Fe-Mn Crusts Research Articles

Modern Bottom Sediments of Lake Onega: Structure, Mineralogical Composition, and Systematization of Rare-Earth Elements

The results of studying the structure and mineral composition of the Upper Holocene bottom sediments of Lake Onega are presented. It is established that there are two types of columns of bottom sediments, for which stratification of layers and formation of Fe–Mn crusts are determined by the diagenesis processes occurring under physicochemical conditions of sediment accumulation according to two scenarios. The distribution spectra of rare-earth elements (REEs) are different in the indicated types of columns, which is apparently attributed to the differences in the oxidation–reduction conditions at the water–sediment interface during the formation of REEs and possibly to the influence of hydrothermal processes.

Assessment of the Mineral Resource Potential of Atlantic Ferromanganese Crusts Based on Their Growth History, Microstructure, and Texture

The decarbonisation of our energy supply is reliant on new technologies that are raw material intensive and will require a significant increase in the production of metals to sustain them. Ferromanganese (FeMn) crusts are seafloor precipitates, enriched in metals such as cobalt and tellurium, both of which have a predicted future demand above current production rates. In this study, we investigate the texture and composition of FeMn crusts on Tropic Seamount, a typical Atlantic guyot off the coast of western Africa, as a basis for assessing the future mineral resource potential of Atlantic Seamounts. The majority of the summit is flat and covered by FeMn crusts with average thicknesses of 3–4 cm. The crusts are characterized by two dominant textures consisting of either massive pillared growth or more chaotic, cuspate sections of FeMn oxides, with an increased proportion of detrital and organic material. The Fe, Mn, and Co contents in the FeMn oxide layers are not affected by texture. However, detrital material and bioclasts can form about 50% of cuspate areas, and the dilution effect of this entrained material considerably reduces the Fe, Mn, and Co concentrations if the bulk samples are analyzed. Whilst Tropic Seamount meets many of the prerequisites for a crust mining area, the thickness of the crusts and their average metal composition means extraction is unlikely to be viable in the near future. The ability to exploit more difficult terrains or multiple, closely spaced edifices would make economic feasibility more likely.

High-Resolution Analysis of Critical Minerals and Elements in Fe–Mn Crusts from the Canary Island Seamount Province (Atlantic Ocean)

Two Fe–Mn crusts among 35 samples, from six seamounts in the Canary Island Seamount Province, were selected as representatives of the endpoint members of two distinct types of genetic processes, i.e., mixed diagenetic/hydrogenetic and purely hydrogenetic. High-resolution analyses pursued the main aim of distinguishing the critical elements and their association with mineral phases and genetic processes forming a long-lived Fe–Mn crust. The Fe–Mn crust collected on the Tropic Seamount is composed of dense laminations of Fe-vernadite (>90%) and goethite group minerals, reflecting the predominance of the hydrogenetic process during their formation. Based on high-resolution age calculation, this purely hydrogenetic crust yielded an age of 99 Ma. The Fe–Mn crust collected on the Paps Seamount shows a typical botryoidal surface yielding an age of 30 Ma. electron probe microanalyzer (EPMA) spot analyses show two main types of manganese oxides, indicating their origin: (i) hydrogenetic Fe-vernadite, the main Mn oxide, and (ii) laminations of interlayered buserite and asbolane. Additionally, the occurrence of calcite, authigenic carbonate fluor-apatite (CFA) and palygorskite suggests early diagenesis and pervasive phosphatization events. Sequential leaching analysis indicated that Co, Ni, Cu, Ba and Ce are linked to Mn minerals. Therefore, Mn-oxides are enriched in Ni and Cu by diagenetic processes or in Co and Ce by hydrogenetic processes. On the other hand, Fe-oxides concentrate V, Zn, As and Pb. Moreover, the evidence of HREE enrichment related to Fe-hydroxides is confirmed in the mixed hydrogenetic/diagenetic crust.

Main Stages of Evolution of Pacific Ferromanganese Stromatolites and Oncolites

As exemplified by cobalt–bearing Fe–Mn crusts (ferromanganese stromatolite) of the Magellan Seamounts (Clarion–Clipperton Province), the main stages of the structural evolution of bacterial communities have been recognized. It has been demonstrated that the change of the stages is caused by the effect of major tectonic, volcanic, and other geological events.

