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U-Pb age of detrital zircons from neoproterozoic placers of the Erementau-Niyaz massif as a reflection of stages of Precambrian tectono-magmatic evolution of northern Kazakhstan |
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| Authors: | V P Kovach A V Ryazantsev A A Tretyakov K E Degtyarev E V Tolmacheva Kuo-Lun Wang A B Kotov Sun-Lin Chun Bor-Min Jahn |
| Institution: | 1. Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034, Russia 2. Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia 3. Institute of the Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei, 11529, Taiwan 4. Department of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 106, Taiwan |
| Abstract: | A typical feature of the Precambrian complexes of the Kokshetau, Ishkeolmess, Erementau-Niyaz, and Aktau-Dzhungaria massifs of Northern and Central Kazakhstan is the presence of the end Mesoproterozoic-beginning of the Neoproterozoic quartzite-schist sequences in these sections. The lower and upper parts of these sequences are mostly composed of schists with interlayers of quartzites and marbles and of quartzitic sandstones, respectively. It is suggested that the quartzite-schist sequences represent the sub-platform cover of a large continental block and were formed in the regressive basin with widely abundant facies of submarine deltas and a littoral shoal. The presence of horizons and the lenses enriched in zircon-rutile heavy concentrate with the amount of accessory minerals of 10-70% characterizes the quartzite-schist sections of the Kokshetau and Erementau-Niyaz massifs. The U-Pb age of zircons from one such locality in the central part of the Erementau-Niyaz massif was analyzed by LA-ICP-MS. The Concordia ages of zircons are in the intervals 1041 ± 13-1519 ± 14, 1623 ± 14-1931 ± 14, and 2691 ± 14-2746 ± 14 Ma. One age was 2850 ± 14 Ma. The age distribution is characterized by clear peaks of 1.08, 1.20. 1.34, 1.46, 1.65, 1.89, and 2.70 Ga and weak peaks of 1.13 and 1.68 Ga. The age of the majority of zircons ranges from 1309 ± 14 to 1519 ± 14 Ma. Our data indicate that mostly Neoproterozoic rocks with a subordinate role of Paleoproterozoic and Neoarchean complexes served the feeding sources for the quartzite-schist sequence of the Erementau-Niyaz massif. The Mesoproterozoic and Paleoproterozoic events identified for the detrital zircons of the Erementau-Niyaz massif are completely manifested only in Laurentia. In the first approximation, these events coincide with the assembly and breakup of the Columbia/Nuna supercontinent (～1650–1580 and 1450–1380 Ma) and assembly of the Rodinia supercontinent (1300–900 Ma). |
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