For her PhD thesis, Christine Kumerics worked in detail on the strain and rotation history of the Messaria shear zone and most of her data are reported in Kumerics et al. (2005). Here we summarise the major results of her work only. The Flinn diagram in (Figure 18) shows the relative shapes of the strain ellipsoids, i.e. prolate vs oblate. As shown in (Figure 18), Fry strains are not fundamentally different from Rf/Φ strains; in some cases, the Rf/Φ strains are slightly greater than the Fry strains, whereas in other cases the opposite is the case. Therefore, we conclude that there was no significant difference in deformation behaviour between the matrix and the porphyroclasts during the accumulation of finite strain. The strain ellipsoids have mostly oblate strain symmetry with some data points in the prolate field (Figure 18). The axial ratios in XZ sections range from 2.4 to 19.9 with SX ranging from 1.2 to 7.2. The stretches in the Z direction, SZ, range from 0.3 to 0.6, indicating strong vertical shortening of 40% to 70%. SY ranges from 0.9 to 1.6, showing mainly extension in this direction.
Figure 18. Flinn diagram
Flinn diagram showing the strain symmetry as obtained by Rf/Φ (white squares) and Fry (black triangles) analysis. Rf/Φ and Fry data from the same sample are connected by dashed tie lines.
Christine Kumerics also analysed vein sets in fifteen outcrop surfaces, thirteen in metapelite of the Ikaria nappe and two in phyllite of the Messaria nappe for determining the degree of rotation during extensional shearing. The degree of rotation is expressed by the so-called kinematic vorticity number, Wm. Wm=1 means that the degree of rotation equals the degree of stretching and the shear zone would not shorten perpendicular to its walls during shearing, i.e. shearing is by simple shear. Wm=0 indicates no shear-related rotation at all and the deformation would be described as pure shear. The distribution of the deformed veins is consistent with top-to-the-NNE shear. Wm ranges from 0.1 to 0.7 and Rf from 1.8 to 8.9. In general, Rf agrees with values of 2.4 to 19.9 for RXZ of finite-strain analysis and again demonstrates heterogeneous shortening perpendicular to the shear zone.