Plagioclase--garnet--Al/sub 2/SiO/sub 5/--quartz: a potential geobarometer--geothermometer

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Am. Mineral.; (United States)

OSTI ID:6807826

Ghent, E D

For the reaction 3CaAl/sub 2/Si/sub 2/O/sub 8/ = Ca/sub 3/Al/sub 2/Si/sub 3/O/sub 12/ + 2Al/sub 2/SiO/sub 5/ + SiO/sub 2/, the logarithm of the apparent distribution coefficient (K/sub D/) varies from -0.5 to -1.4 for kyanite-bearing assemblages and from -2.1 to -3.4 for sillimanite and/or andalusite-bearing assemblages. Using equilibrium constant equations derived from experimental data on pure phases and an ideal solution model for garnet and plagioclase solid solutions, individual P-T curves can be calculated for different values of log K/sub D/. If P or T can be independently estimated, these curves can be used as either geothermometers or geobarometers. The degree of non-ideality of grossular solid solution in garnet can be estimated from calculations using the activity coefficients of anorthrite in plagioclase and the kyanite--sillimanite P-T equilibrium curves as a limiting case for kyanite and sillimanite-bearing assemblages.

• Research Organization: Univ. of Calgary, Can.
• OSTI ID: 6807826
• Journal Information: Am. Mineral.; (United States), Journal Name: Am. Mineral.; (United States) Vol. 61:7/8; ISSN AMMIA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152004* -- Geothermal Data & Theory-- Isotope & Trace Element Studies
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHALCOGENIDES
CHEMICAL REACTIONS
DIAGRAMS
DISPERSIONS
EQUILIBRIUM
FELDSPARS
GARNETS
GEOBAROMETRY
GEOTHERMOMETRY
MINERALS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHASE DIAGRAMS
PRESSURE MEASUREMENT
QUARTZ
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SOLID SOLUTIONS
SOLUTIONS