RADIOMETRIC AGE OF HYPERACIDIC VOLCANISM IN LATE-OROGENIC TROUGHS OF THE CHATKAL-KURAMA ZONE, CENTRAL TIEN-SHAN

The number and age of hyperacidic volcanism events in late-orogenic tr oughs of the Chatkal-Kurama structural zone are discussed on the basis of the radiometric dating. All K-Ar data available are used, includin g 90 original age determinations. The results of Rb-Sr dating obtained for five liparitic and trachyliparitic volcanic bodies of the region are represented. The reliability of the radiometric data is analyzed. The origin of most hyperacidic volcanic bodies of the region is shown to occur in Early Permian (Asselian). The occurrence of younger (P-2-T -1) acidic volcanics, which is suggested in the traditional scheme of the evolution of volcanism in the region, is not confirmed by radiomet ric data. The materials presented suggest pre-Asselian (C-2?) hyperaci dic volcanics in the region.