Dome placers (Gila City placers; Gila City Mine), Dome Mining District (Gila City Mining District), Yuma County, Arizona, USAi

Regional Level Types
Dome placers (Gila City placers; Gila City Mine)	Group of Placers
Dome Mining District (Gila City Mining District)	Mining District
Yuma County	County
Arizona	State
USA	Country

A former surface placer gold mine/deposit area located in secs. 10 & 11, T8S, R21W, at the northern terminus of the Gila Mountains and the Gila River (1 to 2 miles long), and about 18 miles East of Yuma and 1½ miles W of Dome, on BLM-administered land. Started in 1858 after discovery by Colonel Jacob Sniveley.

Mineralization is in Quaternary outwashed materials and the pediment carved out in the underlying Tertiary (?) sediments forms their bedrock. Most of the gold was found at or near the bedrock in the gulches, but a considerable amount was recovered from the benches. Gravels more than 15 feet (5 meters) above bedrock have not been profitable. The gold probably originated from the various gold-bearing quartz veins in the northern end of the Gila Mountains. After each period of subsequent uplift, they suffered rapid erosion, and the weathered quartz veins of the decayedf rocks readly parted with their gold. The gold-bearing zone is 3,218 meters long, 804.6 meters wide and averages 4.57 meters thick.

Faulted against the schist of the main mountain mass is the series of probable Tertiary sedimentary rocks that constitute the bedrock of the bench and of the placer deposits. These beds consist of well-stratified, weakly consolidated locally mud-cracked clays, marls, arkoses, and sandstones. More or less faulting and tilting are evident throughout this formation. After tilting, these beds were beveled to a pediment.

Output is estimated variably as between $2,000,000 to $3,000,000 or about $500,000 (period values), depending on data source.

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Link to USGS MRDS:	10102461

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References