日時 ： ２００８年２月１日（金）17：00〜
場所 ： 愛媛大学理学部講義棟 １０１室
要 旨
After Mg, Si and Fe: Ca and Al are of the most abundant elements of the Earth's mantle, under the assumption of the pyrolitic composition. This make the study of the physical properties and the phase transformations of Ca- and Al-bearing silicates a key-point to the understanding of the Earth's mantle processes. In the transition zone, it is believed that M3(Al,M+Si)2Si3O12 majorite garnet (M = Mg,Fe,Ca) is the main host of calcium and also a deposit for aluminum. Former studies showed that at the P,T conditions of the lower mantle, garnet decomposes into a mix of (Mg,Fe)SiO3 and CaSiO3 perovskites, with Al mainly hosted in the Mg-pv. Although the mechanisms and effects of the Al-incorporation in the Mg-pv have been widely studied, some questions remained about the CaSiO3 perovskite: We conducted HP-HT experiments on Ca3Al2Si3O12 grossular garnet in order to better understand the mechanisms of formation of Ca- and Al-bearing phases at the Earth's lower mantle conditions. Recent works suggested that the Ca-pv could incorporate more Al than showed in former studies: this feature could have implications for the partitioning of other 2+ and 3+ elements (like iron) but also 4+, as well as consequences over the compressibility of their host minerals. The agreement of our results with models and mantle processes from the literature is discussed.
問い合わせ先：土屋 卓久 TEL （089）927-8198
E-mail takut@sci.ehime-u.ac.jp
