Abstract
The paper presents the results of the frst LA-ICP-MS U-Pb geochronological studies of 60 perovskite grains from spurrite marbles of the Kochumdek contact aureole (East Siberia). Perovskite is a dominant accessory mineral of U- and Th-poor marbles, which formed at the contact with traps of the Kuz’movsky complex (southwestern margin of the Tunguska Syneclise). Chemically homogeneous perovskite is characterized by limited substitutions: Ti4+ > Zr4+ (up to 2.5 mol. % CaZrO3) and Ca2+Ti4+ > REE3+Fe3+ (up to 1.8 mol. % REEFeO3). Perovskite is the main host for Th (up to 1550 ppm), U (up to 450 ppm), Ti, Zr, and LREEs (La + Ce + Pr + Nd); the element incorporation ratios are KTh = 516–870 and КU = 374. The U-Pb isotopic age of perovskite of 248.0 ± 7.2 Ma is in agreement with isotopic age values of traps of the Kuz’movsky complex.
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