Investigation of Curie Point Depth in Sulu Ultrahigh-Pressure Metamorphic Belt, Eastern China

The Curie point depth of continental crust can reflect the regional tectonic pattern and geothermal structures. Analysis of magnetism is an efficient way to obtain the Curie point depth on a regional scale. This study systematically investigated the Curie point depth of Sulu ultrahigh pressure (UHP) metamorphic belt (33°40′N to 36°20′N and 118°E to 120°E, ca. 60 000 km²), eastern China using aeromagnetic data. The results show that the Curie point depth of the Sulu region varies from 18.5 to 27 km. The shallowest Curie point depth (ca. 18.5 km) is located in Subei subsidence, where the estimated temperature gradient value is about 31.35 °C/km, which is comparable with the measured value of 30 °C/km. In addition, a two-dimensional numerical solution of the heat conduction was used to calculate the temperature field to a depth of 30 km along the profile from Tancheng to Lianshui with a length of 139 km. The steady state model solved using the finite element method shows that the temperature around the Curie point depth is about 585.36 °C, which is close to the Curie temperature (580 °C) of magnetite at atmospheric pressure. These results provide new insights into the tectonic and continuous thermal structures of the Sulu UHP metamorphic belt.