The Red Chris Porphyry Copper-Gold Deposit, Northern British Columbia, Canada: Igneous Phases, Alteration, and Controls of Mineralization

摘要

Red Chris is a Late Triassic porphyry Cu-Au-(Mo) deposit in the Stikinia island-arc terrane in northern B.C. Late Triassic sedimentary and volcanic rocks of the Stuhini Group host a series of Late Triassic to Early Jurassic (204-198 Ma) diorite to quartz monzonite stocks and dikes. The Red Chris deposit is hosted in the 204 Ma Red stock, the largest (6.5 x 1.5 km) and most altered intrusion in the area. Volcanic rocks approximately time equivalent with the stock are exposed 2 km to the southwest and west. Postmineral Early and Middle Jurassic sedimentary rocks unconformably overlie the Stuhini Group and Red stock to the south and southeast. The composite Red stock consists of multiple phases of crowded porphyries (30-65% plagioclase + hornblende +/- biotite phenociysts) including abundant premineral "P1" leucodiorite; multiple subphases of synmineral "P2" quartz monzonite porphyries; and volumetrically minor late mineral monzonite ("P3") and monzodiorite ("P4") porphyries. The stock evolved from subalkaline to silica-saturated alkalic composition, with the mineral-related P2 porphyries being high K calc-alkalic and high Sr/Y. Common septa of Stuhini biotitic hornfels are entrapped within the stock. Minor postmineral, weakly altered mafic dikes cut the stock.