U-PB ISOTOPE AGING OF LOW-CRUST XENOLITES

U-Pb isotope system has been studied in accessory zircons from ''crust xenolites'' being the matter of low horizons of Earth crust. The xeno lites are sampled from Mesozoic alkaline basalts of Akhaggara (Central Sahara) and Near-Sayan. In the both regions studied the low crust has Early Proterozoic age (2035+/-10 and 1940+/-10 Ma). This age correlat es well with the age of granulites from neighbor regions. The study of U-Pb isotope system of accessory zircons from melanocratic inclusions in I-granitoids of Kazakhstan reveal the inclusions (autoliths) are s yngenetic with the granitoid magma itself.