【摘要】 巴音沟蛇绿混杂岩带中成薄层状产出的硅质岩、硅质泥岩的SiO2=55.37%～91.19%,Al2O3含量较高,变化在3.07～17.66,TiO2=0.12～0.8,Al2O3与TiO2具有较好的正相关关系,表明它们含有较高比例的陆源泥质沉积物质。样品经北美页岩标准化的稀土模式呈现无Ce负异常(Ce/Ce*=1.03～1.45)的平坦稀土谱型,球粒陨石标准化稀土模式为轻稀土富集,Eu具明显负异常的右倾谱型,均显示与大陆边缘沉积硅质岩、硅质泥岩相似的稀土配分模式。它们的(La/Ce)N=0.62～0.92,V/Y=0.32～8.87,Th/U=2.99～6.45,表明这些硅质岩、硅质泥岩形成于与陆源物质输入密切相关的大陆边缘环境,综合大地构造背景、蛇绿岩带中超基性、基性岩元素地球化学以及年代学分析认为,蛇绿岩就位于早石炭世晚期,形成在大陆裂谷向大洋裂谷转换并形成小洋盆的环境。更多还原

【Abstract】 The flaggy cherts and argillite in the ophiolitic mélange of Bayingou have a SiO2 content of 55.37%-91.19%,a high Al2O3 content between 3.07%-17.66%,and a TiO2 content of 0.12%-0.8%,having a good positive correlation between Al2O3 and TiO2,suggesting that they have a relatively high percentage of terrigenous muddy sediments. Moreover,they have typical NASC-normalized flat REE patterns without any visible Ce negative anomaly; and the Eu has an obvious right-hand dipping pattern. All these indicate a REE distribution pattern similar to that of deposited cherts and argillite found in continental margins. In addition,they have a Ce/Ce* ratio of 1.03-1.45,a (La/Ce)N of 0.62-0.92,a V/Y of 032-8.87,and a Th/U of 2.99-6.45,showing that the cherts and argillite are formed in continental margin settings into which the continental material can be easily transported. Therefore,the Bayingou ophiolite was formed in a transitional environment of continental rift to oceanic rift based on our study.更多还原