日本地球惑星科学連合2019年大会

講演情報

[E] 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-IT21] 核-マントルの相互作用と共進化

2019年5月27日(月) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:河合 研志(東京大学大学院理学系研究科地球惑星科学専攻)、飯塚 毅(東京大学)、太田 健二(東京工業大学大学院理工学研究科地球惑星科学専攻)、土屋 卓久(愛媛大学地球深部ダイナミクス研究センター)

[SIT21-P04] Viscosity of potassium titanosilicate melt at high pressure

*鈴木 昭夫1 (1.東北大学大学院理学研究科地学専攻)

キーワード:マグマ、粘度、高圧力

Viscosity of silicate melt is a fundamental property, which controls volcanic processes, including rates of melt extraction, ascent, and magma mixing. Titanium oxide is contained less than 10 wt% in terrestrial magmatic liquids, however, some lunar magmas contains it over 10 wt%. The addition of titanium to silicate melt affects on the properties such as viscosity, density, and compressibility. Especially the pressure dependence of viscosity is of great interest, because magma is generated in the planetary interiors. The aim of this study is to measure the viscosity of K2TiSi4O11 melt at high pressures to estimate the influence of the pressure-induced structural change of melt.
We performed in situ falling sphere viscometry in the pressure range from 1.3 to 7.4 GPa, by using the MAX-III high pressure apparatus at BL14C2 and NE7A beamlines at Photon Factory in KEK, Tsukuba, Japan. A falling platinum sphere in the melt was monitored by using an X-ray CCD camera with a YAG:Ce fluorescence screen. We observed that the viscosity of KTS4 melt decreased up to 3.3 GPa. In contrast, the pressure dependence in viscosity was not observed above 3.3 GPa. Based on XANES spectra of K2TiSi4O11 glasses quenched under high pressure, Paris et al. (1994) showed that the coordination number of titanium increased with increasing pressure. The present study suggests that the melt becomes depolymerized by the coordination change of titanium under high pressure.