Development of the new Raman geobarometer for high-pressure and ultrahigh-pressure metamorphic rocks

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04037
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Waseda University (2020-2021); Kyoto University (2019)
• Principal Investigator: Taguchi Tomoki 早稲田大学, 教育・総合科学学術院, 専任講師 (60791704)
• Co-Investigator(Kenkyū-buntansha): 纐纈 佑衣 名古屋大学, 環境学研究科, 講師 (20726385)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: ラマン分光分析 / 藍晶石 / 石英 / 残留圧力 / 地質圧力計 / 変成岩

Outline of Final Research Achievements

Pressure estimation of metamorphic rocks generally depends on the thermodynamic approach. However, this approach may not be applicable in some cases because the natural rock is a complex system. In this study, we challenged to develop a new Raman geobarometer for high-pressure and ultrahigh-pressure metamorphic rocks, using a micro-Raman spectroscopy. The studied samples were kyanite-bearing quartz eclogites from the Gongen area (Sanbagawa belt, southwest Japan). We comprehensively verified the Raman spectra of quartz inclusions in matrix kyanite grains. Based on the results, we examined minutely numerical models of residual pressures, and constructed a new Raman geobarometer for the quartz-inclusions-in-kyanite system.

Free Research Field

岩石学

Academic Significance and Societal Importance of the Research Achievements

熱力学モデルに基づく地質圧力計は固体地球科学分野で広く使用されてきたが、鉱物組み合わせの制限や、その選択の妥当性検証など難点もあった。ラマン分光学に基づく地質圧力計の大きな特徴は、原理的に熱力学から独立して圧力情報が取得できる点にある。また、藍晶石と石英は高圧型変成岩でよく認められる鉱物であり、本研究は汎用的な地質圧力計を提案したものといえる。本ラマン地質圧力計の実用化は、世界各地の様々な地質体における変成進化プロセスの理解に貢献できると期待される。