Triple in-situ analyses of zircon and baddeleyite in Archean mafic rocks to reveal early mantle evolution

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K23458
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: Japan Agency for Marine-Earth Science and Technology (2020); The University of Tokyo (2019)
• Principal Investigator: Sawada Hikaru 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(超先鋭研究プログラム), Young Research Fellow (10845100)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: ジルコン

Outline of Final Research Achievements

Investments in facilities and equipment were made for the separation of zircon from the mafic rocks and its analysis. A custom-made aliquot was made for　efficient heavy mineral separation. A binocular stereomicroscope and its accompanying equipment were purchased to enable efficient observation and separation of fine heavy minerals. Equipment and consumables necessary for making resin mounts of the separated zircon and polishing them were also purchased. Uranium-lead dating, trace element composition, and hafnium isotope ratios of the zircons by laser ablation inductively coupled plasma mass spectrometry were started up. Using these new equipment and methods, we separated zircons from rock samples in Japan and overseas and obtained analytical data. Some of the data have already been published as papers on peer-reviewed international journals.

Free Research Field

地球科学

Academic Significance and Societal Importance of the Research Achievements

地球は45億年前の誕生時から火成活動が続き、プレート沈み込みと共に大陸地殻生産の起きている太陽系でも特異に活動的な水-岩石惑星である。地球史初期のマントル組成進化と地殻生産量は、地球形成直後の内部構造やテクトニクスを解き明かす大きな手がかりであり、固体地球科学のみならず惑星形成論などの広い範囲に波及するが、地質記録に基づいた具体的な制約は難しく未だ研究途上である。本研究で着眼した苦鉄質岩中のジルコンの分析は、今後この課題解決のキーとなる可能性が高く、これまでの成果はその第1歩となるだろう。