[S-CG46] ハードロック掘削科学〜陸上掘削から深海底掘削そしてオマーン〜

[SCG46-01] Introduction of IODP Exp. 399 Building Blocks of Life, Atlantis Massif - Hole U1309D deepening

*阿部 なつ江^1,2、McCaig Andrew³、Lang Susan ⁴、Blackman Donna⁵、Ildefonse Benoit ⁶、小原 泰彦^7,8、Orcutt Beth⁹、Menez Benedicte¹⁰、Lilley Marvin¹¹、Wheaet Geoffery¹²、Lissenberg Johan¹³、Klein Frieder¹⁴、Seyfried William¹⁵、Andreani Muriel¹⁶、John Barbara¹⁷、Godard Marguerite⁶、Morris Antony¹⁸、Schwarzenbach Esther¹⁹、MacLeod Christopher¹³、Savov Ivan³、Harding Alistair²⁰、Früh-Green Gretchen²¹ (1.国立研究開発法人海洋研究開発機構研究プラットフォーム運用開発部門マントル掘削プロモーション室、2.金沢大学大学院自然科学研究科、3.リーズ大学、4.南カリフォルニア大学、5.カリフォルニア大学サンタクルズ校、6.モンペリエ大学、7.名古屋大学大学院環境学研究科、8.国立研究開発法人海洋研究開発機構海域地震火山研究部門、9.Bigelow海洋学研究所、10.パリ地球物理研究所、11.ワシントン大学、12.アラスカ大学フェアバンクス校、13.カーディフ大学、14.ウッズホール海洋研究所、15.ミネソタ大学、16.リヨン大学、17.ワイオミング大学、18.プリマス大学、19.ベルリン自由大学、20.カリフォルニア大学サンディエゴ校、21.スイス連邦工科大学チューリッヒ校)

キーワード：アトランティス岩体、U1309D孔、海洋コアコンプレックス、斑れい岩、メルトー岩石反応、国際深海科学掘削計画

The Atlantis Massif in the North Atlantic Ocean is one of the most studied Oceanic Core Complex (OCC) in the world, along with the Atlantis Bank at the Southwest Indian Ocean Ridge, with conducting four drilling expeditions (Exp. 304, 305, 340T and 357) and surveys. The famous Lost City Hydrothermal Field (LCHF) is located on the south side of the massif. It has been the site of many studies of the ocean floor hydrothermal circulation and the subsurface biosphere. In Exp. 304/305, we successfully drilled down to 1415 mbsf (Hole U1309D) with a core recovery rate of over 78%. In addition, the most primary gabbro in the history of ocean drilling, "Olivine-rich troctolite," considered a reaction product of mantle peridotite (harzburgite) and MORB, was also obtained for the first time in drilling. The Hole U1309D will be used for deepening to 2100 mbsf, where a temperature of 220C is expected, and shallow serpentinite drilling and fluid sampling near the Lost City hydrothermal circulation field (IODP Exp. 399) from April to June 2023.
There are 3 objectives for this expedition;
Objective 1: The life cycle of an oceanic core complex: Links between igneous, metamorphic, structural, and fluid flow processes, and testing of geophysical and hydrothermal models. This objective addresses Science Plan Challenges 9, 10, and 14.
Objective 2: Accessing the chemical kitchen preceding the appearance of life on Earth: formation of organic molecules of prebiotic interest at high and low temperatures in the Atlantis Massif. This objective addresses Science Plan challenge 10, 13, and 14, and will also be of great interest to the Astrobiology Community.
Objective 3: Deep biosphere and limits for life in the Atlantis Massif: controls of the lithological substrate, porosity and permeability, temperature, fluid chemistry, and reactive gradients on microbiology. This objective concerns Science Plan Challenges 5 and 6.
In this presentation, we will introduce the objectives and prospects of the Exp. 399, focusing on the integrated analysis of rock properties, rock description, and in-hole measurement data obtained from previous drilling and subsequent studies in Hole U1309D.