Accumulation of Platinum Group Elements in Hydrogenous Fe–Mn Crust and Nodules from the Southern Atlantic Ocean

Distribution of platinum group elements (Ru, Pd, Pt, and Ir) and gold in hydrogenous ferromanganese deposits from the southern part of the Atlantic Ocean has been studied. The presented samples were the surface and buried Fe–Mn hydrogenous nodules, biomorphous nodules containing predatory fish teeth in their nuclei, and crusts. Platinum content varied from 47 to 247 ng/g, Ru from 5 to 26 ng/g, Pd from 1.1 to 2.8 ng/g, Ir from 1.2 to 4.6 ng/g, and Au from less than 0.2 to 1.2 ng/g. In the studied Fe–Mn crusts and nodules, Pt, Ir, and Ru are significantly correlated with some redox-sensitive trace metals (Co, Ce, and Tl). Similar to cobalt and cerium behaviour, ruthenium, platinum, and iridium are scavenged from seawater by suspended ferromanganese oxyhydroxides. The most likely mechanism of Platinum Group Elements (PGE) accumulation can be sorption and oxidation on δ-MnO2 surfaces. The obtained platinum fluxes to ferromanganese crusts and to nodules are close and vary from 35 to 65 ng∙cm−2∙Ma−1. Palladium and gold do not accumulate in hydrogenous ferromanganese deposits relative to the Earth’s crust. No correlation of Pd and Au content with major and trace elements in nodules and crusts have been identified.

Rare earth elements and yttrium (REY) variability with water depth in hydrogenetic ferromanganese crusts

The origins of ferromanganese (Fe–Mn) crusts that form in seawater and elemental partitioning into these crusts have previously been studied using samples from water depths shallower than 4 km. Here we report geochemical analyses of Fe–Mn crusts sampled from petit-spot volcanoes within the Pacific Ocean at water depths of 5.2–6.0 km. The Fe–Mn crusts have low Mn/Fe ratios (0.63–1.5), high contents of Co, Ni, and rare earth elements and Y (REY), and positive Ce anomalies, indicating a hydrogenetic origin. The Fe–Mn crusts are characterized by lower shale-normalized La/Pr ratios (LaSN/PrSN) than typical hydrogenetic Fe–Mn crusts from the Pacific Ocean. Despite negative LaSN/PrSN and NdSN/SmSN and positive EuSN/GdSN and DySN/HoSN correlations with water depth, the distribution coefficients of the REY are constant. This indicates that the observed REY variability with water depth in these hydrogenetic Fe–Mn crusts reflects that of seawater. In particular, a strong correlation between LaSN/PrSN and water depth has potential for use as a (paleo)ocean hydro-barometer. The variety of REY compositions of Fe–Mn crusts should be interpreted on the basis of distribution coefficients calculated for each water depth.

Cover: Journal of Basic Microbiology. 5/2018

Journal of Basic MicrobiologyVolume 58, Issue 5 COVER PICTUREFree Access Cover: Journal of Basic Microbiology. 5/2018 First published: 03 May 2018 https://doi.org/10.1002/jobm.201870018AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover illustration: Scanning electron microscopic image of intermediate portion of Fe-Mn crust recovered from the ‘Christmas Tree’ hydrothermal field, northern Lau back-arc basin reveals microbial aggregation leading to the formation of filament-like structures. The filaments are encrusted in exopolymeric material secreted by autochthonous microbes which acts as a nucleation site for deposition of metal oxides. In hydrothermal systems, microbes could thus be playing an important role in controlling the chemistry of metal ions in the aquatic system and aiding in the formation of metal oxides. (Photo: V. D. Khedekar, CSIR-National Institute of Oceanography, Goa, India) Volume58, Issue5May 2018 RelatedInformation

Fossilized Bacteria in Fe-Mn-Mineralization: Evidence from the Legrena Valley, W. Lavrion Mine (Greece)

