The emplacement of an intraplate volcanic system in the Xiangshan Basin, Southeast China, implied from resistivity constrained 3D gravity and magnetic joint inversion

The intraplate volcanic system in Xiangshan basin provides the main source of ore-forming materials for the world's third-largest volcanogenic uranium deposit. Although geological evidence suggests the existence of two volcanic cycles, the geometries of complete volcanic systems remain enigmatic and are not fully understood, as are the underlying emplacements responsible, due in part to the lack of sufficient geophysical data. To refine the structure of the volcanic system, we applied a gravity-magnetic joint inversion constrained by the resistivity model. The results delineated the first volcanic cycle rhyodacite conduit beneath the Shutang area in the western basin, characterized by high susceptibility and dipping southwest in the shallow subsurface, with its emplacement controlled by a low-density east–west-trending basement fault activated by regional north-south extension stresses. The second volcanic cycle porphyroclastic lava conduit, characterized by low density and high susceptibility, dips southeastward and extends toward the northeast flank of Mount Xiangshan. In the west, the high susceptibility of the first-cycle volcanic conduit suggests that the second-cycle porphyroclastic lava conduit may have inherited the earlier magmatic pathway, with its emplacement jointly controlled by low-density regional north–south basement faults activated by east–west extension stresses and pre-existing east–west structures. These results underscore the dominant role of regional tectonic environments in controlling the multi volcanic cycles and provide new insight for emplacement mechanisms in a strike-slip extension environment. • First resistivity-constrained density–susceptibility variation-of-information joint inversion at Xiangshan: enhances shallow imaging and reduces non-uniqueness. • Resolution of two-cycle conduit geometry—especially the pipe-like first-cycle conduit: fills the regional gap in defining the spatial distribution of early volcanic conduits. • Orthogonal basement faults linked to alternating extension: regional tectonics govern multi-cycle emplacement in a strike-slip–extension setting.