THE ARCTIC RIFT SYSTEM AND THE BOUNDARY BETWEEN THE EURASIAN AND NORTH AMERICAN LITHOSPHERIC PLATES: NEW INSIGHT TO PLATE TECTONIC THEORY

Abstract

The Arctic rift system includes the Mid-Arctic Gakkel Ridge, the Laptev Sea continental margin and the Moma rift. The Gakkel Ridge is the world''s slowest spreading mid-ocean ridge with spreading rates ranging from 1.2 cm/year to 0.6 cm/year in the southernmost part close to the Laptev Sea. The distinctive feature of the Gakkel Ridge consists of the butt junction with the Laptev sea passive continental margin and such type of junction has never been observed all over the world. The available geological and geophysical data allow to trace how the sea-floor spreading in the Eurasian basin transforms to the rifting on the Laptev Sea continental margin. The Moma rift as the third element of the Arctic rift system develops in the unsteady stress field conditions. Key point to decipher the geodynamics can be obtained under the study of the recent volcanic activity of Northeast Asia. New data on the helium, strontium, and neodymium isotope systematics and new results obtained from the study of rare and rare-earth elements in lavas of Holocene volcanoes in Northeast Asia suggest that young volcanic features are an evidence of activity of a mantle plume at the earliest stage of its development. Such a geodynamic origin of volcanism is likely to control the stress pattern near the boundary between the Eurasian and North American lithospheric plates. We propose that in Northeast Asia up to now there is an unknown type of the plate boundary induced by incipient mantle plume at very beginning stage. Thus, all previous attempts to represent the boundary between the Eurasian and North American plates in linear form lose their meaning.