Orogenic Gold Deposits - Pembrook Resources

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Orogenic Gold Deposits

• Definitions• Geological Environment• Age• Host Rocks• Related Deposits• Mineralization, Veins & Alteration• Structural Settings• Mode of Formation• Favorable Exploration Characteristics• World & Latin America Examples

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OROGENIC GOLD

INTRUSION-RELATED

EPITHERMALSPLACERS

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• Orogenic Gold deposits are gold deposits formed in regionally metamorphosed terranes during compressional to transpressional defomation processes at convergent plate margins in accretionary and collisional orogens (Groves et al., 1998)

• Mesothermal, mother-lode type, metamorphic rock-hosted, shear-zone hosted, greenstone-hosted, turbidite-hosted, lode-gold, low-sulfide quartz-vein and slate-belt gold

• World Average: 100,000’s to 100Mt @ 2 to 15 g/t Au

• Grade – Variable 1.1 (Las Cristinas) to 21.3 g/t Au (Red Lake)

• 25% of world’s gold is sourced from orogenic gold deposits

Definition

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• Mineralization associated with accretionary to collisional tectonics at convergent plate boundaries

Geological Environment

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Dominantly Archean to Phanerozoic

• Late Archean (2.7 to 2.55 Ga)• Early Proterozoic (2.1 to 1.8 Ga)• Late Proterozoic (700 to 600 Ma)• Late Paleozoic (455 to 340 Ma) • Mesozoic-Cenozoic (285 to 70 Ma)

Coincide with periods of crustal growthand global thermal events

Age

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Kalgoorlie, Australia (40M oz)Timmins, Canada (70M oz)

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Obuasi, Ghana (30M oz)

Telfer, Australia (21M oz)Homestake, US (27M oz)

Tanami, Australia (10M oz)

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Murunta, Uzbekistan (170M oz)Linglong, China (16M oz)

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• Epigenetic

• Host lithology is deformed and metamorphosed – gold deposition late during the deformation-metamorphic history

• Can be any host rock

Common Hosts

• Mafic to intermediate metavolcanic sequences(or greenstones)

• Slate and low-grade metamorphic sediments (especially greywacke)

• Ultramafics, serpentinites, lamprophyric dykes

Not so Common Hosts

• Carbonates and platform sequences

• Conglomerates, evaporites

Host Rocks

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• Ultramafic-intrusion hosted Ni-Cu-PGM deposits

• Epithermal vein Hg and Sb mineralization

• Polymetallic vein deposits

• Placer and alluvial gold deposits

• Intrusion-related Au deposits (Las Haquillas)

Related Deposits

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Vein Mineralogy

• Principle Minerals - coarser-grained quartz, lesser albite, carbonate(as calcite, dolomite, ankerite, and siderite)

• Accessory Minerals - tourmaline, sericite and chlorite

• Others – Fuschite, mariposite, scheelite, roscoelite

• Poorly-developed mineral zonations both laterally and vertically

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Systen & Vein Geometry

• Dominantly a complex (discordant) array of anastomizing moderately to steeply dipping, laminated fault-fill quartz-carbonate veins in brittle-ductile shear zones and faults, with or without fringing shallow-dipping extensional veins and breccias

• Individual veins are 10 cm to 10 meters in width and typically have 100’s meters of strike extent

• Larger systems have multiple vein zones and may be depth persistent (Calle +2 km depth)

• Stockworks and hydrothermal breccias may represent the main mineralization styles when developed in competent units

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Vein Textures

• Textures represent the local deformation process and vary according to the nature of the host structure (extensional vs. compressional).

• Extensional veins typically display quartz and carbonate fibres at a high angle to the vein walls and with multiple stages of mineral growth

• Compressional laminated veins are composed of massive, fine-grained quartz. When present in laminated veins, fibres are subparallel to the vein walls

• Vein as open space infill and altered wall rock as replacements

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Alteration

• Proximal to distal assemblages

• Scale and intensity of alteration function of system depth and wall rock composition

• Best developed in ultramafic and greenstone hosts

• In sediment-hosted systems, alteration is narrow and discrete enveloping the mineralization

• Proximal alteration – sulphide minerals (py-po-aspy) and alkali-rick silicates (sericite, fuschite, albite, biotite) -white clay alteration

• Distal alteration – carbonate minerals (lower temperature varieties) with quartz

• Amphibolite, diopside, plagioclase and garnet present with lesser carbonate in +amphibolite-grade hosts

