Abstract: Geothermal regime is essential for understanding the tectonic mechanism and geodynamics of marginal basins. The East China Sea Shelf Basin (ECSSB), located at the junction of the Eurasian Plate and Pacific Plate, has undergone multiple tectonic deformation, making its tectono-thermal evolution complex. Present-day geothermal regime could provide tight constrains for understanding the tectono-thermal process. However, due to the limited coverage and ambiguous quality of previous heat flow data, the thermal regime of the ECSSB remains poorly understood, posing challenges in exploring the relationship between the geothermal regime and tectonics. This study reports 52 new heat flow data estimated from the industry boreholes in the ECSSB, and integrate previous data to revisit the thermal regime of the ECSSB. The results show that the ECSSB has an average geothermal gradient of 32.0 ℃ /km and a mean seafloor heat flow of 67 mW/m², consistent with the average value of continental China. In addition, the western depression zone shows an average geothermal gradient of 30.7 ℃ /km and an average seafloor heat flow of 65 mW/m², while the eastern depression zone exhibits an average geothermal gradient of 32.4 ℃ /km and an average seafloor heat flow of 71 mW/m2, indicating an increasing from west to east in thermal regime. This geothermal trend is quite consistent with the migration of rifting process within the ECSSB, associated with the rollback of the Pacific Plate subduction. It is concluded that the tectonic evolution of the ECSSB controls the geothermal pattern. Besides, the basement topography and the radiogenic heat contribution by granite base also account for the localized heat flow anomalies. The findings provide new clues for understanding the tectonics of the ECSSB and assessing the hydrocarbon potential.

Key words: geothermal gradient, seafloor heat flow, thermal regime, East China Sea Shelf Basin