[B-BG01] Earth and Planetary Science Frontiers for Life and Global Environment

[BBG01-P03] Fluid sampling in the deepest serpentinite-hosted vent site, Shinkai Seep Field, Southern Mariana Arc: Revisiting after 8 years

*Tomoyo Okumura¹, Junichi Miyazaki², Shinsuke Kawagucci², Eiji Tasumi², Ken Takai², Yumiko Harigane³, Molly Anderson⁴, Emily Chin⁵, Nicholas Dygert⁶, Veronique Le Roux⁷, Matthew Leybourne⁸, Yasuhiko Ohara⁹, Ignacio Pujana¹⁰, Robert J. Stern¹⁰, TN438 on board scientist and students (1.Marine Core Research Institute, Kochi University, 2.JAMSTEC, 3.AIST, 4.Woods Hole Oceanographic Institution, 5.Scripps Institution of Oceanography, 6.University of Tennessee, 7.Université de Lorraine, 8.Queen’s University, 9.Hydrographic and Oceanographic Department of Japan, 10.University of Texas at Dallas)

Keywords:Serpentinite-hosted alkaline vent, Shinkai Seep Field, Brucite-Carbonate chimney, Chemosynthetic ecosystem

Deep sea ecosystems associated with fluids produced during serpentinization reactions have attracted much attention in recent years as analogs of the biosphere of the early Earth and potentially on extraterrestrial planets. The Shinkai Seep Field (SSF), discovered in 2010 at a depth of about 5700 m on the landward slope of the southern Mariana Forearc [1], is the world's deepest seep site associated with serpentinization reactions. During previous explorations, a total of five chimney sites and 13 clam colony sites were discovered, and these are characterized by a diverse faunal community of Calyptogena, snails, and polychaetes [2] unlike other similar sites. Fluid composition is essential for understanding this unique site. However, this site is venting cold hydrothermal fluids in and around the chimney structures at a very low rate , making it extremely difficult to detect and collect vent fluid samples.
To overcome this challenge, three tubular container-shaped markers were placed in the SSF chimney field during the KR16-14 cruise in 2016 to accumulate slowly seeping fluid over the years. . We recovered these markers and fluids during the TN438 research cruise on the R/V Thomas G. Thompson from November to December 2024. This presentation will report on past fluid sampling attempts at this site, including preliminary results of fluid analysis collected from the markers installed for eight years. In addition, we will also report on changes at this site over the past eight years.

References
[1] Ohara et al. (2012) Proc. Natl. Acad. Sci. U. S. A., 109, 2831–2835.
[2] Okumura et al. (2016) Geochem. Geophys. Geosys. 17, 3775–3796.