Metaophiolite association in the Rhodope Massif as a stratigraphical and structural marker

The paper is a brief survey of the geological setting and metamorphism of the Metaophiolite Association within the metamorphic basement of the Rhodope Massif on Bulgarian territory. It emphasizes the stable stratigraphic level of metaophiolites in the lower layers of the Variegated Formation of the Rhodopian Supergroup. Usually, they crop out in deep tight synclinal folds between anticlinal structures. On the basis of new geological arguments and lithological analysis that take into consideration the syn-metamorphic deformation and metamorphic changes, an attempt is made to reconstruct the primary lithostratigraphy of the metamorphic complex. In addition, some corrections of the current stratigraphic column and geological map of the Rhodope Massif are also made. The view that fold structures dominate instead of thrusts is affirmed. Geological relationships assume that the most likely way for the integration of serpentinites into the Variegated Formation of the Rhodopian Supergroup was obduction of fragments of serpentinized oceanic crust onto an ancient continent consisting of gneisses of the Prarhodopian Supergroup. The ophiolites have undergone various metamorphic changes: hydrothermal ocean and regional metamorphism in the amphibolite facies, culminating in migmatization. It is suggested that eclogitization occurred in local shear zones within the crust, and not along thrust surfaces or within subduction zones to mantle depth. The Metaophiolite Association is an important marker for the stratigraphic correlation of the metamorphic terranes as well as for the structural and metamorphic evolution of the Rhodope massif basement.