Critical mineral recovery and carbon storage potential at the Tamarack intrusive complex

The Tamarack Intrusive Complex (TIC), located in Minnesota, USA, is a globally unique ultramafic lithology consisting primarily of poorly consolidated peridotite. CO 2 enhanced mineral recovery (CO 2 -EMR) strategies may be implemented in deep ultramafic formations, including in the Tamarack Bowl intrusion olivine (BIO), to store injected carbon while recovering critical minerals. To better understand the TIC BIO’s unique potential for carbon mineralization and critical mineral mobilization, samples from a Tamarack BIO borehole were analyzed with a suite of geochemical and mineralogical tools. We employed micro-X-ray fluorescence spectroscopy mapping and X-ray photoelectron spectroscopy to understand elemental distributions and quantify spatially resolved chemical compositions on olivine grain surfaces. We captured samples’ bulk mineralogy with X-ray diffraction and scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. This analysis reveals that Tamarack BIO is rich in nickel-bearing forsteritic olivine, suggesting critical mineral extraction via nickel mobilization may be achieved during carbon mineralization-driven dissolution. The non-reactive carbon storage potential in the Tamarack BIO resource ranges from 0.85–117 million metric tonnes (MMT) of CO 2 based on our various reservoir property estimations. Results of our geochemical analyses for the Tamarack site indicate that if only 5% of the BIO was accessed with CO 2 -EMR, fluid-rock reactions could enable recovery of up to 4.1 MMT Ni and 1.2 MMT Co and permanently mineralize 1.4 billion metric tonnes of CO 2 . Given the significant revenue potential of critical mineral export, the TIC exhibits unique potential both as a domestic critical mineral source and a gigaton-scale carbon storage site in the United States.