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Kao. Fuji. Mayan. Bali. Pinatubo. Pinatubo. Stratovolcanoes. Cinder Cones. Gas Content. Fountains: shields and plateaus. Domes. Viscosity. Classification of Igneous Rocks.
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Kao Fuji Mayan
Stratovolcanoes Cinder Cones Gas Content Fountains: shields and plateaus Domes Viscosity
Classification of Igneous Rocks Figure 2-5. Classification of the pyroclastic rocks. a.Based on type of material. After Pettijohn (1975) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b.Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298.
FeO , MgO, CaO Wt. % oxides Na2O, K2O H2O 45 75 Wt. % SiO2
Water Saturation Exsolution of a vapor Water content (wt. %) of a magma Basalt Andesite Rhyolite Composition
Fractional Crystallization Basalt Andesite Rhyolite low H2O Explosive volcanism ? 50 % SiO2 75% SiO2 Water content of a rhyolitic magma ????
Origin of Andesites • Fractional crystallization of basaltic magma • Contamination of basaltic magma by continental crust • Both of the above • Partial melting of “special (wet ?) manlte”
Origin of Granite/ Rhyolite • Fractional crystallization of basaltic magma ( volume problem for some areas) • Partial melting of continental crust