92 Tectonics I

Monday, 23 October 2006
1:30 PM - 5:30 PM

A NEWLY IDENTIFIED, OPPOSITE SENSE AEGEAN CRUSTAL BLOCK PERSISTENT SINCE THE EOCENE REQUIRES KEY REVISIONS TO E-MEDITERRANEAN GEODYNAMICS MODELS

Paper number: 92-6
Program: Technical Sessions
Time: 2:45 PM – 3:00 PM

Authors

Abstract

Eastern Mediterranean geodynamics afford collisional tectonic features ranging from world-class blueschists to subsequent, collapse-engendered lithospheric detachments with anatexis and metamorphic-core-complexes (MCC's), to the present day intense seismicity, striking SLR/GPS-constrained angular velocities and lucid slab tomography. Composite models spanning the Cenozoic history from early high-pressure exhumation to active crustal block rotations typically employ a continued N-NE subducting Africa slab with S-SW-directed terrane plus nappe-stacking and N-NE directed syn-convergent extension (associated with the renowned Aegean MCC's). Data on the nature, distribution and duration of kinematic regimes for these models are pivotal for their geodynamics predictions (e.g. cause versus effect for Hellenic slab-trench retreat vesus Anatolian escape).

Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) presents data from the hitherto geodynamically ill-considered W-Cyclades that identifies a S-SW-directed realm of crustal extension with multiple anatexes and crustal failures that are protracted across Eocene to Late Miocene. On Serifos island, P/T conditions (from petrology and deformation mechanisms) with preliminary zircon U-Pb TIMS crystallisation ages as well as mica Rb-Sr cooling ages reveal a syn- to post-detachment granodiorite with late dyke offshoots and an associated top-to-SSW, mid-upper crustal conditions mylonitic detachment, all of which cross-cut a top-to-SSW, lower-mid crustal conditions high strain zone that mylonitises an S-type granite whose zircons give an ion microprobe U-Pb late Eocene crystallisation age (probably pushing back to Eocene the interval of known Cycladic granitic plutonism). A further top-to-SW high-strain detachment fabric discovered on Kea and consistent kinematics from compiled data for Kithnos and Lavrio reveal that the W-Cyclades is a hitherto unrecognised, roughly 2000x100 km lithospheric extension region (or microplate) that was persistent since the Eocene and, critically, has opposite sense to the NNE-directed Hellenic nappe stacking and detachment kinematics of the E-Cyclades microplate.