淮南煤田太原组铝质泥岩元素地球化学特征

The elemental geochemical characteristics of aluminous argillites in Taiyuan Formation from Huainan coalfield

  • 摘要: 华北聚煤盆地南缘淮南煤田晚石炭世-早二叠世太原组含煤岩系普遍沉积铝质泥岩,然而,对于多层铝质泥岩的形成条件及其地球化学特征尚未开展深入研究。在本次研究中,系统采集了淮南煤田张集煤矿补Y1钻孔岩心样品,采用XRF和ICP-OES、ICP-MS分别测试了主量元素和微量元素,对铝质泥岩地球化学特征及其地质成因进行分析。结果表明:不同层位的铝质泥岩来源于同一源区,铝土质泥岩可能受到了更强烈的红土化作用导致其明显偏离SiO2/Al2O3和Fe2O3/Al2O3趋势线;Sr/Ba的结果表明铝质泥岩是在不稳定的海陆交互沉积环境下形成的,V/Cr和V/(V+Ni)的结果表明铝质泥岩是在贫氧到厌氧的沉积环境中形成的;综合主量元素和微量元素的结果,表明了不同层位铝质泥岩的母岩可能是附近古陆的中酸性火成岩,母岩风化产物经迁移至淮南地区沉积成岩。

     

    Abstract: Aluminous argillites are widely deposited in the Late Carboniferous to Early Permian Taiyuan Formation of Huainan coalfield at the southeast margin of the North China Plate. However, knowledge about their formation conditions and geochemical characterizations are not presently known. We collected samples from a borehole in Zhangji coal mine and tested their geochemical parameters, including major and trace elements, by XRF and ICP-OES and ICP-MS, respectively. The geochemical characteristics and geological origin of Huainan aluminous argillites were investigated. Results show that:nearly all the argillites have comparable ratios of SiO2/Al2O3 and Fe2O3/Al2O3, suggesting that they were possibly derived from the same source materials, however, bauxitic argillites significantly deviate from the correlation slopes, indicating that they probably suffered a more extensive laterization than aluminous argillites; the Sr/Ba ratios of the studied argillite sam-ples were possibly deposited in an unstable paleodepositional environment, while the V/Cr and V/(V+Ni) ratios suggested an anoxic environment; based on the comprehensive consideration of major and trace element results, the studied aluminous argillites probably derived from the common parent rocks composed of felsic to intermediate igneous rocks. These argillites were presumably deposited under anoxic environments in Huainan area.

     

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