Senator Morgan Mine group, Twin Buttes, Pima Mining District, Sierrita Mountains, Pima County, Arizona, USAi

Regional Level Types
Senator Morgan Mine group	Mine
Twin Buttes	- not defined -
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: 425-427.

Brown, R.L. (1926) Geology and ore deposits of the Twin Buttes district: Tucson, University of Arizona, M.S. thesis, 40 p.

Wilson, E.D. (1941), Tungsten Deposits of Arizona, Geological Series No. 14, Arizona Bureau of Mines Bull. 148: 37, 44-46.

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

Dale, V.B., et al (1960), Tungsten deposits of Cochise, Pima, and Santa Cruz Counties, Arizona, U.S. Bureau of Mines Report of Investigation 5650: 85-92.

Lemmon, D.M., and Tweto, O.L. (1962) Tungsten in the U.S., USGS map, MR-25.

Keith, Stanton B. (1974), Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bull. 189, Index of Mining Properties in Pima County, Arizona: 138 (Table 4).

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 334.

USGS Twin Buttes Quadrangle topo map.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10039591, MRDS ID #M050383; and, Dep. ID #10113317, MAS ID #0040190392.

A former small surface and underground Cu-Ag-Zn-Pb-W-Au-Mo mine located in the SW ¼ sec. 1 & the SE ¼ sec. 2, T.18S., R.12E., about 9 miles west of Sahuarita and 1½ miles SW of Twin Buttes. Discovered 1875 or 1876. Produced 1903-1918. Owned at times, or in part, by Mr. Baxter of Twin Buttes; operated by J.A. Poindexter; the Twin Buttes Mining & Smelting Co.; Taylor; and, the American Smelting and Refining Co. (ASARCO).

Mineralization is ore in short lenses as fine-grained, pyritic, chalcopyrite mineralization, with very little oxidation, in garnetized, pyrometasomatic zones, with spotty and local scheelite and powellite in quartz veins, localized by faulting, fracturing and favorable beds in Paleozoic limestone along a NW fault contact with Cretaceous sediments. Favo Rable Limestone beds. Closely associated Laramide granodiorite porphyry dike. Shearing parallel to, and in, veins. The ore body is 365.76 meters long, 3.05 meters wide, with a depth to bottom of 274.32 meters.

Copper mineralization occurs along the fracture zone and extends down to 900 feet, where minable grade ore runs out or granite is encountered. Tungsten ore occurs in WNW-striking quartz fissure veins that extend up to 50 feet long and 10 feet wide. These veins occur in Cretaceous (?) quartzite and shales for 600 feet.

Local structures include NW faulting with some NE faulting.

2 oz/t Ag reported. Ore contained 0.805% WO3. Processintg produced floatation concentrates assaying 62.08% WO3 with a recovery of 92.5%.

Local rocks are SW-ward dipping quartzite and shale, more or less epidotized, and in places, stained brown with iron oxide. Outcrops are a few tens of feet to more than 50 feet long and 1 to perhaps 9 feet wide.

Workings include several shafts with a mine depth of 900 feet (274.32 meters). Worked from the deep shaft in the 1890's to 1918 for copper with estimated and reported production of some 100,000 tons of 4% Cu, 9 oz. Ag/T and minor Zn and Au. Scheelite was mined from a 40-foot deep shaft, 175 feet SW of the Morgan shaft. About 120 tons of 1.25% WO3 ore were shipped in 1942-1943. Several trenches and prospect pits for turngsten. No work on W or Cu since 1943.

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Link to USGS MRDS:	10039591

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