Introduction
This review paper deals with the mylonitic gneisses of the Rhodope Massif. They were deformed under medium-pressure amphibolite-facies conditions (biotite-garnet-staurolite parageneses are common in metapelites) and are examined in the light of results and concepts developed since the 1980. Although this special volume is dedicated to Greece, it is impossible to ignore the work carried out in the Bulgarian Rhodope. It is also impossible to cite all references -many are considered to be obsolete. Consequently, this review unavoidably reflects the author's opinion. For instance, we follow Ricou et al. [1998] to integrate the Greek and much of the Bulgarian parts of the so-called Serbo-Macedonian Massif [Kockel and Walther, 1965] to the Rhodope (Fig. 1). This attribution is a return to initial definitions of units, which bordered the Rhodope Massif along its southwestern boundary with the Vardar Zone [Kossmat, 1924].
We first summarize the evolution of concepts and discussions on the Rhodope since the earliest geological explorations in the area. We then place emphasis on recent discoveries and progress, in particular those related to geochronology, to definitively assert that the Rhodope is a deformed segment of the Alpine-Himalayan suture and collision system. Reviewing these data yields timing of deformational and thermal events that controlled the geodynamic evolution of the area. A synmetamorphic duplex system includes ultrabasic and basic rocks traditionally lumped under the term "ophiolites" and a Jurassic magmatic arc. These rocks were partly subducted to Ultra-High-Pressure (UHP) metamorphic conditions and retrogressed to amphibolite-facies during Cretaceous times. Subsequent crustal thickening led to syn-orogenic extension and extrusion/exhumation of the metamorphic rocks already brought back to the surface in Latest Cretaceous-Paleocene, at least in the northeastern Rhodope. The present-day structure results strongly from these combined large-scale thrusting and pervasive exhumation tectonics. A Late Eocene [Priabonian; Černjavska, 1977] marine transgression marks isostatic equilibrium of the belt in Early Tertiary, until a major extensional event reworked the Rhodope Metamorphic Complex during the Eocene and the Oligocene. This event, associated with voluminous magmatism, is responsible for synmetamorphic reworking of the older gneiss sytem in major, low-angle detachments. A second extensional event produced grabens related to later Aegean extension.
Figure 1. Location of the Rhodope in the Alpine Mediterranean chains.
The high-grade Rhodope metamorphic complex is limited upward by roof greenschists below the European, Carpatho-Balkanic units. It is limited at the Rhodope-Vardar boundary zone by the different, western greenschists. Adapted from Kounov et al. [2010].