【作者】 王俊峰；

【导师】 洪天求； 贾志海；

【作者基本信息】 合肥工业大学 ， 矿物学、岩石学、矿床学， 2016， 硕士

【摘要】 安徽巢湖北部地区的下三叠统南陵湖组发育齐全,出露完好,层序清楚,与下伏下三叠统和龙山组薄层泥质灰岩呈整合接触,与上覆中三叠统周冲村组(东马鞍山组)白云质灰岩呈假整合接触,是研究下扬子地块下三叠统的重要地区。该区下三叠统南陵湖组含有三种形式的硅质沉积：层间燧石结核、层内燧石结核和层内燧石条带。本研究以巢湖北部地区南陵湖组燧石的主量元素和稀土元素地球化学特征的分析为重点,并将其与南一南下加利福尼亚半岛类似燧石的地球特征进行对比,以探讨燧石的形成环境及其硅质来源。通过分析南陵湖组原生燧石的主量元素和稀土元素地球化学特征,本研究发现其与加利福尼亚半岛燧石结核的同类地球化学特征具有很高的相似性。进一步的研究表明,两个沉积区所处的大地构造环境也极为相似,即二者均位于洋壳一陆壳俯冲带附近。其中,加利福尼亚半岛外海的燧石产于太平洋板块与北美版块的俯冲带附近,而本研究讨论的早三叠世南陵湖组燧石形成于下扬子地块与中朝地块的俯冲带附近,火山活动为燧石的形成提供了硅质来源。更多还原

【Abstract】 Lower Triassic Nanlinghu Formation is well exposed in Majiashan area, Northwest area of Chaohu City, Anhui Province, East China, which is worldwide famous because of occurrence of the earlist ichthyosaurs. The Nanlinghu Formation is here conformably contacted with underlying nodular limestone of the Helongshan Formation and unconformably with overlying Middle Triassic dolomitic limestone of the Zhouchongcun (Dongmaanshan) Formation.Three types of siliceous sedimentary from Nanlinghu Formation were found in the studied area:chert nodules between layers、chert lenses and bedded chert within layer. By comparing chemical analysis results of chert of the Nanlinghu Formation with the same analysis results of chert of Southern California, and in reference of chemical analyses of chert of Permian Qixia Formation, the formation environment and siliceous source of chert was discussed.Further research suggests that the studied area in late Early Triassic lay in the subduction zone between Yangtze plate and the North China plate, which is very similar to Southern California now. Based on the previous studies and evidences found in the research, it is concluded that main siliceous source of the Nanlinghu Formation in the studied area was provided by volcanic activities.更多还原