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We have estimated the resource potential of cobalt-rich ferromanganese crusts (CFCs) on the summit area of the KC-8 seamount in the West Pacific, based on the acoustic backscatter intensity (ABI), ROV video footage, and CFC thickness measurements. To estimate the spatial distribution of CFC across 13 equally divided blocks within a 360 km2 area, shipboard and deep-tow ABIs were compared with visual data. The presence of CFCs is evident in the areas where ABI is higher than average, validating the use of ABI data to delineate the exposure of CFCs. With high accuracy in distinguishing between CFCs and sediment-dominant areas, the distribution area of CFCs was precisely calculated. The variation in CFC thickness across the KC-8 seamount summit was measured through CFC samples retrieved using a CFC corer. CFC thickness is highly variable even between adjacent sites, but it shows a roughly increasing trend from south to northwest. Based on the CFC distribution area associated with thickness, we calculated a CFC resource abundance. Of the estimation, 82% have remained on the gentle slope (<10°) areas, which can be accessible for future mining. Overall, our study suggests that the combination of an acoustic survey with reliable thickness information is highly effective in estimating CFC abundance. [ABSTRACT FROM AUTHOR]

Ferromanganese nodules are important marine storehouses for critical metals and windows for changing oceans. Although advanced in situ analytical techniques have been applied to visualize the elemental distribution in the nodule cross‐sections, their spatial distribution remains largely uncertain. This study addresses this gap by employing micro X‐ray fluorescence mapping of parallel nodule cross‐sections to delineate the spatial distributions of critical metals (Mn, Fe, Co, Ti, Ni, and Cu) in three Co‐rich ferromanganese nodules from the northwestern Pacific Ocean. The 10‐layer Os isotopic compositions of one nodule closely align with the well‐documented marine Os isotope evolution of seawater, providing a chronological framework and a maximum age of ∼36 Ma for these nodules. Three concentric chemostratigraphic layers, labeled L1, L2, and L3, were identified from the inside out, based on microscopic structures and the distributions of critical metals. The early growth stage was marked by Mn‐rich, Si‐rich, and high Mn/Fe ratios, suggesting a diagenetic‐driven process attributed to high paleoproductivity conditions because of the low latitude of the study area at that time. The subsequent growth stages are all hydrogenetic in origin to be rich in Fe, Co, and Ti with low Mn/Fe ratios. The apparent detritus present during the second growth stage of the nodules may correspond to the stronger bottom currents in the early Miocene. The final mineralization stage indicates a more stable environment with diminished bottom current activity, leading to the formation of a dense, laminar hydrogenetic layer. Plain Language Summary: The present study bridges the knowledge gap on the spatial distribution of critical metals through the innovative use of micro X‐ray fluorescence mapping on parallel sections of three nodules in the northwestern Pacific Ocean. Os isotope stratigraphy establishes a chronological framework and a maximum age of ∼36 Ma for these nodules. Distinct concentric chemostratigraphic layers, labeled L1, L2, and L3, have been identified in these nodules. The early growth stage of the nodules is characterized by Mn‐rich, Si‐rich and high Mn/Fe ratios, indicative of a diagenetic‐driven process under high paleoproductivity conditions due to the low historical latitude. The subsequent stages are all hydrogenetic in origin to be rich in Fe, Co, and Ti with low Mn/Fe ratios. The apparent detritus present during the second growth stage of the nodules may correspond to the stronger bottom currents in the early Miocene. The final mineralization stage suggested a period of environmental stability with reduced current activity, forming of a hydrogenetic layer enriched in Fe, Co, and Ti. This study not only enhances our understanding of the complex processes that govern the formation and evolution of ferromanganese nodules but also provides deeper insight into the historical shifts within our oceans. Key Points: Ferromanganese nodule was dated via Os isotope stratigraphy and has a maximum age of ∼36 MaMulti‐element integrated maps were produced to assist in obtaining clearer chemostratigraphy images of ferromanganese nodulesSpatial distribution of critical metals and chemostratigraphy in ferromanganese nodules were visualized via multiple parallel cross‐sections [ABSTRACT FROM AUTHOR]

The estimation of the distribution of ferromanganese crusts (FMCs) is determined using the threshold of backscatter intensity of the multibeam echo sounder in ground-truth data; however, this is not accurate. This study developed a method to quantitatively estimate the distribution of FMCs and thickness of the surface sediment (TSS) by determining the relationship between topographic features, backscatter intensity using statistical analyses. Thus, the exposure of FMCs and TSS was quantitatively evaluated with accuracies of 17% and 2.5 m, respectively. This method can efficiently estimate distributions of FMC and TSS of entire seamounts for the benefit of future mineral explorations. [ABSTRACT FROM AUTHOR]

The study of the composition of sedimentary formations raises the problem of identifying extraterrestrial matter, in particular, distinguishing cosmic spherules from technogenic and volcanogenic ones. Based on a study of a collection of 482 bulk spherules separated from ferromanganese crusts of the Pacific Ocean floor, it is proposed to use relief forms on spherule surfaces as an additional feature of their origin. The paper describes in detail such relief forms arising as cosmic particles pass through the upper layers of Earth's atmosphere, and isolation and separation of the Fe–Ni cores from the spherules. The presence of a round hemispherical cavity on the flattened side of the spherule, a depression with concentric circles, or a "button" structure, as the presence of a Fe–Ni core, is sufficient but not necessary evidence for the cosmic origin of a spherule. [ABSTRACT FROM AUTHOR]

Cobalt-rich ferromanganese crusts (CRC) are potential resources for Co, Ni, Pt, and other strategic metals. The CRC thickness varies from a few mm to more than 100 mm at various distance scales over the rock outcrops in the seamounts. However, their variation patterns and controlling factors are not well understood. We conducted a comprehensive small-scale survey, including shipboard acoustic measurements, seafloor observations, and rock drilling over the Xufu Guyot of the Marcus-Wake seamounts in the Northwestern Pacific to characterize the thickness variations on a scale of several kilometers with the topography and geological evolution of the guyot. Rock drilling revealed that thicker CRC (>100 mm) tend to occur on the margins and flat areas on the guyot, while thinner CRC are associated with carbonate reef mounds over the volcanic pinnacles and seamount slopes. The microstratigraphic description indicated that the CRC thickness is strongly related to the geological evolution of the guyot, mainly the stability of the substrate rocks and coverage with calcareous pelagic sedimentation. [ABSTRACT FROM AUTHOR]

