Bulletin of Volcanology

, Volume 51, Issue 3, pp 161–176

Crystallization history of Obsidian Dome, Inyo Domes, California

  • Samuel E. Swanson
  • Michael T. Naney
  • H. R. Westrich
  • J. C. Eichelberger
Article

Abstract

Samples obtained by U.S. Department of Energy research drilling at the 600-year-old Obsidian Dome volcano provide the rare opportunity to examine the transition from volcanic (dome) to plutonic (intrusion) textures in a silicic magma system. Textures in the lavas from Obsidian Dome record multiple periods of crystallization initiated in response to changes in undercooling (ΔT) related to variable degassing in the mag-ma. Phenocr)ysts formed first at low ΔT. A drastic increase in ΔT, related to loss of a vapor phase during initial stages of eruption, caused nucleation of microlites. All of the lavas thus contain phenocrysts and microlites. Extrusion and subsequent devitrification of the dry (0.1 wt% H2O) magma crystallized spherulites and fine-grained rhyolite at high ΔT. A granophyric texture, representing crystallization at a moderate ΔT, formed in the intrusions beneath Obsidian Dome. Textures in the intrusion apparently represent crystallization of hydrous (1–2 wt% H2O) rhyolitic magma at shallow depths.

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Copyright information

© Springer-Veriag 1989

Authors and Affiliations

  • Samuel E. Swanson
    • 1
  • Michael T. Naney
    • 2
  • H. R. Westrich
    • 3
  • J. C. Eichelberger
    • 3
  1. 1.Geology and Geophysics Department and Geophysical InstituteUniversity of AlaskaFairbanksUSA
  2. 2.Chemistry DivisionOak Ridge National LaboratoryOak RidgeUSA
  3. 3.Geochemistry DivisionSandia National LaboratoryAlbuquerqueUSA

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