The primary mineralization in the famous Lavrion mine in the Lavreotiki area, Attica (Greece), associated with a granodiorite intrusion of Upper Miocene age and composed of massive sulphide Pb-Zn-Ag ores [sphalerite, pyrite and galena (B.P.G)], has been extensively studied. The present study is focused on thin, hard, dark brown to black Fe-Mn crusts (a few mm to cm in thickness) in the Legrena valley, SW Lavreotiki, aiming to provide new insights on that type of Fe-Mn-mineralization. The scanning electron microscope (SEM)/energy dispersive spectroscopy (EDS) data presented revealed the presence of fine rounded fragments, resembling nodules (up to 200 μm) and fossilized bacteriomorphic Fe-Mn-oxides/hydroxides, within brecciated and foliated zones of carbonate rocks. They exhibit unusual features when compared to the common massive Fe-Mn mineralization with regards the following: (a) the extensive occurrence of bacteriomorphic Fe-oxides/hydroxides and their micro-textures; and (b) the minor elements (K, Na, P, S, Ca, As and Cl). The occurrence of abundant bacteriomophic Fe-Mn-oxides/hydroxides in the samples from the Legrena valley may reflect their catalytic role in the redox reactions during ore-forming processes. The characteristic features of that type of Fe-Mn mineralization seems to be the result of multistage supergene processes superimposed over initial hydrothermal stages. Such a multistage remobilization and precipitation of metals along open space surfaces on karstified carbonates during a subsequent stage of their initial precipitation may be widespread in the Attica region, Greece.

Abnormally high mercury contents in hydrogenic ferromanganese crusts from Seth Guyot (Northwestern Pacific)

Variations in mercury contents in marine sediments have implications for hydrothermal activity, paleoclimate, depositional environments, and primary bioproduction. Mercury contents reach 148 ppb in hydrogenic ferromanganese crusts on flat-topped seamounts. Such crusts, with up to 4120 ppb Hg, were dredged from the slopes of Seth Guyot in the western Marcus-Wake Seamounts in 1982, during the 13th cruise of RV Vulkanolog. The Seth Fe-Mn crusts are of the same origin as hydrogenic Co-rich ferromanganese deposits from seamounts in other oceanic regions. Mercury accumulated in the Cenozoic as Fe-Mn oxyhydroxides in the crusts adsorbed Hg from bottom water. The process was especially rapid during the Pliocene volcano-tectonic rejuvenated stage.

Heterogeneity of Microbial Communities on Deep-Sea Ferromanganese Crusts in the Takuyo-Daigo Seamount.

Rock outcrops of aged deep-sea seamounts are generally covered with Fe and Mn oxides, known as ferromanganese (Fe–Mn) crusts. Although the presence of microorganisms in Fe–Mn crusts has been reported, limited information is currently available on intra- and inter-variations in crust microbial communities. Therefore, we collected several Fe–Mn crusts in bathyal and abyssal zones (water depths of 1,150–5,520 m) in the Takuyo-Daigo Seamount in the northwestern Pacific, and examined microbial communities on the crusts using culture-independent molecular and microscopic analyses. Quantitative PCR showed that microbial cells were abundant (106–108 cells g−1) on Fe–Mn crust surfaces through the water depths. A comparative 16S rRNA gene analysis revealed community differences among Fe–Mn crusts through the water depths, which may have been caused by changes in dissolved oxygen concentrations. Moreover, community differences were observed among positions within each Fe–Mn crust, and potentially depended on the availability of sinking particulate organic matter. Microscopic and elemental analyses of thin Fe–Mn crust sections revealed the accumulation of microbial cells accompanied by the depletion of Mn in valleys of bumpy crust surfaces. Our results suggest that heterogeneous and abundant microbial communities play a role in the biogeochemical cycling of Mn, in addition to C and N, on crusts and contribute to the extremely slow growth of Fe–Mn crusts.

Formation and Occurrence of Ferromanganese Crusts: Earth's Storehouse for Critical Metals

Marine ferromanganese oxide crusts (Fe–Mn crusts) are potentially important metal resources formed on the seafloor by precipitation of dissolved and colloidal components from ambient seawater onto rocky surfaces. The unique properties and slow growth rates of the crusts promote adsorption of numerous elements from seawater: some, such as Te and Co, reach concentrations rarely encountered elsewhere in nature. Consequently, Fe–Mn crusts are potential sources of metals used in technologies considered essential for the transition to a low-carbon economy. However, the precise distributions and metal concentrations of Fe–Mn crusts at regional and local scales are poorly constrained because of the diversity of geological, oceanographic and chemical processes involved in their formation.

