鄂尔多斯盆地中东部石炭系本溪组煤岩元素富集特征及成因

Element enrichment characteristics and genesis of coal rocks in Carboniferous Benxi Formation, central and eastern Ordos Basin

  • 摘要: 对鄂尔多斯盆地中东部石炭系本溪组障壁岛—沼泽沉积体系与潟湖—沼泽沉积体系煤岩的两口井10个煤样进行常量元素、微量元素和工业组分分析,探讨不同沉积体系下煤岩的元素富集特征与成因。研究结果表明:障壁岛—沼泽和潟湖—沼泽沉积体系中,煤岩的工业组分、常量元素和微量元素含量主要受成煤环境条件控制。两种沉积体系的元素主要受北部造山带物源的影响,同时也受海相沉积环境和岩浆活动的影响。障壁岛—沼泽沉积体系常量元素以Si、Al为主,与灰分有良好相关性,来源于北部造山带的多种黏土矿物;微量元素主要为无机成因,Li、Zr等元素与灰分、Si、Al等有显著相关性,表明其主要来源是陆源碎屑输入的硅铝酸盐;Sr元素来源于黏土矿物和火山岩物质,Cu、Cr元素为火山碎屑和海相磷灰石混合成因,Be、V、Cd元素则来自腐殖酸。潟湖—沼泽沉积体系中,常量元素同样以Si、Al为主,但Mg、Ca、Mn、P元素与灰分和Si、Al的相关性较差,来源于高等植物沉积埋藏;微量元素主要为无机成因,Li、Sr元素分别来源于物源输入和海相沉积有机质矿物;Be、Ga等元素为无机成因,来源于陆源碎屑物质中的长石、石英和黏土矿物;Cu、Sr、等主要来源于海相黄铁矿、磷灰石等矿物或海水作用下成岩过程中富集。

     

    Abstract: Ten coal samples from two wells in the barrier island-swamp and lagoon-swamp depositional systems of the Carboniferous Benxi Formation in the central and eastern Ordos Basin were analyzed for major elements, trace elements, and industrial components to investigate the elemental enrichment characteristics and genesis of coal rocks under different depositional systems. The results indicated that in both depositional systems, the industrial components and the contents of major and trace elements in coal rocks are primarily controlled by the coal-forming environmental conditions. The elemental compositions are mainly influenced by provenance from the northern orogenic belt, marine depositional environments, and magmatic activities. In the barrier island-swamp depositional system, the major elements are dominated by Si and Al, which show strong correlations with ash content and originate from various clay minerals derived from the northern orogenic belt. The trace elements are mainly of inorganic origin. Elements such as Li and Zr show significant correlations with ash content, Si, and Al, indicating that they are primarily derived from terrigenous debris inputs of aluminosilicates. Sr is derived from clay minerals and volcanic rocks. Cu and Cr have mixed origins from volcanic debris and marine apatite. Be, V, and Cd originate from humic acids. In the lagoon-swamp depositional system, the major elements are also dominated by Si and Al. However, Mg, Ca, Mn, and P show weak correlations with ash content, Si, and Al, indicating that these elements are derived from the deposition and burial of higher plants. The trace elements are primarily of inorganic origin. Li and Sr originate from provenance inputs and organic minerals in marine sediments, respectively. Be, Ga, and related elements are of inorganic origin and are sourced from terrigenous debris such as feldspar, quartz, and clay minerals. Cu, Sr, and related elements are primarily derived from marine pyrite, apatite, and other minerals, or are enriched during diagenetic processes under the influence of seawater.

     

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