| 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 |
| |
| 引用本文： | 杨江海,杜远生,于鑫,黄虎,柴嵘.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[J].地球科学,2017,42(1):24-34. |
| |
| 作者姓名： | 杨江海 杜远生 于鑫 黄虎 柴嵘 |
| |
| 作者单位： | 1.中国地质大学生物地质与环境地质国家重点实验室,湖北 武汉 430074 |
| |
| 基金项目： | 中央高校基本科研业务费专项资金项目CUG160604国家自然科学基金项目41302083中央高校基本科研业务费专项资金项目CUGL140402国家自然科学基金项目41572078 |
| |
| 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.
|
| 关 键 词： | 滇东南八布 早二叠世 古特提斯洋俯冲 碎屑锆石 火山岩岩屑 岩石学 |
| 收稿时间： | 2016-08-10 |
Early Permian Volcanic Fragment-Bearing Sandstones in Babu of SoutheastYunnan: Indicative of Paleo-Tethyan Ocean Subduction |
| |
| Abstract: | Babu mafic/ultramafic rocks in Southeast Yunnan Province are interpreted as remnant ocean crust, and together with the ophiolite in Song Hien tectonic zone of North Vietnam, constitute significant components of the Babu-Song Hien Paleo-Tethyan suture, a possible southern extension of the Ailaoshan suture. Around the Babu ophiolite is a widespread siliclastic rocks dominated sequence, with thin-bedded cherts observed in some locations. These clastic rocks have long been considered to be Triassic turbidity current deposits in spite of absence of reliable fossil and isotopic dating. West to Longlin village, there outcrop coarse sandstone and sandy conglomerate beds nearby the Babu mafic/lutramific rocks. These sandstones contain andesite and rhyolite fragments and display detrital zircon age spectra similar to those of the Late Permian sandstones in Song Hien tectonic zone and Permian sandstones in western Ailaoshan belt, but distinguished from those of the Permian-Triassic clastic rocks of Youjiang and Shiwandashan basins in southwestern South China. The youngest zircon group with ages of ~285Ma, has geochemical affinities of magmatic zircons crystallized from arc/orogenic settings, corresponding to the occurrence of volcanic rock fragments, indicating a maximum depositional age, and showing an adjacent Early Permian volcanic source. The new findings of chert deposits within a clastic rock section to the east of Babu Village, and the comparison of detrital zircon U-Pb age spectra suggest that the analyzed clastic rocks should be Early Permian rather than Middle Triassic in age and their Permian volcanic source might be related to the subduction of Babu-Song Hien Paleo-Tethyan ocean. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
|
点击此处可从《地球科学》下载全文 |
|