Magnetic stratigraphic dating of marine hydrogenetic ferromanganese crusts

Deep-sea hydrogenetic ferromanganese crusts are both potential polymetallic resources and records of long-term environmental changes. For palaeoceanographic studies, it is important to construct a detailed and reliable chronological framework. Here, we report the results of a detailed magnetostratigraphic and rock magnetic study of four hydrogenetic Fe-Mn crusts from the Pacific Ocean (PO-01), South China Sea (SCS-01, SCS-02) and Indian Ocean (IO-01). Two groups of characteristic remanent magnetization directions were defined with nearly antipodal normal and reversed polarities for samples PO-01, SCS-01 and SCS-02, indicating a primary record of the Earth’s magnetic field. The magnetostratigraphic framework, established via correlation with the Geomagnetic Polarity Time Scale 2012, implies growth rates of 4.82 mm/Ma, 4.95 mm/Ma, 4.48 mm/Ma and 11.28 mm/Ma for samples PO-01, SCS-01, SCS-02 and IO-01, respectively. Rock magnetic measurements revealed that the Fe-Mn crust samples from the Pacific Ocean and Indian Ocean were dominated by low coercivity, non-interacting, single-domain (SD) magnetite particles, whereas the South China Sea samples were dominated by SD/pseudo-single-domain (PSD) particles. Multidomain (MD) magnetite may also be present in all samples.

Metal cation exchange reactions of ore minerals in Fe–Mn crusts of the Marcus Wake Rise (Pacific Ocean) in aqueous–salt solutions

It is shown that the reaction ability of metal cations of ore minerals in Fe–Mn crusts of the Marcus Wake Rise increases in the following manner: (Co2+ < Cu2+ < Ni2+) < (Mg2+ < Mn2+ < K+ ≈ Ca2+ ≈ Na+). The composition of the exchange complex of the ore minerals is constant and includes these metal cations. Ca2+ and Na+ are major contributors to the exchange capacity of the ore minerals. The capacity of the ore minerals by cations of alkali and base metals is 0.43–0.60 and 2.08–2.70 mg-equiv/g, respectively. The exchange capacity of the ore minerals by cations of base metals increases linearly with the increase in the MnO2 content of the crust and does not depend on the geographical locations of the Marcus Wake guyots.

Depositional Age of a Fossil Whale Bone from São Paulo Ridge, South Atlantic Ocean, Based on Os Isotope Stratigraphy of a Ferromanganese Crust

AbstractWhale carcasses (whale falls) deposited on the deep seafloor are associated with a distinctive biotic community. A fossil whale bone recovered from São Paulo Ridge, South Atlantic Ocean, during cruise YK13–04 Leg 1 of R/V Yokosuka was covered by a ferromanganese (Fe–Mn) crust approximately 9 mm thick. Here, we report an age constraint for this fossil bone on the basis of Os isotopic stratigraphy (187Os/188Os ratio) of the Fe–Mn crust. Major‐ and trace‐element compositions of the crust are similar to those of Fe–Mn crusts of predominantly hydrogenous origin. Rare earth element concentrations in samples of the crust, normalized with respect to Post‐Archean average Australian Shale, exhibit flat patterns with positive Ce and negative Y anomalies. These results indicate that the Fe–Mn crust consists predominantly of hydrogenous components and that it preserves the Os isotope composition of seawater at the time of its deposition. 187Os/188Os ratios of three Fe–Mn crust samples increased from 0.904 to 1.068 in ascending stratigraphic order. The value of 1.068 from the surface slice (0–3 mm depth in the crust) was identical to that of present‐day seawater within error (~1.06). The value of 0.904 from the basal slice (6–9 mm) equaled seawater values from ca. 4–5 Ma. Because it is unknown how long the bone lay on the seafloor before the Fe–Mn crust was deposited, the Os stratigraphic age of ca. 5 Ma is a minimum age of the fossil. This is the first application, to our knowledge, of marine Os isotope stratigraphy for determining the age of a fossil whale bone. Such data may offer valuable insights into the evolution of the whale‐fall biotic community.

