Abstract

Pyrometasomatic sphalerite-chalcopyrite deposits at Johnson Camp are pipes as much as 2,000 feet long, formed along bedding-plane channelways of mineralizing solutions rather than at the intersections of cross-cutting channels with favorable beds. Nearly all of the sphalerite contains numerous microscopic blebs of chalcopyrite. The principal control for variations in the abundance and size of these blebs is stratigraphic, and an attempt to use bleb patterns as a guide to new ore failed because of this stratigraphic control. Blebs are not present in ore that contains bornite. The blebs originated by exsolution as the ore deposits cooled, but before the mineralizing solutions stopped circulating.

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