A new model for an old camp: the enigmatic Ag-Co-Ni-As-Bi mineralization of Cobalt, Ontario

Abstract

The recent emergence of Co as a critical metal used in a variety of high-technology industries has refocused exploration at Cobalt, Ontario. This district represents an unusual ore deposit-type termed the five-element (Ag-Ni-Co-As-Bi) assemblage and was important historically as Canada’s former premier Ag producer at over 460 Moz (1904-1989). This study applies a sophisticated analytical protocol consisting of whole rock analysis, petrography, and insitu mineral analyses (SEM-EDS, LA-ICP-MS) to a sample suite with spatial coverage across the district. These methods constrain geological controls on regional metal distribution, the sequence of alteration and mineralization, and the physiochemical evolution of the system. An updated genetic model for the mineralization involves the veins representing a district-scale homogeneous hydrothermal-metal melt system driven by contact metamorphism and partial melting of pre-existing sulfides in underlying Archean basement rocks. This model enhances understanding of deposit formation and offers refined geochemical vectors to aid ongoing exploration efforts.