VOLUME 5 (1)/March 1975

The distribution of the ore-forming elements in the Balkan Peninsula follows the evolution of residual continental slabs and adjacent orogenic girdles as delineated by ultramafic and mafic rocks of changing age and loci of consolidation. The continental slabs, mainly metamorphic, have been subjected to a gradual thickening and uplift of no less than 20 km since early Precambrian times. In agreement with their crystal chemistry ore-forming elements such as Cr, Fe, Mn, Cu, Mo and some Hg, Au and Ba became enriched in the ultramafic and mafic suites, whereas elements like Pb, Zn, Sb and some Cu, Mo, W, Bi and Ba concentrated in the residual continental masses as a result of a temporal and lateral mobilisation of these elements in different levels of the Earth's crust and the mantle. The trend of mobilisation is first outward then toward the continental slabs with a general tendency the Meso-Cenozoic mineralizations of the Cu-Mn-Mo, Pb-Zn and Sb-(Tl) types to develop gradually to the west and south of the Pontian depression.

E. Dimitrova, D. Bahneva, B. Mavrudciev, B. Kamenov. Y. Yanev. Magmatic Formations in Bulgaria. In the present paper the results of the detailed petrographic study of the igneous rocks of Bulgaria are summarized. The magmatic development and its relationship to the tectonic is discussed from the formation analysis viewpoint. Representatives of three major structural types are known on Bulgarian territory: platforms (Moesian 'plate'), folded zones (the Balk anides and Srednogorie, the Sakar-Strandža zone included), and activation zones (the Rhodope massif). Three main stages in the tectonic development of the folded zones are determined: geosynclinal, inversional and consolidation stages. The inversional stage is subdivided into early and late substages. In the course of the formation analysis the definitions of Yu. A. K u z n e t c o v (1964) have been used. Two classes of igneous rock associations (formations) have been determined: effusive and intrusive ones. Within the folded zones of Bulgaria the following formations are characterized: spilite-diabase and ultramafic-alpinotypic (geosynclinal stage), basalt-andesitic and gabbro-plagiogranitic (early inversional stage), granit-granodioritic (batholitic), gabbro-diorit-granodioritic and gabbro-monzonite-syenitic (late inversional stage), and basalt-rhyolitic and alkaline gabbro-syenitic (for the consolidation stage). The activization zones are characterized by the andesite-trachyandes iterhyolitic, the rhyolitic, and the gabbro-monzonite-syenitic formations.

The paleogeographic and facial conditions during the Paleogene in the East Rhodopes and their significance for the formation of sediments is analysed. In most cases the conditions in the basin are typified by the presence of three well-individualized facial zones: littoral, reefy and internal.
   The carbonate forming processes were of reef character and occurred in the confines of the reefy facial zone. According to its shape the latter was of linear (coastal or barrier) and areal type.
   The clay-forming processes developed in specific conditions: in the confines of the internal facial zone, by dominant terrigenous sedimentation and presence of well-developed reef barrier along the land which supplied the terrigenous material.
   Pure volcanic tuffs formed thick deposits also in the confines of the internal facial zone, independently of the depth of the basin, in the presence of intensive volcanism and a well-developed reef barrier along the neighboring Iand.
   Intensified coarse terrigenous (psephitic and psammitic) sedimentation occurred in the confines of the littoral facial zone and particularly in trough-like depressions, intermontane basins and graben-like depressions characterized by intensive subsidence.