Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT20] Property and role of liquids inside terrestrial planets

Sun. May 26, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Tatsuya Sakamaki(Department of Earth Science, Tohoku University), Yoichi Nakajima(Kumamoto University, Priority Organization for Innovation and Excellence)

[SIT20-P07] Formation of highly pure anorthite crust on the low-volatile astral bodies by low-viscous magma ocean

*Tatsuya Sakamaki1, Yoshio Kono2 (1.Graduate School of Science, Tohoku University, 2.Geodynamics Research Center, Ehime University)

Keywords:anorthite melt, viscosity, structure, high pressure, high temperature, lunar magma ocean

Anorthite (CaAl2Si2O8) is a Ca-endmember of plagioclase, and it is a main component of a crust on the astral bodies, such as Moon and 4 Vesta, Thick anorthite-rich crust has been formed through a process of magma ocean. Here we conduct high-pressure and high-temperature experiments and in-situ X-ray analysis to simultaneously assess the viscosity and structure of anorthite magmas under pressures of up to 6.6 GPa. We find contrasting behavior in the viscosity between liquid anorthite and albite (NaAlSi3O8), which is Na-endmember of plagioclase. The big difference in viscosity between anorthite and albite melts has important implications for planetary differentiation. Na-poor astral bodies (Moon, 4 Vesta, etc.) have been dominated by low-viscous magma ocean and, eventually caused an efficient differentiation between crystal and magma. This process prevented the melt from trapping in the grain boundaries of floating anorthites. This makes the highly pure anorthite crust on the Moon observed by the remote sensing.