Abstract:
Objective Understanding the lithospheric thermal structure is significant for exploring the dynamics of a basin's thermal evolution, as well as for the assessment, exploitation, and utilization of geothermal resources in a basin. However, the limited data on heat production in the Yinggehai Basin has constrained research into the lithospheric thermal structure of the basin.
Methods Using natural gamma-ray (NGR) logs from 23 wells in the Yinggehai Basin, this study calculated the heat production rates of strata in the central depression using the fitted gamma-ray value (GR) - radiogenic heat production rate (A) empirical formula. Based on the ocean bottom seismometer (OBS)-derived crustal velocity structure model, this study established a parameter column of the heat production rates of strata. Accordingly, this study calculated the crustal and mantle heat flow, the crustal-mantle heat flow ratio, Moho temperature, and thermal lithospheric thickness, thereby determining the lithospheric thermal structure.
Results and Conclusions The results indicate that the central depression of the Yinggehai Basin exhibits crustal heat flow ranging from 19.2 to 27.1 mW/m2, with an average of (23.5±2.8) mW/m2; mantle heat flow from 49.2 to 57.2 mW/m2, with an average of (52.8±2.8) mW/m2; Moho temperature from 613 to 707 ℃, with an average of (671±31) ℃, and thermal lithospheric thickness from 61.23 to 64.89 km, with an average of (63.58±1.35) km. With a crust-mantle heat flow ratio of 0.45, the lithospheric thermal structure is characterized by cold crust and hot mantle, indicating the impacts of deep heat sources on the thermal state of the central depression in the Yinggehai Basin. The results of this study not only provide a scientific basis for further exploration and exploitation of geothermal resources in the central depression but also serve as a valuable reference for research on the geodynamics of the basin.
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