Initial results of heat flow acquisition from a gas hydrate system on the Amazon deep sea fan

The Amazon deep sea fan is a dynamic setting in which widespread seafloor fluid vents record degassing of a gas hydrate system hosted within an upper slope thrust-fold belt linked to gravitational collapse of the depocentre. This system is to be investigated during the AMARYLLIS-AMAGAS campaign of the R/V Marion Dufresne, to take place in May-June 2023 as a collaboration between research groups in Europe and Brazil. One aim of the campaign is to study the spatial distribution and stability conditions of the shallow gas hydrate reservoir in relation to temperature changes in the past, fluid migration and venting, and to the triggering of the giant slope failures that have recurrently extended across the fan. Three heat flow transects within a 200 km2 area of the upper fan will target seismically-observed BSR (bottom simulating reflection) patches associated with fluid venting structures at the crests of thrust-fold anticlines. Temperature gradients will be measured using autonomous high-precision temperature probes attached to core barrels, while thermal conductivity will be measured onboard using a needle probe instrument on recovered sediment cores. Together with hydroacoustic and geochemical datasets to be acquired during the campaign, the results are expected to yield insights into the dynamics of the gas hydrate system in relation to subsurface fluid flow and changes in the heat flow in sediments, as well as new information on the poorly-constrained background regional heat flow regime of the Amazon deep-sea fan.