Journal Article

The Effects of Carbonate Precipitation on the Physical Properties of Basalt

O’Ghaffari, Hoagy, Simpson, Jonathan, Peč, Matěj, Elkhoury, Jean E., Chandra Mahavadi, Sharath

2026

Overview

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 CO2 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 (μ\\upmu CT) scanner, which provided 3D whole‐rock data sets at 11.5 μ\\upmu 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 μ\\upmu 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. Plain Language Summary To avoid the worst consequences of global warming, there is an urgent need to remove and store large volumes of carbon dioxide (CO2). One promising method is to inject it into volcanic rocks such as basalt, where it reacts to form solid carbonate minerals. This process, called carbon mineralization, locks CO2 away safely for geologic timescales. The technology is not yet widely adopted, partly due to limited understanding of how it changes basalt properties. In our laboratory experiments, we flowed reactive fluids through basalt samples while monitoring their internal structure with X‐ray scans, their ability to transmit fluids, and their response to sound waves. We found that the flow rate dropped by a factor of 10–100, even though only a small fraction of pore space was filled with carbonates. At the same time, the speed of sound waves increased, showing they are sensitive to small amounts of mineral growth in critical flow pathways. These results reveal that where and how minerals grow inside rocks strongly controls how fast the process proceeds. They also suggest that seismic waves could be used in the field to monitor carbon mineralization underground, helping manage projects to safely store large volumes of CO2 in basalt. Key Points Integrated timelapse micro‐CT and multi‐parameter monitoring reveals how carbonate precipitation evolves in basalt at pore‐scale resolution Ultrasonic velocity rises sharply, showing sensitivity to precipitate location and flow pathway clogging Flow rate and pore geometry control crystal growth, providing potential levers to optimize mineralization efficiency and storage capacity

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: acoustic sensing / Basalt / Calcite / Carbon dioxide / carbon mineralization / Carbon sequestration / carbonates / Climate change / Computed tomography / Crystals / Experiments / Heterogeneity / High flow / micro‐CT imaging / Mineralization / Permeability / Physical properties / Porosity / porous media / Precipitation / Rock properties / Rocks / Supersaturation / Temperature / Tomography / Velocity