In-Situ Evolution of Calcite Twinning during Uniaxial Compression of Carrara Marble at Room Temperature

Calcite twinning is a dominant deformation mechanism at low temperatures. It often used to reconstruct paleostresses: orientations of the principal stress axes, ratios and differential stress. Despite numerous studies, on single crystals aggregates, questions remain about initiation evolution twinning. In particular, existence critical value for activation twin planes debated. this study, Carrara marble samples were uniaxially deformed temperature. The experiments monitored in situ an SEM (Scanning Electron Microscope) analysis was performed regular intervals using image correlation. Image correlation shows link between overconcentration strains appearance first twinned planes. This followed by densification gradual thickening lamellae. Fracturing only appears third stage as precursor collapse sample. inversion, CSIT-2 technique, showed that are globally related applied macroscopic inversion allows one retrieve tensor. Schmid factors extracted from correlated loading curves. For 200 µm diameter, threshold 6.75 8.25 MPa.