宁武煤田煤中稀土元素地球化学特征研究
Study on geochemical characteristics of rare earth elements from coal in Ningwu Coalfield
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摘要: 煤中稀土元素对于指示物源、反映沉积环境等具有重要的研究意义，且煤中稀土元素具有工业利用的潜力。为判断宁武煤田煤中稀土元素富集程度，运用电感耦合等离子质谱对宁武煤田晚古生代煤中稀土元素含量进行测定，结合X射线荧光光谱、X射线衍射、Tessier五态法逐级化学提取的测定结果，对煤中稀土元素的分布模式、物质来源、赋存状态等进行了探讨。研究表明：宁武煤田煤中稀土元素总体轻度富集，呈北高南低的分布特征。各煤层中稀土元素铕（Eu）均表现为明显负异常，表明其陆源碎屑补给的物源背景；利用La/Yb-∑REE图解分析沉积物源，主要以沉积岩和花岗岩为主，物源可能来自北部的阴山古陆。整体轻重稀土分馏不明显，但总体表现为海水影响减弱，分馏程度降低。煤中稀土元素含量与灰分及Al、Si、Fe、Mn等元素呈正相关，表明陆源碎屑是稀土元素的主要来源；逐级化学提取实验结果表明，煤中稀土元素赋存状态以硅铝酸盐结合态（74%）和有机结合态（18%）为主；由于还原性条件利于稀土元素富集，太原组煤中稀土元素的富集也与黄铁矿有关。Abstract: Rare earth elements in coal have important research significance for indicating the source and reflecting the sedimentary environment， and they also have the potential for industrial use in some regions.In order to determine the enrichment degree of rare earth elements in Late Paleozoic coal of Ningwu Coalfield， the content of rare earth elements was measured by inductively coupled plasma mass spectrometry.The results of stepwise chemical extraction with X-ray fluorescence spectrum， X-ray diffraction， and Tessier Five-state Method on the distribution patterns， material sources， and occurrence states of middle and rare earth elements were discussed.The results show that rare earth elements in Ningwu Coalfield are slightly enriched，showing the distribution characteristics of high in the north and low in the south.The rare earth element Eu in each coal seam shows obvious negative anomaly， which indicates the source background of terrigenous clastic replenishment.The La/Yb-∑REE diagram is used to analyze sedimentary sources， mainly sedimentary rocks and granite，and the sources may come from the ancient land of Yinshan in the north.The overall light and heavy rare earth fractionation is not obvious，but the overall performance is that the influence of seawater is weakened and the degree of fractionation is reduced.The content of rare earth elements in coal is positively correlated with ash and other elements such as Al， Si， Fe and Mn， indicating that terrigenous debris is the main source of rare earth elements.The results of stepwise chemical extraction show that the occurrence state of rare earth elements in coal is dominated by aluminosilicate bound (74%) and organically bound (18%)， as the reducing conditions favor the enrichment of rare earth elements， and the enrichment of rare earth elements from coal of Taiyuan Formation is also related to pyrite.
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Keywords:
- coal /
- rare earth element /
- distribution pattern /
- occurrence state
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