【摘要】 沉积岩中的微量元素和稀土元素特征对沉积环境、沉积物的物源和构造背景具有十分重要的示踪与指示作用。对采自中扬子北缘晚侏罗世-白垩纪地层的泥质岩样品中微量元素和稀土元素进行了测试与分析,结果表明,研究区微量元素中的深源元素普遍低于地壳粘土岩中的平均值,说明沉积物的来源为陆源物质,而典型陆源元素Zr、Hf的平均含量远高于地壳粘土岩中的平均含量,反映了大量的陆源物质的快速堆积。上侏罗统与下白垩统泥质岩的微量元素特征相似,而上白垩统则发生了明显的变化,表现为深源性微量元素含量较上白垩统明显降低,而陆源性微量元素含量显著增加,反映早晚白垩世之间沉积背景发生了变化。纵向上,稀土元素的变化规律显示,上白垩统与下白垩统的稀土元素特征具明显的差异,表现为Eu的负异常明显减小,Ce的负异常增大,轻稀土富集程度降低,反映了沉积作用分异度较低的特点。La-Th-Sc、Th-Co-Zr/10和Th-Sc-Zr/10构造环境判别图及La/Th-Hf和Th/Sc-Sc比值图表明,中扬子北缘晚侏罗世-白垩纪沉积岩物源区的构造背景以大陆岛弧型为主,可能也存在类似被动大陆边缘构造背景。更多还原

【Abstract】 The chemical composition of sedimentary rocks contains important records for understanding how the continental crust evolves through geological time.Several previous studies have shown that the characteristics of trace element and rare earth element(REE) in sediments are very important for tracing the environment of deposition, the source province and tectonic settings.In this paper, ten argillaceous rock samples collected from the Upper Jurassic to Cretaceous sediments in the north margin of the mid Yangtze region, China, were analyzed for trace element and rare earth concentrations.Trace elements such as Li, V, Cr, Co, Ni, Cu, Ga, Rb, Sr, Y, Ba and U are depleted, which are lower than the mean value of crustal argillaceous rocks, whereas Zr and Hf are highly enriched, indicating major contributions from massive detrital material of terrigenous origin.The REE patterns also change dramatically with time from the Upper to the Lower Cretaceous, with reducing Eu negative anomaly and light rare earth element enrichment, and increasing Ce negative anomaly, which reflect decreased sedimentary differentiation.The tectonic setting of sedimentary provinces of the north margin of the mid-Yangtze is classified as mainly continental island arc, with some similarities to passive continental margin environment, based on La-Th-Sc, Th-Co-Zr/10, Th- Sc-Zr/10, La/Th-Hf, Th/Sc-Sc, Th/U discrimination plots.更多还原