LITHOSPHERE STRUCTURE OF THE NORTH ATLANTIC REGION

Thermo-chemical heterogeneities in crustal and upper mantle structure reflect an interplay of deep and shallow geodynamical processes related to plate tectonics and mantle convection. The North Atlantic region (north of 45N) is particularly intriguing because of its complex geodynamic evolution which includes the presence of paleo-spreading zones, continental fragments within the Jan Mayen block, still heavily debated Iceland mantle anomaly, the anomaly in crustal thickness across the North Atlantic ocean with its possible continuation across the Labrador Sea, and the transition to the ultra-slow spreading in the northern part of the region. It has also been long known that the bathymetry of the North Atlantic ocean is among the most anomalous in oceans. The evolution of the continental margins of the North Atlantic ocean is also enigmatic, in particular the origin and the age of the high topography along the Norwegian and the Greenland margins.

We present an overview of the crustal and upper mantle structure of the North Atlantic region both for the oceanic and the continental crust. For the latter, we present our new seismic interpretations for Norway and Greenland. We analyze regional patterns of crustal structural heterogeneity and link them to geodynamic evolution of the region.

We also present a model of the upper mantle residual gravity anomalies based on GOCE satellite and EGM2008 gravity models, from which the gravitational effect of the crust was subtracted. Spatial resolution of the model is ca. 150 km and the uncertainty in the amplitude of mantle residual gravity anomalies is ca 20-25%. These anomalies reflect thermal and chemical heterogeneity of the upper mantle in the North Atlantic region, which we interpret by comparing the results with the predictions for “normal” oceans. This allows us to speculate on thermo-chemical heterogeneity of the North Atlantic mantle and to link geodynamic evolution of the region to mantle processes. We present the map of the calculated temperature anomaly in the upper mantle of the North Atlantic region and speculate if it may be resolved by seismic methods. We also map the upper mantle regions with strong chemical (compositional) anomalies and speculate on their possible origin by comparing our results to published geochemical data.