R5: Extraterrestrial materials

[R5-04] Constraints on the cooling rate recorded by silica minerals using Mesosiderites

*Haruka Ono¹, Atsushi Takenouchi², Takashi Mikouchi³, Akira Yamaguchi⁴, Naoji Sugiura¹ (1. Chiba Inst. Tech., PERC, 2. Kyoto Univ., Museum, 3. Univ. of Tokyo, Museum, 4. NIPR)

Keywords:Silica, Cooling rate, Tridymite, Cristobalite, Mesosiderite

In this study, we focus on mesosiderites to estimate the quantitative cooling rate recorded by silica minerals over a wide range of temperatures. The samples contain only monoclinic tridymite or aggregates of cristobalite and quartz. The pyroxene exsolution lamellae in mesosiderite containing aggregates of cristobalite and quartz, and silica minerals in newly discovered meteorites, suggest that the cooling rate of cristobalite to tridymite is less than 0.003-0.01 C/day above 1000-1200 C.