The Paleo-Asian Ocean eventually closed along the Solonker Suture Zone during the Late Permian and Early Triassic, before the collision between the Siberian Craton and the North China Craton (NCC) formed the eastern Central Asian Orogenic Belt (CAOB). In this paper, Magnetotelluric (MT) profile data across the south-eastern CAOB and the northern margin of the NCC are explored to image the two-dimensional resistivity structure of the region. According to the resistivity model, a north-dipping conductive layer to the north of the Xilinhot fault and a south-dipping conductive layer to the south of the Linxi fault are revealed. The two conductors are interpreted as evidence of the late-stage low-angle bidirectional subduction of the Paleo-Asian Ocean, which constrains the northern and southern deep boundaries of the Solonker Suture Zone. Another couple of mantle conductors with opposite dipping angles are revealed under the Solonker Suture Zone and Bainaimiao Belt, which are interpreted as evidence of the early-stage high-angle bidirectional subduction of the Paleo-Asian Ocean. Compared with the results from previously reported MT profiles in this area, the subduction angle becomes more gentle from west to east. The difference of convergence rate between the NCC and the Siberian Craton is considered to be the major cause of the closure difference along the strike. The northern margin of the NCC has a conductive lower crust, which may result from the magma underplating or crust-mantle decoupling, as it is imaged to be connected with the south-dipping conductive layer beneath the Solonker Suture Zone.

中文翻译：

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中亚造山带东南部岩石圈传导结构对古亚洲洋闭合过程和模式的制约

在晚二叠世和早三叠世期间，古亚洲洋最终沿着索伦克缝合带闭合，然后西伯利亚克拉通和华北克拉通（NCC）碰撞形成中亚东部造山带（CAOB）。本文探索了中亚造山带东南部和华北克拉通北缘的大地电磁（MT）剖面数据，以对该地区的二维电阻率结构进行成像。根据电阻率模型，揭示了锡林浩特断裂带以北的北倾导电层和林西断裂带以南的南倾导电层。这两个导体被解释为古亚洲洋晚期低角度双向俯冲的证据，该俯冲限制了索伦克缝合带的北部和南部深部边界。在索伦克缝合带和白乃庙带下还发现了一对相反倾角的地幔导体，这被解释为古亚洲洋早期高角度双向俯冲的证据。与之前报道的该地区大地电磁剖面结果相比，俯冲角度自西向东变得更加平缓。华北克拉通与西伯利亚克拉通收敛速度的差异被认为是沿走向闭合差异的主要原因。华北克拉通北缘有一个导电的下地壳，这可能是由于岩浆底侵或壳幔解耦造成的，因为它被成像与索伦克缝合带下方的南倾导电层相连。