotite, marcasite), copper (chalcopyrite), zinc

(sphalerite), fluorite, barite and quartz mineralization.

New field observations and stress inversion analyses show that at least two regional deformation

events are consistent with structures observed within in the Carboniferous host rocks of the NPO.

A phase of Late Carboniferous (‘Variscan’) N-S compression culminated in the formation of the

NW-SE fractures, initiation of the Burtreeford Disturbance and compressional reactivation of the

Lunedale Fault. A subsequent phase of NNE-SSW dextral transtension involves the formation of

the ESE-WNW and NE-SW veins, together with compressional reactivation of the Burtreeford

Disturbance and extensional reactivation of the Lunedale Fault. These tectonic events occurred in

conjunction with widespread NW European magmatism which is represented in NE England as

the 297.4Ma Whin Sill complex. With the exception of fluorite and barite which lie in

geographically distinct zones within the NPO, field and microstructural analyses show that the

vein-hosted minerals are all texturally coeval and syn-tectonic relative the later phase of

transtensional deformation.

Rhenium-Osmium isotope geochemical analysis of pyrite mineralization suggests that: (i) the

metalliferous ores of the NPO formed ca 294Ma (earliest Permian); and (ii) that they carry an

initial Os ratio indicative of a mantle source similar to that for the Whin Sill.

We conclude that (i) the main phase of NPO mineralization occurred synchronously with regional

dextral transtension during the earliest Permian; (ii) that mineralization is genetically linked to a

mantle source and (iii) that the genesis of the NPO has a strong genetic link to the

penecontemporaneous Whin Sill Complex. Our new findings are consistent with the structural

histories recognised in adjacent regions (e.g. Dent-Pennine Fault systems; Northumberland Basin)

and point to a major regional phase of mantle-sourced mineralization, magmatism and

transtensional deformation in the early Permian. Traditionally relative ages of different

deformation events have been established using cross-cutting field relationships and thin section

observation. This traditional approach places significant emphasis on the deformation sequence,

while the actual ages of these events remain elusive. Through this study of the NPO we show that

it is not only is it possible to date mineralization but indeed to date actual fault rocks themselves

putting real constraints on the timing of a brittle deformation events.

35

Clumped Isotope Constraints on Water:Rock Ratios and the Evolution of

Fluids Associated with Late Variscan Hydrothermal Veins and

Mineralization

Paul F Dennisa, Daniel Myhilla, Neil Allanacha, Stuart Vinena, Alexandra Formana, and Alina Marcaa

a School of Environmental Sciences, University of East Anglia, United Kingdom, p.dennis@uea.ac.uk.

We present new clumped isotope (Δ47) data for hydrothermal calcite veins from the Lower

Carboniferous limestone of the Peak District, U.K and the Clare Basin, Ireland. Whilst many of

these veins are barren, others are intimately associated with Mississippi Valley Type (MVT) base

metal mineralization such as at Ecton Hill, Staffordshire and Dirtlow Rake, Derbyshire.

Clumped isotope values for carbonate minerals allows us to determine both the precipitation

temperature of the mineral and the 18O isotopic composition of the parent fluid. The degree of

ordering of the heavy isotopes 13C and 18O in the carbonate lattice is a function of temperature. At

low temperatures the isotopes are ordered, or “clumped”, together. At higher temperatures the

isotopes become increasingly more randomly distributed. Measuring the deviation from a

stochastic distribution allows us to estimate the mineral growth temperature. With the bulk

oxygen isotope composition of the carbonate, δ18Ocarb, we can back out the δ18Ofluid value.

Veins in the Clare Basin precipitated at a temperature between 100° and 160°C, and for the Peak

District between 30° and 100°C. A striking feature of the data sets for both the Peak District and

Clare Basin is that veins, including multiple samples from single veins, plot on well-defined two

end-member mixing lines in T-δ18Ofluid space. The implication is that the veins precipitate from a

mixed fluid comprised of: (i) a hot, isotopically evolved end-member (T>160°C, δ18Ofluid >

+12‰VSMOW) and; (ii) a cooler, isotopically depleted fluid more characteristic of meteoric

groundwaters (T <40°C, δ18Ofluid < -5‰VSMOW). It is important to note that the hot end-member

has temperatures significantly greater than those we have recorded for diagenetic components in

the host limestones in either the Clare Basin or the Peak District (max. temperatures = 85°C).

The isotopic composition and temperatures of the fluid mixtures vary depending on the mixing

ratio between the two end-members. The δ18O value of the precipitated vein carbonates occupy a

restricted range between +20‰ and +24‰VSMOW. We interpret this as indicating fluids evolved

under conditions of low water:rock ratios from an original meteoric fluid. This is consistent with

δ13C values for the vein and host limestone that are indistinguishable (δ13C = +2 to +3‰VPDB).

We are surprised to find that vein precipitation temperatures are in accord with a simple two end-

member mixing model, with temperature acting as a conservative property. We envisage a simple

physical model in which hydraulic fractures propagate rapidly as a result of sharp increases in

pore fluid pressures associated with seismic pumping or seismic valve type activity, providing

flow paths for fluids sourced from deeper in the basin. Mixing of a hot fluid with local pore water

results in carbonate supersaturation and implies carbonate precipitation must occur over very

short time scales (10’s – 100’s years) as a result of mixing a Ca rich, carbonate poor, low pH

basin derived fluid with a ‘local’ meteoric fluid that has evolved towards carbonate saturation in a

system closed with respect to CO2. Hydraulic fracturing may also result in fluid effervescence

and loss of CO2 to the gas phase. Vein zoning with respect to precipitation temperature and fluid

isotope composition may result from repeated crack-seal type process.

It has not escaped our attention that our observations and interpretations of rapid carbonate

precipitation from fluids in a rock buffered system are at variance with previous suggestions that

both long times (105 - 106 years) and very large water rock ratios (104 - 105) are required for

precipitation of calcite in veins. This has implications for understanding MVT type base metal

mineralization.

36

Mineral Textures Produced from a Fe/Mg/Ca-rich Fluid at Low CO2

Pressure (<10MPa) / Low Temperature (<125˚C) Conditions

Andrew J Dobrzański

Department of Earth Sciences, University of Durham, United Kingdom, DH1 3LE,

a.j.dobrzanski@durham.ac.uk

An increase in CO2 pressure within a mineral-fluid system results in the pH of the system

lowering; the promotion of cation dissolution into the fluid; reactions switching from being

mineral-dominated to fluid-dominated and an increase in the degree of carbonate mineralisation

[1]. The effect of CO2 pressure and fluid temperature on these reactions is important when

studying aspects of hydrothermal mineralisation and the artificial carbonation of lithologies and

anthropogenically derived materials.

The textures presented in this study were formed during experiments undertaken to investigate

the reaction of steel-making slag – a Si-poor (av. 12.7% SiO2) Fe-, Mg-, Ca-rich (av. 31.7%,

9.2%, 37.6% respectively) material – with CO2(g/l/sc) and H2O(l) under varying

pressure/temperature conditions and water availabilities.

The primary aim of these experiments was to quantify the carbonation potential of the steel-

making slag over a short reaction time (19 hours) with a further aim of understanding the growth

of surface precipitation textures that would terminate any reaction with the surface of the

material.

These experiments resulted in the precipitation of distinct mineral textures upon the surfaces of

the slag grains. The individual growth-potential of these phases appears to be dictated by the

availability of water to the samples. As CO2 is present within the Earth’s crust as a gas phase,

liquid phase [2] and supercritical-fluid phase these experiments may have produced textures

analogous to textures formed within these low pressure / low temperature crustal environments.

This research could be of use in understanding the cementation of basaltic aquifers post CO2-

injection or for comparison with CO2-rich hydrothermal/liquid systems rich in Fe, Mg and Ca.

References

[1] J. P. Kazuba et al. “Experimental evaluation of mixed fluid reactions between

supercritical carbon dioxide and NaCl brine: Relevance to the integrity of a geologic carbon

repository”, Chemical Geology, vol. 217, pp. 277-293, 2005.

[2] J. Lupton. “Submarine venting of liquid carbon dioxide on a Mariana Arc Volcano”,

Geochemistry Geophysics Geosystems, vol. 7, no. 8, 2006.

37

Diatreme Volcanism and Pb-Zn Mineralisation in the Limerick District of the

Irish Orefield

Holly AL Elliotta, Thomas M Gernona, Stephen Robertsa, and Chad Hewsonb, and Adrian Boycec

a Ocean and Earth Science, National Oceanography Centre Southampton, UK,

Holly.Elliott@noc.soton.ac.uk, b Teck Ireland Ltd., The Murrough, Wicklow, Ireland, c SUERC, UK.

The Limerick Basin in southwest Ireland is an important sub-district of the Pb-Zn Orefield within

the Irish Midlands [1]. Here the occurrence of a major cluster of basaltic diatremes, spatially and

temporally associated with mineralisation, challenges previously accepted theories that the

carbonate hosted Pb-Zn deposits were not related to Lower Carboniferous volcanism. Thus the

genetic relationship between mineralisation and magmatism is poorly understood and highly

controversial. The diatremes, locally related to faulting, were emplaced into the Lower

Carboniferous carbonate stratigraphy during a period of high heat flow and magmatism

associated with Tournasian extensional activity [2]. A series of extra-crater basaltic lava flows

and pyroclastics (Knockroe Formation), commonly interbedded with shallow marine greywackes

and crinoidal limestones (Lough Gur Formation) [3] were deposited adjacent to the diatremes.

Trace element analysis of juvenile material from the extra-crater and diatreme facies have

confirmed the two are likely related, with the Knockroe sequence sourced from earlier diatreme

eruptions. Eruptions were largely phreatomagmatic in nature, and the high heat flow and water

supply in the shallow marine environment, have implications for the operation of hydrothermal

systems early in the eruptive history of the cluster. Base metal mineralisation occurs as

replacement of Black Matrix Breccias (BMB), formed during the passage of hydrothermal fluids

through the limestone country rock. Diatreme clasts within the mineralised BMB and ore-forming

minerals at the base of the diatreme, suggests mineralisation post-dates or is contemporaneous

with magmatic activity. Sulphur isotope analysis of sulphide phases in the system reveals a

unimodal signature very similar to that of the Lisheen Mine [4]. Data ranges between -45 and +20

%o with a mode of -4 %o and a small very negative pyrite peak at -38 %o. Diatremes exhibit a

combination of hydrothermal and bacteriogenic sulphur signatures, but have a modal value of 4

%o, which may reflect a magmatic sulphur input. Limerick ore-forming minerals have a more

positive isotopic ratio than that of Lisheen, taken to indicate a greater influence of hydrothermal

fluids. The presence of ore-forming minerals and a large proportion of hydrothermal sulphur

within the base of the diatremes suggest that they acted as permeable conduits, facilitating the

flow of metal-rich fluids into the mineralising system. Therefore a clear genetic link exists

between the Lower Carboniferous volcanism and the high concentrations of base metal

mineralisation in the Limerick area.

References

[1] P. Redmond “The Limerick Basin: An Important Emerging Subdistrict of the Irish Zn-

Pb Orefield”, SEG newsletter, vol. 82, pp. 20-25, 2010.

[2] P. Muchez et al. “Extensional tectonics and the timing and formation of basin-hosted

deposits in Europe”, Ore Geology Reviews, vol. 27, pp. 241-267, 2005.

[3] I. D. Somerville et al. “Biostratigraphy of Dinantian limestones and associated volcanic

rocks in the Limerick Syncline, Ireland”, Geological Journal, vol. 27, pp. 201-222, 1992.

[4] J. J. Wilkinson, and S. L. Eyre. “Ore-forming processes in Irish-Type carbonate-hosted

Zn-Pb deposits: Evidence from mineralogy, chemistry, and isotopic composition of

sulphides at the Lisheen Mine”, Economic Geology, vol. 100, pp. 63-86, 2005.

38

Geophysical Approach of the Lead-Zinc Mineralization the Synclinorium of

Verviers (Belgium)

Maxime Evrarda, Eric Pirardb, and Frederic Nguyenc

a University of Liège, Belgium; maxime.evrard@ulg.ac.be, b GeMMe, University of Liège,Belgium, c GEO3

University of Liège, Belgium.

The new ore deposits discoveries are more and more complex: lower grades, smaller size, higher

depth, with complex mineralogy and geometry…Geophysical prospecting methods should be

adapted and improved in order to respond to the actual needs of the mining industry.

The synclinorium of Verviers (Eastern Belgium) has produced the overwhelming majority of the

Belgian Pb-Zn concentrates (more than 2 million tons) from historical time until the beginning of

the 20th century, but some unexploited ore deposits are still present in the basement such as in

Plombières. Indeed, the biggest part of the extracted ore was located at low depth (max 290m)

where the Paleozoic basement outcrops.

The Pb-Zn ore deposits of Belgium are classified as Mississippi Valley type deposits and consist

mainly of Pb-Zn-Fe sulphides and oxides veins/lodes hosted in carbonated rocks [1,2].

Mineralizing fluids originated from seawater evaporation [3] during carboniferous era and

percolated to the Cambro-Silurian basement causing a dolomitization of the crossed limestone

[4]. Mineralized dense brines were then expulsed during the Jurassic era via transversal faults

generated by the Rhine graben extension [4].

Three geophysical techniques are used in this project to inspect the MVT ore deposits: electrical,

gravimetric and magnetometric methods. The data obtained will then be combined using

innovative inversion techniques and constrained with drill-hole information allowing better

detecting and targeting the Pb-Zn deposits.

References

[1] V. Coppola et al. “The “calamine” nonsulphide Zn-Pb deposits of Belgium:

Petrographical, mineralogical and geochemical characterization”, Ore Geology Reviews, vol.

33, pp. 187-210, 2008.

[2] L. Dejonghe, and D. Jans D. “Les gisement plombo-zincifères de l’Est de la Belgique”,

Chronique de la Recherche Minière 470, vol. 3, pp. 3-24, 1983.

[3] P. Muchez et al. “Origin and migration pattern of paleofluids during orogeny: discussion

on the Variscides of Belgium and Northern France”, Journal of Geochemical Exploration,

vol. 69-70, pp. 47-51, 2000.

[4] S. Dewaele et al. “Fluid evolution along multistage composite fault systems at the

southern margin of the Lower Paleozoic Anglo-Brabant fold belt, Belgium”, Geofluids, vol.

4, pp. 1-16, 2004.

39

Galvanic Dissolution of Seafloor Sulphide Ore Deposits

Emily K Fallona, Tom B Scotta, Richard A Brookerb

a Interface Analysis Centre, School of Physics, University of Bristol, UK, e.fallon@bristol.ac.uk,

b School of Earth Sciences, University of Bristol, UK.

Acid rock drainage is a natural weathering process that is often exacerbated by mining activities,

common in terrestrial sulphide ore deposit mines. A similar weathering process occurs on

seafloor massive sulphide (SMS) ore deposits. Unlike terrestrial deposits, the anticipated results

are oxide formation, negligible metal release and minimal net acid generation due to the buffering

capacity of seawater and low solubility of iron at near neutral pH [1]However, galvanic processes

have never been fully considered in this weathering context. Whilst dissolution studies of specific

sulphide minerals have been undertaken [2], the majority are within the context of conventional

acid mine drainage [3]. No dissolution studies emulate the true composition of sulphide ore

deposits that either sit passively on the seafloor or are actively mined in a colder, more saline, and

alkaline context. These deposits include a variety of minerals, and it is the interaction of these

minerals and inclusions as galvanic cells that may substantially increase the dissolution of metals

into the water column [4]. Whilst this galvanic dissolution has the potential to occur naturally on

the seafloor, both the exploration and extraction phases of deep sea mining have the potential to

agitate and expose a high surface area of fresh sulphide minerals to seawater and exacerbate this

natural effect. If any heavy metal release is not balanced by subsequent oxidation and

precipitation, there is the potential for toxicity to benthic ecosystems, bioaccumulation and

dispersal through currents.

Dissolution experiments have been undertaken to determine abiotic dissolution during both

passive and active mining conditions. Factors to consider include mineralogy, bulk chemistry,

temperature, pressure, salinity, dissolved oxygen as well as grain size distribution and surface

area of the sediments. Results will provide an understanding of what metals are released over

time in passive and active mining conditions, implications of grain size produced through mining

that is required to reduce any effect during mining as well as indicate the economic worth of

inactive SMS deposits.

We present preliminary characterisations and dissolution experiments undertaken with pyrite

cubes as well as samples from Trans-Atlantic Geotraverse (TAG), Mid Atlantic Ridge.

Experiments were controlled at 1 atm, 10-11C, <45 m grain size, 8-9 pH, ~9 mg L-1 dissolved

oxygen and 35 psu. Results suggest that mineralogy and galvanic cells are likely to play a role in

the dissolution and release of heavy metals (Cu, Pb) is consistent over timescales of hours. Future

experiments will seek to refine P, T variables to better emulate seafloor conditions. Furthermore,

a range of natural sulphide samples from various tectonic settings (high temperature vent,

ultramafic hosted, back arc rift) will be used in experiments to further understand how

mineralogy and geochemistry plays a role in this process.

References

[1] M. Schoonen et al. “Effect of temperature and illumination on pyrite oxidation between

pH 2 and 6”, Geochemical Transactions, vol. 1, no. 4, pp. 1-23, 2000.

[2] R. A. Feely et al. “Composition and dissolution of black smoker particulates from active

vents on the Juan de Fuca Ridge”, Journal of Geophysical Research, vol. 92, pp. 11347-

11363, 1987.

[3] P. Acero et al. “Sphalerite dissolution kinetics in acidic environment”, Applied

Geochemistry, vol. 22, no. 9, pp. 1872-1883, 2007.

[4] P. K. Abraitis et al. “Acid leaching and dissolution of major sulphide ore minerals:

processes and galvanic effects in complex systems”, Mineralogical Magazine, vol. 68, no. 2,

pp. 343-351, 2004.

40

The Chemistry of Chlorite and Epidote within the Propylitic Alteration Zone

of the Lagalochan Porphyry Cu-Au-Mo Prospect, Argyll, Scotland

Harry Fishera, Robin Armstrongb, Clara Wilkinsonb, and Jamie Wilkinsonb

a Department of Earth Science and Engineering, Imperial College London, United Kingdom,

harryemfisher@gmail.com, b Department of Earth Sciences, Natural History Museum, United Kingdom.

This study focuses on the Lagalochan mineralized centre in Argyll, Scotland.

Mineralization was discovered by BP Minerals and the British Geological Survey in the

1970s and 1980s; it comprises of a large porphyrite intrusion which hosts up to 13g/t Au

and 0.5% Cu [1]. Widespread hydrothermal alteration has resulted in abundant chlorite

and minor epidote development consistent with a propylitic alteration zone. Fieldwork

was undertaken in September 2014 to sample the lithologies surrounding the deposit with

particular focus on the presence of chlorite- and epidote-bearing rocks. The aim of the

project is to analyse the major and trace element chemistry of chlorite and epidote to

determine the differences in geochemistry between these minerals when formed during

hydrothermal (propylitic) alteration as opposed to within regional metamorphic

assemblages. This work will also examine the application of the use of chlorite and

epidote chemistry as an exploration tool for porphyry systems in Greenschist facies

metamorphosed domains [2, 3].

Sampling was focused on metabasic intrusive sheets locally mapped as epidiorite [4],

which are part of the Tayvallich Subgroup of the Argyll Group. The country rock

metamorphic units are part of the Dalradian Supergroup, which were intruded by a

porphyrite into the Crinan Grits and Tayvallich Volcanic formations. 25 samples were

selected for EDS-SEM analysis to determine the mineralogy of each sample as well as

the major element chemistry of chlorite and epidote grains present. The characterized

chlorite and epidote grains were then subjected to laser ablation ICP-MS analysis. The

results of trace element analyses of the chlorite and epidote will be presented and their

spatial distribution in relation to the mineralized centre discussed. Whole rock

geochemical data using a handheld XRF scanner will also be summarised.

References

[1] M. Harris et al. “Geology and Mineralization of the Lagalochan Intrusive Complex,

Western Argyll, Scotland”, Transactions of the Institution of Mining and Metallurgy, vol. 97,

pp. B15-B21, 1988.

[2] J. J. Wilkinson et al. “The chlorite proximitor: a new tool for detecting porphyry ore

deposits” Journal of Geochemical Exploration, in revision.

[3] D. R. Cooke et al. “New Advances in Detecting the Distal Geochemical Footprints of

Porphyry Systems - Epidote Mineral Chemistry as a Tool for Vectoring and Fertility

Assessments”, Society of Economic Geologists Special Publication, vol. 18, pp. 127-152, 2014.

[4] J. Knill. “The pre-Tertiary geology of the Craignish-Kilmelford District, Argyllshire”,

PhD Thesis, University of London, 1957.

41

Science and The City – the Status of Our Gold Industry1

Bob Foster

Stratex International Plc, 180 Piccadilly, London, W1J 9HF

The gold mining sector is defined by a complex and dynamic interplay of a wide

spectrum of parameters including: the demand for and supply of this rare metal; the

science and practise of exploration, mining, and processing to meet the demand; the

capabilities and motivation of the professionals that deliver the practise, the vision and

objectives of the Boardroom personnel that make the ultimate decisions; the jurisdictional

risks that play an important role in deciding where to explore and exploit the metal; the

stakeholder expectations of those jurisdictions; the ability of the explorer or developer to

secure or generate the necessary capital; and, last but not least, the price of the yellow

metal, which in turn is governed by all the foregoing and more!

