Unraveling Dissolution‐Precipitation Evolution in Basalt During Supercritical CO 2 ‐Water‐Rock (CWR) Interaction: A Mesoscale Mechanical Perspective

Abstract Mineral carbonation in basaltic formations provides a geophysically grounded pathway for permanent CO 2 sequestration, as intrinsic dissolution‐precipitation processes convert injected CO 2 into stable carbonates. However, the long‐term integrity of reservoirs is governed not only by geochemical kinetics but also by meso‐mechanical performances of mineral grain interfaces during CO 2 ‐water‐rock (CWR) interactions. In this study, the coupled relationship between interfacial strength and mineral reaction pathways was quantitatively established, directly linking the geochemical alteration to mechanical stability in basalt. Supercritical CO 2 ‐water‐basalt interactions were conducted over 30–300 days under conditions of 10 MPa and 60°C, combining four‐point bending tests on a self‐developed meso‐mechanical measurement platform with post‐reaction SEM‐EDS analysis to quantify interfacial strength evolution and its coupling with mineral dissolution‐precipitation. Results reveal a three‐stage degradation in tensile strength: an initial activation phase (reduction up to 12.8%), followed by nonlinear decay (additional 9.9% loss), and stabilization after 150 days, well characterized by the proposed Weibull probabilistic model. In contrast, interfacial shear strength exhibited delayed weakening and partial recovery with CWR aging, attributed to tribo‐chemical restructuring and new mineral bridging that enhanced interfacial roughness. Microscopic observations revealed sequential carbonate precipitation, from pore infilling to grain‐boundary epitaxy and late‐stage bridging, that can impede fluid‐driven degradation and enhance shear resistance via geometric interlocking, while spatial coupled chemical weakening and precipitation‐induced stresses may still induce micro‐cracks. These findings demonstrate how grain‐scale processes mediate the feedback between geochemical reactions and mechanical stability, providing critical parameters for predictive modeling of fracture initiation and long‐term integrity in basaltic CO 2 storage reservoirs.