Geology and Cu-Ni-PGE Mineralization of Legris Lake...

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Geology and Cu-Ni-PGE Mineralization of

Legris Lake Complex

PLACER DOME

Neil Pettigrew and Keiko Hattori

Contents

• Regional geology• Recent exploration History• Geology of the Legris Lake Complex• Characteristics of the Cu-Ni-PGE

mineralization• Comparison to other Cu-Ni-PGE

deposits

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Regional Geology

Canada U.S.A

Proterozoic Cover

Felsic Intrusive Rocks Mafic and Felsic Volcanic Rocks

Metasediments

Ultramafic-Mafic Intrusive Rocks

Alkaline Intrusive Rocks

Major Fault Subprovince Boundary Highway

Archean

Quetico Subprovince

Wawa Subprovince

Wabigoon Subprovince

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17

17

11

11

11

Stawson Lake

Redhornse Lake

Classical Quetico Intrusion

Lac Des Milles Lac

Rainy Lake

Lac Des Illes

Demar Lake

Legris Lake

Tib Lake

Buck Lake

Dog Lake

Fort Francis

Lake Superior

Shebandowan Lake

Rainy Lake

Atikokan

Upsala

Thunder Bay

Samuels Lake

0 10 20 30 40 50

Garden-ObongaAeromagnetic Map

Legris Lake Property

Tib Lake Gabbro

Demars Lake Intrusion

Legris LakeComplexLac des Iles Mine

Wakinoo Lake Intrusion

Dog River IntrusionLac des Iles Complex

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0 5kilometres

Lac desIles

Legris L.

diabasegranite, gneissultramafic complexgabbro, norite, dioritesandstonevolcanics, iron formationhighway, access roadPGE deposit, occurrence

, iron formation

527

527LakeSuperior

ThunderBay

527

LEGRISLAKE

LAC DES ILES

S

S

S

S

S

SS

S

SS

S

S

S

S

PGM

PGM

MAPM/EWR

PGM

PDL

NCS

CGG

PDLAVL/SOE

PDLFNX

AVL = Avalon Ventures Ltd.SOE = Starcore Resources Ltd.BUC = Buck Lake Ventures Ltd.CGG = Canadian Golden Dragon Resources Ltd.EWR = East West Resource CorporationFNX = Fort Knox Gold CorporationHLM = Houston Lake Mining Inc.MAPM = Maple Minerals Inc.NCS = New Claymore Resources Ltd.PGM = New Millenium Metals Corp.PDL = North American Palladium Ltd.

BUC

HLM

PDL

3.92 g/tPd+Pt+Au

WAKINOOLAKE3 g Pt

TAMANLAKE

BUCK LAKE2.9 g Pd, 2 g Pt

TIB LAKE1.1 g Pd, .2 g Pt LAC DES ILES REGION

Map compiled by Avalon Ventures Ltd.Accuracy is not guaranteed. Dec 2000

Avalon/Placer/Starcore

Legris Lake JV

DOG RIVERINTRUSION

0 20

km

NA PalladiumLac des Iles Mine

145.6 million tonnes1.86 g/t Pd+Pt+Au

DEMARS LAKE2.6 g Pd, .3 g Pt

2.83 g/t Pt+Pd+Au

DEMARS LAKE2.6 g Pd, .3 g Pt

7.74 g/t Pt+Pd+Au

2.28 g/t Pt+Pd+Au

Recent Exploration History

• 154 km of line cut• 136 km of ground based magnetometer surveys• 88 km of I.P. surveys• 97 km of grid mapping• 945 prospecting samples collected• 1500 m of diamond drilling• Currently conducting 3rd phase of trenching

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Geology of the LegrisLake Complex

• Divided into four zones:Central ZoneEastern Border ZoneSouthwestern Border ZoneNorthwestern Border Zone

Central Zone

• Well exposed• Consists almost entirely of massive,

homogenous 5ab leucogabbro• Magnetic and I.P. surveys, however

suggest much more complexity at depth

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8 Diabase (Proterozoic)

7 Granitic

6 Dioritic

4 Igneous Breccia

Heterolithic Breccia

Clinopyroxenite Breccia

5 Gabbroic

Leucogabbro

Main Showing Subtype 5a*

Biotite-rich Subtype 5ab

Mesogabbro 5b

Melanogabbro 5c

3 Ultramafic

Clinopyroxenite 3a

Wehrlite, Dunite 3b 3c

2 Metasedimentary Rocks

1 Metavolcanic Rocks

Iron Formation

LEGEND

2

21

1 kilometre

Legris Lake

Poplar ZoneTrenches

Main Showing Trench

AvalonCamp

I F

I F

I F

5ab Leucogabbro

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Eastern Border Zone• Poorly exposed• Comprises most leucogabbros, but also

meso to melanogabbros and pyroxeniteswith minor breccia

• Contains large hanging wall metasediments tongues, extending up to 600 metres into the complex

• In contact with metasandstone and iron formation

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7 Granitic

6 Dioritic

4 Igneous Breccia



5 Gabbroic

Leucogabbro



Mesogabbro 5b

Melanogabbro 5c

3 Ultramafic

Clinopyroxenite 3a




Iron Formation

LEGEND

2

21

1 kilometre

Legris Lake

Poplar ZoneTrenches

Main Showing Trench

AvalonCamp

I F

I F

I F

Southwestern Border Zone

• Lacks abundant breccia• Hosts the largest 5a* leucogabbro

(main showing subtype) body yet discovered

• Hosts a zoned ultramafic dyke-like body with a dunite core containing semi-massive magnetite

