Geology of a submarine hydrothermal field, Mid-Atlantic Ridge, 26°n latitude

We examined the distribution of Fe, Mn, Cu, Zn, and Pb in one core of metalliferous, and one core of non-mineralized (background) carbonate sediments (located 69 km northwards), from the Pobeda hydrothermal field. Mechanisms of metal accumulation in sediments (12 samples) were evaluated based on sequential extraction of geochemical fractions, including mobile (exchangeable complex, authigenic Fe-Mn hydroxides, and sulfides), and lithogenic (fixed in crystalline lattices) forms. Maps of element distribution in sediment components were obtained using a scanning electron microscope equipped with an energy-dispersive spectrometry detector. In metalliferous sediments, according to X-ray diffraction data, the main Fe mineral phase was goethite FeOOH (37–44% on a carbonate-free basis). The contents of Fe and Mn reached 31.6 and 0.18%, respectively, whereas concentrations of Cu, Zn and Pb were 0.98, 0.36, and 0.059%. The coefficient of metal enrichment relative to background values varied from 16 to 125 times. The exception was Mn, for which no increased accumulation was recorded. Essential mass of Fe (up to 70% of total content) was represented by the residual fraction composed of crystallized goethite, aluminosilicates, the minerals derived from bedrock destruction processes. Among geochemically mobile fractions, 90–97% of total Fe was found in the form of authigenic oxyhydroxides. The same fraction was the predominant host for Mn in both metalliferous and background sediments (55–85%). A total of 40–96 % of Cd, Cu, Zn, and Pb were associated with these Fe and Mn fractions. The sulfide fraction amounted to roughly 10% of each metal. In metalliferous sediment core, the maximum concentrations of metals and their geochemically mobile fractions were recorded in deeper core intercepts, an observation that might be attributed to influence of hydrothermal diffused fluids. Our data suggested that metals are mostly accumulated in carbonate sediments in their contact zone with the underlying serpentinized basalts.

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Microbial ecology of the newly discovered serpentinite-hosted Old City hydrothermal field (southwest Indian ridge)

The ISME Journal ◽

10.1038/s41396-020-00816-7 ◽

2020 ◽

Cited By ~ 1

Author(s):

Aurélien Lecoeuvre ◽

Bénédicte Ménez ◽

Mathilde Cannat ◽

Valérie Chavagnac ◽

Emmanuelle Gérard

Keyword(s):

Microbial Ecology ◽

New Caledonia ◽

Southwest Indian Ridge ◽

Hydrothermal Field ◽

Metagenomic Sequencing ◽

Lost City ◽

Old City ◽

Mid Atlantic Ridge ◽

Indian Ridge ◽

Geochemical Analyses

Abstract Lost City (mid-Atlantic ridge) is a unique oceanic hydrothermal field where carbonate-brucite chimneys are colonized by a single phylotype of archaeal Methanosarcinales, as well as sulfur- and methane-metabolizing bacteria. So far, only one submarine analog of Lost City has been characterized, the Prony Bay hydrothermal field (New Caledonia), which nonetheless shows more microbiological similarities with ecosystems associated with continental ophiolites. This study presents the microbial ecology of the ‘Lost City’-type Old City hydrothermal field, recently discovered along the southwest Indian ridge. Five carbonate-brucite chimneys were sampled and subjected to mineralogical and geochemical analyses, microimaging, as well as 16S rRNA-encoding gene and metagenomic sequencing. Dominant taxa and metabolisms vary between chimneys, in conjunction with the predicted redox state, while potential formate- and CO-metabolizing microorganisms as well as sulfur-metabolizing bacteria are always abundant. We hypothesize that the variable environmental conditions resulting from the slow and diffuse hydrothermal fluid discharge that currently characterizes Old City could lead to different microbial populations between chimneys that utilize CO and formate differently as carbon or electron sources. Old City discovery and this first description of its microbial ecology opens up attractive perspectives for understanding environmental factors shaping communities and metabolisms in oceanic serpentinite-hosted ecosystems.

