南堡凹陷沉积岩化学元素分布特征及多元统计方法研究

对南堡凹陷Ed1亚段、Ng下、Ng上、Nm底地层的75个沉积岩样品进行了主量、微量元素分析，结果表明粒度效应造成砂岩和泥岩元素丰度明显不同，砂岩除富集K、Na、Sr、Ba、Si外，其余元素均较泥岩亏损.根据地层垂向上元素丰度由高—低—高的变化规律，可将这4个亚段分为Ed1、Ng下和Ng上、Nm底3个阶段，与凹陷构造演化特征响应.因子分析、聚类分析等多元统计方法表明，表生环境中元素具有不同的迁移富集规律，Ca、Na、Sr等具有较强的活动性，Zr、Hf等少数元素则在粗粒级中含量较高，而其余元素则多在黏土粒级中富集.元素在表生环境中地球化学行为的不同主要受化学结构特征控制，沉积环境对其也有影响.

DISTRIBUTION CHARACTERISTICS OF ELEMENTS IN SEDIMENTARY ROCKS OF NANPU SAG AND THEIR MULTIPLE STATISTIC ANALYSIS

Seventy-five sedimentary rock samples from Nanpu Sag,involving Ed1 sub-member,Ngl sub-member,Ngu sub-member and Nmb strata,have been studied on the major elements composition,trace elements and rare earth elements.The results show that sandstone and mudstone apparently differ in element compositions due to granularity effect.Most element contents in sandstone are lower than those in mudstones except a few elements,such as K,Na,Sr,Ba and Si.According to the discipline of element compositions changing in the vertical section that element contents change from low to high and to low again,the four sub-members can be divided into three stages.These stages are affected and controlled by tectonic movement of Nanpu Sag.Multiple statistic analysis of element geochemical characteristics reveals that elements have different behaviors of migration and enrichment in hypergene environment.Ca,Na and Sr have strong activity compared with other elements.Zr and Hf are rich in coarse grains.The geochemical behaviors of element in hypergene environment are mainly controlled by the characteristics of chemical structures,and also affected by sedimentary environment.