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

Abstract

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.