Detroit Mine (Arizona Copper Co. group [in part]), Morenci, Greenlee County, Arizona, USAi

Regional Level Types
Detroit Mine (Arizona Copper Co. group [in part])	Mine
Morenci	Town
Greenlee County	County
Arizona	State
USA	Country

A former surface and underground Cu-Ag-Zn-Mn mine located in the S½SE¼ sec. 16 and in the N½NE¼ sec. 21, T4S, R29E, to the E of the Manganese Blue Mine and to the S of the Copper Mountain Mine, under the present town of Morenci, on private land. Discovered 1884. Produced 1884-1932. Formerly owned by the Arizona Copper Co., Ltd. Owned and operated by the Phelps Dodge Corp., Morenci Branch.

Mineralization is a tabular ore body hosted in the Modoc Limestone and Morenci Shale. The ore zone is 121.92 meters long, with a depth to top of 22.86 meters and depth to bottom of 121.92 meters, at 12.19 meters thick, striking NW and dipping 10SW. Ore chiefly contains malachite and azurite; chalcocite and cuprite are rare. An associated rock unit is the Morenci Granite Porphyry. Ore control was several ore-bearing horizons contained in limestone and separated by barren material. The main ore body contained between two large porphyry dikes (Joy and Hummingbird dikes) that both dip 60° to 70° NW, and lies immediately under heavy garnet rock and is about 25 feet thick. A lower ore body of 5 foot thickness is separated from the main ore body by a barren lime-shale sequence.

Ore concentration was mineralization along bedding planes; supergene enrichment facilitated by the Copper Mountain Fault. Alteration involves the upper beds of the Modoc Limestone altered to garnet rock. The ore is entirely oxidized.

Area structures are the Copper Mountain Fault, which dislocates both dikes. The east side of the fault shows SE horizontal throw of 5o to 70 feet. The mine is located just S of the main porphyry contact at Morenci. Garnet in the exposed Modoc Limestone Formation forms a caprock of 75 to 100 feet thickness. Porphyry dikes generally do not contain ore but are occasionally cut by vertical seams of pyrite.

Workings are 121.92 meters deep. Developments included the 224 foot deep Detroit shaft with 4 levels; connections to the Joy shaft. Several adits connected by a maze of irregular stopes and workings; 400 foot deep South shaft near the Copper Mountain Fault.

Production data included in the Longfellow-Metcalf Mine. Longfellow Metcalf also includes the Mammoth, Yavapai, Longfellow, Metcalf, Coronado, Joy, and Humboldt Mines of the Arizona Copper Co. Ltd. Ore reported to be nearly exhausted in 1905. Total production estimated at 150,000 tons. The Detroit and Longfellow Mines were the largest producers for the Arizona Copper Co. Ltd. The Detroit Mine should not be confused with the Detroit Copper Co. mines at Morenci.

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Link to USGS MRDS:	10048296

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References