Following an all-time high price per ounce (in terms of current value) of US$1,900 in

mid-2011 and a range-bound price of $1,600 - $1,800 through 2012, the decade-long bull

market for gold came to a crashing halt in the first half of 2013. Sentiment had shifted

against the metal, led by a strengthening US dollar and lessening concerns about

inflation, and the price retreated to around $1,200 where it sits at the time of writing. In

time-honoured fashion major gold-mining companies slashed their exploration budgets,

substantially reduced their exploration teams, and buckled down to focus on cost-

effective production, with exploration focused more on brownfields sites.

The search for new gold deposits continues, nevertheless, but the rate of new discoveries

and addition of substantial resources to the in-the-ground resource base has not kept pace

with the exploitation of existing resources. The Americas, Australasia, and West Africa

remain favoured exploration destinations but jurisdictional risk remains the prime factor

in discriminating amongst the best metallogenic terranes for exploration targets, with

physical (security) risks particularly high in certain African countries and wider concerns

of resource nationalism.

Against this backdrop, the small-cap (“junior”) companies offer a way forward as they

have in the past – well-managed entrepreneurial teams that have the hunger and vision to

discover and the flexibility to make exploration decisions quickly. Flat management

usually prevails, with at least one or two directors putting boots on the ground and

working with their exploration teams.

Ultimately, whether major company, mid-cap, or small-cap, the industry revolves around

the need to raise capital and sooner or later this devolves down to the World’s major

stock exchanges – London, Toronto, New York, Australian, Johannesburg, and Hong

Kong at the forefront. At the end of the day it’s here in “The City” that it all comes

together and the “economic” of our economic geology becomes truly focused – and

companies flourish or fade away. This contribution will provide a brief insight to the

remarkably complex framework that dictates how, where, and why we explore for gold.

1An abridged version of an abstract and paper presented at Gold14@Kalgoorlie

42

Mineralogy of the Newly Recognised Dolerite-Associated IOCG-s of the

Western Cloncurry District, NW Queensland, Australia

Benjamin W Francis-Smitha, David A Holwella, and Richard M Lillyb

a University of Leicester, University Road, LE1 7RH, United Kingdom, Bfs3@student.le.ac.uk,

b Mount Isa Mines Resource Development, Mount Isa, Australia.

The Cloncurry IOCG province is located in the Eastern Succession of the Proterozoic Mount Isa

Inlier, NW Queensland, Australia and is one of the most productive and well-studied mineral

provinces in the world. This relatively small area of approximately 150km2 boasts a highly

diverse group of IOCG mineralisation styles including Ernest Henry and the E1-Monakoff group

of deposits. These deposits, located north and east of Cloncurry, exhibit strongly breccia- and

replacement-controlled mineralisation within host lithologies that vary from intrusive diorites to

syn-volcanic sediments. A feature of all these deposits is a complex multi-stage paragenesis.

Exploration fieldwork has identified a distinct and newly-defined IOCG-style for the western

Cloncurry district. These relatively small deposits and prospects are spatially associated along an

arcuate magnetic trend coinciding with the boundary of the Williams-Naraku (A-type) batholith

complex (1500 Ma) [1]. The dolerite-associated Great Australia-Taipan (GAT), Magpie and

Rockland’s deposits are thought to represent a carbonate-rich precursor (?) mineralisation style

for the district. These strongly structurally controlled deposits and associated prospects lack the

complex overprinting geochemical signatures (e.g. F, Ba, As, U and REE) that are present in

other IOCG prospects in the Cloncurry District [2].

Early paragenetic studies from breccias and veins reveal multiple mineralisation events across the

western prospects. These are characterised by early magnetite ± amphibole, followed by coarse

pyrite + carbonate that has subsequently undergone brecciation and infill by massive chalcopyrite

± Au. A secondary chalcopyrite stage is also observed. Texturally destructive, late-stage coarse-

carbonate ± chlorite ± epidote overprints are common across the western district. The GAT

deposits have undergone moderate-strong magnetite alteration in addition to regional, sodic-

calcic alteration and limited potassic events, both pre and syn-mineralisation.

Initial results indicate that the western, dolerite-associated deposits and prospects represent both a

chemically and mineralogically discrete suite of IOCG mineralisation within the Cloncurry

district. The relatively simple assemblage of magnetite + pyrite + chalcopyrite + gold + carbonate

may indicate a more restrictive fluid history to other deposits in the region and may represent a

‘end member’ style or an early precursor of early regional fluid history. Alternatively, the

association with a dolerite host may be an important factor in controlling (impeding) subsequent

fluid-rock interaction and the development of a more complex assemblage.

References

[1] M. Williams et al. “Mineralogical and fluid characteristics of the fluorite –rich Monakoff

and E1 Cu-Au deposits, Cloncurry region, Queensland, Australia: Implications for regional

F-Ba-rich IOCG mineralisation”, Ore Geology Reviews, vol. 64, pp. 103-127, 2015.

[2] J. Cannell, and G. Davidson. “A Carbonate-Dominated Copper-Cobalt Breccia-Vein

System at the Great Australia Deposits, Mount Isa Eastern Succesion”, Economic Geology,

vol. 93, pp. 1406-1421, 1998.

43

Diamond Eruptions

Thomas M Gernon

Ocean and Earth Science, University of Southampton, UK

Diamonds are brought to the Earth’s surface via the eruption of kimberlites—volatile-rich

magmas from mantle depths of ≥150 km. Kimberlite volcanism involves the formation of

diverging pipes or diatremes, which are the locus of high-intensity explosive eruptions.

Kimberlite melts ascend from the Earth's mantle to the surface in a matter of hours to days. Their

diatreme-hosted deposits provide valuable insights into the dynamics of other types of volcanic

conduits, which are rarely exposed. Kimberlite diatremes are subject to a wide range of volcanic,

metamorphic and sedimentary processes and interactions, and in some cases, are even host to

exceptional fossil preservation. Additionally, the xenoliths and xenocrysts they contain provide

valuable information on the structure, composition and evolution of the deep subcontinental

mantle. The volcanic geology of kimberlite diatremes is typically very complex, consisting of

massive volcaniclastic deposits punctured by major steep internal contacts. Another characteristic

feature is the preservation of marginal inward dipping layered sequences in deep parts of pipes,

containing components derived from high levels.

A series of laboratory experiments was performed to determine the gas-fluidisation behaviour of

particles in confined containers, as an analogue to volcaniclastic materials in-filling a kimberlite

pipe in the presence of powerful gas flows. The observations demonstrate how fluctuations in gas

flux can produce steep internal boundaries between laminated and well-mixed regions in the pipe.

This, in turn, enables us to use structures observed in the field to constrain gas velocities in

confined environments. The observations also demonstrate how marginal inward dipping layered

sequences could slip into deep parts of kimberlite pipes, thereby affecting diamond grade and

distribution.

Recognising the structurally variable nature of kimberlite pipe-fills is important for economic

forecasting; for example, a major pyroclastic unit at Letseng (Lesotho) has yielded a relatively

high number of large (~100–250 cts) high-quality diamonds compared with the surrounding

kimberlite units. Our experimental constraints on gas velocity provide important new inputs into

thermodynamic models of kimberlite ascent and eruption, estimates of gas budget, and possibly,

even magma rheology. The ability to tightly constrain gas velocities is significant, as it enables

estimation of the maximum diamond size transported in the flow. Gas fluidisation and magma-

coating processes are also likely to affect the diamond surface properties. These results provide a

first-order framework for interpreting the volcaniclastic lithofacies of kimberlite pipes.

44

Pulsed Intrusive Activity and Magma Mixing in the Don Manuel Porphyry

Copper System, Central Chile

Amy K Gilmera, R Stephen J Sparksa, Alison Rusta, and Daniel J Condonb

a School of Earth Sciences, University of Bristol, UK, amy.gilmer@bristol.ac.uk b NERC Isotope Geoscience Laboratory, British Geological Survey, UK.

Many porphyry copper systems display evidence of magma mixing involving multiple intrusive

phases, but the role coeval mafic magma plays in the generation of porphyry copper systems is

not well understood. Investigating the timing of magma mixing, magma degassing, high

temperature fluid alteration, and ore formation, as well as the pulsed timing of the hypabyssal

intrusions at the Don Manuel porphyry copper system could answer key questions about the role

of coeval mafic magma as a source of volatiles. Located in central Chile, the Don Manuel system

is part of the Miocene-Pliocene porphyry Cu-Mo belt and is ~30 km east of the giant El Teniente

porphyry Cu-Mo deposit. Don Manuel consists of multiple intrusive units varying in

composition from 54-73 wt. % SiO2. New U-Pb ID-TIMS zircon ages of 3.975±0.057 Ma from

the quartz monzonite and 3.654±0.028 Ma from the intermediate porphyry bracket the age of the

Don Manuel system, making it the youngest system within the Miocene-Pliocene porphyry Cu-

Mo belt.

Textural and mineralogical observations of drill core and thin sections indicate that magma

mixing and hybridization may be important factors in the mineralization. Mineral disequilibria

textures provide information about the fluid dynamics of the magma and the progression of

magma mixing. Several features found in the intrusives at Don Manuel such as mafic enclaves,

igneous net-veining, heterogeneous hybrid rock textures, and complex zoning and associated

dissolution surfaces in plagioclase phenocrysts are also common in the products of arc volcanoes

of the central volcanic zone of the Andes, such as the nearby Holocene Diamante Caldera–Maipo

volcanic complex.

Within the main mineralizing intermediate porphyry suite, five different types of plagioclase

phenocrysts are recognized based on optical observations and SEM and electron microprobe

analyses. Accompanying the sharp changes in An content within the intermediate porphyry

plagioclase phenocrysts are also distinct, contemporaneous changes in trace elements such as Fe

and Mg. This correlation of changes in trace elements with changes in An content is key to

distinguishing magma mixing from changes in other conditions such as temperature, pH2O, and

pressure. Strontium concentrations within plagioclase of the igneous units at Don Manuel also

provide strong evidence that the intermediate porphyries are a hybridized suite and may represent

mixing between end members similar to the rhyodacite and the basaltic andesite in the igneous

complex.

45

Massive Sulphide Deposits of the Central Jebilet Massif, Morocco

Kathryn Goodenougha, Abderrahim Essaifib, Paul Lustya, Adrian Boycec, Ismaila N’Diayeb, and Lhou

Maachad

a British Geological Survey, UK, kmgo@bgs.ac.uk, b Cadi Ayyad University, Morocco, c SUERC, UK, d Managem Group, Morocco.

The Central Jebilet massif, in the Marrakech region of Morocco, comprises a block of

Carboniferous sedimentary rocks that were extensively deformed and metamorphosed during the

Variscan orogeny. This block, and its extension to the south of Marrakech (the Guemassa massif),

are characterised by bimodal intrusive magmatism and abundant massive sulphide deposits that

represent a major Cu-Pb-Zn resource. Mining is currently taking place at the Draa Sfar and Hajjar

mines. Previously worked deposits at Kettara, Roc Blanc and Koudiat Aicha are not currently

being exploited, but have extensive reserves remaining, and prospects such as Laachach and Ben

Slimane are being explored.

The massive sulphide deposits of the Central Jebilet have generally been assigned to the

Volcanogenic Massive Sulphide (VMS) deposit class. They have some characteristics typical of

VMS systems, although many original relationships are obscured by extensive Variscan

deformation and greenschist facies metamorphism. Notably, extrusive volcanic rocks are rare

within the metasedimentary sequence of Central Jebilet, which is dominated by pelitic schists

with subordinate metasandstones and metalimestones. The massive sulphide deposits form

steeply dipping lenses that are elongated parallel to the regional schistosity, and commonly

associated with shear zones. Their surface expression is typically marked by narrow gossanous

zones (10-100 m in width), but the deposits extend vertically and laterally for several hundred

metres to kilometres. The majority of the massive sulphide lenses are dominated by pyrrhotite,

although many have later phases of sulphide deposition that are characterised by pyrite and

chalcopyrite. The pyrrhotite-rich bodies typically show evidence of ductile deformation and

remobilisation, whilst the later phases of sulphide deposition appear to post-date the main

deformation phase.

There are currently two hypotheses for the formation of the Central Jebilet massive sulphide

deposits: (1) they are syngenetic, representing either classic VMS or SEDEX mineralisation [1,2];

or (2) they are epigenetic, formed during the waning stages of Variscan orogenesis and associated

with the bimodal intrusive magmatism in the area [3,4]. This talk will provide an overview of the

metallogenesis of the region, illustrated with case studies from the Draa Sfar and Kettara deposits.

References

[1] E. Marcoux et al. “Draa Sfar, Morocco: A Visean Pyrrhotite-rich, polymetallic

volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane”, Ore

Geology Reviews, vol. 33, pp. 307-328, 2008.

[2] C. Moreno et al. “Age and depositional environment of the Draa Sfar massive sulphide

deposit, Morocco”, Mineralium Deposita, vol. 43, pp. 891-911, 2008.

[3] A. Essaifi, and M. Hibti. “The hydrothermal system of Central Jebilet: a genetic

association between bimodal plutonism and massive sulphide deposits?”, Journal of African

Earth Sciences, vol. 50, pp. 188-203, 2008.

[4] F. Lotfi et al. “Lithogeochemical, mineralogical analyses and oxygen-hydrogen isotopes

of the Hercynian Koudiat Aicha massive sulphide deposit, Morocco”, Journal of African

Earth Sciences, vol. 56, pp. 150-166, 2010.

46

Mineralogic SEM-EDS Automated Mineralogy: A Preliminary Study on the

Quantitative Mineral Classifications and Measured Assay

Shaun D Grahama, Licia Santorob, and Alastair Croppa

a Carl Zeiss Microscopy Ltd, Cambridge, UK, b University Federico II, DISTAR, Napoli,

licia.santoro@unina.it.

The advent of ZEISS Mineralogic Mining and its utilization of the fully quantitative EDS mineral

classification methodology has resulted in substantial improvements in mineral classification

accuracy and elemental assay on SEM-EDS automated mineralogy solutions. This new solution

uses the wt.% contribution of each element present (mineral stoichiometry) to classify the mineral

phases, thus resulting in improved accuracy in mineral discrimination and assay calculations.

For this study, one random field of view (FOV) was analysed 20 times with the average number

of counts per EDS pixel (collected on a 10 μm stepping interval) ranging from 1,000 to 3,500

with 500 count increments. The analyses were carried out on a single sample from the Jabali Zn-

nonsulfides mining area [1]. Additional analyses at 500 counts and 5,000 counts, which were

repeated 10 times each on the one FOV. The aim of the study was to identify the optimal balance

of analytical speed against accuracy of EDX quantification, and to test the repeatability of results.

Previous studies on the Jabali ore deposit [1] showed that the mineralogy is complex and consists

of: Zn-carbonate and hydrosilicate (smithsonite, hemimorphite), Pb-carbonate and sulfate

(cerussite, anglesite) mixed with remnant sulfides (sphalerite and galena), and Fe-hydroxides

(mainly goethite). The host rock is dolomite that can be locally Zn- and Fe-enriched.

The initial results from this experiment suggest that within the Zn-carbonate samples, EDS

analysis below c. 2000 counts produces inadequate results when tracking Zn and Fe distribution.

EDS analysis at c. 1000 counts per pixel produced average bulk data with over 12% unclassified

EDS pixels, 63% pure dolomite and only 22% Fe-dolomite. An increase in counts per pixel

resulted in a dramatic change; c. 3,000 counts per EDS pixel provided average bulk mineral data

with only 6% unclassified EDS pixels, 35% pure dolomite and 55% Fe-dolomite This significant

change in reported mineralogy is due to the presence of Fe within dolomite at between typically

1-5 wt% which is undetectable at 1000 counts.

Further inspection of the data using the assay directly measured by Mineralogic Mining for Fe

shows that the average Fe assay at c. 1,000 counts is 1.39%, whilst a c. 3,000 count analysis

provides an average assay value of 2.52%. Relative standard deviation for the c. 1,000 counts is

16.28%, while was only 4.35% for c. 3,000 counts. To further outline this trend, several analyses

with c. 5,000 counts per EDS pixel were carried out; this data showed how average bulk data of

unclassified EDS pixels is 5%, for pure dolomite 25% and Fe-dolomite 66%. Fe assay produced

an average assay value of 2.74% with a relative standard deviation of 1.69. Time length per

analysis must also be considered, as higher counts per EDS pixel mean longer analysis time.

However, this study outlines the importance of analysis optimization and balancing data quality

with analysis time. In conclusion, this case study outlines how, when using SEM-EDS automated

mineralogy, higher counts per EDS pixel are required to produce more precise and representative

data. Failure to use a sufficient number of counts and non-quantitative EDS can result in mineral

phase mis-classification, incorrect tracking of elemental distribution and unrepresentative

calculated assay values.

References

[1] N. Mondillo et al. “The Jabali nonsulfide Zn–Pb–Ag deposit, western Yemen”, Ore

Geology Reviews, vol. 61, pp. 248-267, 2014.

47

The Evolution of Gold Bearing Veins in the Klondike, Yukon, Canada

Matthew Grimshawa

a School of Earth and Environment, University of Leeds, Leeds, ee09mrg@leeds.ac.uk.

The Klondike Gold District is world famous for the huge amount of placer gold that has been

recovered since the great gold rush of 1896. Exploration and research has been driven by the

disparity between the 20+Moz of placer gold versus only 1240oz recovered from in situ

occurrences [1]. The largest of these lode occurrences is located on the Lone Star ridge which is

flanked by the extremely rich Eldorado and Bonanza creeks (7Moz) [2]. Development of the

geological understanding of the area has been hindered by complex lithologies, multiple phases of

deformation, deep weathering and a lack of exposure. However, recent detailed lithological

mapping, structural interpretation and geochronological data has constrained the timing of

mineralization and its relationship to the regional geology.

This PhD project aims to characterise gold bearing veins across the Lone Star area in order to

illuminate the controls on the Lone Star hydrothermal system. The current deposit model for the

Klondike mineralization is inferred to be ‘orogenic’ however, the specific elements of the source-

transport-trap model remain unclear. A lack of regional compression, faulting and contemporary

magmatism demand that other factors influenced the generation of the auriferous veins [1].

Recent correlation of the spatial distribution of gold alloy signatures with detailed

lithogeochemical mapping suggests that local remobilization could play an important role.

Programs of analysis will establish the extent and nature of fluid rock interaction and the

conditions of mineralization.

Although the analysis has not been conducted the preliminary hypothesis is that the fluids may be

very locally sourced. Geochronology suggests mineralization postdates a period of very rapid

uplift of the host rocks, a key driver for metamorphic dehydration, whereby liberated fluids

enhanced remobilization of gold from local gold rich schist units [1]. The processes involved in

this mechanism for generating a gold deposit are plausible, however the evidence to prove this at

Lone Star have not been identified. The development of a deposit model for the Lone Star

auriferous hydrothermal system will not only underpin approaches to exploration but contribute a

case study to the wider debate on orogenic gold genesis.

References

[1] M. M. Allan et al. “Magmatic and Metallogeni Framework of West-Central Yukon and

Eastern Alaska”, Society of Economic Geology, Special Publication vol. 17, pp. 111-168,

2013.

[2] R. J. Chapman et al. “Microchemical Studies of Placer and Lode Gold in the Klondike

District, Yukon, Canada: 1. Evience for a Small, Gold-Rich, Orogenic Hydrothermal

System in the Bonanza and Eldorado Creek Area”, Economic Geology, vol. 105, no. 8, pp.

1369-1392, 2010.

48

Toward the Development of Automated Mineral Identification with the Zeiss

Mineralogic Platform for the Routine Analysis of Mineral Exploration

Samples by Laser Ablation Inductively-Coupled-Plasma Mass Spectrometry

Eloise M Harmana, Clara C Wilkinsona,b, William Brownscombea,b, Jamie J Wilkinsona, and Shaun D

Grahamc

a Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, United

Kingdom, e.harman@nhm.ac.uk, b Department of Earth Science and Engineering, Imperial College

London, Exhibition Road, London SW7 2AZ, United Kingdom, c Carl Zeiss Microscopy Ltd, 509 Coldhams

Lane, Cambridge CB1 3JS, United Kingdom.

Laser Ablation Inductively-Coupled-Plasma Mass Spectrometry (LA-ICP-MS) is a technique

used to determine trace element concentrations in minerals. This is currently being utilised at the

LODE (London Centre for Ore Deposits and Exploration) laboratory based at the Natural History

Museum London (NHM) using a New Wave NWR193nm excimer laser coupled to an Agilent

7700 quadrupole ICP-MS. The technique is being used for a variety of ore deposit research

projects, including the analysis of the trace element chemistry of chlorite and epidote for fertility

assessment and exploration targeting in the propylitic alteration domain of porphyry-epithermal

systems. LA-ICP-MS is particularly useful as it is able to determine most elements between 7Li

and 238U with detection limits of the order of a few parts per billion to a few parts per million. In

particular, it is possible to analyse elements within a mineral grain that record information

relating to the position of a sample within large alteration systems that is not resolvable using

conventional whole rock geochemistry.

