Crystal-growth kinetics of plagioclase in igneous systems: Isothermal H sub 2 O-saturated experiments and extension of a growth model to complex silicate melts

Journal Article · · American Mineralogist; (USA)

OSTI ID:7161759

Muncill, G E ^[1]; Lasaga, A C ^[2]

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1. Geophysical Lab., Washington, DC (USA)
2. Yale Univ., New Haven, CT (USA)

Crystal-growth rates have been experimentally determined for the growth of plagioclase from melts in the H{sub 2}O-saturated system NaAlSi{sub 3}O{sub 8}-CaAl{sub 2}Si{sub 2}O{sub 8}-H{sub 2}O (Ab-An-H{sub 2}O). As in an earlier study on crystal growth rates for plagioclase crystal growth in the 1-atm Ab-An system, the authors have developed an extension of simple, single-component growth theory to predict crystal-growth rates. Unlike the earlier study, the predicted growth rates vary considerably from the experimentally derived growth rates, probably as a result of errors in the calculated viscosities for the experimental bulk compositions or because of a failure of the Stokes-Einstein equation relating diffusion rates and viscosities. The combination of the observed growth rates and data on compositions of the crystals and glasses can be used to constrain the possible mechanisms of crystal growth within the Ab-An-H{sub 2}O system. The rate-controlling factor at low undercoolings is the reaction at the crystal-melt interface. At low and moderate undercoolings the resulting crystals are essentially unzoned and reflect the equilibrium compositions for the growth temperature. The growth mechanism at low and moderate undercoolings appears to represent a coupling of advective and diffusive mass transfer in controlling the growth rate.

• OSTI ID: 7161759
• Journal Information: American Mineralogist; (USA), Vol. 73:9-10; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
ANORTHOSITES
CRYSTAL GROWTH
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
COOLING
FORECASTING
GLASS
KINETICS
MAGMA
MASS TRANSFER
SATURATION
SILICATES
VISCOSITY
WATER
GABBROS
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCKS
SILICON COMPOUNDS
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions