AN Qi1, BAO Guang-ping2,3 *, LAN An-ping1, ZHANG Kun1, YOU Jia-gui1, MENG Qing-tian1
(1. No. 104 Geological Team, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Duyun 558000, China;
2. School of Resource Environment and Earth Science, Yunnan University, Kunming 650504, China;
3. Stake Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)
Abstract: The Youneng Pb-Zn deposit is located in Congjiang County, southeastern Guizhou Province, and is adjacent to the Dihu-Jiuxing Cu polymetallic deposit and the Nage Cu-Pb polymetallic deposit. It is a Pb-dominant polymetallic deposit. In this paper, REE and Pb isotope geochemical study of Pb-Zn ores in this deposit has been undertaken. The results show that Pb-Zn ores have relatively high ΣREE contents, ranging from 30.4 to 240×10-6, with significant negative Eu anomalies (δEu = 0.52-0.81) and insignificant Ce anomalies (δCe = 0.95-1.04, with exception of 0.55 for one sample). This indicates that the REE in the ore-forming fluids could be inherited from the source rocks through the water/rock interaction under the reduced environment. The REE distribution patterns of ores of the Youneng Pb-Zn deposit are quite similar to those of wall rocks (lower metamorphic rocks), but obviously different from those of the basic-ultrabasic and intermediate-acidic magmatic rocks developed in the study area. Generally, the REE characteristics and parameters of ores indicate that the wall rocks could have involved in the mineralization of the Youneng deposit, as the REE of ore-forming fluids could be inherited from the source wall rocks via the water/rock interaction under reduced environment. In addition, the 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios of the ores range from 38.074 to 38.823, from 15.631 to 15.895, and from 17.875 to 18.224, respectively. The 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios of wall rocks range from 38.003 to 38.457, from 15.548 to 15.650, and from 17.774 to 18.181, respectively. It can be seen that the Pb isotopic ratios of ores and wall rocks are quite similar. This further indicates that the wall rocks could have provided materials for mineralization. In summary, it is believed that the Youneng Pb-Zn deposit is a structurally controlled hydrothermal deposit and its Pb, Zn metal elements could be mainly sourced from the ore-bearing wall rocks.
Keywords: REE; Pb isotopes; Ore genesis; the Youneng Pb-Zn deposit; Congjiang County in SE Guizhou
