The structure features and forming mechanism of Huaibei coalfield

Huaibei coalfield lies on the leading edge and outskirts of the Xusu arc thrust belt. The paper discussed the structural features, tectonic evolution and forming mechanism of the Huaibei coalfield based on the field geological survey and a synthesis of available data. The results show that:① Huaibei coalfield could be subdivided into the northern and the southern units along Subei fault. The northern unit is featured by thrust faults and Jurassic-type folds distributed as an arc belt protruding westward, of which tectonic lines are characterized by SN-NEE strikes. The southern unit has got tectonic lines that strike NNW and NNE, and dominated by normal faults and open short-axis folds. ② The secondary subdivision of the southern and northern structural units is in line with the faults developed along the leading edge of the nappe, and structural analyses have been conducted within these units. The northern unit is a part of the mainbody of the Xusu thrust. The hanging wall of the thrust comprises the Xiaoxian anticline and area to its east, while the footwall lies to the west of the anticline. As for the southern unit, the hanging wall in the east of Xisipo fault composes the southeastern end of the Xusu arc structure, while footwall lies to the west of the fault. ③ It could be clarified that Huaibei coalfield has experienced three major tectonic events since the deposition of coal-bearing strata during Carboniferous-Permian, namely S-N compression during Indo-China period which formed the E-W fractures, the early Yanshanian NWW-SEE compression that formed Xusu arc structure belt, and the late Yanshanian NNE-SSW compression that triggered the voluminous NNE-SSW normal faults within the coalfield.