中文摘要：

对中上扬子北缘二叠纪碎屑岩成分和地球化学特征进行了分析。结果表明, 本次研究的碎屑岩物源主要来自上部大陆壳, 沉积旋回不高, 大部分样品来自基性岩和长英质火山源区。主元素受到风化作用和沉积后作用的影响, 对区分构造环境意义不大; 几种非迁移性微量元素, 如Cr、Co、Th、Sc、La 和Zr, 较元素有区分构造环境意义。本次研究的碎屑岩非迁移性元素比值La/Sc、Th/Sc、Th/Co 和Th/Cr 与大陆上地壳和硅质砂岩的特征值接近, 与大陆下地壳、洋壳和基性砂岩的特征值相差较大。综合碎屑岩组分、主元素、微量元素和稀土元素的判别结果, 认为镇安西口样品的构造背景主要为大陆岛弧-活动大陆边缘, 与商丹缝合带沉积岩系相同。镇安西口二叠纪碎屑岩成分和地球化学特征与泥盆纪基本类似, 反映了北秦岭古大陆边缘沉积特征; 华蓥山样品呈现出多源性特点, 其构造背景为板内环境。

英文摘要：

The detrital modes and geochemical characteristics of Permian clastic rocks in the northern margin of the Middle and Upper Yangtze region are analyzed. The results show that these rocks are dominantly products of upper continental crust and have low degree of sediment recycling. Most samples were derived from basic and felsic volcanic rocks. However, major elements geochemistry is less useful for interpreting the tectonic setting,because of weathering and post-depositional process, than immobile trace elements such as Cr, Co, Th, Sc, La and Zr. The values of La/Sc, Th/Sc, Th/Co and Th/Cr of the clastic rocks show affinity closer to the upper continental crust and siliceous sandstone than the lower continental crust, oceanic crust and basic sandstone. Based on the composition and geochemical characteristics of major elements, trace elements and REE, it can be summarized that the tectonic settings of Xikou, Zhen’an county was mainly continental island arc-active continental margin which is similar to that of Shangdan Suture Zone, and the similarity of clastic rocks between Permian and Devonian may reflect the feature of paleo-continental margin of the North Qinling. The samples of Huaying Mountain were derived from multiple provenances of intraplate tectonic settings.