The Structure of the Ocean Bottom in the Junction of the Trough King’s and the Mid-Atlantic Ridge (North Atlantic)

— During the 59-th cruise of the R/V Akademik Nikolaj Strakhov, bathymetric and hydromagnetic surveys, acoustic profiling, and sampling of the ocean floor were carried out on the eastern flank of the Mid-Atlantic Ridge (MAR) in the North Atlantic between the King’s Trough, which has an oblique northwesterly strike, and the axial zone, as well as in the axial zone itself of the MAR, which is further north of the proposed intersection of this Trough with the spreading axis. In the axial zone of the MAR, several spreading cells are distinguished, which unusually merge into one another without lateral displacement, but changing their strike. In the center of the longest (up to 65 km) cell located on strike of the King’s Trough, a large volcanic uplift blocking the rift valley was revealed, formed under conditions of abnormally high magmatic budget. In the crest zone among the rift hills, a discordant zone with a total strike of 320° was found, composed of several depressions that decrease in size and shift to the north from east to west, indicating the migration of spreading cells in the same direction. The discordant zone joins the rift valley with the large uplift described above, and in the flank zone of the MAR it ends at the northwestern end of the King’s Trough. Several large volcanic uplifts are distributed between the King’s Trough and the axial zone of the MAR, indicating periodic increases in the intensity of volcanism in the rift valley. According to the results of the hydromagnetic survey, such amplifications occurred between 8 and 11 million years ago and between 5 and 6 million years ago, while in the latter case, according to the location of uplifts and the discordant zone, the center of intense magmatism, or otherwise the microplume, was constantly shifting along the rift valley from south to north. The sedimentary cover in the studied area is significantly deformed, which is manifested in the presence of the faults with an amplitude of up to 50 m and piercing structures with a width of up to 3 km protruding above the bottom up to 40 m. Apparently, the reason for the neotectonic activity is the presence of large density inhomogeneities in the crust and upper mantle associated with superimposed magmatism.