Insights into the Thermal Structure of the Manila Trench from Curie Point Depth–Derived Heat Flow

Abstract

The thermal structure of subduction zones plays an important role in understanding lithospheric dynamics and can be inferred from surface heat flow data. This study presents the first Curie Point Depth-derived heat flow model for the Manila Trench region. Curie Point Depth (CPD) estimates were derived using magnetic anomalies from the World Digital Magnetic Anomaly Map (WDMAM) using spectral analysis applied to overlapping windows of varying sizes. The CPD results from 150 km, 180 km and 200 km window sizes were averaged to minimize spectral bias. The resulting CPD values range from 5 to 49 km and generally reflect expected trends, with shallow CPD beneath the South China Sea (SCS) basin and deeper CPD within the forearc region. Localized deviations in CPD are observed in the Qiongdongnan basin and eastern sub-basin. These are attributed to variations in lithospheric properties such as crustal and sediment thickness, and localized thermal effects. Heat flow was calculated from the CPD values assuming a uniform thermal conductivity, yielding a mean heat flow of 68 mW/m2 across the study area, covering portions of SCS and the Manila Trench region. Calculations using area-specific thermal conductivity improve heat flow estimates but reduce the overall mean. These results indicate that CPD-based heat flow estimation provides a robust first-order constraint on the thermal regime of the Manila Trench region. It demonstrates the applicability of using magnetic data for inferring heat flow in regions where direct heat flow measurements are not available.