PNNL

Abstract

Geologic carbon sequestration in mafic and ultramafic reservoirs is a scalable carbon dioxide removal strategy, offering permanent storage via mineralization as stable carbonates. However, limited information currently exists on the structure and composition of key mineralization endpoints during sequestration. In this study, we unravel for the first time the atomic structure, composition, and nanoscale morphology of carbonates recovered from a field-scale demonstration of CO2 mineralization in basalt. We mapped mineralogical variations from the initial to later stages of subsurface carbonate growth and identified a previously unknown cation-ordered ankerite phase that exerts a primary control over carbonation processes. This study has provided a new understanding of subsurface carbonation pathways which will impact the parameterization of predictive geochemical models for future sequestration efforts in basalt formations.