113-15 Geological and Geochemical Evaluation of a Cu-Au-W deposit in the Ferris Mountains, Wyoming

Session: Mineralogical Characterization of Economic Resources: From Critical Minerals to Gemstones (Posters)

Presenting Author:

Authors:

Abstract:

The Ferris Mountains Archean plutonic suite in south-central Wyoming hosts copper, gold, and tungsten mineralization that was mined briefly during the 1950s. Exploration in the 1970s identified the system as a potential porphyry copper deposit, with quartz-sulfide veins assaying up to 10,000 ppm copper and disseminated mineralization up to 1,800 ppm copper (Master, 1977). Subsequent USGS investigations reported copper values ranging from 7,000-20,000 ppm, along with anomalous concentrations of silver, lead, and gold (Mitchell & Neubert, 1988). Despite early identification of mineralization, the region’s potential for hosting critical and strategic resources has not been systematically explored.

This study aims to characterize the style of mineralization, define the deposit model, and evaluate the potential economic viability of the system. The Ferris Mountain pluton is primarily composed of porphyritic granite, intruded by quartz-sulfide veins, undeformed pegmatitic dikes, and mafic dikes. Field mapping and observations identify hydrothermal alteration concentrated along vein margins, dominated by K-feldspar, chlorite, and sericite alteration. Copper mineralization occurs as chalcopyrite, pyrite, and bornite within the quartz-sulfide veins, while wolframite is abundant along vein contacts. Disseminated sulfide mineralization in the host rock is weak, diminishing rapidly with distance from the vein. This spatial relationship is mirrored in alteration intensity, which also decreases outward from the veins. Bulk-rock geochemistry of mine tailings and outcrop samples supports these observations, with quartz-sulfide material averaging >1 wt% copper in some cases. Petrographic observations further constrain alteration trends and provide insight into the mineralization sequence.

Preliminary data supports a vein-hosted deposit model, rather than a classic porphyry system as suggested. Continued work will refine the deposit model and evaluate the potential for critical resource exploration in the region.

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

doi: 10.1130/abs/2025AM-9606

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