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湘南王仙岭花岗岩体的锆石U-Pb年代学、地球化学、锆石Hf同位素特征及其地质意义
引用本文:郑佳浩,郭春丽.湘南王仙岭花岗岩体的锆石U-Pb年代学、地球化学、锆石Hf同位素特征及其地质意义[J].岩石学报,2012,28(1):75-90.
作者姓名:郑佳浩  郭春丽
作者单位:1. 地质过程与矿产资源国家重点实验室,中国地质大学地球科学与资源学院,北京100083
2. 中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037
基金项目:本文受国土资源部公益性行业科研专项(200911007-11)和国家自然科学重点基金项目(40930419)联合资助.
摘    要:湘南王仙岭岩体由主体电气石黑云母花岗岩和侵入其内部的黑云母二长花岗岩组成,LA-MC-ICPMS锆石U-Pb定年显示电气石黑云母花岗岩形成于印支期(235.0±1.3Ma),黑云母二长花岗岩形成于燕山期(155.9±1.0Ma),表明该岩体是两期岩浆活动的产物。这两期岩石均为高钾钙碱性系列,A/CNK值为1.07~1.66,属过铝-强过铝质花岗岩类。稀土元素显示LREE富集,HREE亏损,Eu负异常明显(0.01~0.38)的特征。早期电气石黑云母花岗岩和晚期黑云母二长花岗岩的εHf(t)值分别为-7.92~+4.61和-10.66~-5.35;两阶段Hf模式年龄(tDM2)分别为1758~967Ma和1875~1538Ma。两期花岗岩均来自于古中元古代地壳物质重熔,其中早期电气石黑云母花岗岩在侵位上升过程中捕获了部分幔源老锆石,成岩过程中有少量地幔物质参与,且其源区具有高εHf(t)值的特点。综合前人研究成果,本文认为华南中生代印支期和燕山期均有钨锡矿化作用,印支期花岗质岩浆形成于碰撞挤压作用间隙伸展环境,而燕山期花岗质岩浆可能形成于大陆边缘弧后伸展环境。

关 键 词:LA-MC-ICPMS锆石U-Pb年龄  岩石地球化学  锆石Hf同位素  王仙岭岩体  华南
收稿时间:2011/8/12 0:00:00
修稿时间:2011/12/3 0:00:00

Geochronology, geochemistry and zircon Hf isotopes of the Wangxianling granitic intrusion in South Hunan Province and its geological significance
ZHENG JiaHao and GUO ChunLi.Geochronology, geochemistry and zircon Hf isotopes of the Wangxianling granitic intrusion in South Hunan Province and its geological significance[J].Acta Petrologica Sinica,2012,28(1):75-90.
Authors:ZHENG JiaHao and GUO ChunLi
Institution:State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
Abstract:The Wangxianling intrusion in South Hunan Province consists of two granitoids,the main tourmaline biotite granites and the biotite monzonite granites invading into the former.LA-MC-ICP MS zircon U-Pb dating shows that tourmaline biotite granites formed in Indosinian(235.0±1.3Ma)while the biotite monzonite granites formed in Yanshanian(155.9±1.0Ma),indicating that Wangxianling intrusion is the product of two-time magmatic activities.The compositions of these two period granites fall into the calcalkaline category,with an A/CNK ratio of 1.07~1.66,which are peraluminous to strongly peraluminous granites.Their whole rock rare earth elements demonstrate total LREE enrichment and HREE deficit with significant negative Eu anomalies(0.01~0.38).The εHf(t)values and two-staged Hf model ages of tourmaline biotite granites and biotite monzonite granites are-7.92~+4.61,1758~967Ma and-10.66~-5.35,1875~1538Ma,respectively.In this paper we suggest that both the tourmaline biotite granite and biotite monzonite granite are originated from the Paleo-and Mesoproterozoic crustal remelting,and the earlier tourmaline biotite granites captured a large number of mantle-derived zircons and there were high-εHf(t)materials in its source region.Combined with previous research results,we infer that the both Indosinian and Yanshanian periods in South China have tungsten and tin mineralization,the Indosinian granitic magma formed in interval lithosphere extensional environment during the collision compression while the Yanshanian granitic magma formed in the extensional environment of the back arc continental margin.
Keywords:LA-MC-ICP MS zircon U-Pb dating  Geochemistry  Zircon Hf isotopes  Wangxianling granitic intrusion  South China
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