Oscillatory zoning during the growth of single crystals; a comparison of chemical potential and concentration gradient driven numerical models

Oscillatory zoning occurs in a multitude of minerals growing in both magmatic systems (e.g. zircon, plagioclase, clinopyroxene) and in solid rock (e.g. garnet). Despite the ubiquity of oscillatory growth zoning in minerals, the processes responsible for such compositional zoning remain enigmatic. It has been argued that such zones may form in response to fluctuations in intensive properties, such as temperature, pressure, and magma/fluid chemistry, and/or extensive properties such as surface reaction rates and the creation of a compositional boundary layer during diffusion. However, numerical models that simulate the evolution of a growing crystal remain relatively rare. Here we aim to provide insight to the conditions that attribute to oscillatory mineral zoning of major elements during crystal growth by presenting forward models of diffusion-controlled crystal growth, incorporating multicomponent diffusion and local equilibrium thermodynamics. Two methods are presented, one each in chemical potential and concentration space. These models further constrain the conditions that allow for oscillatory growth zoning. Allowing better insight into the processes occurring during crystal growth in the crust.