scholarly journals Identification of Two New Hydrothermal Fields and Sulfide Deposits on the Mid-Atlantic Ridge as a Result of the Combined Use of Exploration Methods: Methane Detection, Water Column Chemistry, Ore Sample Analysis, and Camera Surveys

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 726
Author(s):  
Sergei Sudarikov ◽  
Egor Narkevsky ◽  
Vladimir Petrov
Keyword(s):  
Low Temperature ◽  
Hydrothermal Vents ◽  
Hydrothermal Activity ◽  
Neutral Buoyancy ◽  
Combined Use ◽  
Bottom Waters ◽  
Mid Atlantic Ridge ◽  
Hydrothermal Plumes ◽  
Geochemical Studies ◽  
Hydrothermal Fields

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.

scholarly journals Pyrite Varieties at Pobeda Hydrothermal Fields, Mid-Atlantic Ridge 17°07′–17°08′ N: LA-ICP-MS Data Deciphering

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 622
Author(s):  
Valeriy Maslennikov ◽  
Georgy Cherkashov ◽  
Dmitry Artemyev ◽  
Anna Firstova ◽  
Ross Large ◽  
...  
Keyword(s):  
Low Temperature ◽  
Massive Sulfide ◽  
Black Smoker ◽  
Fine Grained ◽  
Framboidal Pyrite ◽  
Icp Ms ◽  
Mid Atlantic Ridge ◽  
Seafloor Massive Sulfide ◽  
Hydrothermal Fields ◽  
Feeder Zone

The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder zone facies to seafloor diffuser facies. Spongy, framboidal, and fine-grained pyrite varieties replaced pyrrhotite, greigite, and mackinawite “precursors”. The later coarse and fine banding oscillatory-zoned pyrite and marcasite crystals are overgrown or replaced by unzoned subhedral and euhedral pyrite. In the microfacies range, the amount of isocubanite, wurtzite, unzoned euhedral pyrite decreases versus an increasing portion of framboidal, fine-grained, and spongy pyrite and also marcasite and its colloform and radial varieties. The trace element characteristics of massive sulfides of Pobeda seafloor massive sulfide (SMS) deposit are subdivided into four associations: (1) high temperature—Cu, Se, Te, Bi, Co, and Ni; (2) mid temperature—Zn, As, Sb, and Sn; (3) low temperature—Pb, Sb, Ag, Bi, Au, Tl, and Mn; and (4) seawater—U, V, Mo, and Ni. The high contents of Cu, Co, Se, Bi, Te, and values of Co/Ni ratios decrease in the range from unzoned euhedral pyrite to oscillatory-zoned and framboidal pyrite, as well as to colloform and crystalline marcasite. The trend of Co/Ni values indicates a change from hydrothermal to hydrothermal-diagenetic crystallization of the pyrite. The concentrations of Zn, As, Sb, Pb, Ag, and Tl, as commonly observed in pyrite formed from mid- and low-temperature fluids, decline with increasing crystal size of pyrite and marcasite. Coarse oscillatory-zoned pyrite crystals contain elevated Mn compared to unzoned euhedral varieties. Framboidal pyrite hosts maximum concentrations of Mo, U, and V probably derived from ocean water mixed with hydrothermal fluids. In the Pobeda SMS deposit, the position of microfacies changes from the black smoker feeder zone at the base of the ore body, to seafloor marcasite-pyrite from diffuser fragments in sulfide breccias. We suggest that the temperatures of mineralization decreased in the same direction and determined the zonal character of deposit.

Stratiform sulfide and barite–fluorite mineralization of the Vulcan prospect, Northwest Territories: exhalation of basinal brines along a faulted continental margin

1984 ◽  
Vol 21 (1) ◽  
pp. 78-91 ◽  
Author(s):  
David A. Mako ◽  
Wayne C. Shanks III
Keyword(s):  
Northwest Territories ◽  
Hydrothermal Vents ◽  
Thickness Distribution ◽  
Massive Sulfide ◽  
Hydrothermal Activity ◽  
High Potassium ◽  
The Road ◽  
Fine Grained ◽  
Bottom Waters ◽  
Brine Pools

