New evidence of the Late Palaeozoic age of the quartzite-schist frame of the Ilmenogorsk complex (Southern Urals) |
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| Authors: | V G Korinevsky E V Korinevsky |
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| Institution: | 1. Mineralogy Institute of Mineralogy, Ural Branch, Russian Academy of Sciences, Miass, Russia
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| Abstract: | In the Ilmenogorsk metamorphic complex, Southern Urals, the Archean gneissic core and Riphean-Vendian quartzite-schist framing are traditionally distinguished. The age of the latter is not reliably determined. There were speculations about its possible Paleozoic age. Those are partially confirmed by isotopic data. The quartzite in the upper part of the section of schist strata detrital mineral grains were found, and they are similar to accessory minerals of the Kisegach Massif granitoids occurring among quartzite. The granitoids demonstrated to form phases of various age. It is assumed that the oldest of them (predating folding) could be intruded synchronously with sedimentation and serve as porvenance for the quartzite. The most informative of these minerals is monazite. Microprobe analyses results on monazite from quartzite and granite are given. Their REE distribution is demonstrated to be similar. This confirms the possibility of the granitoid erosion at the time of quartz sandstone deposition. Since the K-Ar age of granitoids Kisegach Massif is 252 ± 8 Ma, it was concluded that the Kyshtym quartzite-schist unit of Ilmeny has about the same age. |
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