Development of new geothermobarometry and geospeedmetry based on the kinetics of carbonaceous material

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H07395
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Yoshihiro NAKAMURA 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究員 (60803905)
• Project Period (FY): 2017-08-25 – 2019-03-31
• Keywords: 反応速度論 / 炭質物 / 石墨化 / 低変成作用 / 顕微ラマン分光分析

Outline of Final Research Achievements

This study aims to develop a new type of geothermobarometry and geospeedmetry based on the kinetics of carbonaceous materials. This indicator is particularly suitable for low-grade metamorphic rocks in the Japanese island. Hence, two different approaches by (1) experimental and (2) field studies were conducted for this purpose.
(1) Based on the detailed field study, we found the Ryoke and Sambagawa belts were already amalgamated before exhumation. This may suggest subduction zone and volcanic front were fluctuated by the plate motion.(2) We conducted for kinetic experiments of graphitization at various pressures and durations at 1200 °C. Activation volumes of -21.7 to -33.7 (0.5~2 GPa), and -1.5 to -4.0 cm3 mol-1(2~8 GPa) are obtained. Our data demonstrated that natural graphitization might proceed much more rapidly than previously estimated, owing to the large negative activation volumes of the reaction.

Free Research Field

鉱物学

Academic Significance and Societal Importance of the Research Achievements

本研究によって明らかにした活性化体積によって，自由に変成温度・圧力と被熱時間を炭質物の結晶構造進化から推定できるようになった．つまり，天然に広く産する炭質物の結晶構造を分析するだけで様々な地質情報を読み取れる新しい指標の構築が可能となった．今後さまざまな地域で実験と天然の炭質物結晶構造進化を比較し，より高精度な地質学的指標の構築を目指す．