U-Pb датирование рудных ниобиевых минералов группы пирохлора (ильмено-вишневогорский карбонатит-миаскитовый комплекс, Южный Урал)

U-Pb dating of the pyrochlore-group minerals from the Nb-rare metal ore deposits of ilmeny-vishnevogorsky carbonatite-miaskite complex of the Ural fold region was carried out. To date the individual pyrochlore crystals were used a new technique of local U-Pb SHRIMP-II dating which was developed at the CIR VSEGEI (St.Petersburg). In the case of high-U pyrochlore (with more than 2.5 wt % UO2) a laser ablation and ICP-MS method was applied for U-Pb-dating. The studied isotope pyrochlore system indicates a multi-stage formation of rare metal niobium mineralization. The earliest age of ore formation (378 ± 4.9 Ma) is fixed by U-pychlore isotope systems of Potanino deposit. This stage of ore formation is probably associated with the final stages of the alkaline-carbonatite magmatic system crystallization. The next stages of ore formation (230 ± 1.5 Ma) are widely manifested in Vishnevogorsk and later on the Potanino deposit (217.2 ± 1.9 Ma) and were probably related to remobilization and redeposition of alkaline-carbonatite and rare metal substances.