The Southern California Borderland hosts a variety of geologic and oceanographic features that allow for diverse habitats to occur in a restricted region with a strong oxygen minimum zone (OMZ) and hard substrates. These include ferromanganese (FeMn) crusts and phosphorites targeted for deep‐seabed mining in other regions. Baseline studies regarding hardground macro‐ (> 0.3 mm) and megafaunal (> 2 cm) invertebrates are lacking, although they contribute to understanding nutrient cycling and resilience of deep‐sea communities to ocean deoxygenation, fishing, or mineral extraction. With the goal of understanding how substrate type, depth, and dissolved oxygen concentration influence invertebrate trophic structure, we surveyed δ13C and δ15N values of invertebrates on hard substrates on the Southern California Borderland margin along a depth gradient (120–2400 m) through the OMZ at inshore (< 100 km from shore) and offshore (100–250 km from shore) sites, using generalized additive models and community‐level metrics. Macrofaunal isotopic values correlate with substrate type, exhibiting higher trophic diversity on FeMn crusts and specialized communities on phosphorites. Megafaunal isotopic values correlate with proximity to shore; animals offshore seem to depend more on phytoplanktonic production than animals inshore. In general, δ15N increased with decreasing dissolved oxygen and increasing depth, possibly due to remineralization processes within the OMZ and with depth. We discuss how feeding modes and community composition might influence the observed patterns. This study elucidates the importance of the environmental context in shaping invertebrate trophic structure on continental margins and provides baseline knowledge that may be useful in regions where these minerals are targeted for extraction. [ABSTRACT FROM AUTHOR]

The methods of decreasing the lining corrosion rate by controlling the temperature mode are analyzed. It is shown that selection of a proper combination of refractory material layers would allow a noticeable decreasing the lining corrosion rate at interaction with liquid metal, but this also would increase heat losses due to convective and radiation heat transfer. A proper algorithm is suggested to reach the optimal solution by optimization of the lining layer thickness and composition. [ABSTRACT FROM AUTHOR]

Manganese is widely used in the iron and steel industry, batteries and other fields. The amount of the manganese oxide ores existing in China coeval with iron and their manganese-to-iron ratio is low. A study was conducted on a synchronous reduction roasting-magnetic separation of a ferromanganese ore with high content of iron taken from South Africa using CO as reductant. Under the conditions of 750°C roasting temperature, 40 min roasting time, 30% CO concentration roasting atmosphere and − 0.074 mm accounting for 82.56% grinding fineness, the iron removal rate was close to 70% through magnetic separation, with the grade and manganese recovery of manganese concentrate reaching 49% and 72.50% and the manganese-to-iron ratio increasing from 2.5 to 5.92. The X-ray diffraction analysis indicated that Mn2O3 and Fe2O3 in the raw ore was reduced to MnO and Fe3O4, respectively, without forming the intermediate product Mn3O4 in a weak reducing atmosphere. The SEM-EDS analysis of the roasted product showed that the simultaneous reduction of manganese and iron oxides could be achieved when the roasting temperature reaches 750°C. The crystal forms of MnO and Fe3O4 were more perfect, and the coexisting grains of Ca, Si and Al clustered further with increasing roasting temperature. [ABSTRACT FROM AUTHOR]

A nondestructive layer-by-layer elemental and phase analysis of the ferromanganese intact crust (aged about 60 million years), extracted from the 1200-m rise of Magellan Mountains of the Pacific Ocean, has been performed using the X-ray fluorescence and X-ray diffraction methods. The crust morphology was studied using scanning electron microscopy. This analysis made it possible to estimate the contributions of various oceanic sources of iron and manganese to the crusting process and propose a mechanism for its formation. [ABSTRACT FROM AUTHOR]

Ferromanganese (FeMn) crusts are Fe and Mn oxides that typically form on deep‐sea elevations by deposition of colloids from seawater. These mineral deposits are considered a source of critical metals and rare earth elements. Besides their potential economic value, FeMn crusts are extremely relevant in ocean science, since their very slow growth rates result in long‐term paleoenvironmental and paleoceanographic records. In this study, we applied geochemical, mineralogical, and magnetic analyses to unravel paleoenvironmental changes at two locations on opposite sides of the Atlantic Ocean, the Rio Grande Rise in the SW Atlantic and the Tropic Seamount in the NE Atlantic. Our results show that the occurrence of amorphous (non‐crystalline) Fe oxyhydroxides and the absence of Fe oxides in hydrogenetic, non‐phosphatized FeMn crusts prevented the development of primary remanent magnetization. In contrast, phosphatized FeMn crusts may have contained a remanent magnetic signal. Phosphatization resulted from increased primary productivity and occurred at different stages during the growth of the FeMn crusts, leading to suboxic conditions and partial dissolution of pre‐existing, remanence‐carrying magnetic minerals. Carbonate Fluorapatite (CFA) accumulation in the phosphatized layers of FeMn crusts replaced Fe and Mn, decreasing their magnetic content. Thus, magnetic variations do not reflect a primary magnetization but rather result from geochemical alterations. The loss of primary magnetization may hamper the use of FeMn deposits for magnetostratigraphic purposes. Key Points: The hydrogenetic FeMn crusts from the Atlantic Ocean contain paramagnetic/superparamagnetic Fe oxyhydroxidesPhosphatization events throughout the formation history of FeMn crusts have altered the primary geochemical and magnetic signalsBiogenic magnetite in FeMn crusts is influenced by the local environment; further research is needed on other influencing factors [ABSTRACT FROM AUTHOR]

The pre-reduction of manganese ore using elemental sulfur under an inert atmosphere at temperatures above 600 °C is required for maximum MnO formation. Under atmospheric conditions, SO2 formation via sulfur oxidation leads to MnSO4, which again will dissociate to lower Mn oxides. Thus, excess energy is required for this conversion, thereby decreasing the overall energy efficiency. The optimum pre-reduction condition obtained is 800 °C, with a holding time of 4 hours at 0.5 S/Mn ratio. [ABSTRACT FROM AUTHOR]

