The Yermak Plateau is a prominent bathymetric feature of the Arctic Ocean. To the west it is bordered by the Fram Strait, which forms the only deep-water connection between the Arctic and the other global oceans. Origin, crustal nature and age of the Yermak Plateau are largely unknown. For this study, we investigated dredged rocks of two sites from the Yermak Plateau. Based on petrography, geochemistry, and geochronology, we distinguished between ice-transported and in-situ rocks. Ice-transported material was most likely derived from outcrops of the High Arctic Large Igneous Province (HALIP) on Franz Josef Land, the Siberian trap province, and presumably from northern Svalbard. Our data from the in-situ rocks, in conjunction with previously published geophysical data, show that the investigated parts of the Yermak Plateau are composed of stretched continental crust strongly affected by alkaline magmatism. The continental rocks represent a direct continuation of the exposures on northern Svalbard. Alkaline magmatism took place at ~ 51 Ma and was related to continental rifting in an extensional setting. The melts were formed by low degrees of partial melting of the sub-continental lithospheric mantle and are probably associated with the high-amplitude magnetic anomalies described for the northeastern Yermak Plateau. Extension of the Yermak Plateau was contemporaneous with spreading of the adjacent young Eurasian Basin, and occurred during the peak of compressional deformation affecting North Greenland, Svalbard, and Ellesmere Island. These contrasting regimes were probably compensated by transpression and strike-slip movements along the DeGeer and Wegener Faults. The date of ~ 51 Ma for extension-related magmatism also provides age constraints for the extension-related formation of the Sophia Basin (and thus for water exchange between the Eurasian Basin, the area of the DeGeer Fault and the young Norwegian-Greenland Sea), and for the sediments covering the horst-and-graben structures of the Yermak Plateau.
EPIC Alfred Wegener Institut