Browsing by Author "Huang, Kangjun"

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    Cracking the superheavy pyrite enigma: possible roles of volatile organosulfur compound emission
    Lang, Xianguo; Zhao, Zhouqiao; Ma, Haoran; Huang, Kangjun; Li, Songzhuo; Zhou, Chuanming; Xiao, Shuhai; Peng, Yongbo; Liu, Yonggang; Tang, Wenbo; Shen, Bing (2021-10)
    The global deposition of superheavy pyrite (pyrite isotopically heavier than coeval seawater sulfate in the Neoproterozoic Era and particularly in the Cryogenian Period) defies explanation using the canonical marine sulfur cycle system. Here we report petrographic and sulfur isotopic data (delta S-34(py)) of superheavy pyrite from the Cryogenian Datangpo Formation (660-650 Ma) in South China. Our data indicate a syndepositional/early diagenetic origin of the Datangpo superheavy pyrite, with S-34-enriched H2S supplied from sulfidic (H2S rich) seawater. Instructed by a novel sulfur-cycling model, we propose that the emission of S-34-depleted volatile organosulfur compounds (VOSC) that were generated via sulfide methylation may have contributed to the formation of S-34-enriched sulfidic seawater and superheavy pyrite. The global emission of VOSC may be attributed to enhanced organic matter production after the Sturtian glaciation in the context of widespread sulfidic conditions. These findings demonstrate that VOSC cycling is an important component of the sulfur cycle in Proterozoic oceans.
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    Transient marine euxinia at the end of the terminal Cryogenian glaciation
    Lang, Xianguo; Shen, Bing; Peng, Yongbo; Xiao, Shuhai; Zhou, Chuanming; Bao, Huiming; Kaufman, Alan J.; Huang, Kangjun; Crockford, Peter W.; Liu, Yonggang; Tang, Wenbo; Ma, Haoran (Springer Nature, 2018-08-01)
    Termination of the terminal Cryogenian Marinoan snowball Earth glaciation (similar to 650-635 Ma) is associated with the worldwide deposition of a cap carbonate. Modeling studies suggest that, during and immediately following deglaciation, the ocean may have experienced a rapid rise in pH and physical stratification followed by oceanic overturn. Testing these predictions requires the establishment of a high-resolution sequence of events within sedimentary records. Here we report the conspicuous occurrence of pyrite concretions in the topmost Nantuo Formation ( South China) that was deposited in the Marinoan glacial deposits. Sedimentary facies and sulfur isotope data indicate pyrite precipitation in the sediments with H2S diffusing from the overlying sulfidic/euxinic seawater and Fe (II) from diamictite sediments. These observations suggest a transient but widespread presence of marine euxinia in an ocean characterized by redox stratification, high bioproductivity, and high-fluxes of sulfate from chemical weathering before the deposition of the cap carbonate.