Nickel tenor variations between Archaean komatiite-associated nickel sulphide deposits, Kambalda ore field, Western Australia: the metamorphic modification model revisited

Geochemical data for 870 ore samples of 14 nickel sulphide (NiS) deposits from throughout the major Archaean Kambalda ore field, Western Australia, reveal highly heterogeneous Ni tenor (wt% Ni in 100 wt% sulphide) variation that is difficult to explain solely by magmatic processes. The Ni tenor values for the deposits range from 6.2 wt% Ni (Helmut deposit) to 19.7 wt% Ni (Carnilya Hill deposit), close to the range for within single deposits (9.7–19.3 wt% Ni). Contents of Ni and platinum-group elements (PGE) broadly increase with decreasing Fe and with increasing abundance of metamorphic pyrite + magnetite ± silicates. In turn, the abundance of the metamorphic phases appears to be complexly related to structural setting, metamorphic grade, alteration type, and proximity to felsic intrusion. Chondrite-normalised multi-element plots of deposit compositions reveal relative depletions in Au, As, Bi, and Te.