福建上杭地区燕山期花岗岩锆石U-Pb年代学及Hf同位素组成

发布时间：2018-02-08 10:13

本文关键词： 花岗岩类锆石U-Pb年代学 Lu-Hf同位素燕山期石壁寨紫金山矿田福建省　出处：《地质学报》2017年10期 　论文类型：期刊论文

【摘要】：选取福建省西南部紫金山中粗粒花岗岩、石壁寨西部含斑细粒二长花岗岩和东部斑状含黑云母二长花岗岩作为研究对象,利用LA-ICP-MS法对三个岩体的锆石进行了U-Pb、Lu-Hf和微量元素分析,获得了3个岩体的岩浆结晶分别为156.5±2.7Ma(晚侏罗世),166.2±8.1Ma(中侏罗世)和154.1±1.4Ma(晚侏罗世)。锆石的Lu-Hf同位素分析结果表明,锆石的两阶段Hf模式年龄(tDM2)分别为1.6~2.2Ga、1.7~2.0Ga和1.7~1.9Ga。锆石Hf同位素初始值ε_(Hf)(t)均为负,分别为-14.88~-8.40、-11.9~-7.8和-10.9~-7.4。锆石的ε_(Hf)(t)、Hf同位素地壳模式年龄分布范围较小,暗示岩体岩浆来源具有较为均一锆石Hf同位素组成。中侏罗世(166.2±8.1Ma)期间,古太平洋板块与欧亚板块发生碰撞,导致洋壳俯冲至陆壳之下,陆壳并发生了小规模的部分熔融,形成了石壁寨西部岩体;碰撞结束后,在晚侏罗世(145~156Ma)期发生由挤压向拉张环境的转换,闽西南岩石圈伸展减薄、壳源物质发生广泛的熔融作用,形成了大规模的紫金山岩体和石壁寨东部岩体。本文的研究成果,为研究闽西南花岗岩体的来源和区域构造演化提供了新的资料证据。
[Abstract]:The coarse granites in Zijinshan, southwestern Fujian Province, the porphyry biotite monzonitic granites in the west of Shibizhai and the porphyry biotite monzonitic granites in the eastern part of Shibzhai were selected as the research objects. The zircon U-PbPbLu-Hf and trace elements were analyzed by LA-ICP-MS method. The magmatic crystallization of the three bodies is 156.5 卤2.7 Ma (late Jurassic) 166.2 卤8.1 Ma (Middle Jurassic) and 154.1 卤1.4 Ma (late Jurassic), respectively. The Lu-Hf isotopic analysis of zircon shows that. The two-stage HF model age of zircon is 1.6 ~ 2.2GaS1.72.0Ga and 1.7Ga-1.9Ga. the initial value of zircon HF isotope 蔚 ~ (+ +) is negative, which is -14.88 ~ 8.40 ~ -11.9 ~ -7.8 and -10.9-7.4 respectively. The age distribution range of zircon's 蔚 ~ (Hf~ +) ~ ~ ~ (-H _ f _ f) isotopic model is smaller than that of Zircon. It is suggested that the magmatic origin of the rock mass has a relatively homogeneous zircon HF isotopic composition. During the Middle Jurassic period (166.2 卤8.1 Ma), the paleo-Pacific plate collided with the Eurasian plate, which led to the subduction of the oceanic crust beneath the continental crust, and a small scale partial melting of the continental crust. The western Shibizhai rock body was formed, after the collision, the transition from compression to extensional environment occurred during the late Jurassic period, the lithosphere was stretched and thinned, and the crust-source material was melted widely. A large scale Zijinshan rock body and an eastern Shibizhai rock mass have been formed. The research results in this paper provide new evidences for the study of the origin and regional tectonic evolution of the granite body in southwestern Fujian.
【作者单位】：福州大学紫金矿业学院;南京大学地球科学与工程学院内生金属矿床成矿机制研究国家重点实验室;西北大学地质学系大陆动力学国家重点实验室;紫金矿业集团股份有限公司;
【基金】：南京大学内生金属矿床成矿机制研究国家重点实验室项目(20-15-05) 福州大学2017年国家级大学生创新训练计划项目(201710386031)资助成果
【分类号】：P588.121;P597

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