Challenging research on Earth and Planetary surface environment by in-situ high precision isotope analyses of fine-grained carbonate minerals

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K18814
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Earth and planetary science and related fields
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: USHIKUBO Takayuki 国立研究開発法人海洋研究開発機構, 超先鋭研究開発部門(高知コア研究所), 技術研究員 (10722837)
• Co-Investigator(Kenkyū-buntansha): 藤谷 渉 茨城大学, 理工学研究科(理学野), 助教 (20755615) ; 池原 実 高知大学, 教育研究部自然科学系理工学部門, 教授 (90335919)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: 二次イオン質量分析計 / SIMS / 炭酸塩 / 隕石 / 耳石 / クロマグロ / 有孔虫 / 同位体

Outline of Final Research Achievements

We have established analytical techniques for in-situ carbon, oxygen, and sulfur isotopes with the ion microprobe, IMS 1280-HR of Kochi Institute, JAMSTEC. We applied these techniques for various geologic and meteoritic studies. We found that carbonates in Tagish Lake meteorite have extremely high d13C value in contrast with those of most carbonates in CM chondrites, indicating of accretion of CO2 ice into its parent body. By analyzing bluefin tuna otoliths, we could distinguish difference of seawater temperatures of spawning ocean areas. We also found that sulfur isotope ratios of pyrites in the seafloor hydrothermal deposit significantly changed by more than 20 permil according to growth of the deposit, indicating of change of supply sources of sulfur and growth mechanisms.

Free Research Field

地球惑星物質科学

Academic Significance and Societal Importance of the Research Achievements

柔らかい炭酸塩や硫化鉱物を平滑に研磨できるようになり、微小試料の精密な元素・同位体比分析が可能となった。炭酸塩は耳石やプランクトン炭酸塩殻の様に生態や環境変動の記録を調べたり、熱水活動などの無機的な化学反応の変動を調べたりするなど、多様な研究に於いて有効な鉱物である。局所同位体比分析手法を確立し、かつクロマグロ耳石試料や隕石試料研究で成果を上げた事で、同手法が研究手法として実用的である事を証明した。