Mn Crusts Research Articles

Petrography and stratigraphic Os isotopic ages of ferromanganese nodules from the Northwest Pacific east of Minamitorishima Island

The area offshore of Minamitorishima Island, Northwestern Pacific Ocean, contains large amounts of seafloor mineral resources such as ferromanganese (Fe–Mn) nodules, Fe–Mn crusts, and rare-earth element and yttrium (REY)-rich muds. In this study, we applied stratigraphic Os isotopic dating to a Fe–Mn nodule for the first time to date its formation/depositional age, and mineralogical and texturally characterized a complementary nodule. Based on macroscopic and microscopic observations, the studied Fe–Mn nodules can be divided into three layers: Layers L2, L1, and L0 from core to rim. Under the microscope, the Fe–Mn nodules are dominated by vernadite and Fe-oxyhydroxide. In particular, Layer L1 is dominated by banded-columnar vernadite and contains lower amounts of clay minerals derived from the detrital component than Layers L2 and L0. The bulk major and trace element geochemical compositions of sampled layers in the Fe–Mn nodules all plotted in the hydrogenous field in several discrimination diagrams. The Os isotopic ages determined by fitting to the paleo-seawater 187Os/188Os curve can be divided into three clusters (35.7–31.0, 19.0–9.0, and 4.0–1.0 Ma, corresponding to Layers L2, L1, and L0, respectively). These Os isotopic ages indicate that two periods of very slow growth or growth hiatuses occurred during the formation of the Fe–Mn nodule; these age gaps are related to the intermittent (discontinuous) timings of the beginning of Fe–Mn nodule formation offshore Minamitorishima Island.

Geochemistry of Iron-Manganese Crusts of the Bering Sea

The ferromanganese crusts found in the Bering Sea on the Volcanology Massif, the Alpha Fault Zone, and the Shirshov Submarine Ridge that cover the surface of rocky volcanic structures are most likely the product of post-volcanic activity. The present results indicate that the studied ferromanganese formations were formed under the influence of two factors: on the one hand–as a result of slow precipitation of metals from ordinary seawater, on the other hand–under the possible influence of metal-enriched hydrothermal solutions. In microstructural and mineralogical terms, the composition of Fe–Mn crusts of the Bering Sea turned out to be rather monotonous. The ore part is represented mainly by ferruginous vernadite and rarely hematite in combination with amorphous silica, to a lesser extent montmorillonite, calcite, and aragonite. The manganese mineral todorokite, considered a reliable sign of hydrothermal origin of ore crusts, was not detected in our samples. In the studied samples the reduced cerium anomaly (0.87) was established only in one sample, and in other samples its value varies within 1.08–1.89, which is typical for the upper horizons of the ocean water column. At the same time, the europium anomaly is close to neutral, so in 7 samples its value is 0.96–1.03 (average 1.0) and only in three samples it is slightly increased (1.05–1.07), which can be considered a very weak sign of hydrothermal activity. In addition, the presence of gold microinclusions in the ferromanganese phase can indirectly indicate the possible influence of hydrothermal factor on the crust composition.

Factors controlling rare earth element plus yttrium enrichment in Fe[sbnd]Mn crusts from Canary Islands Seamounts (NE Central Atlantic)

Marine minerals are important because concentrate in their structure high contents of strategic and critical elements as rare earth elements. Forty-two samples from eight seamounts of Canary Islands Seamount Province (CISP) have been analyzed in order to evaluate their rare earth elements plus yttrium contents (REY). Highest contents of REY are related to hydrogenetic minerals and essentially Fe-vernadite (on average 3000 μg/g). Diagenetic minerals, on the other hand, show the lowest REY contents with an average content of 260 μg/g. These differences also depend on the growth rates, hydrogenetic minerals with growth rates between 0.5 and 5 mm/Ma allow the incorporation of more REY in their structure. REY contents in studied samples varies depending several factors associated with depth and location, shallowest samples presumably growth near or within the oxygen minimum zone are the most enriched with up to 3800 μg/g due to local enrichment of these elements and the slowest growth rate promoted by the reduced ambient conditions while deeper samples around 3000 m water depth show 2800 μg/g. Location also has a role in REY contents essentially due to the presence of different currents. Samples faced to north are exposed to the more oxygenated waters of the North Atlantic Deep Water and are depleted in REY if compared with deeper samples facing to south to the more oxic Antarctic Bottom Water. Finally, the case of study made on three different seamounts of the CISP show that FeMn crusts from this area could provide on average 130 tons of hydrometallurgical recovered REY (based on 1 km2 areal crust coverage) together with interesting quantity of several other strategic and base elements as Mn, Co, Ni, Cu, V, Mo between others.

