Tectonic Structure and Geodynamic Settings of Neoproterozoic Granitoid Magmatism of the Eastern Arctic
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Tectonic Structure and Geodynamic Settings of Neoproterozoic Granitoid Magmatism of the Eastern Arctic Corresponding Member of the RAS S. D. Sokolova, M. V. Luchitskayaa,*, and A. V. Moiseeva Received May 15, 2020; revised May 19, 2020; accepted May 20, 2020
Abstract—The correlation of Neoproterozoic granitoid magmatism of the New Siberian Islands, Wrangel Island, Chukotka, the Chukchi Borderland, and Northern Alaska indicates integrity of the Arctic Alaska– Chukotka microplate basement and the formation of the continental crust during the Timanian (Baikalian) orogeny. The age of inherited cores of zircons and the Nd model age point out the participation of the Mesoand, less frequently, Paleoproterozoic crust in the formation of the epi-Grenville Arctida continent. In the modern structure, Timanides extended from the Timan Range through the Polar Urals and Taimyr to Chukotka and Northern Alaska, framing the margins of the Baltics, Siberia, and North America continents. It is suggested that the geodynamic setting of Neoproterozoic granitoids for most of the microplate is supra-subduction continental margin, less frequently, rift-related at the late stages of the Timanian orogeny. The origin of the Grenville and Neoproterozoic–Timanian population of detrital and inherited zircons is explained by local provenance areas. Кeywords: tectonics, geodynamics, granitoid magmatism, geochronology, zircon, Eastern Arctic DOI: 10.1134/S1028334X20080206
The Arctic Alaska–Chukotka (AAC) microplate (microcontinent, terrane) has been identified in the Eastern Arctic; it occupies the area from the New Siberian Islands to Northern Alaska. A significant portion of the microplate is covered under the waters of the East Siberian and Chukchi seas (Fig. 1). The southern boundary of the microplate passes on Chukotka along the South Anyui suture and on Alaska, along the Kobuk–Angayucham suture. The northern boundary of the microplate is interpreted differently. Structurally, the microplate is divided into two parts [1]: the southern deformed part and the northern part without traces of Mesozoic deformations. The boundary goes along the front of Cenozoic overthrusts of the fold region in Brooks Range, the Wrangle-Herald frontal overthrust, and its western extension in the East Siberian Sea. Outcrops of the AAC basement are known on Wrangel Island, Eastern Chukotka, and Northern Alaska (Seward Peninsula and Brooks Range). All these objects are characterized by granitoids, as well as felsic volcanics in the age range of 750–550 Ma (single occurrences of 970 and 865 Ma). This work analyzes original and published data on Neoproterozoic granitoid magmatism of the Eastern a
Geological Institute, Russian Academy of Sciences, Moscow, 119017 Russia *e-mail: [email protected]
Arctic to explore its tectonic structure and geodynamic settings of formation. Northern Alaska. In Hub Mountain (Brooks Range) Proterozoic metamorphic rocks are intruded by granodiorite orthogneisses with U–Pb-age of 742 ± 6 and 750 ± 6 Ma [2]. The rare-element composit
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