113-18 Searching for the W: a Mineralogical and Textural Investigation of W-bearing Ores for Domestic Critical Mineral Exploration in Northeast Washington, USA

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

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Abstract:

Critical minerals are non-fuel minerals vital to a country’s economic and national security but are vulnerable to supply disruptions. This research, in partnership with the Washington Geological Survey (WGS) and Earth Mapping Resources Initiative (Earth MRI), aims to better understand critical mineral resources available in Washington state, particularly in northeast Washington, where there is a high density of critical mineral occurrences that can help guide exploration and reveal associated economic materials in the area. The inactive Talisman and Big Iron mines, located in the Orient quadrangle, lie in the footwall and hanging wall of the Kettle metamorphic core complex, respectively. Both mines contain the critical mineral tungsten (W), but existing data are insufficient to assign deposit type, hindering further exploration. The purpose of this project is to 1.) determine the mineral assemblages and textures of W-bearing ores from both mines, 2.) interpret the ore deposit type to better understand the origin of critical minerals within the broader geologic context of northeast Washington. Samples from each mine site were collected to capture a comprehensive range of the minerals, textures, and rock types available at each site and include marbles, skarns, calc-silicate rocks, and granitic pegmatites. Thin sections were made of each sample type and analyzed to quantify chemical and textural information by using transmitted and reflected light microscopy, scanning election microscopy with energy dispersive x-ray spectroscopy (EDS) and cathodoluminescence (CL) detectors, and by X-ray diffraction (XRD). Preliminary results show an abundance of calc-silicate minerals, (i.e. andradite, actinolite, and epidote) across all samples, indicative of a skarn deposit environment, which commonly host ore deposits. Texturally early minerals in the Talisman samples show sphalerite, andradite, and augite with texturally late magnetite, epidote, calcite, actinolite, and chlorite. Disseminated scheelite (a tungsten ore) exhibits texturally ambiguous characteristics, but reveals multiple stages of growth and resorption in CL. Big Iron samples show texturally early quartz, and magnetite, with secondary textures including pyrite, calcite, ankerite, and chlorite. The minerals present in all samples support a relatively oxidized environment based on Mo-poor scheelite observed in EDS, lack of subcalic garnet, abundant epidote (the dominant hydrous phase), and the greater occurrence of pyrite relative to pyrrhotite.

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

doi: 10.1130/abs/2025AM-10791

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