New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

The Proterozoic Tajo granite consists of six outcrops along two northwest-striking faults east of Socorro, New Mexico. The area was originally examined for uranium, but fluorite and rare earth elements (REE) are reported as well. REE consist of the 15 lanthanide elements, including scandium and yttrium, are critical minerals, and are fundamental to modern society. REE deposits are rare in the world. Some Proterozoic granites in New Mexico, including the Tajo granite, contain uranium and REE, but their mineral-resource potential is unknown. We conducted a petrographic and geochemical study of the Tajo granite to determine the mineral-resource potential. The Tajo granite is medium-to coarse-grained, peraluminous, A-type granite, but it is relatively low in REE and uranium concentrations and not economic at this time. Geochemical comparisons of the Tajo granite to other Proterozoic granites found in central New Mexico, including Proterozoic granites found in the Gallinas and Los Pinos Mountains show that Tajo granite has an unusual composition. The Tajo granite is enriched in Rb, U and Th compared to the other Proterozoic granites, and depleted in CaO, Na₂O, and Sr. Future studies are needed to determine why the Tajo granite is depleted in REEs.