The extensional shear zone of Kavala is an excellent natural site for investigating the relationship betweenprogressive deformation, correlated rock fabric and distribution of seismic properties. The syn-tectonic granodioritepluton that we studied emplaced during the large-scale extension that affected NE Greece during late Cenozoic time.Across the shear zone, we selected a suite of mylonitic granitoids with textural and compositional featuresrepresentative of progressively increasing strain.The main assemblage of sheared granodiorites is given by quartz, K-feldspar, plagioclase, biotite, white mica withsubordinate allanite and secondary chlorite. Feldspar porphyroclasts usually are enveloped by ribbon-like quartz andmicaceous matrix. S-C-C' foliations developed during the shearing phase are quite common. Calculated and measuredseismic properties of mylonite granodiorites pointed out that, despite the average compressional and shear wavevelocity as well as density values are similar (average values: Vp ~5.87 km s−1, Vs ~3.4 km s−1, Vp/Vs = 1.73,Poisson’s ratio=0.24 and density = 2.65 g cm−3), the Vp- and Vs-related seismic anisotropy becomes progressivelymarked from the least to the most deformed mylonite specimen, with Vp anisotropy ranging from 4.66 to 6.92%.Results obtained indicate, without doubt, the textural control (increasing CPO, especially of strongly anisotropicminerals, grain size reduction, dramatic decrease of clast/matrix ratio) on the petrophysical properties along a granitoidbody within an extensional shear zone, therefore providing a link between microstructures, tectonics and the distributionof seismic properties.
Relationship between mylonitic features and petrophysical properties within the Kavala shear zone (NE Greece).
PUNTURO, Rosalda;CIRRINCIONE, ROSOLINO;FAZIO, EUGENIO;FIANNACCA, PATRIZIA;ORTOLANO, GAETANO;PEZZINO, Antonino
2015-01-01
Abstract
The extensional shear zone of Kavala is an excellent natural site for investigating the relationship betweenprogressive deformation, correlated rock fabric and distribution of seismic properties. The syn-tectonic granodioritepluton that we studied emplaced during the large-scale extension that affected NE Greece during late Cenozoic time.Across the shear zone, we selected a suite of mylonitic granitoids with textural and compositional featuresrepresentative of progressively increasing strain.The main assemblage of sheared granodiorites is given by quartz, K-feldspar, plagioclase, biotite, white mica withsubordinate allanite and secondary chlorite. Feldspar porphyroclasts usually are enveloped by ribbon-like quartz andmicaceous matrix. S-C-C' foliations developed during the shearing phase are quite common. Calculated and measuredseismic properties of mylonite granodiorites pointed out that, despite the average compressional and shear wavevelocity as well as density values are similar (average values: Vp ~5.87 km s−1, Vs ~3.4 km s−1, Vp/Vs = 1.73,Poisson’s ratio=0.24 and density = 2.65 g cm−3), the Vp- and Vs-related seismic anisotropy becomes progressivelymarked from the least to the most deformed mylonite specimen, with Vp anisotropy ranging from 4.66 to 6.92%.Results obtained indicate, without doubt, the textural control (increasing CPO, especially of strongly anisotropicminerals, grain size reduction, dramatic decrease of clast/matrix ratio) on the petrophysical properties along a granitoidbody within an extensional shear zone, therefore providing a link between microstructures, tectonics and the distributionof seismic properties.File | Dimensione | Formato | |
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