Curie point depths in Northeast China and their geothermal implications for the Songliao Basin

Abstract

This work integrates processing and interpretation of the combined geomagnetic anomaly model of NGDC-720-V3.1 to better constrain thermal structures of the Northeast China lithosphere, which shows intensive extension and active volcanism during the Mesozoic and Cenozoic. Numerical tests demonstrate that magnetic anomalies calculated at 20 km altitude can be used for accurate Curie depth estimation. Averaged Curie depths using a 3D fractal exponent of 3.0 vary from ∼13±2.0 to 33±4.1 km with a mean of ∼22±2.4 km in Northeast China. With temperature-dependent thermal conductivity models constrained by incorporated surface heat flow and Curie depths in different geological blocks, the thermal lithospheric thicknesses are estimated mostly between 45 and 90 km based on 1D steady-state thermal conduction equation. Beneath the Songliao Basin, the Moho temperatures are abnormally high, ranging from ca. 700 to 1000 °C, and the mantle contributes about 65% of the total surface heat flow. The shallow Curie points and thermal lithosphere-asthenosphere boundary, together with high Moho temperatures and mantle heat flow, support abnormally high geotherms in the Songliao Basin, originated from hot upper mantle upwelling triggered likely by lithospheric delamination.