辽北地区奥长花岗岩锆石U-Pb测年及岩石地球化学特征  

Zircon U-Pb dating and lithogeochemical characteristics of trondhjemite in northern Liaoning

作　　者：鲍东明 余超 马力 田毅 杨新宇 Bao Dongming;Yu Chao;Ma Li;Tian Yi;Yang Xinyu(Liaoning Institute of Geology and Mineral Resources Survey,Shenyang,Liaoning,110031,China)

机构地区：[1]辽宁省地质矿产调查院有限责任公司,辽宁沈阳110031

出　　处：《化工矿产地质》2021年第4期289-296,共8页Geology of Chemical Minerals

摘　　要：辽北奥长花岗岩是华北克拉通北缘东段早前寒武纪变质基底的一部分,通过LA-ICP-MS锆石U-Pb测年结果显示其形成年龄为2553±6Ma,时代为新太古代。地球化学结果显示,岩石具有富SiO_(2)、高Al_(2)O_(3)、富Na_(2)O、贫K_(2)O、低镁值(Mg#=27~40)特征,A/CNK值1.08~1.16;岩石显示奥长花岗岩演化趋势为弱过铝质I型花岗岩,并具有埃达克岩和新太古代富铝型TTG岩石特征;岩石ΣREE偏低,稀土元素显示强烈分异,Eu正异常,富集Rb、Ba、K等大离子亲石元素,亏损Ta、Nb、Ti、P等高场强元素,显示弧岩浆特征。综合研究表明,辽北地区在新太古代晚期为俯冲作用相关的构造背景,是华北克拉通新太古代弧陆碰撞增生型造山带的重要组成部分。Northern Liaoning trondhjemite is a part of the early Precambrian metamorphic base in the eastern section of the northern margin of the North China craton.The rock LA-ICP-MS zircon U-Pb isotopic dating indicates that the rock formation age is 2553±6Ma,which is in Neoarchean.Geochemical analysis shows that the rocks are characterized by high SiO_(2),rich Al_(2)O_(3),rich Na_(2)O,low K_(2)O,and low Mg#contents and A/CNK=1.08~1.16.Geochemical data shows that this pluton has geochemical characteristics of Ⅰ-type granite and evolutionary trend of the trondhjemite with adakite and Neoarchean Al-rich TTG rock features.It has relatively low total REE contents with LREE enrichment and positive Eu anomalies.It shows the geochemical characteristics of island arc magma,with an enrichment of some large ion lithophile elements(Rb,Ba,K)and deficit of Ta,Nb,Ti and P and other high field strength element.Comprehensive study shows that northern Liaoning is a subduction-related tectonic background in the late Neoarchean,and it is an important part of accretion orogenic belt by collision of island arc and continent in North China craton in Neoarchean.

关 键 词：锆石 U-PB 年龄 地球化学 奥长花岗岩 华北克拉通 新太古代 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]