Eureka District, Trigo Mts, La Paz Co., Arizona, USA

‡Ref.: Raymond, R.W. (1872) Statistics of mines and mining in the states and territories west of the Rocky Mountains [3rd report]: U.S. Treasury Department, 566 p.

Hamilton (1884).

Thompson, A.P. (1925), The Castle Dome lead district of Yuma County, Arizona Mining Journal: 9(4): 5-6, 48-49.

Wilson, E.D., Cunningham, J.B., and Butler, G.M. (1934), Arizona Lode Gold Mines and Gold Mining. Arizona Bureau of Mines Bull. 137: 40, 50-72.

Wilson, E.D., et al (1951), Arizona zinc and lead deposits, part II, Arizona Bureau of Mines Bull. 158: 89.

Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 39, 104.

Cooper, J.R. (1962) Bismuth in the United States, exclusive of Alaska and Hawaii: U.S. Geological Survey Mineral Investigations Resource Map MR-22, 19 p., 1 sheet, scale 1:3,168,000.

Parker, F.Z. (1966) The Geology and Mineral Deposits of the Silver District Trigo Mountains, Yuma County, Arizona. Masters Thesis, San Diego State College: 131-132.

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: 175 (Table 4).

A Pb-Zn-Ag-Au-Cu-Ba-F-Mo-V mining district located in T.3S., R.23W. in the southern Trigo Mountains, extending from the Colorado River Northward toward the Silver District. Organized in 1862.

Mineralization is varied: (1) Argentiferous lead, zinc, and minor copper and iron ores, deeply oxidized, in a gangue of quartz, calcite, limonite, barite and fluorite, in spotty, irregular, and lensing ore shoots along well-defined fissure veins and at fissure intersections, in Cretaceous-Tertiary volcanics intruded by Laramide granodiorite stocks; (2) Gold placer deposits in gravels and bars; (3) Copper-silver-gold mineralization in fault-fissure veins in schist; (4) Dumortierite with minor kyanite in erosional boulders; and, (5) Weak and spotty scheelite in a local fault fissure vein.

This region is made up of rugged, steep-sided, serrated ridges, alternating with canyons that are several hundred feet deep and drain southward or southwestward to the Colorado River. The prevailing rocks are well-laminated gray quartz-sericite schists of probable sedimentary origin. They generally strike Northward, dip at various angles, and display several systems of faults and fractures. A few aplitic dikes cut the schists.

The veins of this district occupy fault zones that strike about N,70ºE. and dip 45º or more NW. The veins range in width from less than one foot (0.3 meters) up to a general average of perhaps 3 feet (0.9 meters), and, in a few spots, swell to widths of twenty or more feet. Some of them are traceable for nearly a mile, but the oreshoots are rather pockety and tend to be localized in the vicinity of fissures that intersect the main faults at small angles. The vein filling consists predominately of manganiferous to ferruginous and white calcite, intermingled with masses of breccia and gouge.

Very cellular, crystalline, white quartz occurts in places. The oreshoots consist of limonite, hematite, cerussite and smithsonite, with scattered bunches and narrow veins of galena and ferruginous, black sphalerite. Locally, a few thin streaks of copper stain appear. The vein walls contain abundant, small, pyrite metacrysts and show pronounced sericitization together with less abundant silicification and chloritization. The mineralogy, texture and wall-rock alteration of these veins point to deposition in the epithermal zone.

Workings include numerous small mines worked sporadically from about 1865, but mostly from 1879 through the 1880's. Total estimated and recorded production of base and precious metals would be at least some 52,343 tons of ore containing about 1,460 tons of lead, 1.6 million oz. of silver, 940 oz. of gold, 15 tons of zinc and less than 1 ton of copper. The Colorado River placers produced about 1,160 oz. of gold and 100 oz. of silver. Possible minor tungsten production.

Mineral List

14 entries listed. 6 valid minerals.