日本地球惑星科学連合2014年大会

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ポスター発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT39_2PO1] 地球深部ダイナミクス:プレート・マントル・核の相互作用

2014年5月2日(金) 14:00 〜 15:15 3階ポスター会場 (3F)

コンビーナ:*綿田 辰吾(東京大学地震研究所海半球観測研究センター)、境 毅(愛媛大学地球深部ダイナミクス研究センター)、中川 貴司(海洋研究開発機構地球内部ダイナミクス領域)

14:00 〜 15:15

[SIT39-P09] 放射光X線その場観察と川井式マルチアンビル装置を用いた30 GPaまでのクロム苦土鉱の相関係の解明

*國本 健広1入舩 徹男1藤野 清志1 (1.愛媛大学)

キーワード:Magnesiochromite, in situ X-ray diffraction measurement, Kawai-type multianvil apparatus, phase transition

Phase relations in MgCr2O4 (magnesiochromite) have been studied up to 30 GPa and 1600℃, using a large volume Kawai-type multianvil apparatus and in situ X-ray diffraction measurements system installed at SPring-8/BL04B1. MgCr2O4 spinel dissociates into Mg2Cr2O5 (orthorhombic type) + Cr2O3 (eskolate) at 9 GPa and 1200℃, and then reunion to higher pressure phase (CaTi2O4 type) at 22 GPa and 1200℃. Moreover, another high-pressure phase was observed above CaTi2O4 type structure phase, and this phase was unquenchable to ambient condition. In addition, pressure-induced phase transition in MgCr2O4 was confirmed without decomposition under cold compression process. In this cause, Magnesiochromite is directly transformed to high-pressure phase through the mixture of spinel and high-pressure phase. In this study, CaFe2O4 type and ε-phase, which reported in earlier studies in MgAl2O4 were not observed. The Birch-Murnaghan equation of state was used for least-squares fitting of the volume data (assuming K0’=4). Thus, determined zero-pressure bulk modulus (K0) of the CaTi2O4 type MgCr2O4 was 195 GPa.
In this presentation, we will discuss further details of high-pressure phase relation and physical properties of high-pressure phases in MgCr2O4 series.