© 2016, Springer-Verlag Berlin Heidelberg. The distinct element method was used to simulate chemical–mechanical–hydraulic processes that occur during serpentinization (volume-increasing hydration) within the oceanic lithosphere. The proposed model considers water transported in two ways: advective flow along fractures and through matrices. Variations in fracture pattern and system evolution were examined using two nondimensional parameters: the ratios of the rates of flow in fracture (ΨF) and matrix (ΨM) to the surface reaction rate. In cases of fixed ΨF and ΨM with sufficiently low reaction rates, the fracture pattern is not dependent on the surface reaction rate. Otherwise, the fracture pattern varies systematically as a function of ΨF and ΨM. At low ΨF (≤1) and low ΨM (≤1), the reaction proceeds from the boundaries inward and forms fine fractures layer by layer. At high ΨF (≥10,000) and low ΨM (≤10), the reaction proceeds from the boundaries inward and forms polygonal fracture networks. As ΨM increases (>100), the reaction tends to proceed homogeneously from the boundaries without fracturing. A comparison of natural and simulated textures reveals that the following conditions are necessary to develop mesh textures during serpentinization in the oceanic lithosphere. (1) The surface reaction rate must be similar to or higher than the fluid flow rate in the matrix (or than the diffusive transport of water), and much lower than the fluid flow rate along fractures. (2) Original olivine grain boundaries act as pathways for fluid transport; these pathways may result from thermal or tectonic stress-induced cracking prior to serpentinization.