高级检索

鄂尔多斯盆地石炭—二叠纪太原组煤中稀土元素地球化学特征以宁东煤田为例

Geochemistry characteristics of rare earth elements in the permo-carboniferous Taiyuan Formation coal in Ordos Basin—Taking Ningdong coalfield as an example

  • 摘要: 煤中稀土元素地球化学特征的研究在聚煤盆地沉积环境和物质来源等方面具有重要指示意义。为进一步探讨鄂尔多斯盆地石炭—二叠纪煤中系统元素地球化学特征,以宁东煤田晚古生代石炭—二叠纪太原组煤为研究对象,运用电感耦合等离子体质谱、X射线荧光光谱、X射线衍射等方法分析了煤中稀土元素的地球化学特征,探讨了煤中稀土元素的赋存特征及成因。结果表明:宁东煤田石炭-二叠纪太原组煤中稀土元素含量均值为91.19 μg/g,低于中国煤中稀土元素含量均值(135.89 μg/g),Eu负异常明显,Ce异常不明显,LaN/YbN、LaN/LuN、LaN/SmN、LREE/HREE等稀土元素参数以及上地壳标准化的REE配分模式均反映轻重稀土元素分馏较低和重稀土相对富集的特征。煤中稀土元素继承了源岩区稀土元素的特征,在沉积、成煤作用阶段,在温度、压力、pH值及氧化还原条件的综合作用下,主要赋存于黏土矿物中,此可从其与灰分产率、Si、Al、Na、K等具有正相关关系加以佐证。∑REY-La/Yb、∑REE-δCe/δEu、ΣREE-La/Lu图解指示宁东煤田石炭—二叠纪煤中形成于下三角洲平原及下三角洲-三角洲平原沉积背景,均受到海水不同程度的影响。宁东煤田石炭-二叠纪太原组煤中稀土元素来源、含量及赋存特征主要受控于长英质陆源碎屑供给,但同时也受到局部微地形、微地貌和微环境的影响,海水与成岩作用对其影响有限。

     

    Abstract: The study of the geochemical characteristics of rare earth elements (REE) in coal has important indicative significance in terms of sedimentary environment and material source in coal basin. In order to further explore the geochemical characteristics of systematic elements in Carboniferous-Permian coal in the Ordos Basin, taking the Permo-Carboniferous Taiyuan Formation (Fm) coal in Nindong coalfield as the research object to study the geochemistry characteristics of REE and discussed its occurrence characteristics and origin, base on the data from X-ray fluorescence spectrometer and plasma mass spectrometer. The result show that: The average content of REE in Permo-Carboniferous Taiyuan Fm coals from Nindong coalfield is 91.91 μg/g, which is lower than the average content of 135.89 μg/g in China coals. The obviously negative Eu abnormity, unobvious Ce abnormity, LaN/YbN, LaN/LuN, LaN/SmN, LREE/HREE and the REE distribution patterns normalized by the upper crust all reflect the characteristics of low fractionation of light and heavy REE and relative enrichment of heavy rare earth elements in coals. The REE in the coal inherit the characteristics of the rare earth elements in the source rock area, and in the sedimentary and coal-forming stages, under the combined action of temperature, pressure, pH value and redox conditions. The REE in coal mainly occurs in clay minerals, which can be verified by the positive correlation between rare earth elements and ash, Si, Al, Na, K. The diagrams of ∑Lei-La/Ibu, ∑-Li-δ/δ-Ou, and Σli-La/Lu indicate that the Carboniferous-Permian coal in the Ningdong coalfield was formed in the sedimentary setting of the Lower Delta Plain and the Lower Delta-Delta Plain, all of which were affected by seawater to varying degrees. The source, content and occurrence characteristics of REE in Permo-Carboniferous Taiyuan Fm coals from Ningdong coalfield are mainly controlled by the supply of felsic terrigenous clasts, but also affected by local micro-topography, micro-geomorphology and micro-environment, the impact of seawater and diagenesis are limited.

     

/

返回文章
返回