By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Gila County, in mountainous east-central Arizona, ranks eighth among the gold-producing counties of the State with a total of about 240,500 ounces produced through 1959. Most of the gold has been a byproduct of copper ores mined from the Globe-Miami district; a lesser amount has come from copper ores of the Banner district. Placers have yielded an insignificant amount.
The Banner (Christmas) district lies in the extreme southern tip of Gila County at the southeast end of the Dripping Springs Mountains.
Many of the deposits have been known and worked intermittently since the 1870's, but little ore was shipped before 1900 (Ross, 1925, p. 29). The district is noted for its copper mines from which lead, silver, and gold were produced as byproducts. The Christmas mine, discovered in 1880 and operated intermittently through 1954, is the major mine in the district. Total gold production from 1905 through 1959 was about 26,000 ounces.
Small patches of Precambrian granite are exposed beneath a thick section of the Apache Group of late Precambrian age, Martin Limestone of Devonian age, and Tornado Limestone of Carboniferous age. The area of the Christmas mine is blanketed by sandstone, breccia, andesite, and basalt of Cretaceous age, which are overlain by patches of Tertiary bedded rocks consisting of tuff, conglomerate, basalt, and rhyolite. The Paleozoic and Cretaceous rocks throughout the district are cut by dikes and small masses of quartz-hornblende diorite and quartz-mica diorite of Cretaceous age. The rocks were slightly folded in post-Pennsylvanian time; more pronounced folding occurred in Late Cretaceous time. This was followed by faulting which continued through much of Tertiary time (Ross, 1925, p. 6-29).
The important deposits of the district are pyritic gold deposits in shear zones and contact metamorphic deposits such as those at the Christmas and Landon-Arizona mines. The pyritic gold deposits are principally in Cretaceous volcanic rocks, whereas the contact metamorphic deposits are mostly in Paleozoic carbonate rocks. Both types are near or adjacent to bodies of quartz-mica diorite. Pyrite and local chalcopyrite, magnetite, and specu-larite are the principal minerals of the pyritic deposits. The contact metamorphic deposits contain a variety of minerals, including magnetite, specu-larite, chalcopyrite, pyrite, sphalerite, galena, fluorite, chalcedony, and lime silicate minerals. In both types the richest ore has been in the oxidized parts (Ross, 1925, p. 32-39).
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