Abstract

A copper sulfide-bearing feldspathic pyroxenite diatreme at the abandoned Guide copper mine, 5 km northwest of the main Palabora complex, Transvaal Province, Republic of South Africa, contains euhedral cumulate pyroxenes with primary fluid inclusions. These inclusions contain an aqueous silicate liquid which on cooling crystallized pyroxene and K-feldspar, leaving a residual potassium and sodium bicarbonate-chloride brine highly charged with copper and sulfur. Some of the inclusions on heating show evidence of developing two immiscible liquids, which quenching suggests could be carbonate and silicate liquids. A residual aqueous component was also present in these inclusions when they cooled. From these primary inclusions and secondary aqueous inclusions representing just the copper-rich brine, it is possible to reconstruct a detailed cooling history of the diatreme which demonstrates that the copper sulfides were deposited from a residual hydrothermal fluid.

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