Nanoscale Interfacial Dissolution-Precipitation Reactions Drive Incipient Carbon Mineralization at the Tamarack Intrusive Complex Peridotite

The Tamarack ultramafic intrusion in Minnesota, USA may be suited to host concurrent carbon sequestration and critical mineral recovery. These dual capabilities are vital to reduce carbon emissions and supply metals (e.g. nickel) necessary for electric vehicles and other rapidly upscaling energy technologies. To understand carbonation reaction pathways and assess carbon sequestration potential in the Tamarack Intrusive Complex (TIC), we reacted a suite of Tamarack Bowl intrusion olivine (BIO) samples with aqueous-dissolved and liquid or supercritical CO2 (scCO2) at 90 bar and 21-90 °C to simulate a range of subsurface conditions. Samples were characterized pre- and post-reaction with multiple geochemical and mineralogical techniques, and results indicate mineral dissolution followed by magnesite precipitation. Pseudo in situ Identical Location Transmission Electron Microscopy (IL-TEM) experiments revealed that a carbonation reaction of TIC BIO peridotite with water-saturated scCO2 formed aragonite nanocrystals on an altered plagioclase surface and induced dissolution of nickel-bearing forsteritic olivine. The presence of nanoscale-resolved carbonation products identified by IL-TEM, coupled with carbonate transformation rates quantified in batch reactions, suggests that the TIC BIO resource can conservatively store 320-1,070 million metric tonnes (MMT) of CO2 via mineralization while mobilizing 0.9-3.1 MMT of nickel if only 5% of the TIC rock volume is accessed.