CO2-Based Leaching of Sulfidic Peridotite Drives Critical Mineral Mobilization and Carbonate Precipitation

The transition toward green energy requires both carbon dioxide removal and consistent supplies of energy-critical minerals. Injection and mineralization of supercritical CO₂ at active mafic- and ultramafic-hosted mines provide a potential avenue to achieve both, through the stable geologic storage of carbon and subsequent mobilization of critical metals. A sample from the Eagle occurrence, an ultramafic-hosted sulfide deposit in Michigan, United States, that is the only active Ni mine in the United States, was characterized both before and after reaction with supercritical CO₂ at elevated pressure and temperature. We present the changes in mineralogy, feature relocation, and potential for carbon mineralization and critical mineral recovery based on the comparison of pre- and postreaction data sets. Herein, we present evidence of dissolution–precipitation reactions leading to carbon mineralization and critical and strategic mineral mobilization (Ni, Mn, and Cu) driven by water-saturated supercritical CO₂ fluids, including the formation of aragonite and dissolution–reprecipitation of Ni-bearing phases. Collectively, these results will improve fate and transport models for carbon storage in ultramafic rocks, increase understanding of new unconventional sources for critical minerals, and provide a foundation for future studies on CO₂ enhanced mineral recovery (CO₂-EMR).