Arizona Gold Production Summary |
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In Arizona 42 districts in 10 counties produced in excess of 10,000 ounces of gold (fig. 7) ; many additional districts are credited with smaller amounts. According to Wilson, Cunningham, and Butler (1934, p. 13), nearly 80 percent of the State's lode gold production and much of the placer gold has come from deposits that occur in a northeast-trending belt called the mountain region by Ransome (1903, p. 15-16), which is about 65 miles wide and borders the southwest margin of the Colorado Plateau. Within this belt the deformed Precambrian rocks have been tilted, intensely faulted, and intruded by masses of igneous rocks. In the desert region, southwest of the mountain region, the deposits are widely scattered.
The gold deposits of Arizona are of several types. In the San Francisco and Kofa districts gold deposits occur in epithermal quartz-calcite veins of Tertiary age. The Weaver, Vulture, Harquahala, Gila City, Wallapai, and Dos Cabezas districts are representatives of mesothermal vein systems of Mesozoic or Tertiary age with sulfide-quartz veins rich in silver and gold. In the porphyry copper deposits—in the districts of Ajo, Bisbee, Clifton-Morenci, Globe-Miami, Ray, San Manuel, and Superior—the ore bodies are of late Mesozoic or Tertiary age and are in intrusive bodies of quartz monzonite and the adjacent country rocks. The porphyry copper deposit at Jerome is of Precambrian age. Replacement deposits, rich in gold, silver, and base metals, occur near granitic intrusives in the Tombstone, Big Bug, Turquoise, Banner, and Agua Fria districts.
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