講演情報
[T1-P-17]Key Findings from IODP Expedition 399 on the Building Blocks of Life: A Long Section of Serpentinized Depleted Mantle Peridotite
*阿部 なつ江1,2、野坂 俊夫3、マッケイグ アンドリュー4、ラング スーザン5、リッセンバーグ ヨハン6、ブルム ピーター7、IODP Exp.399 Science Party7 (1. 海洋研究開発機構、2. 金沢大学、3. 岡山大学、4. リーズ大学、5. ウッズホール海洋研究所、6. カーディフ大学、7. テキサスA&M大学)
キーワード：
蛇紋岩化かんらん岩、アトランティス岩体、国際深海科学掘削計画第399次航海、海洋コア・コンプレックス、深掘り
The upper mantle is essential for understanding magmatism, crust formation, and element cycling between Earth's interior, hydrosphere, atmosphere, and biosphere. Mantle composition and evolution are inferred through surface sampling and indirect methods. We recovered a 1268 m section of serpentinized mantle peridotite from the Atlantis Massif, with minor gabbroic intrusions, showing depleted compositions and mineralogical variations controlled by melt flow. Located at 30 degrees North on the Central Atlantic Ridge, the Atlantis Massif is an ocean core complex exposing gabbroic rocks and serpentinized peridotite from the lower oceanic crust to the upper mantle. Four previous IODP expeditions were conducted here. IODP Expedition 399 (April 12 - June 12, 2023) by D/V JOIDES Resolution aimed to elucidate the formation of the oceanic core complex, explore reaction processes between the oceanic crust, upper mantle, and seawater, investigate non-biological water-rock reactions representing ancient systems, and evaluate sub-seafloor life activity.
Hole U1601C at the serpentine site in the southern massif was drilled to 1267.8 mbsf, becoming the fifth deepest hard rock hole in IODP history. Continuous temperature, density, porosity, and seismic velocity measurements were taken, along with fluid samples from multiple depths. Dunite zones in these cores exhibit intermediate dips, contrasting with initially steep mantle fabrics, indicating oblique melt transport. Extensive hydrothermal fluid-rock interaction is recorded across the core's full depth, with oxidation in the upper 200 m. Alteration patterns align with vent fluid composition in the nearby Lost City hydrothermal field.
Future analysis of these core samples and data will elucidate the oceanic lithosphere structure, formation of oceanic core complexes, crust alteration, and the generation of hydrogen and methane, essential for the subsurface biosphere.
Hole U1601C at the serpentine site in the southern massif was drilled to 1267.8 mbsf, becoming the fifth deepest hard rock hole in IODP history. Continuous temperature, density, porosity, and seismic velocity measurements were taken, along with fluid samples from multiple depths. Dunite zones in these cores exhibit intermediate dips, contrasting with initially steep mantle fabrics, indicating oblique melt transport. Extensive hydrothermal fluid-rock interaction is recorded across the core's full depth, with oxidation in the upper 200 m. Alteration patterns align with vent fluid composition in the nearby Lost City hydrothermal field.
Future analysis of these core samples and data will elucidate the oceanic lithosphere structure, formation of oceanic core complexes, crust alteration, and the generation of hydrogen and methane, essential for the subsurface biosphere.
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