Three‐dimensional numerical simulation of fluid flow and heat transport within the Barbados Ridge accretionary complex

Abstract

The thickness of the Barbados accretionary prism varies along strike. The increased thickness of the prism to the south is believed to affect the transport of heat by fluids, resulting in anomalously high heat flow at the deformation front. We utilized a coupled three‐dimensional numerical fluid flow and heat transport model to investigate the effect of variable accretionary prism thickness on fluid flow patterns and heat transport in the décollement zone. The variation in sediment thickness produced along‐strike fluid flow in the more permeable décollement. Although surface heat flow is higher for simulations where flow occurs along both the décollement and underthrust sediments, the resultant advective heat transport was not sufficient to appreciably raise steady state surface heat flow at the latitude of the Ocean Drilling Program transect. Simulated temperatures in the décollement were consequently much lower than in situ borehole measurements, suggesting an additional source of warmer fluid. We then investigated the transient hydrologic and thermal response of the system to enhanced fault permeability. Model results provide insight into the degree to which episodic faulting may drive fluid flow and heat transport within subduction complexes. A transient scenario in which décollement permeability was increased two orders of magnitude with fluid flow along both the décollement and underthrust sediments caused the temperature gradient at the location of the drill sites to increase by a factor of two within 7100 years. The results of the three‐dimensional numerical simulations indicate that while both along‐strike advective heat transport and transient fluid flow events should be considered in the heat flow distribution of the northern Barbados accretionary complex, the effects of episodic fluid flow are more significant.