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    鄂尔多斯盆地彭阳地区洛河组砂岩褪色蚀变特征及对铀成矿流体的指示作用

    Alteration characteristics and implication to uranium metallogenetic fluids of faded sandstones in Luohe Formation, Pengyang area, Ordos Basin

    • 摘要:
      研究目的 红层含铀岩系褪色蚀变与还原蚀变作用密切相关,褪色蚀变特征及其成因流体分析对深入认识铀成矿流体和成矿机理具有重要意义。
      研究方法 基于彭阳地区洛河组砂岩褪色蚀变现象及其与铀异常的密切关系,通过岩心编录、元素地球化学测试、高分辨率电镜扫描、电子探针分析、岩心XRF荧光及红外光谱扫描等手段,开展洛河组砂岩沉积特征和褪色蚀变特征分析。
      研究结果 洛河组不同颜色砂岩碎屑含量高,且成分以石英为主,具有典型沙漠相与风成沉积特点;洛河组典型褪色蚀变砂岩一般具有铀矿物、黄铁矿及石膏富集而三价铁氧化物含量低的特点,且铀与硫元素含量明显较高。
      结论 洛河组砂岩主体形成于氧化条件的风成沉积,其颜色、Fe2O3/FeO、Th/U及Cu/Zn反映了随砂岩褪色程度增强,环境发生了由氧化向还原状态的转变;洛河组褪色蚀变与铀矿成矿作用在空间、矿物组合及氧化还原状态的一致性暗示了二者成因与同一还原性流体有关。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective The faded alteration of uranium−bearing rock series in the redbed is closely related to reductive alteration, and the analysis of the characteristics of faded alteration and its genetic fluid is of great significance for understanding the uranium ore−forming fluids and ore−forming mechanism.
      Methods This study is based on analyzing the sedimentary characteristics and faded alteration characteristics of sandstones in Luohe Formation by means of core logging, element geochemical test, electron microscope scanning, electron probe analysis, XRF scanning and core infrared spectrum scanning.
      Results The sandstones in the Luohe Formation are basically formed in aeolian sedimentary with oxidation conditions mineral assemblages enriched in uranium minerals, pyrite and gypsum but little trivalent iron oxides, and uranium and sulfur elements show obvious migration. Then, the redox state of sandstone and the correlation between uranium mineralization and faded alteration were discussed.
      Conclusions The main body of Luohe Formation sandstone was formed in aeolian deposits under oxidation conditions, and its color, Fe2O3/FeO, Th/U and Cu/Zn reflect that the environment has been changed from oxidation to reduction with the increase of sandstone faded degree. The characteristics of the consistency between faded alteration and uranium mineralization in Luohe Formation in space, mineral association and redox state suggest that their genesis is related to the same reducing fluid.

       

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