The Applied Mineralogist - Mineralogical Society
Transcript of The Applied Mineralogist - Mineralogical Society
AMGAMGMineralogical Society
Applied MineralogistThe
Web: www.minersoc.org/amg.htmlTwitter: www.twitter.com/amg_minEmail: [email protected]
The Bulletin of the pplied ineralogy roupA M G
March 2020Volume 5Number 1
From the AMG committeeHello and welcome to the March edition of Applied
Mineralogist! We present a special feature on brand new
research on and how it helps us apatite in volcanic rocks
to understand and crustal magma evolution porphyry
deposits formation. Read about the first meetings this
year and . Finally, test your mineralogical : MDSG VMSG
vocabulary on the . mineralogy crossword
Ÿ Summary of VMSG by Kevin Wong (p. 2)
In this issue:
Ÿ Summary of MDSG 2020 by Holly Andrews (p. 1)
Ÿ The record of crustal magma evolution deciphered by apatite
in volcanic rocks by Chetan Nathwani (p. 3 - 5)
Ÿ #AppliedMineralogy (p. 4)
Ÿ Announcement of the IAEG meeting (p. 5)
Ÿ Mineralogy Crossword (p. 6)
March 2020, 5(1). Page 1
Charlie Compton-Jones
Adam EskdaleEdited by:Stefan HornHolly Andrews Georgian Manuc
Prize winners
The theme of the conference was “metals for a green future”, with talks divided into the following sessions: Critical Metals, Gold, Porphyry Systems, Ni-Cu-PGE, Base Metal Deposits, Hydrothermal Processes and Methods. In total, there were 29 talks. There were also 3 keynote talks by Prof. John Dilles (Oregon State University), Prof. Sarah Gleeson (GFZ Potsdam; talk sponsored by AMG) and Prof. John Thompson
(PetraScience Consultants Inc).The Mineral Deposits Studies Group (MDSG) had its rd th th
43 annual winter meeting in London from the 6 -8January 2020. It was hosted at the Natural History Museum, organised by Prof. Jamie Wilkinson and the London Centre for Ore Deposits and Exploration (LODE) research group. Dr Richard Sillitoe presented a “Porphyry Copper Deposits from Top to Bottom” workshop on 6�� January prior to the Icebreaker.
The Rio Tinto Best Talk Prize: Chetan Nathwani (PhD candidate, Natural History Museum) for: “The magmatic evolution of the Yarabamba batholith, Southern Peru: protracted magmatism culminating in multi-centred giant porphyry Cu-Mo mineralisation”.Anglo American Best Poster Prize: Emily Brugge (PhD candidate, Natural History Museum) for “Apatite inclusions in Zircon: records of porphyry melt evolution”.MDSG Project Prize: George Stonadge for his master thesis (PhD candidate, University of Leicester). This prize is awarded by a panel of academics to the best undergraduate or master thesis.
Mineral Deposit Studies Group Mee�ng (MDSG), 6��-8�� January, London
Summary report by Holly Andrews, Imperial College London
Photo from mdsg.org.uk
MDSG conference dinner in the Earth Hall, Natural History Museum.
March 2020, 5(1). Page 2
Finally, a big thank you to the organising committee of
Paul Cole, Michelle Harris, and Irene Manzella for
coordinating a successful and productive VMSG
meeting (including an exceptional conference dinner
and party), and all the best to the organising
committee of next year's VMSG, to be held at the
University of Manchester.
Congratulations to the two VMSG student prize
winners, Gregor Weber (University of Geneva) for his
poster on Thermochemical modelling of eruptible
magma chemistry, and Sally Law (University of
Edinburgh) for her talk titled Olivine reveals removal of
mantle lithosphere, coincident with the onset of
rhyolitic volcanism in the Taupo Volcanic Zone, New
Zealand. A special mention also to Hannah Buckland
and James Crosby, runners-up for the poster and talk
prizes respectively.
