Petrologic and sulfur isotopic significance of highly oxidized and sulfur-rich magma of Mt. Pinatubo, Philippines

A. Imai, E. L. Listanco, T. Fujii

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Dacitic pumices from pyroclastic-flow deposits and air-fall tephra of the June 14-15, 1991, eruption of Mt. Pinatubo, Philippines, are characteristically rich in sulfur. The presence of microphenocrystic anhydrite suggests that sulfur existed mostly as oxidized species in the magma. This supposition is corroborated by unusually high sulfur contents in apatite microphenocrysts and apatite inclusions in other phenocrystic minerals and by the highly oxidized state of the magma. This highly oxidized state possibly caused the extraordinarily high sulfur content of Mt. Pinatubo dacite through prohibition of sulfide fractionation and because of increasing solubility of sulfur as oxidized species with increasing oxygen fugacity. Among the two pumice types, cummingtonite-rimmed hornblende phenocrysts are typically found in type 1 pumice, whereas rare hypersthene has been observed as discrete microphenocrysts in type 2 pumice. These observations indicate conditions at least near if not at vapor saturation in type 1 magma and undersaturation in type 2 magma prior to eruption. -from Authors

元の言語英語
ページ(範囲)699-702
ページ数4
ジャーナルGeology
21
発行部数8
DOI
出版物ステータス出版済み - 1 1 1993
外部発表Yes

All Science Journal Classification (ASJC) codes

  • Geology

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