RO CKS TO R I CH E S GEOFILE 2004-6: Platinum-Group Elements in Alkaline Cu-Au Porphyries Contact Information 1 2 3 2 2 Graham Nixon , Louis Cabri , Gilles Laflamme , Paul Sylvester and Mike Tubrett Canada (250) 952-0448 1 2 3 [email protected] B.C. Geological Survey Memorial University of Newfoundland Natural Resources Canada CANMET-MMSL

INTRODUCTION LAM-ICP-MS RESULTS Pyrite Selected Cu-Au-Ag+/-PGE Porphyry Deposits and Alkaline intrusions of Late Triassic to Early Jurassic age are important hosts to porphyry-style The laser ablates material at the rate of ~1 micron per second and leaves craters An important Prospects in BC Cu-Au-Ag+/-PGE mineralization in British Columbia. The main deposits and prospects occur Galore Ck ~100 microns across (right). The ablated material is continuously passed into the in the accreted magmatic arc terranes of Quesnellia and Stikinia. The economic potential of plasma torch and analyzed over ~1 second intervals for the isotopes (elements) of Lorraine repository for PGE in Terranes these systems has not been fully evaluated due to the paucity of data relating to the tenor and interest. Raw data for selected trace elements are shown in time-resolved laser d10 distribution of the PGE, a potentially important by-product of Cu-Au ores. Mt Milligan Cache Creek drilling profiles for pyrite, and bornite in various deposits. The profiles alkaline Cu-Au Quesnellia reveal the chemical variation with depth in the sulphide grain. Mt Polley Stikinia Platinum-group and PGE-bearing sulfides in selected deposits have been analyzed Secondary electron images (SEI) of LAM-ICP-MS ablation using the Electron Microprobe and Laser Ablation Microprobe fitted with an Inductively craters in chalcopyrite (cp) with inclusions of apatite (ap) porphyry systems? Afton-Ajax Coupled Plasma Mass Spectrometer (LAM-ICP-MS) capable of analyzing PGE and other and magnetite (mag). [Sappho 01GNX12-2-5] elements at ppm to sub-ppm abundances. Analytical results for 7 samples from Afton, Similco Maple Leaf Lorraine, Copper Mountain (Similco), Friday Creek, Sappho and Maple Leaf (Averill Complex) Main Features Friday Ck Sappho are presented below. > Smooth profiles represent elements in solid solution Afton in the sulphide phase Afton Chalcopyrite (06c13cp) 1000000 ACKNOWLEDGMENTS > Erratic profiles represent compositional zoning and/or d 100000 S 34 Opaque Minerals in Analyzed Samples of Cu-Au Porphyry Deposits n o As 75 This study is funded in part by the “Rocks to Riches” program submicroscopic inclusions c

Optical and Electron Microscopy e Ag 107

S 10000 r

e Background Pd 108 (BCYCM), a cost-sharing agreement between the Mining and

py p cp Sb 121 > s 1000 Opaque minerals identified in the small suite of samples analyzed by Note that erratic metal profiles generally lack any t n Pt 195 Sciences Laboratories, CANMET and B. C. Geological u

LAM-ICP-MS are listed in the table (right). The PGM identified to date correlation with sulphur (implying solid solution or o 100 Au 197 C are mainly Pd-tellurides and -antimonides (typically 10-20 microns the presence of alloys/inclusions) Survey, and a NSERC operating grant to Paul Sylvester. 10 across) which occur as inclusions in the Cu-Fe sulphides. Examples of 0 20 40 60 80 100 120 mineral associations and textures are shown in the photomicrographs. TimTimee (s e(seconds)conds) [D [Depth]epth] Lorraine Pd, Pt, Ag, Au, and Sb in solid solution; [Lorraine 01GNX32-2-1] [Copper Mtn 03GNX1-11-4] Lorraine Bornite (06F09) some Au inclusions (49 and 86s) PGE ABUNDANCES 1000000 Afton Chalcopyrite (06d16cp) d 100000 n 1000000 o S 34

c Role of Pyrite

e As 75

S 10000 d r Background Ag 107 100000 n

[Afton 01GNX19-26-1] e S 34 o p Pd 108 c

s 1000 As 75

e Data for metal concentrations in the t Te 125 PGE in Pyrite

S 10000 Circle = 0.1 mm in diameter n Pt 195 Pd 106 r u Background e o Au 197 Ag 107 various sulphide species are shown in