This year, VMSG was hosted by the University of
Plymouth. Despite a chilly, rainy backdrop, several
hundred delegates from research institutions across
the UK and Europe made the trip to the south of
England to share their recent progress in unravelling
the causes, correlations, and consequences that both
drive and result from worldwide volcanic activity. With
over 50 presentations and 100 posters split across
seven research symposia, this year's VMSG had
something for and from everyone across the
volcanological community. Topics covered included
new advances in volcanic hazards, r isk and
communication, magma storage and transport, and
volcanic monitoring and the forecasting of eruptions.The keynote speakers reflected the diversity of
volcanologists present at this meeting. Kathy Cashman
(University of Bristol) highlighted issues volcanologists
face when developing a conceptual model for volcano
forecasting; Constanza Bonadonna (University of
Geneva) discussed risk modelling on the island of
Vulcano; Johan Lissenberg (Cardiff University)
illustrated his research on understanding magmatic
processes at mid-ocean ridges and lower oceanic
crust; Mike Cassidy (University of Oxford) contrasted
the controls on eruptive and effusive volcanic
eruptions. This year's VMSG award went to David Pyle
(University of Oxford), who additionally presented a
keynote on his research over the course of his career,
titled Living with volcanoes: past, present and future.
Volcanic and Magma�c Studies Group Mee�ng (VMSG), 7��-9�� January 2020, Plymouth
A summary report by Kevin Wong, University of Leeds
VMSG award Winner David Pyle during his talk. photo by Paul Cole from Twitter.
March 2020, 5(1). Page 3
The record of crustal magma evolu�on deciphered by apa�te in volcanic rocks: applica�ons to igneous petrology and in understanding porphyry ore deposit forma�on
, Natural History Museum, LondonChetan Nathwani
Introduc�on
The last decade has seen a surge in the applica�on of
LA-ICP-MS in determining trace element chemistry in
petrogene�c studies and explora�on for mineral
deposits. In par�cular, igneous accessory phases have
a�racted a large amount of interest since these can
capture snapshots of the evolu�on of magmas and can
provide insights into processes determining the
occurrence of valuable ore deposits. The largest
accumula�ons of copper in the Earth's crust, porphyry
copper deposits, are formed in subduc�on zones from
the exsolu�on of metal-charged fluids from large upper
crustal arc magma reservoirs. However, these deposits
are only formed in very par�cular segments in
magma�c arcs, and within narrow �me windows during
arc evolu�on.
Interes�ngly, these metallogenic epochs are marked
by dis�nc�ve changes in the trace element chemistry of
arc magmas towards more hydrous and frac�onated
composi�ons (high Sr/Y, high La/Yb and high Eu) [1].
This is thought to reflect tectonic perturba�ons that
enhance crustal compression, causing magmas to stall
in the lower crust and “stew up” their vola�les.
Typically, in a dry magma in the lower crust, plagioclase
is stable and is the dominant frac�ona�ng mineral
phase. However, if we kick up the pressure and the
water content, the mineral assemblage switches to
being amphibole-dominated (in which Yb and Y are
compa�ble) at the expense of plagioclase (in which Sr
and Eu are compa�ble), which causes these dis�nct
changes in geochemical ra�os [2]. Eventually when
these magmas reach the upper crust, they have
accumulated substan�al quan��es of fluid, metal and
sulfur, so that they can generate a giant porphyry
copper deposit [3]. The chemical fingerprints of this
are u�lised in explora�on, since they can narrow down
magma�c districts and regions that are predisposed to
generate these large porphyry copper systems (i.e.
metallogenically fer�le systems). These chemical
signatures of a long-lived lower crustal magma
evolu�on (Sr/Y, La/Yb and high Eu) have also been
employed as indicators of crustal thickening and to
track arc magma petrogenesis [4]. The common
approach of using whole-rock chemistry as indicators
of this deep-seated magma history holds limita�ons,
since these chemical signatures can be obscured by
later magma�c, or even hydrothermal processes.
Despite its low abundance in rocks, apa�te has an
array of uses in geoscience due to its ability to
incorporate and concentrate a huge number of
elements across the periodic table. It is widely used in
fission track da�ng, radiometric da�ng, trace element
geochemistry and in tracking the vola�le budgets of
melts and fluids. We wanted to test whether apa�te
crystals in igneous rocks may provide a tool to track
and decipher the long-lived lower crustal magma
history from other magma evolu�on processes. Our
study focused on volcanic rocks from the Cenozoic of
Central Chile that cover a window of arc magma�sm
that culminated in the Earth's most economically
valuable porphyry copper mineralisa�on event,
Apa�te: an archive of magma�c evolu�on
Figure 1. Scanning electron microscope image of apa�te crystals in the samples studied. (A) Apa�te microphenocryst containing zircon inclusion. (B) Apa�te inclusions in magne�te (mgt) crystal exsolving ilmenite (ilm). (C) SEM-cathodoluminescene image showing two zoned apa�te microphenocrysts.
