地学前缘 ›› 2014, Vol. 21 ›› Issue (6): 264-280.DOI: 10.13745/j.esf.2014.06.026

• 论文 • 上一篇    下一篇

南岭连阳复式岩体成因：锆石U-Pb年代学、地球化学和Nd-Hf同位素约束

 马星华, 陈斌, 王志强, 高林, 孙克克   

  1. 1. 造山带与地壳演化教育部重点实验室； 北京大学 地球与空间科学学院, 北京 100871 2. 国土资源部成矿作用与资源评价重点实验室； 中国地质科学院 矿产资源研究所, 北京 100037
  • 收稿日期:2014-02-18 修回日期:2014-03-14 出版日期:2014-11-15 发布日期:2014-11-15
  • 作者简介:马星华(1983—)，男，博士，矿物学、岩石学、矿床学专业，主要从事花岗岩成因与成矿研究。E-mail:maxh@pku.edu.cn
  • 基金资助:

    国家自然科学基金面上项目(41272067)；中国博士后科学基金特别资助项目（2013T60029）

Petrogenesis of the Lianyang composite granite, Nanling region: U-Pb zircon geochronology, geochemistry and Nd-Hf isotopes constraints

  • Received:2014-02-18 Revised:2014-03-14 Online:2014-11-15 Published:2014-11-15

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摘要：

报道了南岭地区连阳花岗质复式岩体的锆石U-Pb年代学、岩石地球化学和Nd-Hf同位素数据。LA-ICP-MS锆石U-Pb定年结果表明，连阳岩体中的补体(细粒黑云母花岗岩)形成于100~104 Ma，晚于主体(粗粒似斑状黑云母花岗岩)约40 Ma，表明两者不是分离结晶关系。主体和补体均具有高硅(SiO2 65%~79%)、富碱(Na2O+K2O 6.9%~9.5%)、准铝质过铝质特征(A/CNK=0.9~1.2)，相对高钾(K2O/Na2O=1.3~2.5)，亏损Ba、Sr、P和Ti，富集Rb、Pb和LREE。补体分异程度更高(SiO2 77%~79%)，强烈亏损Eu(δEu=0.03~0.06)。两者εNd(t)值分别为-10.6~-8.4和-9.1~-6.6，补体εHf(t)值为-8.5~-1.8。研究表明连阳岩体的形成与华南燕山晚期陆内伸展作用有关，主要由成熟度较高的元古宙变泥质沉积岩陆壳熔融而成，存在少量幔源岩浆的贡献。通过与典型含W、含Sn和含Nb-Ta矿岩体的对比表明，连阳岩体的主体岩石成矿的可能性较小，而补体具有较好的Sn矿成矿潜力。

 

关键词: 复式岩体, 锆石U-Pb年代学, Nd-Hf同位素, 南岭地区

Abstract:

In this paper, we present zircon U-Pb ages, in situ Hf isotopic, wholerock chemical and Nd isotopic data for the Lianyang composite granite in the Nanling region. Zircon LA-ICPMS U-Pb dating of the supplementary intrusion yielded ages of 100104 Ma, which is significantly younger than the predominant intrusion (144 Ma), suggesting that the former (finegrained biotite granite) is unlikely to be residual melts through fractionation of the latter (coarsegrained porphyritic biotite granite). Both of the two rocks show high SiO2(65%79%), Na2O+K2O(6.9%9.5%) and K2O/Na2O(1.32.5). They are metaluminous to peraluminous (A/CNK=0.91.2), depleted in Ba, Sr, P and Ti, and enriched in Rb, Pb and LREE. The supplementary intrusion shows highly fractionated characteristics (SiO2 77%79%), with extremely negative Eu anomaly (δEu=0.030.06). The NdHf isotopic data (εNd(t)=-10.6-8.4 for the predominant intrusion, εNd(t)=-9.1-6.6 and εHf(t)=-8.5-1.8 for the supplementary intrusion) suggest that the basement rocks should be dominated by Proterozoic parametamorphic rocks. The Lianyang pluton was formed under an extensional setting during the late Yanshanian in the South China. Based on the comparison with W, Sn and Nb/Tabearing granites, it is suggested that the latestage supplementary intrusion is the most important target for Sn prospection.

 

Key words: composite granite, U-Pb zircon ages, Nd-Hf isotopes, Nanling region

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