Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (2): 332-352.DOI: 10.13745/j.esf.sf.2020.3.25

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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


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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