Microstructural Controls on Reactive Flow and CO2 Mineralisation in Basalts: A µCT, SEM, and Modelling Approach

This study investigates four Icelandic basalt types that vary in mineralogy, pore structure, and degree of geothermal alteration, with the aim of understanding how microstructural characteristics influence fluid flow and mineral precipitation in the context of CO₂ storage. Samples were imaged using X-ray micro computed tomography (µCT) and scanning electron microscopy (SEM), enabling multiscale characterisation of fracture networks, vesicularity, and microporosity. Particular attention is given to the effects of hydrothermal alteration, ranging from incipient to advanced, and presence of associated mineral phases such as zeolites and smectites, which modify pore connectivity and surface reactivity. In addition to the geological analysis, the study uses µCTconstrained pore network modelling to incorporate sub-resolution connectivity, resulting in permeability estimates that align with experimental measurements. This integrated approach provides insights into the role of the microstructure in controlling fluid migration and subsequent mineral trapping, and forms a basis for ongoing CO₂saline fluid-rock batch experiments.