阴山地块固阳地区新太古代TTG片麻岩成因及构造意义:锆石U-Pb年代学、地球化学和Lu-Hf同位素约束  

Zircon U-Pb-Hf isotopes and geochemistry of Neoarchean TTG gneisses in the Guyang area of the Yinshan Block:Constraints on petrogenesis and tectonic implications

作　　者：赵辰 王笑 刘锦[4] 张健[3] 陈井胜[1,2] 张超 崔丹丹[1,2] 崔育菘 ZHAO Chen;WANG Xiao;LIU Jin;ZHANG Jian;CHEN JingSheng;ZHANG Chao;CUI DanDan;CUI YuSong(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Northeast Geological S&T Innovation Center of China Geological Survey,Shenyang 110034,China;Department of Earth Sciences,The University of Hong Kong,Hong Kong,China;College of Earth Sciences,Jilin University,Changchun 130061,China;Liaoning Geological and Mineral Survey Institute Co.Ltd.,Shenyang 110000,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]东北地质科技创新中心,沈阳110034 [3]香港大学地球科学系,中国香港 [4]吉林大学地球科学学院,长春130061 [5]辽宁省地质矿产调查院有限责任公司,沈阳110000

出　　处：《岩石学报》2024年第11期3465-3483,共19页Acta Petrologica Sinica

基　　金：中国地质调查局基础地质调查项目(DD20242927);国家自然科学基金项目(42302221、42025204、41890381);国家重点研发计划(2023YFF0803804)联合资助.

摘　　要：作为太古宙基底保存较完整的地区,华北克拉通阴山地块出露大量的新太古代岩石组合,主要包括表壳岩、TTG片麻岩(英云闪长质片麻岩-奥长花岗质片麻岩-花岗闪长质片麻岩)、钾质花岗岩和闪长岩(赞岐岩)等。前人对阴山地块新太古代TTG片麻岩开展了一系列的工作,但有关其岩石成因、构造背景以及新太古代地壳生长机制仍然存在较大争议。本次工作在内蒙古固阳西部的花岗-绿岩带中新识别出一套TTG片麻岩组合,并对其进行了岩石学、同位素年代学和岩石地球化学的综合研究。LA-ICP-MS锆石U-Pb定年结果显示TTG片麻岩组合形成时代为2550~2524Ma;Lu-Hf同位素分析结果显示其εHf(t)值为+0.54~+4.96,t C DM模式年龄为2985~2715Ma,这与阴山地块目前最古老的奥长花岗质片麻岩(2.7Ga)的岩浆年龄近一致,说明其可能来源于2.7Ga新生镁铁质地壳的部分熔融。全岩地球化学分析结果显示,该TTG片麻岩组合具有较高的SiO 2(63.32%~70.80%)和Al 2O 3(15.19%~16.55%)含量,以及较高的Sr(410×10^(-6)~1532×10^(-6))和较低的Y(2.61×10^(-6)~14.04×10^(-6))含量,同时具有相对较高的(La/Yb)N(10.31~56.85)和Sr/Y(44.32~349.1)比值,并相对富集轻稀土元素(LREEs)和大离子亲石元素(LILEs),这些均与典型的埃达克质岩石地球化学特征相似。另外,该TTG片麻岩样品具有相对较低的MgO(0.60%~2.60%)、Ni(3.12×10^(-6)~11.12×10^(-6))、Cr(3.77×10^(-6)~18.11×10^(-6))含量和Mg#(34.88~53.45),说明其来源于加厚的大陆下地壳埃达克质岩浆。因此,本文认为在2.55~2.52Ga,固阳新太古代TTG片麻岩可能由加厚的镁铁质下地壳部分熔融形成的。结合前人的研究结果,进一步推断阴山地块在新太古代可能经历两期岩浆事件:第一期岩浆事件发生在2.7Ga,形成加厚的镁铁质地壳和少量的~2.7Ga TTG岩石;第二期岩浆事件发生在2.55~2.50Ga,形成阴山地块大面积的新太古代TTG岩石和其他花岗�As a well-preserved Archean basement,the Yinshan Block in North China Craton preserved large numbers of Neoarchean rock assemblages,including the supracrustal rocks,tonalitic-trondhjemitic-granodioritic gneisses(TTG gneisses),K-rich granitoids and diorites(sanukitoids).Previous studies have been carried out on the Neoarchean TTG gneisses in this block,but the petrogenesis and tectonic implications of the TTG gneisses are still controversial,which greatly hinders the understanding of the formation and evolution of the Neoarchean continental crust in this region.In this study,a new TTG gneiss assemblage has been identified in the granite-greenstone belt of western Guyang,Inner Mongolia,and its petrology,geochronology and petrogeochemistry have been studied.The LA-ICP-MS zircon U-Pb dating results indicate that the formation age of the TTG gneiss assemblage is 2550~2524Ma;while the Lu-Hf isotope analysis results show anεHf(t)value ranging from+0.54 to+4.96,and a t C DM model age ranging from 2985Ma to 2715Ma.These ages are similar to the magmatic age(2.7Ga)of the oldest trondhjemite gneiss in the Yinshan Block,suggesting that they may have originated from partial melting of a newly formed mafic crust at 2.7Ga.The whole-rock geochemical analysis results show that the TTG gneiss assemblage has high SiO 2(63.32%~70.80%)and Al 2O 3(15.19%~16.55%)contents,as well as high Sr(410×10^(-6)~1532×10^(-6))and low Y(2.61×10^(-6)~14.04×10^(-6))contents with relatively high(La/Yb)N(10.31~56.85)and Sr/Y(44.32~349.1)ratios.The light rare earth elements(LREEs)and Large-ion Lithophile Elements(LILEs)of the gneiss are relatively enriched,which are similar to the geochemical characteristics of the typical adakitic rocks.In addition,the TTG gneiss assemblage has relatively low MgO(0.60%~2.60%),Ni(3.12×10^(-6)~11.12×10^(-6)),Cr(3.77×10^(-6)~18.11×10^(-6))contents and Mg#(34.88~53.45),indicating that it is originated from the adakitic magma of a thickened continental crust.Therefore,the Neoarchean TTG gneisses from Guyang area may

关 键 词：华北克拉通 阴山地块 埃达克质岩石 TTG片麻岩 地幔柱 

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