日本地球惑星科学連合2018年大会

講演情報

[JJ] Eveningポスター発表

セッション記号 S (固体地球科学) » S-MP 岩石学・鉱物学

[S-MP38] 鉱物の物理化学

2018年5月24日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:大藤 弘明(愛媛大学地球深部ダイナミクス研究センター)、鎌田 誠司(東北大学学際科学フロンティア研究所)

[SMP38-P04] Melting experiments on the MgSiO3-SiO2 system to deep lower mantle pressures

*安西 みゆき1小澤 佳祐1廣瀬 敬1,2新名 良介1舘野 繁彦2 (1.東京大学地球惑星科学専攻、2.東京工業大学地球生命研究所)

キーワード:高圧、融解、下部マントル

MgSiO3–SiO2 system is important to understand SiO2-rich chondritic mantle materials, but its melting phase relations have been determined experimentally only up to 1 GPa. Here we conducted melting experiments in a pressure range from 41 to 139 GPa using a laser-heated diamond-anvil cell (DAC), in order to determine the change in a eutectic melt composition. A cross section at the hot spot of a heated sample was prepared with a focused ion beam (FIB), and its textural and compositional characterizations were made with a SEM/EDS. Quenched molten samples always exhibited a concentric texture, with quenched melt at the center surrounded by liquidus phase(s) of MgSiO3 and/or SiO2. Our data show that eutectic composition changes with increasing pressure from SiO2/(MgO+SiO2) = 0.55 (molar ratio) at 1 GPa (Hudon et al., 2005 J. Petrol.) to ~0.60 at 41 GPa and further to ~0.65 at 135 GPa. Combining with the results on the MgO–MgSiO3 system (Ozawa et al., this meeting), we discuss a large-scale differentiation in chondritic mantles starting from a wide range of MgO/SiO2 ratios.