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Regional Metamorphism• Host rocks are typically metamorphosed to greenschist faces, with local amphibolite and granulte facies conditions

• Mineralization preferentially developed in metamorphic gradients (with greenschist or greenschist to amphibolite)

• Ore forming alteration products typicallyoverprinted on regional metamorphic mineralogy

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Economic & Sulphide Mineralogy

Sulphide mineralogy

• Pyrite, pyrrhotite, arsenopyrite > stibnite, galena, sphalerite, chalcopyrite, molybdenite, scheelite and tellurides

• Present in veins but more likely as wall rock alteration (especially po-py)

• Comprise less than 5 (in veins) to 10% (in wall rock) of the volume of the orebody

• No significant vertical mineral zoning or change in gold grade

Precious MetalsPrecious Metals

• Gold occurs as free gold and with sulphide in veins (generally in small fractures in quartz), vein margins and in wall rock associated with iron sulphides and on the margins of rock-fragments

• Au can also contain 15 to 20% weight silver; minor silver sulposalts and tetrahedrites

• Ore-grade mineralization also occurs as disseminated sulphides in altered (carbonatized) rocks along vein selvages

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Geochemistry

• Metallic association: Au, Ag, As, W, B, Sb, Te, Mo >> Cu, Pb, Zn

• Au-Ag ratios range 10:1 to 5:1

• Minor Cr, Ni, Co, V, PGM, Sc, Bi, B

• No vertical metal zoning – case specific

• Secondary minerals – scorodite, jarosite, cerrusite

• Surface geochemistry – Au-As-Ag-Sb >> Pb-Sn-Sc-Fe-Al-Ga

• Drainage geochemistry – Au, As, Ag, Se, Sb, Mo, Hg

• Presence of placers and alluvials suggest nugget gold

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Santa HelenaPembrook Mining Corp.

Key - Structural Control

• Proximity to regional, crustal structures

• Protracted deformation history

• Deposits hosted in second and third-order structures

• Complex deformation history provides many structural trap site geometries, morphologies and geological settings



Structural Control - Anticlinal Closures & Saddle Reefs

Bendigo – 24 Mt @ 14.5 g/t Au (for 11 Moz Au)

Koolhoven & Rosebel deposits at Rosebel



Structural Control – Fault Dilatency

• Present in normal, reversestrike-slip and thrust faults

• Slight warps in the fault plane

• Oblique movement sense

• Lithological heterogeneities

Thrust fault setting Omai (3.7 Moz) Akyem (+5 Moz Au)



Structural Control - Regional Domal Features

Telfer Dome: 1 Bt @ 1.1 g/t Au; 0.4% Cu



Rigid Structures Pressure Shadows

• Structurally-controlled zones of dilation in “pressure shadow” settings adjacent ridge bodies (passive intrusions, more competent and rigid lithologies)

• Sadiola (+10 Moz Au), Cumuru (0.5 Moz Au), Subika & Omai?



Rheological ContrastsPembrook Mining Corp.


Stratigraphy – Reactivity Contrasts

• Structurally-controlled in faults and fold closures, withprecious minerals at redox (carbonates, manganiferous units) boundaries (Sierra Pelada Au-Pd-Pt)

• Fault zone splays in carbonate-saprolite and anintrusive-buttress (?) Sadiola (+11 Moz Au)

Serra Pelada

Sadiola





Stratigraphy - Rheological Contrasts (& Fault)

• Fault propagation along fold axial plane and bedding parallel planesof weakness

• Lithological heterogeneity

• Zones of dilation, extension & pressure shadows

• Maraba, Suriname (+4 Moz); Essakane (+3.1 Moz)

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Mode of Formation

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• Deposits are related to metamorphic fluids from accretionary processes and generated by prograde metamorphism and thermal re-equilibration of subducted volcano-sedimentary terranes

• The deep-seated, Au-transporting metamorphic fluid has been channelled to higher crustal levels through major crustal faults or deformation zones

• Along its pathway, the fluid has dissolved various components - notably gold - from the volcano-sedimentary packages, including a potential gold-rich precursor.

•The fluid then precipitated as vein material or wall-rock replacement in second and third order structures at higher crustal levels through fluid-pressure cycling processes and temperature, pH and other physico-chemical variations.

