Modern volcanism in the Earth’s northern hemisphere and its relations with the evolution of the North Pangaea modern supercontinent and with the spatial distribution of hotspots on the Earth: The hypothesis of relations between mantle plumes and deep subduction

Abstract

The paper reports results of the analysis of the spatial distribution of modern (younger than 2 Ma) volcanism in the Earth’s northern hemisphere and relations between this volcanism and the evolution of the North Pangaea modern supercontinent and with the spatial distribution of hotspots of the Earth’s mantle. Products of modern volcanism occur in the Earth’s northern hemisphere in Eurasia, North America, Greenland, in the Atlantic Ocean, Arctic, Africa, and the Pacific Ocean. As anywhere worldwide, volcanism in the northern hemisphere of the Earth occurs as (a) volcanism of mid-oceanic ridges (MOR), (b) subduction-related volcanism in island arcs and active continental margins (IA and ACM), (c) volcanism in continental collision (CC) zones, and (d) within-plate (WP) volcanism, which is related to mantle hotspots, continental rifts, and intercontinental belts. These types of volcanic areas are fairly often neighboring, and then mixed volcanic areas occur with the persistent participation of WP volcanism. Correspondingly, modern volcanism in the Earth’s northern hemisphere is of both oceanic and continental nature. The latter is obviously related to the evolution of the North Pangaea modern supercontinent, because it results from the Meso-Cenozoic evolution of Wegener’s Late Paleozoic Pangaea. North Pangaea in the Cenozoic comprises Eurasia, North and South America, India, and Africa and has, similar to other supercontinents, large sizes and a predominantly continental crust. The geodynamic setting and modern volcanism of North Pangaea are controlled by two differently acting processes: the subduction of lithospheric slabs from the Pacific Ocean, India, and the Arabia, a process leading to the consolidation of North Pangaea, and the spreading of oceanic plates on the side of the Atlantic Ocean, a process that “wedges” the supercontinent, modifies its morphology (compared to that of Wegener’s Pangaea), and results in the intervention of the Atlantic geodynamic regime into the Arctic. The long-lasting (for >200 Ma) preservation of tectonic stability and the supercontinental status of North Pangaea are controlled by subduction processes along its boundaries according to the predominant global compression environment. The long-lasting and stable subduction of lithospheric slabs beneath Eurasia and North America not only facilitated active IA + ACM volcanism but also resulted in the accumulation of cold lithospheric material in the deep mantle of the region. The latter replaced the hot mantle and forced this material toward the margins of the supercontinent; this material then ascended in the form of mantle plumes (which served as sources of WP basite magmas), which are diverging branches of global mantle convection, and ascending flows of subordinate convective systems at the convergent boundaries of plates. Subduction processes (compressional environments) likely suppressed the activity of mantle plumes, which acted in the northern polar region of the Earth (including the Siberian trap magmatism) starting at the latest Triassic until nowadays and periodically ascended to the Earth’s surface and gave rise to WP volcanism. Starting at the breakup time of Wegener’s Pangaea, which began with the opening of the central Atlantic and systematically propagated toward the Arctic, marine basins were formed in the place of the Arctic Ocean. However, the development of the oceanic crust (Eurasian basin) took place in the latter as late as the Cenozoic. Before the appearance of the Gakkel Ridge and, perhaps, also the oceanic portion of the Amerasian basin, this young ocean is thought to have been a typical basin developing in the central part of supercontinents. Wegener’s Pangaea broke up under the effect of mantle plumes that developed during their systematic propagation to the north and south of the Central Atlantic toward the North Pole. These mantle plumes were formed in relation with the development of global and local mantle convection systems, when hot deep mantle material was forced upward by cold subducted slabs, which descended down to the core-mantle boundary. The plume (WP) magmatism of Eurasia and North America was associated with surface collision- or subduction-related magmatism and, in the Atlantic and Arctic, also with surface spreading-related magmatism (tholeiite basalts).