Abstract
Quartzites and paragneisses of the Archean granulite series of the Anabar Shield (Siberian Craton, Russia) are described geochemically. The Sm-Nd isotope systematics of the rocks and the U-Pb age (SHRIMP II) and geochemistry of zircons from quartzites and paragneisses are studied. Newly formed zircons from quartzites display geochemical characteristics of the magmatic type and were produced by rock anatexis upon granulite-facies metamorphism. The Paleoproterozoic age of the latest detrital zircons, 2250 ± 24 Ma, constrains the maximum age of sedimentary rock deposition. The anatectic rims around detrital zircons were formed ca. 2000 ± 9 Ma ago. The time of deposition of the sedimentary protolith of gneisses and quartzites falls within the age interval of the above-mentioned dates and is tentatively accepted as 2.1 Ga. The presence of Paleoproterozoic metasedimentary rocks in the Daldyn Group implies the tectonic heterogeneity of the series and the existence of Paleoproterozoic rock bodies among the predominant Archean rock sequences.
Highlights
Siberian Craton is the largest Precambrian continent in the north of Asia
The basement of the Siberian Craton represents a Paleoproterozoic collage of Precambrian highly metamorphosed terranes [1,2,3], which is overlain by Mesoproterozoic to Lower Cretaceous sedimentary rocks and Mesozoic flood-basalts
Quartzite beds in the Daldyn Group occur in association with the two-pyroxene plagiogneisses, which areconsistent consistentininchemical chemicalcomposition compositionwith withandesite andesite quartz diorite, with a U-Pb zircon which are oror quartz diorite, with a U-Pb zircon ageage of 2960 ± 22 Ma [7]
Summary
Siberian Craton is the largest Precambrian continent in the north of Asia. The basement of the Siberian Craton represents a Paleoproterozoic collage of Precambrian highly metamorphosed terranes [1,2,3], which is overlain by Mesoproterozoic to Lower Cretaceous sedimentary rocks and Mesozoic flood-basalts (traps). The current understanding of the age and structure of the Siberian cratonic basement has been outlined mostly through studies of exposed rocks in the Anabar and Aldan shields and the Olenek, Kan, Birusa, and Sharyzhalgai uplifts (Figure 1). According to a number of studies, the Siberian craton is composed of several Archean and Early. Proterozoic superterranes (Tungus, Anabar, Aldan, Stanovoy) that are believed to have assembled into a single structure and stabilized at 1.8–2.1 Ga. Superterranes are suggested to have an ancient granulite-gneiss or granite-greenstone basement. The assembling event is marked by a widespread collision-related granulite metamorphism and collisional and post-collisional granitic magmatism [1]
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