Ferromanganese concretions commonly occur in shallow‐water coastal regions worldwide. In the Baltic Sea, they can record information about past and present underwater environments and could be a potential source for critical raw materials. We report on their microstructural characteristics and magnetic properties and link them to their formation mechanisms and environmental significance. Microstructural investigations from nano‐ and micro‐computed tomography, electron microscopy, and micro‐X‐ray fluorescence elemental mapping reveal diverse growth patterns within concretions of different morphologies. Alternating Fe‐ and Mn‐rich growth bands indicate fluctuating redox conditions during formation. Bullet‐shaped magnetofossils, produced by magnetotactic bacteria, are present, which suggests the influence of bacterial activity on concretion formation. Spheroidal concretions, which occur in deeper and more tranquil environments, have enhanced microbial biomineralization and magnetofossil preservation. Conversely, crusts and discoidal concretions from shallower and more energetic environments contain fewer magnetofossils and have a greater detrital content. Our results provide insights into concretion formation mechanisms and highlight the importance of diagenetic processes, oxygen availability, and bacterial activity in the Baltic Sea. Key Points: Magnetic minerals within shallow water Fe‐Mn concretions can provide valuable environmental information about their formationMagnetic properties are linked to specific growth patterns in Baltic Sea Fe‐Mn concretionsSpheroidal and crust/discoidal concretions are dominated by biogenic and pedogenic magnetic phases, respectively [ABSTRACT FROM AUTHOR]

China's manganese ore import sources are relatively single, with an external dependency exceeding 90%. Despite China is rich in manganese ore resources, they are predominantly characterized by low-grade manganese ores with excessive iron content. The mineral composition is complex, the coexistence is close, the selectivity difference between minerals is small, and separation is difficult. In order to better develop and utilize ferromanganese ore, chemical composition analyses, SEM, MLA, X-ray diffraction analysis and other testing methods were used to conduct process mineralogy research on a overseas ferromanganese ore, and a separation and recovery exploration test was conducted on the ore. The results indicate that the TFe grade is 31.31%, the Mn grade is 9.09%, and the main impurity element Si02 content is 28.73% in the ore. The main valuable minerals in the ore are limonite, coronadite, and psilomelane, with contents of 49.57%, 8.60%, and 6.44% respectively; the main gangue minerals are quartz and barite, with contents of 29.01 and 6.24% respectively. The particle sizes of coronadite and psilomelane in the ore are restively line, with the -38µm particle size distribution reaching 74.59% and 62.54% respectively. Their monomer dissociation degrees are low, only 16.75% and 15.12%. Coronadite and psilomelane mainly exist in intergrowth, with the content of both poor and rich intergrowth above 40%. The two are more closely embedded with limonite. Most of the coronadite particles exist in limonite as tine-grained inclusions. Similarly, most of the psilomelane particles exist in limonite as inclusions or disseminated forms. These make it more challenging to dissociate the iron and manganese mineral monomers. Therefore, it is difficult to achieve effective separation of iron and manganese minerals by traditional mineral processing methods. With the process of "hydrogen-based mineral phase transformatiom magnetic separation", the ore can be treated. And the technical indexes of iron ore concentrate with yield of 54.08%, Fe grade of 58.35%, Fe recovery of 91.47% can be obtained. [ABSTRACT FROM AUTHOR]

The paper considers the current state of Platinum Group Elements (PGEs) geochemistry in the ocean. The behavior of PGEs in the aquatic environment is defined by their oxidation state, the ability to change it, and complexation. The difference in chemical properties leads to PGEs fractionation in the ocean. This is their characteristic feature, along with their ultra-low contents. The paper describes the sources of PGEs supply to the ocean, PGEs behavior in the river–sea mixing zone, and their distribution in seawater. The processes of PGE accumulation in sediments, seafloor sulfides, and ferromanganese deposits of the ocean are reviewed. Possible mechanisms of PGE accumulation on ferromanganese oxyhydroxides are discussed. [ABSTRACT FROM AUTHOR]

The first case of hydrothermal brecciated crusts composed of goethite with quartz veinlets is described for the Sea of Japan. [ABSTRACT FROM AUTHOR]

The methods of decreasing the lining corrosion rate by controlling the temperature regime are analyzed. It is shown that selection of a proper combination of refractory material layers would allow a noticeable decrease of the lining corrosion rate at interaction with liquid metal, but this also would increase heat losses due to convective and radiation heat transfer. A proper algorithm is suggested to reach the optimal solution by optimization of the lining layer thickness and composition. [ABSTRACT FROM AUTHOR]

In this paper, according to the reaction principle and material balance, the coefficient calculation rule is established to construct the valuable element allocation model with Java programs in the hydrometallurgy process of cobalt-rich slag. Thus, the ratio of distribution in each process containing acid leaching, copper deposition, ferromanganese precipitation, and cobalt deposition are forecast quantitatively, accompanied by the recovery rate of the valuable element. Compared with the expanding process of cobalt-rich slag, the correctness and applicability of the model for the distribution and ratio of the valuable element are investigated, and the weak link can be improved according to the specific situation of the process. The recovery rate of cobalt is 95.38 %, and the content of cobalt in the cobalt product is 44.93 % in the cobalt deposition. Ultimately, the valuable element allocation model can quantitatively predict the experimental results, indicating that it can be used for simulating and optimizing the control of the hydrometallurgy process of cobalt-rich slag. This can improve the recovery rate of valuable elements in such hydrometallurgical processes. [ABSTRACT FROM AUTHOR]

The East Siberian Sea (ESS) is one of the least studied seas in terms of ostracod fauna. Ostracods are sensitive organisms to environmental changes, and detailed information on their ecology is still required. To fill this knowledge gap, we studied 33 meiobenthic dredge samples collected from the western part of the ESS and the Chaun Bay together with 17 grab samples taken from the eastern part of the sea. Quantitative analyses of the ostracod assemblages demonstrate that the river-influenced western part of the ESS is inhabited by low diverse and impoverished fauna consisting of the taxa which are able to adapt to different environmental conditions. In the isolated Chaun Bay sheltered from significant riverine influence, the ostracod assemblages contain species that prefer more stable conditions. The predominance of living specimens over dead ones and individual valves points to strong carbonate dissolution that is more pronounced in the western ESS than in the Chaun Bay. The formation of such conditions might be related to the high content of dissolved carbon dioxide resulting from bacterial remineralization of in situ produced and land-derived organic matter in the bottom sediments and low pH near the seabed. Numerous ferromanganese crusts were found on the ostracod valve surfaces and inside the shells from the Chaun Bay. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying some properties and structure of a quasi high-entropy alloy (QHEA) of the CoCrFeMnNi system melted with the use of ferroalloys. The paper presents the results of a study of some properties and structure of a quasi-high-entropy alloy of the CoCrFeMnNi system, smelted using low-carbon ferromanganese and ferrochrome. Chemical composition, strength and microhardness have been studied. The structure contains a small number of inclusions of silicate nature. The experimental alloy demonstrated properties close to the level of properties of a similar alloy melted with the use of pure metals by 5-fold remelting. The results obtained showed the possibility of partial replacement of pure metals with ferroalloys when smelting of QHEAs, which will positively affect their cost. [ABSTRACT FROM AUTHOR]

