A numerical model is developed and used to investigate the non-isothermal reactive fluid flow in a fracture. It considers the effect of thermal stresses and silica dissolution in a coupled fracture-matrix system using the dual porosity concept. The fluid flow is based on the Cubic law, and the transport mechanism in the fracture includes solute advection and dispersion. Solute mass exchange between the fracture and the rock matrix is accounted for using a lateral diffusion limited solute transport. The heat transfer between the fracture and the rock is modeled using a lateral conduction limited thermal flux from the reservoir into the fracture while heat transport within the fracture considers thermal advection, conduction, and dispersion. The pressure of the circulating fluid is allowed to vary keeping the discharge along the fracture a constant. As a result, the water velocity, the pressure change and the fracture aperture varies throughout the fracture. The numerical model is applied to examine the individual as well as the combined effect of thermal stress and mass of silica dissolved on the variation of fracture aperture between the injection and production wells with time. The resulting change in pressure distribution along the fracture is evaluated assuming a constant injection rate. Result suggest that there is a significant increase in fracture permeability and the associated pressure drop at the injection well may be mainly attributable to thermoelastic effects, while the increase in fracture aperture near the production well is mainly caused by silica dissolution.