Mansfield claim (Expectation group), Copper Mountain District (Clifton-Morenci District), Shannon Mts, Greenlee Co., Arizona, USA
A former underground Cu-Au-Ag mine located in the NW¼SE¼ sec. 35, T3S, R29E, 0.5 mile NNW of the summit of Copper King Mountain, on the ridge descending into Placer Gulch, 2.5 miles ENE of Metcalf, on private land. The Mandfield claim was unpatented. Discovered in 1875. Owned by the Phelps Dodge Corp., Morenci Branch (1922). Other owners included the Clifton Consolidated Copper Mines Co.; the New England and Clifton Copper Mines Co. (1903-1912); and the Detroit Copper Mines Co. of Arizona (1912-1921).
Mineralization is a vein deposit associated with Morenci Granite Porphyry and Precambrian granite-granodiorite complex. The ore zone is 1.83 meters wide, strikes NE and dips vertically. The orebodies are pockets. Ore control was along a NE-trending dike. The main orebody lies at a cross fracture to the dike. Surface oxidation exists to unknown depths. The porphyry is greatly bleached by seritization and extensively cemneted by quartz veinlets.
Area structures include NE-trending, narrow porphyry dikes in coarse reddish quartzitic granite. Veins consist of many very sharply defined fissure planes striking NNE. The granite country rock is fragmented by small dike(s) of basalt or andesite. A volcanic dike fractures the porphyry dike about 15 feet (5 meters) below the surface.
Local tectonic features include the Copper King massif and block faulting NW of the massif with a downthrow of about 1000 feet.
Workings total 91.44 meters in length and 45.72 meters in depth. Developments included small surface workings and one tunnel 300 feet long.
ReferencesLindgren W. (1905) USGS Professional Paper 43: 262-263.
Stevens, P. (1911) The Copper Handbook: Vol. 10: 1284-1285, New England and Clifton Copper Co.
Weed, W.H. (1914) The Copper Handbook: Vol. 11: 648, New England and Clifton Copper Co.
Bennett (1975) Geology and Origin of the Breccias in the Morenci-Metcalf District, Greenlee County, Arizona, MS thesis, University of Arizona, 153 pp.
MRDS database Dep. ID #10026952, MRDS ID #M001271.
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4 entries listed. 3 valid minerals.
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Locality Updated: Wheal Mithian, Mithian, St Agnes, St Agnes District, Cornwall, England, UKFrom Peter Haas, 31st Aug 2014 00:06:07