GMEG - Geology, Minerals, Energy, & Geophysics Science Center
Antimony in and around the Yellow Pine deposit, central Idaho
Antimony is a critical mineral commodity for advanced technological uses and the US imports over 70% of antimony consumed domestically. Most of our imported antimony comes from China, which is beginning to reduce its production. Understanding of the origin of this deposit, the largest known antimony deposit in the US, would aid in future exploration for undiscovered deposits of this type, both domestically and internationally.
Document the origin of the Yellow Pine gold-antimony deposit and, by extension, the origin of this type of deposit. Our goal is to understand the structural, tectonic, and magmatic setting of the deposit, the character of the ore-transporting fluids, the conditions of ore deposition, and the regional stratigraphic framework and geochemical ore controls of metasedimentary packages that host some of the ore bodies. These studies should lead to a clearer model of this type of antimony deposit.
This will be a 3-pronged study of the Yellow Pine deposit aimed at understanding the controls of this important mineralization.
Structural, stratigraphic and ore deposit studies at the Yellow Pine antimony-gold deposits at Stibnite, Idaho
Structural studies will focus on the geometry, style, offset features, kinematics, age constraints, pressure-temperature constraints, and structural evolution within the four major fault zones in the study area: the ore-controlling Meadow Creek fault, the ore-controlling West End fault, the parallel Profile Gap-Johnson Creek shear zone (which also hosts antimony prospects) 10 km to the west, and the unnamed fault bounding the Eocene Thunder Mountain caldera 5 km to the east. New geochronological analyses will be used to constrain movement on these faults, as well as the age of mineralization.
Ore deposit studies will first work with the mining company staff to document the known geometries of the ore bodies, their chemistry and mineralogy, their alteration haloes and the existing age constraints on ore deposition. A sampling program will be developed utilizing exposures in the mining area as well as available drill core. Samples will be selected which preserve fluid inclusions in ore and gangue minerals within the deposit. We also plan to analyze Ore fluids will be extracted and analyzed for their chemical and isotopic composition to document the nature of the ore transporting fluids prior to ore deposition. Further characterization of ore and gangue mineralogy may also be warranted.
Investigation of metasedimentary roof pendants that host some of the antimony ore bodies will focus on four topics: