Base-and precious-metal deposits in Lincoln and Otero Counties, New Mexico
Virginia T. McLemore
Base (copper, lead, zinc) and precious (gold, silver) metals have been produced in Lincoln, and to a lesser extent, Otero Counties from the 1880s to the present. Four types of deposits occur in these two counties: (I) placer (late Tertiary to Quaternary), (2) Great Plains margin (GPM, mid-late Tertiary), (3) sedimentary copper (Permian), and (4) veins and replacement in Proterozoic rocks. Three of the deposit types are defined primarily by age of host rock and presumed genesis (placer, sedimentary copper, and veins and replacements in Proterozoic rocks). The GPM deposits are defined by similar tectonic setting, similar age of formation, association of other metals, and form of the deposits. These deposits occur along the tectonic boundary between the stable Great Plains and the active Rocky Mountains or Basin and Range (including the Rio Grande rift). Only the GPM and placer deposits have economic potential in Lincoln and Otero Counties. Low-grade but large-tonnage placer deposits may occur in the Jicarilla district, and smaller deposits may occur in the White Oaks, Nogal and Orogrande districts. GPM deposits typically consist of gold-bearing breccia pipes and quartz veins, copper and/or lead/zinc skarns and iron skarns. Future economic potential of GPM deposits is good if large, low-grade, bulk-minable breccia-pipe deposits, similar to the Ortiz deposits in the Old Placers district in Santa Fe County, can be found in Lincoln and Otero Counties. Breccia pipes occur in the Gallinas, Nogal, Jicarilla and Orogrande districts, but the potential for gold is unknown.
- McLemore, Virginia T., 1991, Base-and precious-metal deposits in Lincoln and Otero Counties, New Mexico, in: Geology of the Sierra Blanca, Sacramento and Capitan Ranges, New Mexico, Barker, James M.; Kues, Barry S.; Austin, George S.; Lucas, Spencer, G., New Mexico Geological Society, Guidebook, 42nd Field Conference, pp. 305-309.