Hydrothermal Mineral Assemblages at 71° N of the Mid-Atlantic Ridge (First Results)

Abstract

The article discusses the preliminary results of plume and bottom sediment studies of the Trollveggen hydrothermal vent field based on data from cruise 68 of the R/V Akademik Mstislav Keldysh. The hydrothermal vent field is located east of the axial zone of the slow-spreading Mohn Ridge near the Jan Mayen hotspot at a depth of about 550 m (71°18′ N, Norwegian–Greenland Basin). The hydrothermal vent field plume was characterized by a weak distribution in the water column; temperature, density, and salinity anomalies; a moderate methane concentration; and a low concentration of suspended particulate matter near the bottom. The enrichment of bottom sediments in barium, strontium, and some sulfide-forming elements (zinc, lead, copper, and molybdenum) was shown. Two mineral assemblages of hydrothermally modified bottom sediments were revealed: pyrite and barite–marcasite. The temperature of hydrothermal fluids was established by thermal and cryometric studies of gas–liquid fluid inclusions in barite (128–260°С); the FeS–ZnS equilibrium diagram of sulfide minerals was also used (130–290°С). Our data were close to direct fluid temperature measurement data [28]. We compared the hydrothermal mineralization of the Trollveggen vent field and earlier 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.