Lithospheric electrical structure of the northern Yidun Terrane (Sanjiang region, SW China) and its implications for mineralization

• We present a 3-D magnetotelluric resistivity model of the lithosphere beneath the northern Yidun Terrane (Sanjiang region, SW China). • Deep conductive zones imaged beneath the Jinshajiang and Ganzi–Litang sutures provide geophysical constraints on Paleo-Tethys subduction geometry. • Deep conductive anomalies image bidirectional subduction of the Jinshajiang Ocean and westward high-angle subduction of the Ganzi–Litang Ocean. • 4.Suture-related deep conductors likely reflect melt/fluids and may record an “inherited structure + Cenozoic reactivation” history, offering constraints on regional metallogenic processes and exploration targeting. The northern Yidun Terrane, located at the eastern margin of the Tibetan Plateau, is a key area for understanding the final closure of the Paleo-Tethys Ocean, deformation of the marginal lithosphere, and associated mineralization processes. We present a lithospheric resistivity model to a depth of 150 km, derived from a 480-km-long broadband and long-period magnetotelluric (MT) profile crossing the Qiangtang Terrane, Yidun Terrane, and Songpan-Ganzi Terrane. The results show that the upper crust is dominated by massive resistive bodies, while multiple high-conductivity anomalies are present in the mid–lower crust and crust–mantle transition zone. We infer that the high conductors beneath the Jinshajiang and Ganzi–Litang sutures may be related to partial melting of hydrous rocks, whereas the high conductor beneath the Songpan-Ganzi Terrane reflects a weak, low-viscosity flowing layer in the mid–lower crust of the eastern Tibetan Plateau margin. The geometry of the deep conductors beneath the sutures provides key evidence for the subduction polarity of the Paleo-Tethys Ocean, suggesting a combined pattern with bidirectional subduction along the Jinshajiang suture and westward high-angle subduction along the Ganzi–Litang suture. Considering the regional tectonic evolution and metallogenic history, we suggest that the deep conductors beneath the sutures have a composite nature characterized by “inherited conductive structures from ancient subduction” that were later reactivated by Cenozoic tectonic activity. These features record the Paleo-Tethyan subduction–arc magmatism while also bearing imprints of Cenozoic reworking. Furthermore, the deep conductors imaged beneath the major sutures and their upward connections are interpreted as a long-lived magma–fluid “source–pathway” system, which may have facilitated the ascent and focusing of ore-forming melts/fluids. This architecture provides new geophysical constraints for understanding regional metallogenic processes and for guiding exploration targeting.