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

N. W. Dunbar, Richard Hervig

Research output: Contribution to journalArticle

82 Citations (Scopus)

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)
JournalJournal of Geophysical Research
Volume97
Issue numberB11
StatePublished - 1992

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petrogenesis
Stratigraphy
melt inclusion
stratigraphy
Trace Elements
tuff
magma
inclusions
tephra
Crystallization
ignimbrite
magma chamber
Ions
igneous rocks
Electrons
trace element
trace elements
Chemical analysis
ion microprobe
chambers

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Petrogenesis and volatile stratigraphy of the Bishop Tuff : evidence from melt inclusion analysis. / Dunbar, N. W.; Hervig, Richard.

In: Journal of Geophysical Research, Vol. 97, No. B11, 1992.

Research output: Contribution to journalArticle

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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",
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