| The Mohe basin is a unique basin in Hinggan Mountains basin group. It is different from the other basins in its extension, directions of structural lines and age of basin formation. The type of basin was governed by tectonic setting, but the evolution of the basin is often controlled by the structural evolution of basin basement. The analysis of structural characteristics and evolution of the Mohe basin will contribute to our better understanding of the structural characteristic of basins in Northeast China, dynamic mechanisms of basin formation, the genesis of late Mesozoic igneous rock in adjacent areas, and the tectonic process of lithosphere extension and thinning in East China.Based on synthetic field geological survey, analysis of geophysical data, and geochemical analysis, this paper discussed the relationship between tectonic and magmatic processes and basin evolution, moreover studies of regional geodynamic evolution. We found the Mohe basin is constituted by three parts, a pre-Mesozoic basement of metamorphic rocks, a group of late Jurassic terrestrial clastic sedimentary rocks and a sequence of early Cretaceous volcano-pyroclastic rocks.During late Jurassic, the main tectonic framework of Mohe basin trends EW,with structural characteristic that the north and south parts are higher than the middle part. Basement faults which trends E-W and some small scale faults trending N-E are formed during the period. They controlled late Jurassic sedimentation. Affected by clastic deposition which denuded from the orogenic belts at the northern side and basement at the southern, sedimentary rocks of the Eumr River group are deposited. They are of alluvial fans, braid river, fan delta, braid river delat and lacustrine facies. As a result, a foreland basin was developed in Mohe area. Later in this stage, thrust-nappe from north to south, which caused intense deformation and regional metamorphism of the sedimentary rocks, was formed in the western part of basin.During early Cretaceous,the tectonic framework of Mohe basin was changed into the graben- horst pattern trending NE-SW. Pre-existing faults trending NE was reactivated, and faults trending NNE was developed. They controlled distribution ofvolcanic rocks of early Cretaceous. During 129±17Ma and 117±3Ma, intermediate basic- intermediate to acidic lava, of Tamulangou formation, Shangkuli formation and subsequent Yiliekede formation, was formed. An angular unconformity was formed between lower Cretaceous and upper Jurassic, leading to the occurrence of the bi-mantles of the basin with a volcanic faultdepression.The Mohe basin is a superimposed basin formed by a late volcanic fault basin of Cretaceous superimposed on a foreland basin of late Jurassic. In late Jurassic, influenced by closing of Mongolian -Okhotsk ocean due to convergence of North China plate with Siberia plate, a SN compression affected the Mohe basin. The southern and northern margins of the basin were uplifted due to faulting in EW direction. This is foreland stage of the Mohe basin. During early Cretaceous, there is a significant change of orientation of regional stress field. Regional stress field changed from SN compression into NW-SE extension. Extensive uplifting of mantle, magma activity resulted in subsequent lithosphere thinning. Large scale fault depression was formed in this area and extensive volcanic rocks were erupted at the background of extensional setting from intracontinental to plate margin. The Mohe basin at this stage was evolving into a new stage of volcanic fault depression.
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