Minerals Mn Research Articles

Mineralogy and Geochemistry of the Upper Cretaceous Mudrocks, Wadi Feiran Region, West-Central Sinai, Egypt

The present paper aims to explore the mineralogy and geochemistry of the mud rocks that have been accumulated during the Late Cretaceous in Wadi Feiran, West-Central Sinai, Egypt. The investigated section comprises three distinct lithostratigraphic units, namely the Raha, Wata, and Matulla Formations. Mineralogical examination proposes the existence of several sorts of clay minerals (e.g., kaolinite, illite, muscovite, and montmorillonite). The recognition of these clay minerals proves deposition in alkaline environmental conditions. Besides, our findings suggest that the reported clay minerals probably originated first in the form of chlorite instead of illite, as illite is likely produced from the weathering of chlorite. The overflow dispersion of both main (Al2O3, SiO2, Fe2O3, CaO, MgO, K2O, Na2O, P2O5, Cl, and SO3) and minor (Ti, Mn, Cu, Ni, and Sr) constituents was assessed through applying chemical and physicochemical factors on the studied mudrocks. Our study concludes that reducing alkaline conditions were the limiting environmental factor in the deposition of these Upper Cretaceous rocks.

Distribution of Minor and Major Metallic Elements in Residential Indoor Dust: A Case Study in Latvia.

The coronavirus disease 2019 (COVID-19) pandemic has not only brought considerable and permanent changes to economies and healthcare systems, but it has also greatly changed the habits of almost the entire society. During the lockdowns, people were forced to stay in their dwellings, which served as a catalyst for the initiation of a survey on the estimation of the metallic element content in residential indoor dust in different parts of Latvia. This article presents the study results obtained through the analysis of collected dust samples from 46 dwellings, both in the capital of Latvia, Riga, and in smaller cities. Two methods were employed for indoor dust collection: vacuum sampling and manual sampling with a brush and plastic spatula. After microwave-assisted acid extraction, the samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) in terms of the major (Na, K, Ca, Mg, Al and Fe) and minor (Mn, Ni, Co, Pb, Cr, As, Ba, Li, Be, B, V, Cu, Zn, Se, Rb, Sr, Cd, La, Ce and Bi) elements. For the data analysis, principal component analysis was performed. Among the measured metals, the highest values were determined for the macro and most abundant elements (Na > K > Ca > Fe > Mg > Al). The concentration ranges of the persistently detected elements were as follows: Pb, 0.27-1200 mg kg-1; Cd, 0.01-6.37 mg kg-1; Ni, 0.07-513 mg kg-1; As, 0.01-69.2 mg kg-1; Cu, 5.71-1900 mg kg-1; Zn, 53.6-21,100 mg kg-1; and Cr, 4.93-412 mg kg-1. The critical limit values of metallic elements in soil defined by the legislation of the Republic of Latvia (indicating the level at or above which the functional characteristics of soil are disrupted, or pollution poses a direct threat to human health or the environment) were exceeded in the following numbers of dwellings: Pb = 4, Ni = 2, As = 1, Cu = 16, Cr = 1 and Zn = 28.

Cable bacteria regulate sedimentary phosphorus release in freshwater sediments

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

Occurrence, Source, and Mobilization of Iron, Manganese, and Arsenic Pollution in Shallow Aquifer

This investigation is aimed at exploring the mobilization and sources of Fe, Mn, and As in aquifers through geochemical characterization, spatial analysis, and statistical approaches. Analytical results showed that the average concentrations of Fe (10.17 mg/L) and Mn (3.6 mg/L) crossed the guideline value but not As in all samples. In this study, the elevated levels of dissolved organic carbon, salinity, total hardness, and log10 pCO2; the lower value of dissolved oxygen; and some oxidizing groups of samples influence the reductive environment of Fe and Mn weathering. The investigation illustrated that the source of both metals on the upper platform is consolidated silty soil and aquifer sediment, whereas, in the river valley, they originate from Fe and Mn-bearing nodules in the rich clay layer and tidal mud. In addition, the frequent fluctuation of river flow, excess water mining, and an unbalanced recharge/discharge ratio are the causes of higher concentrations of both metals. The correlation matrix and factor analysis of Fe and Mn with redox-sensitive water variables confirmed that a favourable reductive situation fosters the Fe and Mn release process. Studies have also shown the significant possibility of forming a metal complex with organic and inorganic substances. The higher dissolution of Fe and Mn minerals causes As to be adsorbed on them, leading to less release of As into groundwater. This investigation provides a basis for the rational use of groundwater and the defense of public health in zones with high Fe and Mn contents.

