43rd ISAS Lunar and Planetary Symposium (August 4-6, 2010. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan
抄録（英）
Lunar feldspathic crust is considered to be a product of a primordial magma ocean crystallization. Mineral distribution in the lunar crust provides us with keys to understand the chemical composition and the mode of crystallization of a lunar magma ocean. Mineralogical studies of feldspathic lunar meteorites show that low-Ca pyroxenes are likely the secondary product after olivine and plagioclase crystallized from a magma. The fact suggests that plagioclase and olivine are the two dominant minerals in the initial crust which formed by a magma ocean crystallization, but low-Ca pyroxene is not a direct product from a magma ocean. If that is a case, a magma ocean composition needs to be more aluminous than that previously estimated by a factor of two or three. Replacement of the primary olivines by low-Ca pyroxenes during the secondary heating events after the magma ocean solidification may have altered an initial abundance of olivine in the primary crust. Lower detectability of olivine than low-Ca pyroxene in the reflectance spectra observation may further bias the real abundance of olivine in the present lunar crust.
Origin of Olivine and Low-Ca Pyroxene in the Lunar Crust
