Isotopic Tracing of Rapid CO2 Mineralization Experiment using the Paraná Flood Basalts

CO₂ capture and storage in geological reservoirs have the potential to significantly mitigate the effects of anthropogenic gas emissions on global climate. In contrast to storage in soils and organic matrix, CO₂ geostorage occurs through the precipitation of carbonate crystals, which require less monitoring and may take a long time to return to the atmosphere. Here, we report the results of the first laboratory experiments of CO₂ injection in continental flood basalts of South America. We only used CO₂ and water to form carbonic acid during injection, a natural solution. The results reveal that the analyzed basalts have a mineral assemblage, texture and composition that efficiently allows a fast carbonate precipitation that starts 72h after injection. The carbonic acid reacted with basalt and formed stable carbonate minerals such as aragonite-calcite (CaCO₃) (80%) and dolomite (MgCa(CO₃)₂) (20%). The isotopic ratios of strontium (⁸⁷Sr/⁸⁶Sr = 0.7074 to 0.7076), carbon (δ¹³C = -4 to -12) and oxygen (δ¹⁸O = -3 to -7) also supported the observation that the precipitated carbonates originated from the carbonic acid solution that percolated into the basalt. Thus, the proposed experiment efficiently converted carbon dioxide from a gas phase into a crystalline solid permanently stored in the subsurface. Furthermore, our findings demonstrate that converting CO₂ into carbonate minerals within basalt rocks takes only a few days. Likewise, this is the first experiment demonstrating the safe long-term storage potential of anthropogenic CO₂ emissions through precipitation of carbonates in the Paraná continental flood basalts of South America.