Tertiary magmatism in SW Bulgaria and Eastern FYR Macedonia: geochemistry, geodynamic setting and relation to mineral resources

In the frame of an international joint research project SCOPES IZ73Z0-128089 of the Swiss National Science Foundation, we started a collaborative study of the geological processes in SW Bulgaria and Eastern FYR Macedonia and Serbia that are responsible for the Tertiary magmatism and the formation of important copper, gold, iron and lead/zinc ore deposits. The project is leaded by Dr. A. von Quadt and a team of the Institute of Geochemistry and Petrology, ETH-Zurich, Switzerland. It comprises three additional teams from Serbia (Belgrade University), FYR Macedonia (Stip University) and Bulgaria (Geological Institute of the Bulgarian Academy of Sciences).
   The planned major tasks of the project are four: i) Fluid processes at the magmatic to hydrothermal transition in porphyry-style Cu-Au-(-PGE) deposits and in meso- and epithermal deposits in Eastern Serbia, FYR Macedonia (e.g. Buchim, Ilovitza, Kadiitza) and Western Bulgaria/Central Rhodopes; ii) Geochronology, magmatism and large-scale metallogeny of the Cretaceous ABTS belt and the Paleogene Serbian-Macedonian-Rhodope zone; iii) Deposit-scale geochronology, magma characteristics and mineralization; iv) Impact of the mining activity on environment and the social life.
   Our work as part of the project is concentrated on the second and third tasks and will build the basis of two PhD theses. On the regional scale, together with our Bulgarian supervisors and consultants from the FYR Macedonian team, we want to understand the geodynamic environment and the generation of mineralizing magmas, using extensive radiometric age dating, igneous geochemistry and petrology. We started the sampling of magmatic and volcano-sedimentary rocks along two main E-W transects: i) from the region of Kyustendil in SW Bulgaria trough the whole Kratovo-Zletovo magmatic complex (transect Ruen-Kratovo-Zletovo); ii) from Simitli and Petrich region in SW Bulgaria to Buchim and Alshar in FYR Macedonia (transect Sandanski-Alshar). The sampling aims to include the oldest and the youngest varieties, as well as representative samples for the whole geological succession. So we can test some existing ideas for the zonation of magmatism and mineraliztion along NW-SE structures and provide new data for a substantiated geodynamic model of the Tertiary evolution of the region.
   On the scale of a single ore-forming magmatic-hydrothermal systems we will concentrate on two or three important deposits (e.g. Buchim, Ilovitza) applying mainly the following methods: i) precise age dating (Ar-Ar on magmatic and alteration minerals, Re-Os on molybdenite, U-Pb on zircons from magmatic dykes that bracket the ore formation); ii) stable isotope analyses; iii) isotope-geochemical tracing (Sr, Pb and Nd). They will help us to constrain or to refine the genetical models of the deposits. Analytical works will be performed mostly in the labs of ETH, Zurich and in the new LA-ICP-MS laboratory at the Geological Institute of BAS.
   First field results, isotope-geochronological, isotope-geochemical and petrological data will be presented and discussed during the CBGA-Congress.