RB-SR ISOTOPIC STUDIES OF MURUNTAU ORE DEPOSIT - ORE-BEARING METASOMATITES

The results of Rb-Sr isotopic studies of 4 metasomatite samples of different mineral composition and geological position in terms of oreformation succession are presented: from earliest quartz-felspar-biotite metasomatite up to chlorite enriched metasomatite of regressive stage. All four isochrones are parallel within the error limit with common decline corresponding to 272.6+/-3.8 m.y. The initial Sr isotope ratios in metasomatites (0.7138-0.7166) fall within the time interval characteristic to metasedimentary country rocks (273 m.y.) indicating the absence of external source of matter in the metasomatosis. The history of hydrothermal activity at Muruntau could be expressed as a sequence of separate activity impulses; 272.6+/-3.8; 256.2+/-6.4;230.2+/-3.5; 219.4+/-4.2 m.y.