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Northwestern Border Zone• Poorly exposed• Experienced many phases of dioritic

to pyroxenitic intrusions and multiple brecciations

• Consists mostly of heterolithic breccia• Developed igneous layering in several

phases• Hosts all currently known Cu-Ni-PGE

mineralization and the majority of the 5a* leucogabbro (main showing subtype)

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7 Granitic

6 Dioritic

4 Igneous Breccia



5 Gabbroic

Leucogabbro



Mesogabbro 5b

Melanogabbro 5c

3 Ultramafic

Clinopyroxenite 3a




Iron Formation

LEGEND

2

21

1 kilometre

Legris Lake

Poplar ZoneTrenches

Main Showing Trench

AvalonCamp

I F

I F

I F

Grid Map of Western Portion of the Legris Lake Complex

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Igneous Layering in the Legris Lake Complex

Cu-Ni-PGE Mineralization

• Occurrence and distribution• Mineralogy• Metal concentrations• Mineralization models• Comparison to other deposits

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0 2

kilometres

LegrisLake

NORTH AMERICANPALLADIUM

AVL/SOE

LEGRIS LAKE HIGHLIGHTS

4.92 m1.21 g/t

9.95 mg/t3.16

9.95 mg/t3.16

core lengthPd+Pt+Au

0.77 mg/t1.11

10.70 m1.62 g/t

12.00 m0.86 g/t

Legris Lake Complexdiabase, granite, gneissmagnetic highAvalon 2000 drill hole

0 5kilometres

527

PDL

AVL/SOE

Powder Hill Zone

NA PalladiumLac des Iles

145.6 mt1.86 g/t PGE

LEGRIS LAKEPROPERTY

5a* Leucogabbro (Main Showing Subtype)

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Cross Section of The Northwestern Border Zone

10m of 3.16g/t PGEs0.42% Cu, 0.13% Ni

0.77m of 0.53g/t Rh0.91g/t Pd 0.19g/t Pt 0.01% Cu, 0.07% Ni

Main Showing, 5a* Leucogabbro

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Photomicrograph of Cu-Ni-PGE Mineralization

Millerite

PdS

Cpy

Epd

PdS

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High Rh, Low Cu, Leucogabbro

Semi-massive Magnetite

Metal ConcentrationsPt/Pd ratio >100 ppb PGEs

01234567

1.00

0.94

0.88

0.82

0.76

0.70

0.64

0.58

0.52

0.46

0.40

0.34

0.27

0.21

0.15

0.09

0.03

Pt/Pd ratio

freq

uenc

y

Cu/Ni ratio >1 g/t PGEs

0.00.51.01.5

2.02.5

3.03.5

5.0 4.7 4.4 4.1 3.8 3.5 3.2 2.9 2.6 2.3 2.0 1.7 1.4 1.1

Cu/Ni

frequ

ency

Pd vs Cu

10

100

1000

10000

100 1000 10000

Cu (ppm)

Pd (p

pb)

Cu vs Ni

10

100

1000

10000

100 1000 10000

Cu (ppm)

Ni (

ppm

)

Au vs Pt+Pd

1

10

100

1000

10000

100 1000 10000Pt+Pd (ppb)

Au

(ppb

)

Total PGEs vs Cu+Ni

100

1000

10000

100 1000 10000 100000Cu + Ni (ppm)

Tota

l PG

Es (p

pb)

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PGE Concentration in a Fractionating Silicate Melt

S-Saturated

Pd, S, Cu

Ni

Pd, Cu, SPt

Ir, Os, Ru

S-Undersaturated

Con

cent

ratio

n of

E

lem

ent i

n S

ilica

te M

elt

Crystalization

• Very similar style of mineralization and geology to the Powder Hill and VandeZones southwest of Legris Lake Complex

• Similarities to Lac des Iles and River Valley mafic-ultramafic complexes include:

Rock TypesAbundant igneous Breccias Cu-Pd-rich Cu-Ni-PGE mineralization

Comparison to other Cu-Ni-PGE Deposits

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Stinger Zone 7.74 g/t PGEs

Vande Zone 2.23 g/t PGEs

Stocker Zone 2.80 g/t PGEs

Poplar Zone 3.92 g/t PGEs

Powder Hill Zone 2.83 g/t PGEs

Lac des Iles Mine145 million tones

1.86 g/t PGEs

Powder Hill Zone Mineralized Leucogabbro

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Pt/(Pt+Pd) vs Cu(Cu+Ni)

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0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Cu/(Cu+Ni)

Pt/(P

t+Pd

)

Pt+Pd+Au >1000ppb Pt+Pd+Au <1000ppb, >100ppb

Lac des Iles

Komatiite-hostedDeposits

Sudbury

Tholeiitic-hostedDeposits Quetico

Intrusions

RathbunLake

Coldw ell

Modified after Naldrett and Cabri 1976, Michaud 1998, MacTavish 1999.

Summary 1• The Legris Lake Complex is comprised

mostly of 5ab leucogabbro and appears to be at a shallow level of erosion

• The northwestern border zone is characterized by numerous gabbroic intrusive and brecciation events

• The system, however, remained stable enough between brecciations to allow crystal fractionation to occur producing igneous layering in several phases

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Summary 2• The Legris Lake mineralization is Cu and

Pd-rich and occurs in coarse grained 5a* leucogabbro bodies with melanogabbro to clinopyroxenite bases

• A second style of Rh-rich and Cu-poor mineralization occurs

• The Cu-Ni-PGE mineralization is very similar to the Vande and Powder Hill zones to the southwest

• The geology of the Legris Lake Complex also bears similarities to the Lac des Iles and River Valley mafic-ultramafic complexes

Geology and Cu-Ni-PGE Mineralization of Legris Lake...

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