冈瓦纳大陆北缘安第斯型造山带:藏北安多奥陶纪花岗岩锆石U-Pb年龄和地球化学证据  

Andean-type orogeny along the northern Gondwana margin:Evidences of zircon U-Pb ages and geochemistry data of the Ordovician granites from the Amdo area,northern Tibet

作　　者：胡培远[1] 翟庆国[1] 赵国春[2,3] 唐跃 朱志才[1] 王伟 吴昊[1] HU PeiYuan;ZHAI QingGuo;ZHAO GuoChun;TANG Yue;ZHU ZhiCai;WANG Wei;WU Hao(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chiriese Academy of Geological Sciences,Beijing 100037,China;Department of Earth Sciences,University of HongKong,Pokfulam Road,Hong Kong,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China)

机构地区：[1]自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京100037 [2]香港大学地球科学系,中国香港 [3]大陆动力学国家重点实验室,西北大学地质学系,西安710069

出　　处：《岩石学报》2021年第2期530-544,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41872240、42072268);第二次青藏高原综合科学考察(2019QZKK0703);国家重点研发计划“深地资源勘查开采”(2016YFC0600304);中国地质调查局工作项目(DD20190370、DD20190060)联合资助。

摘　　要：随着近年来地质研究程度的提高,青藏高原晚古生代-中生代的板块构造演化过程已经日趋清晰,但是对于青藏高原前寒武纪-早古生代演化历史的认知程度仍然很低。本文报道了青藏高原拉萨地块安多地区花岗岩的LA-ICP-MS锆石UPb定年、岩石地球化学和锆石Hf同位素分析结果。这些花岗岩形成于早奥陶世(481~487Ma),为Ⅰ型花岗岩具有不均一的锆石ε_(Hf)(t)值(-5.8~+0.6),可能形成于壳源和幔源岩浆的混合作用,随后经历了广泛的结晶分异过程。拉萨地块的埃迪卡拉纪-奥陶纪Ⅰ型花岗岩具有Sr/Y比值降低和锆石ε_(Hf)(t)值升高的演化趋势,指示伸展环境下的幔源岩浆上涌过程。综合前人研究成果可知,安多地区奥陶纪花岗岩可能形成于后碰撞环境与早古生代冈瓦纳大陆北缘的洋壳俯冲和陆块拼贴相关。As a result of the improvement of geological research in recent years,the Late Paleozoic-Mesozoic evolution history of the Tibetan Plateau is becoming daily more clearly.However,our knowledge on the Precambrian-Early Paleozoic evolution of the Tibetan Plateau is still insufficient.This paper reports new LA-ICP-MS zircon U-Pb age and Lu-Hf isotope,and whole-rock major and trace element data from the granites located in the Amdo area,Lhasa terrane,Tibetan Plateau.These granites were formed in the Early Ordovician(481~487 Ma),areⅠ-type,with various zirconε_(Hf)(t)values(-5.8 to+0.6),and were probably generated by magma mixing of crust-and mantle-derived magmas and subsequent extensive fractional crystallization.The positive Sr/Y vs.age and negativeε_(Hf)(t)value vs.age correlations of the Ediacaran-Ordovician I-type granites in the Lhasa terrane indicate mantle input in an extensional setting.Integrating previous studies with the data presented in this contribution,we propose that the Ordovician granites in the Amdo area developed in a post-collisional setting as a result of the oceanic subduction and collisional accretion along the northern Gondwana margin.

关 键 词：青藏高原 安多 花岗岩 全岩地球化学 锆石U-PB定年 

分 类 号：P534.42[天文地球—古生物学与地层学] P542[天文地球—地质学]