[B-BG01] 地球惑星科学　生命圏フロンティア

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

*奥村 知世¹、宮崎 淳一²、川口 慎介²、田角 栄二²、高井 研²、針金 由美子³、Anderson Molly⁴、Chin Emily⁵、Dygert Nicholas ⁶、Le Roux Veronique⁷、Leybourne Matthew⁸、小原 泰彦⁹、Pujana Ignacio¹⁰、Stern Robert¹⁰、TN438 on board scientist and students (1.高知大学海洋コア国際研究所、2.海洋研究開発機構、3.産業技術総合研究所、4.ウッズホール海洋研究所、5.スクリップス海洋研究所、6.テネシー大学、7.ロレーヌ大学、8.クイーンズ大学、9.海上保安庁、10.テキサス大学ダラス校)

キーワード：蛇紋岩ホストのアルカリ湧水、しんかいシープ、ブルーサイトー炭酸塩チムニー、化学合成生態系

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.