Diffusion-driven orbicular dynamics of metamorphic granites.

We developed a reaction–diffusion model of the Gierer–Meinhardt type to simulate the formation of orbicular patterns in granites. By coupling felsic (light-coloured) and mafic (dark-coloured) materials as the activator and inhibitor, respectively, our model reproduces a wide range of orbicular patterns, including bands and rings. A comprehensive quantitative analysis reveals that the non-equilibrium dynamics between felsic and mafic materials drive their reorganisation into matrix and core structures within the granites. Furthermore, our linear stability analysis demonstrates that the stability of the system, whether stable or oscillatory, is determined by the eigenvalues in the complex plane, providing insight into the two-component reaction–diffusion dynamics governing the felsic-mafic system. Self-organising chemical processes, driven by varying diffusion rates and nonlinear interactions between minerals during the cooling and solidification of magma, can explain the formation of concentric orbicular patterns in granitic rocks. Article highlights: Developed a Gierer–Meinhardt model to simulate orbicular pattern formation in granites. Demonstrated that felsic–mafic interactions drive matrix-core structures. Orbicular textures reflect environmental stability. Inhibition strength regulates mineral banding and spatial patterning. [ABSTRACT FROM AUTHOR]