Mode of Formation

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Favorable Regional & District Targeting Criteria

1. Complex lithostratigraphy with competency contrasts

2. Isolation of competent units within incompetent units

3. Greenschist to greenschist-amphibolite transition facies metamorphism

4. Subjacent to major, crustal-scale structure

5. Lamprophyre and porphyry dikes

6. Fe-rich host-rocks and-or early magnetite alteration

7. Anticlines and domal structures

8. Flexures (dilational jogs) in major structural trends

9. Reactivation of earlier structures especially thrusts by strike-slip movement, either late in the orogenic cycle or as a later overprinting event

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Favorable Regional & District Targeting Criteria

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Favorable Orogenic Gold Terranes

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Latin American Orogenic Provinces

• Las Cristinas-Las Brisas (20 Moz Au)

• Rosebel-Nassau Trend (20 Moz Au)

• Aurora-Omai Trend (10 Moz Au)

• Pataz District (+6 Moz Au)

• Santa Helena (+5 Moz Au)

• Crixas (+3 Moz Au)

• Morro Velho(+ 15 Moz Au)

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Guyana Shield



• Late Paleozoic orogenic sediment-hosted gold belt in theCentral Andes of South America

• Extends for over 3,500 km x 80 km, from Northern Peruthrough Bolivia to Central Argentina

• Several historical and recent +1 Moz discoveries within the established mineral districts

• Orogenic belt is the source for the large auriferous placer deposits – Remi, Madre de Dios & Maranon Basins

• Structurally-controlled gold deposits hosted in Ordovician to Carboniferous granites and Early Paleozoic turbiditic sequences

• Potential for large-scale (+1 Moz Au) vein and disseminated gold deposits


Eastern Andean Cordillera



• Active back-arc rift-basin formed as a rift-basin between the Brazilian Shield and the Arequipa Massif during the Early Paleozoic, infilled by turbiditic sedimentation until the Late Devonian

• Orogenic gold mineralization related to Late Devonian “Eoherciniana” compression (Early Devonian in Central Argentina) and Late Carboniferous (Pataz, Huachon & Amapares intrusions)

• Unexplored potential for intrusion-related mineralization during the Permo-Triassic and Miocene (San Rafael, Antana, Alumbrera, Agua Rica)

• Four distinct magmatic events – Subduction-related Carboniferous granitoids in north-central Peru; Post-orogenic Permo-Triassic; Late Triassic plutons; Miocene stocks in south-central Peru





Mineral Occurrences in Carboniferous Granitoids



CAPAC ORCOInventory 48.5Mt @ 2.04g/t Au for 3.10M ounces

- Mineralization within sequence of Ordovician sedimentary rocks.- Sequence tightly folded with NW-trending axial planes and thrusts.- Host unit is the San Jose Group; slates, mudstones, fine quartzites.- Granitic dikes spatially coincident with mineralization.

- Occurs as series of mantos.- Four mantos over a 500m vertical range.- Can be traced for up to 1400m with average thickness of 10m.- Au with quartz + sulfides (py+pyrh+asp+gn+cp), also free Au.- Control – fold noses, shears and thrusts

SANTA HELENA


Au 8.08g/tAssociated with Fe-filled fractures

Au 1.61g/tAu with quartz vein

Au 1.66g/tAu with Fe-filled breccia

Au 15.9g/tAu with Fe-filled fractures

Au 1.16g/tAu with quartz veinlets

SANTA HELENA

Pembrook Mining Corp.SANTA HELENA – OLLACHEA

EMERGING GOLD DISTRICT

OLLACHEAPotential ?

- Area of extensive informal mining since colonial times.- Mineralization related to sheeted quartz-sulfide veins and veinlets.- Mineralization associated with pyrrhotite (magnetitic).- Previous drilling by junior explorer in 1998:

129m @ 0.74g/t Au 51m @ 0.56g/t Au 74m @ 1.04g/t Au 71m @ 0.46g/t Au 44m @ 0.90g/t Au

- MIRL work. Community agreements in place. 9 holes drilled 2008. Metallurgical test program in 2009.

2.5235.69 0.20 1.49 0.48 0.85 0.45 7.7619.94 0.50 1.76 1.45 1.95 2.46 2.26 2.59 2.45 0.36 0.46 2.15 2.45 0.96 0.85

2.521.040.490.310.450.261.002.540.312.101.242.560.420.998.720.522.100.620.291.572.442.100.954.860.345.122.74

Drill hole Assay results

Gold g/tSamples

1m intervals(note: intervals with <0.2 g/t not noted)


