Modeling of the dynamics of diffusion crystal growth from a cooling magmatic melt

• Published in: Fluid dynamics 2010-10, Vol.45 (5), p.679-690
• Main Authors: Gorokhova, N. V., Melnik, O. E.
• Format: Article
• Language: English
• Subjects: Boundaries; Calcium aluminum silicates; Classical and Continuum Physics; Classical Mechanics; Cooling; Crystal growth; Crystals; Diffusion; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Mathematical models; Melts (crystal growth); Physics; Physics and Astronomy
• ISSN: 0015-4628; 1573-8507
• DOI: 10.1134/S0015462810050017

The process of diffusion growth of a single crystal of plagioclase (consisting of two components: albite and anorthite) from a cooling magma melt is considered. Crystallization starts when the temperature becomes lower than the melting (liquidus) temperature and occurs as a result of the diffusion of melt components to the boundary of the growing crystal. The crystallization process is simulated by solving a system of nonlinear, linked by cross terms, nonstationary diffusion equations for albite, anorthite, and residual melt in the coordinate system moving with the growing crystal boundary. The dependence of the crystal growth rate on undercooling and temperature and of its composition on temperature and pressure is taken into account. Both quantities substantially depend on the component concentration ratio in the melt on the crystal-melt interface. The competition between the diffusion and crystal growth processes and the complex dependence of these processes on the current melt and crystal compositions and the system temperature lead to a strong nonlinearity of the problem. As a result of numerical simulation, it is established that with a linear decrease in temperature the growing crystal composition changes nonmonotonically. This makes it possible to propose a novel interpretation of the crystal zoning typical of natural magmatic systems.