Deep mineralization processes in the middle and lower reaches of the Yangtze River, east China: Constraints from deep electrical structure

• Magnetotelluric imaging reveals the distribution of mantle upwelling and partial melting within the lower crust of the middle and lower reaches of the Yangtze River. • The resistivity model highlights subduction and delamination features in the lithosphere at the northern margin of the Yangtze Plate. • During the Yanshanian period, the strike-slip and extensional activities of the Tanlu Fault and the Yangxin-Changzhou Fault contributed to lithospheric delamination, magmatism, and mineralization in the middle and lower reaches of the Yangtze River. The middle and lower Yangtze River metallogenic belt (MLYB) is a major Cu-Fe-Au polymetallic province in eastern China. Despite extensive researches on its mineralization processes, the deep geodynamic process remain poorly constrained. This study utilizes magnetotelluric profiling across key tectonic domains from the southern part of the North China Block (NCB) to the Jiangnan Uplift to delineate lithospheric structure and its metallogenic implication. Our 2-D inversion of magnetotelluric data revealed several key features: (1) A northwest-dipping high-resistivity anomaly (R6, 50–150 km depth) beneath the Dabie Orogenic Belt (DOB) and the middle and lower reaches of the Yangtze River (MLYR), interpreted as a fragment of delaminated lithosphere from the Yangtze Block; (2) Crust-mantle scale conductive zones (C1-C5) associated with asthenospheric upwelling and partial melts; (3) The Yangxin-Changzhou Fault (YCF) represents a lithospheric boundary facilitating magma ascent. Integrated with regional geology, we propose that Yanshanian (145–120 Ma) strike-slip reactivation of the Tan-Lu Fault (TLF) and YCF, driven by Paleo-Pacific Plate subduction, triggered lithospheric delamination, magmatism, and large-scale mineralization. This tectonic reworking provided pathways for mineralizing fluids, ultimately controlling the spatiotemporal distribution of MLYB.