Quantification of alloying elements in steel targets: The LIBS 2022 regression contest

We present the results of the regression contest organized for the LIBS 2022 conference. While the motivation and design of the contest are briefly presented, the work focuses on the methodologies of the three best-performing teams. The employed spectral preprocessing strategies, choice of regression models and its optimization are detailed for each team separately. The aim of the contest reflects the long-term challenges faced by quantitative laser-induced breakdown spectroscopy (LIBS) analysis. Thus, the contest was designed with the purpose of providing a transparent platform for comparing and evaluating the large range of data processing tools available in the LIBS literature. Namely, the contest consisted of the quantification of two major (Cr, Ni) and two minor (Mn, Mo) elements in 15 steel targets. For constructing an appropriate regression model, spectra of 42 targets were provided. The spectra were collected using a commercially available laboratory-based LIBS system and made publicly available. The contest lasted 53 days during which the teams did not receive feedback. In total, 21 teams participated out of which the three best-performing methodologies are presented here. A single linear partial least squares model and two artificial neural network regression models are presented. The corresponding feature selection strategies included emission line selection, spectral range selection, and automatized wavelength selection. Various spectral normalization strategies and data augmentation strategies are also presented.

Mineralogy and geochemistry of ferromanganese nodules in semiarid calcareous soils from Northeastern Brazil

Fe/Mn nodules are important records of pedogenesis, weathering processes, and pedoenvironmental conditions. However, data regarding the morphology and mineralogy of Fe/Mn nodules are limited due to difficulties concerning the identification of their low crystallinity Fe/Mn oxides. The hypothesis is that nodules in calcareous soils in Northeastern Brazil present crystalline forms of Mn oxides, whose mineralogy and chemical composition are linked to slight variations in relief. This study investigated the mineralogy and geochemistry of Fe/Mn nodules of soils on different relief surfaces (convex, flat, and concave). The nodules were analyzed using sequential selective dissolution procedure (SSDP), X-ray diffraction, elemental analyses, micromorphology scanning electron microscopy, and energy dispersive spectroscopy. Improvements of the SSDP were needed to identify Mn oxide minerals (birnessite and lithiophorite) in nodules. The relief features are determinants for the distribution and formation of minerals in nodules. The occurrence of calcite silt-sized on the convex and straight surfaces indicates pedogenetic genesis. An increase in kaolinite, highly crystalline lithiophorite, and the absence of calcite in the nodules close to the concave surface also indicates synchronism with pedogenesis. Pseudo-hexagonal lithiophorite and birnessite with plate-like habits are important scavengers of Ce, Co, V, and Ba. This research represents the first record of the detailed morphology and identification of Mn minerals in Fe/Mn nodules using SSDP in semiarid calcareous soils from Northeastern Brazil.

Anaerobic consortia mediate Mn(IV)-dependent anaerobic oxidation of methane

Manganese-dependent anaerobic oxidation of methane (Mn-AOM) is a major methane sink and vital to mitigating global warming. However, it is difficult for microorganisms to mediate electron transfer between the hardly dissolved CH4 and insoluble Mn(IV) minerals, leading to poor understanding of species mediating Mn-AOM. This study successfully enriched an anaerobic consortium mediating AOM driven by Mn-dependent respiratory growth, and for the first time, revealing a syntrophic pathway for Mn-AOM. The Mn-AOM occurrence was confirmed by long-term bioreactor performance and 13C-labelling batch experiment. Metagenomic and metatranscriptomic analyses demonstrated that the Candidatus Methanoperedens sp. BLZ1 was responsible for CH4 oxidation. The Luteitalea pratensis mediated extracellular electron transfer crossing S-layer of Ca. M. BLZ1 by conductive pili, and mediated microbial Mn(IV) reduction via multi-heme c-type cytochromes. This study offers an alternative syntrophic pathway for Mn-AOM by a microbial consortium instead of previously reported pathway by ANME alone. These outcomes provided new insight into migrating global climate change and manganese cycles.

Structural and spectroscopic study of the kieserite-type (Mg,Mn)SO4·H2O solid solution at ambient and low temperatures relevant to Mars and the icy moons of Jupiter and Saturn

