藏北羌塘盆地基底的地质构造演化:来自侏罗纪雁石坪群砂岩碎屑锆石U-Pb同位素年代学证据  

Geological and tectonic evolution of the basement in the Qiangtang basin of northern Tibet:Evidence from detrital zircon U-Pb isotope chronology of sandstone in the Jurassic Yanshipin Group

作　　者：李江涛[1,2] 梁斌[1,2] 何文劲 徐刚 文龙[1,2] 谢启兴 

机构地区：[1]西南科技大学环境与资源学院,四川绵阳621010 [2]四川省地勘局川西北地质队,四川绵阳621010

出　　处：《中国地质》2016年第4期1216-1226,共11页Geology in China

基　　金：中国地质调查局"青海龙亚拉地区1:5万区域地质调查"项目(121201122019);国家自然科学基金(41472310)联合资助~~

摘　　要：羌塘盆地作为青藏高原面积最大的中—新生代盆地,是揭示特提斯域演化的关键区域,其构造属性与演化历史备受关注。然而,长期以来对于盆地是否具有前寒武纪结晶基底以及其地质构造演化等问题一直存分歧。雁石坪群作为羌塘盆地分布最广,地层出露最全的一套侏罗纪地层,其碎屑沉积物中包含了大量关于羌塘盆地地质构造演化的重要信息。为此笔者选择位于羌塘盆地东部唐古拉山北麓温泉地区雁石坪群砂岩进行碎屑锆石LA-ICPMS U-Pb年代学研究,以期为解决羌塘盆地基底的地质构造演化提供依据。8件砂岩样品429个有效测试点的年龄结果显示,雁石坪群碎屑锆石的年龄时间跨度大,自新太古代至中侏罗世晚期（2668~166 Ma）,具有明显的阶段性,可分为10个年龄组。结合区域地质特征,对年龄值大于486 Ma碎屑锆石年龄组进行了重点分析探讨,认为羌塘盆地具有前寒武纪结晶基底,其形成的主要时期为1974~1666 Ma,且结晶基底还遭受了后期地质构造作用的改造,先后经历了与Columbia超级大陆、Rodinia超大陆演化相关的构造热事件、格林威尔—晋宁构造岩浆运动、泛非运动等一系列地质构造演化,支持了羌塘地块属冈瓦纳大陆的认识。As the largest Mesozoic- Cenozoic basin in the Tibetan Plateau, the Qiangtang Basin is the key area to reveal theevolution of Tethys, and hence its structure and evolution have aroused much interest. However, for a long time the problemsconcerning the existence or nonexistence of the pre-Cambrian basement in the Qiangtang Basin and its tectonic evolution have beentopics of much controversy. Yanshiping Group is the most widely distributed strata which have the most complete set of Jurassic inthe Qiangtang Basin,and its detrital sediments contain a lot of important information concerning the tectonic evolution of theQiangtang Basin. The authors hence selected the sandstone from Yanshiping Group in the east of the Qiangtang Basin, the northernfoot of the Tanggula Range in the Wenquan region to perform LA-ICP-MS U-Pb dating so as to provide an important basis forsolving tectonic evolution about the basement in the Qiangtang basin. The ages of 429 valid test points from 8 sandstone samplesshow that the formation of detrital zircons from Yanshiping Group spanned a long period, and the ages of zircons range from NewArchean to Late Middle Jurassic （2668-166 Ma）, which have evident stage characteristics and can be divided into ten age groups. Incombination with regional geology, the authors discussed and analyzed detrital zircon whose ages are greater than 486 Ma. It is heldthat the Qiangtang Basin has Pre-Cambrian basement, the main period of its formation is approximately 1974-1666 Ma, and thePre- Cambrian basement also suffered from the post- tectonic reformation, and experienced the tectonic thermal events of theColumbia and Rodinia supercontinent, Greenville-Jinning tectonic movement of magma, Pan-African movement and a series oftectonic evolution. The results obtained by the authors support the opinion that the Qiangtang terrane belongs to the Gondwana.

关 键 词：羌塘盆地 雁石坪群 碎屑锆石 LA-ICP-MS U-PB测年 基底 

分 类 号：P597.3[天文地球—地球化学] P588.21[天文地球—地质学]