贵州瓮安磷矿陡山沱组地层元素地球化学特征

The Geochemistry of Phosphorite of Doushantuo Formation in Weng'an,China: Insights from Trace Elements and REE

瓮安陡山沱组上磷矿层含有大量早期多细胞动物化石(瓮安生物群),而陡山沱组下磷矿层未发现该生物群,说明上下两个磷矿层体现了不同的沉积环境。上磷矿层的氧化还原敏感元素Mo,U,V含量较下磷矿层要低很多。底部白云岩层、下磷矿层和中部白云岩层,无Ce异常,而上磷矿层和灯影组白云岩层Ce为负异常。这些表明,瓮安陡山沱组地层形成的海水沉积环境由下部的缺氧环境向上部的氧化环境转变。

The upper phosphorite bed of the Neoproterozoic Doushantuo Formation at Weng＇ an in South China preserves a unique assemblage of earliest metazoan fossils （ Weng＇an biota＂ ）, whereas no animal forms have been found in the lower phosphorite bed. The two phosphorite units display significant differences in their depositional environments. The upper phosphorite bed has a distinctive negative Ce anomaly and low redox-sensitive element contents. The lower phosphorite bed has a much less negative Ce anomaly and higher redox-sensitive element contents. These data suggest a change in the marine paleoenvironment from anoxic in the lower ore bed to suboxic or oxic in the upper ore bed.