Hornblende and biotite as geobarometers in granitoid rocks

Conference · Tue Nov 30 23:00:00 EST 1976 · EOS, Trans., Am. Geophys. Union; (United States)

OSTI ID:5384089

Maggetti, M ^[1]; Keller, P; Piwinskii, A J; Weed, H C

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1. Univ. Freiburg, Switzerland

Results of recent experimental hydrothermal investigations (oxygen fugacity regulated, but not controlled) on rocks of granitoid and gabroic compositions at elevated temperatures and water pressures to 1 GPa suggests that horn-blende and biotite may be used as geobarometers if certain criteria are fulfilled. They are as follows: (1) hornblende and/or biotite are liquidus, or near-liquidus phases as determined from petrographic examination of rocks in thin section, (2) they are not relict phases from some earlier magmatic, metamorphic or metasomatic episode, (3) chemical analyses and CIPW weight norms of the rocks are available. Stability fields of biotite and hronblende together with plagioclase are then a function of water pressure, temperature, and rock composition when portrayed in three-dimensional space using a computer program written for CDC 7600 machines. Projection on to the pressure-Differentiation Index plane (where Differentiation Index = normative albite + orthoclase + quartz and indicates rock composition) yields linear relationships for both biotite and hornblende.

• OSTI ID: 5384089
• Journal Information: EOS, Trans., Am. Geophys. Union; (United States), Journal Name: EOS, Trans., Am. Geophys. Union; (United States) Vol. 57:12; ISSN EOSTA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152004* -- Geothermal Data & Theory-- Isotope & Trace Element Studies
ALBITE
AMPHIBOLE
ANORTHOSITES
BAROMETERS
BIOTITE
CHALCOGENIDES
COMPUTER CALCULATIONS
FELDSPARS
GEOBAROMETRY
GEOLOGY
HORNBLENDE
IGNEOUS ROCKS
MEASURING INSTRUMENTS
MICA
MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROLOGY
PRESSURE GAGES
QUARTZ
ROCKS
SILICON COMPOUNDS
SILICON OXIDES
STABILITY