Marine Ferromanganese Encrustations: Archives of Changing Oceans

Marine iron–manganese oxide coatings occur in many shallow and deep-water areas of the global ocean and can form in three ways: 1) Fe–Mn crusts can precipitate from seawater onto rocks on seamounts; 2) Fe–Mn nodules can form on the sediment surface around a nucleus by diagenetic processes in sediment pore water; 3) encrustations can precipitate from hydrothermal fluids. These oxide coatings have been growing for thousands to tens of millions of years. They represent a vast archive of how oceans have changed, including variations of climate, ocean currents, geological activity, erosion processes on land, and even anthropogenic impact. A growing toolbox of age-dating methods and element and isotopic signatures are being used to exploit these archives.

Microbial activity promotes the enrichment of cobalt over nickel on hydrogenetic ferromanganese crusts

ABSTRACTThe different mineral phases of the ferromanganese (Fe–Mn) crusts stem from the interaction of biotic and abiotic components. It is therefore vital to study the activity of these components to decipher their contribution to the enrichment/depletion of metals in the crust. Thus, the present study examined sorption and release of Co and Ni by Fe-Mn crusts with associated microbial communities in the presence and absence of the metabolic poison sodium azide (15 mM). The study was conducted in the presence (G+) and absence (G−) of added glucose (0.1%) at temperatures of 4 ± 1°C and 28 ± 2°C. Results showed that the microbial community had maximal sorption of Co of 66.12 µg g−1 at 4 ± 1°C in the absence of added glucose and 479.75 µg g−1 at 28 ± 2°C in the presence of added glucose. Maximum sorption of Ni in the absence of added glucose was 1.89 µg g−1 at 4 ± 1°C and release of Ni was 51.28 µg g−1 in the presence of added glucose. Under abiotic conditions with 15 mM sodium azide as a metabolic inhibitor, significant amounts of Co and Ni were released in the G+ medium. Total cell counts on the Fe-Mn crust in the presence of added glucose increased by an order of magnitude from 106 to 107 cells g−1 and in the absence of added glucose remained within the order of 106 cells g−1 irrespective of temperature of incubation. Microscopic observation of the samples from biotic incubations showed numerous bacterial cells, exopolysaccharides, and structures resembling secondary minerals formed by bacteria. The results indicate that bacteria promote the enrichment of Co and Ni on the hydrogenetic Fe-Mn crusts by sorption processes and release of Ni by reductive dissolution of the oxides. The higher enrichment of Co than Ni is attributed to the way in which microbes interact with the metals.

Bacterial activity in hydrogenetic ferromanganese crust from the Indian Ocean: a combined geochemical, experimental and pyrosequencing study

The Afanasiy-Nikitin Seamount (ANS) in the Equatorial Indian Ocean harbors hydrogenetic ferromanganese (Fe–Mn) crusts. It was hypothesized that the bacteria associated with the crust catalyze the precipitation of metal hydroxides in seawater more than abiotic dissolution, contributing to hydrogenetic accretion on the seamount. To test this hypothesis, Fe–Mn crust samples were collected from the flanks of the ANS. Geochemical properties of water samples collected were analyzed, and simulatory laboratory experiments were conducted to quantify bacterial accretion rates. Pyrosequencing was used to delineate the community associated with the crust. The environmental parameters of the water column indicated significant differences (p Mn (0.63) > Ni (0.003) > Co (0.002 mg g−1) with added glucose (0.01%) and Fe (9.09) > Mn (0.87) > Ni (0.0043) > Co (0.0008 mg g−1) without added glucose. Unlike the hydrothermal vent sites of the Pacific where e- and ζ-Proteobacteria were reported to be dominant, the hydrogenetic Fe–Mn crusts of the ANS revealed sequences related to known Fe-, Mn- and S-oxidizing bacteria of the γ- and α-Proteobacterial groups. Thus, the different selective pressures in the two environments could be one of the factors that have brought about a difference in their bacterial diversity. Besides, the ambient nutrient levels could have triggered the participation of the Proteobacterial community of the ANS in the precipitation of Fe–Mn rich minerals.