Solu�ons Crossword: 1. Troilite, 2. Hoodoo, 3. Vitrinite, 4. Sylvite, 5. Kimberley, 6. Germanium, 7. Brown, 8. Apa�te, 9. Aquamarine, 10. Goblin, 11. Olivine
March 2020, 5(1). Page 4
Deciphering magma�c evolu�on using apa�te trace
element chemistry
valuable porphyry copper mineralisa�on event, forming Los Pelambres, Rio Blancos-Los Bronces and El Teniente. The genesis of these deposits is marked by a dis�nct shi� in magma chemistry towards high Sr/Y, high La/Yb and high Eu composi�ons.
We analysed the trace element chemistry of the
apa�te crystals in our volcanic rocks (Fig. 1) by LA-ICP-
MS. The apa�te trace element data showed a clear
correla�on in Sr/Y and Eu/Eu* (a measure of the
magnitude of the Eu anomaly) both within a single
sample and between samples (Fig. 2A). This indicates
that apa�te is a reliable tracer of the evolu�on of Sr/Y
and the Eu anomaly of the melt. We used Mg in apa�te
as a proxy for melt differen�a�on to track how Sr/Y
and Eu/Eu* change as the melt evolves (Fig. 2B). This
demonstrates that apa�te does not record a trend of
increasing Sr/Y with increasing Mg, and therefore does
not record the development of the high Sr/Y
determined by lower crustal magma evolu�on (where
amphibole frac�onates). This is not unexpected, since
we know that apa�te would not crystallise at the
temperatures and pressures found in the lower crust.
However, when apa�te does crystallise in the shallow
crust, it can inherit the signature of a melt that
previously evolved in the lower crust (high Sr/Y, high
Eu/Eu*). We modelled frac�ona�on of amphibole
from a primi�ve melt and found it produced an
increase in Sr/Y and Eu/Eu* that produced the hidden
or “cryp�c” trend, not seen in the apa�te
composi�ons (Fig. 2). Therefore, apa�te in volcanic
rocks is recording a deep frac�ona�on process that is
rarely exposed. We found that the apa�tes that have
the strongest signal of lower crustal evolu�on, are
derived from rocks that formed in thickened arc crust
and may indicate magma composi�ons predisposed to
form porphyry ore deposits.
Figure 2 Trace element chemistry of apa�te in volcanic rocks. Eu/Eu* vs. Sr/Y. Sr/Y vs. Mg. Dashed line shows apa�te A Bcomposi�ons from a model that frac�onates an amphibole-dominant assemblage from a primi�ve melt composi�on, indica�ng that the high Sr/Y and Eu/Eu* in apa�te can be accounted for by lower crustal magma evolu�on.
#AppliedMineralogy @ J. Leutholdvia EGU GMPV Division
@ J. Leuthold
From your #ThinSectionThursdays, #FieldworkFridays
& #MineralMondays, our #AppliedMineralogy
winner is...
with a beautiful gabbro in transmitted light from the
Rum Layered Intrusion, Scotland.
March 2020, 5(1). Page 5
Nathwani, C. L., Loader, M. A., Wilkinson, J. J., Buret, Y., Sievwright, R. H., Hollings, P. (2020) Mul�-stage arc magma evolu�on recorded by apa�te in volcanic r o c k s . G e o l o g y , 4 8 ( 4 ) . h�ps://doi.org/10.1130/G46998.1
This ar�cle is based on the paper:
References
Our approach demonstrates that apa�te entrained
as crystal cargo in volcanic erup�ons can record
valuable informa�on on the composite evolu�on of
arc magmas in the crust. Since the informa�on
recorded by apa�te indicates protracted lower crustal
magma evolu�on, it can poten�ally indicate the
metallogenic fer�lity of arc magmas.
[1] Richards, J. P., & Kerrich, R. (2007). Special paper: Adakite-like rocks: Their diverse origins and ques�onable role in metallogenesis. Economic Geology. 102(4), 536-576.
Though apa�te can record the signature of lower crustal magma evolu�on, apa�te is co-crystallising with other mineral phases in the shallow crust that can modify the melt chemistry. We found that within single samples, trends in Mg, Sr/Y and Eu/Eu* were clear which always showed decreasing Sr/Y and Eu/Eu* with decreasing Mg (i.e. as the melt evolves, apa�te is slowly recording the melt decreasing in Sr/Y and Eu/Eu*). This is consistent with apa�te crystallising with a phase that is removing the Sr and Eu from the melt – probably plagioclase (Sr and Eu are compa�ble in plagioclase) – which is the dominant phenocryst phase in the rock. Consequently, though apa�te is recording this interes�ng lower crustal frac�ona�on signature, this signal in apa�te is gradually overprinted by later melt evolu�on. We therefore conclude that apa�te can track mul�ple stages of arc magma evolu�on.
