| 概要 |
Alkali-pyroxene and alkali-amphibole are main constituent minerals in alkali volcanic rocks. Since the minerals record the condition of magma as compositional zoning in a single crystal or as differen...t paragenesis of rock-forming minerals, we can pursue a condition of their magmas. In Madara-jima island, olivine and clinopyroxene crystallize side by side from early to later stage. The composition of olivine ranges from hyalosiderite to fayalite. The clinopyroxene, however, shows remarkable compositional zoning. The augite grades into aegirine from core to margin in a single crystal.\ The zoning shows that the substitution is changed from CaMgSi_2O_6→CaFeSi_2O_6 to CaMgSi_2O_6→CaFeSi_2O_6 in clinopyroxene solid solution as the・differentiation is proceeded. Riebeckite is formed as a reaction rims around fayalite, aegirine, oxyhornblende, magnetite and hematite in alkali rhyolite. This evidence seems to suggest that water pressure in magma increases at this stage. The variation of oxygen and water partial pressures in magmas from several localities around Sea of Japan is discussed in this paper続きを見る
|
Mendeley出力
