In situ Raman observations reveal that the gas fluxes of diffuse flow in hydrothermal systems are greatly underestimated

• Published in: Geology (Boulder) 2023-04, Vol.51 (4), p.372-376
• Main Authors: Li Lianfu, Li Lianfu, Luan Zhendong, Luan Zhendong, Du Zengfeng, Du Zengfeng, Xi Shichuan, Xi Shichuan, Yan Jun, Yan Jun, Zhang Xin, Zhang Xin
• Format: Article
• Language: English
• Subjects: Analytical methods; Biogeochemical cycle; Biogeochemical cycles; chemical composition; deep-sea environment; East China Sea; Flow; Fluids; Gases; Geology; hydrothermal conditions; Hydrothermal fields; Hydrothermal springs; Hydrothermal systems; Hydrothermal vents; Iheya North hydrothermal field; Marine ecosystems; marine environment; North Big Chimney Mound; North Pacific; Northwest Pacific; ocean floors; Oceanography; Okinawa Trough; Orifices; Pacific Ocean; Raman spectra; Raman spectroscopy; spectra; Spectroscopy; Spectrum analysis; Sulfur; Sulphur; temperature; volatiles; West Pacific
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/G50623.1

Reduced gases released from hydrothermal vents supply energy to local deep-marine ecosystems and play an important role in global biogeochemical cycles of sulfur and carbon. The habitable, lower-temperature diffuse flow sites in a hydrothermal system generally have higher biomass than focused flow sites. However, a scarcity of observational data of diffuse flows limits our understanding of the role of volatile gases in these environments. We deployed in situ Raman spectroscopy in the Iheya North hydrothermal field of the mid-Okinawa Trough (East China Sea). A Raman probe inserted directly into hydrothermal vent orifices with temperatures of 30-302°C collected Raman spectra of hydrothermal fluids. In situ observation data show that the greater volume of diffuse flows results in a flux of volatile gases one to two orders of magnitude higher than that from focused flow environments. This indicates the great potential of diffuse flow for supplying energy and material to hydrothermal systems. The role played by diffuse flow should be reassessed.