CRITICAL MINERALS IN PORPHYRY COPPER DEPOSITS IN NEW MEXICO

New Mexico lies at the eastern edge of one of the world’s great metal-bearing provinces hosting numerous Laramide porphyry Cu deposits. Porphyry Cu (Mo, Au) deposits are large, low-grade (<0.8% Cu) deposits that contain disseminated, breccias and stockwork veinlets of Cu and Mo sulfides associated with porphyritic intrusions. These Cu deposits typically are found in and around relatively small porphyritic diorite, granodiorite, monzonite, and quartz monzonite plutons that were intruded at relatively high crustal levels, commonly within 1-6 km of the surface, and are surrounded by crudely concentric zones of hydrothermal alteration. New ⁴⁰Ar/³⁹Ar dating and prior age determinations have constrained the New Mexico deposits into two periods. The older period (~78-71 Ma) includes Piños Altos (78.55±1.75 Ma), Copper Flat (Hillsboro district; 75.9±0.66 Ma), Oro (Eureka district; 71.4±0.19 Ma) and the younger period (~59-50 Ma) includes Lordsburg (59.25-57 Ma), Santa Rita (59.05±0.36 Ma), Hanover-Hermosa Mountain (Fierro-Hanover district, 58.3±0.7 Ma), McGhee Peak (Peloncillo Mountains, 57.28±0.65 Ma), Tyrone (55.2±0.6 Ma), Lone Mountain (50.6±1.9 Ma), Gold Lake (White Signal district), and Little Rock (Burro Mountains), districts. All of these deposits have potential for various critical minerals, including platinum group elements (PGE), Cu, Zn, Bi, Co, Ni, rare earth elements (REE), Te, and W that are found as micro-inclusions or in solid solution in sulfide minerals. Some of these critical minerals (i.e. PGE) are obtained from the anode slimes that are produced from copper smelting and refining. New and published geochemical analyses of ores, mineralized rocks, and mine wastes provide insights into potential critical minerals in these deposits. High Co concentrations are found in some of the Piños Altos samples (as much as 1026 ppm Co), whereas the Ground Hog mine in the Central district has as much as 64 ppm Te. Many of these critical minerals are found in the skarns adjacent to the porphyry copper deposits. Although most samples are low in TREE, a few deposits contain elevated TREE, including Piños Altos (409 ppm TREE), Santa Rita (717 ppm TREE), Fierro-Hanover (937 ppm TREE), and Oro (Eureka, 2272 ppm TREE). Although, these values are not normally economic, the large volumes of porphyry copper deposits mined enhance the economics of critical minerals in these deposits.