Tectonometamorphic evolution of high-pressure rocks from the island of Amorgos (Central Aegean, Greece)

Abstract

Structural and metamorphic data from the island of Amorgos (central Aegean Sea) show evidence for the existence of two distinct high-pressure units, the Metabasite Unit and the Basal Conglomerate Unit. These are exposed at the base of a thick marble sequence and overlying flysch deposits. The Metabasite Unit is characterized by a mineral assemblage of blue amphibole, garnet and clinopyroxene, indicating P – T conditions of 500–600 °C and >13 kbar. It is juxtaposed below carpholite-bearing metaconglomerates and quartz-rich micaschists of the Basal Conglomerate Unit, for which metamorphic conditions of 300–450 °C and 10–14 kbar are estimated. The contact between the two units is interpreted as a low-angle detachment fault that accommodated top-to-the-NW sense of motion. The Amorgos succession above the Basal Conglomerate Unit collectively resembles the stratigraphy of external units in the Hellenides and could possibly be correlated with the so-called ‘Basal Unit’, which crops out in a number of tectonic windows throughout the Aegean Sea. This means that the Metabasite Unit in Amorgos could possibly represent the lowermost structural unit in the central Aegean Sea.