滇东南八布早二叠世含火山岩屑砂岩指示古特提斯洋俯冲

发布时间：2018-03-18 11:07

  本文选题：滇东南八布　切入点：早二叠世　出处：《地球科学》2017年01期 　论文类型：期刊论文

【摘要】：滇东南八布基性/超基性岩体被认为代表洋壳残片,与越北Song Hien构造带内的蛇绿岩体共同构成八布-Song Hien古特提斯缝合带的重要岩石记录,是认识华南西南缘古特提斯构造演化的重要窗口.环绕八布基性/超基性岩体分布大面积碎屑岩系,内夹有硅质岩序列,长期以来被认为是三叠纪浊流沉积,但缺少确切的古生物化石和放射性年代学证据.为确定这套碎屑岩的沉积时代和物质来源,对紧邻八布岩体的龙林西含火山岩屑砂砾岩进行LA-ICPMS碎屑锆石U-Pb同位素和微量元素分析.结果显示,碎屑锆石年龄谱与华南西南缘的二叠系-三叠系年龄谱明显不同,但与Song Hien构造带晚二叠世砂岩和哀牢山带绿春二叠纪砂岩年龄谱相似.最年轻锆石年龄组约为285Ma,在微量元素组成上与弧/造山型岩浆结晶锆石一致,对应于安山质-流纹质火山岩屑,指示早二叠世火山岩浆活动.结合碎屑锆石年龄谱的对比分析和八布村东硅质岩序列的新发现,结果表明八布碎屑岩的沉积时代应为早二叠世,而非中三叠世,其早二叠世火山岩源区与八布-Song Hien古特提斯洋俯冲有关.
[Abstract]:The octagonal / ultrabasic rock bodies in southeastern Yunnan are considered to represent oceanic crust fragments, and together with the ophiolite within the Song Hien tectonic belt in the northern part of Yunnan, constitute an important rock record in the paleoTethys suture zone of Babu Song Hien. It is an important window to understand the evolution of PaleoTethys structure in the southwestern margin of South China. A large area of clastic rock series is distributed around the octagonal / ultrabasic rock bodies with siliceous sequences in it, and it has long been considered to be a Triassic turbidite deposit. In order to determine the sedimentary age and material source of this set of clastic rocks, Zircon U-Pb isotopes and trace elements of LA-ICPMS clastic zircon are analyzed in the clastic sand-gravel rocks of Longlinxi, adjacent to the Babu rock body. The results show that the age spectrum of the clastic zircon is obviously different from that of the Permian-Triassic age spectrum in the southwestern margin of South China. But it is similar to the late Permian sandstone age spectrum of the Song Hien tectonic belt and the Luchun Permian sandstone age spectrum of the Ailaoshan belt. The youngest zircon age group is about 285 Ma.The trace element composition is consistent with the arc / orogenic magmatic crystalline zircon. Corresponding to the anshanshanlitic volcanic rocks, they indicate the early Permian volcanic magma activity, combined with the comparative analysis of the age spectrum of clastic zircon and the new discovery of the Babucundong siliceous sequence. The results show that the sedimentary age of the Bubu clastic rocks is the early Permian, not the Middle Triassic. The source of the early Permian volcanic rocks is related to the paleoTethys ocean subduction of Babu Song Hien.
【作者单位】： 中国地质大学生物地质与环境地质国家重点实验室;中国地质大学地球科学学院;成都理工大学沉积地质研究院;
【基金】：国家自然科学基金项目(Nos.41302083,41572078) 中央高校基本科研业务费专项资金项目(Nos.CUGL140402,CUG160604)
【分类号】：P588.2;P534.51
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本文编号：1629314