Plagioclase vs. Olivine: Which mineral is more reactive in driving in situ mineralization of CO₂ in Basalt?

The reactivity of basaltic minerals toward CO₂ mineralization remains debated: laboratory studies at low temperatures identify plagioclase as the most reactive, while reservoir-scale experiments emphasize olivine. This study reconciles the apparent contradiction by establishing that mineral reactivity is not an intrinsic property but a condition-dependent outcome governed by temperature, pressure, pCO₂, and fluid chemistry. Through a synthesis of experimental and modelling evidence, we construct a unified framework incorporating five key controls: dissolution kinetics, surface accessibility, geochemical environment, cation stoichiometry, and reaction timescale. Under near-surface laboratory conditions (25–50 °C, acidic pH), plagioclase dissolves rapidly via proton-promoted hydrolysis, releasing Ca for early carbonate formation. At reservoir conditions (100–200 °C, high pCO₂, saline or wet supercritical CO₂), olivine dominates, showing 1–2 orders of magnitude higher dissolution rates and facilitating fast Mg-carbonate precipitation before silica passivation slows reactivity. Intermediate conditions (50–100 °C) yield mixed Ca- and Mg-carbonates, highlighting the futility of single-mineral extrapolations. Pyroxenes remain kinetically sluggish in all regimes. This perspective demonstrates that successful in situ mineralization depends on engineering reservoir conditions, optimizing temperature, salinity, and fluid pathways rather than simply selecting mineral-rich targets. By reframing mineral reactivity as a dynamic, environment-driven function, this study provides a mechanistic foundation for improved experimental design, predictive modelling, and site selection in CO₂ storage operations within basaltic formations.