2022 Fiscal Year Final Research Report

Investigation of the effects of diagenesis on the stable isotope fractionation based on the speciation analysis

Research Project

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Project/Area Number	19H02007
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 17040:Solid earth sciences-related
Research Institution	Japan Agency for Marine-Earth Science and Technology
Principal Investigator	Nakada Ryoichi 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), 主任研究員 (50726958)
Co-Investigator(Kenkyū-buntansha)	高橋聡東京大学, 大学院理学系研究科(理学部), 助教 (60615251) 岡崎啓史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), 研究員 (90784257)
Project Period (FY)	2019-04-01 – 2023-03-31
Keywords	重元素安定同位体 / 続成作用 / 元素分離 / 堆積物コア
Outline of Final Research Achievements	The objectives of this study were to elucidate the effects of diagenesis on the stable isotope ratios of heavy elements in sediments by combining hydrothermal reaction experiments and analysis of sediment core samples. The plan was to conduct four research steps in four years: (1) establishment of elemental separation methods and analytical conditions, (2) collection of natural samples and determination of isotope levels, (3) hydrothermal reaction experiments, and (4) analysis of stable isotope ratios and coordination environments of natural and experimental samples. Although some parts of the project did not progress as planned due to coronal disasters and equipment breakdowns, in step (1), we achieved elemental separation in a simpler procedure than originally planned and a significant improvement in the accuracy of isotope ratio analysis, which led to results that will lead to subsequent research.
Free Research Field	地球化学
Academic Significance and Societal Importance of the Research Achievements	堆積岩中の重元素安定同位体比は古環境指標として近年爆発的に研究が増加している。重元素安定同位体比は配位環境が支配していることが明らかにされてきたが、続成作用に伴う同位体比の変化もしくは保存過程は全く検証されていない。そこで本研究では続成作用を模擬した熱水反応実験に加えて、日本海の未固結堆積物コア及びコアと同時代・同堆積盆の陸上堆積岩を用いて、安定同位体比測定とX線吸収微細構造(XAFS)法による配位環境分析から続成作用が安定同位体比に与える影響の解明を目指した。本研究は地球化学、鉱物学、地質学、古環境学など広範な波及性を有しており、古海洋環境の変遷とそれに伴う生命進化の理解向上に繋がった。