Generating mechanism of the fragmented crystallites in natural minerals

2023 Fiscal Year Final Research Report

• Project/Area Number: 20KK0307
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research (A))
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Yamaguchi University
• Principal Investigator: Nagashima Mariko 山口大学, 大学院創成科学研究科, 教授 (80580274)
• Project Period (FY): 2021 – 2023
• Keywords: 結晶性 / 非晶質化 / ラマンスペクトル / 緑簾石

Outline of Final Research Achievements

This study proposes a new mechanism for the reduction in crystallinity found in natural epidote-group minerals. This phenomenon, which has been challenging to recognize in terms of long-range atomic arrangement and nanoscale observation, is now understood from the perspective of the short-range atomic arrangement using polarized Raman spectroscopy. The mechanism involves the fragmentation of the crystalline matter, preserving the original atomic arrangement into crystalline nano-regions with a non-crystalline boundary. This fragmentation is believed to occur due to the interaction between the chemical bond properties of distributed elements, the disordered OH group, and the deformation of coordination polyhedra in the epidote structure. The study also proposes a practical application for accurately estimating Fe3+ content in epidotes. This function is based on the Raman spectra collected from 31 natural epidotes and could contribute widely to Earth Science.

Free Research Field

鉱物学

Academic Significance and Societal Importance of the Research Achievements

放射性元素の放射壊変による原子配列の乱れや非晶質化は天然鉱物ではよく知られているが，研究代表者が見出した結晶性低下は放射性元素に起因しない未知の現象であった。この現象は捕捉が困難であるため，普遍的現象であるにも関わらず長年見過ごされてきたのだろう。しかし，結晶質固体物質における結晶性の変化はわずかであっても物性変化に直結し，相の安定性に影響するため，その実態把握や発生機構の解明は不可欠である。本研究で明らかにした実態と提唱した発生機構は，結晶質物質を扱うマテリアルサイエンス全体の発展に波及すると考えられる。