鲁西地区新太古代地壳增生事件--来自花岗岩和二长花岗岩 U-Pb年代学、Hf同位素和岩石地球化学的证据  

Neoarchean Crustal Accretion in Western Shandong Province:Evidence from Granite and Monzogranite U-Pb Chronology,Hf Isotope and Rock Geochemistry

作　　者：王跃 周奇明 张金龙[3] 周光峰 Wang Yue;Zhou Qiming;Zhang Jinlong;Zhou Guangfeng(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;China Nonferrous Metals(Guilin)Geology and Mining Co.,Ltd.,Guilin541004,Guangxi,China;Shixi Oilfield Operation Area,Xinjiang Oilfield Company,Karamay 834000,Xinjiang,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]中国有色桂林矿产地质研究院有限公司,广西桂林541004 [3]新疆油田公司石西油田作业区,新疆克拉玛依834000

出　　处：《吉林大学学报（地球科学版）》2022年第2期463-485,共23页Journal of Jilin University：Earth Science Edition

基　　金：国家重点研发计划项目(2016YFC0600608)。

摘　　要：鲁西地区是全球完整保存新太古代早期TTG(英云闪长岩奥长花岗岩花岗闪长岩)和绿岩带的区域,是研究太古宙岩浆演化类型和太古宙时期壳幔作用以及构造模式的典型区域.本文在野外地质调查的基础上,通过年代学、Hf同位素和岩石地球化学等手段,探讨了鲁西地区新太古代花岗岩和二长花岗岩的地球化学特征和形成背景.鲁西地区新太古代花岗岩和二长花岗岩U Pb年龄主要为2537和2566Ma.花岗岩(TA1802)εHf(t)值为-1.4~2.9,平均值为0.65,二阶段模式年龄约为2.9Ga;二长花岗岩(TA1812)εHf(t)值为-0.4~2.7,平均值为1.31,二阶段模式年龄为3073~2886 Ma,平均值约为2.9Ga;二长花岗岩(TA1817)εHf(t)值为0.3~4.7,平均值为3.35,二阶段模式年龄为3032~2762Ma,平均值约为2.8Ga.在εHf(t)t图解上,鲁西地区新太古代花岗岩和二长花岗岩年龄演化线均落在2.9~2.8Ga地壳演化线上,且与二阶段模式年龄大致相同,即表明鲁西地区新太古代花岗岩和二长花岗岩源于2.9~2.8Ga的古老地壳重融.鲁西地区新太古代花岗岩和二长花岗岩均表现为高w(SiO2)、w(Al2O3)和富Na2O特征,大部分属于准铝质岩石.稀土元素球粒陨石标准化分布型式上,均表现为轻稀土元素(LREE)富集和重稀土元素(HREE)亏损,且中重稀土元素出现分馏.花岗岩样品中,有两个样品(TA18011与TA1824)表现出Ta富集,其余样品均表现为K、Rb、Ba和Th等大离子亲石元素富集,Nb、Ta、Ti亏损.二长花岗岩也同样表现为K、Rb、Ba和Th等大离子亲石元素富集,Nb、Ta、Ti亏损,部分熔融残余矿物存在石榴石、金红石以及少量斜长石、角闪石.根据上述地球化学特征,并结合区域地质特征,鲁西地区新太古代花岗岩和二长花岗岩构造背景为同碰撞背景,该构造模式是大陆地壳有效增生.Western Luxi is the only area in the world where the Early Neoarchean TTG and greenstone belts are completely preserved,which are typical for study the evolution types of Archean magma,the crust-mantle interaction,and the Archean tectonic model.Based on field geological surveys,in this paper,the geochemical characteristics and formation background of the Neoarchean granites and monzonites in western Shandong s are discussed by means of trace element geochemistry,isotope geochemistry,and isotope chronology.The U-Pb ages of Neoarchean granites and monzonite granites in western Luxi are mainly 2537 Ma and 2566 Ma.The granite(TA1802)εHf(t)value is-1.4-2.9(average 0.65),and the two-stage model age is about 2.9 Ga;The monzonite granite(TA1812)εHf(t)value is-0.4-2.7(average 1.31),the age of two-stage model is 3073-2886 Ma(average 2.8 Ga),the monzonite granite(TA1817)εHf(t)is 0.3-4.7,the average is 3.35,the age of the second-stage model is 3032-2762 Ma,the average is about 2.8 Ga.On theεHf(t)-t diagram,the age evolution lines of the Neoarchean granites and monzonites in Luxi fall on the 2.9-2.8 Ga crustal evolution line,and are roughly the same as that of the second-stage model,which indicates that the Luxi Neoarchean granites and monzonites originated from the re-melting of the ancient crust at 2.9-2.8 Ga.The Neoarchean granites and monzonites in western Shandong are characterized by high w(SiO2),w(Al2O3),and w(Na2O),and they are all quasi-aluminum rocks.In the standardized distribution pattern of rare earth element chondrites,they all show light rare earth element(LREE)enrichment,heavy rare earth element(HREE)depletion,and medium-heavy rare earth element fractionation.There are two samples(TA1801-1 and TA1824)showing Ta enrichment and the rest samples showing large ion lithophile element enrichment,such as K,Rb,Ba and Th,and Nb,Ta,and Ti depletion.The monzonites also show the enrichment of large ion lithophile element such as K,Rb,Ba and Th,the depletion of Nb,Ta,Ti,and the partial molten residual minerals include

关 键 词：鲁西 新太古代 花岗岩类 地球化学 U Pb年代学 Lu Hf同位素 同碰撞 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]