Laminated and massive sulfide (pyrite, sphalerite, galena) mineralization and massive barite – fluorite–galena lenses occur in Upper Silurian – Lower Devonian Road River Formation shales of the Vulcan property along the eastern flank of the Selwyn Basin, Northwest Territories, Canada. The 5 km thick stratigraphic section, ranging in age from Hadrynian through Mississippian, offers insight into the nature of the Mackenzie Platform – Selwyn Basin transition. Abrupt facies changes, synsedimentary faults, debris flows, local unconformities, and the presence of high-potassium mafic flows indicate extensional tectonics during deposition of the Road River Formation. Mineralization resulted from heated, metal-rich basinal brines that vented on the sea floor up normal faults.Sulfur-isotope studies indicate that both sulfate and sulfide were derived from the exhaling metalliferous brine. Sulfur-isotope data also suggest that reduction of sulfate in the brine occurred as a result of organic decomposition, possibly during thermal maturation of hydrocarbons at temperatures greater than 80 °C. Fluid inclusion observations indicate that the brine salinity reached 26 wt.% NaCl for at least a portion of the evolution of the hydrothermal system.Cooling of the brine during venting into bottom waters caused initial rapid precipitation of fine-grained barite, resulting in a baritic buildup above vent areas. Continued percolation of the brine through the baritic mound caused recrystallization of the barite and then the deposition of interstitial fluorite and galena. In other areas the dense ore fluid collected in topographic depressions, or brine pools, in which sulfide minerals accumulated under anoxic conditions. Location of hydrothermal vents, paleotopography, and intensity of hydrothermal activity were the main controls on the thickness, distribution, and grade of Vulcan mineralization.

Interaction of submarine volcanic and high-temperature hydrothermal activity proposed for the formation of the Agrokipia, volcanic massive sulfide deposits of Cyprus

1992 ◽  
Vol 29 (9) ◽  
pp. 1928-1936 ◽  
Author(s):  
James M. Hall
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Hydrothermal Vents ◽  
Massive Sulfide ◽  
Hydrothermal Activity ◽  
Hydrothermal Fluids ◽  
Spreading Ridge ◽  
Sulfide Deposits ◽  
Original Surface ◽  
Massive Sulfide Deposits

The results of drilling near the spreading-ridge-type, volcanic-hosted, massive sulfide deposits of Agrokipia, Cyprus, are described. Mineralization and associated argillic hydrothermal alteration occur over intervals of 5–130 m and at depths of 80–230 m beneath the original surface of the oceanic crust. Mineralization occurs in massive flows that probably represent a locally ponded sequence up to 300 m thick. Abundant glass–aphanitic basalt transitions are present from about 100 m below the surface of the ponded sequence, with glass abundances locally reaching 60% of the section. A novel hypothesis, involving the presence of active, high-temperature hydrothermal vents beneath the cooling ponded sequence, with the passage of hydrothermal fluids through the still molten lava, is proposed to account for the observations. While this hypothesis is reasonable, the inferred processes have not, as yet, been demonstrated under either laboratory or field conditions. The seafloor expression of this system was probably one of widely distributed, low-temperature, fluid emission over the surface of a lava pond in the axial graben of a spreading ridge.

scholarly journals Regional oceanographic features and hydrothermal activity influence protist diversity and biogeography in the Okinawa Trough

2019 ◽  
Author(s):  
Margaret Mars Brisbin ◽  
Asa E. Conover ◽  
Satoshi Mitarai
Keyword(s):  
Hydrothermal Vents ◽  
Okinawa Trough ◽  
Hydrothermal Activity ◽  
Water Masses ◽  
Mass Composition ◽  
Rare Biosphere ◽  
Environmental Selection ◽  
The Okinawa Trough ◽  
Dispersal Barriers ◽  
Bottom Waters

AbstractMicrobial eukaryotes (protists) contribute substantially to ecological functioning in marine ecosystems, but factors shaping protist diversity, such as dispersal barriers and environmental selection, remain difficult to parse. Deep-sea water masses, which form geographic barriers, and hydrothermal vents, which represent isolated productivity hotspots, are ideal opportunities for studying the effects of dispersal barriers and environmental selection on protist communities. The Okinawa Trough, a deep, back-arc spreading basin, contains distinct water masses in the bottom waters of northern and southern regions and at least twenty-five active hydrothermal vents. In this study, we used metabarcoding to characterize protist communities from fourteen stations spanning the length of the Okinawa Trough, including three hydrothermal vent sites. Significant differences in community structure reflecting regional oceanography and water mass composition were present, indicating the importance of geographic factors in shaping protist communities. Protist communities in bottom waters affected by hydrothermal activity were significantly different from communities in other bottom waters, suggesting that environmental factors can be especially important in shaping community composition under specific conditions. Amplicon sequence variants that were enriched in hydrothermally influenced bottom waters largely derived from cosmopolitan protists that were present, but rare, in other near-bottom samples, thus highlighting the importance of the rare biosphere.

Hydrothermal nontronite formation associated with microbes from low-temperature diffuse hydrothermal vents at the South Mid-Atlantic Ridge

2017 ◽  
Vol 122 (9) ◽  
pp. 2375-2392 ◽  
Author(s):  
Kaiwen Ta ◽  
Xiaotong Peng ◽  
Shun Chen ◽  
Hengchao Xu ◽  
Jiwei Li ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrothermal Vents ◽  
The South ◽  
Mid Atlantic Ridge

scholarly journals A seawater throttle on H2production in Precambrian serpentinizing systems

