Geological Framework of Alkalic Cu-Au Porphyry Deposits in central British Columbia, Canada

CIM Vancouver 2006
Adam B Bath, Paul Schiarizza,
Abstract British Columbia is well endowed with porphyry deposits, including Late Triassic Cu-Au porphyries associated with alkaline intrusions at Galore Creek, Mount Polley and Afton-Ajax. These and co-spatial calcalkaline Cu-Mo +/-Au porphyry deposits formed in island-arc settings, represented by Quesnel and Stikine terranes, on the fringes of ancestral North America, in Late Triassic – Early Jurassic.
The Quesnel terrane is an isotopic and geochemically primitive magmatic arc complex that formed above an east-dipping subduction zone (Cache Creek terrane). Arc magmatism and associated porphyry mineralization migrated eastward with time beginning in the west, ca. 212 Ma with development of calcalkaline Cu-Mo +/-Au deposits at Highland Valley and Gibraltar. East of Gibraltar, Na-and K-rich, submarine to subaerial lava flows, cogenetic alkaline intrusions and 204 Ma, Cu-Au mineralization occupy the central axis of the arc. They conformably overlie or intrude Middle to Upper Triassic, sediments and subordinate back-arc lavas of N- and E-MORB affinities. Uplift and erosion of the fore-arc produced sub-Jurassic unconformities as magmatism-shifted east and culminated with intrusion of calcalkaline plutons at 195 Ma and deposition of distal volcaniclastic and younger sedimentary rocks across the terrane.
Keywords: British Columbia, Porphyry, Mount Polley, Late Triassic, alkalic, Cu-Au
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