Paleomagnetism of the Late Cretaceous ignimbrite from the Okhotsk-Chukotka Volcanic Belt,Kolyma-Omolon Composite Terrane: Tectonic implications |
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| Institution: | 1. Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano, via Mangiagalli 34, 20133 Milano, Italy;2. Dipartimento di Scienze, Università degli Studi Roma Tre, 00146, Rome, Italy;3. Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA;1. Diamond and Precious Metals Geology Institute, Siberian Branch of the Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677980, Russia;2. Research Geological Enterprise ALROSA, Chernyshevskoe Shosse 16, Mirnyi, 678174, Russia;3. Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russis;1. Atmospheric Sounding Station-El Arenosillo, Atmospheric Research and Instrumentation Branch, National Institute for Aerospace Technology (INTA), Crta. Huelva Matalascañas, km 34, 21130 Mazagón, Huelva, Spain;2. Department of Earth Observation, Remote Sensing and Atmosphere, National Institute for Aerospace Technology (INTA), 28850 Torrejón de Ardoz, Spain |
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| Abstract: | New Late Cretaceous paleomagnetic results from the Okhotsk-Chukotka Volcanic Belt in the Kolyma-Omolon Composite Terrane yield stable and consistent remanent directions. The Late Cretaceous (86–81 Ma) ignimbrites from the Kholchan and Ola suites were sampled at 19 sites in the Magadan area (60.4° N, 151.0° E). We isolated the characteristic paleomagnetic directions from 16 sampled sites using an alternating field demagnetization procedure. The primary nature of these directions is ascertained by dual polarities and positive fold tests. A tilt-corrected mean direction (D = 42.8°, I = 84.7°, k = 46.0, α95 = 10.0°) yields a paleomagnetic pole of 66.7° N, 168.5° E (A95 = 18.8°) which appears almost identical to the 90–67 Ma pole reported from the Lake El’gygytgyn area of the Okhotsk-Chukotka Volcanic Belt (Chukotka Terrane). This consistency suggests that the Kolyma-Omolon Composite Terrane and Chukotka Terrane has acted as a single tectonic unit since 80 Ma without any significant internal deformation. Accordingly, we calculate a combined 80 Ma characteristic paleomagnetic pole (Long. = 164.7° E, Lat. = 68.0°, A95 = 10.9°, N = 12) for the Kolyma-Omolon-Chukotka Block which falls 16.5–17.5° south of the same age poles from Europe and East Asia. We ascribe this discrepancy in pole positions to tectonic activity in the area and infer a southward displacement of 1640 ± 1380 km for the Kolyma-Omolon-Chukotka Block with respect to the North American and Eurasian blocks since 80 Ma; more than 260 km of it is attributed to tectonic displacement in the Arctic Ocean due to the opening of the Canadian Basin. |
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| Keywords: | Tectonics Paleomagnetism Late Cretaceous Eurasia Okhotsk-Chukotka Volcanic Belt Kolyma-Omolon-Chukotka Block |
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