Although deep‐sea ferromanganese nodules are a potential resource for exploitation, their formation mechanisms remain unclear. Several nodule‐associated prokaryotic species have been identified by amplicon sequencing of 16S rRNA genes and are assumed to contribute to nodule formation. However, the recent development of amplicon sequence variant (ASV)‐level monitoring revealed that closely related prokaryotic populations within an operational taxonomic unit often exhibit distinct ecological properties. Thus, conventional species‐level monitoring might have overlooked nodule‐specific populations when distinct populations of the same species were present in surrounding environments. Herein, we examined the prokaryotic community diversity of nodules and surrounding environments at the Clarion‐Clipperton Zone in Japanese licensed areas by 16S rRNA gene amplicon sequencing with ASV‐level resolution for three cruises from 2017 to 2019. Prokaryotic community composition and diversity were distinct by habitat type: nodule, nodule‐surface mud, sediment, bottom water and water column. Most ASVs (~80%) were habitat‐specific. We identified 178 nodule‐associated ASVs and 41 ASVs associated with nodule‐surface mud via linear discriminant effect size analysis. Moreover, several ASVs, such as members of SAR324 and Woeseia, were highly specific to nodules. These nodule‐specific ASVs are promising targets for future investigation of the nodule formation process. [ABSTRACT FROM AUTHOR]

REY‐rich mud, consisting of deep‐sea sediments with high concentrations of rare‐earth elements and yttrium (REY), holds significant economic potential. Many studies have been conducted on biogenic apatite, ferromanganese micronodule, and phillipsite within these deposits to ascertain the REY enrichment mechanisms. However, the knowledge of clay minerals in REY‐rich mud, which is the predominant component of pelagic sediments, is still limited. In this study, two adjacent gravity cores (core GC02: REY‐rich mud; core GC03: typical sediments of equatorial Pacific) were collected from the Clarion‐Clipperton Fracture Zone (CCFZ) of the Eastern Pacific to study the role of different clay minerals in REY enrichment. The clay minerals in core GC03 and core GC02 are primarily illite (averaging 60%) and smectite (averaging 63%), respectively, and the smectite in core GC02 was mainly Fe‐rich, which was probably formed via the reaction between opal and FeOOH. Moreover, multiple studies have reported similar smectite enrichment in REY‐rich mud, suggesting that it is a common characteristic. The presumed hydrothermal or volcanic origination of smectite in REY‐rich layers of core GC02 indicates the essential role of hydrothermal and volcanic activities in REY‐rich mud formation during the Oligocene in the western CCFZ. Key Points: Smectite is likely to be commonly enriched in rare‐earth elements and yttrium (REY)‐rich mud of the PacificAuthigenic smectite probably originated from hydrothermal or volcanic activity and concentrated moderate amounts of REYThe REY‐rich mud of the western Clarion‐Clipperton Fracture Zone presumably formed through hydrothermal or volcanic activities during the Oligocene [ABSTRACT FROM AUTHOR]

At the Grimlock laterite deposit (Northern Territory, Australia), Co and Ni mineralization occurs mainly in the Mn-oxide rich layers of the ferromanganese (Fe-Mn) crust overlying ultramafic bedrock. Groundwater-associated Fe-Mn crusts consist of mineral (e.g. Mn-oxide, Fe-oxyhydroxide and silicate) groups suitable for studying triple oxygen isotopes and present unique interpretative challenges (e.g. small Mn-oxide fractions relative to Fe-Mn precipitates from other formation environments and extensive weathering). We evaluate triple oxygen isotopes within the context of changes to properties (i.e. mineralogy, major and trace element geochemistry, and degree of weathering) of a lateritic profile. We use pre-existing mineral-water fractionation factors, meteoric water δ 18O and temperature data to calculate δ 18O values of fully altered mineralogical endmembers, then, using mass balance, discuss scenarios to elucidate measured whole-rock δ 18O values. The δ ′18O (′ denotes linearized notation) and Δ ′17O of near-surface samples (0–8 m) are generally lower (mean of 8.892‰) and higher (mean of −0.141‰), respectively, than the δ ′18O (mean of 12.767‰) and Δ ′17O (mean of −0.176‰) of samples from greater depths (19–22 m). At 16–17 m depth, δ ′18O and Δ ′17O are relatively high (means of 17.509 and −0.118‰, respectively). The measured whole-rock δ 18O values are explainable by substituting lower δ ′18O values for the Mn-oxide and Fe-oxyhydroxide fractions, and higher δ ′18O values for the aluminosilicate fraction, changes coinciding with greater alteration. These results suggest that mineral weathering is primarily responsible for observed variations in the triple oxygen isotopes of groundwater-associated Fe-Mn crusts, rather than variation in the initial source of oxygen incorporated into Mn-oxide. Supplementary material: Grimlock sample photographs, XRD patterns and supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.7071907 [ABSTRACT FROM AUTHOR]

A method of producing nitrogen-alloyed steel is considered. The nitrogen alloying technologies based on the use of nitrided ferromanganese and nitrogen purge gas are analyzed and compared to choose the most effective one for the TAGMET conditions. To produce SA 20A steel with a regulated nitrogen content (100–300 ppm), it is proposed to purge metal with nitrogen and argon during treatment in a ladle furnace and during and after degassing. Proprietary software controlling the purging of steel with nitrogen and argon from the control panel of the ladle furnace and the vacuum degassing unit has been developed. This ensured effective control of the nitriding process and achievement of the required nitrogen content in steel. Changing over from alloying with nitrided ferromanganese to purging with nitrogen gas made it possible to eliminate the pyroelectric effect and to reduce the secondary oxidation and contamination of steel with non-metallic inclusions. [ABSTRACT FROM AUTHOR]

This study investigated the possibilities of using low-grade manganese ores in ferromanganese production by smelting process. It is aimed to increase the consumption areas of boron ores. Fluorspar, ulexite, and boroxide were added to manganese ores, and slag fluidity at determined temperatures was examined. Reference samples without flux were used for comparison. The charge materials were melted in graphite crucibles at 1650 °C for 2 hours. The metal/slag phases were separated from each other and their chemical analyses were made. At the end of the experiments, thanks to boron ores, Mn leakage in the slag phase was reduced to a minimum, while 99% Mn was obtained in the metal phase. As a result, it has been determined that the slag fluidity increases more with boron ores (compared to fluorspar), the smelting time decreases, it is possible to use boron ores in ferromanganese production, and their usage areas can be increased. [ABSTRACT FROM AUTHOR]

