地学前缘 ›› 2020, Vol. 27 ›› Issue (2): 332-352.DOI: 10.13745/j.esf.sf.2020.3.25

• 矿床地质地球化学 • 上一篇    下一篇

湖南水口山铅锌多金属矿田成矿岩体花岗闪长岩锆石U-Pb年龄、Hf同位素及地质意义

李永胜,甄世民,于晓飞,公凡影,杜泽忠   

  1. 1. 中国地质调查局 发展研究中心, 北京 100037
    2. 自然资源部 矿产勘查技术指导中心, 北京 100083
  • 收稿日期:2020-02-09 修回日期:2020-03-10 出版日期:2020-03-25 发布日期:2020-03-25
  • 作者简介:李永胜(1983—),男,博士,高级工程师,主要从事矿产调查与区域成矿学研究。E-mail:zzkclys@126.com
  • 基金资助:

    中国地质调查局项目“整装勘查区矿产地质调查与找矿预测”(DD20190159,DD20190166)和“重要锡、锰等矿集区矿产地质调查”(DD20190166)

Zircon UPb geochronology and Hf isotopic compositions of igneous rocks from the Shuikoushan Pb-Zn deposit, Hunan Province, and their geological significance.

LI Yongsheng,ZHEN Shimin,YU Xiaofei,GONG Fanying,DU Zezhong   

  1. 1. Development and Research Center, China Geological Survey, Beijing 100037, China
    2. Technical Guidance Center for Mineral Resources Exploration, Ministry of Natural Resources, Beijing 100083, China
  • Received:2020-02-09 Revised:2020-03-10 Online:2020-03-25 Published:2020-03-25

摘要:

水口山铅锌多金属矿田是我国南岭地区重要的有色金属和贵金属生产基地之一。矿田内中酸性岩体发育,研究这些岩体的地质地球化学特征对理清区内成岩成矿演化谱系和指导找矿勘探均具有重要意义。该矿田内,老鸦巢4号和鸭公塘3号花岗闪长岩岩体的主微量元素组成相似,都具有高钾钙碱钾玄及准铝质的特点。岩石微量元素配分呈平滑的右倾,轻稀土元素富集,重稀土元素分布平滑,具有弱的负铕异常。LAICPMS锆石UPb定年表明,老鸦巢花岗闪长岩的年龄为(162.9±0.7) Ma,鸭公塘花岗闪长岩的年龄为(156.3±0.6) Ma。年龄结果表明水口山矿田花岗闪长岩岩体主要形成于燕山早期,经历了多期多阶段侵位过程。锆石原位LuHf同位素分析结果显示,老鸦巢花岗闪长岩εHf(t)值为-11.2~-8.24,二阶段模式年龄(TDM2)为1 920~1 734 Ma;鸭公塘花岗闪长岩εHf(t)值为-13.51~-6.23,二阶段模式年龄为2 063~1 601 Ma,显示鸭公塘岩体壳幔混合作用强于老鸦巢岩体。结合岩石地球化学特征及前人对矿田内仙人岩二长岩等岩体的研究结果,文章认为形成老鸦巢和鸭公塘岩体的岩浆主要起源于古老下地壳玄武岩火成岩的部分熔融。该矿田在165~155 Ma处于中晚侏罗世地壳拉张减薄的构造背景中,岩浆岩锆石的εHf(t)值急剧增加,幔源岩浆底侵作用增强。水口山铅锌多金属矿田与鸭公塘及仙人岩的岩体形成时代一致,三者具有成因联系,壳幔岩浆混合为成矿提供了大量金属物质,是区内形成众多铜铅锌金矿床的重要因素。

关键词: 水口山矿田, 花岗闪长岩, 锆石UPb定年, Hf同位素, 地质意义

Abstract:

The Shuikoushan PbZn polymetallic orefield is an important nonferrous and precious metalproducing area in Nanling, China. Many intermediateacidic igneous rocks occur in this area, and studying their geological and geochemical characteristics is critical for clarifying their diagenetic magmaticmetallogenic evolution and guiding ore exploration. The Laoyachao No. 4 and Yagongtang No. 3 granodiorites have similar major and trace elemental compositions and have metaluminous and highK calcalkaline characteristics of shoshonitic series. The rocks display generally flat, rightdipping rare earth element patterns with enriched light rare earth elements, relatively flat high rare earth element patterns, and slightly negative Eu anomalies. Zircon laser ablation inductively coupled plasma mass spectrometry UPb dating showed that the Laoyachao granodiorite formed at 162.9±0.7 Ma, and the Yagongtang granodiorite intruded at 156.3±0.6 Ma. This suggests that igneous rocks in the Shuikoushan ore field mainly formed during the early Yanshanian and underwent multiple emplacement stages. In situ Hf isotope analyses revealed εHf(t) values ranging from -11.2 to -8.24 and twostage Hf model ages (TDM2) of 1920-1734 Ma for the Laoyachao granodiorite as well as εHf(t) values of -13.51 to -6.23 and TDM2 ages of 2063-1601 Ma for the Yagongtang granodiorite. This showed that more mantle material was added to the Yagongtang magma. Based on geochemical compositions and previous studies of the Xianrenyan monzonite in the study area, we argue that the Laoyachao and Yagongtang granodiorites were mainly derived from the partial melting of basaltic rocks in the Mesoproterozoic lower crust. From 165 to 155 Ma, the Shuikoushan ore field was in an extensionalthinning setting, and the εHf(t) values of igneous rocks increased rapidly, indicating enhanced underplating of mantle magmas. Mineralization ages of the Shuikoushan PbZn deposits were coeval with the formation of the Yagongtang and Xianrenyan plutons, indicating genetic relationships. Cocontribution of crustal and mantle oreforming metals was critical to the formation of numerous CuPbZnAu deposits in the Shuikoushan area ore field.

Key words: Shuikoushan orefield, granodiorite, zircon UPb geochronology, Hf isotope, geological significance

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