Summary and conclusions
[2] Müntener, O., Kelemen, P. B., & Grove, T. L. (2001). The role of H O during crystalliza�on of primi�ve arc magmas 2
under uppermost mantle condi�ons and genesis of igneous pyroxenites: An experimental study. Contribu�ons to Mineralogy and Petrology. 141(6), 643-658.
[4] Profeta, L., Ducea, M. N., Chapman, J. B., Paterson, S. R., Gonzales, S. M. H., Kirsch, M., Petrescu, L., & DeCelles, P. G. (2015). Quan�fying crustal thickness over �me in magma�c arcs. Scien�fic Reports 5, p. 17786.
[3] Chiaradia, M., & Caricchi, L. (2017). Stochas�c modelling of deep magma�c controls on porphyry copper deposit endowment. Scien�fic Reports 7(1), 1-11.
The Irish Associa�on for Economic Geology (IAEG) was founded in 1973 with the primary goal of providing a forum for geoscien�sts working in economic geology in Ireland.
At the turn of each decade the Associa�on organises an interna�onal conference. The 2020 conference will be:
Minerals 2020 Europe’s Past, Present and Future
Venue: Salthill Hotel, Galway, IrelandDate: 14th – 16th May 2020
Website: h�ps://www.iaeg.ie/page-18136; Contact: [email protected]
The conference will explore Europe’s past mining tradi�on, document the current ac�vity and look to the future for the sector. The conference will address these through the following technical sessions:
• Se�ng the scene: a series of talks on the current state of the minerals sector in Europe.• Precambrian metallogeny: following a scene se�ng keynote address on Precambrian geology and metallogeny there will
be a series of deposit specific talks.• Caledonian metallogeny: following a scene se�ng keynote address on Caledonian geology and metallogeny there will be a
series of deposit specific talks.• Hercynian metallogeny: following a scene se�ng keynote address on Hercynian geology and metallogeny there will be a
series of deposit specific talks.• Alpine metallogeny: following a scene se�ng keynote address on Alpine geology and metallogeny there will be a series of
deposit specific talks.• The future: a series of talks looking at how the minerals sector is likely to evolve in the next decade and addressing issues
of relevance to the sector.
Interested in joining the Mineralogical Society and Applied Mineralogy Group? Go to: for membership details.http://www.minersoc.org/
Mineralogical Society
Mar ‘20 24 - 26
Calendar
AMGAMG
Founded in 1963 by Norman F.M. Henry, the AMG is a special interest group of the Mineralogical Society of Great Britain and Ireland. We encourage and promote the study and research of mineralogy applied to ores and related industrial mineral materials. This encompasses: ore microscopy, fluid inclusions, nuclear minerals, coals, refractories, slags, ceramics, building materials, nuclear waste disposal, carbon capture and storage, down-hole borehole alteration, and mineral-related health hazards.
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Applied Mineralogist. Please forward any articles, comments or
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Notices
Metamorphic Studies Group RiP Mee�ngSt. Andrews, Scotland
May ‘2014 - 16
Jun ‘203 - 5
Geochemistry Group 50th Ann. Symp. & GGRiPOxford, England
Jun ‘2021 - 26
Sep ‘20 6 - 10
European Mineralogical Conference (EMC)Krakow, Poland
Oct ‘20 23
Diffusion in Minerals, Rocks and Melts:Pi�alls and poten�alLondon, England
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11. Mineral found in Mediterranean food
3. Maceral, which got its name from glass
9. Poseidon's favourite gemstone
1. Variety of pyrrho�te and isotope standard
10. Early German miners named cobalt a�er this fantas�c creature
6. Cri�cal metal used in solar panels
5. City of the “Big Hole” in South Africa
2. Magical rock forma�on in deserts
4. It comes last in the evapora�on sequence
7. Streak colour of chromite
8. A hungry Phosphate
Mineralogy Crossword
Solu�ons are at the bo�om of Page 3
Goldschmidt ConferenceHonolulu, Hawaii
Minerals 2020 (IAEG)Galway, Ireland