Petrogenesis and volatile stratigraphy of the Bishop Tuff: evidence from melt inclusion analysis

N. W. Dunbar, Richard Hervig

Research output: Contribution to journalArticle

83 Scopus citations

Abstract

The Bishop Tuff (BT), erupted from the Long Valley Caldera at 0.74 Ma, is composed of a Plinian tephra and ignimbrite. Based on ion and electron microprobe analyses of melt inclusions (MI), a strong H2O gradient was present in the upper portion of the magma chamber. The H2O content of the magma which formed the Plinian tephra drops from 6 wt.% to 3.5 wt.%. In contrast, the magma which formed the ignimbrite contained a relatively constant amount of H2O, between 2 and 4 wt.%. The strong drop in H2O content of the magma which formed the Plinian tephra suggests that only in its extreme upper part, if any, was the PH2O in the magma close to Ptotal. The range in the trace element concentrations of inclusions suggests that fractional crystallization may have affected magmatic composition. However, magma mixing may also have been an important process in establishing the final trace element zonation within the Bishop magma chamber. -from Authors

Original languageEnglish (US)
Pages (from-to)15,129-15,150
JournalJournal of geophysical research
Volume97
Issue numberB11
DOIs
StatePublished - 1992

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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