ISING MODELS OF UNDERCOOLED BINARY SYSTEM CRYSTALLIZATION: COMPARISON WITH EXPERIMENTAL AND PEGMATITE TEXTURES

Abstract

Simulations of crystal growth in hydrous albite-quartz and albite-orthoclase systems were performed with the Jackson, Gilmer, and Temkin formulation of the Ising model. These simulations demonstrate that at 873 K (approximately 100 K undercooling), comb textures are produced when growth and diffu- sion probabilities are equivalent. If the growth probability is decreased to 0.1 times that of diffusion, discrete alternating zones of albite and quartz are produced; however, increasing the growth probability to 10 times that of diffusion results in an intergrowth of small domains of albite set in a quartz matrix. At near-liquidus temperatures (973 K), textures similar to those at 100 K undercooling are produced although the crystal-melt interfaces of the comb texture are smoother and the absolute value of the diffusion probability exerts a strong control on the texture, unlike results at 873 K. The textures pro- duced in the simulations with a scale of 10 -7 m are similar to experimentally produced textures with scales of 10 -6 to 10 -4 . The fractal dimension of a comb-textured simulation has been measured and shown to be similar to the fractal dimension of a natural pegmatite with a meter-scale texture. This scaling similarity suggests that these simulations may provide insight into the formation of natural pegmatites despite the 5-7 orders of magnitude difference in scale.