Development of a method for quantitatively constraining the thermal history of meteorites using silica minerals

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22370
• 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: Chiba Institute of Technology
• Principal Investigator: Ono Haruka 千葉工業大学, 附属研究所, 研究員 (10880320)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 隕石 / シリカ鉱物 / メソシデライト / 冷却速度

Outline of Final Research Achievements

In this study, we attempted to establish a new estimation method using silica minerals by analyzing silica minerals in the stony-iron meteorite mesosiderite in detail to determine the cooling rate in the low-temperature region, which had previously been estimated only using iron-nickel zoning. The analysis results suggest that the cooling rate of the phase transition from cristobalite to tridymite is less than 0.003-0.01°C/day. Continuation of this study is expected to provide a detailed thermal history of stony meteorites that do not contain much metal, for which low-temperature cooling rates have not been estimated.

Free Research Field

惑星物質科学

Academic Significance and Societal Importance of the Research Achievements

隕石の冷却速度などの熱史は、これまで輝石や金属鉄などを用いて見積もられてきた。しかし、それらが示す熱史は限られた温度領域に限定されている。本研究では、高温から低温まで幅広い温度領域において、数多くの多形（形態）を持つシリカ鉱物に着目した。輝石と金属鉄両方を含むメソシデライト隕石中のシリカ鉱物を詳細に分析することで、シリカ鉱物が850-400℃以下までの冷却速度を示す新しい指標になりうることを明らかにした。