Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (3): 133-149.DOI: 10.13745/j.esf.sf.2023.9.3

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Petrogenesis of reductive S-type granites in the Pengshan district, northern Jiangxi Province, and their implications for tin enrichment: Insights from zircon trace elements

YIN Qingqing1,2(), TANG Juxing1,2, XIANG Xinkui3, ZHAO Xiaoyan1, WANG Fangyue4, XU Yumin3, GUO Hu5, YU Zhendong3, XIE Jinling1,2, DAI Jingjing2, PENG Bo2,*()   

  1. 1. Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China
    2. MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
    3. The Third Geological Brigade of Jiangxi Geological Bureau, Jiujiang 332100, China
    4. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
    5. Laboratory of Non-Fossil Energy Minerals, Tianjin Center of China Geological Survey, Tianjin 300170, China
  • Received:2023-03-16 Revised:2023-09-04 Online:2024-05-25 Published:2024-05-25

Abstract:

The Pengshan tin-polymetallic metallogenic ore field is situated at the transitional junction of the Middle-Lower Yangtze metallogenic belt and the Jiangnan tungsten-polymetallic metallogenic belt. Previous research has indicated that granites associated with large-scale tin mineralization typically stem from highly differentiated peraluminous magmas. However, the precise threshold of oxygen fugacity governing the distribution and migration of tin with mineral phases in reducing magmas remains unknown. It is unclear whether the zonation of tin and tungsten mineralization in northern Jiangxi Province is controlled by the characteristics of the magmatic source or by oxygen fugacity. This study delves into the petrogenesis of granites, the tin source, the redox conditions during the early stages of magmatic evolution, and their influence on the distribution, extraction, and migration of tin within the magma. Through detailed in situ zircon microanalysis of the Pengshan pluton, the findings reveal that the P content of zircon is generally high. The slope of three trend lines fitted by P-(∑REE+Y) is 0.91, 0.85, and 0.81, respectively, aligning with the characteristics of S-type granites (∑REE+Y)<1.15×P. In the Eu/Eu*-YbN/GdN diagram, a negative correlation is observed in all rock groups, indicating that the Eu/Eu* ratios of zircons are constrained by the co-crystallization of titanite and plagioclase. The Hf-Ce4+/Ce3+ zircon and Ti-zircon ratios reflect the degree of reduction in each rock unit within the Pengshan pluton. The zircon Eu anomaly (Eu/Eu*) and Ce4+/Ce3+ zircon ratio exhibit decreasing trends across the three rock units comprising the Pengshan pluton: post-metallogenic granite porphyry→biotite monzogranite batholith→metallogenic muscovite granite. The sandy-argillaceous sedimentary rocks and spilite formed from marine paleo-volcanic eruptive deposits around 1.5 to 1.3 billion years ago likely served as the initial source of tin in the region. The oxygen fugacity of the muscovite granite is lower than that of the Shimensi deposit, and zircon trace elements indicate that the tin-rich magma possesses lower oxygen fugacity compared to the tungsten-rich magma.

Key words: reductivity, S-type granite, Sn enrichment, zircon, northern Jiangxi Province, Pengshan

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