| 鄂尔多斯盆地北缘延安组2号煤层稀土元素异常原因及其地质意义 |
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| 引用本文： | 杨毅,吕大炜,张建强,吴盾.鄂尔多斯盆地北缘延安组2号煤层稀土元素异常原因及其地质意义[J].煤田地质与勘探,2020,48(2):78-84. |
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| 作者姓名： | 杨毅 吕大炜 张建强 吴盾 |
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| 作者单位： | 山东科技大学 山东省沉积成矿与沉积矿产重点实验室,山东 青岛 266590;安徽省核工业勘查技术总院,安徽 芜湖 241003;山东科技大学 山东省沉积成矿与沉积矿产重点实验室,山东 青岛 266590;中国煤炭地质总局勘查研究总院,北京 100039;中国科学技术大学 地球与空间科学学院,安徽 合肥 230026 |
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| 基金项目： | 国家重点研发计划;中国地调局地质调查项目 |
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| 摘 要： | 鄂尔多斯盆地北缘延安组2号煤层稀土元素的异常原因一直存在着争议，以2号煤发育较完整的榆林大海则煤矿为例，运用电感耦合等离子质谱（ICP-MS）、扫描电子显微镜（SEM）等方法，分析煤及夹矸中稀土元素（REE）含量及其矿物学特征，并揭示稀土元素异常原因。结果显示:煤中总稀土元素（∑REE）含量为3.71~46.21 μg/g，轻稀土元素（LREE，La-Eu）比重稀土元素（HREE，Gd-Lu）更富集；稀土元素标准化配分模式图显示少数样品为Eu正异常；稀土元素含量较高的样品和拥有Eu正异常的样品主要分布在与夹矸距离较近的煤层中，表明煤中稀土元素分布受到了夹矸的影响；在夹矸中发现很多晶型较好的锆石、磷灰石、透长石及锐钛矿，这些矿物是在聚煤过程中接受火山物质的直接证据。综合认为，鄂尔多斯盆地延安组2号煤沉积期，盆地周缘存在一次火山活动，火山灰降落覆盖在泥炭沼泽之上，影响了聚煤作用，致使煤中稀土元素分布异常。研究结果解释了鄂尔多斯盆地北缘的煤中稀土元素异常原因，为研究区煤的加工利用方式提供参考。
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| 关 键 词： | 稀土元素(REE) 矿物学 Eu异常 火山活动 鄂尔多斯盆地 |
| 收稿时间： | 2019-11-21 |
Causes of anomaly of rare earth elements of seam 2 of Yan'an Formation in the northern margin of Ordos basin and its geological significance |
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| Abstract: | The cause of rare earth elements(REE) anomalies in No.2 coal seam of the Yan'an Formation in the northern margin of the Ordos basin has been controversial. This paper takes Dahaize coal mine, Yulin area with well developed No.2 coal as an example to analyze REE, mineralogical characteristics of coal and partings, and to reveal the causes of anomaly of REE by Inductive Coupled Plasma Mass Spectrometry(ICP-MS) and Scanning Electron Microscopy(SEM). The results show that the total rare earth element(∑REE) concentration in the coal samples ranges from 3.71 to 46.21 μg/g. Light rare earths elements(LREE, La-Eu) are more abundant than heavy rare earth elements(HREE, Gd-Lu). The distribution patterns of their normalization show that a few of samples have positive anomalies. Samples with high REE content and samples with positive Eu anomalies mainly appeared in the analyzed coal seam close to the partings. It is indicated that the distribution of REE in coal is affected by its partings. There are many zircons, apatites, sanidines and anatase with better crystal form found in the partings, which are direct evidence of the volcanic activity during the peat formation. This suggests that there was a volcanic activity during the No.2 peat formation of the Yan'an Formation in Ordos basin. The volcanic ash fallen over and covered the swamp and affected the coal accumulation and the abnormal distribution of REE in the coal. The results explain the reason of REE anomaly in the coal and provide data support or theoretical basis for the future industrial use of REE in the coal in this area. |
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