Lithospheric Melting and Gold Mineralization in the Southwestern Cathaysia Block: Constraints From Magnetotelluric Evidence

Mesozoic Paleo‐Pacific plate subduction was dominant and drove intense continental reworking in South China, coupled with voluminous magmatism and episodic mineralization events. However, the lack of detailed geophysical constraints on the lithospheric architecture of southwestern Cathaysia Block hinders resolution of its alteration mechanisms and metallogenic evolution. We acquired magnetotelluric array data at 82 sites across southwestern Cathaysia Block, constraining the lithospheric resistivity architecture of this region. Integrating laboratory measurements of mantle minerals, broadband seismic data, and geothermal constraints, we quantitatively constrain the origin of lithospheric mantle conductivity anomalies. Research findings indicate that the crust in the study area is predominantly characterized by a high‐resistivity background, interspersed with linear conductive anomalies spatially correlated with fault zones. The conductive features in the lithospheric mantle likely result from the combined effects of partial melting and water in the mantle. Based on the regional tectonic framework, we propose that water released from previously subducted slabs and associated metasomatism weakened the lithosphere, potentially leading to delamination of the lithospheric root. This process, accompanied by slab collapse, triggered asthenospheric upwelling and thermo‐mechanical perturbations. Thermal erosion by the upwelling asthenosphere facilitated decompression melting within the thinned lithospheric mantle and the overlying, extended crust. The Paleo‐Pacific subduction system provided the necessary conduits for sourcing and transporting Au‐rich fluids, ultimately facilitating gold mineralization in the study area.