The Effects of Carbonate Precipitation on the Physical Properties of Basalt

To avoid the negative consequences of climate change, there is an urgent need to remove carbon dioxide from the atmosphere. Carbon mineralization—the conversion of injected CO 2 into stable carbonate minerals—offers a promising pathway for large‐scale, permanent geologic storage. While projects such as CarbFix have demonstrated its feasibility, optimizing and scaling in situ mineralization requires a deeper understanding of rock–fluid interactions and how carbonate precipitation alters rock properties. Previous studies have shown that elasticity, porosity, and permeability are all sensitive to mineral precipitation, but few have monitored their concurrent evolution. Here, we present flow‐through experiments on thermally cracked vesicular Iceland basalt in which permeability, porosity, ultrasonic velocity, and outlet fluid chemistry were tracked during carbonate precipitation from reactive fluids. Experiments were conducted with the apparatus inside an X‐ray micro‐computed tomography (CT) scanner, which provided 3D whole‐rock data sets at 11.5 m resolution every 20–40 min during flow. Results show that permeability decreases by one to two orders of magnitude within hours, while porosity declines by less than 4% over 24–90 hr. In contrast, ultrasonic velocity increases by up to 10% in step with permeability loss, demonstrating strong sensitivity to precipitation in critical flow pathways. Scanning electron microscope and CT imaging reveal a transition from dendritic and sheet‐like morphologies at high flow and supersaturation to rhombic calcite crystals as permeability and flow decrease. These findings highlight the coupling between precipitation dynamics, pore‐scale heterogeneity, and bulk rock properties, and offer avenues for optimizing and monitoring carbon mineralization in the field.