Mantle Magmatic Activity and Source Material Supply for the Jinchuan Cu–Ni Deposit in Northern China Revealed by Seismic Tomography

The Jinchuan Cu–Ni sulfide deposit, one of only two ultra-large magmatic Ni–Cu–PGE deposits in Eurasia, is hosted in a small ultramafic intrusion at the southwestern margin of the Alxa block, North China Craton, and contains over five million tonnes of nickel. Previous studies suggest that its formation is linked to large-scale deep magmatic processes, but direct evidence from the mantle source region has been limited. Using P-wave seismic tomography, we imaged the crust and mantle beneath the Qilian–Longshoushan area, revealing a deep low-velocity anomaly at ~400 km depth, interpreted as residual mantle plume material. This anomaly spatially corresponds to the Jinchuan deposit, representing a long-term material and heat supply pathway for ore formation. A high-velocity anomaly at ~200 km depth, likely related to Indian plate subduction, influenced the Cenozoic tectonic evolution of the Longshoushan region. These results integrate geophysical, geochemical, and geological evidence, highlighting how deep mantle dynamics and associated magmatic activity controlled the supply of material to the Jinchuan Cu–Ni deposit and contributed to its formation.