Ferromanganese (Fe‐Mn) nodules are widely considered significant economic potential and paleoenvironmentally significant archives. Generally, submicron‐thick layers (SMLs) are basic units of the Fe‐Mn nodules and record valuable information about the environment of Fe‐Mn nodule formation, but their structural, mineralogical, and chemical features are not well resolved. Here, we investigated a typical hydrogenetic Fe‐Mn nodule from the Penrhyn Basin in the South Pacific Ocean, using various microanalytical techniques. The nodule mainly consists of a micronodule‐dominant region around the core, a crust near the surface with Mn‐ and Fe‐rich layers, and stromatolite‐like textures between them. These textures are composed of distinct and indistinct SMLs parallel to their growth front. Although the distinct and indistinct SMLs have different mineral phases, the transmission electron microscopy revealed that these layered structures are actually interstratification of SMLs with different crystal sizes of foliated phyllomanganates. Large crystals contain higher Mn oxidation states than small crystals. Such variations of Mn oxidation state with different crystal sizes along the growth direction imply the short‐term regular fluctuation in the redox condition of the Lower Circumpolar Deep Water. Plain Language Summary: Ferromanganese (Fe‐Mn) nodules are the precipitation of Fe and Mn (oxyhydr)oxides, generally occurring as submicron‐thick layers (SMLs). Due to the slow growth rates (millimeters per million years) of Fe‐Mn nodules, these Fe and Mn (oxyhydr)oxides can adequately adsorb various ions from seawater. Besides, as Fe and Mn are highly redox active, their oxides are very sensitive to the redox condition of the environment. Therefore, the physicochemical characteristics of SMLs are the critical key to decipher the metallogenetic environment of the nodules. In this study, we systematically studied the SMLs in a typical hydrogenetic Fe‐Mn nodule collected from the South Pacific Ocean. We discovered that the SMLs are composed of alternating porous and dense layers caused by the crystal size of minerals. The adjacent porous (large crystal size) and dense (small crystal size) layers have the same mineral phases and similar chemical compositions, while the Mn oxidation states are different, revealing the short‐term change of redox conditions of the Lower Circumpolar Deep Water. Our findings not only reveal the characteristics of SMLs, but also provide a new insight into the redox environments of the formation of Fe‐Mn nodules. Key Points: Submicron‐thick layered structures in ferromanganese nodule correspond to the alternation of large and fine phyllomangante crystallitesMn oxidation state in the alternating layers is variable depending on the crystal size of phyllomanaganteThe variation in Mn oxidation state across the layers may reflect short‐term changes in redox environment of the ocean [ABSTRACT FROM AUTHOR]

The structure and chemical composition of ferromanganese crusts formed on the sedimentary cover of the underwater volcanoes of the Peter the Great Seamount and the Vasilkovsky Ridge, located near the continental slope of Primorye (Sea of Japan), are studied. The crusts were formed as a result of cementation and precipitation of manganese hydroxides on the sediment surface. The signs of the hydrothermal nature of these formations are very high titanium and low aluminum modules, low contents of nonferrous and rare-earth elements (REEs), and an excess of heavy REE contents over the light ones. An ore substance was probably deposited in the Pleistocene–Holocene from postvolcanic hydrothermal solutions. Unlike the crusts deposited on basalts in the central parts of the Sea of Japan, these crusts do not contain inclusions of fine grains of medium- and high-temperature mineral phases of nonferrous metals. [ABSTRACT FROM AUTHOR]

Ferromanganese crusts found in the Bering Sea on the Volcanology Massif, Alpha Fault Zone, and Shirshov Submarine Ridge that cover the surface of rocky volcanic structures are most likely the product of postvolcanic activity. The results indicate that the studied ferromanganese formations developed under the influence of two factors: slow precipitation of metals from ordinary seawater and metal-enriched hydrothermal solutions. In microstructural and mineralogical terms, the composition of Fe–Mn crusts of the Bering Sea proved rather monotonous. The ore part is represented mainly by ferruginous vernadite and, rarely, hematite in combination with amorphous silica, and 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 of the upper horizons in the ocean water column. At the same time, the europium anomaly is close to neutral, so in seven samples, its value is 0.96–1.03 (average 1.0) and only in three samples is it slightly elevated (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. [ABSTRACT FROM AUTHOR]

For the first time, data on the mercury content and its forms in the ferromanganese and ferruginous formations of the Chaun Bay (East Siberian Sea) were obtained. According to the geochemical classification, the studied formations belong to diagenetic. The mercury content ranges from 8 to 26 µg/kg, which is two to five times lower than the bulk content in the Upper continental crust. The isomorphic (mineral) form of mercury is predominant in ferromanganese and ferruginous formations. [ABSTRACT FROM AUTHOR]

The geochemistry and mineralogy of Mn nodules offer crucial insights into the origins, environmental changes, and distribution of abyssal resources. However, the conventional laboratory X-ray diffractometer, usually employed for semi-quantitative analysis of mineral composition in Mn nodules, often fails to sufficiently detect minor phases due to beam flux limitations and high background signals. In this study, we investigated differences in manganate composition, even when comprising around 1% of the phase fraction, in two manganese nodules (KC-8 and KODOS-10) using high-resolution synchrotron X-ray diffraction. The Mn/Fe ratios of KC-8 and KODOS-10 were 1.32 and 6.24, respectively, indicating that KC-8 and KODOS-10 were predominantly formed in hydrogenetic and diagenetic environments. Both samples contained quartz, vernadite, buserite, and feldspar. Todorokite and illite were exclusively observed in KODOS-10. In KC-8, the phase fractions of vernadite and buserite among manganates ranged from 94(5)%–100(4)% and 6(1)%–0%, respectively. However, in KODOS-10, the fractions of vernadite, buserite, and todorokite ranged from 47(1)%–56(2)%, 33.6(4)%–40.1(3)%, and 10(3)%–16.3(8)%, respectively. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the sorption properties of ferromanganese crusts on the Kocebu Guyot relative to rare-earth metal (REM) cations are presented. It is established that the crusts are a natural, highly selective sorbent of REM cations. The REM cations are adsorbed on ore minerals (Fe-vernadite, vernadite, Mn-feroxyhyte, and goethite). The crusts are characterized by a high exchange capacity (1.67‒3.28 mg-equiv/g), which increases in the series: Lu < Gd < Dy < La, Sm < Nd < Y < Eu Ce. The REM cations are adsorbed by the ion-exchange equivalent mechanism—in the case of Ce3+ cations, according to the superequivalent mechanism with respect to cations of the exchange complex of ore minerals—Na+, K+, Ca2+, Mg2+, Mn2+, and Ni2+, which contribute 95–98% to the total capacity of minerals. [ABSTRACT FROM AUTHOR]