SANTA HELENA – OLLACHEA (MIRL) EMERGING GOLD DISTRICT

DDH-08-04113m @2.30g/t from 88-162m

DDH08-03 DDH08-02 DDH08-22 DDH08-04 DDH08-01 DDH08-05 DDH08-23

102m @ 1.83

126m @ 2.30

70m @ 2.00

122m @ 2.9594m @ 3.02

All data from MIRL wesite


SANTA HELENA – AYAPATAEMERGING GOLD DISTRICT

AYAPATAPotential

+1M ounces

- Folded and sheared clastic sediments- Stratabound sheeted zone veins/veinlets of qtz-ser-py-aspy- Gold zone within siltstone immediately beneath graphitic shale- Mineralized zone with 3km of strike and thickness from 25-95m

Black shale

0

100 m

Shale, slate, siltstone

Black shale

Quartzite

Gold Zone30-90 meters thick

Best surface geochemistry 100m @ 1.3g/t Au

Best drill intercept 110m @ 1.1g/t Au


SANTA HELENA – AYAPATAEMERGING GOLD DISTRICT

DRILL RESULTS (1997)APD-1 7m @ 2.98g/t from 42-49mAPD-2 1.6m @ 32.80g/t from 102-103.6mAPD-2A 16m @ 0.99g/t from 107-123mAPD-3 10m @ 1.35g/t from 73-83mAPD-4 33m @ 1.85g/t from 61-94mAPD-5 69m @ 1.86g/t from 71-140m

84870008488000

381500 382500380500

8487000

381000 382000 383000

9.109.101.21.2

3.43.4

5.65.6CC

FF GG

AA

Trench D40m @ 0.60 g/t

Trench B45m @ 3.60 g/t

Trench C95m @ 0.56 g/t

Trench E65m @ 1.28 g/t

Trench A127m @ 1.40 g/t

Trench G70m @ 1.26 g/t

DD

BB

Trench F127m @ 1.31 g/t

Black graphitic shale

Mineralized zone

Proposed drill holes

TrenchC

TrenchD

TrenchE

TrenchF

TrenchG

95m @ 0.56 g/t

40m @ 0.60 g/t

65m @ 1.28 g/t

100m @ 0.866 g/t

50m @ 0.168 g/t

100m @ 1.310 g/t

70m @ 1.26 g/t


SANTA HELENA – HIGH GRADEEMERGING GOLD DISTRICT

- Narrow (2-50cm), high-grade (15-150g/t Au)- Quartz-carbonate veins- Milky quartz with iron oxide; free gold- “white clay” wall rock alteration????

Penon de Oro

- Small, Au-bearting quartz veins with associated colluvial and alluvial workings- High-grade gold (10-100g/t Au)- “Sheeted ladder” veins in fold closures

Yanacocha

EASTERN CORDILLERA OROGENIC GOLD DEPOSITSPOTENTIAL FOR

SMALL, RICH, HIGH GRADELARGE VOLUME, BULK MINEABLE LOW GRADE

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San Francisco

Pembrook Mining Corp.EASTERN CORDILLERAN

PATAZ

Orogenic Gold Belt – 160km long in Eastern CordilleraNW-trending, 1-5km wide corridor associated with the Pataz Batholith (Miss)Quartz veins within, and on margin of batholith and in Ordovician phyllitesGeochemical assemblage Au-Ag-As-Fe-Pb-Zn+Cu,Sb,Bi,Te,WThree distinct phases of vein filling (1) quartz-pyrite-arsenopyrite-ankerite (2) quartz-galena-sph-ccpy-Sb sulfosalts-Electrum-Gold (3) calcite-dolomite-quartzShoots average 7-15g/t Au and Ag to 120g/tPataz Batholith 329my; Gold mineralization 312my

PRODUCED 6M Oz; Potential +10M oz

Tertiary Volcanics

Mesozoic SandstoneLimestone

Ordovician SlateQuarzite

Cambrian - Ordovician SandstoneVolcanics

Late Proterozoic PhylliteCambrian Schist

Mississippian to Triassic Sandstone (Mitu)LimestoneSiltstone / Sandstone (Ambo)

Mississippian Pataz Batholith

Papagayo

Consuelo

Pataz

Ariabamba

Culebrillas

El Gigante

Buldibuyo

Estrella



• Integrated and systematic exploration approach

Regional & District Exploration

• Challenges – topography, vegetation cover, isolation

• Discriminate prospective from non-prospective areas

• Understanding the structure architecture and lithological sequences (the geology) – existing maps, satellite Imagery (topography, Landsat), magnetics-radiometrics

• Presence of gold occurrences (Use of Imagery)

• Drainage anomalies – Discriminate primary sources contra secondary sources


Exploration

Orogenic Gold Deposits - Pembrook Resources

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