Facile Metal Release from Pore-Lining Phases Enables Unique Carbonate Zonation in a Basalt Carbon Mineralization Demonstration

& mu;-XRF chemical mapping analysiswas performed on recoveredsidewall cores from a geologic carbon sequestration field demonstrationsite. The results highlight the unique nature of the anthropogeniccarbonates and reveal novel insights into the importance of secondaryminerals in dictating the fate of CO2 in basalt reservoirs. Carbon-negative strategies such as geologic carbon sequestrationin continental flood basalts offers a promising route to the removalof greenhouse gases, such as CO2, via safe and permanentstorage as stable carbonates. This potential has been successfullydemonstrated at a field scale at the Wallula Basalt Carbon StoragePilot Project where supercritical CO2 was injected intothe Columbia River Basalt Group (CRBG). Here, we analyze recoveredpost-injection sidewall core cross-sections containing carbonate nodulesusing & mu;-XRF chemical mapping techniques that revealed compositionalzonation within the nodules. The unique nature of the subsurface anthropogeniccarbonates is highlighted by the near absence of Mg in an ankerite-likecomposition. Furthermore, a comparison between pre- and post-injectionsidewall cores along with an in-depth chemical mapping of basalt porelining cements provides a better understanding into the source andfate of critical cationic species involved in the precipitation ofcarbon mineralization products. Collectively, these results providecrucial insights into carbonate growth mechanisms under a time-dependentpore fluid composition. As such, these findings will enable parameterizationof predictive models for future CO2 sequestration effortsin reactive reservoirs around the world.