| 研究実績の概要 |
The generation of observed magnetic field, surface geological activities and temperature distribution are all largely controlled by the core mantle boundary heat flux, which is governed by the heat transport properties of the lowermost mantle minerals. Accurate thermal conductivity values of exact compositions of planet-forming minerals are essential for good models of terrestrial planets, providing insights of thermal evolutions of these planets and helping us understand why the Earth is the only active and habitable terrestrial planet nowadays.
The purpose of this study is to understand how impurities in minerals affect the thermal evolution of terrestrial planets and to achieve the following projects: (1) Determination of pressure dependence and temperature dependence of thermal conductivity of (Fe,Al)-bearing bridgmanite with different iron, aluminum content by pulse heating method. (2) Determination of pressure dependence and temperature dependence of thermal conductivity of anhydrous and hydrous Fe-rich ringwoodite by pulse heating method. In this fiscal year, we accomplished project (1). Simultaneous measurements of thermal conductivity and thermal diffusivity of post-spinel and bridgmanite with 5 different compositions were performed under high pressure up to 24 GPa. At 24 GPa, temperature dependence data were taken up to 1100 K. Based on present data, impurity effects on thermal properties of bridgmanite and its influence on slab dynamics and cooling history of terrestrial planets were identified.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
The intended goals for this fiscal year at the time of application are to complete the following tasks: (i) thermal conductivity measurement of bridgmanite, (ii) synthesis experiments of ringwoodite, (iii) thermal conductivity measurement of ringwoodite, (iv) review data and application for models. However, high quality hydrous Fe-rich ringwoodite samples with diameter as large as 2.1 mm are difficult to obtain. The rapid grain growth of this composition makes the recovered samples fragile and difficult to cut into thin enough slices to be measured by pulsed heating method. We are now exploring the best way to synthesize high quality well sintered hydrous ringwoodite.
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