Interpretation of geochronological data obtained by K-Ar, Rb-Sr and U-Pb methods for the same geological objects of western part of the Ukrainian shield

Explained are some new isotope data obtained by the U-Th-Pb, Pb-Sr and K-Ar methods for various minerals and rocks of the western part of the Ukrainian shield as the most studied region in geological respect. Presented are the results of determination of the Pb, Sr, Rb isotope composition, quantitative content of Pb, Th, 204Pb, U in gneisses, isochrones of isotope age of accessory minerals of the Podol'sk and Teterev metamorphic rocks, Berdichev and Zhitomir granites. The most ancient ages about 3-3.2 milliard years obtained by the U-Pb isochrone method for gross paragneiss samples probably correspond to the period of primary cristallization of the initial material being the source for the ancient sedimentary rock formation. These rocks remained closed systems in respect to U and Pb during the following alterations. The age of 2350 mln years and 2140 mln years obtained by the Pb-Sr method characterizes the period of metamorphism and the beginning of granitization. The ages obtained by the U-Th-Pb and isochronic methods for accessory minerals correspond to the period of formation of these minerals. Porphyry granites probably were formed due to supposed alkaline metasomatosis of granites manifestated locally. Their age determined by the Pb-Sr and K-Ar methods corresponds to the value of >700 mln years. Introduction of dikes of the main magnetism over faults is dated as approximately 1500 mln years