Geology and ore deposits of the Sacramento (High Rolls) mining district, Otero County, New Mexico

Abstract

In the Sacramento (High Rolls) mining district, Otero County, New Mexico, the Permian Abo Formation unconformably overlies folded and faulted rocks of pre-Permian age; in turn, it is overlain conformably(?) by the Permian Yeso Formation. Structure in the Abo and Yeso is relatively simple, being generally a monocline striking north and dipping gently east and cut by faults of moderate throw. The few intrusives in the district are sills of andesite with no associated mineralization or alteration.The Abo contains small, irregular deposits of copper and lead minerals occurring separately or associated in discontinuous, light-colored arkose beds sandwiched between red shales. Total production from these deposits through 1962 probably does not exceed 23,000 tons of lead ore varying between 5 and 11 per cent lead and 6500 tons of copper ore varying between 2 and 7 per cent copper. Minor amounts of other metals occur with these principal ore types.Evidence accumulated as a result of surface and underground mapping, a large number of assays, and extensive testing of favorable-appearing arkose beds with acetic acid and potassium iodide for lead sulfate and lead carbonate strongly suggests that the ores are "semisyngenetic" in origin. Copper and lead sulfides possibly were deposited with the arkose. The source of the metals has not been established. Both copper and lead sulfides later were oxidized and the metals reconcentrated to some extent as carbonates and sulfates by the action of ground water.Provided such an origin is correct, the overlying Yeso Formation and the underlying rock units, predominantly the Magdalena Group, contain no ore deposits that are genetically related to those in the Abo.