216-4 Geochronology and Evaluation of Critical Minerals in Selected Eocene-Miocene Porphyry Copper and Mo-W deposits in New Mexico

Session: Geochronology of Critical Mineral Deposits with Special Reference to U-Th-Pb Dating of Common-Pb-Rich Minerals

Presenting Author:

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Abstract:

Understanding the geochronology of mineral deposits is important to determine what mineralizing pulse the district is associated with and therefore where critical minerals could be targeted for exploration. New Mexico lies at the eastern edge of a well-known metal-bearing province, hosting numerous Laramide and Paleogene mineral deposits. Southwestern New Mexico contains two spatially overlapping mineralization events; the Laramide porphyry copper (±Mo, Au) and Paleogene Mo-W deposits, and studies are ongoing to better understand their timing, scale and economical mineral potential. Porphyry copper deposits are generally large, low-grade deposits containing Cu, Fe, Mo, Au sulfides (and other metal sulfides) and exhibit characteristic alteration styles. Porphyry copper systems can also be spatially and temporally associated with skarn deposits, carbonate replacement deposits and polymetallic veins. Mo-W deposits within southwestern NM formed through extensional magmatism during the Eocene-Miocene period and tend to be of more felsic compositions. All these deposit types have the potential to host various critical minerals, including Cu, Zn, Bi, Co, Ni, rare earth elements (REE), Te, and W along with hosting significant Au, Mo, Re and Ag resources. Critical minerals may be found as substitutions within diffuse gangue minerals or concentrated as mineralized veins and hence their variability and abundance is important for the future economy of the U. S. The NM Laramide porphyry copper deposits and Paleogene Mo-W deposits have been constrained using current ⁴⁰Ar/³⁹Ar dating methods into three ore-producing magmatic pulses: 1) 78-71 Ma Laramide pulse, 2) 59-50 Ma, Laramide pulse, and 3) 40-30 Ma Paleogene Mo-W pulse. Historically many of these ages have shown less precise data through the K-Ar method or older U-Pb dates from the 1970s and 1980s. Some of the more recent ⁴⁰Ar/³⁹Ar age determinations have also shown some low precision results or give conflicting ages. Pluton emplacement and mineralization in the porphyry systems within southwestern New Mexico during the Laramide orogeny and Paleogene period overlap spatially. Recent findings show Mo-W deposits exhibit slightly different geochemical signatures in ore and vary from the Laramide porphyry copper deposits in terms of grade, mineralogy and scale. Deposits of similar ages share similar characteristics such as these found in the Paleogene Mo-W districts, tend to be elevated in Re & Te, Mo & W and are of smaller scales.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8955

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