Humboldt Mine (Humboldt tunnel; Liverpool tunnel; Arizona Copper Co. group [in part]), Morenci, Greenlee County, Arizona, USAi

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

A former surface and underground Cu-Zn mine located on the Joy claim, in the E½SW¼W½SE¼ sec. 16, T4S, R29E, at the SE foot of Copper Mountain, under the present town of Morenci, on private property. The shaft is located in the W½SE¼ sec. 16. Situated in the center of town. Discovered by Miles Joy (?) in 1892. Produced 1892-1932. Owned and operated by the Phelps Dodge Corp., Morenci Branch. Past operators included the Arizona Copper Co. Ltd.

Mineralization is a disseminated ore body hosted in the Modoc Limestone, Morenci Shale, and Longfellow Limestone. The ore zone is 609.6 meters long, 182.85 meters wide, with a depth to top of 60.96 meters and a thickness of 304.8 meters, striking N25E and dipping 70SE. Associated rock units are the Morenci Granite Porphyry and the Coronado Quartzite. Ore control was a NE-trending fissure vein containing several seams of massive chalcocite, adjoined by decomposed porphyry with disseminated grains and small seams of chalcocite and pyrite. Ore concentration was mineralization along fissure veins; porosity and looseness of grains in porphyry allowed ore solutions to permeate host rock to great depths. Alteration was surface oxidation of chalcocite zone with chalcocite replacing pyrite.

Decomposed porphyry surrounding the veins consists primarily of sericite, quartz, pyrite and chalcocite. The ore body is almost exclusively confined to porphyry. Veins entering sedimentary masses become narrow and poor. Regional faulting occurred after vein emplacement. The Humboldt ore body is one of 4 principal lodes at Morenci (the others are the Wellington, Ryerson, and the West Yankie). Rich chalcocite ore is replaced at depth by a strong vein of massive low-grade pyrite and chalcopyrite with well-defined walls of greatly altered porphyry and varying width. The Humboldt vein extends from NE to SW through Copper Mountain and is 1 to 4 feet wide. The Humboldt Mine is situated on the Humboldt and Wellington lodes.

Area structures include NE-trending fissure veins containing rich chalcocite ore. Between the Humboldt vein and another fissure vein 200 feet distant, lies the great mass of concentrating ore. Extensive seam impregnations of the country rock are rarely confined by distinct walls. Veins cut across both porphyry and metamorphic limestone. The vein footwall is generally a well-defined plane and follows porphyry dikes in some places.

Tectonic component is the complex Copper Mountain fault system with substantial vertical displacement. Fault blocks generally downthrown to the NE The Copper Mountain fault cuts across the Humboldt Mine to the SW.

Workings are 3218.6 meters long and 121.92 meters deep. The Humboldt shaft is located on the Joy claim adjacent to the Humboldt property on the S and is 400 feet deep. Developments included several crosscuts, several stopes with lengths of 500 feet and widths of 40 feet or less. The Humboldt tunnel is 1650 feet long. The Liverpool tunnel starts from the NW side of Copper Mountain.

Production data included in the Longfellow Metcalf Mine. Longfellow Metcalf also includes the other Arizona Copper Co. mines of Detroit, Longfellow, Metcalf, Coronado, Yavapai, Mammoth, and Joy mines.

Other Databases

Link to USGS MRDS:	10088900

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References