Multi-scale modeling of water-fluid reactions based on observations on nano strtuctures

2022 Fiscal Year Final Research Report

• Project/Area Number: 18KK0376
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research (A))
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Tohoku University
• Principal Investigator: Okamoto Atsushi 東北大学, 環境科学研究科, 教授 (40422092)
• Project Period (FY): 2019 – 2022
• Keywords: 岩石ー流体相互作用 / 岩石組織 / 水熱実験 / ナノスケール / 熱水鉱床 / シリカ / 蛇紋岩 / 空隙

Outline of Final Research Achievements

Reactions involving mass transfer in rock-fluid systems produce characteristic structures ranging from the nanoscale to the macroscopic scale. In this project, in collaboration with Utrecht University and Karlsruhe Institute of Technology, the products of hydrothermal reactions in natural and laboratory experiments were analyzed in detail. Unusual spherical pyrite particles were found in black ore deposits, and crystal orientation analysis revealed that they grew dynamically while floating in submarine hydrothermal vents. The importance of micropores formation associated with hydrothermal alteration such as serpentinization and chloritization on the seafloor and in subduction zones was clarified. The growth mechanism of quartz particles via metastable phases in fluid flow along fractures and the influence of the basement were also clarified. Through this project, an international network has been expanded by co-organizing a research meeting at Utrecht University.

Free Research Field

岩石学

Academic Significance and Societal Importance of the Research Achievements

本課題では、ナノスケールの岩石解析の中心地であるユトレヒト大と共同研究により、様々な岩石―流体反応の組織解析を行った。黒鉱鉱床の球状黄鉄鉱から熱水噴出孔で浮遊しながら粒子が成長する描像を明らかにし、実験的にも急激な過飽和でのシリカ粒子の形成過程を明らかにし、急激な過飽和状態での鉱物粒子形成の理解を大きく進めた。また、熱水変質により、自己促進的に微細な空隙を形成して、その水道を使って反応が進行する描像を天然と実験から明らかにしている。岩石―流体反応による自発的な構造形成は地球内部の反応プロセスの理解のみならず、鉱床形成、地熱開発、地震と流体の関係などの理解に大きく貢献している。