San Xavier Extension Mine (Red Oxide group; Wakefield group), Pima Mining District, Sierrita Mountains, Pima County, Arizona, USAi

Regional Level Types
San Xavier Extension Mine (Red Oxide group; Wakefield group)	Mine
Pima Mining District	Mining District
Sierrita Mountains	Mountain Range
Pima County	County
Arizona	State
USA	Country

‡Ref.: Ransome, F.L. (1922) Ore deposits of the Sierrita Mountains, Pima County, Arizona, in Contributions to Economic Geology (Short Papers and Preliminary Reports), 1921 - Part I.--Metals and Nonmetals except Fuels: U.S. Geological Survey Bulletin 725J: 422.

Mayuga, M.N. (1942) The Geology and Ore Deposits of the Helmet Peak Area, Pima County, Arizona, PhD thesis, University of Arizona: 117.

Wilson, E.D., et al (1950), Arizona zinc and lead deposits, part I, Arizona Bureau of Mines Bull. 156: 47-48.

Burnham, C.W. (1959), Metallogenic provinces of the southwestern US and northern Mexico: New Mexico Bureau of Mines and Mineral Resources Bull. 65: 16, 30.

Keith, Stanton B. (1974), Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bull. 189, Index of Mining Properties in Pima County, Arizona: 137 (Table 4).

Niemuth, N.J. & K.A. Phillips (1992), Copper Oxide Resources, Arizona Department of Mines & Mineral Resources Open File Report. 92-10: 13 (Table 1).

USGS Twin Buttes Quadrangle topo map.

New Mexico Bureau of Mines and Mineral Resources Bull. 65: 16, 30.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10039579, MRDS ID #M050365; and, Dep. ID #10283700, MAS ID #0040190389.

A former small underground Zn-Pb-Ag-Cu-Au-Bi-Co-Mo-Cd-Mn-Ni mine located in the SW ¼ sec. 2 & the SE ¼ sec. 3, T.17S., R.12E., on the Red Oxide claim, west of the Twin Buttes road and NW of the San Xavier Mine (Twin Buttes 15 minute topo map), 5 miles NNW of Twin Buttes. Owned/operated at times or in part by the San Xavier Extension Copper Co.; and, the Chilson Mines Co.

It was developed originally by E.G. Bush. Prior to 1919 it yielded some 900 tons of ore that averaged about 4% Cu and 2 oz. Ag/T. During 1943-45 Chilson Mines Co. shipped a few thousand tons of ore containing Zn-Pb-Cu-Ag. Intermittent production occurred mainly in 1917-1918 and 1943-1945, of some 5,000 tons of ore averaging about 10% Zn, 2% Pb, 7 oz. Ag/T, 1% Cu and minor gold. Commodity sub-types are present as trace elements in sphalerite and chalcopyrite.

Mineralization is irregular, pyrometasomatic replacement ore deposits as shoots and lenses of partly oxidized zinc, lead and copper minerals along fractures and bedding in folded and faulted Paleozoic limestone. This type of ore probably represents an intermediate zone of mineralization between the Cu-garnet ores of the Mineral Hill area and the Pb-Zn-Ag ores of the San Xavier Mine.

Naco limestone overlaps Escabrosa with a fault contact that dips 25º southeastward. The Escabrosa limestone, particularly, has been metamorphosed to marble.

Many faults, largely of northeastward trend, were cut by the mine workings. A thrust-fault wedge of Escabrosa marble, bounded above, beneath, and on the north by impure Naco beds, was found to apex at the 100 level and thicken with depth southeastward. Mineralization occurred in the impure limestone on the northwest or lower contact of the marble wedge.

Workings include deep shaft operations, with a vertical shaft 500 feet deep (152.4 meters) with drifts extending northwestward on the 227 and 313 levels. The 227 level connects with the bottom of a shaft inclined 70º southeastward, 250 feet northwest of the vertical shaft. The ore zone was stoped mainly above the 227 level and to a limited extent above the 313 level. San Xavier is now part of the Mission Complex. See MRDS databaase record #O50387.

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Link to USGS MRDS:	10039579

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