Geological Framework of Alkalic Cu-Au Porphyry Deposits in central British Columbia, Canada
CIM Vancouver 2006
Adam B Bath, Paul Schiarizza,
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.
British Columbia, Porphyry, Mount Polley, Late Triassic, alkalic, Cu-Au