Gravity Anomalies and Lithospheric Flexure in Western Yunnan, China, Deduced From a New Dense Gravimetry

Abstract

AbstractWe conducted a dense gravity/GNSS survey in western Yunnan, China, and improved the precision of Bouguer gravity anomalies (BGAs) and Free‐air gravity anomalies (FGAs) by about 50 mGal. The BGAs showed that there was no significant BGAs abnormal change over the whole study area, and the density structure of BGAs inversion shows low‐density regions at 20–40 km depth beneath Tengchong and its surrounding areas. Meanwhile, we calculated the loading ratio of the lithosphere in western Yunnan based on merged FGAs using the gravity admittance method. The resulting ratios show that the lithospheric flexure in this region results from a combination of the surface, the internal crust, and the mantle, with the internal crust dominating. Combined with other geophysical results, we speculate that the origin of Tengchong volcanoes is not large‐scale mantle upwelling, but limited mantle material rising along the fracture in the process of material migration in the middle‐lower crust.