Genesis of the Lengshuikeng Ag-Pb-Zn Orefield in Jiangxi: Constraint from In-situ LA-ICPMS Analyses of Minor and Trace Elements in Sphalerite and Galena
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State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences,State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences

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    Abstract:

    The Lengshuikeng AgPbZn orefield, located in Guixi County, Jiangxi Province, is one of the important ore cluster areas in China. There are two types of ore bodies in the Lengshuikeng orefield: coarse veins, veinlet, and dissemination ores occur in porphyry granite intrusions, and massive sulfide ore bodies occur in volcanic clastic rock. However, the genesis of both two kinds of ore bodies and their relationship remains controversial. We analyzed the concentration of minor and trace elements in sphalerite and galena from these two types of ore bodies using insitu LAICPMS to constrain genetic mechanism of this deposit. Analytical results show that the sphalerites from coarse veins and veinletdissemination ore body have relatively high contents of Fe, Mn, Pb, Ag, Cu, Sb, Sn and Tl, whereas the sphalerites from massive sulfide ore body have much higher content of Cd. There are also some differences in the contents of trace elements between galena from two kinds of ore bodies, much higher content of Ag, Sb, Sn and Au in coarse vein, veinletdissemination ore body, and relative higher content of Cd, Bi, Se and Tl in massive sulfide ore body. Comparison study with various genetic PbZn deposits both home and abroad suggests that the sphalerites in the Lengshuikeng orefield have relatively low Zn/Cd (66~131), Cd/Fe (006~031) and low content of Co (mostly<10×10-6), and relative high contents of Sn (mostly>1×10-6), and these features are similar to that of sphalerites from volcanogenic massive sulphide (VMS) deposits, indicating that they may possess same formation process. Our study also confirms that Fe, Cd, Ag, Sb and Tl occur in sphalerite as solid solution and Cu, Pb, and Sn may be present within microscopic inclusions. Ag, Sb, Cd, Sn and Tl occur in galena as solid solution while Mn, Bi and Se occur in galena as microscopic inclusions. By using the Cdfractionation temperature (Tcd) geothermometer of sphaleritegalena, we obtain the formation temperature of 238~246 ℃ for stratabound massive sulfides ore body and lower temperature of 209~224 ℃ for coarse vein, veinletdissemination ore body. Stratabound massive sulfides have relatively low contents of Fe and Mn, which may result from the high oxygen fugacity. In summary, we suggest that the two types of ore bodies in the Lengshuikeng orefield have a same genetic mechanism, with oreforming fluids and materials originating from deep magmatic fluids. The variations of trace element concentrations in sphalerite and galena cloud are mainly ascribed to the temperature, wall rocks and oxygen fugacity.

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LENG Chengbiao, QI Youqiang.2017. Genesis of the Lengshuikeng Ag-Pb-Zn Orefield in Jiangxi: Constraint from In-situ LA-ICPMS Analyses of Minor and Trace Elements in Sphalerite and Galena[J]. Acta Geologica Sinica,91(10):2256-2272

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History
  • Received:July 03,2016
  • Revised:October 14,2016
  • Adopted:October 26,2017
  • Online: October 26,2017
  • Published: