Critical Mineral Resources in the Cornudas Mountains, Otero County, New Mexico.

Abstract

Reexamination of the mineral resources in the Cornudas Mountains is warranted in light of today’s economic importance of critical minerals that are essential in most of our electronic devices. The Cornudas Mountains form the northern Trans-Pecos alkaline magmatic province in the southern part of the North American Cordilleran alkaline-igneous belt. New mapping, petrography, 40Ar/39Ar geochronology, and geochemical analyses have provided a better understanding of the emplacement of the intrusions and associated mineral deposits in the area. The igneous rocks in the Cornudas Mountains were emplaced into Permian and Cretaceous sedimentary rocks in two pulses at 37.14–34.5 and 32.48–26.95 Ma, just prior to or during the early phases of Rio Grande Rift extension, and consist of (1) larger nepheline syenite–syenite laccoliths and plugs, (2) phonolite plugs, sills, and dikes, (3) smaller syenite plugs and dikes, and (4) volcanic breccia dikes. New U.S. Geological Survey geophysical data indicate that some of the larger intrusions extend into the subsurface as pipelike geometries, with additional buried intrusions potentially at depth that could be additional exploration targets. The focus of exploration for critical minerals in the Cornudas Mountains is for rare earth elements (REE), niobium (Nb), and zirconium (Zr) that are found within (1) the basal unit (PEnsp2) of the Wind Mountain nepheline syenite laccolith, (2) syenite-phonolite and volcanic breccia dikes and plugs, and (3) skarns and carbonate-replacement deposits in Chess Draw and Wind Mountain areas. Some samples contain as much as 3110 ppm total REE. REE could be leached from a mineral concentrate of REE-bearing minerals (eudialyte, zircon, monazite, bastnäsite, calciocatapleiite, vitusite, roumaite, xenotime). Pyrochlore (Nb), eudialyte (Zr), and zircon (Zr) are also found with the REE-bearing minerals and have potential for economic recovery. Another potential mineral resource is nepheline syenite for use as ceramics, glass, or other industrial use. 132 New Mexico Geological Society Guidebook, 73rd Fall Field Conference, 2023, p. 132–141, https://doi.org/10.56577/FFC-73.132