Heat and fluid transport in the vicinity of the Corsair Growth Fault Zone, Texas Continental Shelf, Gulf of Mexico
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In the Texas continental shelf off Mustang Island, geothermal gradients in the vicinity of the Corsair growth fault zone are elevated (0.05 - 0.06 K/m) relative to those off the fault zone (0.02 – 0.03 K/m). It has been previously suggested that the Corsair faults might serve as conduits for hot fluids recently expelled from overpressured Mesozoic sediments. The present study examines potential mechanisms that cause the high geothermal gradients in the vicinity of the Corsair growth fault. To achieve this objective, I generate one- and two-dimensional basin models of heat and fluid transport through the sediments. A basin model is a computational model which reconstructs geologic history of a sedimentary basin and simulates the physical processes such as sediment compaction, heat and fluid transport. Such modeling has been performed along a 55 km profile line crossing the area of high geothermal gradients. The models confirm that 8 mW/m2 of additional heat is required to explain the high thermal gradients, if fluid flow along the faults is disregarded. Pore pressure gradients within the fault zone, and the Corsair faults geometry are favorable for occurrence of fluid flow. With high Darcy’s velocities (> 6 m/year), temperatures within the fault zone can be significantly elevated, though it depends on duration of flow, fluid budget and fault thickness. However, the models also raise another possibility, because the deep sedimentary and crustal structure of the study area has been poorly constrained by previously conducted seismic studies. It is also possible that the 8 mW/m2 of additional heat may be derived from the heat released from the basement. For example, some researchers have speculated that there was failed rifting along the Corsair fault zone in the early Cenozoic. Variation in basal heat and episodic fluid flow along faults are both viable mechanisms for explaining the observed high geothermal gradients, with additional basal heat suggested as the primary mechanism and fluid flow the secondary mechanism.