Longfellow Mine (Ofarizona Copper Co. group [in part]; Longfellow incline), Clifton, Greenlee County, Arizona, USAi

Regional Level Types
Longfellow Mine (Ofarizona Copper Co. group [in part]; Longfellow incline)	Mine
Clifton	- not defined -
Greenlee County	County
Arizona	State
USA	Country

A former surface and underground Cu-Au-Ag-clay mine located in the NE¼SE¼ & in the SE¼NE¼ sec. 16, and in the W½NW¼ sec. 15, T4S, R29E, in the Morenci open pit just N of Modoc Mountain. The upper workings of the Longfellow ore body extend over the East Yankee, Longfellow, and Longfellow Extension claims. Discovered by Robert Metcalf in 1872. Produced 1882-1932. Owned and operated by the Phelps Dodge Corp., Morenci Branch (as part of the Morenci Open Pit). Prior operators included the Longfellow Extension Copper Co.; the Arizona Copper Co. Ltd.; Leszynsky Brothers; and the Longfellow Mining Co.

Mineralization is an irregular ore body hosted in the Longfellow Limestone and Morenci Shale. The ore zone is 121.92 meters wide with a depth to bottom of 121.92 meters. Ore control was a funnel-shaped mass that occurs between two large porphyry dikes. Irregular and tabular deposits of very rich oxidized ores along the contact between limestone and porphyry. Associated rock units are the Coronado Quartzite and the Morenci Granite Porphyry. Ore concentration was secondary enrichment along sedimentary rock and porphyrycontacts, and between dikes. The porphyry dikes are somewhat mineralized but have no economic value. Mineralization was partially facilitated by the fault.

The principal stopes between the north and middle dikes displayed essentially cuprite with small amounts of manganese dioxide while stopes between the middle and south dikes showed copper carbonates with large amounts of black manganese. Pure kaolin occurs extensively in the mine. The Cu ore bodies narrow with depth.

Alteration is sericitized porphyry. The Morenci shale shows hardening and introduction of epidote. The limestone contains seams of magnetite intergrown with pyrite, chalcopyrite and prisms of pyroxene. Substantial surface oxidation to limonite and kaolin is present.

Local structures include a well-defined fault with strike of N65°W and upthrow on the south side of 80 to 100 feet. Three main porphyry dikes that trend ENE, widen considerably with depth (from 20 feet wide on surface to 90 feet wide at depth), and send out horizontal sheets in the lower part of the Longfellow Limestone. Ore bodies in the region tend to follow porphyry contacts.

Workings total 646.18 meters long and 137.16 meters deep. Developments included tunnels on 4 levels, stoping, open pit mining, one incline with a vertical run of about 80 feet.; The section of the Longfellow workings that lies on the East Yankee claim was developed by 4 levels from the East Yankee shaft (Detroit Copper Mining Co. of Arizona). A 1300 foot tunnel was driven from Chase Creek connects with a 600 foot blind shaft (winze).

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Link to USGS MRDS:	10048281

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References