Imaging the shallow magmatic system of the Xiangshan volcanic basin by the 3-D joint inversion of potential field data

The underlying magmatic system in the Xiangshan volcanic basin is crucial in controlling the origin and migration of ore-forming fluids and driving uranium element transport. However, its shallow structure still lacks high-resolution imaging constraints. Gravity and magnetic data are combined in a three-dimensional joint inversion to obtain structurally similar density and magnetic susceptibility models of the Xiangshan shallow magmatic system. As imaged by the obtained model, a steep tubular anomaly characterized by low density and high magnetic susceptibility beneath the main peak of Xiangshan, interpreted to be a volcanic conduit associated with the porphyroclastic lava. A tubular high-magnetic susceptibility anomaly that located approximately 3 km west of the Xiangshan main peak is also imaged, is presumed to be a rhyodacite volcanic conduit. Both of them converge at depth and exhibit a hereditary relationship. In addition, the east-west oriented low-density anomaly is likely a reflection of the depression zone in the metamorphic basement. It is speculated that the imaged regional structural framework could control the emplacement of shallow magmatic system. We argue that the deep magma intrudes along the basement fault zone and ascends through its derived secondary fractures, providing material and heat sources for shallow hydrothermal circulation.

This work was funded by the National Natural Science Foundation of China (grants 42130811, 42304090 and 42374097) and by Jiangxi Provincial Natural Science Foundation (20242BAB20143).