Geodynamics and Early Cretaceous Magmatism of the Northern Volcano-Plutonic Belt of Verkhoyan–Kolyma Fold Area (Northeastern Russia)

Abstract

New data on the geological position, U‒Pb SIMS zircon ages, petrogeochemical features, Sr‒Nd isotopic composition, and geodynamic setting of the granitoids and volcanics of the Northern volcanic-plutonic belt of the Verkhoyan–Kolyma fold area are presented. Magmatic rocks of the belt include granitoids of Elikchan, Kuranakh, and Bakyn plutons, composed of Elikchan granite–granodiorite complex and volcanics of predominantly intermediate-felsic Tumusskaya sequence with subvolcanic bodies of the same composition. They form a single Early Cretaceous (127–121 Ma) volcanic-plutonic assemblage. Granitoid plutons are elongated in a sublatitudinal and northwestern direction and are discordant to main fold-and-thrust structures. Granitoids intrude and metamorphose Jurassic terrigenous and Early Cretaceous volcanics of Tumusskaya sequence and are intruded by younger Late Cretaceous subvolcanic bodies. Granitoids of Bakyn, Elikchan, and Kuranakh plutons combine petrogeochemical features of I-, S-, and A-type granites. Such diversity of petrogeochemical granitoid types, as well as interrelations of major (\({\text{F}}{{{\text{e}}}_{{\text{2}}}}{\text{O}}_{3}^{{{\text{tot}}}}\)–TiO₂–MgO) and rare (Ba/La–Nb × 5–Yb × 10) elements in granitoids and the same age volcanics of the Tumusskaya sequence, allow us to refer them to igneous rocks of transform or sliding plate boundaries. Collision between the Chukotka microcontinent and the Siberian continent with the earlier accreted Kolyma–Omolon microcontinent in Barremian–Aptian time changed to postcollisional extension and formation of volcanic-plutonic assemblage of the Northern volcanic-plutonic belt. Postcollisional extension took place at the transform or sliding plate boundaries. Sr–Nd isotopic characteristics of granitoids of all granite plutons indicate the interrelation of mantle and crustal sources of granitoid melts in this process.