东海盆地丽水凹陷古新统沉积岩的稀土元素地球化学特征

采用等离子体质谱分析法测试了东海盆地丽水凹陷古新统砂泥岩样品的稀土元素含量,结果表明,稀土总量在82 2×10-6～182×10-6之间,平均为144×10-6;w(LREE)/w(HREE)比值在4 54～10 02之间,平均为8 67,相对富集LREE;Eu基本为负异常,δEu在0 59～1 03之间,平均为0 73;δCe在0 92～1 09之间,平均为0 98,Ce正常或具微弱的负异常;(w(La)/w(Yb))N在8 23～11 61之间,样品的分布曲线为轻稀土元素富集、重稀土元素亏损型。样品稀土元素的地球化学特征反映当时丽水凹陷为海陆交替的沉积环境,水介质环境为缺氧的还原条件,盆地类型应为稳定的克拉通盆地,物源区母岩主要为花岗岩。

THE REE GEOCHEMICAL CHARACTERISTICS OF PALEOCENE-EOCENE IN THE LISHUI SAG OF THE DONGHAI BASIN

An ICP-MS(Inductively Coupled Plasma-Mass Spectrometry) method is used to determine the contents of rare earth element of Paleocene-Eocene samples in the Lishui sag. The result shows that the REE content ranges from 82.2×10~-6) to 182×10~-6),and the contents of most samples approach the average of REE contents in sediments in the world; The REE distribution pattern of samples is characterized by a"V-shape") curve with slightly negative Ce anomaly and obviously negative Eu anomaly.The fractionation pattern is right-declined,and LREE are obviously richer.According to the REE content and its variation,the rare earth element pattern indicates that its provenance is the mixing of claystone and granite. According to the values of _δ_Ce, the authors suggest that the paleo-environment is mainly marine and sometimes continental environment.