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It is well-known that the crust of central Asian areas was amalgamated during the Paleozoic and reworked in the Cenozoic. However, tectonic framework and evolution of the areas during the Paleozoic, including that the basement of Junggar basin is the trapped ocean or sinking continent, that subduction of oceanic lithospheric plate represented by Kalamaili ophiolites took place only along the northward margin of the ocean or simultaneously in its southern and northern sides, and etc, have been hot-debated issues. In the other hand, the crust of Tianshan and Junggar areas are underlaid by Paleozoic oceanic remains and continental marginal complexes, but why their present physiognomy are evidently different? Geological data from our field investigations and in-door researches last more than 20 years reveal that Paleozoic strata in the northeast margin of Junggar basin consist mainly of continent-derived clastic sedimentary rocks and are deformationally and tectonically characteristic of foreland thrust-fold belt. Seismic surveys from southern Altay mountains, through East Junggar ranges, Junggar basin and Tianshan mountains, to northern Tarim basin implemented in recent years discovered that Moho under the Tianshan mountains is cut off and overlapped, but kept relatively continuously under the Junggar basin and Esat Junggar ranges, that a weaker reflect area occurs in the lithosphere of Junggar basin evidently contrasted to stronger reflect features in its southern and northern areas, that only northwards dipping faults are distinguished from the deep lithosphere of Junggar basin and East Junggar ranges, and that a very strong reflector with northwards moderate dipping is lying in 100km to 150km deep lithosphere of the northern East Junggar. These geological and seismic data make us to get following conclusions that the Paleozoic basement of Junggar basin is sinking continental crust which is possibly underwent re-melting processes, that closure of ancient ocean represented by Kalamaili ophiolites followed the northward subduction of its oceanic lithosphere plate, and that geomorphological difference between the Tianshan mountains and Junggar areas is originated from Moho deformation. This research is financially supported by the National Key Basic Research Program of China (grant No. 2007CB411306, 2001CB409810), Surveying and Investigating Project of Land and Resources of China (grant No. 1212010611806, 1212010711817) and National Scientific Foundation of China (grant No. 40672138).
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