胶北地区粉子山群碎屑锆石U-Pb年龄、Hf同位素及其对胶-辽-吉带构造演化的制约  

Detrital zircon U-Pb geochronology and Hf isotopes of the Fenzishan Group,Jiaobei Terrane:Implications for the Paleoproterozoic tectonic evolution of the Jiao-Liao-Ji belt

作　　者：陶鹏 谢士稳[2] 王舫[2] 刘倩 李强 高嘉敏 龙涛[2] TAO Peng;XIE ShiWen;WANG Fang;LIU Qian;LI Qiang;GAO JiaMin;LONG Tao(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Shandong Provincial No.4 Institute of Geological and Mineral Survey,Weifang 261021,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]中国地质科学院地质研究所,北京100037 [3]山东省第四地质矿产勘查院,潍坊261021

出　　处：《岩石学报》2023年第9期2619-2635,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41402167、41890833);中国地质科学院基本科研业务费专项经费(JKYQN202312);中国地质科学院地质研究所基本科研业务费(J1712、J2009、J2102)联合资助.

摘　　要：胶北地区粉子山群和荆山群是胶-辽-吉带重要的组成部分,对粉子山群和荆山群中碎屑锆石的年龄分布和Hf同位素特征的研究,有助于深入认识胶-辽-吉带古元古代构造演化过程。对粉子山群小宋组、张格庄组和巨屯组中碎屑锆石U-Pb定年结果表明,其锆石谐和年龄分布在1842~3663Ma之间,其中13颗锆石的变质边给出了1842~1877Ma的变质年龄,指示粉子山群经历了古元古代晚期变质作用,与荆山群变质作用时代一致。本次研究的三个组中都存在2.2~2.1Ga的碎屑锆石,结合前人研究成果,粉子山群主体应沉积于2.1~1.9Ga。粉子山群碎屑锆石的年龄峰和εHf(t)值与胶北地区早前寒武纪岩浆岩基本一致,表明其碎屑物质很有可能来自胶北地体。另外在巨屯组样品中发现约17%的新太古代晚期碎屑锆石具有明显偏低的εHf(t)值(-5.79~-2.44),可能由早期岩浆岩部分熔融而成,这也暗示胶北~2.5Ga不仅发生大规模的初生地壳生长,还存在早期地壳的重熔。粉子山群和荆山群碎屑锆石年龄分布特征基本一致,均含有胶北特征的年龄峰(~2.7Ga和~2.9Ga),结合二者空间分布特征、一致的变质作用时代以及顺时针的P-T-t轨迹,本文认为粉子山群和荆山群可能均沉积于胶北地体一侧,并随胶北地体向东南俯冲。The Fenzishan and Jingshan groups in the Jiaobei Terrane are important components of the Paleoproterozoic Jiao-Liao-Ji belt.The study of the age histograms and Hf isotopic characteristics of detrital zircons from these two groups will provide great help for understanding of the tectonic evolution of the Jiao-Liao-Ji belt.The U-Pb dating on the detrital zircons and their metamorphic rims in the Xiaosong,Zhanggezhuang and Jutun formations of the Fenzishan Group obtained concordant zircon ages within the range of 1842~3663Ma.Thirteen zircon rims have ages of 1842~1877Ma,indicating that the Fenzishan Group underwent a Late Paleoproterozoic metamorphism,which is consistent with that of the Jingshan Group.The detrital zircons in all the three formations have the ages of 2.2~2.1Ga.Combined with early studies,the main body of the Fenzishan Group should be deposited at 2.1~1.9Ga.The age peaks andεHf(t)values of detrital zircons from the Fenzishan Group are basically consistent with the Early Precambrian magmatic rocks in the Jiaobei Terrane,indicating that its detrital materials are most likely to be originated from this terrain.In addition,about 17%of~2.5Ga detrital zircons from the Jutun Formation samples have obviously lowεHf(t)values(-5.79~-2.44),which may be formed by partial melting of early magmatic rocks,suggesting that not only large-scale primary crustal growth but also early crustal remelting occurred in the Late Neoarchean in the Jiaobei Terrane.The age distributions of detrital zircons from the Fenzishan and Jingshan groups are basically identical to each other,and both of them contain typical age peaks of Jiaobei Terrane(~2.7Ga and~2.9Ga).In combination with their spatial distribution relationships,the identical metamorphic ages and clockwise P-T-t trajectories,it can be concluded that both the Fenzishan and Jingshan groups were probably deposited on the same side of the Jiaobei Terrane and subducted southeastward with this terrane afterwards.

关 键 词：胶-辽-吉带 古元古代 胶北地体 粉子山群 碎屑锆石 

分 类 号：P588.3[天文地球—岩石学] P597.3[天文地球—地质学]