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Phanerozoic Tectonic Evolution of the Chukotka-Arctic Alaska Block: Problems of the Rotational Model Boris A. Natal’in Istanbul Technical University Components of the ChukotkaArctic Alaska block Alaska Arctic Alaska superterrane Seward Terrane York Mountains terrane Chukotka Bennett-Barrovia block Chukotka fold belt Nutesyn arc The Bennett-Barrovia block continues to Alaska as the Hammond subterrane, York Mountains terrane, and Nixon Fork terrane Proposed Boundaries of Arctic AlaskaChukotka Plate (dotted line) Late Jurassic, 150 Ma Lawver et al. 2002 1000 km Kotelnyi Severnaya Zemlya Kotelnyi Bol. Lyakhovsky 291±62 Sm-Nd 133-139 Ma K-Ar 122±7 K-Ar Younger than late Jurassic Gravity gradients Pushkarev et al., 1999 Geophysical data Puskarev et al., 1999 S Franke et al. (2004): - Blagoveschensk N basin is absent - the shelf of the East Siberian Sea is epicontinental platform Puskarev et al. (1999): - Low standing basement - Densities are characteristic for consolidated crust Bennett-Barrovia block: Basement Granites 699 Ma Granites 750 Ma Metamorphism 655-594 Ma Granites 705 Ma Orthogneiss 650 Ma Orthogneiss 681 and 676 Ma Correlation with Taimyr Bennett-Barrovia pre-collision volcanics – 633±25 Ma syncollisional granites – 750-699 (650?) Ma metamorphism – 630 Ma assimilated crust – 1.31.5 Ga (Nelson et al., 1989) and 0,8-1.0 (Karl et al., 1989) Devonian granites – 0.71.6 Ga Taimyr pre-collision volcanics – 630-615 Ma syncollisional granites – 630 Ma metamorphism – 655-594 assimilated crust – 0.84-1.1 Ga 1 6 2 3 5 4 Correlation of Paleozoic sections Barrovia (Sherwood, 1992) Taimyr and Severnaya Zemlya (Russia) Thick pile of the upper Proterozoic-Cambrian flysch Evaporites in the Ordovician and Upper Silurian and Devonian Early Paleozoic fossils are different Franklinian structures sandstone, tuffaceous sandstone, shale, conglomerate, lavas and dikes of basalt, andesite, and diabase Deformed Ordovician and Silurian slates Margin of N. America Ordovician to Silurian oceanic and magmatic arc rock assemblages Pre-late Devonian subduction related magmatic arc at the eastern edge of BB gravity magnetic Herman and Zerwick, 1998 The late Silurian-early Devonian collision of the Bennett-Barrovia block Devonian-early Carboniferous subduction zone along the southern margin of the Bennett-Barrovia block Visean 360 Ma 375 ± 11 Ma 376 ± 37 Ma εNd is +0.2 and -0.3 398-383 Ma euhedral zircons of 370-360 Ma 381 Ma Back arc basin of the Devonian arc Tanatap basin - deep water shale and fine grained turbidite - high-K andesitic tuffs with εNd -7 Alyarmaut - Calc-silicates, quartzite, mafic tuffs Belkovskyi-Nerpalakh Trough - Upper Devonian to Lower Carboniferous limestone, shale, sandstone, conglomerate, mafic dikes and sills Brooks Range - Devonian extensional basin (the Beaucoup F.) Position of continents is after Lawver et al. (2002); 390 Ma Carboniferous-Permian Wrangel Island - shallow marine Carboniferous limestones grading up into Permian slates (~2100 m) - basin slopes to the south Chukotka - Lower Carboniferous conglomerates grading up into arkose sandstones, shale, and limestones (4500 m) - Permian rocks are unknown - Source area is expected in the south - Source area have to be rich in granites Many km lithic turbidite mafic magmatism rifting 0.1-0.2 km shale, chert, sandstone stable shelf 4.5 km molasse orogeny Modified after Grantz et al. (1991) Carboniferous collision? Position of continents is after Lawver et al. (2002); 330 Ma Opening of the South Anyui ocean Position of continents is after Lawver et al. (2002)