吕梁地区古元古代花岗片麻岩成因及变质时代:锆石和独居石U-Pb年龄及锆石Hf同位素证据  

Petrogenesis and metamorphic age of Palaeoproterozoic granitic gneisses in Lüliang area:Constraints from zircon and monazite U-Pb ages and Hf isotopes

作　　者：胡国辉[1,2] 周艳艳 张拴宏[1,2] 王伟[1] 赵太平 王世炎[5] HU GuoHui;ZHOU YanYan;ZHANG ShuanHong;WANG Wei-(RZ);ZHAO TaiPing;WANG ShiYan(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 512640,China;Henan Institute of Geological Survey,Zhengzhou 450001,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部古地磁与古构造重建重点实验室,北京100081 [3]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [4]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [5]河南省地质调查院,郑州450001

出　　处：《岩石学报》2020年第12期3631-3653,共23页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41602202、41725011、41572176)资助。

摘　　要：吕梁地区在华北克拉通前寒武纪研究中具有重要位置,出露大量的古元古代变质表壳岩和花岗质岩石,对研究华北克拉通古元古代地质演化历史具有重要意义。本次研究选择吕梁地区白家滩花岗片麻岩进行锆石和独居石U-Pb年代学以及锆石Hf同位素研究,2个花岗片麻岩的岩浆锆石U-Pb年龄分别为2182±16Ma和2185±24Ma,代表了其侵位时代。独居石U-Pb年龄分别为1898±7Ma和1899±14Ma,明显比锆石增生边的谐和207Pb/206Pb年龄(2180~2032Ma)年轻,说明独居石对后期变质作用的响应程度比锆石强,其U-Pb年龄更能反映白家滩花岗片麻岩经历了~1900Ma的退变质作用,与华北克拉通中部造山带的变质作用时间一致。花岗片麻岩的锆石Hf同位素亏损地幔模式年龄(tDM)为2473~2598Ma,两阶段亏损地幔模式年龄(tDM C)分别为2646~2839Ma,εHf(t)值分布于-1.3^+1.8之间,未显示同期幔源物质的加入,而是新太古代地壳物质部分熔融的产物,结合已有的古元古代中期(2.2~2.1Ga)的岩浆岩锆石Hf同位素数据,华北克拉通新太古代地壳在2.2~2.1Ga期间发生了广泛的重熔作用,这期岩浆活动在华北克拉通吕梁、中条、五台以及胶-辽-吉等地区广泛发育,可能形成于陆内裂谷环境。The Lüliang area,occupying an important position in the Precambrian research on the North China Craton(NCC),developed extensive Palaeoproterozoic metamorphic supracrustal rocks and granitic rocks.It is of great significance to study the paleoproterozoic geological evolution of the NCC.This paper presents zircon and monazite U-Pb ages and zircon Hf isotopes of Palaeoproterozoic Baijiatan granitic gneisses in the Lüliang area.Two granitic gneiss samples obtain LA-ICP-MS zircon U-Pb ages of2182±16 Ma and 2185±24 Ma,respectively,representing their emplacement ages.New LA-ICP-MS dating of monazites from two samples yielded U-Pb ages of 1898±7 Ma and 1899±14 Ma,respectively,which are much younger than the concordant207 Pb/206 Pb ages(2180~2032 Ma)of zircon overgrowth rims.It indicates that monazites thoroughly suffered from the late metamorphism and their U-Pb ages showed the granitic gneiss underwent^1900 Ma metamorphism,which is synchronous with the metamorphic age of the Central Zone of the NCC.Zircon depleted mantle model ages are 2473~2598 Ma and two-stage model ages are 2646~2839 Ma,which are distinctively older than the zircon U-Pb ages.ZirconεHf(t)values are-1.2^+1.8 and-1.3^+1.4,respectively,suggesting the granitic gneiss were originated from partial melting of the late Archean crustal materials,without any mantle-derived materials input.Combined with the available zircon Hf isotopic data from middle Palaeoproterozoic(2.2~2.1 Ga)magmatic rocks,the Late Archean crust of the NCC suffered from extensive remelting effect during 2.2~2.1 Ga.The 2.2~2.1 Ga magmatic activity widely distributed in the Lüliang,Zhongtiao,Wutai and Jiao-Liao-Ji areas and elsewhere in the NCC,which may develop in an intracontinental rift setting.

关 键 词：华北克拉通 吕梁地区 古元古代 花岗片麻岩 锆石和独居石U-Pb年龄 

分 类 号：P588.345[天文地球—岩石学] P597.3[天文地球—地质学]