Genesis of ferromanganese nodules associated with mud volcanoes in the southeastern Dongsha waters of the northern South China Sea: Implications for regional deep Mesozoic hydrocarbon prospects

The Dongsha waters of the South China Sea are the location of thick Mesozoic deposits and many mud volcanoes that suggest hydrocarbon accumulation. Knowledge of the mechanism, fluid source and evolution of these mud volcanoes, however, remains inadequate. Ferromanganese nodules have been sampled from several deep-water mud volcanoes in waters around Southeast Dongsha island and provide a unique opportunity to study the fluid origin and evolution of the mud volcanoes in the area. In this contribution, the petrology, geochemistry and C–O isotopes of fluid inclusions in the nodules have been analyzed. The ferromanganese nodules are composed of distinct black Fe–Mn crust layers and light-yellow nucleus that contain quartz that hosts fluid inclusions. The outermost layers mainly consist of iron manganese minerals with high Mn/Fe ratios (0.9∼1.57), whereas the nucleus are dominated by siliceous debris. Positive Ce anomalies (δCe: 1.45∼2.13) and negative Y anomalies in growth layers indicate an anoxic environment, which is conducive to hydromanganite precipitation. In contrast, negative Ce anomalies (δCe: 0.27∼0.96) and positive Y anomalies in the nucleus suggest oxidized conditions. The absence of obvious Eu anomalies may be related to low-temperature hydrothermal conditions. The nucleus is enriched in δ13C (−2.59∼1.09‰) and weakly depleted in δ18O (−4.94∼0.89‰), whereas the growth layers are strongly depleted both in δ13C (−16.94∼–12.57‰) and δ18O (−23.05∼–17.48‰). These values indicate that carbon in the nucleus is mainly inorganic carbon from volcanism, whereas the carbon in the growth layers is related to the leakage of deep old hydrocarbon. The fluid inclusions in the quartz from the nucleus show records of at least two periods of CO2-rich hydrothermal activity and an origin from deep Mesozoic strata before release by mud volcanism. Given the widespread mud volcanism, the quartz from the nucleus may come from debris carried by mud volcano eruptions; the quartz also experienced diagenesis related with micro-organisms. The growth layers are considered to be hydrogenic and affected by the leakage of mature thermogenic hydrocarbons from deep old strata. These findings provide insights into deep mature hydrocarbon sources and thermogenic activity and improve understanding of mud volcanism and deep oil and gas resources in the southeastern Dongsha waters.

A high-resolution Os-Nd-Pb isotopic record of a hydrogenous Fe[sbnd]Mn crust from the Northwestern Pacific and its response to plate motion

Ferromanganese crusts are ideal archives of the isotopic composition of ambient deep waters. The cause of the long-term variations of Nd and Pb in the North Pacific deep water has not been well constrained because of a lack of reliable dating method. In this study, we documented the long-term Sr-Os-Nd-Pb isotopic evolution and major elements chemistry of a ferromanganese crust that grew in Northwestern Pacific deep water. The crust was dated using Os isotopic stratigraphy and has a maximum age of 86 Ma. In the early Cenozoic, εNd values increased from −5.3 to −4.0, and the Pb isotope ratios decreased, which can be explained by an input from the margin of South America that contributed both Nd and Pb to the Pacific deep water. The synchronous variations of Nd and Pb isotopic compositions were relate to the reduction of the source. Since Miocene, εNd value trended to more radiogenic values of −4.8 to −3.3 with oscillation owe to the decreased and pulsed input of the southern component water into the Pacific caused by the closure of the Indonesian seaway. The Pb isotope ratios increased after 35 Ma but remained lower than those of central North Pacific crusts. The Pb isotopic compositions did not respond to the one order of magnitude increase in dust flux and increase of Al content along with Pb isotope ratios since 10 Ma, which support that the arc-derived Pb dominated the Pb isotopic signature as the crust moved from the southern to northern Pacific, although Asian dust may have contributed to the Pb budget.

