Abstract
In 2018–2020 the research vessel (R/V) Professor Logachev (cruises 39 and 41) carried out geological and geochemical studies in the bottom waters of the Mid-Atlantic Ridge hydrothermal fields at 14°45’ N, 13°07’ N, and 13°09’ N. Two new hydrothermal fields were discovered—the Molodezhnoye and Koralovoye. Standard conductivity, temperature, and depth (CTD) sounding with a methane sensor was accompanied by video surveillance and sampling of rocks and water. The rocks were characterized by a zonal composition with opal and sulfides of copper and zinc. An increase in methane concentration values was accompanied by CTD anomalies in the bottom waters. The methane anomaly was formed within the hydrothermal plume of both high-temperature and low-temperature systems. Methane was almost absent in the plume of neutral buoyancy and was associated in all the studied manifestations with the ascending flow of hot waters over the hydrothermal vents. The hydrothermal plumes were characterized by increased Cu, Zn, and Fe concentrations at background Mn concentrations. Signs of low-temperature hydrothermal activity were also observed. Different sources and mechanisms are required to explain the elevated concentrations of base metals and methane in the hydrothermal plumes.
Highlights
Since the end of the 1970s, numerous studies have been carried out on polymetallic sulfides and metalliferous sediments across the ocean floor
During the 39th cruise of the research vessel (R/V) Professor Logachev, data were obtained on the formation of methane anomalies in the zone of discharge of hydrothermal solutions
The methane sensor used made it possible to record methane anomalies not in solutions circulating through hydrothermal systems, but in hydrothermal plumes
Summary
Since the end of the 1970s, numerous studies have been carried out on polymetallic sulfides and metalliferous sediments across the ocean floor. New opportunities for detecting deep-sea hydrothermal activity are emerging with the use of methane sensors in the process of sounding the water column. In the 39th (2018) and 41st (2020) cruises of the R/V Professor Logachev, new data on the formation of methane anomalies in areas of submarine hydrothermal activity on the Mid-Atlantic Ridge were obtained. The Koralovoe (~2800–2900 m) and Molodezhnoe (~3500 m) hydrothermal fields, at 13◦07 N and 13◦09 N, respectively, were discovered on the MAR (Mid-Atlantic Ridge) during the 41st cruise of the R/V Professor Logachev. Standard CTD sounding was accompanied by the measurement of methane concentrations with a Franatech METS methane sensor (with a methane calibration range of 1 nM–500 nM) to study in detail hydrothermal plumes near high-temperature sources. New data were obtained on the CTD structure of hydrothermal plumes and methane anomalies
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