Tank Mountains District, Tank Mts, Yuma Co., Arizona, USA

A Au-Mn-Fe-Cu mining area located in T2-4S, R13-16W, in the Tank Mountains, NW of the Palomas Mountains.

Mineralization is varied: (1) Scattered, short, lenticular, and narrow, gold-bearing quartz, carbonate, iron oxide and minor, partly oxidized, copper and iron sulfide veins in fissure zones in Mesozoic granitic intrusive and metamorphic schist, with dioritic to rhyolitic dikes. Wall rocks are sericitized, silicified, and carbonatized. Gold concentrated by weathering in near-surface iron oxides and quartz; (2): Separate and discontinuous, lenticular pods of pyrolusite, psilomelane, and manganiferous calcite in fissure zones in Tertiary andesitic flows, tuffs, and breccia; (3) Small gold placers in various washes resulting from the rosion of the gold-bearing quartz-carbonate-iron oxide veins, notably in the northwestern area near the engesser prospect and in the southeastern area.

Workings include mostly shallow pit, shaft and open cut operations. The gold-quartz veins and gold placers were discovered by prospectors in the late 1800's and were worked sporadically since then. The total production from these veins would some 50 tons of ore containing about 50 oz. of gold with 10 oz. of silver recovered by panning and amalgamation. Possibly as much as 200 oz. of gold were recovered by dry placer operations. Manganese production was about 50 long tons of ore at 25-30% Mn.

References:
Burchard, H.C. (1883-85) Arizona, in Report of the director of the Mint upon the statistics of the production of the precious metals in the United States [annual volumes for the years 1882-1884]: Washington, D.C., U.S. Government Printing Office.

Wilson, E.D. (1933) Geology and Mineral Deposits of Southern Yuma County, Arizona. Arizona Bureau of Mines Bulletin 134: 123-127.

Wilson, E.D., Cunningham, J.B., and Butler, G.M. (1934), Arizona Lode Gold Mines and Gold Mining (revised 1967), Arizona Bureau of Mines Bull. 137: 147-148.

Wilson, E.D. (1961) Gold Placers and Placering in Arizona. Arizona Bureau of Mines Bull. 168 (revised 1978): 24-25.

Farnham, L.L. & L.A. Stewart (1958), Manganese deposits of western Arizona, US Bureau of Mines Information Circular 7843: 85-86.

Johnson, M.G. (1972), Placer gold deposits of Arizona, USGS Bull. 1355: 71-73.

Keith, Stanton B. (1978) State of Arizona Bureau of Geology and Mineral Technology, Geological Survey Branch Bull. 192, Index of Mining Properties in Yuma County, Arizona: 179 (Table 4).

Arizona Bureau of Mines file data.