Crustal Sinking and Formation of the Main Tectonic Structures and Igneous Provinces in the Arctic in the Late Cretaceous-Cenozoic: A View from the Subduction-Convective Model

摘要

A new geodynamic model of the Cretaceous-Cenozoic evolution of the Arctic has been developed in recent years at the Shirshov Institute of Oceanology, Russian Academy of Sciences, with the participation of Geological Institute, Russian Academy of Sciences, and the Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences. In the framework of this model, the upper mantle convection associated with the Pacific subduction zone plays the main role; based on this model, we also propose a mechanism of crustal subduction, leading to the formation of oceanic depressions and sedimentary basins, as well as the emergence of large magmatic provinces in the Arctic. This mechanism is associated with the establishment of an upper mantle convection regime, which is more complex in comparison with the initial one; along with the existence of a long, horizontally elongated convective cell (which produces the effect of conveyor drag of the lithosphere), this regime is characterized by the appearance of inner isometric cells (which produce the effect of upper mantle plumes). These isometric cells lead to the formation of igneous provinces if, under conditions of stretching of the lithosphere, faults are formed to provide magma eruption to the surface. If the geomechanical conditions in the lithosphere impede the magma outflow, then, upon cooling, a lens of magma-derived volume, located at the base of the thinned lithosphere, should undergo a phase transition with the formation of heavy eclogite rocks, which causes the formation of deep basins and deep sedimentary basins in the Arctic.