A simple model of reaction-induced cracking applied to serpentinization and carbonation of peridotite

Abstract

During chemical weathering there is the potential for a positive feedback process to occur: Chemical reactions cause volume changes, increasing stresses and potentially fracturing the rock. In turn, these fractures may enhance transport of chemicals through the rock, accelerating the weathering process. An idealised model of this feedback is presented. Simple scaling laws relate the speed of the weathering front to elastic properties, the rate of transport of reactants, and reaction rates. Five different regimes in the model are identified, although only two of these are appropriate for natural systems, where the reaction rate is a key control on the weathering rate. The model is applied to the carbonation and serpentinization of peridotite, chemical weathering processes which have potential industrial application in the storage of CO 2. If these weathering processes can be accelerated, CO 2 could be stored as carbonates in the peridotite in substantial quantities. This simple model suggests that it may be possible to boost the speed of the weathering front a millionfold by a combination of heating, increased partial pressure of CO 2, forced fluid flow, and hydrofracture.