Longfellow Mine (Ofarizona Copper Co. group [in part]; Longfellow incline), Clifton, Copper Mountain District (Clifton-Morenci District), Shannon Mts, Greenlee Co., Arizona, USA
|Latitude & Longitude (WGS84):||33° 5' 3'' North , 109° 21' 29'' West|
|Latitude & Longitude (decimal):||33.08417,-109.35806|
|Other regions containing this locality:||Sonoran Desert, North America|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
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).
12 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Serpukhovian - Early Cambrian|
323.2 - 541 Ma
|Mississippian, Devonian, and Cambrian sedimentary rocks|
Age: Paleozoic (323.2 - 541 Ma)
Description: Brown to dark gray sandstone grades upward into green and gray shale, overlain by light to medium gray or tan limestone and dolostone. This unit includes the Tapeats Sandstone, Bright Angel Shale, Muav Limestone, Temple Butte Formation and Redwall Limestone in northern Arizona, and the Bolsa Quartzite, Abrigo Formation, Martin Formation, and Escabrosa Limestone in southern Arizona. These rocks record intermittent sea-level rise and inundation in early Paleozoic time. (330-540 Ma)
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.