Abstract
The kinetics of the α-β transformation in Mg2SiO4 was studied by in situ synchrotron powder X-ray diffraction (XRD) at nine pressure-temperature conditions in the ranges 13.4-15.8 GPa and 850-1100 °C. The transformation from olivine occurred by grain-boundary nucleation and interface-controlled growth mechanisms. Infrared analysis of the recovered samples indicates that a small amount of water, 750 ± 100 ppm by weight, was present in the samples although the experiments were carried out under nominally dry conditions. Nucleation and growth rates were determined by fitting the rate equation for the grain-boundary nucleated transformation to the kinetic data. The activation energy and activation volume for growth were estimated to be 348 (137) kJ/mol and 1.7 (4.5) cm3/mol, respectively. The growth kinetics determined in this study bear upon the field of metastable olivine in the subducting slab as the water contents of samples studied are well known. Nucleation rates were estimated to be relatively large, even at small overpressure conditions, which is consistent with the small activation energy for nucleation derived in this study.
© 2015 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- Composition and I4/m-P42/n phase transition in scapolite solid solutions
- Synthesis and characterization of K2Ca5(SO4)6·H2O, the equivalent of görgeyite, a rare evaporite mineral
- Phase relations in the system Fe-FeSi at 21 GPa
- The speciation of dissolved H2O in dacitic melt
- Nucleation and growth kinetics of the α-β transformation in Mg2SiO4determined by in situ synchrotron powder X-ray diffraction
- Experimental determination of siderite stability and application to Martian Meteorite ALH84001
- Determination of the molar absorption coefficient for the infrared absorption band of CO2in rhyolitic glasses
- Crystallographic properties of the calcium phosphate mineral, brushite, by means of First Principles calculations
- The crystal structure of jonesite, Ba2(K,Na)[Ti2(Si5Al)O18(H2O)](H2O)n: A first example of titanosilicate with porous double layers
- Crystal-chemistry of talc: A near infrared (NIR) spectroscopy study
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- Sieve-textured plagioclase in dacitic magma: Interference imaging results
- Single crystal raman spectroscopy of cerussite
- Sodalite: High-temperature structures obtained from synchrotron radiation and Rietveld refinements
- The structure of metahohmannite, Fe3+2[O(SO4)2]⋅4H2O, by in situ synchrotron powder diffraction
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- Micro-Raman studies of gypsum in the temperature range between 9 K and 373 K
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