Early Precambrian high-grade metamorphosed terrigenous rocks of granulite-gneiss terranes of the Sharyzhalgai uplift (southwestern Siberian craton) |
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| Institution: | 1. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;2. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;1. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;2. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;1. Department of Geology, Rhodes University, Artillery Road, Makhanda (Grahamstown), 6139, South Africa;2. Department of Earth, Environmental and Planetary Sciences, Rice University, 6100 Main Street, Houston, TX 77005, United States of America;3. Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana;1. Schmidt Institute of Physics of the Earth, RAS, 10 B. Gruzinskaya St., Moscow 123995, Russian Federation;2. Institut des Sciences de la Terre, Université Grenoble Alpes, CNRS (UMR5275), 1381, rue de la Piscine, 38610 Gieres, France;3. Institute of Mechanics, Lomonosov Moscow State University, Russian Federation;4. Lomonosov Moscow State University, Department of Physics, Russian Federation;5. Fersman Mineralogical Museum RAS, Bldg. 2, 18 Leninsky Prospekt, Moscow, Russian Federation;6. Institute of Volcanology and Seismology FEB RAS, 9 Piipa Blvd., Petropavlovsk-Kamchatsky 683006, Russian Federation;1. State Key Laboratory of Continental Tectonic and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;3. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China |
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| Abstract: | We present results of geochemical and Sm-Nd isotope studies of high-grade metaterrigenous rocks of the Kitoi and northwestern Irkut terranes of the Sharyzhalgai uplift on the Siberian Platform in comparison with paragneisses of the southeastern Irkut terrane. The metasedimentary rocks of the first region are high-alumina garnet-sillimanite-cordierite-bearing paragneisses; their protoliths were mostly mudstones and pelitic mudstones by major-element composition. The low-alumina biotite gneisses of the Kitoi terrane formed, most likely, from magmatic protoliths similar in petrochemical features to intraplate volcanics. The major factor controlling the composition of the studied high-alumina paragneisses is precipitation of most of incompatible trace elements in the clay fraction of sediments, as evidenced from the positive correlation between trace-element and Al2O3 contents. The Cr and Ni contents, showing a positive correlation with MgO and no correlation with Al2O3, are an indicator of the contribution of the mafic-source material to the formation of high-alumina rocks. The contribution of a mafic source-derived material to the formation of terrigenous rocks increases in passing from Kitoi to northwestern Irkut terrane. The high-alumina and garnet-biotite paragneisses of the southeastern Irkut terrane are similar in trace-element patterns to the analogous rocks of the Kitoi terrane and northwestern part of the Irkut terrane but show higher Th contents and a distinct negative Eu anomaly related to the change in the composition of the felsic source. The participation of felsic potassic igneous rocks in the formation of the southeastern terrigenous sediments is consistent with their deposition after the Neoarchean collision processes (metamorphism and granite magmatism), whereas sedimentation in the Kitoi and northwestern Irkut terranes preceded them. The Sm-Nd isotope characteristics indicate that the latter sediments formed mostly as a result of the erosion of the Paleo-Mesoarchean crust, whereas the metasediments of the southeastern Irkut terrane formed with the participation of Paleoproterozoic juvenile rocks. Thus, the variations in the trace-element and isotope compositions of the high-grade metamorphosed terrigenous rocks reflect recycling and growth of the continental crust of the Sharyzhalgai uplift during the Neoarchean-Pa- leoproterozoic transition. |
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