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, Ng_l sub-member, Ng_u sub-member and Nm_b 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.