Variety regularity of metamorphic coal of Longdong coalfield in Xingtai by X-ray diffraction method

In this paper,the character of basic structural unit and spatial-temporal variety regularity of metamorphic coals are studied through X-ray diffraction(XRD) analysis.In the vertical direction,as the burial depth increases,the d₀₀₂ values decrease,whereas L_c and L_a values increase.In the level direction,d₀₀₂ values are low when the coal seams are near the magma intrusion.On the contrary,these values are large when the coal seams are far away from the magma intrusion.Affected by magmatic heat sources,distribution of coal sorts assumes the old town as the center and takes the banding distribution outward.In the coalfield,it is found that the anthracite distributes nearby the old town and the coal sorts are lean coal,coking coal,fatty coal and gas coal outward.Coal metamorphism is mainly affected by regional metamorphism,also affected by telemagmatic metamorphism.