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Twelker, Evan, 2007

A breccia-centered ore and alteration model for the Copper Canyon alkalic Cu-Au porphyry deposit, British Columbia

Bibliographic Reference

Twelker, Evan, 2007, A breccia-centered ore and alteration model for the Copper Canyon alkalic Cu-Au porphyry deposit, British Columbia: University of Alaska Fairbanks, M.S. thesis, xii, 141 p., illust., maps.

Abstract

Similar to the nearby Galore Creek deposit, the Copper Canyon prospect of northwestern British Columbia is a porphyry-type copper-gold-silver occurrence associated with alkalic intrusive rocks of the Late Triassic-Early Jurassic Copper Mountain Suite. A reevaluation of the prospect geology shows that, of the previously recognized orthoclase and/or pseudoleucite porphyry syenite intrusions, mineralization is spatially and temporally associated with a single intrusive phase (unit i5) and biotite-garnet stockworks. Further, a newly defined unit of pre-mineralization magmatic-hydrothermal intrusive breccia occupies the core of the prospect and is a favorable host for much of the prospect mineralization. Prospect alteration can be divided into two distinct styles. Calc-potassic alteration consists of K-feldspar, Mg and Fe3+-rich (An20) biotite, andradite-rich garnet, hematite, magnetite, chalcopyrite, pyrite, and sphalerite (Zn94-99, Feo 5-2<5-2, Cdo 4-1)S and is associated with copper-gold-silver mineralization. Ankerite-sericite-pyrite (± fluorite, albite, anhydrite, pyrite, and trace covellite and bornite) alteration adjoins this core, hosting gold mineralization and insignificant copper. Sulfide-electrum and biotite geothermometry suggest fluid temperatures decreasing from the core (≤550°C) to distal gold mineralization (≤361°C). Distal gold mineralization is most likely the result of higher than typical sulfur activity and bisulfide transport of gold.

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