Seafloor Observations Eliminate a Landslide as the Source of the 1918 Puerto Rico Tsunami

ABSTRACT The 11 October 1918 devastating tsunami in northwest Puerto Rico had been used as an example for earthquake-induced landslide tsunami hazard. Three pieces of evidence pointed to a landslide as the origin of the tsunami: the discovery of a large submarine landslide scar from bathymetry data collected by shipboard high-resolution multibeam sonar, reported breaks of submarine cable within the scar, and the fit of tsunami models to flooding observations. Newly processed seafloor imagery collected by remotely operated vehicle (ROV) show, however, pervasive Fe–Mn crust (patina) on the landslide walls and floor, indicating that the landslide scar is at least several hundred years old. C14 dates of sediment covering the landslide floor verify this interpretation. Although we have not searched the region systematically for an alternative tsunami source, we propose a possible source—a two-segment normal-fault rupture along the eastern wall of Mona rift. The proposed fault location matches the published normal faults with steep bathymetry and is close to the International Seismological Center–Global Earthquake Model catalog locations of the 1918 mainshock and aftershocks. The ROV observations further show fresh vertical slickensides and rock exposure along the proposed fault trace. Hydrodynamic models from an Mw 7.2 earthquake rupture along the eastern wall of the rift faithfully reproduce the reported tsunami amplitudes, polarities, and arrival times. Our analysis emphasizes the value of close-up observations and physical samples to augment remote sensing data in natural hazard studies.

Hydrothermal Genesis of Fe–Mn Crust in the Southernmost Segment of the Mohns Ridge, Norwegian Sea: REE Geochemistry and Sr and Nd Isotopic Composition

Hydrothermal Genesis of Fe–Mn Crust in the Southernmost Segment of the Mohns Ridge, Norwegian Sea: REE Geochemistry and Sr and Nd Isotopic Composition

87Sr/86Sr Isotopic Ratio of Ferromanganese Crusts as a Record of Detrital Influx to the Western North Pacific Ocean

In this study, the Sr isotope ratios (IRs; 87Sr/86Sr) of ferromanganese (Fe–Mn) crusts are analyzed through laser ablation inductively coupled plasma multiple-collector mass spectrometry. A sample collected from off Minamitorishima Island showed uniform Sr IRs (0.70906–0.70927) similar to that of present-day seawater with more than 36 mm thickness. Meanwhile, a detritus-rich sample collected from off northeast (NE) Japan showed a wide variation in Sr IRs (0.707761–0.709963). The Sr IR variation in the Fe–Mn crust from off NE Japan suggests detrital influx contributions from both the NE Japan arc (<0.708) and aeolian dust from China (>0.718). Detrital flux from the NE Japan arc increases from the bottom to middle layers, possibly due to the uplift of the Ou backbone range that occurred after ~2 Ma. The increased influx of the aeolian dust in the outer layer is attributable to global cooling in the Quaternary that increased the loess dust transportation from China to the western North Pacific Ocean. Meanwhile, the influence of the detrital influx on the sample from off Minamitorishima Island appeared to be negligible. The Sr IR analysis with high spatial resolution proposed in this study possibly improves the burial history of Fe–Mn nodules.

R-Process Radioisotopes from Near-Earth Supernovae and Kilonovae

Abstract The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron star mergers (kilonovae (KNe)) contribute, and some classes of core-collapse supernovae (SNe) are also possible sources of at least the lighter r-process species. The discovery of 60Fe on the Earth and Moon implies that one or more astrophysical explosions have occurred near the Earth within the last few million years, probably SNe. Intriguingly, 244Pu has now been detected, mostly overlapping with 60Fe pulses. However, the 244Pu flux may extend to before 12 Myr ago, pointing to a different origin. Motivated by these observations and difficulties for r-process nucleosynthesis in SN models, we propose that ejecta from a KN enriched the giant molecular cloud that gave rise to the Local Bubble, where the Sun resides. Accelerator mass spectrometry (AMS) measurements of 244Pu and searches for other live isotopes could probe the origins of the r-process and the history of the solar neighborhood, including triggers for mass extinctions, e.g., that at the end of the Devonian epoch, motivating the calculations of the abundances of live r-process radioisotopes produced in SNe and KNe that we present here. Given the presence of 244Pu, other r-process species such as 93Zr, 107Pd, 129I, 135Cs, 182Hf, 236U, 237Np, and 247Cm should be present. Their abundances and well-resolved time histories could distinguish between the SN and KN scenarios, and we discuss prospects for their detection in deep-ocean deposits and the lunar regolith. We show that AMS 129I measurements in Fe–Mn crusts already constrain a possible nearby KN scenario.

