| Yangquan coalfield is the largest anthracite production base in China,However,the structure of coalfield is relatively complicated,The gas outburst safety situation is relatively severe in the mine production,which restricts the safe and efficient production of coal mine in some extent.Based on the regional geological tectonic background and mine geological data,through the observation of typical field structures,combined with the microdeformation features of tectonites and tectonically deformed coal(TDC),this thesis deeply studies the regional tectonic evolution mechanism and its control mechanism for the mine structure in the Yangquan coalfield,and provide important support for mine gas outburst prediction and evaluation The following results are obtained.(1)The regional tectonic evolution,which has obvious control over the tectonic development in Yangquan coalfield,is mainly in the Indosinian,Yanshanian and Himalayan.The NWW-SEE tectonic compression in the early Yanshanian was the key period for establishing the structural pattern of Yangquan coalfield.In the Indosinian,near NS compressive stress formed a near EW fold and fracture structure in the north and south parts of the Qinshui Basin.The early Yanshanian was the key period to form a structural pattern in the study area.At this time,the area was affected by the NWW-SEE compressive stress,and NNE direction structures were formed in the middle part of North China.In the midYanshanian,there are distinct structural divisions on both sides of the Taihang Mountains.The east part of the Taihang Mountains is dominated by extension,while the compression stress is still dominant in the west of the Taihang Mountains.The Qinshui Basin located on the middle is slightly stretched.In the late Yanshanian,North China is in a weak squeeze deformation period,and the tectonic stress mechanism is dominated by NW-SE extrusion.In the Himalayan,NNE-SSW compression dominated the study area,and mainly reflected in the reconstruction of the early structure.(2)The Taihangshan fault on the eastern side of the Qinshui Basin is closely parallel to the Taihang Mountain uplift and has a controlling effect on the formation of the basin.The fault zones show obvious structural segmentation features along the strike.The intensity of the northern tectonic deformation is significantly stronger than that of the northern part.The northern part of the thrust nappe structure is relatively developed.It is mostly manifested by the thrust of the west plate to the east plate,resulting in folded folds in the rock near the fault zones.The Wutaishan uplift is located in the northern part of the study area and is characterized by the exposed Archean metamorphic rock,which controls the northern boundary of the coalfield.The south of the study area is Zhanshang-Wuxiang-Yangcheng NNE-trending fold belt,which forms the main part of the Qinshui Basin,and the exposed strata in the region are dominated by the Triassic.The analysis of the micro-deformation features of tectonites shows that the brittle deformation and plastic deformation in the study area are relatively developed.The form of brittle deformation is characterized by the interlaced development of shear fissures and tension fissures.The ductile deformation is dominated by double-crystal sliding.According to the width and shape of the calcite twins,it can be estimated that the temperature at which twins are formed is between 150?and 250°C.By counting calcite twinned particle percentage,calculated ?? is between 111 Mpa and 162 Mpa.This indicates that the stress-strain environment of formed structures is the shallow,medium-low temperature,high stress,and high strain rate deformation environment.(3)The folds in the Yangquan coalfield are relatively developed,and the deformation is relatively weak.According to the fold distribution direction and development scale,there are mainly three groups of folds,the folds of NNE-NE direction are the most developed,controlling the main shape of the mine,near EW folds followed,the NW folds is weakest.Through the curvature analysis,it is shown that the deformation of the coal seam in the coalfield is small,the average curvature reflects the deformation degree of the fold,and the Gaussian curvature could indicate saddle structure.The fault structure in the coalfield is characterized by the appearance of small faults.Both of the drop and extension distance are small.The faults in different coal seams are different.The normal fault in No.3 coal is more developed,the NE and NWfault are more developed,the number of reverse fault and normal fault in No.15 coal is basically equal.Its the trend is most developed with NNE.The development of TDC in Yangquan coalfield is mainly controlled by the secondary fold structure and its mutual superposition.It is partially affected by small faults.The TDC is mainly brittle and forms brittle deformation series TDC of different types,but wrinkle coal and mylonitic coal are also developed in someplace.(4)The structural development of the Yangquan coalfield has the deformation features,planar zoning and vertical divergence.The folds distributed in different directions in the coalfield are formed in different tectonic periods and are superimposed on each other to form the current tectonic combination form in the coalfield.Indosinian had a weak influence on the whole coalfield,and several folds that were near EW were formed mainly in the northern part of the coalfield.In the early Yanshanian,the NNE-NE folds are widely developed in coalfield,formed the main part of the coalfield structure.The Himalayan is mainly a superposition of the early formed structures and forms some NWW folds. |
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