Russian Journal of Earth Sciences
Vol. 5, No. 5, October 2003
The Arctic rift system
and the boundary between the Eurasian and North American lithospheric plates:
New insight to plate tectonic theory
A. F. Grachev
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.