Nelson Roman, PhD
N. Román1, D. Gregory1, R. Chapman2, J. Mortensen3, J. Thompson4, P. Tallman5
1Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
2Ores and Mineralization Group, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
3Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
4U.S. Geological Survey, Geology Geophysics and Geochemistry Science Center, Denver, Colorado, United States
5Klondike Gold Corp., Vancouver, British Columbia, Canada
Linking placer Au alloy (native gold, electrum) to specific vein Au occurrences is a fundamental exploration tool in Au districts. In the Klondike Au district, Yukon, this approach has been successfully implemented from a compositional and mineralogical viewpoint by previous studies, based on electron probe microanalyses (EPMA) of large sample populations combined with detailed petrographic mineral inclusion examination. However, this approach is limited due to the relatively high detection limits of EPMA which restricts the identification and quantification of additional trace elements, and by the scarcity of mineral inclusions in Au alloy grains. With the goal of enhancing the certainty of placer-vein relationships in the Klondike, here we report preliminary vein and placer Au alloy LA-ICP-MS trace element composition from the Klondike, focusing on the Lone Star area.
The most detected elements in Au alloy were Ag, Hg, Cu and Sb. Lead, Pd, Pt and Bi were detected in more than 40% of the analyzed spots. Vein Au alloy composition variation trends were observed. Mercury concentrations in vein Au systematically decrease from Lone Star to the southwest Au occurrences (Nugget-Buckland, Dysle-Gay Gulch and Violet), whereas Cu concentrations show the opposite trend. Gold alloy element ratios (Hg/Cu and Ag/Cu) discrimination diagrams highlight the relationship between placer and vein Au in the district.
Future work will use Au alloy Pb isotope data to reinforce the geochemical placer-vein Au link. The results of this study are expected to have direct application for exploration in the Klondike and elsewhere.