Samples are typically mounted as polished resin blocks of rock or grain separates with areas of

interest highlighted using reflected light petrography. Currently, SEM-BSE images and EDS

analyses are then collected as a means of pre-selecting grains and determining their major

element compositions so that one element can be used as an internal standard for subsequent LA

analysis. The digital images and sample scans are used to relocate the grains of interest for the

LA-ICP-MS analytical stage. However, this procedure is time consuming and therefore costly,

especially for the large number of grain analyses required for mineral exploration applications.

Research is therefore being undertaken using the new ZEISS Mineralogic Mining automated

SEM-EDS solution to automate and improve the current workflow. Mineralogic is an automated

quantitative petrological analyser capable of mapping entire samples at a user-determined EDS

pixel resolution. The application of ZEISS Mineralogic Mining thus makes it quick and easy to

accurately locate and map all epidote and chlorite grains in a sample using the fully quantitative

EDS mineral classification technology. Although not currently possible, the aim is to fully

integrate Mineralogic as an automated precursor to laser analysis. The utilisation of this

technology in the analytical protocol will result in improved efficiency and reduced cost, bringing

these mineral chemistry tools within the reach of routine exploration budgets.

49

Talc Mounds on the Mid-Cayman Spreading Centre

Matthew RS Hodgkinsona, Bramley J Murtona, and Stephen Robertsa

a National Oceanography Centre Southampton, UK, Matthew.Hodgkinson@noc.soton.ac.uk.

Discovered in 2010 as part of RRS James Cook Cruise 044 to the ultra-slow spreading Mid

Cayman Spreading Centre, the Von Damm Vent Field (VDVF) is an unusual hydrothermal vent

field that consists predominately of talc with accessory microcrystalline silica and sulphides.

Comprising 4 conical mounds, the largest of which is 75 m high and 120 m in diameter, it

features chimneys venting clear fluids at temperatures of up to 215°C with a pH of 6. Elsewhere

across the active site, both focussed and diffuse flow areas emit fluids with temperatures of up to

150°C.

Situated at a seawater depth of 2300 mbsl, the VDVF is hosted in an assemblage of altered

gabbro and serpentinised peridotite on the footwall of the Mount Dent oceanic core complex.

These tectonic structures, common at ridges with full spreading rates of up to 75 mm/year, expose

lower crustal and upper mantle rocks at the seafloor, and occur when the magma supply is not

enough to accommodate full spreading rate.

Talc occurs as botryoidal bands or platy and dendritic clusters in active chimneys, and as

reworked massive and clastic assemblages in mound material. Microcrystalline silica is

intergrown with talc, and sulphides, including chalcopyrite, pyrite, sphalerite and galena, occur as

thin bands or disseminated within the groundmass.

Further, inactive mounds of botryoidal talc and silica were discovered within 1 km of east and

south of active site, giving a total talc mass of ~900,000 tonnes. These mounds are up to twice the

volume of the main cone at the active site, and suggest that hydrothermal activity has occurred at

the top of Mt. Dent for thousands of years.

The NNW and ESE alignment of the mounds and major fault scarps suggest a strong structural

control imposed by Mt Dent as axis-parallel extensional faulting occurs in response to the uplift

of the lower oceanic crust and upper mantle. These faults provide pathways for fluids to ingress

deep into the basement where they react with both mafic and ultramafic rocks at <350°C forming

an Si-rich, moderate pH and temperature that is low in base metals and precipitates talc on mixing

with seawater.

50

A New Petrographic Study of Orogenic Gold Mineralization in the Castromil

Prospect, Northwest Portugal

Cameron L Hoopera, Gawen RT Jenkinb, and Daniel Jamesc

a Department of Geology, University of Leicester, UK, ch287@le.ac.uk,

b Medgold Resources Corp, Portugal.

In NW Iberia, orogenic gold mineralization occurs in both granites and metasediments (Noronha

et al., 2000). In the case of the Castromil prospect located East of Porto, Portugal, the Castello de

Paiva granite hosts gold mineralization, where the primary structural control is thought to be

associated to the northwest-trending Railway Fault.

Work conducted by Vallance et al. (2002) produced a paragenesis and metallogenic model,

although some of this is now disputed by Mackenzie and Craw (2014). The deposition of gold in

microfractures in quartz-hosted sulphides was proposed, although specific attention was not paid

to the pure sulfide veins (which have largely been oxidized to iron oxides) which contain the

highest gold-arsenic grades. In addition, mineral assemblage and associated textures were not

analysed in detail. It is important to address these problems when targeting similar deposits in the

Valongo region as knowledge of paragenesis can be used to interpret where gold can be found

and what metallurgical processing may be required. This study aims to investigate the nature of

mineralization at Castromil in order to better understand the gold paragenesis, whilst also

analyzing the different vein types for composition. The area has very good potential for this kind

of study due to firstly, the main structure (the Railway Fault) being well exposed and secondly,

the presence of abundant veining.

A suite of representative samples have been collected from the Castromil prospect from the

different types of field-observed mineralization. These include: quartz pods and veins hosting

disseminated sulphides; massive sulphide veins that have largely been oxidized to iron oxides

with characteristic boxwork textures, and; late stage cockscomb quartz veins, that contain minor

iron oxide between crystals. In order to determine a paragenesis, petrographic studies, including

SEM, will be carried out on these, with attention paid to sulfide mineral textures and overprinting

relationships. Results will then be compared to that of Vallance et al. (2002). Specific interest will

be directed towards analyzing the different mineralization types, as some may be richer in gold

than others.

Preliminary microscope studies have found features including: growth zonation in arsenopyrite

and cockscomb quartz; mineral inclusions in pyrite crystals, and; a large amount of fluid

inclusions within quartz crystals, these will be analysed in order to test the formation

temperatures that Vallance et al. (2002) proposed.

References

[1] D. Mckenzie, and D. Craw. "Controls on gold mineralization at the Valongo, Vila de

Rei, Salguerio, Castromil, Serra da Quinta and Limarinho prospects, northern Portugal”, June 2014.

[2] F. Noronha et al. “A three stage fluid flow model for Variscan gold metallogenesis in

northern Portugal”, Journal of Geochemical Exploration, vol. 71, pp. 209-224, 2000.

[3] J. Vallance et al. “Fluid–rock interactions and the role of late Hercynian aplite intrusion

in the genesis of the Castromil gold deposit, northern Portugal”, Chemical Geology, vol. 194,

pp. 201-224, 2003.

51

Sulphide Slumping in Magma Conduits: Evidence from the North Atlantic

Igneous Province of Scotland and Greenland

Hannah SR Hughesa, Iain McDonalda, David A Holwellb, Adrian J Boycec, and Andrew C Kerra

a School of Earth and Ocean Sciences, Cardiff University, UK, HughesH6@cf.ac.uk, b Department of

Geology, University of Leicester, UK, c Scottish Universities Environment Research Centre, University of

Glasgow, UK.

Sulphides and platinum group minerals are documented in chromitite layers from the ultramafic-

mafic Eastern and Western Layered Series on the Isle of Rum [1,2] and in a single ultramafic

volcanic plug in the NW of the island [3]. However, there has been no systematic study to

determine the abundance of sulphides in volcanic plugs elsewhere on Rum, or to establish where

sulphide liquids formed and collected. Recent S-isotopic studies on the Isle of Skye have

highlighted the role of isotopically light S-rich Jurassic sediments in triggering S-saturation in

ascending Palaeogene mafic magmas [4]. Power et al. identified a light crustal δ34S signature for

intercumulus sulphides in the NW Sgaorishal plug on Rum, but failed to establish if the parental

sulphide liquids had been entrained upwards or downwards through the conduit. Depending on

the fluid dynamics prevailing in the conduit and the absence of light δ34S host rocks both

scenarios are plausible. We examine a larger suite of peridotite volcanic plugs on Rum, using

whole-rock geochemistry, δ34S and sulphide trace element compositions to decipher controls on

sulphide accumulation in these near-surface magma conduits.

Sulphides occur as very small interstitial minerals in all ultramafic plugs on Rum, recording

magmatic δ34S and S/Se ratios, and demonstrating that conduit magmas were already S-saturated.

However two plugs in NW Rum have coarser sulphides with light δ34S and elevated S/Se ratios.

For these plugs, additional sulphur contamination probably involved Jurassic mudrocks, with

characteristically light δ34S which have since eroded away. Projecting Hebrides Basin sediments

above the preserved unconformable base of Triassic rocks, the Jurassic mudrocks would have

outcropped up to ~ 100m above the current level of exposure. We suggest that once active

magma transport ceased, sulphide liquids sank down through the conduit over a distance of

several hundreds of meters, and over a period of a few days. Such sulphide ‘slumping’ may be

observed in other vertical/steeply inclined magma conduits globally, e.g. in the Macrodykes of

East Greenland. This model may be used to explain S-isotopic compositions which indicate

contamination of magmas by crustal S, but with no appropriate lithology to support this either

locally or deeper in the system. But we emphasize the difference between our model of sulphide

sinking in a non-active conduit or during magma ‘suck-back’ vs. reverse (downward) sulphide

flow in an active conduit, such has been suggested for conduits at Noril’sk Talnakh [5].

References

[1] L. J. Hulbert et al. “Metallogenic and geochemical evolution of cyclic Unit 1, lower

Eastern Layered Series, Rhum”, Institute of Mining and Metallurgy, 1992.

[2] A. R. Butcher et al. “Platinum-group mineralization in the Rum layered intrusion,

Scottish Hebrides, UK”, Journal of the Geological Society, London, vol. 156, pp. 213-216,

1999.

[3] M. R. Power et al. “Diversity of platinum-group element mineralization styles in the

North Atlantic Igneous Province: new evidence from Rum, UK”, Geological Magazine, vol.

140, pp. 499-512, 2003.

[4] H. S. R. Hughes et al. “Contrasting mechanisms for crustal sulfur contamination in the

British Palaeogene Igneous Province: evidence from dyke and sill complexes on Skye”,

Journal of the Geological Society, London, under review.

[5] N. T. Arndt. “Insights into the geologic setting and origin of Ni-Cu-PGE sulfide deposits

of the Norilsk-Talnakh region, Siberia,” Reviews in Economic Geology, vol. 17, pp. 190-215,

2011.

52

Scottish Caledonian Mafic Magmatism: An Analogy to Alaskan-Type

Complexes and PGE Mineralisation?

Hannah SR Hughesa, Iain McDonalda, Kathryn M Goodenoughb, Chris Sangsterc, and Andrew C Kerra

a School of Earth and Ocean Sciences, Cardiff University, UK, HughesH6@cf.ac.uk, b British Geological

Survey, Murchison House, Edinburgh, UK, c Scotgold Resources, Tyndrum, Stirlingshire, UK.

Alaskan-type complexes are deep-seated pipe-like and concentrically zoned ultramafic-mafic

intrusions located within continental arc settings [1]. These dome-shaped bodies are thought to

have been injected as mantle-derived ultramafic alkaline magma diapirs comprised of dunite or

pyroxenite cores with a gabbroic margin. Alaskan-type complexes represent differentiated calc-

alkaline basaltic magmas in feeder pipes of volcanoes probably erupting andesitic lavas [2]. The

bulk platinum group element (PGE) systematics of Alaskan-type complexes have many

characteristic features: a depletion in Ru (such that Ru/Ir ratio is < 1); elevated Pt; and depletion

in Pd. Platinum group minerals (PGM) are associated with chromitites and Pt-Fe alloys occur in

dunites and magnetite-rich clinopyroxenites [1].

In the Scottish Caledonides, ‘post and late-tectonic’ intrusions with both mafic and ultramafic

components include the Loch Loyal Syenite Complex at 426 Ma [3], Loch Borralan Syenite

Complex at 429.2 ± 0.5 Ma [4], Garabal Hill – Glen Fyne at 428 ± 9.8Ma [5] and Ballachuilish

diorites at 433.5 ±1.8 Ma [6]. The calc-alkaline basaltic-andesitic Lorn Plateau Lavas are

contemporaneous with late- to post-tectonic Grampian intrusions (U-Pb zircon age 425 ± 0.7 Ma;

[5]) and the similarity in Nd, Sr and Pb isotopes between Loch Borralan and Lorn [7] suggests a

geochemical, as well as temporal link, between the Lorn plateau lavas and various ‘late-tectonic’

Caledonian intrusions. Pipe-like appinite intrusions from the Grampian Highlands are dated to

426 – 427 ± 3 Ma [5], within error of the Lorn Lavas. Appinites have been interpreted as volatile-

rich magmas which intruded fractured country rocks along narrow brecciated pipes, venting to the

surface [8]. The appinites are compositionally unusual and likely derived from melting of

hydrated subcontinental lithospheric mantle [9]. In addition there are mineralogical and

geochemical similarities between ‘appinites’ (or diorites) and cumulate ultramafic rocks in ‘late-

tectonic’ Caledonian intrusions. Further impetus to investigation is the discovery of Ni-Cu-PGE-

Au mineralisation in the Sron Garbh gabbro-appinite intrusion near Tyndrum.

We compare the PGE, Cu and Au abundances of bimodal and/or mixed ‘late-tectonic’ Caledonian

intrusions, appinites and basaltic-andesitic Lorn Lavas, with the broad geochemical and

mineralogical features of Alaskan-type PGE complexes. Chalcophile element modelling shows

that prior to eruption, the Lorn parental magmas reached S-saturation which depleted the residual

silicate melt in chalcophile elements and deposited the PGE budget. Thus intermediate-level

(hyperbyssal) appinite pipes and appinite-bearing intrusions fed from deeper Alaskan-type

complexes are potential PGE-Cu-Au targets if they achieved S-saturation and the upwards flow

of mafic magma was maintained over an extended period.

References

[1] Z. Johan. In: The geology, geochemistry, mineralogy and mineral beneficiation of

platinum-group elements, pp. 669-720, 2002.

[2] C.G. Murray. Geol. Soc. Am. Mem. vol. 132, pp. 313-335, 1972.

[3] A.S. Walters, et al. Contrib. Min. and Pet. vol. 166, pp. 1177-1202, 2013.

[4] K.M. Goodenough, et al. J. Geol. Soc. vol. 168, pp. 99-114, 2011.

[5] J.C. Neilson, et al. J. Geol. Soc. vol. 166, pp. 545-561, 2009.

[6] J. Conliffe, et al. J. Geol. Soc. vol. 167, pp. 297-302, 2010.

[7] M.F. Thirlwall & P. Burnard. J. Geol. Soc. vol. 147, pp. 259-269, 1990.

[8] I.M. Platten. Caledonian igneous rocks of Great Britian, vol. 17, 1999.

[9] M.P. Atherton & A.A. Ghani. Lithos, vol. 62, pp. 65-85, 2002.

53

Novel Environmentally-Friendly Ore Processing Techniques for the 21stC

Gawen RT Jenkina, Ahmed ZM Al-Bassamb, Robert HC Harrisb, Andrew P Abbottb, Daniel J Smitha,

David A Holwella, and Chris J Stanleyc

a Department of Geology, University of Leicester, UK, grtj1@le.ac.uk, b Department of Chemistry,

University of Leicester, UK, c Earth Sciences Department, Natural History Museum, UK.

The processing of ore minerals to obtain metals nearly always involves hydrometallurgy or

pyrometallurgy. These processes have a high energy demand (and thus CO2 footprint), from e.g.

the production of strong acids/bases to dissolve ores; being high temperature processes; and the

clean-up of resulting wastes. Thus it is desirable to develop more energy efficient and

environmentally compatible methods. Leicester has been at the forefront of the development and

application of ionic liquids to the processing of metals [1] and here we describe applications to

the processing of ore minerals. Our research shows that these liquids can be used to selectively

dissolve and recover native gold [2] and tellurium, as well as all sulphide minerals studied so far.

Ionic liquids are salts that are liquid at low temperature, typically <100°C. These anhydrous

liquids are composed of ions and, like high temperature molten salts, are powerful solvents and

electrolytes. High ligand concentrations are possible allowing greater control on dissolved metal

speciation; recovery from solution can be by electrowinning, cementation, ion exchange or

precipitation. These features allow for high selectivity in both dissolution and recovery. A vast

range of ionic liquids exist – those pioneered at Leicester are deep eutectic solvents (DES);

mixtures of salts such as choline chloride with H-bond donors such as urea or citric acid. DESs

have distinct advantages in being environmentally benign, yet chemically stable. Furthermore the

components are industry-ready, being already produced in large quantities at low cost (~€2/kg).

We have developed the use of new microscopy techniques to allow us to rapidly monitor the

reaction rate of mineral samples with DES. Using an optical profiler the depth to which a

polished sample surface is etched is measured after a given duration. This technique obviates the

need to analyse solutions to monitor reaction and can monitor the dissolution rate of a number of

minerals simultaneously. Furthermore, the sample used can be a portion of a polished section of

ore or concentrate that has previously been characterised by microbeam techniques, so that

dissolution can be related to mineralogical factors, e.g. composition, zonation, inclusions etc.,

thus providing direct information of practical use for designing an ore processing method.

Minerals such as galena and chalcopyrite, as well as rarer minerals such as tellurobismuthite

(Bi2Te3), are shown to be soluble in DES by oxidation at low temperatures (45-50°C) at rates that

are very favourable in comparison to bio-oxidation or high-T hydrometallurgy. Pyrite is notably

insoluble under the same conditions, demonstrating the strong selectivity of DES.

Pyrite and arsenopyrite sulphide gangue may often contain inclusions or be intimately associated

with the target ore minerals, in particular gold, but also base metal sulphides. Thus a method to

liberate ore minerals from the pyrite/arsenopyrite would be extremely useful. We show that

pyrite, arsenopyrite, and indeed any sulphide, can be selectively dissolved by electrolytic

reduction in a DES, thus suggesting a protocol whereby target minerals can be liberated by

reduction and then dissolved by subsequent oxidation. Ionometallurgy would thus appear to offer

a whole new set of environmentally-benign tools for metallurgists that can be used in concert, or

indeed to replace, existing techniques.

References

[1] A. P. Abbott et al. “Processing of metals and metal oxides using ionic liquids”, Green

Chemistry, vol. 13, pp. 471-481, 2011.

[2] A. P. Abbott et al. “Electrocatalytic Recovery of Elements from Complex Mixtures using

Deep Eutectic Solvents”, Submitted to Green Chemistry, 2014.

54

Determining the Genetic Relationship between Breccia and Magmatic

Deposit at the Sakatti Deposit, Finland

Kate Jillingsa, William Brownscombea,b, Stuart McCrackenc, Richard Herringtonb, and Peter Doddsd

a Imperial College London, UK, katherine.jillings11@imperial.ac.uk, b The Natural History Museum,

London, UK, c Anglo American Plc, London, d AA Sakatti Mining Oy, Finland.

This poster provides a synopsis of preliminary work on the ‘Breccia’ unit that sits above the

recently discovered Sakatti Cu-Ni-PGE deposit in Finland, performed as part of an MSci project

at Imperial College in collaboration with Anglo American. This distinctive unit is found directly

on top of the deposit and is thought to be one of two known instances where such a breccia

overlies a magmatic Cu-Ni deposit, the other being Tamarack in North America. The Sakatti

Breccia has been extensively drilled by Anglo American, targeting the underlying sulphide

deposit. Although the unit has been termed a breccia, it is highly heterogeneous and includes

apparent sub-units of angular breccias, coherent dolomites and conglomeratic sections present.

Initial whole rock geochemistry suggested there are two clear sub-units within the package and

part of this research aims to ascertain whether there is a genetic relationship between these two

units.

Seven drillholes were logged during fieldwork on site and 29 representative samples were taken

and sectioned for microscope, SEM and CL analysis. Whole rock geochemistry was made

available for two holes and has been correlated with other quantitative and qualitative data to

determine element distribution within the different rock types. The seven logged drill holes have

also been used to determine lateral continuity of the unit above the deposit.

Initial textural analysis indicates that parts of the unit were of mafic origin, with ghost textures

outlined by iron oxides. The whole unit has been variably carbonate altered resulting in dolomite

and calcite formation with traces of dravite. Textural analyses using transmitted light microscopy

and cathodoluminescence infer multiple carbonate phases. Strong iron oxide staining is present

throughout, and conspicuously missing in some carbonate phases which may help define an order

of alteration events. Pervasive talc and chlorite alteration. Geochemistry work has also been done

to determine whether there is a relationship between the breccia and the underlying deposit.

Further work will try to integrate these data into a model proposing the nature and origin of the

breccia unit, hopefully leading to hypotheses to test for the relationship between the breccia and

the development of the Cu-Ni deposit.

55

Umbers of the Troodos Ophiolite, Cyprus: A Potential Rare Earth Resource?

Pierre Jossoa, Steve Robertsa, Damon Teaglea, Carlos Ponce-de-Leon-Albarranb, Richard Herringtonc

a National Oceanography Centre, United Kingdom, pmjj1e13@soton.ac.uk b Electrochemical Engineering

Laboratory, University of Southampton, United Kingdom, c Natural History Museum, United Kingdom.

