HU Yu-si1,2, YE Lin1*, WEI Chen1,2, HUANG Zhi-long1, WANG Hao-yu1,2
(1. State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China)
Abstract: An important breakthrough of the exploration of Pb-Zn resources in the Huayuan Pb-Zn orefield, located in the southeastern margin of Yangtze Block, has been obtained in recent years. With the discovery of several large and/or super-large Pb-Zn deposits, such as the Yangjiazhai and Danaopo deposits, over 10 Mt of contained Pb-Zn resources have been newly increased. Therefore, the Huayuan orefield is expected to become a world-class lead and zinc resource base. Although many outcomes on studies of geology and geochemistry of this orefield have been published, researches on the source and evolution process of the ore-forming fluid are not well carried out yet. This has limited to deeply discuss the mineralization mechanism of the Huayuan orefield. In this study, the rare earth elements (REE) compositions of the hydrothermal calcites of different stages have been analyzed for comparing with those of host rocks and different strata in order to discuss the source and evolution of ore-forming fluids in this orefield. The results display that the REE contents and distribution patterns of calcites of different ore stages are obviously different. The REE contents of calcites of the pre-ore and post-ore stages are similar to those of host rocks, but those of the main ore stage calcites are obviously higher than those of calcites formed in other stages, suggesting that the ore-forming fluid could be partly derived from the ore-hosted strata with the input of relatively REE-rich fluids derived from the underlying strata and/or basement. The ore-forming fluid could also carry a large amount of metals (Pb, Zn, etc.) for the Pb-Zn mineralization. In addition, δEu values of calcites formed in the early to main ore stages are all less than 1, indicating that the ore-forming fluids of the early and main ore stages are relatively reduced. However, δEu values of the late ore stage are much higher than 1, suggesting the ore-forming fluid at late stage is relatively oxidized. Overall, the ore-forming fluid was envolved from the relatively reduced in the early and main ore stages to relatively oxidized in the late ore stage.
Keywords: Hydrothermal calcite; rare earth elements; source of ore-forming fluid; ore-forming process; Pb-Zn deposits
ACTA MINERALOGICA SINICA Vol. 40, No.4, 2020, page 441-449
