吉林中部敖花村角闪辉长岩锆石U-Pb定年、Hf同位素和岩石地球化学特征  

Zircon U-Pb dating,Hf isotopic and geochemical characteristics of the hornblende gabbro in Aohua Village,central Jilin Province

作　　者：孙永刚[1,2] 李碧乐[1] 王永胜[2] 李良[3] 张学海[2] 赵昌吉[1] 李翱鹏 SUN Yong-gang;LI Bi-le;WANG Yong-sheng;LI Liang;ZHANG Xue-hai;ZHAO Chang-ji;LI Ao-peng(College of Earth Sciences,Jilin University,Changchun 130061,China;Geological Survey Institute of Jilin Province,Changchun 130102,China;College of Earth Sciences,Yunnan University,Kunming 650000,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]吉林省地质调查院,吉林长春130102 [3]云南大学地球科学学院,云南昆明650000

出　　处：《岩石矿物学杂志》2021年第2期257-268,共12页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目(41272093);吉林省自然科学基金资助项目(20180101089JC)。

摘　　要：古太平洋板块的俯冲在欧亚大陆东缘的区域构造演化中发挥了重要作用,但其发生的时间尚不清楚。本文报道了吉林中部新发现的敖花村角闪辉长岩的锆石U-Pb年龄、Hf同位素组成和岩石地球化学数据。锆石U-Pb定年显示,角闪辉长岩形成于早侏罗世(180.3±2.3 Ma),锆石εHf(t)值高且均一(9.6~11.3)。岩石地球化学分析显示样品低Si和Al,高Fe、Mg和Ca,富集轻稀土和大离子亲石元素(如Rb、Ba、U、K和Sr),亏损重稀土和高场强元素(如Nb、Ta和Ti),具有弱Eu负异常(δEu=0.67~0.98)。岩石起源于板片流体交代的亏损岩石圈地幔,形成过程中分离结晶、地壳混染和堆晶作用不明显。结合东北地区东段早中生代火成岩组合及时空分布,认为古太平洋板块向欧亚大陆下的俯冲开始于早侏罗世,敖花村角闪辉长岩形成于与古太平洋俯冲密切相关的弧后环境。The subduction of the Paleo-Pacific Plate played an important role in the regional tectonic evolution of the eastern margin of the Eurasian continent,but the timing of this event remains ambiguous.To address this issue,this paper reports zircon U-Pb ages,zircon Hf isotopic compositions and petrogeochemical data of whole-rocks for the newly-found hornblende gabbro in Aohua Village,central Jilin Province.Zircon U-Pb dating shows that the hornblende gabbro was formed in Early Jurassic(180.3±2.3 Ma),and has high and uniformεHf(t)values(9.6~11.3).Petrogeochemical analyses show that the samples are characterized by low Si and Al,and high Fe,Mg,and Ca,enrichment of light rare earth elements and large-ion lithophile elements(e.g.,Rb,Ba,U,K,and Sr),and depletion of heavy rare earth elements and high-field-strength elements(e.g.,Nb,Ta,and Ti),and have weak negative Eu anomalies(δEu=0.67~0.98).They were derived from a depleted lithospheric mantle source that had previously been metasomatized by slab-derived fluids,with unapparent effects of fractional crystallization,crustal contamination and cumulation in the formation process.Combined with rock associations and spatial distribution of Early Mesozoic igneous rocks in the eastern part of Northeast China,the authors hold that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent started in Early Jurassic,and the hornblende gabbro was formed in the back-arc setting which might have been closely related to the subduction of the Paleo-Pacific Plate.

关 键 词：吉林中部 角闪辉长岩 锆石U-PB定年 岩石地球化学 HF同位素组成 古太平洋板块 

分 类 号：P597.3[天文地球—地球化学] P595[天文地球—地质学]