F Ccp = (Cu wr )/ (Cu Ccp ) (1) In the first iteration all of the Ni was assigned to pentlandite. F Pn = (Ni wr )/ (Ni Pn ) (2)

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1 Online resource C: Method to determine the proportion (in wt.%) of each element hosted by pyrrhotite, pentlandite, chalcopyrite, pyrite and the precious metal minerals (PMM) used by Dare et al. in Chalcophile and platinum-group element (PGE) concentrations in the sulfide minerals from the McCreedy East deposit, Sudbury, Canada and the origin of PGE in pyrite, Mineralium Deposita, DOI /s These calculations are based on those of Godel et al. (2007), Barnes et al. (2008) and Dare et al. (2010b). They require 1) concentration of each element in the whole rock (Table 1), 2) the weight fraction (in wt.%) of each mineral phase (Table 1), as determined from whole rock geochemistry and image analysis described below, and 3) the average concentration of each element in each sulfide phase (Tables 3, B and C1) and PMM phase (Table C2). The weight fraction (F) of pyrrhotite (Po), pentlandite (Pn) and chalcopyrite (Ccp) was calculated for each sample using whole rock (wr) Cu, Ni and S and the SEM data (Table C1). The amount of chalcopyrite present is F Ccp = (Cu wr )/ (Cu Ccp ) (1) In the first iteration all of the Ni was assigned to pentlandite F Pn = (Ni wr )/ (Ni Pn ) (2) The contribution of Ni from minor amounts of accessory pyrite, silicate minerals (pyroxene, quartz, plagioclase, amphibole, biotite, chlorite) and a moderate amount (8 22 wt.%) of magnetite, which at Sudbury contains ~ 0.15 wt% Ni (Dupuis and Beaudoin 2007), is considered negligible (< 1%) but the contribution of Ni in pyrrhotite is taken into consideration below. The modal fraction of accessory pyrite (Py) and magnetite (Mt) was determined using image analysis (Image Pro Plus version 6.2) over the scanned images of the entire polished block, because the weight fraction of these Fe-rich minerals is not easily calculated from the geochemical data. Pyrrhotite, pentlandite and chalcopyrite were grouped together as one phase to facilitate the image analysis. Pyrite grains were carefully traced over in a bold color in Corel Draw to aid the selection of this phase during image analysis. Precision of the image analysis, based on 4 repeat analyses of the same image, is < 10%. The modal fraction was then calculated

2 to weight fraction taking into account the different densities (D) of the minerals (Table C3) as follows Weight F x = Modal F x * D x /D sample (3) Where x = mineral phase and D sample is the bulk density of the sample which is approximately 4.5 for these massive sulfide samples. The remaining S was attributed to pyrrhotite using the following equation F po = (S wr S Ccp *F Ccp S Pn *F Pn S Py *F Py )/S Po (4) The weight fraction of pentlandite is then corrected to account for the minor amount of Ni (0.6 wt.%) in pyrrhotite using Fpn = (Ni wr - F Po * Ni Po )/ (Ni Pn ) (5) The weight fraction of pyrrhotite (equation 4) is then recalculated using this new value for the weight fraction of pentlandite obtained from equation 5. Without taking this into account the weight fraction of pentlandite is overestimated by ~ 10%. A comparison of the two methods (geochemical and image analysis) used to determine the total weight fraction of sulfides indicates that the polished blocks and thin sections are representative of the hand specimen used in the geochemical analysis because they are similar to within 15% relative difference. The modal fraction of each PMM (F PMM ) was calculated for the entire sample suite of 7 sections, in order to minimize the problem of the heterogeneous distribution of the PGM in the samples, using F PMM = total V PGM / total V Sample (6) Where total V PMM = total volume of PMM and total V Sample = total volume of sample. As no information is available on distribution or size of the PGM in the third dimension we have made the assumption that the volume represented by each phase is approximated by its area, following the method of Godel et al. (2007). The areas of the PMM grains were calculated from length x breadth measurements of each grain taken from the SEM image (Table 2). The total area of 6 round polished blocks (diameter 2.1 cm) and 2 thin sections (2 x 3 cm) is µm 2.

