Geoelectric structure of the collision zone between the Siberia plate and the North China Craton and discussion on the deep suture boundary

The collision between the Siberia plate and the North China Craton led to the closure of the ancient Asian Ocean and the formation of a vast central Asian orogenic belt, which recorded abundant plate collision information and evidences that the deep suture boundary is of great significance to the study on the deep dynamic process from oceanic-continent subduction to continent-continent collision. To further address this issue, this paper presents an inversion of MT data along the 410 km-long Chagan Obo-Huade profile, thus to delineate a two-dimensional electrical structure beneath it. It provides evidence for the study of the deep structure and collision boundary between the Siberian plate and the North China Craton collision zone. Combining with seismic reflection and geological data we can obtain the following conclusions:(1) There are many groups of "U"-shaped low-resistance anomalies in the crust of the Siberian plate and the North China Craton collision zone which are correspond to arc-like and "crocodile mouth"-shaped reflection interfaces. Two dislocations on the Moho surface can be recognized, consistent with the deep electrical gradients. In addition to the low-resistivity blocks beneath the Bainaimiao island arc, the lithosphere of high-resistivity. These physical characteristics reflect the structural traces formed by the north-south convergence. (2) The collision zone can be divided into two different converging systems:Erenhot-Hegenshan and Soren-Xilamulun. The Erenhot-Hegenshan convergence system which formed in the Late Devonian-Late Carboniferous is composed of the renhot-Hegenshan accretion complex belt,Baolidao Island arc geological body and fault zone,of which the deep suture boundary is located in Erenhot.And the Late Permian-Early Triassic Soren-Xilamulun convergence system consists of the Erdaojingzi accretional complex belt and the Wenduermiao accretion complex belt and the fault zone,of which the deep suture boundary is located in Sonid Zuoqi. (3) There are high resistivity anomalies in asthenosphere beneath the Xilinhaote area, which may be the fragments of subducted oceanic crust or detachment lithosphere after collision orogeny.