Systematic and Integrative Ore Characterization of Massive Sulfide Deposits: An Example from Voisey's Bay Ni-Cu-Co Ovoid Orebody, Labrador, Canada

摘要

Systematic characterization of the mineralogy of massive sulfide ore deposits can provide valuable insights into ore genesis and metallurgical processing that would not be apparent otherwise. We describe a method wherein (1) normative mineral abundances are calculated from whole-rock chemical assays using an algorithm, (2) the results are cast in block models, (3) the results are then verified with automated image analysis of a subset of samples prepared as grain mounts by backscattered electron imaging and X-ray mapping on a scanning electron microscope, and (4) those verified results are integrated with textural data determined by optical microscopy. The technique is applied to the magmatic Ni-Cu-Co sulfides of the Ovoid orebody, based on geo-chemical assays of 3175 whole-rock samples. Three principal ore zones are defined in the Ovoid. Type I ore occurs in the center of the deposit; it is magnetite-rich and pyrrhotite-poor with intermediate contents of pentlandite and chalcopyrite. Type II ore surrounds Type I ore and is pentlandite-chalcopyrite-rich with intermediate contents of pyrrhotite and magnetite. Type III ore occurs at the base and along the outer periphery of the northern part of the orebody; it is pyrrhotite-rich and chal-copyrite-poor with an intermediate content of pentlandite, and a low-to-intermediate content of magnetite.