辽北新太古代晚期岩浆热事件与陆壳生长:来自清原奥长花岗岩的锆石U-Pb年代学和岩石地球化学证据  

Late Neoarchean magmatism and crustal growth in northern Liaoning: Evidence from zircon U-Pb geochronology and petro-geochemistry of the Qingyuan trondhjemites

作　　者：袁玲玲 刘洁[1] 张晓晖 杨智荔[2,4] 张航 李宏斌 YUAN LingLing;LIU Jie;ZHANG XiaoHui;YANG ZhiLi;ZHANG Hang;LI HongBin(MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,School of Geoscience and Info-physics,Central South University,Changsha 410083,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy for Earth Sciences,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中南大学地球科学与信息物理学院,有色金属成矿预测与地质环境监测教育部重点实验室,长沙410083 [2]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 [3]中国科学院地球科学研究院,北京100029 [4]中国科学院大学,北京100049

出　　处：《岩石学报》2020年第2期333-355,共23页Acta Petrologica Sinica

基　　金：国家自然科学基金面上项目(41573031);青年科学基金项目(41903030);中南大学中央高校基本科研业务费专项资金(1053320190076)联合资助

摘　　要：TTG(英云闪长岩-奥长花岗岩-花岗闪长岩)片麻岩是太古宙陆壳的重要组成部分,探究其形成过程可以获得地球早期大陆地壳增生-演化的关键地球动力学信息。本次研究从华北克拉通东部辽北清原地体中识别出了柴河、摩离红两个奥长花岗岩岩株,在空间上它们与时代相近的赞岐岩类(石英二长闪长岩)伴生,SIMS锆石U-Pb定年指示二者结晶年龄和变质年龄分别为2550~2546Ma和2510~2480Ma。柴河岩体SiO2含量介于70.7%~73.5%之间,Na2O/K2O比值为2.15~4.89,Al2O3含量为14.3%~15.5%;富集Rb、Ba、Sr等大离子亲石元素(Sr=356×10^-6~464×10^-6,Sr/Y=71~392),亏损Nb、Ta和Ti等高场强元素,轻重稀土强烈分异,(La/Yb)N比值介于45~144之间,部分样品发育Eu正异常(δEu=1.17~2.41)。摩离红岩体SiO2含量为64.7%~75.7%,Na2O/K2O比值为1.86~2.78,Al2O3变化范围较大(13.7%~17.7%);同样富集大离子亲石元素并亏损高场强元素,Sr/Y比值为22~36,轻重稀土分异明显,具有中等至偏高的(La/Yb)N比值(7~47),Eu异常发育不明显(δEu=0.86~1.34)。二者均具有接近亏损地幔的全岩εNd(t)(+1.9^+3.8)和锆石εHf(t)(+3.9^+7.1)值。以上特征指示柴河、摩离红岩体可能分别形成于低角度俯冲大洋板片或岛弧下地壳在榴辉岩相和石榴角闪岩相条件下部分熔融。区域岩浆-变质事件的时-空分布关系表明,华北克拉通东部新太古代晚期热事件主要受控于初始板块构造体制下的短周期、小规模俯冲-碰撞-伸展造山旋回。俯冲带岩浆活动在新太古代晚期陆壳生长-分异过程中已经扮演着非常重要的角色。The TTG(tonalite-trondhjemite-granodiorite)gneisses constitute important components of Archean continental crust and their genesis harbors a key to ascertaining critical geodynamic controls on continental crustal formation and differentiation.This geochronological and geochemical study documents two trondhjemite plutons from the Qingyuan area of northern Liaoning,eastern North China Craton(NCC).Spatially associated with near-coeval sanukitoids(quartz monzodiorites),these trondhjemites are emplaced at 2550~2546Ma and metamorphosed at 2510~2480Ma.The Chaihe pluton possesses SiO2 contents of 70.7%~73.5%,Al2O3 contents of 14.3%~15.5%and Na2O/K2O ratios of 2.15~4.89,and shows enrichment of large ion lithophile elements(LILEs,e.g.,Rb,Ba,Sr),depletion of high field strength elements(HFSEs,e.g.,Nb,Ta and Ti)with high Sr/Y(71~392)and(La/Yb)N(45~144)ratios and weakly positive Eu anomalies(δEu=0.89~2.41).The Molihong pluton exhibits SiO2 abundances of 64.7%~75.7%,Al2O3 contents of 13.7%~17.7%and Na2O/K2O ratios of 1.86~2.78,and also displays decoupled trace element and rare earth element patterns,with moderate to high Sr/Y(22~36)and(La/Yb)N(7~47)ratios and minor Eu anomalies(δEu=0.86~1.34).Both plutons have whole-rockεNd(t)(+1.9^+3.8)and zirconεHf(t)(+3.9^+7.1)values close to those of depleted mantle.These features suggest that the Chaihe and Molihong plutons stem from partial melting of low-angle subducted slab or arc lower crust under eclogite and garnet amphibolite facies conditions,respectively.The spatial-temporal distribution of regional magmatic and metamorphic records indicates that the Late Neoarchean thermal events in the eastern NCC were mainly dominated by short-term,small-scale subduction-collision-extension orogenic cycles within pristine plate-tectonic regimes,which might also lead to the initial amalgamation of microcontinental blocks in the NCC.The subduction zone magmatism may have played an important role on continental crustal growth and differentiation since the Late Neoarchean.The recycling or rewo

关 键 词：TTG片麻岩 新太古代晚期 岩石成因 构造环境 华北克拉通东部 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]