Equilibrium-approximated solutions to the reactive Lauwerier problem: thermal fronts as controls on reactive fronts in Earth systems

Abstract. Rates of subsurface rock alteration by reactive flows are often independent of kinetic rates and governed solely by solute transport. This enables a major simplification that makes models tractable even for complex kinetic systems through the widely applied local equilibrium assumption. Here, this assumption is applied to the reactive Lauwerier problem (RLP), which describes non-isothermal fluid injection into a confined aquifer, leading to chemical disequilibrium. Specifically, the thermal changes drive temperature-dependent solubility variations, leading to undersaturation and dissolution or supersaturation precipitation reactions. Using this framework, solutions for reaction rate and porosity evolution are developed and analyzed, yielding a time-dependent criterion for their validity that incorporates time and thermal parameters. A key feature – the coalescence of thermal and reactive fronts – is used to explore their evolution over time in different settings. The applicability of the equilibrium model for important fluid–rock interaction processes is then examined and discussed, including sedimentary reservoir evolution and mineral carbonation in ultramafic rocks. Notably, the approach used here to extend thermal solutions for reactive processes suggests broader applicability. The findings also highlight that thermally driven reactive fronts, particularly near equilibrium, often become stationary after a relatively short period. As a result, their spatial evolution is governed by geological processes operating over much longer timescales.