Insights on the magma reservoirs beneath the Xiangshan volcanic basin: Revealed by integrated magnetotelluric and petrological data

The Xiangshan volcanic basin hosts the largest volcanogenic uranium deposit in China. The host volcanic-intrusive complexes are the direct objects of the background study of metallogenic dynamics. However, the mechanism of its formation is still controversial. Given that the magma reservoir beneath the Xiangshan volcanic basin records the deep process of magma differentiation and evolution, the deep electrical structure and thermodynamic model were integrated to establish the dependence of melt fraction, temperature, and volatile phase content. Based on the high temperature and pressure petrophysical simulation and generalized three-phase Archie's law, the conductivity of each phase medium of the three-phase saturated magma reservoir and the bulk resistivity of the magma reservoir are estimated. The coupling relationship between the electrical parameters and the petrological data is finally established to find out the state of the Xiangshan magma reservoir. The results indicate that the highest volatile content of magma in the reservoir can reach 17 vol% and the highest melt fraction can reach 12 vol% based on the temperature pressure conditions and resistivity structure model of the crustal magma reservoirs here. This work provides new geophysical constraints and corroboration for the investigation of the formation mechanism of uranium-rich volcanic-intrusive complexes in the study area.

This work was funded by the National Natural Science Foundation of China (grants 42130811, 42304090 and 42374097), the Jiangxi Provincial Natural Science Foundation (20242BAB20143) and by the Autonomous deployment project of National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing, East China University of Technology (2024QZ-TD-15).