HR: 0800h
AN: T31C-0588    [Abstracts]
TI: Late Miocene cooling and extension identified on Serifos, western Cyclades: Development of an Aegean metamorphic core complex
AU: * Vogel, H
AF: Geological Sciences, Ohio Univ, Athens, 45701, United States
AU: Schneider, D A
AF: Earth Sciences, Univ of Ottawa, Ottawa, K1N 6N5, Canada
AU: Heizler, M
AF: NMBGMR, New Mexico Tech, Socorro, 87801, United States
AU: Grasemann, B
AF: Structural Processes Group, Univ of Vienna, Vienna, 1090, Austria
AU: Iglseder, C
AF: Structural Processes Group, Univ of Vienna, Vienna, 1090, Austria
AU: Team, A
AB: The island of Serifos is located in the Western Cyclades archipelago, a region noted for Miocene extension, where slab roll-back of the African-Arabian plate and gravitational collapse of a thickened crust has resulted in north-south to northeast-southwest directed extension. Bedrock lithologies on the island are composed of calc- silicates, schists, gneisses, and marbles metamorphosed to greenschist- to lower amphibolite-facies conditions. Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) has recently documented a major low-angle shear zone consisting of (ultra)mylonitic marbles and orthogneisses with stretching lineations and kinematic indicators that record consistent SSW-directed extensional shear. The orthogneisses found within this shear zone are thought to be a syn-kinematic granite that yield preliminary U-Pb zircon rim ages of c. 37 Ma, suggesting a Late Eocene magmatic and deformation event. The southern part of the island is dominated by a largely undeformed, I-type granodiorite pluton of Late Miocene age. Serifos contains all the hallmarks of a classic Aegean metamorphic core complex, and a thermochronology campaign is underway to elucidate the timing of extension and unroofing. Analysis of fourteen mica separates using Ar-Ar thermochronmetry reveals two distinct cooling age populations, separated by a steep age gradient that is coincident with the well-defined shear zone in the northern region of the island. Samples taken from the southern units of the island, within the shear zone, and adjacent to the granodiorite pluton, give cooling ages of 8-9 Ma, illustrating bedrock cooling and exhumation coeval with intrusion of the granodiorite. Lower grade lithologies from the northern portion of the island yield mica cooling ages of 32-35 Ma. Eocene cooling ages present on Serifos are identical to deformation ages reported from the Cycladic Blueschist unit (CBU), present on nearby islands in the Cyclades and Evvia. The cooling and crystallization ages from Serifos reported here demonstrate the protracted nature of extensional deformation since the Eocene, commencing with probable extrusion of CBU-equivalent units. Extensional shear was localized along the site of extrusion during Late Miocene development of a metamorphic core complex, which overprinted much of the earlier metamorphic history. Our results suggest a new domain in the Western Cyclades that has been exhumed by an uncharacteristic south-directed extensional regime since the Late Miocene.
DE: 1140 Thermochronology
DE: 8038 Regional crustal structure
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting