Geology of the Quest BC area: regional setting and - Geoscience BC PDF
Preview Geology of the Quest BC area: regional setting and - Geoscience BC
Exploration Undercover: Making Effective Use of Public Geoscience Data Geology of the Quest BC area: regional setting and ore deposit models Thomas Bissig, Mineral Deposit Research Unit, University of British Columbia Acknowledgements: Dianne Mitchinson, Santiago Vaca, Geoscience BC, and MDRU, Jim Logan, Paul Schiarrizza (BCGS). Porphyry deposits in BC and Yukon •Various types of porphyry mineralization •Alkalic and Calc-alkalic affiliations, but alkalic Cu-Au association most important •Highland Valley porphyry Cu deposit is the largest Open pit mine currently operating in N. America •2 Principal episodes: U. Triassic to Mid Jurassic and Late Cretaceous to Eocene Mod.from Sinclair, 2008 Upper Triassic-Upper Jurassic Porphyries •Most prolific metallogenetic epoch •Pre to syn accretion •Early Calc alkalic Cu-Mo (Au) porphyries •~206-203 Ma Alkalic Cu-Au porphyries •~ 200 Ma Calc alkalic Cu- Mo and Cu –Au porphyries •190-180 Ma Alkalic Cu-Au S porphyries Q •< 170 Calc alkalic Cu-Mo- Au porphyries (Island Cu) Mod after Nelson and Colpron, 2007 Cretaceous to Eocene porphyries All calc-alkaline, some Mo +/- W rich In British Columbia concentrated along the Skeena Arch = major crustal break Epithermal Au-Ag prospects present. Tectonic setting at time of porphyry emplacement Triassic Collapse of the back-arc Slide Mountains Ocean, and initial interaction of marine arc with continental margin Formation of calc-alkalic and alkalic PCD along length of arc at end of magmatic episode Graphics from Monger (2008); Nelson and Colpron (2007) Middle Jurassic 2nd stage of alkalic porphyry Final amalgamation Arc shifts to west Sinistral strike slip & opening of N. Atl. Graphics from Monger (2008); Nelson and Colpron (2007) Triassic Early Jurassic Formation of calc-alkalic and alkalic, Formation of alkalic PCD in localized silica undersaturated, PCD along area length of arc at end of magmatic episode Oceanic plateau? Graphics from Monger (2008); Nelson and Colpron (2007) Lorraine Quest compilation map Mt Milligan Alkalic Cu-Au porphyries Mt Polley, Milligan, Lorraine Calc Alkalic Mo and Cu-Mo Endako, Gibraltar Quest Endako Extensive cover! P. George Nechaco basin Gibraltar Mt Polley Geoscience BC Map 2009-4-1 Endako Nechako basin: host to Late Cretaceous to Eocene porphyries and epithermal deposits and prospects Capoose Classification according to Minfile Blackwater Epithermal Porphyry Mo-Cu Carbonate hosted Au-Ag Other probable epithermal Newton Map courtesy of E. Bordet, MDRU Igneous associations Porphyry Cu-Au-Mo deposit classification Silica- undersaturated 16 alkalic Silica-saturated ) % alkalic t w 12 ( Cu-Au O 2 K 8 Cu-Au(-Mo) Cu-Mo + Cu-Au O 4 2 Arizona calc- a SW Pacific High-K calc- N alkalic calc-alkalic alkalic 40 50 60 70 Magnetite- py-cpy vein, Copper Mtn. SiO (wt%) 2 Modified from Lang et al., 1995
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