THE CHUKCHI SEGMENT OF THE UDA-MURGAL AND OKHOTSK-CHUKOTKA VOLCANIC BELTS: AGE AND TECTONIC ENVIRONMENT
P.L. Tikhomirov1,2, N.V. Pravikova1, Ya.V. Bychkova1
1Lomonosov Moscow State University, Leninskie Gory 1, Moscow, 119991, Russia
2North-East Interdisciplinary Scientific Research Institute, Far Eastern Branch of the Russian Academy of Sciences, ul. Portovaya 16, Magadan, 685000, Russia
Keywords: Magmatism, geochronology, geochemistry, northeastern Asia, Uda-Murgal belt, Okhotsk-Chukotka belt
Abstract
We present new data on the geology, geochronology, and geochemistry of volcanic complexes of the Uda-Murgal and Okhotsk-Chukotka belts that expose on the left bank of the Anadyr’ River in its middle course. The structural relationships between the stratons, supplemented by the U-Pb and 40Ar/39Ar dates of volcanics, indicate at least three compression events at this segment of the Pacific margin during the Cretaceous: pre-Aptian, early Albian, and late Turonian. The complexes of the Uda-Murgal and Okhotsk-Chukotka belts are separated by an early Albian unconformity, but the other two unconformities are also well pronounced. The studied segment of the Uda-Murgal belt evolved in the ensialic island arc setting till the Barremian. In the Aptian, after the accretion of the island arc to the continent, volcanism reactivated on the Andean-type margin. The main geochemical difference between the Uda-Murgal and Okhotsk-Chukotka belts is the different volume portions of silicic rocks. The less significant difference in the contents of trace elements indicates a change in the composition of the mantle protolith. The complexes of the Okhotsk-Chukotka belt show signs of geochemical zoning, both longitudinal and transverse relative to the strike of the continent-ocean boundary.
DOI: 10.15372/RGG2019149
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