Direct observation of the fractured surfaces of minerals produced at middle-low Crust and upper Mantleer

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K05679
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Shizuoka University
• Principal Investigator: Masuda Toshiaki 静岡大学, 防災総合センター, 客員教授 (30126164)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: マイクロブーディン構造 / 長柱状鉱物 / 破断面 / レーザー顕微鏡 / FIB–SEM / 核形成 / 結晶成長

Outline of Final Research Achievements

(1) Fractured surfaces of amphibole microboudins in a marble and a metachert were tentatively observed with a laser microscope and FIB-SEM, respectively. Although the fractured surfaces are partly concealed by newly overgrown amphibole grains on the fractured surfaces after the microboudinage, original fractured surfaces show smoothly undulated, not serrated morphology in most places. (2) I published a paper that proposes a new kinetic model of metamorphic minerals based on systematically changeable activation volume for the nucleation under the influence of normal stress in non-hydrostatic stress state in an international journal (Masuda, T. and Omori, Y., 2021. A kinetic model of oriented nucleation under nonhydrostatic stress: implications for the preferred orientation of columnar and platy minerals in metamorphic rocks. Journal of Structural Geology).

Free Research Field

構造岩石学

Academic Significance and Societal Importance of the Research Achievements

（１）角閃石マイクロブーディンの破断面の観察では、地下深部での破断のメカニズムを考察する上で基本的情報を提供した事になる。石英や方解石が流動するような温度圧力環境で微小に起こる角閃石の破断の実態を知ることで、地下深部での岩石の変形への理解が進み、地震発生メカニズムの理解につながる基礎知識の一つを提供できたと考えている。（２）核形成の活性化体積が応力に依存するというモデルは、応力場での結晶の異方的成長の新しい方向性を示しており、今後の変成鉱物の選択配向の議論が活性化する土台を築けたと考える。