The giant Central Asian Orogenic Belt is an extensive accretionary orogen, of which the Solonker suture, as a major regional suture, coincides closely with an early Permian paleobiogeographical boundary. This suture is considered to mark the location of the final closure of the Paleo-Asian Ocean between the North China Craton and the Mongolian Terrane. Although the closure time of the Paleo-Asian Ocean along the Solonker suture has generally been regarded as Late Permian–Early Triassic, uncertainty remains because of a lack of typical collision-related features (e.g., high-grade regional metamorphism and well-developed fold–thrust structures) and a scarcity of outcrops.

The present study reports Early Permian foliated gabbros and dikes (288–275 Ma) and Middle-Late Permian undeformed layered gabbros, strongly peraluminous granites, and I-type granites (265–254 Ma) in the Xinhure area along the northern margin of the North China Craton. The Early Permian foliated intrusions have a subduction-related geochemical signature and were derived from partial melting of lithospheric mantle modified by subduction-related melts or fluids at the active margin of the North China Craton. In contrast, the Late Permian undeformed layered gabbros and strongly peraluminous granites were derived from partial melting of lithospheric mantle and middle–upper crust, respectively, triggered by asthenospheric upwelling. Therefore, a transition from an end-compressional to an extensional environment according to a transition from collision termination to post-collision of the North China Craton and Mongolian Terrane may have occurred between 275 Ma and 262 Ma. This time span can be considered as the final closure time of the Paleo-Asian Ocean along the Solonker suture.

巨大的中亚造山带是广泛的增生造山带，其中的Solonker缝合线作为主要的区域缝合线，与二叠纪早期的古生物地理边界非常吻合。该缝合线被认为是华北克拉通和蒙古地带之间古亚洲洋最终封闭的位置。尽管沿Solonker缝合线将古亚洲洋封闭的时间通常被认为是晚二叠世-早三叠世，但由于缺乏典型的与碰撞有关的特征（例如，高品位的区域变质作用和发达的褶皱），不确定性仍然存在–推力构造）和露头稀缺。

本研究报道了沿北缘新胡尔地区早二叠世的叶状辉长岩和堤防（288-275 Ma）和中晚期二叠纪的未变形层状辉长岩，强铝质花岗岩和I型花岗岩（265-254 Ma）。华北克拉通。早二叠世的叶状侵入体具有与俯冲有关的地球化学特征，并且是由华北克拉通活动边缘的俯冲有关的熔体或流体对岩石圈地幔的部分融化而产生的。相反，晚二叠纪未变形的层状辉长岩和强烈的高铝质花岗岩分别来自软流圈上升的岩石圈地幔和中上地壳的部分熔融。因此，根据华北克拉通和蒙古人地形从碰撞终止到碰撞后的过渡，从端部压缩到过渡的过渡可能发生在275 Ma至262 Ma之间。该时间跨度可视为沿Solonker缝线的古亚洲洋的最终封闭时间。