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陕西西乡县龙王塘地区新元古代岩体和脉岩锆石U-Pb年代学及源区性质
(1.中国地质科学院地质力学研究所, 北京 100081;2.自然资源部古地磁与古构造重建重点实验室, 北京 100081;3.陕西地矿汉中大队有限公司, 陕西 汉中 723000;4.陕西矿业开发工贸公司, 陕西 西安 710054;5.陕西省矿产资源勘查与综合利用重点实验室, 陕西 西安 710054)
ZIRCON U-PB AGE AND SOURCE CHARACTERISTICS OF NEOPROTEROZOIC GABBRO AND DYKES IN LONGWANGTANG REGION OF XIXIANG COUNTY, SHAANXI PROVINCE
(1.Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;2.Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resources, Beijing 100081, China;3.The Hanzhong Geological Team Company ltd, Shaanxi Geological and Mineral Survey and Development Corporation, Hanzhong 723000, Shaanxi, China;4.Shaanxi Mining Industry & Trade Company, Xi'an 710054, Shaanxi, China;5.Shaanxi Key Laboratory of Mineral Resources Exploration and Comprehensive Utilization, Xi'an 710054, Shaanxi, China)
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投稿时间:2019-02-08    修订日期:2019-05-21
中文摘要: 陕西西乡县广泛出露的晋宁期岩浆岩是研究和理解扬子克拉通基底地质演化的一个窗口。通过对西乡县龙王塘地区的辉长岩体、花岗岩脉和钠长斑岩脉进行锆石U-Pb定年和原位Lu-Hf同位素分析,确定了岩浆侵位时代,揭示了岩浆源区特征。年代学研究结果表明,辉长岩体和花岗岩脉的侵位时间分别为(863.6±4.4)Ma和(863.6±3.8)Ma,是新元古代岩浆作用的产物。在两条钠长斑岩脉中识别出(905.2±8.2)Ma、(807.0±8.9)Ma和(762.5±4.2)Ma三组锆石年龄,第一组为继承锆石的年龄,后两组年龄分别代表两条岩脉的侵位时代。综上可知,龙王塘地区存在~864 Ma、~807 Ma和~763 Ma三期岩浆作用,以及早期(~905 Ma)构造热事件,岩浆作用具有长期性和多阶段性特征。Lu-Hf同位素分析结果表明,辉长岩体和脉岩的εHft)平均值介于+7.1~+10.0之间。对已有地质资料进行综合分析发现,汉南地区的绝大多数新元古代岩体的εHft)为正值,具有随时间偏离亏损地幔线,接近球粒陨石线的基本演化趋势。上述锆石U-Pb年龄和原位Lu-Hf同位素结果表明,龙王塘地区出露的新元古代岩浆岩起源于亏损地幔或新生地壳的部分熔融,形成于活动型大陆边缘环境。
Abstract:There exist a number of Jinningian magmatic rocks in Xixiang county, Shaanxi Province, which is an important "fingerprint" to study and understand the evolution of the Yangtze craton basement. This paper focuses on gabbro body, granite and albitophyre dikes from Longwangtang region, aiming to understand their formation ages and source characteristics through the methods of LA-ICP-MS zircon U-Pb dating and in-situ Lu-Hf isotope analyses. Age data show that gabbro and granite dike emplacement ages are (863.6±4.4) Ma and (863.6±3.8) Ma, respectively, suggesting they are the products of Neoproterozoic magmatism. Three age groups of (905.2±8.2) Ma, (807.0±8.9) and (762.5±4.2) Ma are identified in the two albitophyre dikes; The first group records the inherited zircon ages and the latter two groups represent emplacement ages for the two dikes, respectively. These results suggest that there existed three stages of magmatism (~864 Ma,~807 Ma and ~763 Ma), and also existed an early tectonic-thermal event (~905 Ma), indicating Longwangtang region has undergone and preserved long-lived and multi-phased intrusive activities. Lu-Hf isotopic analysis shows that these samples have εHf(t) average values of +7.1~+10.0. Based on the comprehensive analysis of the available geological data, most εHf(t) values of Neoproterozoic rocks in Hannan are positive, showing the trend of deviating from depleted mantle line and closing to chondrite line with time in general, indicating the Neoproterozoic magmatic rocks of Hannan mainly derived from the partial melting of depleted mantle or juvenile crust in an active continental margin setting.
文章编号:     中图分类号:P597+.1    文献标志码:
基金项目:陕西省地勘基金(61201304167);中国地质调查局地质调查项目(121201104000160916,121201103000150017);国家自然科学基金(41172184);江西省学位与研究生教育教学改革研究项目(JXYJG-2018-167)
引用文本:
郑光高,崔建军,刘晓春,陈少锋,曲玮,乔建新,陈龙耀,赵文平,李淼,刘林.陕西西乡县龙王塘地区新元古代岩体和脉岩锆石U-Pb年代学及源区性质[J].地质力学学报,2019,25(4):574-589DOI:10.12090/j.issn.1006-6616.2019.25.04.056
ZHENG Guanggao,CUI Jianjun,LIU Xiaochun,CHEN Shaofeng,QU Wei,QIAO Jianxin,CHEN Longyao,ZHAO Wenping,LI Miao,LIU Lin.ZIRCON U-PB AGE AND SOURCE CHARACTERISTICS OF NEOPROTEROZOIC GABBRO AND DYKES IN LONGWANGTANG REGION OF XIXIANG COUNTY, SHAANXI PROVINCE[J].,2019,25(4):574-589DOI:10.12090/j.issn.1006-6616.2019.25.04.056

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