摘要
位于吉尔吉斯斯坦南天山缝合带附近的Djanydjer蛇绿混杂岩由蛇纹石化橄榄岩、辉长岩、玄武岩、硅质岩等组成。通过对辉长岩中锆石U-Pb年代学研究获得两组年龄：（422.0±2.0）Ma（MSWD=1.2）,（397.3±3.9）Ma（MSWD=0.6）。结合境内外南天山蛇绿混杂岩的年代学特征,认为前者代表辉长岩的形成时代,表明分割吉尔吉斯斯坦中天山和塔里木克拉通的洋盆在晚志留世早期已经存在。由辉长岩中获得的中泥盆世年龄可能与洋壳闭合-蛇绿岩构造侵位或后期花岗质岩浆侵入作用相关。与Djanydjer蛇绿混杂岩产出于同一构造带上的变质沉积岩组合,一直以来被认为是前寒武纪的变质地体,文中对其中的白云母石英片岩的研究发现,其碎屑锆石记录了较宽的年龄范围（406~2 856 Ma）。通过与阿特巴什变质硬砂岩中的碎屑锆石和塔里木克拉通岩浆锆石的比较发现,白云母石英片岩与包裹榴辉岩的变质杂岩相似,原岩的沉积时代不早于早泥盆世,其部分物源可能来自吉尔吉斯中天山—北天山。
Djanydjer ophiolitic m61ange in the Kyrgyzstan, South Tianshan suture are composed of serpentinized peridotite, gabbro, basalt and chert. Two groups U-Pb zircon ages of 422. 0±2. 0 Ma（MSWD=I. 2） and 397. 3± 3.9 Ma （MSWD = 0. 6） have obtained for the gabbro. Considered with chronology studies of ophiolites in China-Kyrgrz, South Tianshan, the older age （422 Ma） represents the crystallization of gabhro, which implies the oceanic basin separated the Tarim craton and Kyrgyz Middle Tianshan terrane has existed in the early stage of the Late Silurian. The younger age might be related to metamorphism during the oceanic lithosphere obduction or the post-collisional magmatism. Muscovite-quartz schist in the same belt with Djartydjer ophiolitic mfilange was considered as a part of Precambrian metamorphic terrane. It has similar petrology and deformation characteristics with the host rocks of Atbashi ecologite. Its detrital zircons vary widely in age from 406 Ma to 2856 Ma, which is similar to that reported from the Atbashi greywacke. Compared with the age spectrum of zircons from Tarim Craton and Atbashi greywacke, the protolith of the muscovite-quartz schist has a depositional age 〈406 Ma and the provenance was probably in the North and Middle Tianshan.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2016年第3期198-209,共12页
Earth Science Frontiers
基金
中国地质调查局地质调查项目'吉尔吉斯天山成矿带成矿地质背景研究及资源潜力评价'(12120115066901)
中-乌合作天山造山带成矿条件与找矿方法示范研究项目(12120115066701)
陕西省自然科学基础研究计划青年人才项目(2015JQ4106)
