Geochemistry and Geochronology of Scheelites as constraints on the formation of gold ore deposits at Timmins West mine, Ontario

点击翻译按钮获取中文摘要

New gold ore deposits are increasingly hard to find for mining companies such as Lake Shore GoldCorporation (a wholly owned subsidiary of Tahoe Canada / Tahoe Resources Inc.) in Timmins, Ontario. Keyparameters in gold exploration are to understand their relationship to geological processes and obtain preciseknowledge of the deposits' ages. Gold deposits are challenging to age date because they may be formed laterthan the host intrusions and the origin of the auriferous fluids can be associated with the intrusion itself,metamorphism or from deeper parts of the crust or mantle. Moreover, elements used for long-lived radioactivedecay systems do not partition well into gold. Neighbouring minerals are not always reliable either as they mayhave crystallized in the presence of different fluids or are minerals pre-dating the mineralization itself. As aconsequence, at the West Timmins mine (TWM), there is currently no chronology established for goldmineralization. Only the age of the host rocks of the veins are available (Barrie, 1990) and may pre-datemineralization by tens of million years. Gold is found in veins next to minerals such as scheelite (CaWO4) andtitanite (CaTiSiO5) at TWM. Following a successful visit of Lake Shore in 2016 using a NSERC Connectgrant, when we discussed with the company what geochemical and geochronological tools we can use foranalyzing scheelite, we propose here to constrain the source of metals, geological processes associated with theformation of gold veins, and determine their radiometric ages. Knowing when and how many events wereresponsible for gold mineralization is critical to build a "footprint" of the geological processes responsible forgold deposition in Timmins. Our results will provide constraints on potentially areas of future exploration forLake Shore Gold Corporation.