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High-resolution multibeam bathymetry of the northern Mid-Atlantic Ridge at 45–46° N: the Moytirra hydrothermal field

Journal of Maps ◽

10.1080/17445647.2021.1898485 ◽

2021 ◽

Vol 17 (2) ◽

pp. 184-196

Author(s):

Luis Somoza ◽

Teresa Medialdea ◽

Francisco J. González ◽

Sara Machancoses ◽

Jose A. Candón ◽

...

Keyword(s):

High Resolution ◽

Hydrothermal Field ◽

Multibeam Bathymetry ◽

Mid Atlantic Ridge

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Two New Caridean Shrimps (Bresiliidae) from a Hydrothermal Field on the Mid-Atlantic Ridge

Journal of Crustacean Biology ◽

10.2307/1548184 ◽

1986 ◽

Vol 6 (3) ◽

pp. 446 ◽

Cited By ~ 88

Author(s):

Austin B. Williams ◽

Peter A. Rona

Keyword(s):

Hydrothermal Field ◽

Mid Atlantic Ridge

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Covellite of the Semenov-2 hydrothermal field (13°31.13′ N, Mid-Atlantic Ridge): Enrichment in trace elements according to LA ICP MS analysis

Doklady Earth Sciences ◽

10.1134/s1028334x17030060 ◽

2017 ◽

Vol 473 (1) ◽

pp. 291-295 ◽

Cited By ~ 8

Author(s):

I. Yu. Melekestseva ◽

V. V. Maslennikov ◽

S. P. Maslennikova ◽

L. V. Danyushevsky ◽

R. Large

Keyword(s):

Trace Elements ◽

Hydrothermal Field ◽

Ms Analysis ◽

Icp Ms ◽

Mid Atlantic Ridge

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Sulfide Breccias from the Semenov-3 Hydrothermal Field, Mid-Atlantic Ridge: Authigenic Mineral Formation and Trace Element Pattern

Minerals ◽

10.3390/min8080321 ◽

2018 ◽

Vol 8 (8) ◽

pp. 321 ◽

Cited By ~ 5

Author(s):

Irina Melekestseva ◽

Valery Maslennikov ◽

Nataliya Safina ◽

Paolo Nimis ◽

Svetlana Maslennikova ◽

...

Keyword(s):

Trace Elements ◽

Hydrothermal Field ◽

Trace Element Pattern ◽

Modes Of Occurrence ◽

Element Pattern ◽

Authigenic Mineral ◽

Mid Atlantic Ridge ◽

Lower Temperature ◽

Hydrothermal Sulfides

The aim of this paper is the investigation of the role of diagenesis in the transformation of clastic sulfide sediments such as sulfide breccias from the Semenov-3 hydrothermal field (Mid-Atlantic Ridge). The breccias are composed of marcasite–pyrite clasts enclosed in a barite–sulfide–quartz matrix. Primary hydrothermal sulfides occur as colloform, fine-crystalline, porous and radial marcasite–pyrite clasts with inclusions or individual clasts of chalcopyrite, sphalerite, pyrrhotite, bornite, barite and rock-forming minerals. Diagenetic processes are responsible for the formation of more diverse authigenic mineralization including framboidal, ovoidal and nodular pyrite, coarse-crystalline pyrite and marcasite, anhedral and reniform chalcopyrite, inclusions of HgS phase and pyrrhotite–sphalerite–chalcopyrite aggregates in coarse-crystalline pyrite, zoned bornite–chalcopyrite grains, specular and globular hematite, tabular barite and quartz. The early diagenetic ovoid pyrite is enriched in most trace elements in contrast to late diagenetic varieties. Authigenic lower-temperature chalcopyrite is depleted in trace elements relative to high-temperature hydrothermal ones. Trace elements have different modes of occurrence: Se is hosted in pyrite and chalcopyrite; Tl is related to sphalerite and galena nanoinclusions; Au is associated with galena; As in pyrite is lattice-bound, whereas in chalcopyrite it is related to tetrahedrite–tennantite nanoinclusions; Cd in pyrite is hosted in sphalerite inclusions; Cd in chalcopyrite forms its own mineral; Co and Ni are hosted in chalcopyrite.

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