Abstract:

The WD-16 INCO deposit, a contact-type Ni-Cu sulphide ore deposit, is located approximately 700m northwest of Joe Lake on the North range of the Sudbury Igneous Complex, Sudbury, Ontario. Two types of mineralisation are observed: (1)massive sulphide pods and veins and (2)disseminated sulphide, which are present both in the hangingwall and footwall environments. Current reserves lie up to 100m below surface, containing at least 500,000 tonnes. The sulphide phases present (estimated abundances) in the deposit are pyrrhotite (89%), pentlandite (9%), chalcopyrite (2%) and pyrite (accessory). Modal pentlandite up to 30% is occasionally observed within massive sulphide. Normalised (to 100% sulphide) Ni content is uniform across the orebody at 3.67 wt.%. Normalised Cu contents are low, averaging 1.16 wt.%, and generally rise at the base of the orebody whilst highest Co values occur toward upper areas of the deposit. <br/>Major element concentrations of the common sulphide phases are fairly homogeneous, with pyrrhotite containing ~0.5 wt.% Ni, pentlandite averages 35.7 wt.% Ni and 1.1 wt.% Co. 'In situ' analysis of Os, Ir, Pt, Au and Ag using Laser Ablation-ICP-MS revealed concentrations in pyrrhotite from sub-ppb levels to 300 ppb Os, 62 ppb Ir, 235 ppb Pt, 726 ppb Au and 2624 ppb Ag. Values in pentlandite values range up to 642 ppb Os, 138 ppb Ir, 500 ppb Pt, 159 ppb Au and 21495 ppb Ag. Chalcopyrite has maximum abundances of 545 ppb Os, 69 ppb Ir, 14 ppb Au and 16593 ppb Ag. Platinum was detected in only one sample with a concentration of 53 ppb. The PGEs and Au occur as discrete, submicroscopic PGE-bearing inclusions within the sulphides. Any PGE held in solid solution have concentrations lower then the detection limits of the technique and contribute a minimal amount to the overall PGE concentrations of the deposit. PGE and Au distribution is very heterogeneous between neighbouring grains of the same phase ans also between location and mineralization style. Whole rock PGE analyses show a general increase in Pd, Pt and Au with increasing depth with a concurrent decrease in Ir, and Rh. PGE concentrations in the bulk ore at WD-16 are depleted relative to other contact-type North Range deposits. Trace eement concentrations of the whole rock and in situ analyses observed at WD-16 currently do not provide convincing evidence for appreciable sulphide fractionation.