Volcanic Structures and Magmatic Evolution of the Vesteris Seamount, Greenland Basin

The formation of isolated seamounts distant from active plate boundaries and mantle plumes remains unsolved. The solitary intraplate volcano Vesteris Seamount is located in the Central Greenland Basin and rises ∼3,000 m above the seafloor with a total eruptive volume of ∼800 km3. Here, we present a new high-resolution bathymetry of Vesteris Seamount and a detailed raster terrain analysis, distinguishing cones, irregular volcanic ridges, volcanic debris fans, U-shaped channels and lava flows. The slope angles, ruggedness index and slope direction were combined with backscatter images to aid geologic interpretation. The new data show that the entire structure is a northeast to southwest elongated stellar-shaped seamount with an elongated, narrow summit surrounded by irregular volcanic ridges, separated by volcanic debris fans. Whole-rock geochemical data of 78 lava samples form tight liquid lines of descent with MgO concentrations ranging from 12.6 to 0.1 wt%, implying that all lavas evolved from a similar parental magma composition. Video footage from Remotely Operated Vehicle (ROV) dives shows abundant pyroclastic and hyaloclastite deposits on the summit and on the upper flanks, whereas lavas are restricted to flank cones. The seamount likely formed above a weak zone of the lithosphere possibly related to initial rifting parallel to the nearby Mohns Ridge, but the local stress field increasingly affected the structure of the volcano as it grew larger. Thus, we conclude that the evolution of Vesteris Seamount reflects the transition from deep, regional lithospheric stresses in the older structures to shallower, local stresses within the younger volcanic structures similar to other oceanic intraplate volcanoes. Our study shows how the combination of bathymetric, visual and geochemical data can be used to decipher the geological evolution of oceanic intraplate volcanoes.

Late quarterly paleooceanology of the Norwegian Sea on the basis of analysis of benthic foraminifers

Deep-water cores selected at AMK 5536 and 5524 stations on the 68th cruise of the research vessel «Academik Mstislav Keldysh» from the north-eastern part of the Norwegian-Greenland basin were investigated by sedimentological and micropaleontological methods. Changes in benthic foraminifera communities in the Norwegian Sea, their changes in time, which make it possible to use paleooceanological reconstructions and associate them with marine isotope stages are considered.

Hydrothermal mineral associations on 71° n of Mid-Atlantic ridge (first results)

We discuss the preliminary results of the plume and bottom sediments studies of the Trollveggen hydrothermal vent field based on data from the 68th cruise of the RV Akademik Mstislav Keldysh. The hydrothermal vent field is located to the east of the axial zone of the slow-spreading Mohn Ridge close to the Jan Mayen hotspot at a depth of about 550 m (7118 'N, Norwegian-Greenland Basin). The plume of the hydrothermal vent field was characterized by a weak distribution in the water column, anomalies of temperature, density and salinity, a moderate concentration of methane and a low concentration of suspended particulate matter near the bottom. The enrichment of bottom sediments with barium, strontium and some sulfide forming elements (zinc, lead, copper, molybdenum) was shown. Two mineral associations of hydrothermally modified bottom sediments were revealed: pyrite and barite-marcasite. The temperature of hydrothermal fluids was established by the method of thermal and cryometric studies of gas-liquid fluid inclusions in barite (128260C) and using the FeSZnS equilibrium diagram of sulfide minerals (130290C). Our data were close to the data of direct measurements of fluid temperature [28]. We made a comparison of the hydrothermal mineralization of the Trollveggen vent field and the previously studied fields of the Mid-Atlantic Ridge located near the Azores hotspot. As a result we confirmed the influence of ocean depth and PT-conditions on the formation of hydrothermal deposits.

Sedimentation systems definition of the Barents Sea and Norwegian-Greenland basin during 68th cruise of the research vessel Academic Mstislav Keldysh

The article presents summary of the first research results of sedimentation systems of the region of interaction of the Arctic Ocean and Atlantic Ocean obtained in July-August 2017. Joint examination of the system of dispersed sedimentary matter (aerosols, suspended particulate matter, phytoplankton, faecal pellets, etc.) – concentrated sedimentary matter (bottom sediments), of biogeochemical processes of the matter transformation in the system in line with paleo-oceanologic reconstructions allow us to understand environment and climate of different geological epoch in one of the key ocean areas. The attempt to study the role of endogenous material in recent sedimentation processes in the ocean was taken on the example of the subpolar zone of the mid-ocean ridges system – Mohn Ridge.