青海省格尔木市小南川地区昆南构造混杂岩带的物质组成、LA-ICP-MS锆石U-Pb年龄及其地质意义  

The material composition and LA-ICP-MS zircon U-Pb age of East-Kunlun tectonic melange in Xiaonanchuan area, Golmud City,Qinghai Province,and its geological significance

作　　者：张海迪[1,2] 李荣社[2] 计文化[2] 查显锋[2] 刘银[1,2] 潘术娟[1,2] 时超[1,2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质调查局西安地质矿产研究所,陕西西安710054

出　　处：《地质通报》2012年第1期38-49,共12页Geological Bulletin of China

基　　金：中国地质调查局项目<东昆仑成矿带基础地质综合研究>(编号:1212010040107);国家自然科学基金(国土资源部百人计划)项目<青藏高原冈底斯及其以北地区中上二叠统不整合地质意义研究>(批准号:40872084)

摘　　要：在格尔木以南小南川地区测制了一条近S—N向的剖面。通过详细的野外接触关系、露头地质体组成、变形-变质特征观察,结合室内显微结构研究,在小南川昆南构造混杂岩带识别出6种不同的构造岩片,自北往南依次为含斜长角闪岩透镜体绿片岩岩片、块状大理岩岩片、粉砂质板岩岩片、片理化火山碎屑岩岩片、板理化沉凝灰岩岩片和片岩岩片,岩片之间主要以不同性质的脆性或韧性断层接触。对构造混杂岩中的斜长角闪岩和片理化英安岩中的锆石进行了LA-ICP-MS U-Pb同位素测定,获得的年龄分别为1123Ma±110Ma和499Ma±11Ma。对比分析认为,含斜长角闪岩透镜体绿片岩岩片与块状大理岩岩片应属于中元古代万保沟群,形成于大陆裂谷环境;粉砂质板岩岩片、片理化火山碎屑岩岩片、板理化沉凝灰岩岩片分别为火山弧及与弧相关的弧前-弧后盆地建造;片岩岩片为增生楔内部的物质。昆南构造混杂岩带的物质组成和年代学研究为细化昆南增生杂岩带的增生-就位过程提供了物质基础和时代限定,进而为昆仑造山带乃至青藏高原北缘的构造过程研究提供了依据。Depending on the NS-trending structural section in Xiaonanchuan area of East Kunlun, south of Golmud, the authors have recognized six different tectonic slices based on field detailed contact relationship, composition characteristics, metamorphic-deforma- tion features and microstructures. From north to south, these six tectonic slices are amphibolitic lenses-bearing greenschist, blocky marble, silty slate, foliated pyroclastic rock, platy tuffite and schist, and each of them were bounded by brittle or ductile faults. Zircons in amphibolitic schist and foliated dacite from the tectonic melange belt are dated by LA-ICP-MS U-Pb method and yield weighted ages of 1123 _＋ 110 Ma and 499 ＋ 11 Ma. A comparative analysis shows that amphibolitic lenses-bearing greenschist and blocky mar- ble should be part of Mesoproterozoic Wanbaogou Group and formed in the setting of continental rill Silty slate, foliated pyroclastic rock and platy tuftite are the components of a suite of volcanic arc and arc-related fore-back basins, and schist is the petrologic con- stituent within the accretionary wedge. Petrologic constituent and geochronology of the tectonic melange belt in southern Kunlun can provide the fundamental substance and precise constraints for the establishment of the accretionary complex belt and the process of ac-cretion and emplacement, which may furnish basis to the study of the tectonic progress of the Kunlun orogenic belt and even the northern margin of the Tibetan Plateau.

关 键 词：青海 昆南构造混杂岩 岩片划分 物质组成 LA—ICP—MS锆石U—Pb年龄 

分 类 号：P542[天文地球—构造地质学]