Rare earth elements (REE) and critical metals are attracting acute interest due to their widespread

use within modern technologies. A perceived supply risk, notably for REE, is driving interest in

alternative and diversified deposits for REE and critical metals. The investigation of the potential

of sea-floor deposits including ferromanganese (Fe-Mn-rich) nodules and crusts [1], sea floor

massive sulfides and marine clays [2] is a key issue. However, even if these sea floor deposits

show concentrations of economic interest, their relative inaccessibility and need for advanced

mining technologies make their exploitation challenging. One approach is to investigate terrestrial

analogues of these deposits. The mid-cretaceous umberiferous deposits within the Troodos

ophiolite, Cyprus, present a direct equivalence of actual oceanic metalliferous sediments forming

at oceanic ridge axis. Umbers constitute fine-grained brown Fe-Mn rich mudstones formed by

fall-out deposit of hydrothermally-derived Fe-Mn oxyhydroxides [3, 4]. Even though umbers

show low concentration in REE in comparison with magmatic-related deposits found on land,

they present the advantage of being easy to refine with simple leaching processes thanks to an

oxyhydroxide-only mineralogy and low radioactive by-product ([Th + U] < 10 mg.kg-1).

We report results on a stratigraphic sequence of umber deposits and overlying radiolarian cherts

recovered near Theotokos Monastery west of Kampia, Cyprus. Geochemical analysis on the

profile display increasing concentrations for Si, Ti, Al, Mg, K, Zr as we progress upwards while

Fe, Ba Co, Cu and Sr decrease. Mn exhibits complex geochemical behavior with highly depleted

level in the base of the column, constant concentration in the central part of the deposit and

progressive depletion in the top. Rare earth elements for umbers display concave trends when

normalized to PAAS [5] with pronounced negative Ce anomalies (0.14 – 0.42), slight positive Eu

anomalies (1.09 – 1.16), Lan/Smn = 0.50 – 0.88, Gdn/Ybn = 1.12 – 1.61 and ƩREE = 226 – 586

mg.kg-1. This evolution translates balance between decreasing supply in hydrothermally derived

element, greater content in detrital clay as deposits get farther from the vent by spreading and

later diagenetic influence.

References

[1] M. Bau et al. “Discriminating between different genetic types of marine ferro-manganese

crusts and nodules based on rare earth elements and yttrium”, Chemical Geology, vol. 381,

pp. 1-9, 2014.

[2] Y. Kato et al. “Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth

elements”, Nature Geoscience, vol. 4, pp. 535-539, 2011.

[3] Robertson, A.H.F. Origins of ochres and umbers: Evidence from Skourioutissa, Troodos

Massif, Cyprus. Institute of Mining Metallurgy Transactions, 85, 245-251, 1976.

[4] T. J. Barret, and I. Jarvis. “Rare Earth Element geochemistry of metalliferous sediments

from DSDP LEG 92: The East Pacific Rise Transect”, Chemical Geology, vol. 67, pp. 243-

259, 1988.

[5] S. R. Taylor, and S. M. Mclennan. “The continental Crust: Its composition and

Evolution”, Blackwell Scientific, Boston, Mass, pp. 312, 1985.

56

Key Characteristics of the Magmatic Cu-Ni-PGE Mineralisation at

Manchego, West Musgrave Province, Western Australia

Bartosz T Karykowskia,d, Paul A Politob, and Jens Gutzmerc,d

a School of Earth and Ocean Sciences, Cardiff University, Wales, bkarykowski@yahoo.com, b Anglo

American Exploration (Australia) Pty Ltd, Australia, c Helmholtz Institute Freiberg for Resource

Technology, Germany, d Department of Mineralogy, TU Bergakademie Freiberg, Germany.

The late Mesoproterozoic Giles Complex of the west Musgrave Province hosts one of the largest

concentrations of mafic-ultramafic layered intrusions on Earth. Therefore, the area is highly

prospective for hosting significant Ni-Cu and platinum-group element (PGE) mineralisation,

especially following the discovery of the 446 Mt magmatic sulfide deposit at Nebo-Babel in 2000

[1]. Due to the remoteness and the cultural sensitivity of the area, the Musgrave Province is one

of the least explored and understudied areas in Australia. Apart from Nebo-Babel, a number of

low-grade prospects were identified throughout the Musgraves. A significant occurrence of

magmatic sulfide mineralisation reaching up to 0.62 wt % Cu, 0.47 wt % Ni and 1 ppm Pt + Pd

was discovered at Manchego in 2013.

Manchego was initially identified from a Spectrem airborne electromagnetic (EM) survey

representing two separate EM conductors. Subsequently, the anomaly was drill tested confirming

the presence of disseminated to massive sulfides along two gently dipping zones of up to 25 m in

thickness. The mineralisation is hosted by a range of gabbronoritic rock types located along a

linear magnetic anomaly interpreted to be a magnetite layer belonging to the layered mafic-

ultramafic succession. The contact between country rock and the Manchego intrusion was not

intersected; however, different types of metasedimentary to granitoid xenoliths in the

gabbronorites reflect the strong interaction of the magma with crustal lithologies.

In this study, we provide insights into the geology and petrology of the Cu-Ni-PGE prospect at

Manchego. Critical controls on the process of ore formation were investigated using petrography,

whole-rock geochemistry, mineral chemistry and sulfur isotopic data to facilitate a better

understanding of the factors controlling sulfide mineralisation associated with evolved mafic rock

types. These include: (1) composition of the parental magma, (2) potential triggers for sulfur

saturation and (3) the importance of crustal contamination in these mineralising systems.

Economically significant magmatic sulfide deposits associated with similar mafic rock types

include Voisey’s Bay in Canada, Noril’sk in Russia and Jinchuan in China. Hence, the Manchego

prospect provides a superb opportunity to identify key characteristics and processes responsible

for magmatic sulfide mineralisation in the Mugraves. These key characteristics may guide further

exploration in the area.

References

[1] Z. Seat et al. “Architecture and emplacement of the Nebo-Babel gabbronorite-hosted

magmatic Ni-Cu-PGE sulphide deposit, West Musgrave, Western Australia”, Mineralium

Deposita, vol. 42, pp. 551-581, 2007.

57

The Geochemistry and Oxidation of Seafloor Massive Sulphide Deposits:

Implications for Global Seafloor Resources and Mining

Robert D Knighta, and Stephen Robertsa

a Ocean and Earth Science, National Oceanography Centre, University of Southampton, UK

R.D.Knight@soton.ac.uk

The geochemistry of seafloor massive sulphide (SMS) deposits worldwide has been studied by

updating and manipulating a pre-existing geochemical database created by Hannington et al. [1]

and average chemical compositions of individual deposits have been determined. These deposits

form in various tectonic settings and as such, this data also enables the calculation of the average

expected composition of SMS deposits formed in any given tectonic setting.

The metal grades and tonnage of these deposits will be presented, with variations in these linked

to ocean spreading rates, basement composition, magma supply rate, fluid-rock interaction and

temperature. Grade and tonnage information will be used to comment on the total seafloor Cu

resource potential; current estimations of which are highly variable (e.g., [2,3,4]).

The high Cu and Au content of some of these deposits combined with their high ore to waste ratio

makes them attractive exploration and extraction targets. Nautilus Minerals were granted a

mining lease by the Government of PNG in 2011 to develop their Solwara 1 prospect; an SMS

deposit with an indicated mineral resource of 1,030kt @ 7.2 % Cu, 5.0 g/t Au, 23 g/t Ag, 0.4 %

Zn and an inferred mineral resource of 1,540kt @ 8.1 % Cu, 6.4 g/t Au, 34 g/t Ag, 0.9% Zn [5].

Although the specifics of planned mineral extraction methods remain unclear at the time of

writing, they are expected to result in both physical and geochemical impacts. In the case of

mining SMS deposits whereby sulfides are pulverized leaving fresh mineral surfaces exposed to

seawater, it is highly likely that these exposed sulphide surfaces will be oxidised resulting in a

portion of sulfide-hosted major and trace metals being released into the ocean. This is not only

potentially harmful to marine ecosystems, but may also impact rates of metal recovery.

However, little is known regarding sulfide mineral oxidation rates under seafloor conditions. As

part of the MIDAS project (Managing Impacts of Deep-seA reSource exploitation), we are

developing experiments to quantify the abiotic oxidation rates of a range of sulfide minerals

under seafloor conditions and the concentrations of major and trace metals released during these

reactions. Using this research, we aim to model the release of major and trace metals; the

quantification of which is crucial in assessing both the environmental impact of seafloor mining

and the effect of sulphide mineral oxidation on metal recovery.

References

[1] M. D. Hannington et al. “A Global Database of Seafloor Hydrothermal Systems”,

Geological Survey of Canada Open File 4598, 2004.

[2] M. D. Hannington et al. “The abundance of seafloor massive sulfide deposits”, Geology,

vol. 39, 1155-1158, 2011.

[3] L. M. Cathles. “What processes at mid-ocean ridges tell us about volcanogenic massive

sulfide deposits”, Mineralum Deposita, vol. 46, pp. 639-657, 2011.

[4] M. D. Hannington. “Comments on “What processes at mid-ocean ridges tell us about

volcanogenic massive sulfide deposits” by L.M. Cathles”, Mineralum Deposita, vol. 46, pp.

659-663, 2011.

[5] www.nautilusminerals.com/s/Projects-Solwara.asp

58

Using High Resolution SEM to Identify Daughter Crystals in Fluid Inclusions

from the Bingham Canyon Porphyry Deposit, Utah

Simon Kocherabc, Jamie J Wilkinsonabc, and Robin N Armstrongbc

a Department of Earth Science and Engineering, Imperial College London, UK, s.kocher12@ic.ac.uk,

b Department of Earth Sciences, The Natural History Museum, UK,

c London Centre for Ore Deposits and Exploration (LODE).

Fluids play a key role in mobilising, transporting and ultimately concentrating metals to form

many types of ore deposits. To analyse these ore forming fluids, preserved as fluid inclusions in

gangue and ore minerals, and to get a better understanding of the processes of ore deposition, a

variety of techniques are available.

Fluid inclusion microthermometry is by far the most widely used technique and provides

important information on the temperature and pressure regime during ore formation as well as a

basic understanding of dissolved salt species. In saline inclusions, significantly more information

on dissolved metals and anionic species can be gained by the identification and volumetric

quantification of daughter crystals, precipitated during cooling from the trapping conditions to

room temperature. However, the optical identification of daughter crystals can be difficult,

especially for opaque phases. Proton Induced X-Ray Emission (PIXE) is one method that has

been used to achieve this but it is costly and cannot quantify light elements.

As a relatively cheap alternative, Scanning Electron Microscopy has been used successfully in the

past to identify daughter minerals in large fluid inclusions [1]. The new generation of high

resolution instruments now makes it possible to image and identify smaller phases than has

previously been possible. This method has therefore been used to identify daughter phases in

molybdenite-rich veins from the Bingham Canyon porphyry deposit to shed light on the chemical

composition of Mo-transporting fluids.

Suitable samples were ground to a thickness of 500 µm and cut into 10 mm wide chips. To mount

the samples, 5 mm deep notches were cut into a standard 25 mm epoxy resin block. The sample

chips were then vertically mounted into the notches with superglue and the projecting material

sheared off to expose fluid inclusions on the broken surfaces. To evaporate the fluid and avoid

interaction between air moisture and daughter crystals the samples were stored in a heated

desiccator for 24 h prior to carbon coating. Analyses were then performed on a FEI Quanta 650

SEM at the Natural History Museum London using an acceleration voltage of 10 kV.

High salinity brine inclusions associated with molybdenite mineralisation at Bingham Canyon

predominantly contain halite (NaCl) and sylvite (KCl) as transparent daughter phases. Anhydrite

is another commonly found daughter and usually forms tabular or acicular crystals. Chalcopyrite

is the most abundant opaque daughter phase, occurring in intermediate density vapour and brine

inclusions. Molybdenite is rare as a daughter phase, even in molybdenite-rich veins, where it

occurs as small hexagonal plates. Other phases identified include pyrite and Fe-oxides. These

results indicate that Mo-stage fluids are of a H2O-NaCl-KCl composition and carry both reduced

and oxidised sulphur species at room temperature. Interestingly, although the Mo ore zone at

Bingham only contains minor Cu, the fluids responsible for transporting Mo appear to carry a

significant amount of Cu in solution based on the frequency of chalcopyrite daughter crystals.

References

[1] F. W. Metzger et al. “Scanning Electron Microscopy of daughter minerals in Fluid

Inclusions”, Economic Geology, vol. 72, pp. 141-152, 1977.

59

Evaporite Derived Hypersaline Ore Fluids in Orogenic Gold: New Boron

Isotope Data from Tourmaline in the Loulo-Bambadji District in Mali, West

Africa

James Lambert-Smitha, Alex Rochollb, David Lawrencec, and Peter Treloarc

a Centre for Earth & Environmental Science Research, Kingston University, Surrey, KT1 2EE, UK,

J.S.Lambert-smith@kingston.ac.uk, b Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum,

Telegrafenberg, D14473 Potsdam, Germany, c Randgold Resources, 1st Floor, 2 Savoy Court, Strand,

London, WC2R 0EZ, UK.

The 2.1 Ga Kédougou-Kéniéba Inlier in West Africa hosts outstanding mineral wealth, with some

45 Moz of gold and 630 Mt of iron ore hosted along the Senegal-Mali Shear Zone (SMSZ). To

the west of the SMSZ the Falémé Volcanic Belt (FVB) is comprised of calc-alkaline

volcaniclastic sediments, lavas and plutons, with iron ore hosted in a series of magnetite-apatite

skarns. To the east, the Kofi series is comprised of poly-folded clastic basin sediments intruded

by peraluminous granites, orogenic gold deposits are hosted in structurally controlled locations

within the sedimentary rocks.

A >400 ppm boron soil anomaly occurs over ~100 km of the strike length of the SMSZ with

orogenic Au mineralisation, hosted along its eastern margin, spatially associated with epigenetic

tourmaline alteration. Hypersaline fluid chemistries are interpreted to have played a role in ore

genesis. This fluid and the tourmalinisation were initially interpreted to be sourced from local

magmatism. However, stable isotope (O, C and S from hydrothermal silicate, carbonate and

sulphide minerals) and geochronological studies to date show no strong evidence to support this

association.

Heavy δ34S values (+25 ‰) from diagenetic pyrite may indicate the former presence of evaporites

in the Kofi metasedimentary rocks. New boron isotope data collected from: 1) pre-, syn-, and

post-mineralisation hydrothermal tourmaline from Au ore bodies in the Kofi series and 2)

pegmatite hosted tourmaline from the nearby Gamaye pluton. The data show that tourmaline from

pegmatite dykes in the Gamaye pluton display values typical of magmatic sourced B (δ11B from -

18.3 to -15 ‰). Conversely, hydrothermal tourmaline from within the Au ore bodies displays

δ11B values that indicate derivation of B from marine carbonate rocks and evaporites (δ11B

between -4.6 and +19.8 ‰). It can reasonably be deduced from this data that the hypersaline

fluids in the region are also sourced from the metasedimentary rocks of the Kofi series.

Hypersaline fluids are not commonly associated with orogenic gold provinces, being more widely

reported in IOCG, porphyry or skarn systems. The data presented here adds a further layer of

complexity to the orogenic gold model, demonstrating that metamorphism can give rise to

hydrothermal fluid systems with highly variable chemistries.

60

Lithological and Mineralogical Controls on the Surface Geochemistry of

Epithermal and Porphyry Prospects, Kiziltepe Gold Corridor, Turkey

Claudia Leppa, David Holwella, Zack van Collerb, and Kerim Sener

a Geology Department, University of Leicester, United Kingdom, cd182@student.le.ac.uk,

b Ariana Resources, Bridge House, London Bridge, London, United Kingdom.

The Kiziltepe Au-Ag corridor is host to low sulphidation epithermal vein deposits and is

located in Sindirgi, Western Turkey. The Kepez and Karakavak prospects are located

within this corridor, consisting of economic to sub-economic auriferous veins hosted in

volcanic rocks which form part of the western Turkey Miocene magmatic arc complex.

Nearly 15,000 soil samples and a suite of representative rock samples covering an area

67km2 were collected during fieldwork in summer 2014 and analysed by portable X-ray

fluorescence (XRF). We show that this data is effective in identifying lithologies, in

addition to the presence of mineralised structures and intrusions.

Dacites preferentially host mineralised veins, with thick rhyolitic ignimbrites, barren of

mineralisation, overlying them. Soils overlying dacite and rhyolite lithologies show Sr

highs in the dacite and Th highs in the rhyolite; thus, Sr/Th ratios in the portable XRF soil

data can be used as a criteria for distinguishing between these lithologies. A Sr/Th ratio

over 0.4 implies the soil sample is located above a dacite, with anything below this ratio

indicating a rhyolite. Soil data with high Cr and Ni can be used to identify the mafic

ophiolitic lithologies in the area. Therefore, it is possible to map very effectively the local

geology using XRF soil data alone.

Areas with anomalously high As and Sb are located over low-sulfidation epithermal Au-

Ag veins and as such, As and Sb in soils are excellent indicators of mineralisation. In

addition, they also show a large anomaly above the Kepez porphyry intrusion; indicating

a cap of silica-pyrite alteration in an area which also contains anomalously high Mo,

interpreted to represent a possible porphyry Mo-Au intrusion.

Petrological observations and 3D mineralogical studies using CT scanning of the

Karakavak and Kepez samples reveal varying textural styles of mineralisation. The

Kepez mineralisation is chalcedony-ginguro style consisting of quartz pseudomorphing

platy calcite and black ginguro material that occurs in bands or spots. The Karakavak

mineralisation consists of banded pyrite with gold dispersed along the rim of the banding.

These different mineralisation styles suggest that these prospects were deposited at

different times or by different hydrothermal systems.

61

Geological Application for the New Fault Response Modelling Module in

Move

Euan Macaulaya, Heike Broichhausena, Jenny F Ellisa, and Alan PM Vaughana

a Midland Valley Exploration, 2 West Regent Street, Glasgow, G2 1RW, UK

When a fault slips, subsequent displacement, strain and stress can be analytically calculated using

elastic dislocation theory. An analytical solution for triangular dislocation will shortly be

implemented in Move in the form of the easy-to-use Fault Response Modelling graphical user

interface. Fault Response Modelling, combined with the structural modelling and restoration

functions of Move, will offer unparalleled insights into the effects of faulting across different

time intervals and has many potential applications in earthquake-induced displacement and stress

modelling, hydrocarbon exploration and the mining industry. This range of possible applications

will be demonstrated by applying new workflows to four different case studies.

In the first case study, Fault Response Modelling will be used to model displacements and stress

changes that followed the 2008 Nura earthquake in Kyrgyzstan [1]. The second and third case

studies will demonstrate how fault-related fracturing modelled with the Fault Response

Modelling tool can be used to reduce risk in the hydrocarbon and mining industries. In the second

case study, the tool will be used to investigate the distribution of gold deposits around the Carlin

fault system in northeastern Nevada, USA [2], and how these correlate with modelled fracture

intensity. In the third case study, fault-related fractures predicted using Fault Response Modelling

in the La Concepción oil field in the Maracaibo basin of Venezuela will be used to generate a

discrete fracture network (DFN). The fourth case study will illustrate the potential of Fault

Response Modelling as a geomechanical validation tool by comparing the displacements

predicted following slip on a listric normal fault with observed hanging-wall geometries.

Acknowledgements: Petrobras Energia Venezuela are acknowledged for providing data.

References

[1] K. Teshebaeva et al. “Strain partitioning at the eastern Pamir-Alai revealed through

SAR data analysis of the 2008 Nura earthquake”, Geophysical Journal International, vol.

198, pp. 760-774, 2014.

[2] S. Micklethwaite. “Fault-induced damage controlling the formation of Carlin-type ore

deposits”, In Great Basin Evolution and Metallogeny: 2010 Symposium Proceedings (Eds.

R. Steininger and B. Pennell), DEStech Publications, Inc., pp. 221-231, 2011.

62

Are Re Concentrations in Porphyry Copper Deposits the Result of

Hydrothermal Fluid-Country Rock Interactions? Evidence from Stable

Isotope Analyses (δ34S, δ18O, δD) of the Muratdere Cu-Mo (Au-Re)

Porphyry Deposit, Turkey

Katie McFalla, Steve Robertsa, Jon Nadenb, Paul Lustyb, and Adrian Boycec

a Ocean and Earth Science, National Oceanography Centre, University of Southampton,

K.McFall@soton.ac.uk, b BGS, Environmental Science Centre, UK, c SUERC, UK.

The Muratdere deposit is a Cu-Mo porphyry system in western Turkey with significant Au, Ag,

and Re credits. The deposit is hosted by a suite of Palaeocene−Eocene granodiorite intrusions

located in the North Anatolian Belt, a pre-Jurassic subduction complex associated with the

closure of the Tethyan Ocean [1], which contains ophiolitic melange units incorporating

limestone blocks and ultramafic lenses.

The Muratdere porphyry contains several generations of quartz veins. The earliest mineralized

vein set, V2, comprises quartz-pyrite-chalcopyrite and hosts the majority of the Cu-Au

mineralization. The remainder of the Cu-Au mineralization, and some of the Mo, is associated

with disseminated chalcopyrite and molybdenite in the host porphyry. Veinset V3 is composed of

quartz and dendritic molybdenite, which is associated with the majority of the Mo and Re

enrichment. LA-ICP-MS analysis of disseminated molybdenite in the host porphyry shows

comparable Mo concentrations to molybdenite in V3, however the molybdenite within the V3

veins has significantly higher concentrations of Re - up to 3624 ppm (mean 725 ppm), than the

disseminated molybdenite which has a maximum of 1490 ppm Re and a mean of 367 ppm. This

suggests that fluids forming the V3 veins evolved in a contrasting manner to those which

precipitated the disseminated molybdenite. A further mineralized veinset, V5, is polymetallic

containing sphalerite, galena, pyrite-chalcopyrite, and barite. V5 is associated with elevated

values of Ag, Au and Te.

