Quantitative parameters associated to progressive mylonitic deformation are strictly controlled by several counterbalancing mechanisms competing with each other. In this view, synergistic quantitative investigation of relatively simple rocks characterized by a clear strain increment can aid to shed new light in the calculation of anisotropic properties driven by progressive grain size reduction and dynamic recrystallisation and/or by phase transformations and metamorphic reactions (e.g. reaction hardening/softening), which often provide a further softening process contributing to concentrate deformation. As an example, the Kavala shear zone, exposed in north-eastern Greece, has been chosen, where early-Miocene syn-extensional granodiorite emplacement occurred; here, relatively isotropic granodiorite gradually evolves towards mylonitic granodiorite, with evidence of NE-SW monotonous stretching lineation consistent with the elongation of the exposed pluton. Stepwise controlled procedure allowed us: i) selection of variably deformed granodiorite samples characterized by homogeneous protolith, as inferred by geochemical and petrographical investigation; ii) quantification of grain size reduction as well as minerochemical modification during progressive shear increase by means of statistical data handling of EDS X-ray maps via Principal- and Canonical-Component-Analysis; iii) investigation on shape and crystallographic preferred orientation of quartz-rich domains, which control the bulk-rock rheology during deformation, via image processing utilities; iv) determination of petrophysical properties at confining pressure in rocks characterized by progressive shear strain. Finally, results pointed out a close relationship between petrophysical properties and changes in microstructure and composition along the shear zone investigated.
|Titolo:||Changes of microstructure, mineralogy, chemistry and anisotropic properties during progressive strain in the Kavala mylonitic shear zone (Rhodope Massif, NE Greece): advancement after a synergistic approach|
|Data di pubblicazione:||2012|
|Appare nelle tipologie:||4.2 Abstract in Atti di convegno|