Based on the Multibeam backscatter data, Sub-bottom profiling and Remotely Operated Vehicle (ROV) dives, an attempt has been made to understand the spatial distribution of ferromanganese crusts and nodules on the West Sewell Ridge (WSR), Andaman Sea. Slope analysis of the multibeam data and echo type characters from sub-bottom profiles were used to identify favorable areas for crust and nodule occurrence and these areas were selected for detailed seafloor feature analysis using ROV videography. Further, histogram analysis of backscatter intensity revealed five boundary values and integrated these threshold values with ground truth observation from ROV videos identified crust dominated, crust and nodule dominated, the hard substrate with thin sediment cover, the hard substrate with thick sediment cover, and complete sediment covered seabed. The seafloor variation map prepared from the different geological classes identified shows that crust-dominated seabed is distributed in the eastern summit region while crust and nodule-dominated seabed in the western summit region of WSR. Further, the flanks of the WSR are covered with turbidity sediments and sediments derived from the slope failure and possess the least possibility of the occurrence of crusts and nodules on the flanks. [ABSTRACT FROM AUTHOR]

Here we report the mechanism of adsorption and immobilization of heavy metal ions during the formation of deep-sea microbial-mediated Mn-Fe oxidation synergistic synthesis products under Mn concentration of 1 g/L, pH = 6, temperature of 25°C, adsorption time of 12 days, salinity of 3% and OMF inoculation of 20%. The adsorption amounts of heavy metal ion (Cu2+, Ni2+, and Co2+) by the deep-sea microbial-mediated Mn-Fe oxidation co-synthesis products were 11.81 mg/g, 9.52 mg/g, and 7.14 mg/g, respectively. The process was consistent with the Langmuir isothermal adsorption model and quasi-secondary kinetic model, indicating that the adsorption of heavy metal ion during the formation of the deep-sea microbial-mediated Mn-Fe oxidation co-synthesis products was controlled by chemisorption. FTIR and XPS results showed that the adsorption and fixation of heavy metal ions in the system mainly depended on the physical adsorption, ion exchange, functional group complexation, precipitation and electrostatic attraction effects of the functional groups on the surface of the manganese and iron oxidation products and oxidized low-valent manganese colonies. The introduction of iron ions improved the negative charge, specific surface area, active sites and surface activity of the adsorbent surface, which enhanced the adsorption of heavy metal ion by the oxidized low-valent manganese functional microbial-mediated manganese oxidation synergistic synthesis products. Meanwhile, this study provides a new theoretical basis for the pollution treatment of Cu2+, Ni2+, Co2+, Fe2+, and Mn2+ in heavy metal polluted water bodies and deep-sea manganese nodule mining processes with local exceedances. [ABSTRACT FROM AUTHOR]

The results of experiments on manganese pellets based on beneficiated manganese-containing sludge and the melting of ferromanganese alloy with their use are presented. Via beneficiating manganese-containing sludge (16.32% Mn), a concentrate with a manganese content of 35.2% was obtained. The composition of the charge used to prepare manganese pellets is proposed, and the conditions affecting their strength are determined. It was established that manganese is present in the composition of calcined pellets in the form of jacobsite MnFe2O4 and hausmannite Mn3O4. The formation of a phase of ferrobustamite (Ca0.79Fe0.21)SiO3, a ferrosilico-calcium binder that helps increase the strength of pellets, was found. Ferromanganese alloy was obtained as a result of the melting of calcined manganese pellets in a high-temperature Tamman-type unit. The Fe-Mn-Si alloy corresponds to the DIN 17 564 as-grade FeMn70Si in terms of manganese (63.76%) and silicon (17.21%) contents. The content of limiting impurity elements—carbon and phosphorus—in ferromanganese alloy is within acceptable limits. The structure of Fe-Mn-Si alloy and slag formed during their smelting process were studied. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the temperature effect on the formation of a complex alloy–mangano ferro silico chromium—from dusts formed at ferromanganese and ferrochromium production in the presence of iron shavings and high-ash coal. The study included the thermodynamic modeling of the process using the HSC-6.0 software package, based on the minimum Gibbs energy principle. In the thermodynamic modeling, the following raw materials were used: ferromanganese production dust of the following composition, %: MnO 53.3; SiO2 24.0; Fe2O3 1.5; MgO 3.50; ZnO 1.8; PbO 0.6; ferrochromium production dust of the composition, %: 3.7 Al2O3, 3.0 CaO, 25.0 Cr2O3, 8.0 FeO, 17.0 MgO, 10.0 SiO2, 4.0 C; high-ash coal containing, %: C 33.0; volatile compounds 20.0; ash 46.14 (including 23.07% of SiO2, 7.0% of Al2O3, 11.5% of Fe2O3, 2.8% of CaO, 1.8% of MgO). It was found that manganese from the dusts' mixture is completely reduced and passes into the alloy at 500 °C; chromium, regardless of the amount of coal, passes from the dust into the alloy at 1300 °C; 88.43% of silicon passes into the alloy at 1900 °C and 48% of coal. The manganese, chromium and silicon concentrations in the alloy are 19.74–27.46%, 20.45–27,20%, 8.02–26.43%, respectively. Increasing the amount of coal from 32 to 48% at a constant temperature (or increasing the temperature of a constant amount of coal) increases the silicon concentration in the alloy and reduces the chromium and manganese content. The monoalloy for producing 30HGSA steel can be obtained in the temperature range of 1793–1900 °C and coal amount of 35.5–40%; for 25HGSA steel—in the temperature interval of 1773–1900 °C and coal amount of 34.4–40%; for 35HGSA steel—in the temperature range of 1723–1850 °C and 32–40% of coal. [ABSTRACT FROM AUTHOR]