V2 has δ34S of +1.1‰ to +6.3‰, and a mean δ18O quartz value of 8.1‰. The disseminated

sulfides have a δ34S of −2.2‰ to +4.6‰, indicating a magmatic source, while V3 has a heavier

δ34S signature of +5.6‰ to +8.8‰, similar to values found in peridotite lenses in the Anatolian

Belt (δ34S of between +6.8‰ and +8.8‰ [2]). V3 has a mean quartz δ18O of 8.0‰, similar to V2.

V5 has much lighter δ34S values of between −5.5‰ and +2.7‰, and mean quartz δ18O of 11.3‰.

The light δ34S values of V5 appear to suggest assimilation of sedimentary sulphur. However, the

fluid δ18OV-SMOW of V5 is close to that of magmatic water at the predicted mineralizing

temperatures of 350°C (from sulphur isotope geothermometers and preliminary fluid inclusion

data). V2 and V3 show δ18OV-SMOW values between magmatic and meteoric water, suggesting that

mixing has occurred, and fluid-rock interaction modelling for V3 has shown that it is likely that

the fluids have interacted with the surrounding peridotite. We propose that hydrothermal fluid-

country rock interaction provides an enrichment mechanism for Re in this deposit.

References

[1] O. Tekeli. “Subduction complex of pre-Jurassic age, northern Anatolia, Turkey”,

Geology, vol. 9, pp. 68-72, 1981.

[2] O. Koptagel et al. “Sulfur-Isotope Study of the Ana Yatak Masive Sulfide Deposit,

Southeastern Turkey”, International Geology Review, vol. 40, no. 4, pp. 363-374, 1998.

63

Geological Constraints on Rare Earth Elements (REEs): Concentrations in

Deep Sea Clays from the Nares Abyssal Plain

Amaya Menendez Gamella

Ocean and Earth Science, National Oceanography Centre Southampton, United Kingdom,

A.Menendez@soton.ac.uk

Recent studies in a series of seafloor sediment types from the eastern South and central North

Pacific have revealed remarkably high concentrations in rare earth elements (REEs) [1]. Deep sea

Pacific clays have thus been proposed as a potential source in order to supply the world demand

for this resource. Processes regulating REE concentrations in deep sea clays are complex, and

respond to a number of geological and geochemical factors, some of which are poorly

understood.

In order to evaluate these compositions and to stablish a comparison frame with the Atlantic

Ocean, analyses have been carried out of 12 sediment samples from 6 cores collected from the

Nares Abyssal Plain (23°30' N 62°59' W in the Atlantic Ocean). Samples were collected on board

the RRS Discovery Cruise 108 and include slowly deposited pelagic red clays and rapidly-

deposited grey clays associated with turbidites, as well as mixed concentrations of both end

members. Despite their similar mineralogy and possible common detrital origin, both types of

clays are characterized by different geochemical signatures. This is attributed to differences in

their sedimentation rates and subsequent metal-enriching authigenic chemical fluxes [2]. Analysis

revealed higher REE total concentrations in red clays than in the grey clays, as well as a more

pronounced Ce anomaly in the former group. Furthermore, authigenic-related transition metals

such as Cu, Co, Ni, Zn and V show an enrichment in the red clays relative to the grey clays,

whereas that the detrital-related elements (Y, Nb, Cr, Zr, Rb, Sr) showed similar concentrations in

both groups. These differences have been interpreted as reflecting preferential presence of an

authigenic and detrital component in the red and grey clays respectively. Additionally, a positive

correlation between the REEs and Fe, Ti and Al has been found, which might be suggesting

association with a single authigenic phase such as Fe-oxide. A negative correlation with Ca has

also been observed, and is interpreted as being the result of the diluting effect of CaCO3-rich

detrital components in the sediment.

On average, total REE abundances found (ΣREE up to 240 ppm) are lower than in the REE-rich

reported sediment for the Pacific (ΣREE up to 660 ppm [1]). This fact might be due to a higher

sedimentation rate in the Atlantic, which will cause dilution of the REE concentrations in the

presence of a more abundant detrital component. Differences in the dispersal of the hydrothermal

plumes between fast- and low- spreading ridges in the Pacific and Atlantic, respectively, could

also account for the differences observed, as the hydrothermal supply for the metallic phases

which are responsible for seawater REE uptake might be significantly different between both

oceans. At the same time, the Ce anomaly has been observed to be more pronounced in the

Atlantic samples than in the Pacific. This would ultimately be reflecting more oxygenated

conditions in the Atlantic due to the action of the global ocean circulation pattern.

References

[1] Y. Kato et al. “Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth

elements”, Nature Geoscience, vol. 4, no. 8, pp. 535-539, 2011.

[2] J. Thomson et al. “Metal accumulation rates in northwest Atlantic pelagic sediments”,

Geochimica et Cosmochimica Acta, vol. 48, no. 10, pp. 1935-1948, 1984.

64

Polymetallic Zn-Pb Mineralization in the Cuzco Area (Peru): Lead Isotope

Geochemistry in the Accha-Larisa District

Nicola Mondilloa, Maria Bonia, Giuseppina Balassonea, and Igor M Villab

a Dipartimento Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli, Italy,

boni@unina.it, b Institut für Geologie, Universität Bern, Switzerland.

The Accha Zn-Pb nonsulfide deposit is located in the Andahuaylas-Yauri province (Cuzco

region, Peru), an area hosting middle Eocene to early Oligocene porphyry-Cu and porphyry-

related skarn deposits, genetically associated with the Andahuaylas-Yauri batholith [1]. This area

also hosts many Zn and Pb occurrences, which have been recently considered as distal

components of wide “porphyry Cu systems” [2].

The Accha Zn deposit (www.zincoremetals.com) is an almost fully oxidized smithsonite-

sphalerite mineralization hosted in Mesozoic rocks [3]. The mineralized zone [6,613 kilotonnes of

measured and indicated resources at 6.37% Zn and 0.78% Pb (2.20% ZnEq cutoff)] occupies the

hinge of an anticline that has been exposed by erosion. The main host to mineralization consists

of limestones with intercalated shales, but recent observations showed that part of the Zn

mineralization also occurs in an algal mound limestone. The Larisa Cu porphyry-type target area

is located a few kms west from the Accha deposit. Here, the main igneous rocks are:

diorite/tonalite, tonalite porphyry, and quartz diorite/monzonite porphyry. Together with Accha,

the Larisa Cu-porphyry constitutes a Cu-Zn-(Pb) mineralized area very similar to the nearby

Yanque-Dolores Cu-Zn-Pb district, which is one of few cases of porphyry-Cu system in the

Andahuaylas-Yauri province [2].

The Pb-isotopic compositions of the Accha smithsonite are: 206Pb/204Pb = 18.560±0.001 to

18.570±0.003, 207Pb/204Pb = 15.640±0.002 to 15.644±0.003, and 208Pb/204Pb = 38.528±0.005 to

38.538±0.008. These isotopic ratios are similar to those measured on sulfides and hydrothermal

and oxidized minerals from the Yanque-Dolores district, and are also correspondent to the mean

composition of the Tertiary magmatically-derived ores in this part of Peru [2].

In the case of the Dolores Cu-porphyry and Yanque Pb-Zn mineralization, the combined data

supported the concept that the Yanque-Dolores district was a porphyry-Cu system, i.e. the

primary Yanque Zn-Pb mineralization was deposited by the same hydrothermal system that

formed the Dolores Cu-porphyry deposit. In the case of the Accha-Larisa area, the absence of Pb-

isotopic data from Larisa sulfides hinders a direct comparison between the two deposits of the

district. However, the numerous analogies between the Accha-Larisa and the Yanque-Dolores

districts (i.e. geological setting, location, geochemical zoning), and the similar Pb-isotopic

composition between supergene minerals from both Accha and the Yanque-Dolores porphyry Cu

system, suggests that also Accha could be potentially associated to the emplacement of a

porphyry-Cu mineralization in close proximity (i.e. the Larisa Cu-porphyry).

References

[1] J. Perelló et al. “Porphyry-style alteration and mineralization of the Middle Eocene to

Early Oligocene Andauaylas-Yauri belt, Cuzco region, Peru”, Economic Geology, vol. 98,

pp. 1575-1605, 2003.

[2] N. Mondillo et al. “The Yanque Prospect (Peru): from Polymetallic Zn-Pb

Mineralization to a Nonsulfide Deposit”, Economic Geology, vol. 109, pp. 1735-1762, 2014

[3] M. Boni et al. “The nonsulphide zinc deposit at Accha (southern Peru): geological and

mineralogical characterization”, Economic Geology, vol. 104, pp. 267-289, 2009.

65

Tellus South West: Relevance to Mineral Exploration and Deposit Models, an

Initial View

Charlie Moon

Rose Cottage, Church Hill, Calstock, Cornwall, PL18 9Q, UK & Camborne School of Mines, University of

Exeter, Penryn TR10 9EZ, UK, cjm@moongeology.co.uk.

The Tellus SW data currently being released into the public domain by NERC through the British

Geology Survey and Centre for Ecology and Hydrology give many new insights into the geology

of Cornwall and Devon. Data have been released on to a website [1] and viewer although detailed

interpretation is best done in a GIS environment.

The Lidar data with a resolution of 1 m provide a detailed view of the surface topography. These

are particularly useful for detection of old mine workings, even of limited size, and of pre-19th

century age. Hill shaded Lidar images can be used to check previously published mapping

especially fault and dyke locations, particularly elvans. The Lidar data also provide a rapid means

of locating outcrops for follow up mapping.

Airborne Radiometrics (total count, K, Th, U and ratios, spacing 200 × 8 m) give a synoptic view

of the geology and allow mapping of composite granite intrusions. The latter show obvious

spatial correlations with kaolinisation and metallic mineralisation. The data also directly detect

uranium and thorium mineralisation although detection of these requires ratioing.

Magnetic data are more difficult to interpret as responses are complicated by extensive

(magnetic) infrastructure. However there is evidence of much more fault control on granite

distribution than previously described.

The geophysical data are shortly to be complemented by stream sediment and limited soil

geochemistry. Initial maps suggest patterns will be similar to the Wolfson Atlas [2] but with

wider elemental range.

References

[1] Tellus SW Web Site, http://www.tellusgb.ac.uk/

[2] J. S. Webb et al. ‘‘Wolfson Geochemical Atlas of England and Wales’’, Clarendon Press,

Oxford, pp. 70, 1978.

66

On the Feasibility of Detecting Carbonatite-Hosted Rare Earth Element

(REE) Deposits Using Remote Sensing: A Work in Progress

David A Neavea, Teal R. Rileyb, Sally A Gibsona, Martin Blackb,c, Graham Ferrierc,

Frances Walld, and Sam Broom-Fendleyd

a Department of Earth Sciences, University of Cambridge, United Kingdom, dan27@cam.ac.uk,

b British Antarctic Survey, United Kingdom, c Department of Geography, Environment and Earth Sciences,

University of Hull, United Kingdom, d Camborne School of Mines, University of Exeter, United Kingdom.

Rare Earth Elements (REEs) are crucial raw materials in a wide range of technological products,

ranging from hybrid car batteries to wind turbine generators and mobile technology and are

consequently considered amongst the critical metals, i.e. they are of increasing economic

importance and might be susceptible to restrictions in future supply. Carbonatites (igneous rocks

containing >50% carbonate minerals) and their alkaline silicate associates are by the far the most

significant host for global reserves of REEs. Carbonatite magmas are usually characterized by

high volatile contents, low viscosities and low densities making them particularly capable of

transporting large-ion-lithophile and high-field-strength elements. Most REE mineralisation is the

result of sub-solidus processes involving carbonatite-derived fluids that can precipitate rare earth-

bearing minerals directly, or lead to the alteration of primary minerals.

Many REEs have unique spectral properties at visible and near infrared wavelengths (VNIR;

400–1400 nm) that make them directly detectable with reflectance spectroscopy: most lanthanide

series elements undergo f-f electronic transitions caused by absorption of photons at specific

wavelengths resulting in multiple narrow diagnostic absorptions. Previous studies have indicated

that neodymium (Nd) has the most diagnostic and easily detectable spectral features of all the

light REEs, which can be generated by as little as 300 ppm Nd I samples [1]. Although recent

studies have demonstrated that carbonatite complexes can be identified by remote sensing [2],

previous generations of multispectral and hyperspectral instruments have been insufficiently

sensitive to resolve the narrow absorption features associated with REEs. However, improvement

in the sensitivity of upcoming instruments, such as HyspIRI and EnMap, may enable REEs to be

detected from satellite-based platforms for the first time.

In order to ground truth future remote sensing data, we have acquired spectral reflectance and

emissivity data from a range of REE-mineralised samples. Samples have been sourced from the

Harker Collection at the University of Cambridge, the Natural History Museum, Camborne

School of Mines and SRK Consulting (UK) Ltd (Cardiff), and contain the following REE-rich

phases in variable abundances: monazite-(Ce), bastnäsite-(Ce), parasite-(Ce), synchysite-(Ce) and

pyrochlore. VNIR reflectance and TIR (thermal infra-red) emissivity spectra were collected at the

NERC Field Spectroscopy Facility (FSF) at the University of Edinburgh using an ASD

FieldSpec® Pro field spectroradiometer and MIDAC field portable FTIR respectively. Initial

findings confirm the presence of strong REE absorbance features (particularly Nd) in the VNIR

reflectance spectra of REE-rich rocks from locations including Bayan Obo, China; Mountain

Pass, USA; and Kangankunde, Malawi. By resampling our reference spectra to the spectral

responses of various hyperspectral instruments it will be possible to determine the conditions

under which REEs may be positively identified using remote sensing data.

References

[1] L. C. Rowan et al. “Spectral reflectance of carbonatites and related alkalic igneous

rocks; selected samples from four North American localities”, Economic Geology, vol. 81,

pp. 857-871, 1986.

[2] E. Bedini et al. “Mapping lithology of the Sarfartoq carbonatite complex, southern West

Greenland, using HyMap imaging spectrometer data”, Remote Sensing of Environment, vol.

113, pp. 1208-1219, 2009.

67

Behaviour of Au, As, Sb, Se and Te During the Hydrothermal Alteration of

the Oceanic Crust: a Study Case from IODP Site 1256D

Clifford Pattena, Iain Pitcairna, Damon Teagleb, and Michelle Harrisb

a Department of Geological Sciences, Stockholm University, Sweden, Clifford.patten@geo.su.se, b Ocean

and Earth Science, National Oceanography Centre Southampton, United Kingdom.

Metals enriched in volcanic massive sulfide (VMS) deposits such as Cu and Zn are known to

have been partly mobilised from areas of highly altered oceanic crust [1,2]. An important sub-set

of VMS deposits are enriched in Au and associated elements such as As, Sb, Se and Te but

despite this, the mobility of these elements during seafloor alteration is not well constrained. The

concentrations of Au, As, Sb, Se and Te have been determined in a suite of 65 oceanic crust

samples from Integrated Ocean Drilling Program (IODP) site 1256D in the Cocos Plate, Pacific

Ocean. Hole 1256D penetrates a complete in-situ section of the upper oceanic crust providing a

unique sample suite to investigate the behaviour of metals during hydrothermal alteration. Gold

concentration has been determined by ultralow-level Au technique and As, Sb, Se and Te have

been determined by hydride generation-atomic fluorescence spectrometry (HG-AFS) at

Stockholm University, Sweden. Mass balance of metal mobilised during hydrothermal alteration

has been calculated by coupling our data with fresh mid-oceanic ridge basalt (MORB) glass

database [3] and Hole 1256D major and trace elements database [4].

During hydrothermal alteration, metals are mobilised to variable extent: Au, As, Se, Sb, S, Cu, Zn

and Pb are depleted in the sheeted dyke complex and the plutonic rocks with mobilities of -46%, -

47%, -6%, -27%, -13%, -10%, -9% and -46% respectively. Zinc shows enrichment in the upper

sheeted dykes indicating fractionation relative to other metals which could explain the Cu-rich

affinity of mafic VMS. Important metal enrichment occurs in the transitional zone associated with

sulphide precipitation except for Cu. Arsenic and Sb are enriched in the volcanic section due to

seawater-derived fluid circulation. Calculations suggest that large quantities of metal are

mobilised but only a portion is eventually trapped as VMS mineralisation. Metal composition and

Au to base metals ratio in hydrothermal fluids are similar to that of mafic VMS and a ten times

enrichment of Au would be needed to form an Au-rich VMS.

References

[1] J. C. Alt et al. “Subsurface structure of a submarine hydrothermal system in ocean crust

formed at the East Pacific Rise, ODP/IODP Site 1256”, Geochemistry, Geophysics and

Geosystems, vol. 11, no. 10, pp. 1-28, 2010.

[2] S. M. Jowitt et al. “Quantifying the release of base metals from source rocks for

volcanogenic massive sulfide deposits: Effects of protolith composition and alteration

mineralogy”, Journal of Geochemical Exploration, vol. 118, pp. 47-59, 2012.

[3] F. E. Jenner and H. S. O'Neill. “Analysis of 60 elements in 616 ocean floor basaltic

glasses”, Geochemistry Geophysics and Geosystems, vol. 13, no. 2, pp. 1-11, 2012.

[4] M. Harris. “The accretion of lower oceanic crust”, Unpublished Doctoral Thesis,

University of Southampton, School of Ocean and Earth Science, pp. 294, 2011.

68

A PhD Study on the Controls of Au-As Mineralization at the Lagares

Project, Northern Portugal

Cláudio Pauloa, Alexandre Limaa, and Daniel Jamesb

a Departamento de Geologia, ambiente e ordenamento de território da Faculdade de Ciências,

Universidade do Porto, Portugal, up200604829@fc.up.pt, b Medgold Resources Corp, Canada.

The Variscan orogeny of northwest Iberia, and particularly in northern Portugal, has a dominant

control upon the regional metallogenesis of the gold-arsenic prospects of the region. These gold-

arsenic prospects are predominantly structurally-controlled and associated with silicification and

sulphide mineralization.

The Lagares Au-As project is located in northern Portugal close to the town of Sobreira.

Geologically, the prospect is located at the contact of a major anticlinal structure of Silurian

sediments, called the Valongo Anticline, and the Hercynian-aged Castelo de Paiva granite. Key

prospects within the project area are Castromil and Serra da Quinta, which are the focus of

current exploration work, and have mineralization extensive over a total strike length of 4 km.

The strike of the mineralization is northwest, dipping to the northeast, and broadly parallel to the

axial plane. The NW-trending contact between the Silurian sediments and Hercynian granites is

both an intrusive contact and has been subsequently normal faulted with the NE-block being

downthrown and subsequently cut by NE-trending faults.

The previous geological model for the Castromil and Serra da Quinta was one of mineralization

forming under a compressive regime and associated with high-angle reserve. However, recent

work undertaken by Medgold, [1,2] have identified the dominant control on mineralization is

formed under normal faulting conditions. Furthermore, the recent identification of the NE-

trending faults in the region, which intersect the dominant NW-trending faults perpendicularly,

may be generating significantly increased mineralized thicknesses and grades.

The aims of this new PhD study, undertaken in collaboration between the University of Porto and

Medgold Resources Corp., is to better understand the gold-arsenic metallogensis at the Lagares

project. Particular focus will be made to the structural controls upon mineralization, and the

implications for regional exploration, aiming to identify and delineate various vein orientations,

dilation, and possible plunging ore shoots. The study will also undertake detailed field analysis

and analytical geochemical and petrographical studies. Fluid inclusion studies of the different

mineral phases will be undertaken and combined with geochronological dating of both the

different mineral phases and the granitoid host rocks.

References

[1] D. Mckenzie, and D. Craw. “Controls on gold mineralization at the Valongo, Vila de Rei,

Salguerio, Castromil, Serra da Quinta and Limarinho prospects, northern Portugal”,

Internal Report for Medgold Resources Corp., June 2014.

[2] J. K. Mortensen. “Investigations of gold mineralization in the Lagares, Balazar and

Castelo de Paiva concessions, northern Portugal: results and recommendations for future

exploration,” Internal Report for Medgold Resources Corp., August 2013.

69

The Nature and Origin of Hydrothermal Gold Mineralisation at the Rex Pit,

Damang Mine, Ghana

Rebecca J Perkinsa,b, Laurence J Robba, and Matthew Crawfordc

a Department of Earth Sciences, University of Oxford, UK, rebecca.perkins@bristol.ac.uk,

b School of Earth Sciences, University of Bristol, UK, c GoldFields, Australia.

The Ashanti Belt in southern Ghana is a world-class gold producing province with an extensive

history of mining dating back to pre-colonial times. Situated within the Ashanti Belt is the

regionally unique Damang orogenic gold deposit. ‘Typical’ Ashanti Belt lode-gold orebodies are

hosted in deep crustal shear zones at the contact between weakly metamorphosed Upper Birimian

bimodal lava and pyroclastic interbeds and Lower Birimian conformable volcaniclastic and

argillaceous sedimentary units [1]. However, in the Damang region, mineralization is restricted to

the overlying, syn-Eburnean Tarkwaian metasedimentary sucession with no known

mineralization occurring in the local Birimian Group.

