MINERALOGY AND FLUID INCLUSION STUDY OF POLYMETALLIC VEINS IN THE MADJAROVO ORE FIELD, EASTERN RHODOPE, BULGARIA

The formation of the Madjarovo polymetallic ore deposit is closely rel ated to Paleogene magmatism of intermediate character represented by s ubvolcanic and volcanic rocks. Six stages of vein type mineralization were established: 1. quartz-pyrite-chalcopyrite with Bi-sulphosalts; 2 . quartz-hematite-chlorite with gold; 3. quartz-galena-sphalerite; 4. quartz-barite-chalcedony with Sb-sulphosalts; 5. quartz-arsenic sulpho salts; 6. calcite-siderite. Ag-bearing galena and Fe-poor sphalerite a re the main minerals. Galena of early formation is Bi-bearing, while i n late stages it carries more Sb. Gold was found in two generations in different parageneses. The ''early'' gold is Ag-poor and related to h ematite, while the ''late'' one is Ag-rich and closely associated with quartz and sulphosalts. Three groups of sulphosalts were established: Se-bearing Bi-sulphosalts; Sb-sulphosalts, a part of them Cl-bearing, and As-sulphosalts with more or less Ag. Fluid inclusion data obtaine d in quartz, amethyst, sphalerite and barite from several representati ve ore veins show formation temperatures in the range of 370-degrees t o 150-degrees-C for different stages of mineralization. Evidence of bo iling fluids suggests pressures of 70 to 180 bars which correspond to an average depth of mineralization near 1.000 m. The low salinities of the fluids (a/v 3.5 eq. wt% NaCI) indicate influx of meteoric waters during mineralization. On the basis of mineralogical and fluid inclusi on data physicochemical conditions and source of the ore forming fluid s are discussed.