The Hawaiian Chain-Emperor Seamounts is known to be one of the most active regions influenced by mantle hotspot. However, previous studies have provided limited information on the growth process and metal enrichment of marine ferromanganese crusts as indicators of post-eruption history. In this study, we conducted a geochronological and major elemental study of a hydrogenetic ferromanganese crust, from the Detroit Seamount using high-resolution magnetic and geochemical scanning. Our findings are as follows: (1) A total of 39 magnetozones are recognized in the studied section of the crust, which can be preliminarily correlated to the geomagnetic polarity timescale from chrons C1n to C5Dn. This correlation yields growth rates of 1.48–2.18 mm/Myr over the past ∼18 Myr. (2) Columnar and lamellar growth structures are identified with distinct metal enrichment patterns. A significant transition from lamellar to columnar growth occurred at ∼11.6 Ma. (3) The quantified elements can be clustered into three groups, (Mn, Cu–Co–Ni, and Al–Si), (Fe and Ti), and Ca. A strong correlation between metal enrichment in the crust and the global benthic foraminifera δ13C record is then observed. Based on these results, we suggest a predominant role of deep-sea redox conditions in the growth history of ferromanganese deposits on the Detroit Seamount since the Early Miocene. [ABSTRACT FROM AUTHOR]

A new X-ray fluorescence technique is proposed as an alternative to the labor-consuming volumetric method for the estimation of manganese valence state in ferromanganese nodules. The approach is based on the measurement of the relative intensities of some X-ray fluorescence spectrum characteristic spectral lines and satellites (MnKβ5 and MnKβ′) preconditioned by electron transfer from the valence shell. Calibration curves were created using manganese oxide samples (MnO, Mn2O3, MnO2) and 12 certified reference materials of ferromanganese nodules, cobalt-bearing ferromanganese crusts, and manganese ores with certified (or determined by approved methods) total and tetravalent manganese content. The presence of high iron content was taken into account. A set of oceanic ferromanganese nodules samples collected in the Magellan Seamounts (Pacific Ocean) were analyzed. Differences between the results of the X-ray fluorescence method and volumetric techniques for tetravalent manganese content were 4.9 rel.%, which is comparable with the accuracy of the volumetric technique (3.6 rel.%). [ABSTRACT FROM AUTHOR]

The manganese silicate and calcium ferrite commonly generated during the treatment process of manganese ore results in difficult separation of manganese and iron. In this study, the migration behaviors of ferromanganese spinel and gangue compounds in a microwave field were explored by examining the corresponding phase and microstructural evolutions. Different from the traditional process, the interface reactions depend on the diffusion of Mn2+ and Fe2+ towards the surface of the gangue particles, owing to the microwave absorption ability of ferrite being better than that of calcium oxide. Compared with manganese, iron more easily combined with silicon oxide to form silicates. CaO induced the lattice transformation of the ferromanganese spinel to calcium manganese ferrite. The migration rate of manganese was faster than that of iron in the microwave field. The appropriate mass ratio (m(CaO)/m(SiO2)) reduced the negative impact of gangue components on the reduction process of ferromanganese. [ABSTRACT FROM AUTHOR]

A study of the isotopic compositions of neodymium and strontium in four mineral fractions of the hydrogenous ferromanganese crusts of the northernmost Pacific has been carried out for the first time. The relationship of the 87Sr/86Sr ratio and εNd value of the residual fraction in heterochronous layers of the ferromanganese crusts have shown that the sources of detrital matter are from rock weathering by the Yukon River, the Kuskokwim River, the Anadyr River and the rivers of Kamchatka. The amount of aluminosilicate impurity does not affect the isotopic compositions of the chemogenic (loosely bound, Mn oxides or manganese, hydrous Fe oxides or ferrous) fractions. The decreased εNd value in the ferrous fraction seems to be related to the presence of rare earth element (REE) phosphate complexes in seawater. The increase in those complexes is a consequence of melt waters entering the ocean during warming periods. Our data indicate that the carbonate REE complexes are not the dominant form of the REEs in the northernmost Pacific, which leads to the fact that the neodymium isotopic compositions of the manganese and ferrous fractions of hydrogenous ferromanganese crusts are different. A decrease in εNd value in the ferrous fraction may be a marker of a local increase in the surface water bioproductivity. Our data also show that the increase of the REE in the ferrous fraction relative to the manganese fraction does not reflect the participation of hydrothermal matter in the formation of mixed hydrogenous–hydrothermal crusts but is a consequence of an increase in the REE phosphate complexes. [ABSTRACT FROM AUTHOR]

To remove the serious contamination caused by tetracycline hydrochloride, this paper uses the method of impregnation followed by pyrolysis to prepare ferromanganese-loaded sludge-based biochar and investigate its effectiveness in removing tetracycline hydrochloride. The material was characterized by field emission SEM, FTIR, and X-ray diffraction analysis. The possible reaction mechanisms involved in the removal of tetracycline were deduced based on the determination of Mn2+ during the reaction process and XPS characterization of materials before and after the reaction, and analysis of degradation intermediates and reaction pathways during tetracycline hydrochloride degradation was discussed. The results showed that the highest removal rate of 90.71% was achieved at a Fe-to-Mn ratio of 2:1 for the Fe-to-Mn-loaded sludge-based biochar. XPS characterization before and after the reaction showed that the valence state of Fe did not change significantly and was stable, while Mn4+ partially changed to Mn2+ and a redox reaction occurred. The changes in Mn2+ concentration during the reaction showed that the degradation of tetracycline hydrochloride was mainly dominated by MnO2. The LC–MS analysis revealed eight intermediates in the degradation of tetracycline, and two possible reaction pathways existed. [ABSTRACT FROM AUTHOR]

Sighter Induced Roll Magnetic Separation tests were conducted on a ferromanganese ore sample to determine the potential to significantly upgrade the Mn content and Mn:Fe ratio. The sample had a Mn:Fe ratio of 1.3 and was comprised of hematite, cryptomelane, pyrolusite, quartz, goethite and braunite. Tests at 4.7, 2.3 and 1 mm top sizes revealed better separation of Fe from Mn at the 2.3 and 1 mm top sizes. This reflected the better liberation and separation characteristics of Fe oxides at 2.3 mm and both Fe and Mn oxides at 1 mm. A test on the −2.3 + 0.6 mm size fraction improved the Mn:Fe ratio to 4.6, the Mn content to 41.5 wt% with 69.4% mass recovery and 84.2% Mn recovery. Particle magnetic susceptibility was influenced by particle microporosity, and its effect on apparent density, resulting in some Mn oxides reporting to the magnetic concentrate and Fe oxides to the tails. [ABSTRACT FROM AUTHOR]

