Coal Facies Characteristics and Coal Formation Mechanism of No. 38 Coal Seam in Cuipingshan Coal Mine

Abstract

No. 38 coal seam is the main coal seam in Cuipingshan Coal Mine. In order to reveal its coal-forming mechanism, the microlithologic types of No. 38 coal seam in Cuipingshan Coal Mine are analyzed by using modern testing methods such as sequence stratigraphy, coal petrology and geochemistry. We find that the maceral of No. 38 coal seam is mainly vitrinite, the average content is respectively 57.28%, the vitrinite is mainly telinite and desmocollinite, and the microlithotypes is semi-bright coal. The coal facies of the No. 38 coal seam include tidal flat-tidal channel wet forest swamp facies, shoreland lacustrine wet forest swamp facies and barrier island-lagoon low swamp facies. The formation background of coal seam is an environment of shoreland lacustrine facies, barrier island~lagoonfacies and tidal flat-tidal channel swamp facies, etc., which are sea-land transitional facies. The shoreland lacustrine wet forest swamp facies and barrier island-lagoon low swamp facies are the main coal facies types of the No. 38 coal facies in the region of interest and are distributed throughout the whole coal seam section. This indicates that it always predominated in the evolutionary process of swamp. The tidal flat-tidal channel wet forest swamp facies also accounted for a certain proportion in the formation process of coal seam, and constitutes periodic cycle structure with the shoreland lacustrine wet forest swamp facies and barrier island-lagoon low swamp facies. Generally the coal formation mechanism of No. 38 coal seam is a regressive swamp development process, and its coal formation environment is tidal flat-tidal channel swamp and shoreland lacustrine swamp. Besides, the development process of peat swamp is influenced by the frequent advance and retreat of secondary seawater.