The presence and importance of sulfates in our solar system have become common knowledge among the dedicated scientific community, as well as their crucial role in governing the water budget of planets such as Mars. The formation of subsurface oceans and cryovolcanism on icy moons of Jupiter and Saturn owe their existence to melting equilibria influenced by sulfate hydrates in the deeper parts of these celestial bodies. In such a setting, it cannot be ruled out that lower-hydrated sulfates including kieserite, MgSO4·H2O, are also present, given their stability under geologic pressures relevant even down to the lower mantle of the icy satellites. With regard to the composition of the water-soluble fraction in C1 and C2 chondritic meteorites presumed to correspond to that of the rocky cores of the Jovian moons, local kieserite may contain significant amounts of Mn in addition to Ni (and also some Fe). Minor Mn contents are probable even in kieserite occurring on the surface of Mars. Substantial lattice parameter changes and spectral band shifts between kieserite and its isostructural Mn-analogue szmikite, MnSO4·H2O, are well known, nevertheless neither the existence of a potential MgMn solid solution series nor its crystal chemical and spectroscopic behavior has yet been investigated.This work provides the first evidence for such a continuous solid solution, describes its structural properties, and gives a detailed insight into the position changes of prominent bands in FTIR- and Raman spectra of synthetic samples, as the Mn/Mg ratio increases, with the measurement having been performed both at ambient and low temperatures relevant for Mars and the icy satellites. It reveals that contents of Mn do not cause any significant shift in the H2O stretching vibrational bands, yet influence the position of sulfate-related vibrations much in the same way as the incorporation of other relevant transition metal cations, such as Ni. The contrasting behavior of the ν3 and ν1 stretching vibrations of the H2O molecule in case of Mn- (no shift) and Ni-incorporation (significant shift to lower wavenumber) along with their comparable influence on the position of sulfate bands allow to deduce the chemical composition of kieserite in a ternary Mg–Mn–Ni system based on spectroscopic remote sensing or in situ data from celestial bodies. The assessment of chemical composition from vibrational spectra is facilitated by the observed Vegard-type behavior, where lattice parameters as well as the spectral band positions change along linear trends with increasing substitution of Mg, regardless if by Mn, Fe, or Ni. The observed shift of mainly the H2O stretching vibrations to lower wavenumber values as temperature decreases (in contrast to the bands related to the sulfate group) match thermal behavior observed in other binary solid solutions of sulfate monohydrate phases isostructural with kieserite.

Chronology and critical metals enrichment mechanism of ferromanganese nodules from the Parece Vela Basin, Philippine Sea

Ferromanganese nodules are potential economic metal resources enriched with Mn, Co, Ni, Cu, Ti, and rare earth elements plus yttrium (REY). The mineralogy, magnetic scanning, and geochemistry of ferromanganese nodules from the Parece Vela Basin in the Philippine Sea were documented to verify critical metals variations during nodule growth. Based on in situ magnetic scanning, the nodules from the basin were found to initially form during the late Pliocene. At ∼1.6 Myr, the growth structure of the nodules changed remarkably from lamellar to columnar. The inner part has a dense lamellar structure with unstable buserite I, whereas the outer layers are columnar with stable todorokite (or buserite II). The growth rate of the nodule decreased from 4.39 to 2.82 mm/Myr, which may have been related to the persistently weakening of deep-sea sedimentary dynamics in the Philippine Sea since ∼1.6 Myr. The slower growth rate facilitates the enrichment of Ce, resulting in a higher REY content and strong positive Ce anomalies in the columnar structure. The mineralogical compositions and Mn/Fe ratios indicate that the nodules were primarily hydrogenetic with low diagenetic influences. The contents of Ni and Cu increase rapidly, but the trends of Co and REY display an inflection point from the hydrogenetic to diagenetic. REY was primarily enriched in Mn mineral phases, and hydrogenesis dominated the enrichment of REY. Hydrogenesis is beneficial for the enrichment of Ti, Ge, Se, Nb, and Sn. However, diagenesis facilitated the enrichment of Ga, Cd, Li, Tl, Zn, Mo, and W in the nodules of the Parece Vela Basin.

Manganese oxides mediated dissolve organic matter compositional changes in lake sediment and cadmium binding characteristics

In sediment environments, manganese (Mn) minerals have high dissolved organic matter (DOM) affinities, and could regulate the changes of DOM constituents and reactivity by fractionation. However, the effects of DOM fractionation by Mn minerals on the contaminant behaviors remain unclear. Herein, the transformations of mineral phases, DOM properties, and Cd(II) binding characteristics to sediment DOM before and after adsorption by four Mn oxides (δ-MnO2, β-MnO2, γ-MnOOH, and Mn3O4) were investigated using multi-spectroscopic tools. Results showed a subtle structural variation of Mn oxides in response to DOM reduction, and no phase transformations were observed. Two-dimensional correlation spectroscopy based on synchronous fluorescence spectra and Fourier transform infrared spectroscopy indicated that tryptophan-like substances and the amide (II) N–H groups could preferentially interact with Cd(II) for the original DOM. Nevertheless, preferential bonding of Cd(II) to tyrosine-like substances and phenolic OH groups was exhibited after fractionations by Mn oxides. Furthermore, the binding stability and capacity of each DOM fraction to Cd(II) were decreased after fractionation based on the modified Stern-Volmer equation. These differences may be attributed to DOM molecules with high aromaticity, hydrophobicity, molecular weight, and amounts of O/N-containing group were preferentially removed by Mn oxides. Overall, the environmental hazard of Cd will be more severe after DOM fractionation on Mn minerals. This study facilitates a better understanding of the Cd geochemical cycle in lake sediments under the DOM–mineral interactions, and recommends being careful with outbreaks of aquatic Cd pollution when sediments are rich in dissolved protein-like components and Mn minerals.

