Unveiling solid-Earth water distribution of oceanic tranfdorm faults and fracture zones

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K13638
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: National Institute of Polar Research
• Principal Investigator: Fujii Masakazu 国立極地研究所, 研究教育系, 助教 (80780486)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 海洋リソスフェア / トランスフォーム断層・海底断裂帯 / 蛇紋岩化作用 / 海上・深海磁気異常 / 岩石磁気

Outline of Final Research Achievements

In this study, we focused on the water cycle occurring beneath the seafloor, and conducted observational research on oceanic transform faults and fracture zones, which are expected to contain large amounts of water. We collected samples of mantle materials from seven oceanic regions, which had not been easily accessible until now, and constructed a new data set of magnetic and physical properties of these rocks. The results indicate that the density decrease and magnetic changes associated with progress of rock-water reactions commonly occur in mantle domain at different geological settings. In addition, magnetic data acquisition and analysis in three fractured seafloors did not reveal a uniform trend suggesting a relationship with the hydrological cycle. The need for a better understanding of the crustal heterogeneity and paleomagnetic intensity variations is identified as a future challenge.

Free Research Field

固体地球科学

Academic Significance and Societal Importance of the Research Achievements

本研究で得られた海域のマントルに関するデータおよび知見は、地球史を通じて起こってきた海底下の変化について、鉱物の挙動（ナノスケール）から海底大規模構造（テクトニックスケール）までをつ繋ぐ点で極めて重要であり、21世紀の海洋底科学の展開に向けて重要な物質・観測証拠を提示しました。今後、新たな海底下生命圏や物質循環を理解する上でも、それらの基礎となる海底物理場と地質の情報として活用されます。