Research On Physical And Chemical Structure Of Coal And Characteristics Of Gas Occurrence In Contact Metamorphic Zone

Pingdingshan coalfield is mainly Carboniferous-Permian coal measures. LateYanshanian tectonic activity is strong in this area. Acidic magma intrudes coalbed alongthe weak structural zone resulting in coal metamorphism and the variation of gasemission. Based on the investigation of regional geology, evolution of coal measuresand gas emission, combining with collecting coal samples near the agama body, byusing optical microscope, scanning electron microscope and X-ray diffraction, theinfluence of magmatic thermal on the coal is analyzed, the microstructure and themetamorphic degree of coal are investigated, the gas emission derived from laneway iscompared, and the conclusions are as follows:1. On basis of scanning electron microscopic analysis, the results show that thecoal influenced by the heat and overburden pressure from tense magmatic intrusion hasthe characteristics of tense deformation, abundant visible pores and fractures, which isbeneficial to connection of fractures and pores. The mid-macro pores are predominantin the coal. The degree of pore development decreases gradually apart from magmabody. The coal uninfluenced by the heat has characteristics of original texture with thepores derived from regional metamorphism and the fractures resulted from tectonicmovement. The small-micro pores are well developed in the coal.2. Results of XRD analysis indicate the crystal structure of the coal affected by theheat and overburden pressure has a regular variation within30~40meters apart from themagma body. From the beginning of the magma body, the elongation level (La) and thestack height (Lc) of aromatic nucleus in the coal prominently decrease with the distanceincreasing from the magma body; meanwhile, lamellae spacing of d002elevatesobviously.3. According to analyzing gas emission derived from the transport and ventilationlaneways of13021Coalface, amount of the gas emission has an increasing andfluctuating tendency with the laneways promoting towards the magma body because ofhigh gas content and pressure as well as improving permeability of the coal.