| Qinshui Basin is located in the South-central North China Craton. It is a complex syncline striking NNE-SSW(Taihangshan in the east, Huoshan in the west, Qinling-Dabie orogenic belt in the sorth, and Yinshan orogenic belt in the north),which was mainly formed during the Mesozoic. The Main coal-bearing strata of the Qinshui Basin are Taiyuan Formation and Shanxi Formation of the Late Paleozoic. The Qinshui Basin is thought to has been mainly experienced three periods of tectonic deformation for the impact of tectonic regime transformation since the Mesozoic, when the basin formed. The three periods of tectonic deformation are Indosinian, Yanshanian, Himalayan.Based on the studies of folds, faults, joints developed in the study area, this paper focused on the study of characteristics of tectonic deformation and tectonic stress field for the parts of the basin, relationship between the cleats and joints, paleocurrent direction of the Late Paleozoic and the characteristics of tectonic deformation of southern section of Lishi Fault Belt. The main understanding are as follows:1. Eastern part of the Qinshui Basin, Taihangshan Fault Belt(TFB) is the eastern boundary of the Qinshui Basin. Based on the difference in composition of the strata of the two sides of the TFB, structural styles and deformation intensity along the striking, the TFB could be divided into four sections in general. The paper offered new geological evidences for the TFB to show the sinistral strike-slip in the Mesozoic. The weak zone in the basement play an important role for forming the TFB. Asthenosphere upwelling and the magmatic activity uplifted the TFB. The different uplift extent in the north and the south of the TFB caused the different performance in outcrops.Eastern part of the Qinshui Basin, joints systems developed very well and often developed two conjugate joint systems with better orientation. One set is striking NNE-SSE to N-S, the other set is striking NEE-SWW to NWW-SEE. Most of the dip angles of these joints are bigger than 75°. The maximum principal stress also could be divided into two sets, one set is striking NE-SW, the other set is striking NW-SE.2. Southern part of the Qinshui Basin, the effect of the regional extension stress field is very obvious. nearly E-W, NW-SE trending graben systems and triangular facets are the concrete manifestation of the regional extension.Southern part of the Qinshui Basin, joints systems developed very well but with various orientation. Besides the NE-SW trending joint system set, there are some other joint system sets, for example the NNW-SSE,NW-SE and NEE-SWW trending joint system sets. Most of the dip angles of these joints are bigger than 70°. The maximum principal stress are striking nearly W-E and NE-SW.3. Western part of the Qinshui Basin, the Huoshan piedmont fault and the Fushan fault and other striking nearly N-S composite the west boundary of the Qinshui Basin, these faults show activities in the Cenozoic.4. Northwest part of the Qinshui Basin, the Cenozoic structures developed very well, the extensional direction of the Cenozoic is 141°. Shovel normal faults controlling the Jinzhong graben basin have good performance both in the seismic sections and in the outcrops. There are a lot of NEE-SWW trending fractures and high-angle normal faults. The joints could be divided into two sets One set is striking NNW-SSE, the other set is striking NEE-SWW. The maximum principal stress are striking NE-SW, N-S and NW-SE.5. North end of the Qinshui Basin, the trends of the structure line in different area are diverse, in the west the structure lines are mainly NE-SW trending; in the east the structure lines are mainly NNW-SSE or NW-SE trending; in the central the structures lines are mainly almost E-W trending.The relationship between the faults and the dykes is quite clear. The timing of the NNW-SSE trending compression is ahead the Late Yanshanian confined by the dykes. The tectonic stress field control the drainage development. The maximum principal stress are striking NNW-SSE.6. Central part of the Qinshui Basin, NNE trending subordinate folds developed generally in small scale with gentle dip angles of the limbs of the folds. The joints systems developed very well and often developed two conjugate joint systems with better orientation. One set is striking NE-SW, the other set is striking NW-SE. The maximum principal stress also could be divided into two sets, one set is striking NNW-SSE to N-S, the other set is striking NNE-SSW.7. The Qinshui Basin is thought to has been mainly experienced three periods of structure activities in the Mesozoic and the Cenozoic:Indosinian, Yanshanian, Himalayan.Indosinian, the maximum principal stress is nearly N-S compression derived from the analysis result of the nearly W-E trending folds and the conjugate joint sets. The collision between the North China Plate and South China Plate provided the power producer.Yanshanian, the TFB and the other NNE-SSW trending structures formed during the period. The maximum principal stress is NW-SE compression. The paleo-Pacific Plate subducted under the Asian continent provided the power producer.Himalayan, the tectonic stress field is affected by the Indian plate and the Pacific plate. The maximum principal stress is NE-SW compression. The tectonic stress field changed radically compared to that of Yanshanian.8. The joints and cleats show consistency to some extent. The data of oblique bedding, cross-bedding in the Permian could reflect the ancient flow direction. In the Permian, meandering river developed very well, and the provenance was from the north and the south.9. The south section of the Lishi Fault Belt is the best outcrop observation area for the Lishi Fault Belt composed by the thrust fault and fault fracture zone. The quite steep faults striking nearly N-S with different dip. Tectonic breccia, structural lenticular body, fault gouge and cleavage zone developed in the fault fracture zone. It is a typical compressed fragmentized belt. In Shilou, fault related folds formed manifesting thrust from W to E. |
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