Abstract
The Quesnel River gold deposit (1.2 million tonnes grading 5.22 g/t Au in three separate zones) occurs within Takla Group volcanic rocks of Upper Triassic age proximal to an alkalic stock. The deposit occurs in amphibole-augite phyric, fragmental, basaltic rocks. Alteration has produced an assemblage of epidote-chloritetremolite-calcite-quartz with lesser pyrite, chalcopyrite, pyrrhotite, sphalerite, marcasite, galena, arsenopyrite and gold.
The West Zone comprises a tabular, conformable sulfide body underlain by bedded, variably altered fragmental basaltic rocks and overlain by siltstone and argillite. In the Main Zone, highest gold grades occur adjacent to a sharp discordant alteration front with barren, strongly carbonatized, pyritic basaltic lapilli-tuff. It is overlain by siltstone and argillite and bounded to the east and a depth by a west dipping reverse fault. To the west the auriferous, propylitically altered, rocks grade laterally into lower grade and barren basaltic rocks.
Oxygen(δ18O = + 9 to + 15) and carbon (δ13O= -14 to −7) isotopic signatures of calcite from carbonate-altered and propylitically altered rocks are similar. However, sulfur isotopic values for pyrite are different, with gold-associated pyrite (δ34S = −7 to −3) distinct from pyrite in carbonate altered rocks with (δ34S = + 8 to + 13).
The carbonization occurred before complete induration of the basaltic fragmental rocks, whereas propylitization and gold plus sulfide precipitation is clearly epigenetic.
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Melling, D.R., Watkinson, D.H., Fox, P.E. et al. Carbonatization and propylitic alteration of fragmental basaltic rocks, Quesnel River gold deposit, Central British Columbia. Mineral. Deposita 25 (Suppl 1), S115–S124 (1990). https://doi.org/10.1007/BF00205258
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DOI: https://doi.org/10.1007/BF00205258