Southeast Asia contains significant natural geothermal resources. The structure of the geothermal anomalies, which have been affected by extension, are characterized by northeast trending normal faults surrounded by Mesozoic magmatic intrusions. In order to study the relationship between tectonic movements and geothermal resources, Bouguer gravity data of Guangdong province is inverted to determine the crustal structure. Density sources from different depths are separated with multi-scale wavelet decomposition. Concealed granites are inferred from low gravity anomalies and these high radioactive granites correlate with the location of natural thermal springs. The locations of basins are delineated by high gravity anomalies. The granites and rift basins, which formed during the Mesozoic in an extensional regime associated with thermal and magmatic activity, resulted in the current geophysical and geothermal anomaly.