共和盆地河流碎屑锆石U-Pb年龄特征、Hf同位素组成及其对构造和地壳演化的启示  

Zircon U-Pb ages and Hf isotopic compositions of river sediments from the Gonghe Basin and implication on tectonics and evolution of the crust

作　　者：艾尼卡尔·艾克帕尔 陈岳龙[1] 梁乾坤 康欢 ANKAR Akbar;CHEN Yuelong;LIANG Qiankun;KANG Huan(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地震局地质研究所地震动力学国家重点实验室,北京100029

出　　处：《地质通报》2024年第6期1004-1020,共17页Geological Bulletin of China

基　　金：国家自然科学基金项目《祁连造山带中河流沉积物地球化学及其锆石U-Pb年龄与Hf同位素组成》(批准号:41473015)。

摘　　要：为揭示青海共和盆地沉积源区构造活动和地壳演化历史,应用LA-MC-ICP-MS技术,对共和盆地曲什安河与西河河漫滩沉积物中的碎屑锆石进行了U-Pb定年和Hf同位素分析。得出碎屑锆石U-Pb年龄可分为5组:309~172 Ma、471~368 Ma、943~737 Ma、2368~1698 Ma、2543~2453 Ma。结合研究区构造-岩浆事件得出,曲什安河与西河河漫滩碎屑沉积物是西秦岭地块在不同时期提供的结果。碎屑锆石U-Pb年龄存在2个主要峰值,约236 Ma和约403 Ma,反映了古特提斯洋和原特提斯洋在不同部分的俯冲导致陆块碰撞,形成强烈岩浆事件的地质记录,碰撞后伸展阶段出现裂谷和新生洋盆。Hf同位素组成特征揭示,源区地壳在2.7~1.3 Ga经历了主要增生期,形成现今地壳的84%。ε_(Hf)(t)值为-14.7~+15.0,Hf亏损模式年龄在3.6~0.24Ga范围内,表明源区基底存在古太古代古老地壳物质。约0.5 Ga以来,地壳增长以古老地壳物质再循环为主,并在0.28 Ga左右地壳停止了生长。依据前人公式计算了曲什安河与西河河漫滩碎屑沉积物物源区各时期的重熔/增生比例。To reveal the history of tectonic activity and crustal evolution in the sedimentary source area of the Gonghe Basin,U-Pb dating and Hf isotope analysis of detrital zircons in the floodplain sediments of the Qushian river and Xi river in the Gonghe Basin were analyzed by LA-MC-ICP-MS approach in this study.It was revealed that the U-Pb age of these detrital zircons can be divided into 5 groups:309~172 Ma,471~368 Ma,943~737 Ma,2368~1698 Ma,2543~2453 Ma.According to the tectonic-magmatic events in the study area,it is concluded that the detrital sediments of the floodplains of the Qushian River and Xi River are provided by the Western Qinling block at different times.There are two main detrital zircon U-Pb ages,236 Ma and 403 Ma,reflecting the geological record of the collision of blocks in different parts of the paleo and proto-Tethys oceans,induced strong magmatic events,and the emergence of rift valleys and neonatal ocean basins in the post-collision extension stage.The features of Hf isotopic composition revealed that the crust in the source area underwent a major accretion period at 2.7~1.3 Ga,and created 84%of the current crust.ε_(Hf)(t)value ranges between-14.7 and+15.0,Hf depleted mode age in the range of 3.6~0.24 Ga,indicating the presence of Paleoarchean ancient crust substance in the source area substrata.Since 0.5 Ga,the growth of the earth's crust has mainly been dominated by the recycling of ancient crust substance,and the growth of the crust has stopped at 0.28 Ga.Furthermore,using formula of recycling ratio,ratios between remelting and juvenile crust with age have been calculated.

关 键 词：共和盆地 碎屑锆石 U-Pb年龄 LU-HF同位素 大陆地壳生长 

分 类 号：P597.3[天文地球—地球化学]