Geochemical characteristics of the amphibolites (ophiolitic metabasites) from the Serifos metamorphic core complex, Atticcycladic metamorphic belt, Cyclades, Greece

Half of the surface outcrop of the Serifos island (NW Cyclades, Attic-Cycladic Metamorphic Belt) is composed of a volcano-sedimentary sequence regionally metamorphosed to greenschists facies. This unit consists of, mainly carbonate-rich metasediments, alternating with silicate-rich layers with chlorite and mica-rich layers and enclose a wide variety of metabasites: amphibolite blocks and mafic schists (with minor relict blueschists facies assemblages, now retrogressed to greenschists). The origin of the amphibolites (ophiolitic metabasites) within the Attic-Cycladic Metamorphic Complex (ACMC) remains enigmatic due to the disrupted occurrence of these rocks that makes difficult to constrain the structural relationship of these rocks with their host rocks and their tectonic significance. This study documents preliminary geochemical data (major-and trace elements) of the amphibolites interlayered within the Serifos Greenschist Unit. A comparative geochemical study of these rocks with other meta-ophiolite rocks from similar structural occurrences in other Cycladic islands, is attempted. On the basis of petrographic and major - trace element bulk chemical data, these rocks can be distinguished in different rock types (basalts/andesites and minor gabbros) with different chemical affinities: a) The relatively LILE-enriched amphibolites resemble typical low- to medium – K calc-alkaline basalts (CAB), comparable to the recent Aegean back-arc volcanics. b) Other amphibolites display chemical affinitities similar to island arc tholeiites (IAT). c) The retrogressesd blueschist – to – greenschists facies metabasites are coarse-grained gabbroic rocks with mixed IAT/MORB chemical affinities. Further geochemical work need to be carried out in order to improve our knowledge on the tectonic setting and emplacement of the Serifos amphibolites.