Dynamic recrystallization is an important process during deformation of many rock forming minerals and occurs under a wide range of metamorphic conditions (Urai et al., 1986; Drury and Urai, 1990). In general, it leads to the formation of new grains at the expense of old ones. Therefore, dynamic recrystallization significantly influences the microstructure as well as the mechanical properties of a rock (Hirth and Tullis, 1992, Rutter, 1998). Resultant microstructures are used to derive processes active during deformation (e.g., Guillopé and Poirier, 1979; Urai et al., 1986; Drury and Urai, 1990; Hirth and Tullis, 1992) and delineate the conditions during which the rock was formed and/or deformed (e.g., Hobbs et al. 1976; Hirth and Tullis, 1992; Twiss and Moores, 1992). Two main mechanisms active during dynamic recrystallization are rotational recrystallization and grain boundary migration recrystallization (e.g., Poirier and Nicolas, 1975; Guillopé and Poirier, 1979; Urai et al. 1986 and references therein).

To be able to interpret microstructures that developed due to dynamic recrystallization, it is vital to know how they form. Questions to be answered involve the way and extent to which specific processes, combination of processes and parameters such as grain boundary mobility affect the microstructure and the rheology of a rock during progressive deformation. Additionally, we still have insufficient knowledge of how and to what extent the initial fabric of rock influences the microstructural development and flow properties of rock during subsequent deformation.

Movies showing the evolution of a microstructure through time and progressive deformation can improve our understanding of how processes change a microstructure. In such movies the formation of microstructural features can be observed and analysed. When interpreting the movies and extrapolating the findings to rocks the observer should always be aware of the limitations of numerical or analogue models. Nevertheless, watching a microstructure development may stimulate our imagination, give rise to new questions, may verify, challenge or change our current understanding of modelled processes and their interaction. In the last two decades movies showing the microstructural development of samples deformed and/or heated in in-situ experiments with organic and salt analogue materials have provided invaluable insight in microstructural development (e.g., Means, 1983, 1989; Means and Ree, 1988; Bons and Urai, 1994; Herwegh and Handy 1998; Bons and Jessell, 1999). Numerical simulations using modelling systems like Elle, which visually represent a microstructure in specific time steps, can also be used to generate movies depicting the development of microstructures. In addition, in such numerical models movies depicting different attributes such as grains and subgrains, dislocation density, crystallographic orientation can be generated. Furthermore, such movies are very useful for teaching.

In this study, two sets of simulations showing the microstructural change due to dynamic recrystallization during progressive deformation are shown. The only difference between the two sets of simulations is the initial fabric. These simulations show that simulations which model the evolution of a microstructure with time may be a powerful tool to improve our understanding of interacting processes and their effect on microstructure through time. This contribution is primarily aimed to illustrate the potential of such numerical models for teaching purposes, scientific investigations of the interaction of concurrent processes active at the grain scale and determination of values such as temperature and grain boundary mobility, which may be characteristic for a specific observed microstructure.