Research about Mora County, New Mexico

USGS1954

Copper and uranium mineralization in the Coyote mining district, Mora County, New Mexico

Sedimentary copper-uranium deposits lie along the eastern flank of the Sangre de Cristo Range in the Coyote mining district, Mora County, New ilexico. The oldest rocks in the district are pre-Cambrian granites, pegmatites and metasediments. These are unconformably overlain by marine limestones and shales of Pennsylvanian age and fluviatile sediments of Pennsylvanian-Permian age. Tertiary basalt flows are extensive to the east and cover Pennsylvanian and Permian rocks locally. The copper-uranium mineralization occurred in a belt of thrusting and transverse faulting associated with the uplift of the Ancestral Rockies, but there is no visible evidence to relate the ore deposits to faults. The uranium deposition seems to have been controlled by channels containing carbonized plant remains in the coarser sandstone lenses of the Sangre de Cristo formation. There are two major types of ore deposits in the Coyote district. One consists of copper-replaced pyrite nodules and plant remains in black carbonaceous shales, the other consists of uranium in cross bedded sandstones. Copper is most abundant in the lower 1500 feet of the Sangre de Cristo formation. The most important copper mineral is chalcocite with minor amounts of chalcopyrite, bornite, covellite, pyrite, malachite, and azurite. The uranium minerals are metatyuyamunite and an undetermined black radioactive mineral associated with chalcopyrite. The uranium occurs in stream channels approximately 2000 feet stratigraphically above the top of the Aagdalena group (as mapped). The copper-uranium was probably derived from nearby pre-Cambrian highlands which contain abundant copper mines, granitic intrusions, and uranium bearing pegmatites. Heteoric waters containing copper sulfate and a soluble uranium compound transported the minerals to their present site and upon encountering carbonaceous material were precipitated out.

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USGS1954

The copper and uranium deposits of the Coyote district, Mora County, New Mexico

The copper and uranium-vanadium deposits of the Coyote district, Mora County, N. Mec, are confined to the lower 2,000 feet of the Sangre de Gristo formation of Pennsylvanian and Permian age. A narrow belt of deposits in steeply dipping or overturned rocks extends for 7 miles along Coyote Creek south of Guadalupita. Earlier studies showed that the copper deposits contained uranium, but both the reserves and the uranium content of the copper-bearing shale are too low to permit the recovery of uranium. However, small, commercial grade uranium deposits have been discovered in sandstone. Small lenses of copper-bearing carbonaceous shale, siltstone, limestone or sandstone, interbedded with predominantly red rocks, are present at intervals at 12 or more stratigraphic levels. The better deposits, in carbonaceous shale, average about 2 percent copper. The copper content of the other rocks is usually lower, but small concentrations may contain 6 percent copper. The principal copper minerals are chalcocite and malachite. Chalcocite replaces wood and forms nodules that contain small, variable amounts of pyrite, bornite, covellite, and rarely, uraninite. The uranium deposits occur as small closely spaced pockets that are commonly localized by sedimentary structures within one or more fluviatile arkosic sandstone beds near the middle of the formation, particularly" where carbonized wood, clay galls, and rock fragments are abundant. The uraniferous sandstone is commonly stained pink by hematite that probably was introduced with the uranium. The color increases in intensity with the radioactivity. The outcrops of the uranium deposits are typically inconspicuous, but close inspection shows they contain malachite, chalcopyrite, black vanadium minerals of micaceous habit, metatyuyamunite and microscopic grains of an unidentified black uraniferous substance. The proportion of copper, uranium, and vanadium is variable and any metal may be dominant. The metals probably were derived from pre-Cambrian granitic rocks. Copper and minor amounts of uranium were deposited in local stagnant basins by reaction with hydrogen sulfide. and decaying organic material. The uraniferous shales and the copper deposits are believed to be syngenetic, or nearly so, but the uranium deposits in sandstone are epigenetic and probably were deposited from ground waters with a possible hydrothermal admixture. The uranium and vanadium may have been reconcentrated from earlier, low-grade, syngenetic deposits.

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