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1
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
2
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
17
17
17
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
3
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
4
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
5
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
6
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
7
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
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
8
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)
9
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
Grid Map of Western Portion of the Legris Lake Complex
10
Heterolithic Breccia
Clinopyroxenite Breccia
11
Igneous Layering in the Legris Lake Complex
Cu-Ni-PGE Mineralization
• Occurrence and distribution• Mineralogy• Metal concentrations• Mineralization models• Comparison to other deposits
12
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)
13
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
14
Photomicrograph of Cu-Ni-PGE Mineralization
Millerite
PdS
Cpy
Epd
PdS
15
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)
16
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
17
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
18
Pt/(Pt+Pd) vs Cu(Cu+Ni)
0
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
19
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