At the southern boundary of the Rhodope Massif, NE Greece, theKavala Shear Zone (KSZ) represents an example of the Eastern Mediterranean deep-seated extensional tectonic setting. During Miocene time, extensional deformation favoured syntectonic emplacement and subsequent exhumation of plutonic bodies. This paper deals with the strain-related changes in macroscopic, geochemical and microstructural properties of the lithotypes collected along the KSZ, comprising granitoids from the pluton, aplitic dykes and host rock gneisses. Moreover, we investigated the evolution of seismic anisotropy on a suite of granitoidmylonites as a result of progressive strain. Isotropic compressional and shearwave velocities (Vp, Vs) and densities calculated frommodal proportions and single-crystal elastic properties at given pressure–temperature (P–T) conditions are compared to respective experimental data including the directional dependence (anisotropy) of wave velocities. Compared to the calculated isotropic velocities, which are similar for all of the investigated mylonites (average values: Vp 5.87 km s−1, Vs 3.4 km s−1, Vp/Vs = 1.73 and density = 2.65 g cm−3), the seismic measurements give evidence for marked P-wave velocity anisotropy up to 6.92% (at 400 MPa) in the most deformed rock due to marked microstructural changes with progressive strain, as highlighted by the alignment of mica, chlorite minerals and quartz ribbons. The highest P- and S-wave velocities are parallel to the foliation plane and lowest normal to the foliation plane. Importantly, Vp remains constant within the foliation with progressive strain, but decreases normal to foliation. The potential of the observed seismic anisotropy of the KSZ mylonites with respect to detectable seismic reflections is briefly discussed.
|Titolo:||Microstructural, compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone (Rhodope Core complex, Greece)|
|Autori interni:||PUNTURO, Rosalda|
|Data di pubblicazione:||2014|
|Appare nelle tipologie:||1.1 Articolo in rivista|