琼东南盆地中央峡谷早上新世沉积物稀土元素特征及物源分析

Features and Source Analysis on Early Pliocene Sedimentary Rare Earth Element(REE) in Central Canyon of Qiongdongnan Basin

为确定琼东南盆地中央峡谷早上新世沉积物(距今5.5Ma)物质来源,取中央峡谷沉积物样品进行稀土元素分析,经球粒陨石标准化后,在稀土元素含量分布模式中呈斜率负值的形式,轻稀土元素相对富集,具有较高的∑LREE/∑HREE值(轻稀土元素总量与重稀土元素总量比值),平均为13.23,中等正Eu异常,δEuN(Eu异常)平均为3.29。经对比发现,其特征与红河沉积物最为相似,断定沉积物主要来自于红河物源,在琼东南盆地的流向为自西向东流;此外,δEuN值与∑LREE/∑HREE记录了母岩区的特征,而不受搬运、水动力、沉积、成岩及变质作用影响,是成功判别中央峡谷沉积物来源的关键。

The REE analysis was an important method of provenance analysis.In order to determine the provenance of the sediments of the 5.5Ma central canyon in Qiongdongnan Basin,the analysis of REE was carried out.After the pelletal cosmolites were normalized,the REE distribution pattern was a negative slope with relative REE enrichment,there were medium normal-abnormity of Eu(avg.3.29)and high ∑LREE/∑HREE value(avg.13.23).Though the analysis and comparison,it is found out that the REE characteristics of is the most similar with that of Red River.The flow direction of the central canyon is from west to east in the Qiongdongnan Basin.In addition,δEuN and∑LREE/∑HREE values have the characteristics of their parent rocks,it is not influenced by the processes of transportation,hydrodynamics,deposition,diagenesis and metamorphism,so they are the key parameters for successful judging the provenance of the area.