Solid solubility limit of incompatible element in olivine aggregates

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03799
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: The University of Tokyo
• Principal Investigator: Koizumi Sanae 東京大学, 地震研究所, 特任研究員 (60792504)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 上部マントル / 多結晶体 / 粒径効果 / 不純物 / 偏析

Outline of Final Research Achievements

Trace elements in rocks segregate at mineral grain boundaries and significantly alter the physical and chemical properties of the Earth's interior. Therefore, quantification of solubility limits of trace elements at grain boundaries is fundamental information for understanding rock properties. To clarify the solubility limits of impurity elements in olivine polycrystals, we synthesized samples with large effective volumes of grain boundaries, controlled the grain size, added trace elements, and established a method to analyze element concentrations along grain boundaries. Two types of impurity-added samples were prepared: pure olivine samples with specific elements added for grain boundary segregation, and samples containing various impurity elements synthesized using mud samples collected from the Horoman peridotite rock body. Three-dimensional elemental mapping and concentration measurements near grain boundaries were performed on the synthesized samples.

Free Research Field

地球科学

Academic Significance and Societal Importance of the Research Achievements

岩石中の狭い構造体である粒界近傍での不適合元素の固溶量の定量化を可能にする試料合成及び元素添加技術、三次元元素マッピング・濃度測定の手法を確立した。合成した高品質の試料は、岩石の粒界の物理化学現象の測定に最適でマントル物性の化学効果の解明に貢献できると期待される。