The Oligocene gap in the formation of Co-rich ferromanganese crusts and sedimentation in the Pacific Ocean and the effects of bottom currents

The Marcus Wake and Magellan guyots formed about 129–74 Ma ago at 10°–30° S and drifted 1700–4400 km to their present-day latitudinal position across the equatorial zone of maximum deposition. Cooling of the Pacific plate brought these guyots to the northern arid zone during the Turonian–Maastrichtian, to depths at which sediment accumulation rates were low and the conditions promoted precipitation of Co-rich Fe–Mn crusts from the Campanian to the present. Nonprecipitation of Co-rich Fe–Mn crusts during the Oligocene was caused by the action of bottom currents. The presence of a hiatus identified in cores from drill holes was used as the basis for reconstruction of the directions of bottom currents in the Oligocene.

Thallium elemental behavior and stable isotope fractionation during magmatic processes

Stable thallium (Tl) isotopes are an extremely sensitive tracer for the addition of small amounts of sediments or materials altered at low temperatures to the source(s) of mantle-derived melts. The ability of Tl to trace such materials is due to the large concentration contrast between the mantle (Tl<2ng/g) and possible exotic inputs (Tl~100ng/g to >μg/g), which also often display fractionated Tl isotope compositions. However, the magnitude of Tl isotope fractionation induced by igneous processes alone has not been systematically assessed. Here, two suites of co-genetic magmas, spanning a large range of differentiation, from Hekla, Iceland, and Anatahan, in the Mariana arc, are used to assess the behavior of thallium and its stable isotope variations during magmatic processes. Thallium behaves as a near-perfectly incompatible lithophile element throughout magmatic evolution, mirroring elements such as Rb, Cs, and K. Lavas from Hekla have restricted Cs/Tl ratios and stable Tl isotope compositions, which overlap with mantle estimates. Lavas from subduction-related Anatahan volcano also have a restricted range in Tl isotope composition, which overlaps with Hekla and MORB, demonstrating that fractional crystallisation and partial melting does not fractionate stable Tl isotopes. Subduction environments display variable Cs/Tl, indicating that the subduction process commonly fractionates these two elements. The immunity of thallium stable isotopes to fractionation by magmatic processes coupled with its extreme sensitivity for tracing pelagic sediments, FeMn crusts and low temperature altered oceanic crust highlight its value in elucidating the nature of mantle sources of both oceanic basalts and arc lavas. Critically, meaningful interpretation of thallium isotope compositions need not be restricted to primitive lavas.

Paleoceanographic conditions on the São Paulo Ridge, SW Atlantic Ocean, for the past 30 million years inferred from Os and Pb isotopes of a hydrogenous ferromanganese crust

Hydrogenous ferromanganese (Fe-Mn) crusts can provide records of long-term environmental changes during the Cenozoic. To understand the paleoceanographic conditions in the southwestern Atlantic Ocean, we investigated depth profiles of major- and trace-element concentrations as well as Os and Pb isotopic compositions in a Fe-Mn crust collected from the southern flank of the São Paulo Ridge in the southwestern Atlantic. Major and trace element data plotted on ternary Mn–Fe–10×(Ni+Co+Cu) and rare-earth element plus yttrium (REY) discrimination diagrams indicate that the analyzed sample is a typical hydrogenous Fe-Mn crust. The obtained 187Os/188Os data were matched to the Cenozoic seawater Os isotope evolution curve reconstructed from pelagic sediments. The result suggests that the Fe-Mn crust has accreted over ~30Myr with growth rates of 0.5–3mm/Myr, although the sample likely grew in two directions during the early stage of its growth. We found no evidence of growth hiatus in the sample, which may contrast with the growth histories of many Pacific Fe-Mn crusts. Hence, the conditions favorable for the accretion of hydrogenous Fe-Mn crusts were likely to have developed on the São Paulo Ridge over the past ~30Myr. The Pb isotopic compositions show very limited ranges (e.g., 206Pb/204Pb=18.80–18.85), and are similar to those of pre-anthropogenic seawater in the Southern Ocean. As the São Paulo Ridge is located near the Vema Channel, which is presently a major path of Antarctic Bottom Water, we suggest that a strong northward bottom current has continuously swept detrital and biogenic sediments from the ridge, and played a vital role in the Fe-Mn crust formation since ~30Ma.