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Paleoproterozoic,High-Metamorphic,Metasedimentary Units of Siberian Craton

Acta Geologica Sinica(English Edition) 2009年第5期83卷 875-883页

作者： Lena URMANTSEVA olga turkina Institute of Geology and Mineralogy Siberian BranchRussian Academy of SciencesNovosibirskRussia

Sensitive, high-resolution ion microprobe zircon U-Pb ages of Paleoproterozoic, high-grade, metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet-biotite, hypersthene-biotite, and cordierite- bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4-3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show corerim textures in cathodoluminescence （CL） image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are：〉2.7, -2.3, and 1.95-2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga （Wan et al., 2006）. All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton.

关键词： zircon sensitive high-resolution ion microprobe U-Pb dating metasedimentary rocks,Paleoproterozoic Siberian Craton

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The Oldest Grey Gneisses and Tonalite-Trondhjemite Granodiorites in the Fennoscandian Shield: ID-TIMS and SHRIMP Data

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Open Journal of Geology 2020年第2期10卷 124-136页

作者： Tamara Bayanova Evgeniy Kunakkuzin Pavel Serov Ekaterina Steshenko Elena Borisenko Alexander Larionov olga turkina Geological Institute KSC RAS Apatity Russian Federation A.P. Karpinsky Russian Geological Research Institute (VSEGEI) St. Petersburg Russian Federation Institute of Geology and Mineralogy Siberian Branch RAS Novosibirsk Russian Federation

Genesis of the oldest continental crust retains a marked trace in the Earth’s evolution over its 4.5 Ga history. Despite ample isotope data on the role of the continental crust in the Earth’s evolution, there has been much debate on the origin of grey gneisses and tonalite-trondhjemite-granodiorites (TTG). Precise U-Pb (ID-TIMS) and SHRIMP data on single zircon for paragneisses and TTG (3158.2 ± 8.2 Ma) have indicated the Central-Kola and Belomorian (White Sea) megablocks of the Fennoscandian Shield to be 3.16 Ga and 3.70 Ga, respectively. The newly obtained ages of zircon from these megablocks indicate the origin of the discrete continental crust to be 3.16 and 3.70 Ga. It is close to the Nordsim zircon data on the Siurua TTG (Finland), which are 3.45 and 3.73 Ga in the core. The new summarized data on the Earth’s oldest rocks (basement and continental crust) indicate the younger age of the rocks in the Fennoscandian Shield as compared to those in Australia (Kronendonk et al., 2019).

关键词： Fennoscandian Shield Geochronology Hadean ID-TIMS SHRIMP TTG Grey Gneiss

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