VOLUME 17 (6)/December 1987

The Virini-Pessani-Dadia area, NE of Alexandroupolis, W. Thrace, is made up of metamorphic rocks and in a major extent of Tertiary volcanic and sedimentary rocks. In the volcano-sedimentary association fine grained sandstones alternating with thin bedded pelites are overlain by mafic and felsic volcanics of Eocene-Oligocene age. These are intruded by quartz-feldspar porphyries. Felsic volcanics, the majority of which are of dacitic-rhyodacitic composition, comprise pyroclastic flow and fall deposits and lava flows and domes. All petrological and geochemical data indicate that the Eocene lavas are of andesitic composition and show characteristics of orogenic volcanic series of continental margins rather than of island arcs. Two types of mineralization can be distinguished in the explored area: a) Stratabound Zn-Pb-Cu semimassive mineralization occurring in a series of calcareous sandstones, which close to their contacts with felsic porphyries are propylitized and b) Epigendic fracture-filling Pb-Zn-Cu mineralization in epidote and chlorite-bearing sandstones. The low areal extent of the propylitized sandstones and the absence of any indication for the existence of massive ore at depth, are considered unlikely that the clastic sequence of the studied area is favourable to be the host of economic polymetallic ores.

The Priabonian-Oligocene magmatism in the Eastern Rhodope Mts. took place during an interval of 11-12 Ma (37-25.5 Ma). Fauna-dated Priabonian and Oligocene sediments are interbedded by lava flows (dated 37-35 Ma and 34-30 Ma, respectively) which corresponds to the age of the Priabonian-Oiigocene boundary as proposed by O d i n (34 ±1/2 Ma) and C a v e I i e r & P o m e r o I (35.7 ±0,4). The youngest, subvolcanic dike swarms are intruded at the Lower-Upper Oligocene boundary (28-25.5 Ma). Small hypabyssal intrusions are found to be contemporaneous with the volcanic activity as a whole. Three of them are dated 31.5-33 Ma.