3 The modal fraction was then converted into weight fraction using equation (3) and densities given in Table C3. The proportion (%) of each element in each sulfide and PMM phase was calculated by 100* F x C x /C wr (7) Where F x = weight fraction of phase x as calculated above. C x = concentration of each element in phase x, C wr = concentration of each element in the whole rock (Barnes et al. 2008). The results are presented in Table 4 and Table B in Online Resource B. The combined error for the whole rock and LA-ICP-MS analyses close to the detection limits makes it difficult to provide an accurate mass balance for some elements (e.g., As, Os, Ru and Sb) and thus they are not reported. The values for Pd in pentlandite are an average of medium-grained veinlets and coarse-granular varieties based on the fact that the Pd content of pentlandite decreases from coarse-granular to medium-grained veinlets to negligible Pd in pentlandite flame exsolutions (Dare et al. 2010b). Table C1 Scanning electron microscope results for pyrrhotite, pentlandite, chalcopyrite and pyrite from the Main and West orebodies of McCreedy East deposit. Cobalt in accessory pyrite is determined by the electron microprobe. Sulfide Mineral S Fe Co Ni Cu Total S Fe Co Ni Cu wt.% wt.% wt.% wt.% wt.% wt.% at.% at.% at.% at.% at.% Pyrrhotite-rich sulfides from the Main orebody (N=5) Pyrrhotite ave bdl 0.6 bdl bdl 0.4 bdl (n = 15) stdev Pentlandite ave bdl bdl (n = 13) stdev Chalcopyrite ave bdl n.a bdl bdl 24.4 (n = 5) stdev Accessory Pyrite ave bdl bdl bdl bdl (n = 25) stdev n.a. n.a. 0.6 n.a. n.a. n.a. n.a. n.a. 0.4 n.a. n.a. Pyrite-rich sulfide from the altered West orebody (N=1) Massive Pyrite ave bdl bdl bdl bdl (n = 8) stdev Pyrrhotite ave bdl 0.7 bdl bdl 0.5 bdl (n = 9) stdev Pentlandite ave bdl bdl (n = 8) stdev Comparison with Sudbury sulfide data (wt.%) from the the Main orebody of the McCreedy East deposit (N=10, Gregory 2005): Pyrrhotite: S , Fe , Ni ; Pentlandite: S , Fe , Co , Ni ;and from the 402 Trough of the Creighton deposit (N=19, Dare et al. 2010b): Pyrrhotite: S 39.7, Fe 59.4, Ni 0.7; Pentlandite: S 33.6, Fe 29.6, Co 1.2, Ni 35.6; Chalcopyrite: S 35.2, Fe 30.7, Cu 33.7; Pyrite: S 53.7, Fe 42.2, Ni wt. weight, at. atomic, ave average, stdev 1 standard deviation, N number of samples, n number of grains analyzed, bdl below detection limit, n.a. not analyzed, Eu euhedral, An anhedral, Msv massive

4 Table C2 Representative scanning electron microscope analyses (wt.%) on precious metal minerals (PMM) from the McCreedy East Deposit, Sudbury PMM Host Sample No. Fe Ni Pd Te Pt Bi As Ag Au Total Atomic formula Moncheite Po MCR3_ (Pt 0.94 Pd 0.06 ) Σ1.00 (Te 1.51 Bi 0.49 ) Σ Moncheite Po/Pn MCR5A_ (Pt0.70 Pd 0.25 Fe 0.07 ) Σ1.01 (Te 1.48 Bi 0.51 ) Σ Moncheite Plag/Po MCR4B_ (Pt0.80 Pd 0.18 Fe 0.04 ) Σ1.02 (Te 1.72 Bi 0.25 ) Σ Moncheite Plag MCR4B_3b (Pt0.52 Pd 0.47 Fe 0.06 ) Σ1.04 (Te 1.71 Bi 0.25 ) Σ1.96 Moncheite Po MCR4B_ (Pt 0.90 Fe 0.26 Pd 0.03 ) Σ1.18 (Te 1.60 Bi 0.22 ) Σ Moncheite Ep MCRE1_ (Pt0.47 Ni 0.31 Pd 0.24 ) Σ1.00 (Te 1.72 Bi 0.27 ) Σ Merenksyite Py MCRE1_ (Pd0.53 Pt 0.46 ) Σ0.99 (Te 1.77 Bi 0.24 ) Σ Pt-Pd-melonite Po/Py MCR2_ (Ni0.37 Pt 0.37 Pd 0.22 Fe 0.13 ) Σ1.10 (Te 1.58 Bi 0.32 ) Σ1.90 Pd-Pt-melonite Po/Chl MCRX_ (Ni 0.41 Pd 0.36 Pt 0.27 Fe 0.12 ) Σ1.16 (Te 1.77 Bi 0.24 ) Σ Michenerite Po MCR5B_ (Pd1.02 Pt 0.09 ) Σ1.11 Bi 0.94 Te 1.00 Michenerite Po/Pn/Mt MCR3_ Pd 1.04 Bi 0.90 Te Sperrylite Po/Bi MCR3_ Pt1.07 As 1.93 Electrum Pn MCR3_ Ag 0.95 Au 1.75 Numbers 1-8 identify the analyzed grains in Figure 6 Po pyrrhotite, Pn pentlandite, Ccp chalcopyrite, Py pyrite, Mt magnetite, Plag plagioclase, Ep epidote, Chl chlorite, Bi biotite, No. number Formula of PMM from Sudbury for comparison with this study: Ag 1.04 (Au 1.91 Hg 0.06 ) Σ electrum from Creighton deposit, Dare et al. (2010a) (Pd 0.99 Ni 0.01 ) Σ1.00 (Bi 0.79 Sb 0.13 ) Σ0.92 Te michenerite from South Range mines, Cabri and Laflamme (1976) Pt 1.00 (As 1.99 Sb 0.01 ) Σ sperrylite, Cabri and Laflamme (1976). (Pd 0.92 Pt 0.07 Ni 0.01 ) Σ1.00 (Bi 0.99 Sb 0.01)Σ1.00 Te michenerite from a North Range mine, Cabri and Laflamme (1976) (Pt 0.97 Au 0.03 ) Σ1.00 (As 1.93 Sb 0.03 ) Σ sperrylite from Creighton deposit, Dare et al. (2010a)

5 Table C3 Density of each mineral phase and composition of the precious metal minerals (averaged from Table C2) used in the calculation Mineral Density Pt Pd Bi Te Au Ag (g/cm 3 ) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) Pyrrhotite 4.6 Pentlandite 4.8 Chalcopyrite 4.2 Pyrite 5.0 Magnetite 5.2 Plagioclase 2.7 Hypersthene 3.6 Quartz 2.6 Augite 3.4 Average Silicate 3.1 Moncheite Merenskyite Melonite Michenerite Sperrylite Electrum