42-4 Mineralogical Analysis of the San Carlos Epithermal Vein in Fresnillo, Zacatecas.

Session: Cordilleran Mineral Systems: Interdisciplinary Perspectives on Critical Metal Ore Deposits

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Abstract:

Fresnillo, Zacatecas, has for centuries been a mining district recognized for its great production of precious metals associated with Cenozoic magmatism in the central zone of Mexico. Although the San Carlos vein is one of the structures with the highest content of economic mineral in this district, it lacks detailed mineralogical studies. Through the analysis of hand samples, petrography, electron microscopy (FE-SEM), and microprobe (EPMA), this work presents a multi-scale description (i.e., macro, micro, and nano) of the mineralogy of the San Carlos vein and its implications for the deposit's evolution. This information allowed establishing the growth sequence of the vein, which shows a dominance of pyrite, galena, sphalerite, quartz, and carbonates, with variable proportions of iron oxides (hypogene), acanthite, and Ag sulfosalts (e.g., proustite-pyrargyrite). The mineralogy and texture in the deposit define a vertical and lateral zoning, with Ag sulfosalts being characteristic of the shallow levels, while Ag sulfides (to a lesser extent) and iron oxides predominate in the deeper zones, generally associated with carbonates. These observations allow refining the genetic-evolutionary model of the San Carlos vein, providing new exploratory guides for the Fresnillo area.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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