Ferromanganese nodules are a potential energy resource because of their high contents of economically interesting elements (i.e. Mn, Ni, Cu, and Zn). These are higher in diagenetic layers than in hydrogenetic layers. The study of the causes of elemental accumulation in the diagenetic layer is useful for the exploration metal-rich nodules. A diagenetic-dominant ferromanganese nodule, from the central Clarion–Clipperton Fracture Zone of the eastern Pacific Ocean was studied from core to rim. It was divided into four layers and seven sublayers, of the four typical diagenetic sublayers (L1, L2-1, L2-2, and L3-1). Differences were observed in these diagenetic sublayers. L1 presents the highest Mn/Fe ratio (54), the lowest Co content (2262 ppm), and a positive Ce anomaly. L2-1 exhibits high Co (3122 ppm) and Ba contents (4020 ppm), a positive Ce anomaly, and an obvious peak for 10 Å manganate minerals. L2-2 contains the lowest Ni+Cu contents (3.2 wt%), the highest Ba and Co contents (5110 ppm), and the strongest positive Ce anomaly. In L2-2, the δCe value can be positively correlated to the Mn/Fe ratio and a pronounced peak for 10 Å manganate minerals indicates that this layer has the highest mineral crystallinity. L3-1 shows the highest Ni+Cu contents (5.4 wt%), the lowest Ba (1247ppm), and Co (1725 ppm), a weakly positive Ce anomaly, and the poorest mineral crystallization. Diagenetic- and hydrogenetic-endmember mixing models reveal that hydrogenetic input contributes minimally to these chemical changes, whereas diagenetic input contributes greatly. The changes in diagenetic input may be caused by the changes in primary productivity brought about by movement of tectonic plates and the intense activity of the diagenetic pore fluid. The activity may provide a metal source for the diagenetic sublayer (anomalously high Co and Ce content) via the incorporation of metals released from dissolved buried nodules and micronodules under a suboxic or reducing environments. [ABSTRACT FROM AUTHOR]

Background: Ferromanganese nodule-bearing deep-sea sediments cover vast areas of the ocean floor, representing a distinctive habitat in the abyss. These sediments harbor unique conditions characterized by high iron concentration and low degradable nutrient levels, which pose challenges to the survival and growth of most microorganisms. While the microbial diversity in ferromanganese nodule-associated sediments has been surveyed several times, little is known about the functional capacities of the communities adapted to these unique habitats. Results: Seven sediment samples collected adjacent to ferromanganese nodules from the Clarion–Clipperton Fracture Zone (CCFZ) in the eastern Pacific Ocean were subjected to metagenomic analysis. As a result, 179 high-quality metagenome-assembled genomes (MAGs) were reconstructed and assigned to 21 bacterial phyla and 1 archaeal phylum, with 88.8% of the MAGs remaining unclassified at the species level. The main mechanisms of resistance to heavy metals for microorganisms in sediments included oxidation (Mn), reduction (Cr and Hg), efflux (Pb), synergy of reduction and efflux (As), and synergy of oxidation and efflux (Cu). Iron, which had the highest content among all metallic elements, may occur mainly as Fe(III) that potentially functioned as an electron acceptor. We found that microorganisms with a diverse array of CAZymes did not exhibit higher community abundance. Instead, microorganisms mainly obtained energy from oxidation of metal (e.g., Mn(II)) and sulfur compounds using oxygen or nitrate as an electron acceptor. Chemolithoautotrophic organisms (Thaumarchaeota and Nitrospirota phyla) were found to be potential manganese oxidizers. The functional profile analysis of the dominant microorganisms further indicated that utilization of inorganic nutrients by redox reactions (rather than organic nutrient metabolism) is a major adaptive strategy used by microorganisms to support their survival in the ferromanganese nodule sediments. Conclusions: This study provides a comprehensive metagenomic analysis of microbes inhabiting metal-rich ferromanganese nodule sediments. Our results reveal extensive redundancy across taxa for pathways of metal resistance and transformation, the highly diverse mechanisms used by microbes to obtain nutrition, and their participation in various element cycles in these unique environments. 7UX-FAbsHcrvGN6PxGni8J Video Abstract [ABSTRACT FROM AUTHOR]

Manganese sludge, an industrial waste product in the ferroalloy industry, contains various components and holds significant importance for sustainable development through its valorization. This study focuses on characterizing a manganese sludge and investigating its behavior during sulfuric acid leaching. The influence of process conditions, including temperature, acid concentration, liquid to solid ratio, and leaching duration, was examined. The results revealed that Mn, Zn, and K are the main leachable components, and their overall leaching rates increase with increasing temperature, liquid to solid ratio, and time. However, the acid concentration requires optimization. High leaching rates of 90% for Mn, 90% for Zn, and 100% for K were achieved. Moreover, it was found that Pb in the sludge is converted to sulfate during the leaching, which yields a sulfate concentrate rich in PbSO4. The leaching process for Mn and Zn species appears to follow a second or third order reaction, and the calculation of rate constants indicated that Mn leaching kinetics are two to five times higher than those for Zn. Thermodynamic calculations were employed to evaluate the main chemical reactions occurring during leaching. [ABSTRACT FROM AUTHOR]

The transformation of oxide inclusions in flash-butt welding (FBW) of K76F rails was studied with the use of the Auger-microprobe JAMP 9500f of JEOL company (Japan) with the X-ray energy dispersion spectrometer Inca penta fet x3 mounted on it and involvement of the most informative methodologies of fractographic analysis. It is shown that high-temperature oxide inclusions without changing the aggregate state are removed as a flash. On the basis of silicon oxides on a molten surface in the welding process, easy fusible ferromanganese and in the near-contact layer -- manganese silicates are formed. The heterogeneity of silicon distribution is the cause of formation of clusters of silicates and formation of "matt spots" in the near-contact layer. [ABSTRACT FROM AUTHOR]

Selenium (Se) is essential to human health, anti-cancer, possessing antioxidant, and antiviral properties. In this study, the spatial patterns of rice Se and their varying relationship with soil Se on a regional scale were studied using hot spot analysis for the agricultural soils in Guangxi. According to the hot and cold spot maps, rice Se correlates positively with soil Se in Guangxi agricultural soils. High rice Se accompanies high soil Se in the central part of Guangxi (e.g., Liuzhou, Laibin), and low rice Se is in line with low soil Se in the western part (e.g., Baise). However, the hot spot analysis maps indicate that southwestern Guangxi exhibits a special characteristic of low rice Se with high soil Se (e.g., Chongzuo). This special pattern is strongly associated with the high concentrations of Fe2O3 (ferromanganese nodules) in the carbonate rock area. The hot spot analysis proves useful in revealing the spatial patterns of rice Se in Guangxi and identifying the hidden patterns. [ABSTRACT FROM AUTHOR]