Subduction-Driven Reworking of Craton and Accretionary Orogen: Evidence From Integrated Geophysical Imaging in Western North China Craton

Abstract

Observations and interpreted mechanisms for the reworking of Precambrian cratons and accretionary orogens have significant relevance in understanding the history and evolution of continental lithosphere. Here we investigate the Precambrian basement and lithospheric architecture of the western North China craton (NCC) through the integration of multiple geophysical data sets, including density structure derived from 2D velocity-constrained gravity-focused inversion, along with newly-compiled aeromagnetic, magnetotelluric (MT) and shear-wave velocity data. We present five multi-geophysical sections illustrating the lithospheric structure along compiled MT profiles in western NCC. The mantle lithosphere of the central-western Alxa block and central–southern Ordos block is primarily characterized by high velocity, low-moderate density and high resistivity. This contrasts with the mantle lithosphere on or near the Inner Mongolia Suture Zone (IMSZ), where an apparent low resistivity zone with anomalous density marks the Paleoproterozoic suture between the Yinshan block and the Ordos block. Our results demonstrate the Alxa block's preservation of an Archean–Paleoproterozoic metamorphic basement, linking it as the westward extension of the Yinshan block and an integral part of the Precambrian NCC. We propose that the marked lithospheric geophysical anomalies of the IMSZ mainly resulted from subduction processes related to the Paleo-Asian and Paleo-Pacific oceans. Our findings suggest the Precambrian cratonic accretionary orogens are more vulnerable to modification than adjacent Archean nuclei during later tectonic events. Therefore, cratonic accretionary orogens may be important for processes of craton destruction, continental breakup and lithospheric healing.