对博兴洼陷始新统和渐新统所取的20件泥岩样品的地球化学特征分析表明:始新统与渐新统样品稀土元素分布模式与上地壳稀土元素分布模式一致。稀土特征元素之间的比值显示始新统和渐新统沉积物源岩虽都来自后太古代,但存在着明显的差异性。根据源岩属性判别图解可以看出始新统源岩主体为长英质火山岩,渐新统则为长英质和基性岩的火山岩混合物源。多方面对比认为:始新统和渐新统沉积物源存在较大的差异性,表明始新世与渐新世之间可能存在较为明显的沉积物源改造,从一个新的视角揭示了鲁西隆起与邻近盆地在始新世与渐新世之间所发生的构造分异事件,而这次构造分异也造成了邻近盆地内始新统与渐新统之间油气藏成藏要素的差异。
The application of detrital geochemistry to determine provenance attribute is an important method for basin analysis. Geochemical characteristics of 20 mudstone samples from the Eocene and Oligocene deposits in the Boxing Sag, Jiyang Depression of Bohai Bay Basin, showed that the REE distribution pattern was similar to that of the upper continental crust. They were characterized by enrichment of LREE, flat HREE pattern and slightly negative Eu anomaly. Although the ratios of trace elements showed the materials of the source rocks for both the Eocene and the Oligocene deposits being drived from the post-Archean strata, there was an obviously difference between the materials of the source rocks between the Eocene and Oligocene deposits. According to the discrimination diagram for attribute of source rocks, the source rocks of Eocene deposits were mainly felsic volcanics, while that of Oligocene deposits were felsic and basic volcanics. The great difference between the source rocks of Eocene and Oligocene deposits suggested that there existed a clear change in provenance supply between Eocene and Oligocene, which might be resulted from the uplifting of western Shandong area, namely, a tectonic differentiation between the West Shandong Rise and neighbouring basins, which influenced oil-gas accumulation and reservoir in the Paleogene basins.