The sequestration of trace metals preserved in pyritized burrows

Pyritized burrows from three localities were analysed using LA-ICP-MS to determine their trace element content and assess their ability to sequester trace elements. Pyritic burrows from Hock Cliff (Jurassic), Wren's Nest (Silurian) and Southerham Grey Pit (Cretaceous) have anomalous levels of Se, Cu and Pb and are enriched relative to their host sediments. Sequestration rates were calculated using sedimentation rates from similar depositional environments. Results show that pyritic burrows, mediated by bacterial sulphate reduction, can sequester Se, Cu and Pb up to 3 orders of magnitude greater than the rate of Fe–Mn crusts, which are considered rich sources of trace elements, demonstrating that bioturbated marine sediments are significant sinks of trace elements.

Accumulation and Enrichment of Platinum Group Elements in Hydrogenous Fe–Mn Crust and Nodules from The Andaman Sea, India

Accumulation and Enrichment of Platinum Group Elements in Hydrogenous Fe–Mn Crust and Nodules from The Andaman Sea, India

Nature of Native Gold in Ferromanganese Crusts on the Seafloor of the Northwestern Pacific Ocean

SEM-EDS analysis of cobalt-rich Fe–Mn crusts (CRFMC) and their substrate rocks from the Gummy Bear seamount in the northwestern Pacific Ocean and the Magellan seamounts (Ilyicheva and Vulcanologist guyots) in the subequatorial Pacific Ocean revealed the presence of accessory (0.6–40 μm) two- and three-component minerals of the Ag–Au–Cu system, which is indicative of a wider distribution of authigenic gold mineralization than one would expect for such deposits. A concept for the biogeochemical genesis of these natural alloys was proposed, including the processes of biosorption, bioaccumulation, and biotransformation of metal ions by microbial cells to their metallic nano- and microforms.

Microbial Diversity of Deep-Sea Ferromanganese Crust Field in the Rio Grande Rise, Southwestern Atlantic Ocean.

Seamounts are often covered with Fe and Mn oxides, known as ferromanganese (Fe-Mn) crusts. Future mining of these crusts is predicted to have significant effects on biodiversity in mined areas. Although microorganisms have been reported on Fe-Mn crusts, little is known about the role of crusts in shaping microbial communities. Here, we investigated microbial communities based on 16S rRNA gene sequences retrieved from Fe-Mn crusts, coral skeleton, calcarenite, and biofilm at crusts of the Rio Grande Rise (RGR). RGR is a prominent topographic feature in the deep southwestern Atlantic Ocean with Fe-Mn crusts. Our results revealed that crust field of the RGR harbors a usual deep-sea microbiome. No differences were observed on microbial community diversity among Fe-Mn substrates. Bacterial and archaeal groups related to oxidation of nitrogen compounds, such as Nitrospirae, Nitrospinae phyla,Candidatus Nitrosopumilus within Thaumarchaeota group, were present on those substrates. Additionally, we detected abundant assemblages belonging to methane oxidation, i.e., Methylomirabilales (NC10) and SAR324 (Deltaproteobacteria). The chemolithoautotrophs associated with ammonia-oxidizing archaea and nitrite-oxidizing bacteria potentially play an important role as primary producers in the Fe-Mn substrates from RGR. These results provide the first insights into the microbial diversity and potential ecological processes in Fe-Mn substrates from the Atlantic Ocean. This may also support draft regulations for deep-sea mining in the region.

Platinum Group Element Geochemistry in Ferromanganese Crust of the Detroit Guyot, Pacific Ocean

Abstract—Hydrogenetic Fe–Mn crusts in the ocean are enriched in platinum but do not accumulate palladium. The mechanism of platinum input into the crusts remains debatable. There is even less data on ruthenium and iridium. In this article, the distribution of platinum group elements (Pd, Ru, Ir, Pt) in ferromanganese crusts of the Detroit guyot (Northwest Pacific) is studied. Based on correlation analyses of major and trace elements, it was shown that accumulation of PGE (Ru, Ir, Pt) occurs from hydrogenetic particulate Fe–Mn oxyhydroxides on all layers with exception of the bottom layer. High platinum contents in the bottom layer are also associated with its input from seawater. However, the most probable additional source of platinum was halmirolysis of underlying basalts.

