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

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

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

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

Original languageEnglish
Pages (from-to)699-702
Number of pages4
JournalGeology
Volume21
Issue number8
DOIs
Publication statusPublished - Jan 1 1993
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geology

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