班公湖-怒江洋复理石沉积时代:来自改则县亚多村碎屑锆石的制约  

Age of Flysch in Bangong-Nujiang Ocean:Constraints of Detrital Zircon from Yaduo Village of Gerze County

作　　者：罗安波 范建军[1] 王明[1] 曾孝文[1] Luo Anbo;Fan Jianjun;Wang Ming;Zeng Xiaowen(College of Earth Sciences,Jilin University,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院

出　　处：《地球科学》2019年第7期2426-2440,共15页Earth Science

基　　金：国家自然科学基金项目(Nos.41702227,41402190);中国地质调查局区域地质调查项目(Nos.DD20160026,121201010000150014)

摘　　要：木嘎岗日岩群是班公湖-怒江洋的洋盆沉积记录,它的时代归属对约束班公湖-怒江洋的演化具有重要意义.然而自命名以来,木嘎岗日岩群的时代一直争议较大.以班公湖-怒江缝合带中段改则县亚多村一带的木嘎岗日岩群为研究对象,对其进行岩石学和碎屑锆石年代学方面的研究.该区木嘎岗日岩群以薄层砂岩和页岩互层为主,具复理石沉积特征.砂岩碎屑锆石年代学分析结果显示,最小碎屑锆石为149 Ma,最小年龄峰值为156 Ma,指示该地区木嘎岗日岩群的时代为晚侏罗世-早白垩世.在此基础上,对班公湖-怒江缝合带中西段内不同地区木嘎岗日岩群的年龄信息进行搜集和整理,结果显示,木嘎岗日岩群的时代跨度至少为晚三叠世-早白垩世,表明班公湖-怒江洋中西段在晚三叠世-早白垩世内可能是连续演化的.The Mugagangri Group is an oceanic basin sedimentary record of Bangong-Nujiang Ocean. However, the age of Mugagangri Group has been controversial since it was named. In this paper, the Mugagangri Group in Yaduo Village of Gerze County, central part of Bangong-Nujiang suture zone, is selected as the research object. We have carried out detailed petrological and clastic zircons chronology studies on it. Our research shows the Mugagangri Group in this area is mainly composed of thin sandstone and shale interbeds, which have characteristic of flysch. The chronological analysis of sandstone clastic zircons shows that the minimum clastic zircon is 149 Ma and the minimum age peak is 156 Ma, indicating that the age of the Mugagangri Group in this area is from Late Jurassic to Early Cretaceous. In addition, the age information of Mugagangri Group in different areas of the central and western parts of the Bangong-Nujiang suture zone are collected and analyzed in detail as well. The results show that the age span of the Mugagangri Group is at least Late Triassic-Early Cretaceous, suggesting that the middle and western parts of the Bangong-Nujiang Ocean may have evolved continuously during the Late Triassic-Early Cretaceous.

关 键 词：青藏高原 木嘎岗日岩群 班公湖-怒江缝合带 碎屑锆石 年代学 

分 类 号：P534.5[天文地球—古生物学与地层学]