Cracking the superheavy pyrite enigma: possible roles of volatile organosulfur compound emission

Xianguo Lang; Zhouqiao Zhao; Haoran Ma; Kangjun Huang; Songzhuo Li; Chuanming Zhou; Shuhai Xiao; Yongbo Peng; Yonggang Liu; Wenbo Tang; Bing Shen

doi:10.1093/nsr/nwab034

Cracking the superheavy pyrite enigma: possible roles of volatile organosulfur compound emission

Natl Sci Rev. 2021 Mar 1;8(10):nwab034. doi: 10.1093/nsr/nwab034. eCollection 2021 Oct.

Authors

Xianguo Lang¹, Zhouqiao Zhao², Haoran Ma², Kangjun Huang³, Songzhuo Li¹, Chuanming Zhou⁴, Shuhai Xiao⁵, Yongbo Peng⁶, Yonggang Liu⁷, Wenbo Tang⁸, Bing Shen²

Affiliations

¹ State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, and Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China.
² Key Laboratory of Orogenic Belts and Crustal Evolution of the Ministry of Education, and School of Earth and Space Science, Peking University, Beijing 100871, China.
³ State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China.
⁴ State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China.
⁵ Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
⁶ International Center for Isotope Effect Research, Nanjing University, Nanjing 210023, China.
⁷ School of Physics, Peking University, Beijing 100871, China.
⁸ School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, USA.

Abstract

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 (δ³⁴S_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 ³⁴S-enriched H₂S supplied from sulfidic (H₂S rich) seawater. Instructed by a novel sulfur-cycling model, we propose that the emission of ³⁴S-depleted volatile organosulfur compounds (VOSC) that were generated via sulfide methylation may have contributed to the formation of ³⁴S-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.

Keywords: Cryogenian; Datangpo Formation; organosulfur compound; sulfur cycle; sulfur isotope.