U-Pb Geochronology of Migmatite Leucosomes Based on Zircon SIMS Measurements and Correlation with TIMS-ID Data on Monazite

摘要

The use of an advanced analytical method for the local study of isotope systems requires control of results by traditional and tested methods and approaches. This is particularly true of local U-Pb analysis of metamorphic zircons with poorly developed or thin metamorphogenic rims. Repeated measurements for statistics, which is usually necessary during mass spectrometric analysis with application of secondary ions (SIMS), are objectively difficult for such zircon, while the correct TIMS-ID (isotopic dilution) dating is problematic. At the same time, even a limited number of local measurements in different generations (and rims) of zircons may yield useful information and reveal real stages in substance evolution. This is evident from local SIMS dating of zircons from migmatite leucosomes substantiated by U-Pb geochro-nological data (TIMS-ID) on monazite.