燕辽裂陷槽基底陆壳生长事件——来自长城系碎屑锆石U-Pb年龄和Lu—Hf同位素的启示  

Crustal growth of the Yanliao intracontinental rift basement---insights from U-Pb ages and Lu-Hf isotopes of the detrital zircon from Mesoproterozoic Changcheng System

作　　者：李文奇 刘汇川 刘小平[1,2] 于志琪 王艺壬 王莹莹 LI Wenqi;LIU Huichuan;LIU Xiaoping;YU Zhiqi;WANG Yiren;WANG Yingying(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing,102249;College of Geosciences,China University of Petroleum(Beijing),Beijing,102249)

机构地区：[1]油气资源与探测国家重点实验室,中国石油大学(北京),北京102249 [2]中国石油大学(北京)地球科学学院,北京102249

出　　处：《地质论评》2024年第4期1335-1352,共18页Geological Review

基　　金：中石油科技创新基金“磷酸盐矿物原位U-Pb测定含油气盆地油气成藏期次”项目(编号:2021DQ02-0103);国家重点研发计划项目“富氦天然气成藏机制及氦资源分布预测技术”(编号:2021YFA0719000);中国石油勘探开发研究院开放基金课题(编号:2022-KFKT-07)的成果。

摘　　要：华北克拉通大陆地壳生长已有大量研究,但对于被巨厚沉积盖层覆盖的燕辽裂陷槽基底地壳生长的问题前人讨论较少。笔者等以燕辽裂陷槽基底之上的长城系沉积岩为研究对象,统计了燕辽裂陷槽内长城系地层中碎屑锆石年龄频谱和Lu—Hf同位素数据,探讨长城系地层沉积年龄、碎屑锆石沉积源区和地壳生长事件等科学问题。同位素年龄将燕辽裂陷槽长城系沉积年龄约束为1680 Ma,代表着燕辽裂陷槽的开启时间。燕辽裂陷槽长城系碎屑锆石年龄频谱主要显示为2.7~2.5 Ga和2.2~1.9 Ga两个阶段,Hf同位素ε_(Hf)(t)表现为高的正值区间0.1~34.6。通过对比长城系碎屑锆石与华北克拉通结晶基底的U-Pb定年、Lu—Hf同位素ε_(Hf)(t)和T_(DM2)模式年龄数据,推测燕辽裂陷槽长城系沉积物源为燕辽裂陷槽下伏基底。结合碎屑锆石U-Pb定年、ε_(Hf)(t)值和T_(DM2)模式年龄数据,我们认为燕辽裂陷槽下伏基底中元古代前地壳生长有3个峰值,分别为2.7~2.5 Ga,2.2~1.9 Ga和1.7~1.6 Ga。Objectives:The North China Craton stands as one of the most ancient cratons worldwide,with its continental crust undergoing multiple episodes of crustal growth events.Considerable research has been conducted on the growth of the continental crust in the North China Craton.However,previous discussions on the crustal growth of basement beneath the Yanliao Rift Basin,obscured by extensive deposits of thick sedimentary cover,have been relatively scarce.Methods:Taking the sedimentary rocks of the Mesoproterozoic Changcheng System above the basement of the Yanliao Rift Basin as example,this study systematically analyzes the detrital zircon age spectra and Lu-Hf isotope data from the Changcheng System strata within the Yanliao Rift Basin.The investigation aims to elucidate scientific inquiries concerning the sedimentary age of the Changcheng Formation,the provenance of detrital zircons and crustal growth events.Results:The isotopic ages constrain the sedimentary age of the Changcheng System in the Yanliao Rift Basin as ca.1680 Ma,which represent the timing of initiation of the Yanliao Rift.The detrital zircon age spectrum from the Changcheng System in the Yanliao Rift Basin primarily exhibits two stages:2.7~2.5 Ga and 2.2~1.9 Ga.The Hf isotopeε_(Hf)(t)values manifest in a high positive range of 0.1 to 34.6.By comparing the detrital zircon U-Pb dating,Lu-Hf isotopeε_(Hf)(t),and T_(DM2) model age data of the Changcheng System with the crystalline basement of the North China Craton,it is inferred that the sediment source of the Changcheng System in the Yanliao Rift Basin is the underlying basement of the Yanliao Rift Basin.Conclusions:①The detrital zircon age spectrum of the Changcheng System in the Yanliao Rift Basin defines two major age populations two main stages:2.7~2.5 Ga and 2.2~1.9 Ga.The Hf isotopeε_(Hf)(t)values exhibit a high positive range between 0.1 and 34.6.②Combining zircon U-Pb dating,zircon Lu-Hf isotopeε_(Hf)(t)and T_(DM2) model age,it is suggested that there are three distinct episodes of crusta

关 键 词：燕辽裂陷槽 长城系 长城群 碎屑锆石 U-Pb年龄 Lu—Hf同位素 陆壳生长 

分 类 号：P597[天文地球—地球化学]