摘要
在辽东中部的本溪-宽甸一带发育有较大规模的中生代岩浆岩,关于这些岩体的形成时代、岩浆来源及构造背景的研究相对滞后.本溪关门山岩体由花岗斑岩和碱长花岗岩构成,对其进行了岩石学、岩石地球化学及年代学研究.LA-ICP-MS锆石U-Pb定年结果表明,花岗斑岩侵位年龄为126.4±1.5 Ma,碱长花岗岩侵位年龄为125.7±1.7 Ma,形成于早白垩世.花岗斑岩和碱长花岗岩的主量元素具有富Si、K,贫Fe、Mg、Ca、Ti的特征,A/CNK=0.95~1.12;微量元素富集高场强元素K、Th、Rb,亏损Ba、Sr、Ti、P等;具有明显的负Eu异常,(La/Yb)N=7.62~17.32,轻重稀土元素分异明显.上述特征表明关门山岩体属于A型花岗岩.结合地球化学特征,关门山岩体为非造山的伸展构造背景下的岩浆活动产物,其受控于古太平洋板块向欧亚大陆俯冲的岩石圈减薄环境,是华北板块东部伸展地球动力学背景的具体体现.
Large-scale Mesozoic magmatic rocks developed in the Benxi-Kuandian area in central eastern Liaoning Province.However,research on the formation age,magmatic source,and tectonic setting of these rocks relatively lags behind.Guanmenshan pluton is mainly composed of granite porphyry and alkali-feldspar granite,and its petrology,petrogeochemistry and chronology have been studied.LA-ICP-MS zircon U-Pb dating indicates that the emplacement age of the granite porphyry is 126.4±1.5 Ma,the emplacement age of the alkali-feldspar granite is 125.7±1.7 Ma,and that the pluton was emplaced in Early Cretaceous.The major elements of the granite porphyry and the alkali-feldspar granite are high in Si and K,and low in Fe,Mg,Ca and Ti,A/CNK=0.95-1.12.Trace elements are enriched in incompatible elements such as K,Rb,Th and depleted in Ba,Sr,Ti and P,with evident negative Eu anomalies,(La/Yb)N=7.62-17.32,and high field strength elements.These features suggest that the Guanmenshan pluton belongs to A-type granite.Combined with geochemical characteristics,the Guanmenshan pluton is the product of magmatism in the extensional tectonic setting,which was controlled by the subduction of Izanagi Plate to Eurasia Plate in the lithosphere thinning environment.It is considered a concrete manifestation of the eastern North China Plate stretch geodynamic setting.
作者
刘杰勋
李世超
朱凯
赵庆英
Liu Jiexun;Li Shichao;Zhu Kai;Zhao Qingying(College of Earth Sciences,Jilin University,Changchun 130061,China;College of Geo-Exploration Science and Technology,Jilin University,Changchun 130026,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第3期869-879,共11页
Earth Science
基金
国家自然科学基金项目(Nos.41872203,41872234).
关键词
岩石圈减薄
A型花岗岩
伸展构造背景
辽东
地球化学
地质年代学
lithosphere thinning
A-type granite
extensional tectonic setting
eastern Liaoning Province
geochemistry
geochronology
