鄂尔多斯盆地东胜—神木地区侏罗系煤中常量元素地球化学特征

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

对鄂尔多斯盆地东胜—神木地区侏罗系直罗组和延安组的9个煤样进行了工业分析和元素分析以及煤灰常量元素测试分析,探讨了成煤环境条件对煤样性质的影响,并揭示了不同聚煤体系煤灰中常量元素的特征及其控制因素。分析测试结果显示,直罗组和延安组不同聚煤体系中煤的灰分产率、矿物含量和有机C含量呈现明显的变化趋势,从延安组Ⅱ、Ⅲ、Ⅳ单元→延安组Ⅴ单元→直罗组,煤矿物含量和灰分产率增加、有机C含量降低。此外,直罗组和延安组不同聚煤体系煤灰样的常量元素特征也具有明显的差异性和一定的变化规律,如:从延安组Ⅱ、Ⅲ、Ⅳ单元→延安组Ⅴ单元→直罗组,煤灰样中SiO2含量增加;延安组煤灰样K2O含量明显低于直罗组煤灰样K2O含量;此外,延安组Ⅱ、Ⅲ、Ⅳ单元煤灰样中TFe2O3含量远高于延安组Ⅴ单元和直罗组。综合研究认为,延安组Ⅱ、Ⅲ、Ⅳ单元、延安组Ⅴ单元和直罗组煤层煤的灰分产率、矿物含量和有机C含量的差异主要受控于成煤环境条件。成煤过程中所处的沼泽环境受河流所携带的碎屑物质影响的程度,影响着煤的矿物含量、灰分产率和有机C含量等特征。而延安组Ⅱ、Ⅲ、Ⅳ单元、延安组Ⅴ单元和直罗组不同聚煤体系的煤灰常量元素特征及其差异性,则主要受成煤环境条件(陆源碎屑矿物的量)、环境气候条件和有机质的量等因素的控制。

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 seam Ⅱ ,Ⅲ, Ⅳof Yah＇an Formationcoal seam V of Yan＇ an Formation→Zhilue 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 seam Ⅱ , Ⅲ, Ⅳ of Yan＇an Formation→coal seam V of Yan＇ an Formation→Zhiluo Formation, SiO2 contents of coal ash samples increase ; K20 contents in coal ash samples from Yan＇ an Formation are apparently less than those from Zhiluo Formation; besides, TFe2 O3c0n. tents of coal ash samples from coal seam Ⅱ , Ⅲ, Ⅳof Yan＇ an Formation are far more than those from coal seam Vof 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 seam Ⅱ , Ⅲ, Ⅳ of Yan＇ an Formation, coal seam V of 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 organ- ic carbon content of coals. However, the characteristics and diversities of coal ash major elements of different coal accumulating systems of coal seam II ,l]I, Ivof Yah＇ 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 enviromnental condition and organic matter content.