hide
Free keywords:
-
Abstract:
Heat flow is reported at eight sites drilled into the Guaymas Basin, Gulf of California, during the International Ocean Discovery Program Expedition 385. This expedition seeks to understand the thermal regime of the basin and heat transfer between off-axis sills intruding the organic-rich sediments of the Guaymas Basin, and the basin floor. The relatively high sedimentation rates combined with active tectonism and voluminous shallow off-axis magmatism characterizes this basin. Our results bridge a data deficiency allowing basin-wide interpretations shading light on this young rift basin. Results show sedimentation corrected heat flow values range between 119 and 221 mW/m2 in the basin and between 257 and 1003 mW/m2 at the site of a young sill intrusion, termed Ringvent. Thermal analysis shows that heat in the Guaymas Basin is being dissipated by conduction for plate ages >0.2 Ma, whereas younger plate ages are also dissipating heat by advection. Drilling data show that an active ring of hydrothermal vent root to a shallow sill fueling low-temperature hydrothermal fluids with discharge velocities of 10–200 mm/yr. Possible recharge sites are located ~1 km away from the sill's border. Modeling of the heat output and assuming supplied by a cooling sill, we estimate a sill thickness at Ringvent of ~240 m. A simple order-of-magnitude model predicts that relatively small amounts of magma are needed to account for the elevated heat flow in non-volcanic, sediment-filled rifts like the central and northern Gulf of California where heating of the upper crust is achieved via advection by sill emplacement and hydrothermal circulation. Multiple timescales of cooling control the crustal, chemical and biological evolution of the Guaymas Basin. Here we recognize at least four timescales: the time interval between intrusions (~103 yr), the thermal relaxation time of sills (~104 yr), the characteristic warming time of the sediments (~105 yr), and the cooling of the entire crust at geologic timescales.