100 p C Sb 121

s 1000 t the bar charts. Each bar represents one

n Te 125 Sites of LAM-ICP-MS ablation craters 10 u Pt 195 o 100 Afton C time-integrated analysis over an in chalcopyrite (cp) and pyrite (py). 0 20 40 60 80 100 120 Au 197 TTimeime (seconds) (seconds ) [Depth] [Depth] inclusion-free interval. 10 42 ppm 00 2020 4040 6060 80 10 1000 12 1200 Altaite (alt) and (hs) in Grains of mertieite II (M) associated Ag,Te in solid solution; Au inclusions TTimeime (seconds) (seconds) [Depth] [Depth] The LAM-ICP-MS results demonstrate: bornite (bn) associated with with tetrahedrite (tt) in bornite (bn) (65 and 92s); no significant PGE in muscovite (ms), gypsum (gp) and chalcopyrite (cp). solid solution Pd, Ag, Sb, Te in solid solution; Pd-As > The PGE occur in solid solution in the Sappho and sodalite (sdl). (42s) and Pd-Te (66s) inclusions; Au main sulphide minerals and show no Sappho Copper Mtn inclusions (74, 87, 95s) marked correlations with other metals [Copper Mtn 03GNX1-8-1] [Lorraine 01GNX32-2-1] [Friday Creek 01GNX35-3-10] Afton Pyrite (06c16py) > Pyrite may be significantly enriched Copper Mtn Pyrite (05c03py) 1000000 Sappho Pyrite (05e12py) Cu Mtn (1) 100000 in PGE (up to 42 ppm Pd) relative to 10000000 (Similco) Pt ppm 100000

S 34 d

d S 34

n co-existing Cu-Fe sulphides

d 1000000

n Pd ppm 10000 o n

o Ag 107 c o c S 34 e 10000 Ru 102 c e 100000 Pd 108 S e Ag 107 Background S r Background S

e Rh 103 Pd 108 r Sb 121 > p e r 1000 Part of the PGE budget resides in p e 10000 Sb 121 Te 125 s 1000 t Pd 108 0 5 10 15 20 p s

Background n t

s Pt 195 Pt 195 u discrete platinum-group minerals, n t ppm

1000 o

u Pt 195 n Au 197

100 Au 197 C o u 100 o Bi 209 C Bi 219 notably PGE-tellurides, -antimonides

C 100

10 10 and -arsenides (as inferred by EPMA 10 [Copper Mtn 03GNX1-11-4] 0 20 40 60 80 100 120 0 20 40 60 80 100 120 PGE in Chalcopyrite 0 20 40 60 80 100 120 and LAM-ICP-MS). Time (seconds) [Depth] Inclusion of galena (gn) associated Time (seconds) [Depth] Time (seconds) [Depth] Time (seconds) [Depth] Euhedral grain of carrolite (car) in Inclusions of merenskyite (mer) and Inclusions of merenskyite (mer), Time (seconds) [Depth] 4.9 ppm with pyrite (py), both encapsulated Afton bornite (bn) associated with Pd-Pt-bearing melonite in bornite and PGE, Ag, Sb, Bi in solid solution; Au in solid Pd, Au, Ag, Sb and Te in solid solution PGE in Bornite in chalcopyrite (cp). temagamite (tg) and galena (gn) PGE in solid solution; Pd erratic (zoned?) chalcopyrite (cp) and biotite (bt). secondary Cu sulphides(bn+) associated with bornite (bn), K- solution and forming inclusions (47 and 94s) surrounded by albite (ab), diopsidic feldspar (K-spar) and biotite (bt). Copper Mtn Pyrite (05c16py) Afton Pyrite (06c16py) Maple [Copper Mtn 03GNX1-8-1] Sappho Pyrite (05d16py) Leaf [Afton 01GNX19-26-1] pyroxene (px) and magnetite (mag). 100000 1000000 1000000 Friday d [Lorraine 01GNX32-2-1] [Friday Creek 01GNX35-3-10] d Creek

n 100000 d 100000 n 10000 S 34 o n o c c o S 34 Background S 34

e As 75 e c Sappho e S Ag 107 S Ag 107 10000

S 10000 r r Ag 107 e e r Background Pd 108 1000 Pd 108 Background e p Pt 195 p Sb 121 p Sb 121 s

s 1000 t t

s 1000 Au 197 Te 125

t Pt 195 n n n u Au 197 100 Bi 209 u u o o Au 197 100 o C 100 Bi 209 C C Cu Mtn (2) Cu Mtn (2) 10 10 (Similco) (Similco) 10 0 20 40 60 80 100 120 0 20 40 60 80 100 120 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Time (seconds) [Depth] Time (seconds) [Depth] TimeTime (seconds) (seconds ) [Depth][Depth] Time (seconds) [Depth] Time (seconds) [Depth] Pt ppm Lorraine Pt ppm Cu Mtn (1) Backscattered electron image BEI of coarse and fine-grained PGE, Ag, Sb, Bi, Au in solid solution; High Pt does not correlate with Pd, Ag, Bi Au in both solid solution and inclusions Pd ppm (Similco) Pd ppm (BEI) of a small inclusion of electrum (Au) in chalcopyrite note concordant zoning of Bi and Ag (and Sb, As, Te) in solid solution (56, 64, 80s) 0 1 2 3 4 5 0 1 2 3 merenskyite (mer) in pyrite (py). (cp) and gangue (G). ppm ppm

[Afton 01GNX19-26-1]