四川宣汉地区吴家坪组发育薄层状硅质岩、条带状硅质岩以及似层状燧石结核等类型的硅质岩。以宣汉渡口镇羊鼓洞剖面为基础，对不同类型硅质岩的稀土元素和微量元素地球化学特征进行分析后认为：稀土元素∑REE总量相对较低，在岩性上有似层状燧石结核—条带状硅质岩—薄层状硅质岩递增的趋势。标准化的稀土元素具有低—中等δCe负异常、中等的La_n/Ce_n、La_n/Yb_n和δEu多数为负异常的特点，显示硅质岩为大陆边缘—广海平原的成因环境。微量元素Co、Ni、As和Sb等元素反映出其非热水沉积的特点。综合露头地球化学特征，认为四川盆地东北部二叠系吴家坪组的硅质岩形成的环境以大陆边缘—广海平原环境为主，其中部分条带状硅质岩受较弱热水沉积的影响。

The different types of siliceous rocks(i.e.flaggy siliceous,striped siliceous and striped chert noddle) occurr in the Wujiaping Formation,Xuanhan area of Sichuan basin.The rare earth elements and trace elements in different siliceous rocks from Yanggudong section in Dukou town,Xuanhan County,were measured.The total volume of rare earth elements is relatively low,and shows the increasing tendency from striped chert noddle to striped siliceous rocks and flaggy siliceous rocks in turns.The shale-normalized rare earth elements have slight to intermediate negative δCe anomalies,intermediate ratios of La_n/Ce_n, La_n/Yb_n and an overwhelming majority negative δEu anomalies,suggesting the continental margin and open-ocean basin environment for siliceous rocks.Trace elements of Co,Ni,As and Sb elements indicate that siliceous rocks would be formed under non-hydrothermal deposition.Integrating the outcrop geochemical characteristics in NE Sichuan Basin,these suggest the sedimentary environment of Wujiaping Formation siliceous rocks mainly continental margin and open-ocean basin,and part of striped siliceous rocks influenced by weak hydrothermal fluids.