Coal, being one of the major energy sources for power generation, contains several critical trace elements. There is a growing scarcity and expense of these critical elements as a result of the increased demand and limitation of mining sources. To explore the geochemical characteristics of the rare-metal, rare-dispersed (scattered), and rare-earth elements (TREs) in coal, 25 coal seam samples of the Shanxi Formation in the Huainan coalfield were collected. The major element oxides, minerals, and TREs were analyzed by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the coal of the Shanxi Formation had ultra-low moisture and low ash yield and was medium–high-volatility with low sulfur content and high calorific value. Concerning minerals, the coal was mainly composed of kaolinite, illite, quartz, calcite, dolomite, and pyrite. Compared with Chinese coal and world hard coal, rare-metal element Li and rare-dispersed element Se were enriched, whereas Ga and Ta were only slightly enriched. The average content of REYs was 51.34 μg/g, which is lower than the average content of REYs in Chinese coal. It has the enrichment characteristics of light REYs. In the vertical direction, the content of most TREs was higher in the roof and floor of the coal seam and the parting, indicating that the sedimentary microenvironment plays an important role in controlling the migration and enrichment of elements. The experimental results of sequential chemical extraction and correlation analysis showed that the TREs in the Shanxi Formation coal mainly exist in a residual and carbonate bound state, and occur in clay minerals and carbonate minerals. The enrichment of Se may be due to its high organic form ratio. The C-value, B content, w(Sr)/w(Ba), and REY geochemical parameters indicated that the Shanxi Formation Coal seam was developed in a transitional, semi-saline, deltaic sedimentary environment. With their development affected by seawater, REYs in coal are greatly supplied by terrigenous clastics. The complex sedimentary environment is an important reason for the varying occurrence states of TREs in the Shanxi Formation coals.

为探究含煤地层沉积过程古泥炭沼泽的发育情况,以淮南煤田张集矿山西组1煤层为研究对象,刻槽采集样品,测试了样品的煤质参数、显微组分组成、部分微量元素含量,采用凝胶化指数、结构保存指数等参数,综合Sr/Ba、Cu/Zn等地球化学指标,讨论了张集矿山西组1煤层的煤质特征、煤相及其演化模式.结果表明:(1)张集矿山西组1煤具特低全水分、低灰、中高挥发分、特低硫、中高发热量的特点,为1/3焦煤,镜质组为主要显微组分,平均达到64.5％;(2)山西组1煤层煤相主要表现为低位沼泽相(A)和湿地草本沼泽相(B),同时表现出潮湿森林沼泽相(C)和干燥森林沼泽相(D)的煤相类型,在剖面上山西组1煤层煤相的演化可划分为B→A→B,A→D,A→C的三个阶段,从第一阶段至第三阶段成煤沼泽由三角洲间海岸的湿地草本沼泽相转变为下三角洲平原的潮湿森林沼泽相,指示了由海向陆的转化进程;(3)山西组1煤层泥炭沼泽发育过程中受到海水影响,整体海退背景包含一系列次级的海进和海退事件.

以淮南煤田深部山西组煤为研究对象,分别采集研究区张集煤矿和新集二矿二叠系山西组1煤层的煤样品,测试了样品中总汞的含量,分析汞的空间分布特征,采用浮沉实验、逐级化学提取实验以及相关性分析研究了煤中汞的赋存状态,并结合沉积环境探讨了深部山西组煤中汞的富集成因.结果 表明:(1)研究区煤样中汞含量介于0.03～0.93 μg/g之间,算术平均值为0.21 μg/g,均高于中国和世界煤中汞的背景值,与地壳中汞含量相比,富集系数高达2.6,表现出明显富集;(2)淮南煤田不同煤矿山西组煤中汞含量不同,张集煤矿煤中汞算术平均值为0.35 μg/g,新集二矿煤中汞算术平均值为0.12 μg/g;受复杂沉积环境和沉积相作用,同一煤层中,汞含量分布差异性较大;(3)相关性分析、浮沉实验和逐级化学提取实验结果表明,煤中的汞主要以硫化物结合态存在;矿物分析结果显示,黄铁矿是煤中汞的主要载体,张集煤矿煤中的汞主要以固溶态赋存于原生黄铁矿中,新集二矿山西组煤中的汞主要赋存于裂隙充填的后生黄铁矿中.