Περίληψη:
The Late Cretaceous Asteroussia event as recorded in the Cyclades is a
potential key to the tectonic evolution of Western Tethys.
Microstructural analysis and Ar-40/Ar-39 geochronology on garnet-mica
schists and the underlying granitoid basement terrane on the island of
Ios demonstrates evidence of a Late Cretaceous high-pressure,
medium-temperature (HP-MT) metamorphic event. This suggests that the
Asteroussia crystalline nappe on Crete extended northward to include
these Gondwanan tectonic slices. In this case, the northern part of the
Asteroussia nappe (on Ios) is overlain by the terrane stack defined by
the individual slices of the Cycladic Eclogite-Blueschist Unit, whereas
in the south (in Crete) the Asteroussia slices are near the top of a
nappe stack defined by the individual tectonic units of the external
Hellenides. This geometry implies that accretion of the Ios basement
terrane involved a significant leap of the subduction megathrust
(250-300 km) southward. Accretion needs to have commenced at or about
similar to 38 Ma, when the already partially exhumed slices of the
Cycladic Eclogite-Blueschist Unit began to thrust over the Ios basement.
By similar to 35-34 Ma, the subduction jump had been accomplished, and
renewed rollback began the extreme extension that led to the exhumation
of the Ios metamorphic core complex.
Συγγραφείς:
Yeung, Sonia
Forster, Marnie
Skourtsos, Emmanuel
Lister,
Gordon
