This paper presents a study of the seismic P−wave velocity and density structure of the lithosphere−asthenosphere system along a 800 km long transect extending from the actively spreading Knipovich Ridge, across southern Spitsbergen to the Kong Karls Land Volcanic Province. The 2D seismic and density model documents 6–8 km thick oceanic crust formed at the Knipovich Ridge, a distinct continent−ocean−boundary (COB), the eastern boundary of the dominantly sheared Hornsund Fault Zone, and the eastern boundary of the Early Cenozoic West Spitsbergen Fold−and−Thrust Belt. The crustal continent−ocean transitional zone has significant excess of density (more than 0.1 g/cm 3 in average), characteristic for mafic/ultramafic and high−grade metamorphic rocks. The main Caledonian suture zone between Laurentia and Barentsia is interpreted based on variations in crustal thickness, velocities and densities. A high velocity body in the lower crust is preferably interpreted in terms of Early Cretaceous magmatism channelled from an Arctic source southwards along the proto−Hornsund zone of weakness. The continental upper mantle expresses high velocities (8.24 km/s) and densities (3.2 g/cm 3 ), which may be interpreted in terms of low heat−flow and composition dominated by dunites. The lower velocities (7.85 km/s) and densities (3.1 g/cm 3 ) observed in the oceanic lithosphere suggest composition dominated by primitive peridotites. The model of mantle allows for successful direct description of subcrustal masses distribution compensating isostatically uneven crustal load. The estimated low value of correlation between density and velocity in the mantle 0.12 kg × s × m −4 suggests that horizontal density differences between oceanic and continental mantle would be dominated by compositional changes.

This paper presents a review of geophysical studies of the crust and the lithosphere- asthenosphere boundary (LAB) in the ocean-continent transition in the area of Spitsbergen (Svalbard Archipelago) in high Arctic. Over last decades many investigations were performed during Polish geophysical expeditions, as well as in the framework of international cooperation with scientists from Germany, Japan, Norway and USA. We compiled here existing seismic, gravity and thermal models down to LAB depth along the 800 km long transect extending from the actively spreading Knipovich Ridge, across southern Spitsbergen to the Kong Karls Land Volcanic Province. The results of all methods are very consistent, although they are sensitive to different physical parameters: seismic wave velocities, densities and thermal. The thinnest lithosphere of only 12 km is found beneath the Knipovich Ridge. Only 50 km to the west and 50 km to the east of the ridge the LAB depth increases to about 30 km, and this value corresponds to the oceanic structure of the North Atlantic Ocean. Beneath southern Spitsbergen the LAB depth is about 55 km and increases to 90–100 km beneath continental structure of the Barents Sea. The uplift of the LAB close to distance of 700 km along transect could be correlated with Kong Karls Land Volcanic Province.