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Author Tamura, Y. ♦ Yuhara, M. ♦ Ishii, T. ♦ Irino, N. ♦ Shukuno, H.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Daisen Volcano ♦ Partial-to-total Remelting ♦ Andesite Magma ♦ Phenocryst Content ♦ Phenocryst-rich Dacite ♦ Normal Frac-tionation ♦ Positive Correlation Exists ♦ Resorbed Plagioclase ♦ Voluminous Andesite ♦ Daisen Rock ♦ Dacite Lava ♦ Many Orthopyroxene Phenocrysts ♦ Two-pyroxene Lava ♦ Rim Composi-tions ♦ Contain Feature ♦ Higher-temperature Magma ♦ Sieve-textured Plagioclase ♦ Phenocryst-poor Rock ♦ Sw Japan ♦ Feature Consistent ♦ High-ca Overgrowth Rim
Abstract Voluminous andesite and dacite lavas of Daisen volcano, SW Japan, contain features suggesting the reverse of normal frac-tionation (anti-fractionation), in the sense that magma genesis progressed from dacite to andesite, accompanied by rises in tempe-rature. A positive correlation exists between phenocryst content (0---40 vol. %) and wt % SiO2 (61---67%). Phenocryst-rich dacites contain hornblende and plagioclase that are generally unaltered, clear, and euhedral. However, phenocryst-poor rocks contain sieve-textured plagioclase, resorbed plagioclase, and opacite in which hornblendes are pseudomorphed. Some Daisen rocks contain two coexisting pyroxenes. Many orthopyroxene phenocrysts from two-pyroxene lavas have high-Ca overgrowth rims (up to 50 mm), a feature consistent with crystallization from a higher-temperature magma than the core. Rim composi-tions are similar from phenocryst to phenocryst in individual
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study
Publisher Date 2002-01-01