TWO ALTERNATIVE SOLUTIONS FOR THE DEVELOPMENT OF A MARGINAL BASIN IN NE GREECE

Abstract

Several ophiolites are exposed intermittently in NE Greece along a NW-SE striking belt from Guevgueli to the Sithonia peninsula (IMHOB). This belt may be extended east- and southeastwards to include the Evros, Samothraki and Lesvos ophiolites (IMHOB plus ESL). Minor mafic exposures running approximately parallel to the IMHOB form the Therma-Volvi-Gomati complex (TVG). All these suites display common features: they are incomplete ophiolite sequences, lack ultramafic members, are broadly autochthonous and display ages 10-20 Ma younger than the ophiolites from western Greece. Chemical variations suggest that these ophiolites were formed in a marginal basin. The salic Chortiatis magmatic suite is found between the IMHOB and TVG, on the Chalkidiki peninsula and represents a volcanic arc formation. Geological and geochemical characteristics coupled with geographical constraints led us to reconstruct two alternative plate tectonics interpretations for the evolution of this basin. The first suggests a fore-arc environment for the IMHOB plus ESL ophiolites and a back-arc rifting for the TVG, due to the northward subduction of the Axios (Vardar) ocean. The second favours an opposite interpretation for the IMHOB plus ESL and TVG ophiolites, relating their formation to a basin that developed due to the southwards subduction of the Strandza ocean of Paleotethys. In any case, these ophiolites have been formed in a marginal basin regime, where spreading occurred disorderly in randomly oriented ridges.