Delta-clasts are a type of mantled porphyroclasts widely used as kinematic indicators in rocks. They are defined by a core porphyroclast with wings of recrystallised material. In this VPFFT-ELLE simulation a clast is embedded in an isotropic matrix. All slip systems of one phase have the same critical resolved shear stress (CRSS). CRSS of the core object (grey) and mantle (black) are 50 and 80 times higher than that of the matrix, respectively. The object rotates synthetically and wings develop forming a delta-clast. The simulation shows deformation until a dextral simple shear strain of ten. The model boundaries are periodic.
Sigma-clasts are a type of mantled porphyroclasts widely used as kinematic indicators in rocks. They are defined by a core porphyroclast with wings of recrystallised material. In this VPFFT-ELLE simulation a clast is embedded in an anisotropic matrix. The critical resolved shear stress (CRSS) of the object core (grey) is 50 times higher than that of the softer slip system of the matrix, while that of the mantle (black) 4 times higher. The matrix is anisotropic, with a CRSSs of 1 and 10 for the basal and non-basal slip systems, respectively. The object rotates synthetically at a low rate and wings develop forming a sigma-clast. The simulation shows deformation until a dextral simple shear strain of ten. The model boundaries are periodic.
For more information see article by Ran et al. (2018).