Abstract

The Copper Cities copper deposit in the Globe-Miami district, Arizona, is now in process of development. It is of the "porphyry" type and occurs in a body of quartz monzonite that has been intruded by smaller masses of granite porphyry. The hypogene sulfides are pyrite, chalcopyrite, and a very little molybdenite. Pyritic mineralization extends over a large area of which only a small portion contains an appreciable amount of chalcopyrite. The outcrop of the copper-bearing rock, roughly 1,800 feet square, is bounded on the west, north, and east sides by fault zones. The south boundary is gradational. The pyrite to chalcopyrite ratio of the protore increases rapidly with depth, whereas the copper content decreases but slightly. The ore body is a shallow chalcocite zone formed by supergene enrichment. Bodies of granite porphyry within the copper-bearing area were not as strongly mineralized by hypogene solutions as the quartz monzonite, and in them the chalcocite zone is thin, undoubtedly because the granite porphyry is less pervious to ground water than the quartz monzonite.

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