PNNL

Abstract

Carbon-negative strategies such as geologic carbon sequestration in continental flood basalts offers a promising route to the removal of greenhouse gases, such as CO2, via the safe and permanent storage as stable carbonates. This potential has been successfully demonstrated at a field scale at the Wallula Basalt Carbon Storage Pilot Project where supercritical CO2 was injected into the Columbia River Basalt Group (CRBG). Here we analyze recovered post-injection side-wall core cross-sections containing carbonate nodules using ?-XRF chemical mapping techniques that revealed unique compositional zonation within the nodules. The exotic nature of the subsurface anthropogenic carbonates is highlighted by the near absence of Mg in an ankerite-like composition. Furthermore, a comparison between pre- and post-injection side wall cores along with an in-depth chemical mapping of basalt pore lining cements provides a better understanding into the source and fate of critical cationic species involved in the precipitation of carbon mineralization products. Collectively, these results provide crucial insights into carbonate growth mechanisms under a time-dependent pore fluid composition. As such, these findings will help parameterize predictive models for future CO2 sequestration efforts in continental flood basalts around the world.