Formation Mechanism And Coal Spatial Feature-control Of F₁6Thrust Fault In Yima Coalfield

As the north boundary fault of Yima coalfield, F16thrust fault is a large-scaleregional fracture. Study on the geological characteristics of the F16thrust fault, such asshape of fault plane, extended length, thrust distance, associated structures andcoal-control action, makes important sence to guarantee the security of undergroundmining and exploration of coal under the F16thrust fault.According to plate tectonic theory, this paper analyzes the F16thrust fault fromthree aspects: geometry shape characteristic、kinematics characteristic、and dynamicalcharacteristic, and studies the coal-control action of F16thrust fault, by applyingtraditional geological research method with anthracology experiments. Based on thestudy of regional structures, the five main conclusions are abtaine.(1) F16thrust fault, Jiashi thrust fault and Nanpingquan thrust fault compose alarge-scale regional thrust nappe system, which extend at least100km in the directionof EW. This huge thrust nappe system links up other similar thrust nappes inneighboring areas, extending eastward into the Huainan coal basin, Anhui, andwestward into the north of Weihe basin, Shangx.(2) The upper part of F16thrust faultsurface has a steep dip about70o, however, the lower part has a low-angle dip20o,which looks like a shovel. In the western Yima coalfield, structure of the fault surfaceis a simple, with a high-angle dip. However, in the opposite direction, fault surface’sdip angle decreases and the F16thrust fault has2or3piece of secondary fault surfacebeyond the main surface.(3) The study of joint analysis and the rock&coalmicrostructure shows that Yima area has undergoing the effect of tectonic stress fieldmore than once. The most important effect come from the SN compressionalmovement, which accompanies with strike-slip shear movement.(4) Under the controlof the evolution of east Qinling orogenic belt, F16thrust fault formed in the lateMesozoic, as the fronter zone of Jiashi-Nanpingquan thrust nappe. According topreliminary estimate, the thrust distance in the horizontal orientation of F16thrust faultis more than2.5km，and the fault amplitude is about1.2km.(5) The formation of F16thrust fault had created the drag fold in the south of Yima coalfield, leading the flowingdeformation of coal seam and anomalous change of the coal-seam thickness and spatialform.