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Xiong X.,Chinese Academy of Geological Sciences | Gao R.,Chinese Academy of Geological Sciences | Li Y.,Geological Information Center | Hou H.,Chinese Academy of Geological Sciences | And 5 more authors.
Journal of Asian Earth Sciences | Year: 2015

The Great Xing'an Range is characterized by a complex crustal history involving the successive development of several Paleozoic to Mesozoic tectonic domains. A set of new different geophysical data, including deep seismic reflection profile, seismic refraction/wide-angle reflection profile, and magnetotelluric survey, were conducted recently to establish the lithosphere structure and geodynamic framework of the Great Xing'an Range and adjacent basins. Results based on the interpretation of the integrated geophysical data include the discovery of the "crocodile" style assembly fabric of the Songnen and Xing'an blocks; the intrusion of the Great Xing'an Range continental crust into the Songnen block while the mantle lithosphere of the Songnen block beneath the Xing'an block. The Great Xing'an Range experienced the delamination and the underplating, which is very common in the eastern part of Central Asian Orogenic Belt. The building of the Great Xing'an Range could divide into two phases: (a) the crustal shortening and overlapping resulted from the compression between the Songnen and Xing'an blocks in late Devonian to early Carboniferous; (b) the vertical building by the upwelling and underplating of the magmas in Mesozoic and Cenozoic. © 2015 Elsevier Ltd. Source

Li Y.-K.,Geological Information Center | Gao R.,Chinese Academy of Geological Sciences | Yao Y.-T.,Geological Information Center | Mi S.-X.,Geological Information Center | And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

Deep Seismic Sounding profile from Zhangjiakou to China-Mongolia border is about 600 km long, it goes across North China Plate, Xingganling-Mongolian orogenic belt and the Siberian plate. The recording of seismic waves from 8 explosions was conducted of 300 recorders along seismic line. The P-wave field provided good quality data for most of the profile. The authors processed, analyzed, and modeled the data which was collected during the wide-angle reflection and refraction effort. There are six phases, arrivals of refracted and reflected waves from sediments and basement (Pg), the reflected wave form the bottom of upper crust (P2), in middle crust (P3), the bottom of middle crust (P4), in the lower crust (P5, only appears in the beneath Xianghuang-Sunite) and Moho (Pm). Crustal velocity structure was obtained by seismic dynamics ray method (seis88). The results show that, (1) In the upper crust where is in area between North China Plate and Mongolia orogenic belt and in area between Mongolia orogenic belt and the Siberian plate, there are obvious high-velocity partial variations, and a lot of Paleozoic granite and ultramafic rock are exposed in the ground surface. (2) The velocities which is 6.3~6.7 km/s in the lower crust of southern margin of the North China Plate is higher than the velocities which is 6.1~6.7 km/s in the lower crust of the northern margin of the Siberian Plate, and the interface of the southern margin of the North China Plate is more gently than the northern margin of the Siberian Plate. The reason is that, in Inner Mongolia orogenic belt, the violent undulation interface of middle and lower crust may be caused by the crustal shortening and orogenic uplift, the flatten and material exchange in different blocks of land and sea result in the different regions of the velocity heterogeneity. Moho is more gently in the south of F2 fault and in the north of F4 fault, which is 40~42 km. There are double Moho boundaries between F2 and F4 fault, the No. 1 Moho uplifts obviously, the depth is 33.5 km and velocities is 6.6 to 6.7 km/s. The No. 2 Moho lies low obviously, the deepest area reaches 47 km in the beneath of F3 fault and the velocity is 6.8 to 6.9 km/s, which was caused by the crust-mantle mixed substance. Based on the characteristics of the Moho, the authors consider that the south area of double Moho boundaries is the northern margin of the North China Plate, and the north area of double Moho boundaries is the southern margin of the Siberian plate, the split position of the North China Plate and Siberian plate is between F2 and F4 fault. Source

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