149-6 Trapped Secrets of Hicks Dome: Fluid-Melt Inclusions Reveal Carbonatite Breccia and Mississippian-Valley Type Deposit Connection

Session: Research to Accelerate Recovery of Critical Minerals from Primary and Secondary Resources (Posters)

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Abstract:

The global shift toward green energy has increased demand for critical metals, particularly rare earth elements (REEs), which are essential for technologies such as electric motors, wind turbines, and high-performance electronics. The world-class Hicks Dome deposit, located in southern Illinois within the Wauboukigou Igneous Province (WIP) and the Illinois-Kentucky Fluorspar District (IKFD), is a unique structural and mineralogical feature where Permian REE-enriched carbonatitic breccias were overprinted by Mississippi Valley-Type (MVT) mineralization. The breccias at Hicks Dome are composed of quartz, calcite, dolomite, fluorite, and REE-bearing phosphates phases and are spatially associated with Permian carbonatites and lamprophyre dikes. Although the IKFD is one of the world’s largest fluorite districts, the genetic connection between the carbonatitic intrusions, breccia formation, and surrounding MVT deposits remains unresolved. This study examines fluid and melt inclusions in core samples from Hicks Dome and nearby MVT deposits to gain a deeper understanding of the mineralizing environment. Preliminary fluid inclusion analyses reveal a wide variety of fluid inclusions from aqueous liquid-rich, vapor-rich, and solid-rich (halite), CO₂-liquid-rich and polycrystalline inclusions, which may represent melt inclusions. Raman spectrometry of vapor bubbles is applied to estimate CO₂ densities, offering insight into trapping conditions and fluid evolution. These initial findings, along with continued investigation, aim to establish a geochemical and petrological framework for the emplacement of the breccias as the carbonatite is emplaced, and the possibility of further mineralized bodies in the region. Further analysis will also explore the role of fluorine, the potential source of fluids, and how the WIP may have influenced fluorite mineralization across the district. Understanding these processes provides valuable insight into REE behavior in carbonate-hosted systems and may help refine exploration models for critical minerals in similar geologic settings.

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

doi: 10.1130/abs/2025AM-9107

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