Fe isotopic characteristics of the Dongshengmiao and the Tanyaokou polymetallic sulfide deposits in Inner Mongolia and their metallogenic significance

Here we report the iron isotopic compositions of pyrites and chalcopyrites from the Dongshengmiao and the Tanyaokou deposits in the Langshan area. The δ56Fe results of irregularly shaped pyrites from graphite-rich mica schists vary from +0.04‰ to +1.11‰, indicating partial oxidation of Fe2+ in an oxygen-limited environment and the conversion to pyrites during diagenesis. While the δ56Fe results of pyrites and chalcopyrites from the ores vary from -1.33‰ to +0.08‰, indicating a hydrothermal origin. In addition, the δ56Fe results of vein pyrites from graphite-rich mica schists vary from -0.39‰ to -0.04‰, which lie between the values of irregularly shaped pyrites and ore pyrites, suggesting mixture of hydrothermal fluids and the early irregularly shaped pyrites. The totally different iron isotopic compositions between irregularly shaped pyrites from graphite-rich mica schists and ore sulfides in the Dongshengmiao deposit indicates that hydrothermal fluids didn't contribute to irregularly shaped pyrite, therefore it is unlikely that synsedmentary hydrothermal activities account for the mineralization in the Dongshengmiao deposit. Combining with the common silicified dolomite marble fragments in the top and bottom part of dolomite marble-hosted sulfide orebody, we suggested that epigenetic mineralization is the main ore-forming form. Besides, the similiarity in iron isotopic characteristics of ore sulfides from the Dongshengmiao and the Tanyaokou deposits indicates the similarity of their metallogenic material sources. © 2016, Science Press. All right reserved.