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Kinetics of crystal growth in a terrestrial magma ocean

Solomatov, Viatcheslav S. and Stevenson, David J. (1993) Kinetics of crystal growth in a terrestrial magma ocean. Journal of Geophysical Research E, 98 (E3). pp. 5407-5418. ISSN 0148-0227. https://resolver.caltech.edu/CaltechAUTHORS:20130625-093544733

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Abstract

The problem of crystal sizes is one of the central problems of differentiation of a terrestrial magma ocean and it has been an arbitrary parameter in previous models. The crystal sizes are controlled by kinetics of nucleation and crystal growth in a convective magma ocean. In contrast with crystallization in magma chambers, volcanic lavas, dikes, and other relatively well studied systems, nucleation and crystallization of solid phases occur due to the adiabatic compression in downward moving magma (adiabatic “cooling”). This problem is solved analytically for an arbitrary crystal growth law, using the following assumptions: convection is not influenced by the kinetics, interface kinetics is the rate controlling mechanism of crystal growth, and the adiabatic cooling is sufficiently slow for the asymptotic solution to be valid. The problems of nucleation and crystal growth at constant heat flux from the system and at constant temperature drop rate are shown to be described with similar equations. This allows comparison with numerical and experimental data available for these cases. A good agreement was found. When, during the cooling, the temperature drops below the temperature of the expected solid phase appearance, the subsequent evolution consists of three basic periods: cooling without any nucleation and crystallization, a short time interval of nucleation and initial crystallization (relaxation to equilibrium), and slow crystallization due to crystal growth controlled by quasi-equilibrium cooling. In contrast to previously discussed problems, nucleation is not as important as the crystal growth rate function and the rate of cooling. The physics of this unusual behavior is that both the characteristic nucleation rate and the time interval during which the nucleation takes place are now controlled by a competition between the cooling and crystallization rates. A probable size range for the magma ocean is found to be 10^(−2) − 1 cm, which is close to the upper bound for the critical crystal size dividing fractional and nonfractional crystallization discussed elsewhere in this issue. Both the volatile content and pressure are important and can influence the estimate by 1–2 orders of magnitude. Different kinds of Ostwald ripening take place in the final stage of the crystal growth. If the surface nucleation is the rate-controlling mechanism of crystal growth at small supercooling, then the Ostwald ripening is negligibly slow. In the case of other mechanisms of crystal growth, the crystal radius can reach the critical value required to start the fractional crystallization. It can happen in the latest stages of the evolution when the crystals do not dissolve completely and the time for the ripening is large.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/92JE02839DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/92JE02839/abstractPublisherArticle
ORCID:
AuthorORCID
Stevenson, David J.0000-0001-9432-7159
Additional Information:© 1993 by the American Geophysical Union. Received May 5, 1992; revised September 9, 1992; accepted December 4, 1992. The authors wish to thank the reviewers G. Lofgren and K. V. Cashman for thoughtful criticism of the first version of the paper. Experimental data on plagioclase were substantially extended by courtesy of K. V. Cashman. This work was supported by the National Science Foundation grant EAR-89-16611.
Funders:
Funding AgencyGrant Number
NSFEAR 89-16611
Issue or Number:E3
Record Number:CaltechAUTHORS:20130625-093544733
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130625-093544733
Official Citation:Solomatov, V. S., and D. J. Stevenson (1993), Kinetics of crystal growth in a terrestrial magma ocean, J. Geophys. Res., 98(E3), 5407–5418, doi:10.1029/92JE02839
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39070
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Jun 2013 17:12
Last Modified:03 Oct 2019 05:03

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