112-11 Aeromagnetic and radiometric analysis data targeting pegmatites and carbonatites enriched with anomalies of REE in the northwest of Oaxaca, Mexico.

Session: Geophysics in Investigating and Exploring for Mineral, Energy and Groundwater Resources (Posters)

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Abstract:

Rare Earth Elements (REEs), along with critical minerals, including U and Th, are essential for modern technologies supporting the global energy transition and climate change mitigation. North American production of REEs remains limited, highlighting the need to identify new sources. This study investigates a potential REE-bearing province in the Oaxaquia microcontinent, a Mesoproterozoic terrane in southern Mexico associated with the Grenvillian orogeny. Oaxaquia comprises high-grade metamorphic rocks anorthosite-mangerite-charnockite-granite (AMCG) and a dense network of dikes and pegmatites, the latter being mineralogically complex and emplaced before, during, and after the orogeny. Field work, petrographic analysis, and geochemical data reveal that pegmatites in northwest Oaxaca are spatially associated with carbonatites and exhibit elevated REE concentrations (>2,000 ppm total REEs), as well as enrichment in U, Th, and K, with moderate radioactivity. These findings were integrated with a recent high-resolution airborne magnetic and radiometric survey. A strong spatial correlation exists between REE-enriched pegmatites and radiometric anomalies and magnetic anomalies that are aligned parallel to structural fabric. To prioritize exploration targets, we applied the Analytic Hierarchy Process (AHP), incorporating enhanced magnetic and radiometric datasets. Signal processing techniques—such as the first vertical gradient, analytic signal, Centre for Exploration Targeting (CET) grid analysis, and Euler deconvolution—highlighted five magneto-lithologic zones. High magnetic zones (>400 nT/m) are interpreted as possible intrusive centers. 3D Euler deconvolution suggests the intrusive bodies extend to at least 150 m depth. Lineament analysis from CET and analytic signal maps reveals dominant structural orientations coincide with magnetic and radiometric anomalies.

Radiometric ternary and K/Th ratio maps delineate areas of intense potassic alteration. The AHP-integrated model combined with field observations, ICP-MS geochemical data, and detailed petrography have identified multiple high-potential zones for future REE exploration and development.

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

doi: 10.1130/abs/2025AM-9600

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