The Damang pits are clustered in the hinge of a NE-striking anticline. The focus of this study, the

Rex pit, is a satellite deposit located 15 km along strike of the western limb of this structure. At

Rex, only the two lowermost units of the Tarkwaian Succession (the Kawere Group and the

Banket Sandstone), outcrop at the surface. Both units show well-preserved original sedimentary

features with a greenschist facies metamorphic overprint characterized by chlorite and ankerite

porphyroblasts. The complex structural history of the Damang region can be resolved at Rex

where sequential folding and thrusting followed by cross-cutting sinistral strike-slip faulting can

be related to the well-defined D2-D4 events of the Eburnean Orogeny [2].

The D3-related Kawere thrust contact between the Banket Sandstone and the Kaware Group

acted as a hydrothermal fluid pathway with gold mineralization and alteration confined to the

Banket Sandstone in the footwall and decreasing in intensity with distance from the fault. Wall

rock sulphidation is pervasive throughout the Banket Sandstone and increases in intensity

associated with high gold grade, where it often replaces detrital magnetite. Using isocon analysis

[3], the five additional alteration styles observed can be related to three metasomatic events –

chloritic, carbonate and haematitic. Orogenic gold is strongly coupled with the second

metasomatic event showing isochemical carbonate alteration associated with a sheared, fault

parallel to sub-parallel vein set showing strong internal foliations of calcite and quartz.

A strong spatial correlation between the thrust faulting, a quartz calcite vein array, carbonate

alteration and gold grade suggests a genetic link. Interaction between a reducing, H2O-CO2 rich

fluid and the oxidized, magnetite-bearing, sandstone host rock produced carbonate alteration

selvages proximal to fault controlled veins and widespread wallrock sulphidation. Reduction of

the magnetite within the host sandstone formed pyrite destabilizing the [Au+][HS-]2- complex in

solution leading to Au precipitation. The two further barren metasomatic events (chloritic and

haematitic) had little impact on the orogenic gold mineralization.

References

[1] T. Oberthür et al. “Age constraints on gold mineralization and Palaeoproterozoic crustal

evolution in the Ashanti Belt of southern Ghana”, Precambrian Research, vol. 89, no. 3, pp.

129-143, 1998.

[2] J. P. Pigois et al. “Age constraints on Tarkwaian Palaeoplacer and lode-gold formation

in the Tarkwa-Damang district, SW Ghana”, Mineralium Deposita, vol. 38, no. 6, pp. 695-

714, 2003.

[3] R. Gresens. “Composition-volume relationship of metasomatism”, Chemical Geology,

vol. 2, pp. 47-65, 1967.

70

Controls on the Rare Earth Element Enrichment at the Serra Verde Ion

Adsorption REE Deposit, Goias, Brazil

Carmen E Pinto-Warda, Richard J Herringtonb, and Jamie J Wilkinsonb

a Dept. of Earth Science and Engineering, Imperial College London, UK, carmen.pinto-

ward08@imperial.ac.uk, b Dept. of Earth Sciences, Natural History Museum, UK.

Ion-adsorption rare earth element (REE) deposits are weathered granites that contain

economically exploitable REE-bearing clays. The REE enriched weathering profiles result from

the breakdown of feldspars into clays and the dissolution of REE-bearing minerals. The deposits

are typically low grade at 0.05-0.2 % REE2O3 [1], but are enriched in the heavy rare earth

elements (HREE), they have low radioactive element contents, and have low mining and

processing costs [2]. To date ion-adsorption REE deposit have only been mined in China and are

currently the primary source of HREE [3].

The Serra Verde REE deposit in the Goias state, Brazil is one of the few ion-adsorption REE

deposits that has been found outside China. The deposit was discovered a few years ago and

operations are due to start in 2017 [4]. The Serra Verde REE deposit is a 10 – 35 m thick

weathering profile that developed over a Proterozoic age tin-bearing granite called Serra

Dourada. The weathering profile is divided into four main horizons; ferruginous zone, the mottled

zone, saprolite, and saprock, and is covered by a thin layer of ferricrete soil. The saprolite

horizon, which varies in thickness from 0.5 m to 6 m, contains the enriched REE-bearing clays.

Due to the limited amount of work published on Chinese deposits and the lack of economic ion-

adsorption REE type deposits found outside China, the controls and the processes involved in the

formation of this type of deposit are not well understood. The Serra Verde REE deposit therefore

offers a unique opportunity to investigate this type of REE deposit and gain a better insight into

their formation.

This study aims to investigate and develop a model for the introduction, enrichment and

mineralogical residence of the REEs in the Serra Verde ion-adsorption REE deposit. The Serra

Verde deposit will be studied by firstly mapping the geology and weathering zones of deposit

area and secondly by carrying out detailed chemical, petrographic and mineral analysis on

samples at the Natural History Museum.

Detailed core logging and sampling of the weathering profile have now been completed. This

poster presents the main characteristics of the weathering profile that developed over the Serra

Dourada granite and outlines the aims and research methods of this study.

References

[1] Wu et al. “Rare earth deposits in China”, In Rare Earth Minerals: Chemistry origin

and ore deposits (Eds A. P. Jones, F. Wall, and C. T. Williams), The Mineralogical Society

Series, vol. 7, Chapman and Hall, 1996.

[2] Y. Kanazawa, and M. Kamitani. “Rare earth minerals and resources in the world”,

Journal of Alloys and Compounds, vol. 408-412, pp. 1339-1343, 2006.

[3] R. Chi, and J. Tian. “Weathered Crust Elution-Deposited Rare Earth Ores”, Nova Science

Publisher, New York, pp. 286, 2008.

[4] http://www.minesandmoney.com/hongkong/serra-verde/

71

Regional Carbonate Alteration in the Eastern Desert of Egypt: Fluid Sources

and Implications for Formation of Gold Deposits

Iain K Pitcairna, Ahmad Boskabadia,e, Curt Bromana, Damon AH Teagleb, Matthew J Cooperb, Adrian

Boycec, Mokhles Azerd, and Robert J Sterne

a Department of Geological Sciences, Stockholm University, Sweden, iain.pitcairn@geo.su.se, b National

Oceanography Centre Southampton, University of Southampton, UK, c Scottish Universities Environmental

Research Centre, UK, d Geology Department, National Research Centre, Egypt, e Geosciences Department,

University of Texas at Dallas, USA.

The migration of carbonate-rich solutions was common during deformation and metamorphism of

the Arabian-Nubian Shield (ANS), forming veins and dykes, and causing diffuse and pervasive

carbonation of a wide range of basement rocks (1). Pervasive carbonate alteration focused along

faults and shear zones is extremely abundant in ultramafic and mafic components of the ophiolitic

sequences of the Central Eastern Desert (CED), Egypt, and is spatially associated with orogenic

gold deposits. Despite the abundance of this alteration and its significance for understanding the

formation of the gold deposits, there have been few isotopic investigations into the source of

fluids that caused the alteration. In this study we investigate a sequence of carbonated ultramafic

rocks surrounding the Meatiq core complex (MCC) in the CED of Egypt. We report C, O and Sr

isotope compositions of carbonated serpentinites and of pure carbonate veins in order to constrain

the origin of the carbonating fluid. We also report trace metal concentrations from two types of

serpentinites, and fluid inclusion compositions from carbonate veins.

The isotopic composition of the magnesite veins show a mantle signature with 13Cpdb and 18OSMOW

ranging -6.8 to -8.1‰ and 6.4 to 10.5‰ respectively, and age-corrected 87Sr/86Sr ratios ranging

0.7028 to 0.7034. Carbonate-altered serpentinites have isotopic composition that plot close to

mantle compositions but indicate mixing with a surficial fluid. The data indicate that large fluxes

of mantle-derived CO2-rich fluid through the CED basement rocks occurred during the

Neoproterozoic. Trace metal concentrations are systematically lower in the intensively

carbonated antigorite serpentinites compared to the lesser-carbonated lizardite serpentinites

suggesting these elements have been remobilized during transition of lizardite to antigorite.

Carbonate veins contain abundant carbonic (CO2±CH4±N2) and aqueous-carbonic (H2O-NaCl-

CO2±CH4±N2) low salinity fluid inclusions. Fluid inclusions and isotopic compositions from

gold-rich vein deposits in the CED show similarities to those reported from this study (2) and it is

possible that the CO2-rich mantle fluid that leached metals during carbonation also formed the

gold-rich veins.

References

[1] R. J. Stern, and C.J. Gwinn. “Origin of late Precambrian intrusive carbonates, Eastern

Desert of Egypt and Sudan: C, O and Sr isotopic evidence”, Precambrian Research, vol. 46,

pp. 259-272, 1990.

[2] B. Zoheir, and R. Moritz. “Fluid evolution in the El-Sid gold deposit, Eastern Desert,

Egypt”, Journal of the Geological Society, London, doi 10.1144/SP402.3, 2014.

72

Geochemical and Mineralogical Data across the Platinova Reef and its

Implications for the Genesis of Discrete, Offset, Precious Metal-Enriched

Horizons

Richard F Prassera, David A Holwellb, and Shaun D Grahamc

a Department of Geology, University of Leicester, UK, richardprasser@btinternet.com,

b Department of Geology, University of Leicester, UK, c Carl Zeiss Microscopy Ltd., Cambridge, UK.

The Platinova Reef is a series of distinct, stratiform Au and PGE-enriched horizons located

within the 56 Ma tholeiitic layered Skaergaard intrusion in the Kangerlussuaq region of east

Greenland. The intrusion stretches 11 km north to south, 8 km east to west and is around 3.5 km

thick, and is an example of a magma chamber which has undergone fractional crystallisation in an

entirely closed system.

The Platinova Reef is an example of a rare sub-class of magmatic Ni-Cu-PGE sulfide deposits,

formed from late stage sulfide saturation triggered by prolonged fractional crystallisation of the

magma, and often linked to magnetite crystallisation. They can be classified on four main features

[1]: the sulfide phase boundary lies stratigraphically above the magnetite phase boundary; the

sulfide assemblage is Cu rich and Fe and Ni poor; precious metals are found at or beneath the

major sulfide phase boundary; and precious metals distributions are complex, forming discrete,

offset subzones in a specific stratigraphic order.

The Platinova Reef is made up of a number of zones based on its relative metal content [2]: a

basal Subzone, where precious metal grades increase; a Pd zone, with Pd >1 g/t over a few

metres; an Intermediate zone with Pd 0.1 – 1 g/t; a very thin Au zone with Au >1 g/t over 1 m;

and an overlying Cu zone, where sulfide content increases but precious metal contents drop off.

The processes involved in producing the mineralisation, and the characteristic offsets and abrupt

change in sulfide volume and tenor, have been subject to many contrasting models, including

distribution of metals by fluids [3], fractionation of sulfide liquids [4] and dissolution of sulfides

[2]. Notwithstanding this debate, the Pd zone is stratigraphically controlled and is present

throughout the entire intrusion in the same stratigraphic unit (unlike the Au zone).

High resolution (20 cm scale) geochemical data across the mineralised zone show that the Pd

zone has an enrichment in V and TiO2 (proxies for magnetite and ilmenite) at its base. This

increase in bulk Fe-Ti oxide coincides with the major onset of sulfide generation and Pd

enrichment. This would suggest that the removal of Fe-Ti oxide from the melt at this level caused

sulfide saturation and the onset of mineralisation by removing FeO from the magma, thus

reducing the S carrying capacity of the melt, and also by reducing sulphate to sulfide. Therefore,

Fe-Ti oxide formation is a critical process in the development of late stage stratiform offset style

reefs.

References

[1] M. D. Prendergast. “Layering and Precious Metals Mineralization in the Rincón del

Tigre Complex, Eastern Bolivia”, Economic Geology, vol. 95, pp.113-130, 2000.

[2] D. A. Holwell, and R. R. Keays. “The Formation of Low-Volume, High-Tenor Magmatic

PGE-Au Sulfide Mineralization in Closed Systems: Evidence from Precious and Base Metal

Geochemistry of the Platinova Reef, Skaergaard Intrusion, East Greenland”, Economic

Geology, vol. 109, pp. 387-406, 2014.

[3] J. C. Ø. Andersen. “Postmagmatic sulphur loss in the Skaergaard Intrusion:

Implications for the formation of the Platinova Reef”, Lithos, vol. 92, pp. 198-221, 2006.

[4] J. C. Ø. Andersen et al. “The Triple Group and the Platinova Gold and Palladium Reefs

in the Skaergaard Intrusion: Stratigraphic and Petrographic Relations”, Economic Geology,

vol. 93, pp. 488-509, 1998.

73

Chlorine Partitioning in Magmas and the Formation of Porphyries

Simon Richardsa, and Daniel J Smitha

a Department of Geology, University of Leicester, LE1 7RH, UK, sjr60@le.ac.uk.

Ore forming and volcanic processes are controlled by the behaviour of water, with the enhanced

fertility of arc magmas being a direct result of their high water contents [1]. Chlorine is an

important ligand for metals such as Cu and Au and is assumed to strongly partition into an

aqueous phase upon exsolution from magmas [2]. Much research has been conducted on the

behaviour of chlorine to this end [3] and the majority of studies have concentrated on crustal

pressures of 200 MPa: within the approximate pressure/depth interval of porphyry copper deposit

emplacement [4], and the assumed exsolution pressure of a magma with “typical” water contents

of ~ 5 wt% H2O [5]. However, recent work has demonstrated that the dissolved water contents of

arc magmas may approach 15–20 wt% H2O [6], and that exsolution of volatiles may occur much

deeper in the crust, at greater pressures. The potential impact of earlier and longer volatile release

on chlorine (and metal) budgets of magmatic-hydrothermal systems have not been well explored

previously.

This research project aims to gain insight into the behaviour of chlorine at depth in the crust to

better understand ore-forming arc magmas. The assumption that chlorine will partition strongly

into an aqueous phase upon exsolution from magma will be tested by compiling melt/fluid

partition coefficients of chlorine, with the ultimate aim to determine whether chlorine can be used

as a proxy that records volatile exsolution. Numerical models of chlorine partitioning between

magma and volatile phase will be created with fundamental equations that describe fractionation,

water solubility and element partitioning to produce ‘chlorine curves’ for different initial H2O and

magma compositions. The theoretical models will be compared and contrasted to the real world

data (e.g. compilations of melt inclusions) to determine whether ore forming systems are

impacted by different degassing regimes and / or initial volatile chemistry.

References

[1] J. P. Richards. “High Sr/Y magmas and porphyry Cu+/- Mo +/- Au deposits: Just add

water”, Economic Geology, vol. 106, pp. 1075-1081, 2011.

[2] J. D. Webster, and J. R. Holloway. “Experimental constraints on the partitioning of Cl

between topaz and rhyolite melt and H2O and H2O and CO2 fluids: New implications for

granitic differentiation and ore deposition”, Geochemica et Cosmochimica Acta, Vol. 52, pp.

2091-2105, 1988.

[3] D. R. Baker, and M. Alletti. “Fluid saturation and volatile partitioning between melts

and hydrous fluids in crustal magmatic systems: The contribution of experimental

measurements and solubility models”, Earth Science Reviews, vol. 114, pp. 298-324, 2012.

[4] R. H. Sillitoe. “Porphyry copper systems”, Economic Geology, vol. 105, pp. 3-41, 2010.

[5] G. Moore et al. “An empirical model for the solubility of H2O in magmas to 3 kilobars”,

American Mineralogist, vol. 83, pp. 36-42, 1998.

[6] C. Annen et al. “The genesis of intermediate and silicic magmas in deep crustal hot

zones”, Journal of Petrology, vol. 47, pp. 505-539, 2006.

74

Source and Role of Extrinsic Hydrocarbons at the MVT Pb-Zn Laisvall

Deposit, Sweden

Nicolas J Saintilana, Jorge E Spangenbergb, Cyril Chelle-Michoua, Massimo Chiaradiaa, Michael B

Stephensc,d, and Lluís Fontbotéa

a Section of Earth and Environmental Sciences, University of Geneva, Switzerland,

nicolas.saintilan@unige.ch, b Institute of Earth Surface Dynamics, University of Lausanne, Switzerland, c Geological Survey of Sweden, Sweden, dDivision of Geosciences, Luleå University of Technology, Sweden.

Mineralizing fluids forming Mississippi Valley-type (MVT) deposits are widely accepted to be

mainly derived from oil-field brines in sedimentary basins whilst lead isotope data suggest

various basement rocks and basal detrital rocks as potential metal sources [1]. Organic

compounds in sedimentary sequences hosting MVT deposits play a major role in sulphide

precipitation by providing reduced sulphur through thermochemical sulphate reduction [2]. In

addition, the role of organic matter as minor source of metals has been suggested, although direct

evidence for metals in MVT ores being partly derived from organic-rich rocks remains

unsatisfactory [3,4,]. A detailed organic geochemistry study at the world-class Mississippi

Valley-Type sandstone-hosted Pb-Zn Laisvall deposit and organic-rich shale of the upper

Cambrian‒Lower Ordovician Alum Shale Formation suggests that extrinsic organic compounds

acted as a reductant and contributed to the metal endowment of the deposit.

The chromatographic and molecular signature of mineralized and barren sandstone and organic-

rich shale samples indicates that: i) hydrocarbons in mineralized sandstone are, at least

predominantly, not indigenous; and ii) organic-rich shale is the source rock for these extrinsic

hydrocarbons. Accumulated evidence suggests that thermochemical sulphate reduction via these

extrinsic hydrocarbons is the main source of reduced sulphur in mineralisation at Laisvall. These

results, combined with a reassessment of the Pb isotope geochemistry of the deposit and potential

source rocks (Chelle-Michou et al., this conference), indicate that the hydrocarbon source rocks,

in addition, contributed with a subordinate part to the metal endowment at Laisvall. Extractable

metal-organic complexes in the asphaltene and NSO-fraction of oil and bitumen may supply

significant amount of metal ions (e.g., Pb2+, Zn2+) to ore fluids [e.g., 4,5,6]. Indeed, highly water-

soluble carboxylate (e.g., acetate) produced from metal-catalyzed reactions during kerogen

maturation are rapidly transported in ore-forming fluids [5]. It is proposed that Pb-acetate

complexes in aqueous fluids, migrating with immiscible hydrocarbon from upper

Cambrian‒Lower Ordovician organic-rich shale source rock into sedimentary traps in sandstone

palaeoaquifers, may explain the low-radiogenic Pb source identified at Laisvall.

References

[1] D. Leach et al. “Sediment-hosted Pb-Zn deposits: A global perspective”, Economic

Geology 100th Anniversary Volume, pp. 561-607, 2005.

[2] G. M. Anderson. “The mixing hypothesis and the origin of Mississippi Valley-type ore

deposits”, Economic Geology, vol. 103, no. 8, pp. 1683-1690, 2008.

[3] D. A. C. Manning, and A. P. Gize. “The role of organic matter in ore transport

processes”, In Organic Geochemistry, Principles and Applications (Eds. M. H. Engel, and S.

A. Macko), New York, Plenum Press, vol. 11, pp. 547-563, 1993.

[4] T. H. Giordano, and Y. K. Kharaka. “Organic ligand distribution and speciation in

sedimentary basin brines, diagenetic fluids and related ore solutions”, In Geofluids: Origin,

Migration and Evolution of Fluids in Sedimentary Basins (Ed. J. Parnell), Geological

Society, London, Special Publication, vol. 78, pp. 175-202, 1994.

[5] J. Parnell. “Metal enrichments in solid bitumens: A review”, Mineralium Deposita, vol.

23, pp. 191-199, 1988.

[6] P. F. Greenwood et al. “Organic geochemistry and mineralogy. I. Characterization of

organic matter associated with metal deposits”, Ore Geology Reviews, vol. 50, pp. 1-27, 2013.

75

Stable Isotopes (C-O) from the Supergene Nonsulfide Zn Prospect of Reef

Ridge, Alaska

Licia Santoroa, Maria Bonia, and Michael Joachimskib

a Dipartimento Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli, Italy,

licia.santoro@unina.it, b GeoZentrum NordBayern, University of Erlangen-Nuremberg, Germany.

The Reef Ridge (RR) prospect is a typical supergene "nonsulfide" zinc mineralization, located in

the Yukon-Koyukuk region of west central Alaska (USA), hosted in Lower-Middle Devonian

shallow water dolomites. The useful mineralization, consisting of Zn carbonates (smithsonite)

mixed with Fe-(hydr)oxides (goethite and hematite) and remnants of sulfides, commonly occurs

in the oxidation zone.

A geochemical study on the stable C-O isotopes of RR smithsonite and dolomite has been carried

out, in order to define the genetic constrains of the supergene mineralization. In this study the

results of the isotopic analyses are briefly summarized, in order to re-consider the "traditional"

interpretation on the origin of Zn nonsulfide deposit in warm, semi-arid environments.

Seven concretionary smithsonite and thirteen dolomite fragments were separated by mechanical

hand picking, and analyzed at the University of Erlangen-Nuremberg (Germany) using mass

spectrometry. Carbon and oxygen isotope values are reported in ‰ relative to V-PDB and V-

SMOW respectively, by assigning a δ13C value of +1.95‰ and a δ18O value of -2.20‰ to

standard NBS19. Reproducibility was checked by replicate analysis of laboratory standards (>±

0.07 ‰ 1σ for both C and O). Oxygen isotope values of dolomite and smithsonite were corrected

using the equation described by [1]. The results show that the δ18O values of the host dolomite are

between 25.5 and 28.1‰ V-SMOW, whereas the δ13C ratios are relatively constant in the range

from 0.3‰ to 1.6‰. The δ18O values of smithsonite are comprised between 19.1 and 21.9‰ V-

SMOW. On the contrary, the δ13C values are more variable, ranging between –0.7 and 2.1‰.

