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A gold-specularite deposit, Unuk River, B.C.

University of British Columbia

On the Gracey group of claims, Unuk River, B.C., are mesothermal-type quartz veins; (1) with speoularite-gold mineralization, (2) with galena-pyrite-gold mineralization, and (3) with chalcopyrite-pyrite mineralization containing no precious metals. The veins outcrop in a band of Late Palaeozoic(?) andesite tuff, siltstone, argillite, and limestone bordered on the northeast and southwest by Triassic(?) diorite gneiss sills. The main body of Coast Range intrusives outcrops five miles southwest of the property, but several stocks are exposed about five miles east of the property. The regional-type metamorphism, and most of the folding and faulting of the bedded rocks on the property have been caused by orogeny associated with the Coast Range intrusives; but some recrystallization of andesite-tuff can be attributed to thermal metamorphism produoed by the adjacent diorite-gneiss sills. The vein-forming fluids are probably derived from Coast Range intrusive rather than the local sills. In the quartz-galena-pyrite veins anhedral gold fragments are associated with three soft minerals, possibly tellurides, which form inclusions in the galena. In the quartz-specularite-gold veins the gold has been deposited in disruptions between specularite 'cleavage' plates. Both classes of veins contain minor amounts of gold in or near fractures in the quartz. No veins contain both abundant specularite and abundant sulfides. The specularite probably has been deposited earlier than the sulfides but in the same period of mineralization. Specularite does not necessarily indicate hypothermal deposition, but it is usually one of the first minerals deposited from hydrothermal solutions. It is formed only under oxidizing conditions, and if exposed to later sulfide-bearing, and thus reducing, solutions, it tends to be reduced to magnetite or an iron-bearing sulfide.

Text

2012-03-28

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http://hdl.handle.net/2429/41850

Geological Sciences

University of British Columbia

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