Kroushev Dol is one of the important Pb-Zn ore deposits in the Madan ore district. The main subvertical ore vein, 1 to 3 m wide, is embedded in gneissic rocks and shows clear vertical zonation. The rich galena-sphalerite ores, formed in the upper levels (1100-650 m) under boiling conditions, are followed in dept (600-450 m) by a zone of barren quartz. Metasomatic marble hosted ore beds occur deeply (450-400 m). A long-prismatic crystal of barren quartz from the intermediate ore-free zone was studied in several cross and longitudinal plane polished sections. Total salinity of 4.0÷9.1 wt % NaCl eqv. was established by microcryometry. Homogenization temperatures range 350÷312°C (mode 340°C). The concentrations of 30 elements were determined by LA-ICP-MS in single fluid inclusions in several cross and longitudinal plane polished sections from the quartz crystal studied. The mol ratios are in the ranges: K/Na 0.053÷0.22; Ca/Na 0.016÷0.065; Mg/Na 0.002÷0.009 and Mn/Na 0.001÷0.010. Mn is a typomorphic element in the fluids, closely related to the pre-ore pyroxene skarns. Boron was also found (170 ppm). The ore elements concentrations are (mean values, ppm): Pb 29, Zn 70, Cu 16, As 34. Bi (5 ppm) and Sb (23 ppm) found systematically also in the galena crystals of the deposit were also detected. Some fluctuations and evolution of the chemical composition as well as some other features of fluid inclusions in radial and longitudinal positions in the crystal were established.
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