Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (4): 66-81.DOI: 10.13745/j.esf.sf.2020.4.28

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Trace element characteristics of sphalerite in the Lishan Pb-Zn-Cu polymetallic deposit in Hunan Province and the metallogenic implications

GUO Fei1(), WANG Zhilin1,*(), XU Deru2,3, YU Deshui3, DONG Guojun4, NING Juntao4, KANG Bo4, PENG Erke1   

  1. 1. MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
    2. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
    3. CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
    4. 402 Geological Prospecting Party, Bureau of Geology and Mineral Resources Exploration and Development of Hunan Province, Changsha 410004, China
  • Received:2018-10-08 Revised:2019-03-18 Online:2020-07-25 Published:2020-07-25
  • Contact: WANG Zhilin

Abstract:

The northeastern Hunan Province, located in the central segment of the Jiangnan Orogen, holds one of significant Au-Sb-W-Cu polymetallic metallogenic belts in South China. In recent years the large Lishan Pb-Zn-Cu polymetallic deposit was discovered in this area. The deposit is spatially associated with the Late Jurassic-Early Cretaceous Mufushan granitoids, and orebodies are hosted within altered fracture zones. In this contribution, we analyzed the trace elemental composition of sphalerite using combined EPMA and LA-ICPMS methods. The results show that sphalerite in the Lishan deposit was enriched in Co and Ga, but depleted in Fe, Cd and Ge. Iron, Mn, Cd, Co and Ga elements occur as solid solution, while other elements, notably Cu, Pb, Ag and Sn are distributed as both solid solution and inclusions. Based on the correlation of different trace elements, we discovered some important coupled substitutions: Zn2+↔Fe2+, 4Zn2+↔2Fe2++Ge4++□ (where □ denotes a vacancy), 3 Zn2+↔2Cu+ +Ge4+, and 2Zn2+↔Ag++Sb3+. The Zn/Fe, Ga/Ge, Ge/In and Ga/In ratios, together with Fe geothermometer, indicated a low to medium mineralizing temperature (240-250 ℃) and low sulfur fugacity (lgf(S2) ranging from -13.3 to -9.6). The trace elemental components of sphalerite in the Lishan deposit revealed a significant distinction from the Jinding, SEDEX, VMS, MVT, and skarn deposits. The low Cd/Fe (0.03-0.14, av. 0.06) and Cd/Mn (1.54-6.30, av. 2.91) ratios, as well as low Ge values, suggested an association of the Lishan Pb-Zn-Cu polymetallic deposit with magmatic hydrothermalism. Based on deposit geology and regional tectonic-magmatic evolution, we propose that the Lishan Pb-Zn-Cu polymetallic deposit formed from a hydrothermal system related to the Yanshanian Mufushan pluton, in an extensional setting related to the roll back of the subducting Paleo-Pacific plate. The trace elemental compositions in this study can provide a reference for the determination of deposit genesis.

Key words: sphalerite, trace element, Lishan Pb-Zn-Cu polymetallic deposit, Mufushan pluton, northeast of Hunan Province

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