Cenozoic Tectono‐Thermal Modeling of the Leiqiong Region, Beibuwan Basin, South China: Insights Into the Geodynamic Mechanisms of Late Cenozoic Volcanism

Abstract The Beibuwan Basin is a Cenozoic extensional basin whose Leiqiong region hosts the youngest intraplate volcanic field in South China. Although a mantle plume has been proposed for this magmatism, its location and timing, along with the crustal melting condition, remain controversial. The tectono‐thermal evolution of this basin, critical for understanding geodynamic processes and geothermal genesis, remains poorly constrained. Here we employ a multi‐episodic finite extension model to quantify lithospheric stretching factors, strain rates, and thermal structure along three profiles and 19 wells. Results show total stretching factors ranging from 1.04 to 1.76, with peak strain rates during the Paleocene, middle Eocene, and Oligocene. Basement heat flow increased progressively from 60 to 62.5 mW/m 2 at 65 Ma to 67–85.5 mW/m 2 at 23.5 Ma, subsequently decreasing to 65–82 mW/m 2 at present, indicating incomplete lithospheric thermal equilibration. Present‐day Moho temperatures vary between 534°C and 735°C, with average Curie interface depth and thermal lithospheric thickness of 22 and 78 km, respectively. Mean present‐day mantle heat flow is 45 mW/m 2 , constituting 69% of the terrestrial heat flow. Model results indicate that Paleogene extension greatly enhanced mantle heat flow and temperatures, promoting potential crustal melting at 25–35 km depth. Limited anomalous post‐rift subsidence, accompanied by localized uplift during the early Miocene and Quaternary, indicates the presence of hot mantle upwelling that provided an additional heat source. These findings offer geothermal evidence that the interplay between lithospheric extension and hot mantle upwelling drove the late Cenozoic magmatism in the Leiqiong area.