Geochemistry of gold from Ontario gold deposits

Abstract

Gold is one of the most crucial metals in human history, and still, few investigations have directly studied gold composition to understand gold systems. Ontario (Canada) provides a natural example of gold systems because of the abundance and distribution of world class gold deposits. The present study constrains the geochemical signature of free gold using SEM-EDS, EPMA and LA-ICP-MS to characterize 242 samples from 71 gold deposits and occurrences. Generally, Ag, Cu, and Hg occur over 100 ppm, with Sb, Pd, Cd, and Bi typically as trace elements between 0.001 and 100 ppm. The geochemical signature of gold varies at the craton scale but is consistent at the camp scale. These spatially distinct trace element signatures are independent of local host rock and deposit types, which have implications regarding the controls on ore-forming mechanisms and reflect district-scale variations in the primary and secondary composition of gold. This elemental signature has important practical applications for industry; for example, in using elemental vectors that reflect local gold composition and/or in metallurgical processing.