Deep source region and material channels beneath a collision-related porphyry copper-polymetallic metallogenic belt, South Tibet: Insights from magnetotelluric data

The closure of the Neo-Tethys Ocean and subsequent continent-continent collision between the Indian and Eurasian plates have driven a complex series of subduction-collision orogenic events across Southern Tibet. As a consequence, the region hosts abundant arc-related polymetallic mineralization formed during the Mesozoic along with collision-related porphyry copper-polymetallic deposits generated in the Cenozoic. However, the deep-seated origin and evolution of metal-bearing materials and their transport from source region to surface across the whole lithosphere remain unclear. To address this, we present a new 3-D electrical resistivity model, derived from magnetotelluric (MT) data, to explore the crustal structure beneath the central segment of the collision-related metal belt in Southern Tibet. The model reveals a widespread low-resistivity zone at depths of 30–75 km, with a location corresponding to the front of the downgoing Indian Plate. This zone is interpreted to be a deep source region for metal-bearing fluids. Additionally, localized low-resistivity features in the upper crust connect with the inferred source region and closely align with the spatial distribution of surface porphyry copper-polymetallic deposits, likely representing pathways for the upward migration of fluids. Integrating with geochemical and geological constraints, the MT results support the hypothesis that a geodynamic event, such as the detachment of the lithospheric mantle from the Indian crust, generated the right conditions for the formation of the metal-enriched source region, therefore ultimately contributing to the development of the collision-related metallogenic belt.