The δ18O and δ13C values of dolomite have the Middle Devonian seawater signature, whereas

those of RR smithsonite are quite different from the values of most supergene smithsonite

worldwide. The majority of the δ13C values for smithsonite are similar to those of the host rock,

suggesting that the prevailing C source was in the host carbonates, with limited contribution from

organic carbon; whereas the δ18O values suggest fluids of meteoric origin. Their strong depletion

in δ18O can be considered normal at sub-arctic/arctic latitudes where RR is located. Using the

oxygen isotope fractionation equation between smithsonite and water [1], the formation

temperature of this Zn carbonate can be approximated. Using the δ18O values of meteoric waters

in the vadose zone (~ -14 and ~ -15‰), which are precipitated during the summer season (we

hypothesized that no precipitation can happen at winter temperatures), the calculated precipitation

temperatures would be in the range of 5 to 10° C.

There are two main hypothesis for the age of smithsonite precipitation. Assuming a climate with

temperatures similar to today, Zn carbonate could have precipitated from cold water during the

summer in Late Tertiary. Alternatively, the supergene nonsulfides may have formed from local

meteoric waters at very low temperatures, possibly related to cold/humid episodes during the

warmer Pliocene or Pleistocene-Holocene.. The “traditional” interpretation of Zn nonsulfide

deposit formation in warm (semi-arid?) conditions should be questioned where other climate

zones are indicated. This applies not only to the nonsulfide prospects in Alaska, but also to other

“oxide” deposits at high latitudes.

References

[1] H. A. Gilg et al. “Stable isotope geochemistry of 767 carbonate minerals in supergene

oxidation zones of Zn-Pb deposits”, Ore Geology Reviews, vol. 33, pp. 117-133, 2008.

76

Portable XRF for Mineral Exploration Geochemistry in Till

Pertti Saralaa, and Todd Houlahanb

a Senior Scientist, Geological Survey of Finland, Finland, pertti.sarala@gtk.fi,

b Director, International Mining Group, Olympus Scientific Solutions Americas, UK.

Surficial geology, till geochemistry and heavy mineral studies have been used as practical

exploration tools in glaciated terrains for nearly one hundred years. Till as a sampling

media is very useful due to its glaciogenic nature and being a mixture of fresh bedrock,

pre-glacial weathered bedrock and older sediments. Lithological and geochemical

characteristics of the secondary dispersed till are an effective way to estimate transport

distances and deposition processes of mineralised material in glaciogenic formations.

New sampling techniques and analysis methods for till geochemical exploration are

studied in the Geological Survey of Finland, Finland (GTK). The purpose is to find new

applications for regional and/or target-scale exploration by finding new solutions for

surficial exploration and by developing effective, environmentally-friendly sampling

techniques and analysis methods in the sensitive Arctic and Subarctic regions. An aim is

to get a very low environmental impact due to exploration activity in the areas of thick

glaciogenic overburden, peat-cover and/or reservation. At the same time, the focus is

decreasing analytical costs and increasing sample efficiency. New tested methods include

for instance portable X-Ray Fluorescence (pXRF) supported by laboratory XRF

measurements and traditional partial leach geochemistry.

For the last few years the GTK have been applying modern pXRF analyzers on a range of

projects in Finland. The detection limits of these analysers are now low enough (ppm

scale) for a large group of elements to make them very effective for regional exploration

work. Portable equipment is light-weight and easy to take in the field. Real-time analytics

provide quick directing of the till geochemical sampling and focusing into most potential

exploration targets within the study area. Several exploration examples from northern

Finland prove the methods suitable and effective for exploration purposes in glaciated

terrains.

Based on the practical experience using Olympus Delta 6000 pXRF, correlations between

pXRF analyzer, laboratory XRF and even ICP-AES (based on aqua regia leaching)

analyses are mostly good or moderate for a large group of elements. Although the Delta

6000 pXRF results are excellent and highly accurate for the base metals, giving

possibility for the absolute value measurements, relative values and trends are mostly

worth considering. This poster will outline the strengths and weaknesses observed by the

GTK using portable XRF over the last few years.

77

Regional Geochemistry and Characteristics of Gold Mineralisation in

Castromil and Serra da Quinta, Northern Portugal

Robert Selwyna, Gawen RT Jenkina, and Daniel Jamesb

a Department of Geology, University of Leicester, LE1 7RH, UK, robertselwyn@live.co.uk, b Medgold Resources Corp, Portugal.

The Central Iberian Zone of northwest Iberia contains several orogenic gold deposits and

prospects including Castromil and Serra da Quinta. The northwestern part of Portugal is a

particularly important Variscan metallogenic province for gold that has been extensively mined

since Roman and Pre-Roman times [1] yet still poorly understood.

Castromil and Serra da Quinta are principle prospects within the Lagares licence area located 30

km east of Porto and are both structurally-controlled intrusion-hosted orogenic gold prospects.

The Lagares project is located on the eastern flank of the NW-plunging Valongo anticline [2] and

lies within a mineralisation belt extending over a 4 km strike length. Mineralisation is mostly

confined to the granite in the hanging wall of the NW trending Railway Fault. The fault runs

along the contact of Silurian metasediments in Castromil (consisting of greywacke, graphitic

schist and mudstones) and the Variscan Castelo de Paiva porphyritic granite [1] however this

contact is gradually lost in Serra da Quinta and becomes a granite/granite contact.

Mineralisation at Castromil has been exploited by the Romans and traces of old workings are still

seen today by waste piles and various adits. Soil geochemistry, channel samples, trenching and

rock chip samples have been collected by Medgold Resources Corp across both prospects

combined with over 4700 m of diamond drill holes. Soil samples reveal up to 33.5 g/t Au which

has been reflected in recent channel samples in the mineralisation beneath. Other channel samples

in iron-oxide boxwork structures contain 4.60 m at 36.17 g/t Au. Mortensen et al. (2013) [3]

observe that metasediments in close proximity to the Railway Fault contain considerable gold and

have been previously dismissed in earlier literature. An initial observation made from fieldwork is

that on a regional scale, Castromil is dominanly pyrite-rich whilst Serra da Quinta is dominantly

arsenopyrite-rich.

This research aims to compile regional geochemistry data across both prospects to understand

mineral relationships between Au, Ag, As and Sb and how the changes in regional soil

geochemistry relate to geochemistry of oxides and leached elements between the two prospects.

To answer the aims of this research, these samples will be subjected to detailed optical

mineralogy and petrography. Samples with good textural information will be scanned by SEM to

understand mineral relationships and compositions of the oxides. Other samples will be futher

analysed by CT scanning to observe 3D mineralisation and lithological relationships in the

metasediment. Geochemical results from new channel samples and trenching will be used to

examine how geochemistry relates to mineralisation.

References

[1] F. Vallance et al. “Fluid-rock interactions and the role of late Hercynian aplite intrusion

in the genesis of Castromil gold deposit, northern Portugal”, Chemical Geology, vol. 194, pp.

201-224, 2003.

[2] J. K. Mortensen et al. “Investigations of Au, Sb and Pb-Zn-Ag mineralisation in the

Valongo, Castelo de Paiva and Ponte da Barca concessions, northern Portugal”, Internal

Report for Medgold, September 2013.

[3] J. K. Mortensen et al. “Investigations of gold mineralisation in the Lagares, Balazar and

Castelo de Paiva concessions, northern Portugal: results and recommendations for future

exploration,” Internal Report for Medgold, August 2013.

78

Magnetite Crystallisation as a Control of Mineral-Melt Partitioning of

Divalent Cations

Robert Sievwrighta,b, and Jamie Wilkinsona,b

a Dept of Earth Science and Engineering, Imperial College London, United Kingdom,

r.sievwright13@imperial.ac.uk, b Dept of Earth Sciences, Natural History Museum, United Kingdom.

There is increasing interest in the use of magnetite as a geochemical proxy to interpret ore

forming processes in magmatic systems e.g. [1]; [2]. However, in order to utilise magnetite as a

petrogenetic indicator, a comprehensive understanding of how different factors affect magnetite

chemistry is required. Magnetite/melt partitioning of a large range of elements has been

investigated experimentally as a function of oxygen fugacity (fO2) and temperature (T) in an

andesitic bulk-chemical composition. In this bulk system, at constant T, there are strong increases

in the magnetite-melt partitioning of the divalent cations, Mg2+ and Mn2+, with increasing fO2

between 0 and 3 log units above the fayalite-magnetite-quartz (FMQ) buffer. At first sight, this

could be viewed as related to changing redox condition; however, we suggest this is actually

controlled by a coupling between magnetite crystallisation and melt structure.

At constant T, with increasing fO2 the proportion of magnetite and plagioclase increases, whereas

the melt proportion decreases. The increased crystallisation of magnetite notably results in a

decrease in FeOmelt, which causes a silica enrichment in the residual liquid. This leads to an

increase in the degree of melt polymerisation at a given temperature. It has been suggested that

more polymerised melts contain less potential sites onto which divalent cations can partition [3].

Consequently, between FMQ < fO2 < FMQ + 3, increasing the fO2 drives an increase in the

degree of melt polymerisation into a critical range where small increases in polymerisation result

in large increases in the mineral-melt partitioning of divalent cations. In an andesitic bulk system,

the enhanced crystallisation of magnetite with increasing fO2, and associated repercussions on

melt structure, will have significant implications for mineral-melt partitioning, phase relations

and the physical properties of melts, and should therefore be considered when studying natural

andesitic systems.

References

[1] S. A. S. Dare et al. “Variation in trace element content of magnetite crystallized from a

fractionating sulfide liquid, Sudbury, Canada: Implications for provenance

discrimination”, Geochimica et Cosmochimica Acta, vol. 88, pp. 27-50, 2012.

[2] P. Nadoll et al. “Geochemistry of magnetite from porphyry Cu and skarn deposits in the

southwestern United States”, Mineralium Deposita, vol. 10, pp. 1-23, 2014.

[3] M. J. Toplis, and A. Corgne. “An experimental study of element partitioning between

magnetite, clinopyroxene and iron-bearing silicate liquids with particular emphasis on

vanadium”, Contributions to Mineralogy and Petrology, vol. 144, no. 1, pp. 22-37, 2002.

79

Lonmin Plc Exploration in Northern Ireland - The Contribution of Mineral

Exploration to New Observations in Regional Geology

Dermot Smyth

Lonmin Plc., 4, Grosvenor Place, London, SW1X 7YL, dermot.smyth@lonmin.com

Lonmin Plc has explored for PGE in Northern Ireland since 2008. Our focus in this region was

initiated by the release of new geochemical and geophysical datasets for Northern Ireland as a

consequence of the Tellus Project. Our exploration strategy has primarily sought to define

orthomagmatic PGE targets with subordinate gold and base metals.

The completion of the largest airborne Full Tensor Gravity (FTG) survey in the UK and Ireland

has provided greater detail and defined new basement structures and ‘blind’ mafic intrusions in

the Dalradian stratigraphy. Geophysical, geochemical and geological fieldwork observations in

the Antrim Lava Group (ALG) include the discovery that many of the lavas comprising the ALG

are relatively depleted in palladium which has implications for accumulations of PGM in magmas

prior to extrusion. Field studies have recognised magmatic conduit systems cutting through the

Mesozoic and Dalradian stratigraphy to facilitate extrusion of the Antrim Lava Group. Gold-

bearing mineralisation has been intersected in two boreholes, one of which has characteristics

similar to Dalradian gold deposits found in the British Isles.

This presentation will outline and document these new observations which offer insight into the

understanding of the geology of Northern Ireland and present opportunities for further research

work.

80

Volcanic Processes in the Formation Porphyry Copper Deposits

R Stephen J Sparksa, Jon Blundya, Frances Coopera, Amy K Gilmera, Alison Rusta, Tom Sheldrake, and

Brian Tattitcha

a School of Earth Sciences, University of Bristol, UK

The hypothesis that porphyry copper deposits are linked to active volcanoes is examined in the

light of recent advances in understanding silicic volcanism in arcs. PCDs are commonly

associated with silicic and intermediate composition dykes and plugs, which can be explained as

volcanic conduits related to lava dome and explosive activity. Models of PCD’s commonly

envisage steady degassing of large silicic magma chambers, in recognition that the small

porphyry intrusions cannot provide the very large volumes of magmatic fluids needed to explain

the localised enrichments in metal sulphides. However, evidence from well-documented active

arc volcanoes indicates that they are highly unsteady systems. Arc volcanoes commonly alternate

between very long periods of dormancy (typically > 103 to 105 years) and short intense bursts of

activity (typically 1 to 103 years) when evolved volatile-rich magmas are transferred from the

lower and upper crust to form ephemeral magma chambers. The short periods are associated with

volcanic activity characterised by cyclic dome growth and explosions. There is large variation of

the flux of magma and volatiles, but these fluxes can be de-coupled. There are examples of arc

volcanoes where magma eruption and volatiles are well correlated, cases where volatiles degas

between cyclic episodes of dome growth and explosions, and cases where there is persistent

magmatic degassing without eruption of magma. The compositions of the magmatic volatiles

reflect associated variations in depths of degassing. During the short periods of volcanic activity

the magmatic systems are disturbed and magma mixing is common as magmas derived from

different depth intermingle. Magmatic fluids typically have multiple sources, have different

degassing solubility-controlled behaviours of volatile species (notably H2O, H2S, SO2 and Cl)

critical to ore formation, and can decouple from parent magmas in space and time. The water

content of arc magmas is typically significantly higher than previously thought with values of 4%

typical of primitive arc basalts, while andesites and rhyolite melts derived from these basalts by

differentiation in the lower and middle crust may commonly exceed 10%. Thus degassing starts

much deeper than commonly supposed and this is supported by geophysical observations of deep

sources of SO2 (> 10 km). Magmatic volatiles can originate in three different ways: from shallow

degassing of silicic magma chambers; from ascent of deeper more mafic magmas during system

disturbances during eruptions; and by segregation and long term storage of deep poorly soluble

volatiles in the lower and middle crust. The release of these volatiles from all these sources can

occur on very different time scales and volatiles become decoupled from magma. We propose

that PCDs form during the short bursts of volcanic activity when sub-volcanic intrusions disrupt

the upper crust to enable magmatic fluids from different depths and sources to flow to the surface

and intermingle. This hypothesis is consistent with emerging evidence of multiple short-lived

bursts of mineralization in PCDs. Further we propose that porphyry copper mineralization is the

consequences of mixing between fluids derived from different depths and on different time

scales. Water and Cl-rich fluids are released from shallow silicic magma chambers and

accumulate in the overlying crust as copper-rich brines. Bursts of deeper S-rich magmatic fluids,

likely derived from mafic magmas, mix with these brines during volcanic activity.

81

Structural and Lithological Controls on Gold Mineralisation at the Wassa

Mine, Ghana

Rebecca C Strachana, David A Holwella, Christopher Bonsonb, and Mitchell S Waselc

a Department of Geology, University of Leicester, UK, rcs26@student.le.ac.uk,

b SRK Consulting, Cardiff, UK, c Golden Star Resources, Accra, Ghana.

Ghana’s Ashanti greenstone belt is host to a number of Paleoproterozoic hydrothermal

gold deposits, including Golden Star Resources’ Wassa Mine. Due to host rock lithology

and age, these deposits are distinct from paleoplacer deposit at Tarkwa, and shear zone

related fractures and fault fill of the world class deposit, Obuasi [1]. Wassa, however, is

unique in the Ashanti Belt, as it is the only deposit to be located in Birimian volcanics, on

the eastern limb of the regional Tarkwa Syncline [2]. Gold mineralisation at Wassa is

strongly controlled by regional and local deformation of the Birimian series.

In the region, the main lithologies are divided into two series; the Birimian and

Tarkwaian, 2266-2130 Ma and 2132-2107 Ma respectively [3]. The Birimian series

comprises: older metavolcanics; predominantly mafic and intermediate flows of the

Sefwi Group; and the slightly younger turbiditic and phyllitic metasediments sequences

of the Kumasi Group. The Tarkwaian Series is mostly conglomerate with interbedded

sandstones and phyllites, with some of the composite being dated as originating from the

Birimian

At least six deformation events have occurred in the region between 2187-1980 Ma,

extending from the Eoeburnean through to the Eburnean Orogeny [3]. Locally at Wassa

however, four of these can be observed at outcrop; D1 N-S shortening, D3 NW-SE

shortening, D4 NNW-SSE shortening [3] and D5 vertical shortening, with D2 absent.

Initial gold mineralisation is thought to have occurred during D1. This mineralisation

becomes remobilised in a later deformation event, thought to be D4; however, initial 3D

modelling of gold grade has shown high concentrations of gold along the hinges and

attenuated limbs of the refolded F3 folds. This would suggest that remobilisation of the

mineralisation occurred during D3 and that this is in fact the most important structural

control on mineralisation. From preliminary studies there is also an indication that more

than one mineralisation event may have occurred at Wassa.

References

[1] Y. Bourassa. “The Wassa gold mine: An Eoeburnean deposit within the Ashanti belt”,

Prospectors and Developers Association of Canada (PDAC) Convention, 2014.

[2] Y. Bourassa. “Geology Report Feasibility study”, Wexford Goldfields Limited, 2003.

[3] S. Perrouty et al. “Revised Eburnean geodynamic evolution of the gold-rich southern

Ashanti Belt, Ghana, with new field and geophysical evidence of pre-Tarkwaian

deformations”, Precambrian Research, vol. 204-205, pp. 12-3, 2012.

82

Geochemical and Mineralogical Characterisation and Ore Genesis of Red-

Bed Mineralisation at Gipsy Lane Brick Pit, Leicester

Adam B Taylora, Gawen RT Jenkina, and Hannah Townleyb

a Department of Geology, University of Leicester, United Kingdom, abt8@student.le.ac.uk,

b Natural England, United Kingdom.

Red-bed style mineralisation is observed at the present site of the disused Gipsy Lane brick pit in

Leicester. The site is the only SSSI within Leicester city, and comprises a 2.5 m stratigraphy of

Upper Triassic red/brown clays and evaporites of the Mercia Mudstone Group. The aim of this

research is to better understand the stratigraphy of the site and to quantify the mineralisation and

metal enrichments, with the end-goal to produce a geological model of ore formation. It is hoped

this will contribute to the understanding of basin evolution and fluid flow of this part of the UK

Triassic, with comparisons drawn to the mineralisation of the Cheshire Basin [1].

Previous study of the site has been limited: mineralisation was reported in the 1980s [2] and a

limited amount of geochemical analysis was conducted within the Department of Geology in the

1990s. These studies have shown enrichments in Cu, Co, Ni, As, Cr, Pb, V and U, and the

presence of malachite, azurite, erythrite, coffinite and lavendulan.

Current on-site observations show gypsum is the principal evaporite present, occurring in the

form of fine grained beds and nodules, and fibrous satin-spar veins. Associated directly with

gypsum beds and veins are areas of reduced green clay, small black spheroidal grains, amorphous

black residues and ore minerals (malachite and erythrite are observed, coffinite and lavendulan

are reported [2]). Reduction spots which are not associated with gypsum are also present within

the clay, many containing spherical black cores.

Observations of fibrous satin spar gypsum veins are important in deciphering the geological

history of the site. Thick (up to 30 mm) laterally continuous sub-horizontal veins with vertical

fibres are common, often present with rarer non-fibrous vertical veins. Thin veins (2-10 mm) are

also common but are less laterally continuous, and are commonly observed linking between

gypsum nodules. It is interpreted that these vein textures relate to fluid overpressure having once

occurred. Similar vein textures are observed in the Mercia Mudstone Group in Somerset [3], and

it is likely these represent a temporary permeable vein network. Also, the previously mentioned

black spheroidal grains and black residues are likely of a hydrocarbon origin [John Parnell,

personal communication]. Therefore the presence of a permeable vein network, hydrocarbons and

a possible pressurised metal-bearing basinal fluid are key to the ore genesis.

References

[1] H. Naylor et al. “Genetic studies of red bed mineralisation in the Triassic of the Cheshire

Basin, northwest England”, Journal of the Geological Society, vol. 146, pp. 685-699, 1989.

[2] J. W. Faithful, and N. Hubbard. “Coffinite from Gipsy Lane Brickpit, Leicester”,

Journal of the Russell Society, vol. 2, no. 1, pp. 25-28, 1988.

[3] S. L. Philipp. “Geometry and formation of gypsum veins in mudstones at Watchet,

Somerset, SW England” Geological Magazine, vol. 145, no. 6, pp. 831-844, 2008.

83

The Role of Faults in Localising Mineral Deposits in the Irish Zn-Pb Orefield

John J Walsha, Chris G Bonsonb, and Vincent Carbonic

a Fault Analysis Group, University College Dublin, Dublin, Ireland, john.walsh@ucd.ie, b SRK Consulting

(UK) Ltd., Cardiff, UK, c CurHydro, Bailleval, France.

