Geodynamic setting of the formation of late cretaceous granitoids in the Central Sikhote-Alin

Abstract

As a result of LA-ICP-MS U-Pb isotope dating of zircons, new data on the Late Cretaceous age of a number of granite massifs localized in the central part of the Sikhote-Alin orogenic belt were obtained for the first time. Three complexes of plutonic rocks of different ages have been identified. The first has an age of 105–92 Ma and corresponds to the Tatiba Series of synorogenic magmatism. The second (86–83 Ma) and third (~73 Ma) complexes formed during the post-orogenic stage of development. The obtained data refute the widespread opinion about the absence of Late Cretaceous magmatism on the eastern margin of the Paleo-Asian continent at a considerable distance from the Late Cretaceous continental marginal East Sikhote-Alin volcano-plutonic belt (ESAVPB). The ages of the studied granitoids ideally coincide with the time of the change in the convergence angle between the Paleo-Pacific Plate and the eastern margin of the Paleo-Asian continent in the Late Cretaceous. These changes in the direction of movement of the oceanic plate with respect to the continent (or rather, plate rotations) were apparently accompanied by ruptures of the submerged plate (slab) due to different subduction rates of different parts of the oceanic plate, followed by asthenospheric matter rising through the permeable zones, causing partial melting of the lower crust, and, as a result, intracontinental intrusive magmatism.