GEOCHRONOLOGY OF THE CHUKTUKON CARBONATITE MASSIF, CHADOBETS UPLIFT (Krasnoyarsk Territory)
D.A. Chebotarev1, A.G. Doroshkevich1,2, V.V. Sharygin1,3, D.S. Yudin1,3, A.V. Ponomarchuk1, S.A. Sergeev4
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakh'yanovoi 6a, Ulan-Ude, 640047, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
4A.P. Karpinsky Russian Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
Keywords: Geochronology, alkaline magmatism, carbonatite, weathering crust, perovskite, monazite, rippite, Chuktukon massif, Chadobets uplift
Abstract
We present results of U-Pb (SHRIMP II) and Ar-Ar geochronological study of the rocks of the Chuktukon massif, which is part of the Chadobets alkaline-carbonatite complex, and of the weathering crust developed after them. Perovskite from picrites and monazite from the weathering crust were dated by the U-Pb (SHRIMP II) method, and rippite from carbonatites, by the Ar-Ar method. Rippite has first been used as a geochronometer. The estimated ages (252 ± 12 and 231 ± 2.7 Ma) testify to two magmatism pulses close in time (within the estimation error) to the stages of alkaline magmatism in the Siberian Platform (250-245 and 238-234 Ma). These pulses characterize, most likely, the processes accompanying and completing the activity of the mantle superplume that formed the Siberian Igneous Province at 250-248 Ma. The monazite-estimated age (102.6 ± 2.9 Ma) is the time of formation of the ore-bearing weathering crust on the massif rocks.
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