Faults play a crucial role in the formation of mineral deposits globally, acting as conduits for ore

fluids and forming the bounding structures to deposits. Despite their intrinsic importance,

understanding of the precise geometric and displacement characteristics of faults which localize

the flow and entrapment of ore fluids is far from complete. Currently, structural models

accounting for the flow of mineralising fluids have drawn mainly on studies of episodic fluid

flow attributed to earthquake-related stress cycling in the crust [e.g., 1-4]. These models provide a

rationale for the distribution of dilational strains due to the coseismic slip around fault

complexities and for the redistribution of crustal fluids into sites of lower mean stress, such as

fault step-overs and bends.

Here we examine the controls on mineralisation in a basinal setting where, locally at least, fault

activity had ceased. We present the results of studies of the structural geology of three mines in

the Irish Zn-Pb orefield, Galmoy, Lisheen and Silvermines [5-7], which support a model in which

fault growth-related deformation and hydraulic fracturing causes the formation of stratiform

dolomitic breccias within the hangingwalls of faults, which are, in turn, precursors to post-

faulting up-fault migration of Zn-Pb mineralizing fluids and their entrapment mainly within the

breccias. The model invokes the existence of normal fault relay zones at fault segment boundaries

to be responsible for the localisation of up-fault fluid flow, with smaller intra-deposit faults

locally acting as both conduits and barriers to lateral fluid migration. We show that whilst

segment boundaries and associated complexities on deposit-bounding fault systems occur over a

broad range of scales which tend to reflect the mechanical stratigraphy of the host rocks, only

relay zones with a particular size:displacement ratio are likely to have contributed significantly to

the localisation of up-fault fluid flow. Moreover, their precise geometrical arrangement may have

favoured the flow of ore fluids into the hangingwall, where Irish Zn-Pb deposits are observed,

rather than their continued ascendance along the fault to higher levels, possibly reaching the sea

floor.

References

[1] R. H. Sibson. “Earthquake rupturing as a mineralizing agent in hydrothermal systems”,

Geology, vol. 15, pp. 701-704, 1987.

[2] R. Muir-Wood, and G. C. P. King. “Hydrological signatures of earthquake strain”,

Journal of Geophysical Research, vol. 98, pp. 22035-22068, 1993.

[3] S. F. Cox et al. “Principles of structural control on permeability and fluid flow in

hydrothermal systems”, Reviews in Economic Geology, vol. 14, pp. 1-24, 2001.

[4] S. Micklethwaite, and S. F. Cox. “Fault-segment rupture, aftershock zone fluid flow, and

mineralization”, Geology, vol. 32, pp. 813-816, 2004.

[7] C. J. Andrew. “The tectono-stratigraphic controls to mineralization in the Silvermines

area, County Tipperary, Ireland”, In Geology and Genesis of Mineral Deposits in Ireland.

(Eds C. J. Andrew, R. W. A. Crowe, S. Finlay, W. M. Pennell, and J. F. Pyne), Irish

Association for Economic Geology, Dublin, pp. 377-418, 1986.

[6] J. D. Johnston. “Regional fluid flow and the genesis of Irish Carboniferous base metal

deposits”, Mineralium Deposita, vol. 34, pp. 571-598, 1999.

[7] J. D. Johnston et al. “Basement structural controls on carboniferous-hosted base metal

mineral deposits in Ireland”, In Recent advances in Lower Carboniferous Geology (Eds P.

Strogen, I. D. Sommerville, and G. Ll. Jones), Geological Society, London, Special

Publication, vol. 107, pp. 1-21, 1996.

84

Sea Floor Mining, Challenges and Opportunities

Philip Weaver

Seascape Consultants Ltd., Romsey, UK

phil.weaver@seascapeconsultants.co.uk

Deep-sea mining refers to the mining of polymetallic minerals on the deep sea-floor. These

include manganese nodules, cobalt crusts and seafloor massive sulphides. The potential for deep-

sea mining was a hot topic in the 1970’s and early 1980’s and the first contractors to the

International Seabed Authority signed up in 2001. Progress however remained slow through the

early part of the 21st Century until 2010 when contractors again began to register with the ISA.

Since 2010 there has been an increase from 8 to 17 contractors with an additional 9 awaiting

signature. This renewed interest is being driven by an increase in demand for metals, by

presumed simpler planning control in the high seas, and by a need for security of supply for many

countries. Technological challenges present some problems in the deep-sea, especially the ability

to pump ores from the seabed at up to 6000 metres water depth, but these are seen as being less

challenging now that the hydrocarbon industry is working to 3000 metres.

Nautilus Minerals has commissioned the build of its seabed mining machines and entered into

agreement for the build of its ship to mine Solwara 1 in the Bismark Sea off Papua New Guinea.

This is an SMS deposit located on an active vent system in a back-arc location at 1600 metres

water depth. Mining is scheduled to start in 2017. Manganese nodules are common on the

abyssal plains of the Pacific and Indian Oceans and many license blocks have been issued in the

Clarrion Clipperton Zone of the central Pacific. Mining nodules from the top 30 cm of the seabed

will be an easy task, but pumping them to the surface 4000-6000 metres above will be a

challenge. For cobalt crusts the challenge is to produce cutting equipment that can closely follow

the thickness of the ore without mining any of the underlying rock.

At present there are no regulations in place to control deep-sea mining on the high seas but the

ISA is currently developing these with a draft expected in 2015. One of the key issues will be

environmental monitoring and the MIDAS project (http://www.eu-midas.net/) is collecting

information to feed this process. Ecosystems in many of the areas that are being licensed for

exploration are poorly known. Examples include hydrothermal vents on mid-ocean ridges that

were only discovered in 1977 and the quiet abyssal plains of the Pacific where the seabed is

strewn with manganese nodules that have taken millions of years to grow. They each contain

unique, though very different, ecosystems and biodiversity, and both areas remain poorly

researched because of their remoteness and complexity. Key differences between on-land and at-

sea mining include the huge areas that will be mined for nodules and crusts and the potential

impact of particle-laden plumes that may have a negative impact hundreds of kilometres from the

mine site. Other issues include remediation that will be difficult or impossible in the deep-sea

combined with the extremely slow recovery times of some of the ecosystems.

This talk will provide an update on the progress towards mining in the deep-sea and outline some

of the key challenges.

85

Supercritical Venting and VMS Formation at the Beebe Hydrothermal Field,

Cayman Spreading Centre

Alexander P Webbera, Stephen Robertsb, Bramley J Murtona, and Matthew RS Hodgkinsonb

a National Oceanography Centre Southampton, UK, SO14 3ZH, a.webber@noc.ac.uk, b Ocean and Earth

Science, National Oceanography Centre Southampton, University of Southampton, UK, SO14 3ZH.

The Beebe hydrothermal field is the world’s deepest hydrothermal vent site at ~5000 metres

below sea level on the ultra-slow spreading mid-Cayman rise. The fluid venting at Beebe is

supercritical due to stable high temperatures of ~401ºC and a low salinity of ~2 wt% NaCl. This

salinity indicates phase separation has occurred, requiring higher temperatures at depth. As such,

the site offers a unique opportunity to study mineralization and hydrothermal processes in-situ, at

P-T conditions normally expected deep within the crust.

The hydrothermal system shows two distinct mineral and chemical assemblages. Focussed vent

chimneys, those with a single or few active orifices, contain less than 1 wt% zinc and display a

simple mineralogical assemblage of chalcopyrite in the chimney inner wall, through to bornite

and then a pyrite/anhydrite mixture on the exterior. So-called “beehive” chimneys, which are

more uniformly permeable and vent fluid from many smaller orifices, are zinc-rich and display an

assemblage of sphalerite, pyrite, marcasite and pyrrhotite. Samples of mound talus are almost

exclusively pyrite, with a subordinate assemblage of oxides, sulfates and chlorides. The

asymmetrical morphology of the sulfide mound and talus is strongly controlled by its location

atop a volcanic edifice and position adjacent to a prominent fault scarp, with virtually all the talus

spreading down-slope towards the west, whilst east of the field is sulfide-free. Metalliferous

sediment collects in depressions below the vent sites that shows limited pelagic or hemipelagic

input, preserving relatively high copper and zinc contents.

The extreme physical conditions found at Beebe make it an ideal end-member seafloor

hydrothermal system for the study of metal mobility, hydrothermal circulation and VMS

formation under high pressure supercritical conditions.

86

Lifespan and Fluid Evolution for Magmatic-Hydrothermal Systems: A U-Pb,

Re-Os and O Isotope Case Study from Qulong Porphyry Cu-Mo Deposit,

Tibet

Li Yanga, David Selbya, Daniel Condonb, and Li Xianhuac

a Department of Earth Sciences, Durham University, Durham, UK, li.yang@durham.ac.uk, b NERC Isotope

Geoscience Laboratory, British Geological Survey, Keyworth, UK, c State Key Laboratory of Lithospheric

Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.

Porphyry Cu systems (PCS) represent the world’s largest known exploitable concentrations of

Cu, Mo, and the second largest for Au. As a result, PCS presently supply 75% of the world’s Cu,

50% of the Mo, and approximately 20% of the Au, together with the majority of the Re, and

minor amounts of other metals (Ag, Pd, Te, Se, Bi, Zn, and Pb) [1]. As such PCS are regarded as

the most important ore deposit type [1]. Over one hundred years of exploration and research has

resulted in PCS being most studied and potentially best known and understood deposit type [2].

However, although extensively studied, PCS remain poorly understood with respect to the

understanding of the relationship between magmatism and mineralization (release of

hydrothermal fluids), how long it takes to form a porphyry ore body [3] as well as the P-T-X

evolving of ore-forming fluids [4].

Here we employee the currently most precise and accurate U-Pb zircon (CA-ID-TIMS, NIGL)

and Re-Os molybdenite (ID-N-TIMS, Durham) methodology to accurate evaluate the chronology

of magmatism versus mineralization in the post-collision related giant Qulong porphyry Cu-Mo

deposit (≥ 10 Mt Cu and ~ 1 Mt Mo metals [5]), Tibet, China. This temporal framework is further

utilized to track the evolution of the hydrothermal fluid represented by quartz veins through SIMS

quartz O isotope and fluid inclusion data.

Preliminary data indicates the Rongmucuola granodiorite pluton, which predated the

mineralization and host most of the ore, was emplaced at 17.0±0.02 Ma, with mineralization

occurring between 16.23±0.06 and 15.78±0.06 Ma. The main stage mineralization happened

around 16.0 Ma, thus the minimum duration of the mineralization event is 0.33 my. The cease of

the magmatic-hydrothermal activity was marked by the post-ore and barren quartz-diorite at

15.2±0.02 Ma. Unlike previous research [4] which suggests an overall progressively

involvement of meteoric water throughout the mineralization processes, our SIMS quartz O

isotope suggests meteoric water (5±0.5 per mil) and magmatic-sedimentary fluid (12±0.5 per mil)

was involved in the ductile-brittle transition stage and early stage, respectively, while the overall

budget was dominated by magmatic water (9±0.5 per mil).

References

[1] R. H. Sillitoe. “Porphyry copper systems”, Economic Geology, vol. 105, no. 1, pp. 3-41,

2010.

[2] E. Seedorff et al. “Porphyry deposits: characteristics and origin of hypogene features”,

Economic Geology 100th Anniversary Volume, pp. 251-298, 2005.

[3] M. Chiaradia et al. “How Accurately Can We Date the Duration of Magmatic-

Hydrothermal Events in Porphyry Systems? - An Invited Paper”, Economic Geology, vol.

108, no. 4, pp. 565-584, 2013.

[4] D. R. Cooke et al. “Evidence for Magmatic-Hydrothermal Fluids and Ore-Forming

Processes in Epithermal and Porphyry Deposits of the Baguio District, Philippines”,

Economic Geology, vol. 106, no. 8, pp. 1399-1424, 2011.

[5] Z. Yang et al. “Geology of the post-collisional porphyry copper-molybdenum deposit at

Qulong, Tibet”, Ore Geology Reviews, vol. 36, no. 1, pp. 133-159, 2009.

87

Metal Transport in Fluids: Brines and Not-Brines

Bruce WD Yardleya, David Banksa, and Delia Cangelosia

a School of Earth & Environment, University of Leeds, UK

B.W.D.Yardley@leeds.ac.uk

In recent decades the importance of brines for ore-formation has been demonstrated for a wide

range of deposit types and geological settings. Chloride can reach high concentrations in fluids

from sedimentary, igneous and metamorphic environments and complexes many metals in

solution. Nevertheless, there are elements, for example Au but potentially others also, which are

preferentially complexed by other ligands and are transported and concentrated in low-Cl fluids.

Brines in sedimentary sequences may be derived from evaporation of seawater or dissolution of

halite. Both types have the potential to react with host minerals, exchange cations and acquire

increased concentrations of a range of transition metals. In practice, the extent to which this takes

place in low-T sedimentary basins is limited, but at temperatures in excess of c. 150oC becomes

significant. The transition into metamorphic conditions can lead to more saline fluids with higher

metal concentrations, but is also accompanied by a reduction in the amount of pore fluid and its

mobility. Nevertheless a range of ore deposits are associated with this transitional, deep basinal

environment, especially where structures focus flow. Examples range from Pb – Zn deposits and

copper belt ores to emerald deposits and hypogene enrichment of BIF ores, but the extent to

which these contrasting deposit types reflect different brine chemistries or different environments

of precipitation remains a subject of considerable interest.

The lack of fluid in higher grade metamorphic rocks means that contemporaneous ore formation

is increasingly rare at higher grades, even though metal-rich brines occur. In contrast magmatic

fluids often have Cl as the dominant cation and may be very saline. Transition metal levels in

magmatic brines are often orders of magnitudes higher than in sedimentary brines, but the amount

of fluid is less. Depending on the evolution of the magma body, significant levels of other ligands

may also be present, and may impact on metal transport; for example F-rich fluids can evolve

from Ca-poor melts and transport Al, Si and probably related cations.

Because of “salting out” effects that are widespread at crustal pressures, highly saline fluids are

relatively low in dissolved gases, whereas low salinity fluids can carry significant loads of CO2,

H2S and other volatile species, including As, Sb and Hg. There are examples of metal transport in

low-Cl fluids from a wide range of environments, including shallow geothermal fields, deeper

magmatic systems and end-orogenic metamorphic fluids. Of the volatile species with the

potential to complex specific metals only H2S has been investigated in detail. Arsenic may be

particularly abundant in some low-salinity fluids and As-rich fluids have been described from

several environments, however the possible role of As-complexing in transport of Au or other

metals is not known. There is little evidence for enhancement of metal solubility by CO2 under

upper crustal conditions, except through lowering of pH, but there is some circumstantial

evidence that CO2-saturated brines may mobilise Ni more effectively than brines alone.

Hydrocarbons are also more soluble in low-salinity aqueous fluids, and might result in enhanced

solubility for specific transition elements.

Sulphate is an important anion in a range of upper crustal fluids where alkali-earth cations are

sparse, and present in many brines. Although sulphate is not widely implicated in many types of

ore genesis, sulphuric acid generated by oxidation of magmatic H2S plays an important role in

leaching altered rocks in many geothermal fields. Notably, sulphate forms aqueous complexes

with the HREE, and hydrothermal HREE enrichment at the Huanglongpu carbonatite deposit,

China, is conspicuously associated with sulphate-rich fluid inclusions.

88

Delegate List

Name (Last, First) Affiliation

Abraham-James, Thomas

Arfè, Giuseppe Università di Napoli

Armitage, Paul Paul Armitage Consulting Ltd

Armstrong, Robin Natural History Museum

Bakker, Edine

Banyard, James

Barros, Renata University College Dublin

Bartlett, Ryan Barrick Exploration

Bay, Claire Stratex International

Belcher, Richard RWB Exploration Ltd

Bell, Robin-Marie Geological Survey of Denmark and Greenland

Betton, Sebastian University of Leicester

Bird, Philip Kingston University

Bissell, Christopher University of Southampton

Bodman, Toby Camborne School of Mines

Boni, Maria Università di Napoli

Bonson, Christopher SRK Consulting

Boyce, Adrian SUERC

Brownscombe, Will Natural History Museum

Campbell, Linda University of Manchester

Cangelosi, Delia University of Leeds

Carluccio, Roberta University of Padua

Caulfield, Brendan

Chant-Tuft, Olivia Imperial College London

Chapman, John Geological Survey of Canada

Chelle-Michou, Cyril University of Geneva

Clark, Jake University of Leicester

Clifford, John Antofagasta

Coller, Dave Earth Tectonics Ltd

Cooper, Frances University of Bristol

Cope, Ian ArcelorMittal Mining

Coppard, Jim

Cromwell, Edward Durham University

Deady, Eimear British Geological Survey

Deltenre, Alex

Dempsey, Edward Durham University

Dennis, Paul University of East Anglia

Dobrzanski, Andrew Durham University

Dodds, Peter Anglo American

Douglas-Hamilton, Charles Universal Dawnus

Duffin, Adam Rio Tinto

Elliott, Holly University of Southampton

Evrard, Maxime University of Liège

89

Name (Last, First) Affiliation

Fallon, Emily University of Bristol

Fisher, Harry Imperial College London

Fletcher, Tim Reservoir Minerals Inc

Foster, Bob Stratex International

Fox, Kevin Rio Tinto

Francis-Smith, Benjamin University of Leicester

Freeman, Jack Camborne School of Mines

Gernon, Tom University of Southampton

Gibbs, Jeremy GibbsGeoGIS Ltd

Gilmer, Amy University of Bristol

Goodenough, Kathryn British Geological Survey

Graham, Shaun Carl Zeiss

Grimshaw, Matthew University of Leeds

Gunn, Gus British Geological Survey

Hardy, Liam University of Brighton

Harman, Eloise Natural History Museum

Hart, Lisa Imperial College London/Natural History Museum

Hartshorne, Craig Anglo American

Hartwell, Tony Knowledge Transfer Network

Hatcher, Guy

Hawkes, Nick Rio Tinto

Herrington, Richard Natural History Museum

Hodgkinson, Matt University of Southampton

Holwell, Dave University of Leicester

Hooper, Cameron University of Leicester

Hughes, Hannah Cardiff University

Hughes, Joshua University of St Andrews

Jaunzems, Andrew Rio Tinto

Jenkin, Gawen University of Leicester

Jillings, Katherine Imperial College London

Karhunen, Otto Lafarge Tarmac

Karykowski, Bartosz Cardiff University

Katie, McFall University of Southampton

Knight, Robert University of Southampton

Kocher, Simon Natural History Museum

Krüger, Jens University of Southampton

Larcombe, Grace University of Southampton

Large, Duncan Consultant

Lepley, Ben SRK

Lepp, Claudia University of Leicester

LI, Yang Durham University

Lloyd, Christopher University of Southampton

Lusty, Paul British Geological Survey

McCusker, James Teck Resources

McDonald, Iain Cardiff University

90

Name (Last, First) Affiliation

McLaurin, Neil Neil McLaurin Associates

Menendez, Amaya University of Southampton

Menuge, Julian University College Dublin

Meshkova, Luba Stratex International

Moles, Norman University of Brighton

Moon, Charlie Camborne School of Mines

Myhill, Daniel University of East Anglia

Naden, Jon British Geological Survey

Naldrett, Anthony

Neave, David University of Cambridge

Nicoll, Graeme Neftex

Norman, Rachel Natural History Museum

Pacey, Adam Natural History Museum

Patten, Clifford Stockholm University

Pegg, David Aureus Mining

Periasamy, Durgha University of Portsmouth

Perkins, Rebecca University of Bristol

Pesquidous, Raphael Imperial College London

Pierre, Josso University of Southampton

Pinto-Ward, Carmen Imperial College London

Pitcairn, Iain Stockholm University

Pollard, David

Prasser, Richard University of Leicester

Prichard, Hazel Cardiff University

Richards, Simon University of Leicester

Roberts, Steve University of Southampton

Russel, Rajendra Mineralogical Society

Saintilan, Nicolas University of Geneva

Santoro, Licia Università di Napoli

Saunders, Ben Neftex

Selwyn, Robert University of Leicester

Sharman, Libby PR Associates

Sievwright, Robert Imperial College London

Smith, Daniel University of Leicester

Smith, Heather University of Southampton

Smith, James Kingston University

Smith, Martin University of Brighton

Smyth, Dermot Lonmin PLC

Sotiriou, Paul Norwegian University of Science and Technology

Sparks, Steve

Spence-Jones, Carl

Stacey, Mark

Steiner, Benedikt Rio Tinto

Stott, Daniel University of Brighton

Strachan, Rebecca University of Leicester

91

Name (Last, First) Affiliation

Tapster, Simon NERC - British Geological Survey

Taylor, Adam University of Leicester

Treloar, Peter Kingston University

Vaughan, Alan Midland Valley Exploration Ltd

Walker, Sandy Rio Tinto

Walsh, John University College Dublin

Waugh, Ben Aureus Mining

Weaver, Phil Seascape Consultants

Webber, Alex University of Southampton

Wenborn, Alice Reservoir Minerals Inc

Willan, Robert Consultant, Aberdeen

Wood, Martin University of Southampton

Yardley, Bruce University of Leeds

92

Useful Maps

Map of Southampton (Conference Locations, Suggested Hotels and Travel

Terminals)

93

Map of the National Oceanography Centre

94

Map of Drinking and Dining Areas

95

Map with Directions to St. Mary’s Stadium (Dinner Venue)