ELLE: AN INTEGRATED SCHEME TO MODEL TECTONIC AND METAMORPHIC MICROSTRUCTURES

Tectono-metamorphic microstructures form by the complex interplay between various physical and chemical processes: mineral reaction, crystal-plastic flow, brittle failure, dissolution-precipitation, grain boundary migration, etc.. The different scaling behaviour of these processes inhibits simultaneous scaling of all these processes from geological to laboratory conditions and scales, precluding the experimental modelling of the formation of many microstructures (e.g. snowball garnets, crenulation cleavages). The different behaviour of the various processes has led to a mostly fragmented approach in their numerical modelling, where each process is studied in isolation, thus neglecting the all-important process coupling. ELLE overcomes this impasse by incorporating the main modelling methods (finite elements, finite difference, Potts models, particle code and front-tracking) in a single hybrid scheme, together with a flexible and realistic 2D description of the microstructure [1,2]. Individual processes are programmed as modules or plug-ins, which each in turn act on the microstructure in small spatial and time-increments. So far, ELLE has been applied with success to static and dynamic recrystallisation [3,4], but the possibilities are rapidly expanding. The modelling of geological materials has necessitated the initiation of a web-based mineral-properties database, which will be available to the scientific community.

[1] See: http://microstructure.info [2] Jessell, Bons, Evans, Barr, Stüwe. 2001. Elle: the numerical simulation of metamorphic and deformation microstructures, Comp. Geosci. 27, 17-30. [3] Bons, Jessell, Evans, Barr, Stüwe. 2001. Modelling of anisotropic grain growth in minerals. Geol. Soc. Am. Mem. 193, 39-49. [4] Becker, Koehn, Walte, Jessell, Bons, Passchier, Evans. 2003. Numerical simulation of disequilibrium structures in solid-melt systems during grain growth. J.Virtual Explorer 11.