Metallogenic model of the Hongqiling Cu-Ni sulfide intrusions, Central Asian Orogenic Belt: Insight from long-period magnetotellurics

The Hongqiling magmatic Cu-Ni sulfide deposit is one of the most important deposits in the easternmost segment of the Central Asian Metallogenic Belt, northeast China. However, the existence or non-existence of magmatic chambers is still not been determined, which is the key to decipher the formation of Hongqiling Cu-Ni deposit. Therefore, this study proposes to adopt long-period magnetotellurics method to image the deep-seated metallogenic system in Hongqiling Cu-Ni deposit. Two-dimensional (2D) nonlinear conjugate gradient inversion technology allows us to describe entire magma plumbing system, including the mantle-derived magma channels (banded low-resistivity anomalies), deep separated chamber (low-resistivity anomaly C2), and shallow magma conduits (low-resistivity anomaly C1). These results indicated that the mantle-derived primitive magma gave rise to the parental magma for the mafic-ultramafic intrusions in Hongqiling Cu-Ni deposit and triggered the segregation of Cu-Ni sulfides in the shallow chamber. By combining the experimental simulation, geochemistry, geochronology, and geotectonics data in the study area, we suggest that the partial melting processes which produced the large magma plumbing system probably have been triggered by lithospheric delamination.