2020 ◽  
Vol 117 (26) ◽  
pp. 14756-14763 ◽  
Author(s):  
Benjamin M. Tutolo ◽  
William E. Seyfried ◽  
Nicholas J. Tosca
Keyword(s):  
Low Temperature ◽  
Hydrothermal Vents ◽  
Oxidation States ◽  
Ridge Axis ◽  
Secular Changes ◽  
Mid Atlantic Ridge ◽  
Initial Discovery ◽  
The Origin Of Life ◽  
Microbial Systems ◽  
Alkaline Hydrothermal Vents

Since the initial discovery of low-temperature alkaline hydrothermal vents off the Mid-Atlantic Ridge axis nearly 20 y ago, the observation that serpentinizing systems produce abundant H2has strongly influenced models of atmospheric evolution and geological scenarios for the origin of life. Nevertheless, the principal mechanisms that generate H2in these systems, and how secular changes in seawater composition may have modified serpentinization-driven H2fluxes, remain poorly constrained. Here, we demonstrate that the dominant mechanism for H2production during low-temperature serpentinization is directly related to a Si deficiency in the serpentine structure, which itself is caused by low SiO2(aq) concentrations in serpentinizing fluids derived from modern seawater. Geochemical calculations explicitly incorporating this mechanism illustrate that H2production is directly proportional to both the SiO2(aq) concentration and temperature of serpentinization. These results imply that, before the emergence of silica-secreting organisms, elevated SiO2(aq) concentrations in Precambrian seawater would have generated serpentinites that produced up to two orders of magnitude less H2than their modern counterparts, consistent with Fe-oxidation states measured on ancient igneous rocks. A mechanistic link between the marine Si cycle and off-axis H2production requires a reevaluation of the processes that supplied H2to prebiotic and early microbial systems, as well as those that balanced ocean–atmosphere redox through time.

From wood to vent: first cocculinid limpet associated with hydrothermal activity discovered in the Weddell Sea

2020 ◽  
Vol 32 (5) ◽  
pp. 354-366
Author(s):  
Chong Chen ◽  
Katrin Linse
Keyword(s):  
Hydrothermal Vents ◽  
Deep Ocean ◽  
First Record ◽  
Hydrothermal Activity ◽  
Integrative Taxonomy ◽  
Weddell Sea ◽  
Anatomical Reconstruction ◽  
Cold Seeps ◽  
Evolutionary Trajectory ◽  
Genetic Sequencing

AbstractLush ‘oases’ of life seen in chemosynthetic ecosystems such as hot vents and cold seeps represent rare, localized exceptions to the generally oligotrophic deep ocean floor. Organic falls, best known from sunken wood and whale carcasses, are additional sources of such oases. Kemp Caldera (59°42'S, 28°20'W) in the Weddell Sea exhibits active hydrothermal vents and a natural whale fall in close proximity, where an undescribed cocculinid limpet was found living in both types of chemosynthetic habitats. This represents the first member of the gastropod order Cocculinida discovered from hot vents, and also the first record from the Southern Ocean. Here, we applied an integrative taxonomy framework incorporating traditional dissection, electron microscopy, genetic sequencing and 3D anatomical reconstruction through synchrotron computed tomography in order to characterize this species. Together, our data revealed an unusual member of the genus Cocculina with a highly modified radula for feeding on bacterial film, described herein as Cocculina enigmadonta n. sp. Its phylogenetically derived position within the largely wood-inhabiting Cocculina indicates that it probably evolved from an ancestor adapted to living on sunken wood, providing a compelling case of the ‘stepping stone’ evolutionary trajectory from organic falls to seeps and vents.

Enhancement of RF Ablation by Combined Use of Ultra-Low Temperature Fluid Cooling and Magnetic Nanoparticles

2010 ◽  
Author(s):  
Zhong-Shan Deng ◽  
Jing Liu
Keyword(s):  
Magnetic Nanoparticles ◽  
Low Temperature ◽  
Bioheat Transfer ◽  
Rf Ablation ◽  
High Electrical Conductivity ◽  
Thermal Coagulation ◽  
Cooling Method ◽  
Tumor Tissues ◽  
Combined Use ◽  
Fluid Cooling

Magnetic nanoparticles with high electrical conductivity have been proved to be effective in enhancing the efficacy of RF ablation. However, the possible carbonization of tissues is an unfavorable factor in achieving greater dimensions of necrosis, because carbonized tissue is a poor conductor, increases impedance and limits propagation area of RF energy. To prevent potential carbonization of tissues surrounding to the heating part of RF electrodes during RF ablation, a new method using ultra-low temperature fluid was proposed for cooling RF electrodes and tissues in the vicinity of RF electrodes in this study. To test its feasibility, the corresponding bioheat transfer process during RF ablation simultaneously applying this cooling method and magnetic nanoparticles was studied through numerical simulations. The results indicate that the cooling method by ultra-low temperature fluid can prevent carbonization of tissues resulted by local high temperature, significantly enlarge the effective heating area and thus actualize highly efficient thermal coagulation to tumor tissues during RF ablation with adjuvant use of magnetic nanoparticles.

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