Sulfur isotopic compositions of sulfides along the Southwest Indian Ridge: implications for mineralization in ultramafic
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Sulfur isotopic compositions of sulfides along the Southwest Indian Ridge: implications for mineralization in ultramafic rocks Teng Ding 1,2,3 & Chunhui Tao 1,3,4 & Ágata Alveirinho Dias 5,6 & Jin Liang 1 & Jie Chen 1 & Bin Wu 7 & Dongsheng Ma 8 & Rongqing Zhang 8 & Jia Wang 3 & Shili Liao 1 & Yuan Wang 1 & Weifang Yang 1 & Jia Liu 1 & Wei Li 1 & Guoyin Zhang 1 & Hui Huang 7 Received: 28 April 2020 / Accepted: 22 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The recently explored Tianzuo hydrothermal field in serpentinized ultramafic rocks of the amagmatic segment of the ultraslowspreading Southwest Indian Ridge displays high-temperature sulfide mineralization (isocubanite, sphalerite, and minor pyrrhotite) and low-temperature (pyrite and covellite) phases. Pyrite can be subdivided into pyrite-I and -II, with the former generally having a pseudomorphic texture after pyrrhotite and the latter typically growing around isocubanite, sphalerite, and pyrite-I or occurring as individual grains in quartz veinlets. The sulfide minerals have the greatest range of δ34S values (− 23.8 to 14.1‰), found so far among modern sediment-starved ridges, with distinct δ34S values for low- and high-temperature mineral phases. The high δ34S values of isocubanite (9.6 to 12.2‰) and sphalerite (9.1 to 14.1‰) suggest that sulfate, which precipitated from seawater during an early low-temperature phase of hydrothermal circulation, was the main sulfur source for these sulfides. PyriteII has the lowest and most variable δ34S values (− 23.8 to − 3.6‰), suggesting microbial sulfate reduction. Pyrite-I has variable and generally positive δ34S values (− 0.1 to 12.0‰), with sulfur being inherited from pyrrhotite from the original thermochemical reduction of sulfate, mixed with volcanogenic sulfur. Intermittent magmatism represented by gabbroic intrusions, and high permeability caused by well-developed fractures associated with detachment faults, contributed to the formation of sulfides in the Tianzuo hydrothermal field. These factors possibly control sulfide mineralization in amagmatic segments of ultraslowspreading ridges. Keywords Tianzuo hydrothermal field . SWIR (Southwest Indian Ridge) . Ultramafic rocks . Sulfides . Sulfur isotopes
Editorial handling: M. Fiorentini Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s00126-02001025-0. * Chunhui Tao [email protected] 1
2
3
Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Central South University, Ministry of Education, Changsha 410083, China Institute of Marine Geology, College of Oceanography, Hohai University, Nanjing 210098, China
4
School of Oceanography, Shanghai Jiaotong University, Shanghai 200030, China
5
Institute of Science and Environment, University of Saint Joseph, Rua de Londres 106
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