Manganese nodules NOD-A-1 and NOD-P-1: Implications of pre-treatment on oxygen isotopes and mineralogy

Manganese nodules are a type of ferromanganese chemical precipitate containing a plethora of economically important metals increasingly being used in the high- and green-technology sectors. By measuring oxygen isotope ratios in these materials, we can increase our understanding of how they form, and constrain which metals are likely to be present in them. There is a lack of suitable reference materials for use in oxygen isotopic studies of samples dominated by Mn oxide minerals (i.e., Mn nodules and crusts) and, therefore, a need for their development. The samples NOD-A-1 and NOD-P-1 (United States Geological Survey), Mn nodules from the Atlantic and Pacific oceans, respectively, provide the best opportunity for such a reference material but their application has been hampered by their incomplete mineralogical characterization and lack of consensus on how to pre-treat (if at all) these type of samples for δ18O analysis. We have performed a detailed mineralogical study using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), powder X-ray diffraction (PXRD), and Raman spectroscopy on these reference materials. In sample NOD-A-1 todorokite, goethite and/or hematite, Mg-calcite, phillipsite or chabazite, quartz and barite were identified. The minerals todorokite, birnessite, asbolane, vernadite, goethite, pyrochroite, quartz, phillipsite or chabazite, anorthite, kaolinite and barite were identified in NOD-P-1. We conducted experiments to assess the effect on δ18O and mineralogy resulting from acidification with hydrochloric acid (HCl), pre-fluorination with bromine pentafluoride (BrF5) at ambient temperature, or both acidification and pre-fluorination treatments. Results from samples given both treatments were deemed most meaningful to the study of Mn crusts and nodules, and therefore nodule research in general, by providing δ18O values representative of the relatively pure oxide-silicate fraction only. We report a δ18O value of 11.0 ± 1.0‰ for the oxide-silicate fraction of NOD-A-1, and a value of 11.1 ± 0.7‰ for the same fraction in NOD-P-1, with results showing a δ18O shift of up to 10.3‰, as a function of nodule and the pre-treatment used. The δ18O values of samples given both treatments converge and are substantially 18O-depleted relative to that of corresponding untreated material, which was found to contain various 18O-enriched phases such as carbonate minerals and non-stoichiometric water. Based on our results, we recommend that for all future analyses of Mn nodules and crusts, the samples receive both treatments to ensure accurate and consistent results.

PALAEOENVIRONMENTAL CONTEXTS FOR MICROBIAL COMMUNITIES FROM Fe-Mn CRUSTS OF MIDDLE-UPPER JURASSIC HARDGROUNDS (BETIC-RIFIAN CORDILLERA)

The Middle-Upper Jurassic transition within the External Subbetic (Betic Cordillera) and the Jbel Moussa Group (Rifian Calcareous Chain) is characterised by numerous stratigraphic breaks recorded as palaeoreliefs, omission surfaces and hardgrounds. One common characteristic is the presence of microbial Fe-Mn crusts and Mn crusts. Three different contexts of microbially mediated Fe-Mn crusts can be distinguished: a) hydrogenetic surficial Fe-Mn crusts and macro-oncoids, b) hydrogenetic cryptic Fe-Mn crusts, and c) hydrothermal surficial Mn crusts. Encrusting foraminifera (Thurammina, Placopsilina, Tolypammina and nubeculariids) and fungi fed on bacteria, while the bacteria and fungi took advantage of the nutrient-rich foraminiferal excretions. The cryptic Fe-Mn crusts are also hydrogenetic crusts developed in the walls of submarine cavities and fractures in the External Subbetic at the time of the hardground development. They are endostromatolites consisting almost exclusively of Frutexites in the case of thin neptunian dykes, or serpulid-Frutexites assemblages in a large neptunian sill. This assemblage reflects the colonization of unfavourable environment (aphotic with low oxygenation) as a response to the photophobic behaviour of chemosynthetic and cryptobiontic microorganisms. Finally, the hydrothermal Mn crusts registered in the Rif are characterised by the record of bacillus-shaped bacteria and different type of filaments. The precipitation of manganese minerals is interpreted as induced by the chemo-organotrophic behaviour of benthic microbial communities, since manganese oxides may form as a result of the direct metabolic activity of bacteria in hydrothermal environments. Very well-preserved fungal hyphae evidence the presence of fungi that probably fed on bacterial communities and their by-products

Microbial community composition in iron deposits and manganese crusts formed in riverine environments around the Aso area in Japan

