石煤中伴生多种元素，开发利用潜力巨大。微量元素赋存特征研究是解决石煤中有益元素提取和有害元素环境污染的关键。本文运用煤地质学、矿物学、元素地球化学、统计学等理论，对湘东北地区下寒武统牛蹄塘组石煤的煤质特征、矿物组成、元素赋存状态及富集机理进行了研究。研究成果对揭示石煤中微量元素富集机理、促进有益元素开发、减轻有害元素危害具有重要意义。

根据工业分析、反射率、硫分等指标，阐明了石煤煤质特征。石煤为腐泥无烟煤阶段，呈高灰、低碳特征。全硫含量变化大，以硫化铁为主，菌藻类有机质次之。利用X射线衍射仪和带能谱的扫描电镜，分析了石煤矿物组成和形态特征，阐述了矿物地质成因。石煤矿物种类丰富，矿物组成和形态特征表明矿物主要为陆源碎屑输入和自生成因，硫化物矿物形态显示石煤沉积时受海水影响较强烈。

借助X射线荧光光谱仪和电感耦合等离子体质谱仪，测定了石煤中常量、微量元素含量，评价了石煤元素含量水平，总结了石煤中典型富集元素的富集特征。石煤中常量元素含量之和远高于中国煤中均值，常量元素含量特征表明石煤物质来源复杂、元素赋存状态多样。石煤中微量元素富集明显（1782~21977 μg/g），相比上地壳均值，普遍高度富集V、Mo、Cd、Sb和As，富集系数分别达到了38、130、414、153和75；明显亏损Sc、Ga、Zr、Sn、Hf、Ta和轻稀土元素（LREE）。

综合分析五步提取实验、逐步浸取实验、数理统计分析和扫描电镜测试结果，揭示了石煤中典型富集元素的赋存状态特征，建立了微量元素之间及其与矿物的共生关系。V主要以吸附和交代形式赋存于伊利石、云母和石英中，通常与Cu、Cd、Zn紧密共生，还发现了一种依附于有机质碎片的含钒物相。Mo通常与Ba结合紧密，以石英、磷钡铝石为主要赋存载体，个别存在高含量离子交换态的Mo。Cd赋存状态特征差别较大，具有含量高时以有机结合态为主，含量低时以无机结合态为主的特点。Sb主要赋存于有机质中，与Mo存在一定的共生关系。As在有机质、石英、碳酸盐矿物中均有赋存。

根据石煤元素地球化学指标、矿物和微量元素的赋存特征，分析认为石煤中微量元素的富集主要受沉积源区碎屑输入、多期次海水作用、热水影响和生物作用四个因素控制。划分了不同主控因素下石煤富集的微量元素类型，沉积源区碎屑输入使石煤富集了元素Si、Al、Ni、Cu、Zn、Cd、Y，多期次海水作用富集了元素S、K、B、U，热水影响富集了元素Si、Ba、Co、Ni、U、V、Mo、Cd、Sb、As，生物作用富集了元素Zn、Mo、V、Cr、Cu、Ni、Cd、Sb。

从元素地球化学角度确定了江南造山带东南缘发育的中—酸性岩浆岩和砂岩为湘东北地区早寒武世石煤的沉积物源区，揭示了石煤中微量元素的富集机理。江南造山带发生的多期次构造活动导致了海水影响下的元素在石煤层中出现了阶段性响应变化。海底热水喷发为周围水体提供了热能、大量微量元素和营养物质。营养物质使生物更加繁盛，菌藻类活体和残骸在缺氧条件下，通过生物化学作用捕获或络合水中元素，使游离元素在生物体内初步富集，有机体残骸与陆源碎屑混合后，经煤化作用形成石煤。

The stone coal containing some elements, has great potential for development. The modes of occurrence of trace elements play a key role in the extraction of valuable elements and prevention of harmful elements. The coal quality, mineral characteristics, modes of occurrence of elements, and enrichment mechanism of the lower Cambrian Niutitang formation stone coal in northeastern Hunan are studied using theories of coal geology, mineralogy, geochemistry and statistics. The results are of great significance to reveal the enrichment process of trace elements, promote the development of valuable elements and alleviate the damage of harmful elements in stone coal.

Based on the proximate analysis, reflectivity, sulfur content, the characteristics of stone coal quality are summarized. The stone coal is classified as saprolite anthracite with high ash and low carbon. The total sulfur contents of stone coal vary greatly, while the sulphate sulfur is the dominant form, followed by the bacteria and algae organic sulfur. Using XRD and SEM with energy spectrum, the composition and morphological characteristics of the mineral in stone coal are analyzed, and the geologic origin of the mineral is explained. Different types of minerals exist in the stone coal. The mineralogical composition and distribution indicate that minerals are mainly formed from terrigenous clastic material and authigenic precipitation. The sulfide minerals show that the stone coal is strongly affected by seawater.

With the help of XRF and ICP-MS, the content of major and trace elements in stone coal is determined, the level of element content in stone coal is evaluated, and the characteristics of typical enriched elements in stone coal are summarized. The sum of the major elements in the stone coal is much higher than the average value of Chinese coal. The characteristics of the major elements indicate that the sources of the stone coal are complex and the modes of occurrence of are diverse. Trace elements are enriched significantly (1782~21977 μg/g). Compared with the average value of upper continental crust, V, Mo, Cd, Sb and As are highly enriched, with the concentration coefficients being 38, 130, 414, 153 and 75, respectively. However, Sc, Ga, Zr, Sn, Hf, Ta and LREE are depleted.

Comprehensive analysis of five-step extraction experiment, gradual immersion experiment, mathematical statistical analysis and SEM test results. The occurrence state characteristics of typical enriched elements in stone coal are revealed. The relationship between the trace elements and their symbiosis with the minerals are established. Vanadium mainly occurs in illite, mica and quartz, coexisting closely with Cu, Cd, and Zn. A phase of vanadium attached to the organic debris is confirmed. Molybdenum is usually associated with Ba, with quartz and gorcexite as the main carrier. If the content of Cd is high or low, the dominant form is the organic matter or inorganic matter. Antimony coexisting with Mo, mainly occurs in organic matter. Arsenic distributes in organic matter, quartz, and carbonate minerals.

According to the geochemical indicators of stone coal elements, the occurrence characteristics of mineral and trace elements, the analysis believes that the enrichment of trace elements in stone coal are mainly controlled by the debris input of the sediment source area, multiple seawater effects, hot water influence and biological action. The types of trace elements enriched under different main control factors are divided. The input of debris from the sediment source makes enrichment of Si, Al, Ni, Cu, Zn, Cd and Y. The enrichment of S, K, B, U are caused by the seawater intrusion. The effect of hot water makes Si, Ba, Ni, U, V, and Mo enriched. Biological action makes enrichment of Zn, Mo, V, Cr, Cu, Ni, Cd, and Sb.

The medium-acid magma and sandstone developed in the southeast edge of the Jiangnan orogenic belt are identified as the stone coal sediment source area. The mechanism of the enrichment of stone coal trace elements in the early Cambrian in northeast Hunan is revealed from the perspective of elemental geochemistry. The multi-phase tectonic activities in the Jiangnan orogenic belt have caused the elements under the influence of seawater to appear in the stone coal seams in stages. The submarine hot water provide heat energy, trace elements and nutrients to the surrounding water body. The nutrients make organisms more prosperous. Under hypoxic conditions, living bacteria and algae and debris can capture or complex elements through biochemical action. The free elements are initially enriched in organisms, the organism debris and terrestrial debris mixed, then stone coal is formed.