Mineral Carbonation: Processes, Mechanisms, and Its Role in the Carbon–Hydrogen Cycle

Mineral carbonation represents a promising carbon capture and storage (CCS) approach, offering permanent CO₂ sequestration via spontaneous reactions, abundant natural feedstocks, and low environmental impact. Mafic and ultramafic rocks, in particular, exhibit high carbonation potential due to their rich magnesium, iron and calcium content. This paper provides a systematically study of the reaction process, intrinsic mechanisms, and role of mineral carbonation in the carbon-hydrogen cycle. (1) Reaction process and mechanisms in mineral carbonation. Mineral carbonation is a dissolution– precipitation process involving Mg²⁺-, Ca²⁺-, or Fe²⁺-rich silicates (e.g., olivine, pyroxene) and CO₂-rich fluids. It proceeds through three stages: CO₂ dissolves to form carbonic acid, dissociating into HCO₃^- and CO₃^2- (stage 1); the resulting acidity promotes silicate dissolution, releasing metal ions (e.g., Mg²⁺, Ca²⁺) (stage 2); and metal cations react with carbonates ions to precipitate stable carbonate minerals (stage 3). Carbonation in peridotite and pyroxenite is often coupled with serpentinization, leading to the co-formation of carbonates and serpentine minerals. Under certain conditions, abiogenic H₂ and organic carbon are also produced, offering implications for astrobiology, early life origins, and clean energy. (2) Role of water in mineral carbonation. Water and H⁺ ions play a critical role in enhancing silicate dissolution, facilitating the release of Mg²⁺, Ca²⁺, and Fe²⁺. Carbonate ions from hydrated CO₂ combine with these cations to form stable minerals. In aqueous supercritical CO₂ systems, water content affects carbonation efficiency by influencing pore volume, while nanoscale water films regulate the types of carbonate mineral types formed. Silicate dissolution is typically the rate-limiting step, controlled by mineral structure and composition, and strongly influenced by pH, temperature, and water activity, etc. (3) Long-term reactivity and tectonic integration in carbon-hydrogen system. Effective reactivity is maintained through fluid overpressure, reaction-induced porosity, dissolution channels, and fracturing, which collectively enhance fluid infiltration and promote complete carbonation. Mineral carbonation across diverse tectonic settings and is closely linked to plate activity. It acts as a long-term carbon sink in oceanic and continental lithosphere, while subduction zones facilitate deep carbon and hydrogen transport into the mantle, driving the long-term global carbon-hydrogen cycle.