The Kurokawa river flowing through the Aso Caldera in Southwest Japan is influenced by groundwater containing high concentration of dissolved metals (Fe2+ and Mn2+) and is associated with orange deposits in the upstream and thick black crusts on the wall of artificial waterway tunnel with several km lengths in the midstream regions. X-ray fluorescence analysis revealed that the orange deposits contained up to 34.4% Fe and black crusts comprised up to 25.4% and 10.6% Mn and Fe, respectively. Although naturally occurring Mn-oxides and crusts are considered biogenic in pH-neutral freshwater environments, the whole microbial community in Mn crust and their contribution to Mn crust formation in these environments remain unclear. High-throughput molecular sequencing for bacteria and eukaryotes including fungi revealed black Mn crusts had a high abundance of Sphingomonas, Hyphomicrobium, Bacillus, Pseudomonas, and Mortierella, previously reported genera including several species with Mn-oxidizing activity in Mn crusts or nodules of other marine and freshwater environments. In addition, one bacterial isolate and one fungal isolate with Mn-oxidizing activity were obtained from black Mn crust. These results suggest that multiple Mn-oxidizing bacteria including Pseudomonas and fungi are involved in Mn crust formation on the wall of dark waterway tunnel in the oligotrophic environment of the Kurokawa river.

Extensive Occurrence of Fe–Mn Crusts and Nodules on Seamounts in the Southern Andaman Sea, India

Extensive Occurrence of Fe–Mn Crusts and Nodules on Seamounts in the Southern Andaman Sea, India

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

The Rio Grande Rise (RGR) is a large elevation in the Atlantic Ocean and known to host potential mineral resources of ferromanganese crusts (Fe–Mn), but no investigation into their general characteristics have been made in detail. Here, we investigate the chemical and mineralogical composition, growth rates and ages of initiation, and phosphatization of relatively shallow-water (650–825 m) Fe–Mn crusts dredged from the summit of RGR by using computed tomography, X-ray diffraction, 87Sr/86Sr ratios, U–Th isotopes, and various analytical techniques to determine their chemical composition. Fe–Mn crusts from RGR have two distinct generations. The older one has an estimated age of initiation around 48–55 Ma and was extensively affected by post-depositional processes under suboxic conditions resulting in phosphatization during the Miocene (from 20 to 6.8 Ma). As a result, the older generation shows characteristics of diagenetic Fe–Mn deposits, such as low Fe/Mn ratios (mean 0.52), high Mn, Ni, and Li contents and the presence of a 10 Å phyllomanganate, combined with the highest P content among crusts (up to 7.7 wt %). The younger generation is typical of hydrogenetic crusts formed under oxic conditions, with a mean Fe/Mn ratio of 0.75 and mean Co content of 0.66 wt %, and has the highest mean contents of Bi, Nb, Ni, Te, Rh, Ru, and Pt among crusts formed elsewhere. The regeneration of nutrients from local biological productivity in the water column is the main source of metals to crusts, providing mainly metals that regenerate rapidly in the water column and are made available at relatively shallow water depths (Ni, As, V, and Cd), at the expense of metals of slower regeneration (Si and Cu). Additionally, important contributions of nutrients may derive from various water masses, especially the South Atlantic Mode Water and Antarctic Intermediate Water (AAIW). Bulk Fe–Mn crusts from the summit of RGR plateau are generally depleted in metals considered of greatest economic interest in crusts like Co, REE, Mo, Te, and Zr, but are the most enriched in the critical metals Ni and Li compared to other crusts. Further investigations are warranted on Fe–Mn crusts from deeper-water depths along the RGR plateau and surrounding areas, which would less likely be affected by phosphatization.

Mineral Composition of Manganese Crusts from Belyaevskii Volcano (Sea of Japan)

The polygenic mineral composition of Mn crusts from Belyaevskii Volcano of the Central Basin of the Sea of Japan is determined. The crusts are found for the first time to contain rhodochrosite, manganosite, quenselite, heterolith, manganotantalite, and tungomelane in addition to the previously described todorokite, birnessite, manganite, pyrolusite, and vernadite. Among ore minerals, the breccia crusts include magnetite, titanomagnetite, hematite, pyrite, pyrrhotine, galena, monazite, cerianite, baddeleyite, and pentlandite, while fragments of manganite have silver and numerous particles of copper gold. A significant role in the formation of the mineral composition of the crust was likely played by pore waters involved in the hydrothermal process and organic matter (OM) of the Miocene–Quaternary siliceous–argillaceous strata, which served as the source of many rare and noble metals and affected the redox conditions of mineral formation.