Major Element Geochemistry of Jurassic Coal in DongshengShenmu Area, Ordos Basin

Key words: 
• coal /
• major elements /
• Jurassic /
• Ordos Basin

Abstract: Nine coal samples of Jurassic Zhiluo and Yan'an Formation, collected from DongshengShenmu area of Ordos Basin, have been analysed for their proximates, ultimates and major elements. In order to discuss the influence of coalforming environmental conditions on coal properties, and study the characteristics and its control factors of major elements in coal ash of different coal accumulating systems. Ash production, mineral and organic carbon content of coal samples from different coal accumulating systems of Zhiluo and Yan'an Formation show obvious change trend. From coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation→coal seamⅤof Yan’an Formation→Zhiluo Formation, mineral content and ash production increase, organic carbon content decreases. In addition, major element contents of coal ash also have clear diversities and certain variation rules. For example, from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation →coal seamⅤof Yan’an Formation → Zhiluo Formation, SiO2 contents of coal ash samples increase; K2O contents in coal ash samples from Yan’an Formation are apparently less than those from Zhiluo Formation; besides, TFe2O3 contents of coal ash samples from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation are far more than those from coal seamⅤof Yan’an Formation and Zhiluo Formation. Based on synthetic analysis, the authors hold that the diversities of ash production, mineral content and organic carbon content of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation, are mainly controlled by coalforming environmental conditions. The degree of influence on coal by detrital material during coal forming process affects mineral content, ash production and organic carbon content of coals. However, the characteristics and diversities of coal ash major elements of different coal accumulating systems of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation are mainly controlled by the factors of coalforming environmental condition (the content of terrigenous clasts), climatic environmental condition and organic matter content.