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Concerning their provenance and age, the nappes of the Uppermost Unit of Crete are counted among the most enigmatic constituents of the Eastern Mediterranean. U–Pb dating of zircons separated from metavolcanic rocks of the Preveli nappe exposed near Lefkogia yielded Triassic emplacement ages at 237.3 ± 1.8, 241.5 ± 1.2 and 242.1 ± 1.2 Ma. U–Pb grandite dating of subvolcanic barren skarn of this area yielded the same age at 239.3 ± 2.3 Ma. The skarn is dominated by hydrous phases (ferri-actinolite, hydro-grandite, epidote), which developed at T = 400–450 °C in a marine extensional setting due to fluid-assisted metasomatic reactions between chert-bearing limestone and igneous veins. The fluids and their composition played a significant role for the complex oscillatory zoning of the grandite, which largely results from antithetic variations in Fe3+ and Al. The new U–Pb ages suggest that—similar to deep-seated skarns—U–Pb grandite dating of shallow-seated skarns allows dating the complementary record of hydrothermal activity related to the causative melt. Although the development of skarn is regarded as a short-lived process on geological time scales, the skarn formation of the Preveli nappe lasted for more than 20 m.y. as is indicated by additional U–Pb grandite ages obtained from skarn exposed near Kerames (232.7 ± 1.5 Ma) and near Gerakari (218.0 ± 3.5 Ma). The new ages and published data suggest the Uppermost Unit of Crete to be derived either from the peri-Rhodope domain of the Internal Hellenides or from the Pontides of northern Turkey. [ABSTRACT FROM AUTHOR]

Analysis of strain, paleodifferential stress, illite crystallinity, and microfabrics of quartz and calcite suggest that multiply alternating late Oligocene/early Miocene N–S convergence and N–S extension caused significant vertical discontinuities in the grade of high-pressure/low-temperature metamorphism of the Phyllite–Quartzite unit (PQU) of eastern Crete. Constrictional fabrics and parallelism of D2 stretching lineations and fold axes are attributed to enhanced slab pull forces at greater depth of subduction. A major D3 extensional detachment is present in the upper part of the PQU where slates with lowest metamorphic grade (diagenesis/anchizone transition) are resting on top of anchimetamorphic rocks. The highest metamorphic grade (anchi-/epizone transition) has been determined for Skythian rocks on top of pre-Alpine basement. Revived N–S convergence (D4) led to E–W-trending map-scale folds and top-to-the-S directed brittle thrusts. There is a clear correlation between D2-related metamorphic grade, finite strain, differential stress, and deformation mechanisms. At the anchi-/epizone transition, solution–precipitation and dislocation creep of quartz and calcite caused maximum finite strains (RXZ=up to 7) at high strain rates and moderate differential stresses (80–200 MPa). At the diagenesis/anchizone transition, deformation was accommodated by cataclasis, dislocation glide and solution–precipitation creep resulting in relatively low finite strains (RXZ<2) at high differential stresses of up to 300 MPa. [Copyright &y& Elsevier]