The Chukotka Segment of the Uda–Murgal and Okhotsk–Chukotka Volcanic Belts: Age and Tectonic Environment

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.

High‐Latitude Geomagnetic Secular Variation at the End of the Cretaceous Normal Superchron Recorded by Volcanic Flows From the Okhotsk‐Chukotka Volcanic Belt

“…The volcanic sequences of the OCVB (74–106 Ma; e.g., Akinin & Miller, 2011; Tikhomirov et al., 2020) uncomformably overlie all pre‐Albian complexes. Within the studied area shown in Figure 2, the sequences averagely dip 5°–10° southeast, toward the inner zone of the volcanic belt.…”

“…Within the studied area shown in Figure 2, the sequences averagely dip 5°–10° southeast, toward the inner zone of the volcanic belt. In the absence of vestiges of compressional tectonics, the monocline likely results from the subsidence related with the discharge of magmatic chambers (Tikhomirov et al., 2020). The local departures of the bedding attitude from the general SE trend are ascribed to dissected paleotopography and/or local manifestations of caldera tectonics (e.g., Cole et al., 2005).…”

Detrital Zircon U-Pb Data for Jurassic–Cretaceous Strata from the South-Eastern Verkhoyansk-Kolyma Orogen—Correlations to Magmatic Arcs of the North-East Asia Active Margin

“…Biakov et al [59][60][61] reported calc-alkaline volcanics of the late Middle-Late Permian age in the east of the Okhotsk Terrane and ascribed them to the Okhotsk-Taigonos volcanic arc, although they could have alternatively been assigned to the Uda-Murgal Magmatic belt. Mesozoic diorite and granodiorite plutons and volcanic rocks have yielded zircon U-Pb ages of 160-100 Ma (e.g., [1,62] (Figure 1). The belt can be divided into two branches: the Svyatoi Nos and Oloy.…”

“…The belt is interpreted as an Andean-type continental Magmatic arc [1,2,4,77,80,81]. The Aptian-Late Cretaceous age of the volcanic and volcanoclastic rocks were determined by fossil flora, while zircon U-Pb and mica 40 Ar/ 39 Ar ages from the volcanic and plutonic rocks clustered between 106-76 Ma [1,62,73,74,76,77,[81][82][83][84][85][86].…”