| Инд. авторы: | Turkina O.M., Sukhorukov V.P., Sergeev S.A. |
| Заглавие: | Mesoarchean bimodal volcanic rocks of the Onot greenstone belts, southwestern Siberian craton: Implications for magmatism in an extension/rift setting |
| Библ. ссылка: | Turkina O.M., Sukhorukov V.P., Sergeev S.A. Mesoarchean bimodal volcanic rocks of the Onot greenstone belts, southwestern Siberian craton: Implications for magmatism in an extension/rift setting // Precambrian Research. - 2020. - Vol.343. - Art.105731. - ISSN 0301-9268. |
| Внешние системы: | DOI: 10.1016/j.precamres.2020.105731; РИНЦ: 43273635; WoS: 000532835600020; |
| Реферат: | eng: This paper shows that Mesoarchean bimodal felsic and mafic metavolcanic rocks of the Onot greenstone belt (Sharyzhalgay uplift, the southwestern margin of the Siberian craton) formed as a result of rifting of Paleoarchean continental crust. Evidence for this comes from U-Pb zircon ages, whole-rock geochemical and Nd isotope data and Hf-in-zircon isotope data from a metarhyolite-basaltic unit. The over 80 km long Onot greenstone belt consists of tectonic sheets composed of metasedimentary-volcanogenic and tonalite-trondhjemite-granodiorite (TTG) rocks thrusted to the southwest onto high-grade rocks of the Kitoy terrane. The greenstone sequence includes a bimodal metavolcanic unit overlain by metavolcanogenic-sedimentary units. The felsic volcanic rocks formed at similar to 2.88 Ga and were metamorphosed at 660-690 degrees C and similar to 6 kbar during the Late Paleoproterozoic. The high-Fe metarhyolites are enriched in the REE and HFSE and are compositionally similar to felsic volcanic rocks of Archean greenstone belts with lower La/Yb and Zr/Y (FIIIa and FIIIb types after Hart et al., 2004), and A-type granitoids. The high- and low-Ti metabasalts (amphibolites) possess geochemical affinities to both subduction-related basalts and continental flood basalts contaminated by crustal material. The metarhyolites yielded negative epsilon(Nd)(t) values (-3.8 to -0.8). Their zircons yielded negative to positive epsilon(Hf)(t) values (-8.5 to +1.1). The isotopic data suggest melting of heterogeneous crust, consisting of Paleoarchean plagiogneisses of the TTG basement complex and a juvenile source. The contribution of a mafic source resulted in enrichment of metarhyolites in FeO, MgO and TiO2. The crustal melting probably occurred at shallow depths at 2-4 kbar and at high temperatures higher than 900 degrees C. The coeval formation of Onot basalts and low-P - - high-T felsic melts could be triggered by decompressional mantle upwelling and subsequent extension and thinning of the subcontinental lithosphere. Worldwide, evidence for extension/rifting comes from Meso-Neoarchean mafic dikes and coeval intra-plate bimodal basalt-rhyolite volcanism. The events of extension/rifting and the formation of subcontinental lithospheric mantle suggest formation of stable and rheologically rigid continental plates.
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| Ключевые слова: | PILBARA CRATON; CONTINENTAL-CRUST; SM-ND; LU-HF; SHARYZHALGAI-UPLIFT; U-PB; TRACE-ELEMENT GEOCHEMISTRY; A-TYPE GRANITES; HF ISOTOPE COMPOSITION; Stabilization of subcontinental lithospheric mantle; Nd and Hf isotopes; Geochemistry; U-Pb zircon age; Onot greenstone belt; RE-OS; |
| Издано: | 2020 |
| Физ. характеристика: | 105731 |