I and S-type Plutonism on Serifos (W-Cyclades, Greece)

Tertiary I- and S-type plutonism are widespread in the Aegean region and frequently associated with extensional tectonic structures. This investigation presents the first evidence of protracted magmatism on the island of Serifos in the western Cyclades and at least two discrete generations of plutonism and coeval dyke generations can be distinguished: (1) An older granitoid with S-type characteristics intruded the Attic-Cycladic crystalline rocks. The granitoid and its host rocks were mylonitized by an earlier phase of deformation at temperature conditions > ~450°C and WSW directed shear. This crustal scale ductile shear zone has been reactivated during the initial stage of a metamorphic core complex formation recording top-SSW sense of shear. Rb-Sr muscovite data from the orthogneiss yield cooling, respectively deformation ages of 15-11.3 Ma. (2) An I-type hornblende-biotite-granodiorite pluton with dacitic to andesitic dyke generations intruded syn- to post-kinematically during ongoing extensional deformation at shallow crustal levels. Single grain zircon TIMS U-Pb ages of the main granodiorite body and its associated dykes are 11.6-9.5 Ma. Cooling ages of these samples scatter between 8.5-7.7 Ma (Rb-Sr on biotite).