Homogenizing rhyolitic glass inclusions from the Bishop Tuff

Journal Article · · American Mineralogist; (United States)

OSTI ID:5639818

Skirius, C M; Peterson, J W; Anderson, Jr, A T ^[1]

---

1. Univ. of Chicago, IL (USA)

Silicate glass inclusions can be homogenized to a single glassy phase free of bubbles and crystals by heating to near magmatic temperatures at near magmatic pressure. Variably devitrified glass inclusions in quartz phenocrysts from the plinian ash-fall pumice and four of the five ash-flow units of the Bishop Tuff were heated in an internally heated gas pressure vessel to 800 or 900C at {approximately}2 kbar for approximately 20 h and quenched nearly isobarically. The heating procedure yielded glassy, unfractured inclusions free of crystals and gas bubbles for most inclusions. Some extensively devitrified inclusions with lower H{sub 2}O content required heating at higher temperature ({ge}900C) for complete homogenization. Inclusions that were intersected by cracks prior to heating do not revitrify owing to loss of volatiles, possibly during posteruptive cooling. Spectroscopic analyses of homogenized inclusions reveal a small range in concentrations of H{sub 2}O and CO{sub 2} that is within the larger range found for stratigraphically equivalent natural, unheated inclusions. Detailed comparisons of the most equivalent inclusions from the same pumice clast or closely similar ones reveal slightly less H{sub 2}O in heated inclusions. These facts are interpreted to signify that few or no volatiles leak from inclusions during heating but that the speciation and absorptive properties of H{sub 2}O may be slightly dependent upon quenching history.

• OSTI ID: 5639818
• Journal Information: American Mineralogist; (United States), Journal Name: American Mineralogist; (United States) Vol. 75:11-12; ISSN AMMIA; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152002* -- Geothermal Data & Theory-- Properties of Minerals & Rocks
BUBBLES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CRACKS
DEVOLATILIZATION
DISPERSIONS
FLUIDS
GASES
GLASS
HEAT TREATMENTS
HOMOGENEOUS MIXTURES
IGNEOUS ROCKS
INCLUSIONS
MAGMA
MATTER
MINERALS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PRESSURE DEPENDENCE
QUENCHING
RESERVOIR ROCK
RHYOLITES
ROCKS
SILICATE MINERALS
SPECTROSCOPY
TEMPERATURE DEPENDENCE
VAPORS
VITRIFICATION
VOLATILE MATTER
VOLCANIC ROCKS
WATER VAPOR