Heat flow and thermal structure of the East China Sea

Abstract

Heat flow and thermal structure are crucial for understanding the tectonic evolution and geodynamics of marginal seas. The East China Sea (ECS) occupies a unique position within the West Pacific marginal seas system, characterized by the existence of the actively spreading Okinawa Trough-a back-arc basin in its early evolutionary stage. However, the thermal regime of the ECS remains poorly constrained, due to limited data coverage and variable data quality in previous compilations. Here we report some additional new heat flow data, and integrate all the geothermal data available from the ECS with thermal modeling, to depict the heat flow pattern of the ECS and thermal structure of the lithosphere there. The results show that the ECS is of typical heat flow pattern for the trench-arc-basin system. Amongst, the East China Sea continental shelf exhibits a moderate heat flow (<65 mW/m²), while the Okinawa Trough shows high heat flow with a large variability (>100 mW/m², except those extremely high values affected by fluid activities), and the heat flow for the Ryukyu Trench is quite lower (∼50 mW/m²). In contrast to the central and southern segments, the northern segment of the Okinawa Trough has a weaker crustal extension, resulting in a small geothermal gradient and a large lithospheric thickness. The thermal regime of the East China Sea is generally controlled by subduction process, but such environmental factors as magmatism and fluid circulation also contribute to local heat flow anomalies. For instance, the heat flow pattern of the Okinawa Trough is significantly influenced by strong fluid activities and magmatism, with the coexistence of high and low heat flow in the central and southern segments. The findings could not only provide a good example for exploring the relationship between heat flow and regional tectonics, but also is significant for hydrocarbon potential assessment in the East China Sea.