Adsorbed Gold in Clay Minerals from Hardrock Gold, Geraldton, Ontario

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Greenstone Gold Mines is a 50/50 partnership between Centerra Gold and Premier Gold Mines for the development of, amongst others, the Hardrock gold property. Preliminary research by Dr. Nadeau and student on the Archean Hardrock gold deposit suggests that gold was partly remobilized from its primary location through weathering during the 2.7 billion years that followed its emplacement. Analysis of a limited set of samples suggests that besides that which is associated with sulfides, a significant amount of gold is hosted in a low-temperature phase containing loosely bonded volatiles, titanium, cadmium and heavy rare earth elements. The total amount of gold and other economic metals in these rocks must thus be partly related to their concentration in that low-temperature phase and the extent of the weathering. The auriferous low-temperature phase was degassed at a temperature lower than 105°C and thus probably is a clay mineral. The scientific objectives are to precisely identify these clay minerals using x-ray diffraction spectrometry (XRD) and to identify and quantify the metals adsorbed at their surface using x-ray photoelectron spectrometry (XPS) and laser ablation ICP-MS (LA-ICP-MS). Although XRD and XPS/LA-ICP-MS have been used before to identify clay minerals and the metals adsorbed on their surfaces, the concept of weathered Archean gold deposits and the combination of these techniques in the context of Archean gold metallogenesis would represent a world premiere. Given the current interest of mining companies for large-tonnage/low-tenor, open pitable deposits, the combination of this discovery with such methods will certainly have impactful results on exploration and mining activities. Ultimately, these results should help Canadian exploration and mining companies refine their resource estimates, metallurgical flow sheets and exploitation procedures, which in turn will enhance their economic activity and the Canadian economy.