75-15 Comparative geochemical analysis of the critical minerals potential of mafic rocks in the Zuni Mountains and Black Hawk District, Western New Mexico

Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

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Abstract:

Investigating factors that cause movement and alteration of hydrothermal fluids is a useful method to understand the mobility of critical minerals. This study characterizes alteration and critical minerals potential of Mesoproterozoic mafic bodies within the Zuni Mountains (Cibola County) and in the Black Hawk district of the Burro Mountains (Grant County). The Black Hawk district is an arsenide five-element vein system containing Ag, Ni, Co, As, and Bi. The mafic rocks in the Zuni Mountains, which predominantly consist of hornblende, were thought to have critical mineral potential, whereas the rocks in the Black Hawk district are considered a source of Co and Ni found within the arsenide five-element veins. The Zuni mafic rocks alter on a gradient of hornfels-granitoid to a weakly foliated amphibole. As the material grades, rare earth elements (REEs), Co, and Ni become depleted as sulfide minerals increase in conjunction with the increase in serpentinization (also denoted by elevated Mg content). Amphiboles from the Black Hawk district show a lower grade of alteration and removal of REEs. Based on petrographic analysis, samples predominantly consist of amphibole, calcite, plagioclase, and quartz with inclusions of hematite, magnetite, and pyrite metals as well as a variety of alteration states of minerals. Geochemical analysis shows that Zuni samples are elevated in Ni (up to 1005 ppm), Co (up to 140 ppm), Cr (up to 2180 ppm) and Black Hawk district samples are elevated in Cu (up to 8510 ppm), Ni (up to 220 ppm), Sr (up to 960 ppm), and Zn (up to 2790 ppm). Preliminary findings reveal a trend relating to alteration of both the Zuni Mountains and the Black Hawk district through hydrothermal fluids, as Na and P increase within the Black Hawk district, Ca and REEs dissipate, while Co and Ni remain in the host rock. In the Zuni Mountains, as Mg elevates, so do Cr and Ni, suggesting the effect of serpentinization.

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

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