Occurrence characteristics and formation mechanism of coal-bearing kaolinite rocks in Datong coalfield

The kaolinite rocks, a resource of industrial value, are abundant in the coal-bearing strata of the Datong coalfield.To look into the occurrence characteristics and formation mechanism of coal-bearing kaolinites, this paper uses the kaolinite deposits in the Taiyuan formation of the Late Paleozoic in the study area as the research object.The occurrence horizon, structural composition, rock type and genesis analysis of the kaolinite deposit were studied through field geological survey, microscopic identification, XRD analysis and geochemical analysis.Results show that the kaolinite rock in Datong coalfield is mainly located in five layers, including the No.9 coal floor, the No.8 coal floor, the No.3 and 5 coal floor, No.3 and 5 coal parting and the No.2 coal floor to No.3 coal roof.The kaolinite is the predominant mineral(the content is between 60 % and 90 %)associated with minor minerals like quartz, feldspar, mica, anatase, siderite and diaspore.The micro-components of the kaolinite rock in the study area were divided into grains, kaolinite crystals, mineral clasts and matrix.In addition, the kaolinite rock in the study area were categorized as grain kaolinite rock, cryptocrystalline kaolinite rock, lump kaolinite rock and sandy kaolinite rock according to the present morphology analysis.In conclusion, the genesis of kaolinite rock is mainly terrigenous transport sedimentary and volcanic ash.