Precise classification of sedimentary rocks using multiple isotope measurements of heavy minerals.

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H01316
• 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: Kyushu University
• Principal Investigator: NAKANO Nobuhiko 九州大学, 比較社会文化研究院, 准教授 (20452790)
• Co-Investigator(Kenkyū-buntansha): 足立 達朗 九州大学, 比較社会文化研究院, 助教 (00582652) ; 亀井 淳志 島根大学, 学術研究院環境システム科学系, 教授 (60379691)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: ジルコン / モナズ石 / アパタイト / 同位体

Outline of Final Research Achievements

Apatite and monazite are the waste during zircon separation, which are used for Sr and Nd measurements, respectively using laser ablation multi-collector inductively coupled plasma mass spectrometry. In this project, we successfully set up the routine from mineral separation, U-Pb dating, and Sr-Nd-Hf isotopic measurement using zircon, apatite, and monazite. This method does not require any dissolution of rocks and wet analyses, thus, it allows quite rapid and safety measurements of multi isotopes. Additionally, the isotopic data obtained from each mineral are in good agreement with those of whole rock measured by wet analyses. Using this method, we can evaluate protolith of sedimentary and metasedimentary rocks using detrital zircon, apatite, and monazite.

Free Research Field

岩石学

Academic Significance and Societal Importance of the Research Achievements

堆積岩や変成堆積岩の原岩の年代や分類は，これまでは微化石に頼ることが多かったが，2000年以降は砕屑性ジルコンの年代測定が広く用いられるようになった．本研究はそれをさらに発展させ，数種類の鉱物のマルチ同位体を用いた分類を可能とした．このことは，より詳細な堆積岩の分類，堆積物の供給源の特定，堆積環境の制約を可能とし，日本列島形成史の詳細な解析に利用できることはもちろんのこと，超大陸の復元や造山帯の発達史等，地球規模の地質現象の解明に大きく寄与するものと考えられる．