湘西北永顺地区志留系砂岩稀土元素地球化学特征及其地质意义

    REE geochemical characteristics and geological significance of Silurian sandstone in Yongshun area of Northwestern Hunan

    • 摘要: 受华夏板块与扬子板块碰撞影响,上扬子海域周边在志留纪发育古隆起,区内沉积物的物源较为复杂。为研究湘西北永顺地区志留纪的沉积环境,对该地区志留系砂岩中稀土元素的地球化学特征开展分析。结果表明: 样品轻稀土和重稀土元素分异明显,轻稀土元素富集、重稀土元素呈平坦型,具明显的负Eu异常,Ce异常不显著,Ceanom值指示研究区在志留纪为缺氧的弱还原环境。稀土元素地球化学特征显示该区志留系沉积速率整体较快,结合研究区的沉积构造特征及前人的古地理研究成果,认为研究区志留系的物源为雪峰山隆起的沉积岩。研究可为湘西北地区志留系的岩相古地理恢复提供参考。

       

      Abstract: Affected by the collision between Cathaysian Plate and Yangtze Plate, the ancient uplifts around Upper Yangtze Sea area developed during the Silurian period, and the sediment sources in the study area were complex. In order to investigate the sedimentary environment of Silurian strata in Yongshun area of Northwestern Hunan, the authors in this paper studied the REE geochemical characteristics of Silurian sandstone in this area. The results show that the differentiation between LREE and HREE is obvious in samples, with rich LREE and flat HREE. Eu is of obviously negative anomaly, and Ce is normal. The palaeoenvironment of the Silurian period in the study area was anoxic and weak reduction environment, implied by Ceanom results. The geochemical characteristics of REE indicate that the sedimentary rate of the Silurian period in the study area is fast. Combined with structural features and achievements in palaeogeography of predecessors, the authors in this paper suggest that the provenance of the study area comes from the sedimentary rock in Xuefeng Mountain uplift, which can provide some reference for lithofacies paleogeography restoration of Silurian in Northwestern Hunan.

       

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