In recent years the Rhodope Massif has risen in prominence due to the discovery of microdiamond in garnet from metapelites in the Greek Rhodope Mts., establishing the region as a rare UHP province. This study is the first to establish that the UHP conditions continue through to Bulgaria, owing to the discovery of a microdiamond inclusion in garnet from metapelite in the vicinity of the town of Chepelare in the Bulgarian Central Rhodope Mts. This UHP metapelite outcrops within the Chepelare Shear zone (CSZ), a ‘melange’ of meta-igneous and meta-sedimentary rocks located on the edge of the Variscan Arda dome, one of three metamorphic core complexes that dominate the regional geology. Through a combination of petrographical and geochemical analysis, the metamorphic conditions experienced by these UHP samples have been reconstructed. Two populations of metabasic units in the Central Rhodope Mts. were identified in this study; one within the melange units of the CSZ, and one as boudins in orthogneiss overlying the CSZ. The boudins are shown to be retrogressed eclogites with a suprasubduction zone origin unrelated to the metabasic units within the CSZ. Correlations are observed with Neoproterozoic/Ordovician metabasic samples previously reported from the Eastern Rhodope Mts., which represent remnants of the Variscan Orogeny in this region. Metabasic melange samples within the CSZ instead have an N-MORB affinity, and display no evidence of a shared P-T history with the UHP metapelites. Sm-Nd garnet dating of the metapelites from the CSZ performed in this study indicates a Late Cretaceous age for the UHP metamorphic event. This is significantly younger than previously reported ages, and suggests a formation history associated with the northwards subduction of the Vardar Ocean beneath the Moesian Platform during the Late Mesozoic. The present day structure of the massif is the result of complex Cenozoic tectonics following post orogenic extension and formation of the metamorphic core complexes that are observed across the Rhodope Massif
