Hydrothermal Circulation Within Subducting Crust: Implications for Subduction Zone Temperature

Hydrothermal circulation plays an important role in cooling and redistributing heat within high-permeability ocean crust. We examine the effect of hydrothermal circulation on subduction zone temperature by modeling 2D fluid and heat transport within subducting ocean crust using a finite element heat and mass transport code. The effect of hydrothermal circulation is quantified by comparing results from simulations with coupled fluid and heat transport to those from simulations with only heat conduction (no fluid flow). We examine how sediment distribution, convergence rate, and subduction geometry influence hydrothermal circulation and temperatures within the subduction zone. Our model geometry mimics the Middle America subduction zone off Nicoya Peninsula, Costa Rica. We simulate fluid and heat flow for systems with upper basaltic basement permeability ranging from 10^{-13 to 10^{-10} m2. Additionally, we incorporate the effect of permeability reduction within the basaltic basement as it is subducted. The models with fluid transport show suppressed temperatures along the subducting slab relative to purely conductive models. In the subducting slab, convection cells develop along the entire length of the highly permeable upper basaltic basement and vary in width depending on permeability and distance from the trench.