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).