U-Pb Isotopic Dating of Zircons (SHRIMP-II) from Granulites of the Ol'khon Region of Western Baikal Area

摘要

Based on the first isotopic geochronological data obtained by the classic U-Pb method by zircons [1 -3], it was established that magmatic and metamorphic rocks of the Ol'khon region are of Early Paleozoic age. The age of granulite metamorphism of the Chernor-udskaya zone rocks spreading as a narrow band (with a width of <1 km) along the boundary of the Siberian Craton was 485 ± 5 Ma. Data of the SHRIMP ion microprobe for U-Pb isotopic dating of zircons [4, 5] confirmed previously obtained results: age estimations were 507 ± 8 Ma, for granulites in the northeastern part of the Chernorudskaya zone (Khadarta Peninsula) and 498 + 7 Ma, for the Khoboi Cape (Ol'khon Island). However, problems concerning age estimations for the protolith of these rocks remained unsolved. Our study is aimed at solution of these problems.