Binding of Cd(II) to birnessite and fulvic acid organo-mineral composites and controls on Cd(II) availability

Manganese oxide minerals (MnOs) are major controls on cadmium (Cd) mobility and fate in the environment. However, MnOs are commonly coated with natural organic matter (OM), and the role of this coating in the retention and availability of harmful metals remains unclear. Herein, organo-mineral composites were synthesized using birnessite (BS) and fulvic acid (FA), during coprecipitation with BS and adsorption to preformed BS with two organic carbon (OC) loadings. The performance and underlying mechanism of Cd(II) adsorption by resulting BS-FA composites were explored. Consequently, FA interactions with BS at environmentally representative (5 wt% OC) increase Cd(II) adsorption capacity by 15.05–37.39% (qm = 156.5–186.9 mg g−1), attributing to the enhanced dispersion of BS particles by coexisting FA led to significant increases in specific surface area (219.1–254.8 m2 g−1). Nevertheless, Cd(II) adsorption was notably inhibited at a high OC level (15 wt%). This might have derived from the supplementation of FA decreased pore diffusion rate and generated Mn(II/III) competition for vacancy sites. The dominant Cd(II) adsorption mechanism was precipitation with minerals (Cd(OH)2), and complexation with Mn–O groups and acid oxygen-containing functional groups of FA. In organic ligand extractions, the exchange Cd content decreased by 5.63–7.93% with low OC coating (5 wt%), but increased to 33.13–38.97% at a high OC level (15 wt%). These findings help better understand the environmental behavior of Cd under the interactions of OM and Mn minerals, and provide a theoretical basis for organo-mineral composite remediation of Cd-contaminated water and soil.

Unlocking the potential of sulphide tailings: A comprehensive characterization study for critical mineral recovery

Sulphide tailings are a major environmental concern due to acid mine drainage and heavy metal leaching, with costly treatments that lack economic benefits. Reprocessing these wastes for resource recovery can address pollution while creating economic opportunities. This study aimed to evaluate the potential for critical mineral recovery by characterizing sulphide tailings from a Zn–Cu–Pb mining site. Advanced analytical tools, such as electron microprobe analysis (EMPA) and scanning electron microscopy (SEM)-based energy dispersive spectroscopy (EDS), were utilized to determine the physical, geochemical, and mineralogical properties of the tailings. The results showed that the tailings were fine-grained (∼50 wt% below 63 μm) and composed of Si (∼17 wt%), Ba (∼13 wt%), and Al, Fe, and Mn (∼6 wt%). Of these, Mn, a critical mineral, was analyzed for recovery potential, and it was found to be largely contained in rhodochrosite (MnCO3) mineral. The metallurgical balance revealed that ∼93 wt% of Mn was distributed in −150 + 10 μm size fractions containing 75% of the total mass. Additionally, the mineral liberation analysis indicated that Mn-grains were primarily liberated below 106 μm size, suggesting the need for light grinding of above 106 μm size to liberate the locked Mn minerals. This study demonstrates the potential of sulphide tailings as a source for critical minerals, rather than being a burden, and highlights the benefits of reprocessing them for a resource recovery to address both environmental and economic concerns.

Insight on efficiently oriented oxidation of petroleum hydrocarbons by redistribution of oxidant through inactivation of soil organic matter coupled with passivation of manganese minerals.

While extensive works focused on the enhancement of the activity of heterogeneous Fenton catalysts, little was paid attention to the inhibition of soil organic matter (SOM) and Mn minerals in soil remediation. Here, the oxidation of petroleum hydrocarbons in soils (S1: 4.28% SOM, S2: 6.04% SOM, S3: 10.33% SOM) with inactivated SOM and passivated Mn oxides regulating by calcium superphosphate (Ca(H2PO4)2) was carried out. Oily sludge pyrolysis residue was used as precursors to prepare an oleophilic iron-supported solid catalyst (Fe-N@PR). For regulated systems, under the optimal conditions of 1.8mmol/g H2O2 and 0.05g/g Fe-N@PR, 72 ∼ 91% of total petroleum hydrocarbons (TPHs: 15,616.58mg/kg) were oxidized, which was 38 ∼ 45% higher than that of control systems. The mechanism of efficient oxidation was proposed that the passivated Mn minerals stabilized H2O2 redistributing more H2O2 to sustainably produce •OH, and the inactivated SOM improved the relative reactivity of •OH to TPHs. Additionally, the passivation of Mn oxides was mainly related to the binding of H2PO4-, and the inactivation of SOM was realized by Ca2+ combing with -OH and C-O-C to form stable complexes. This study brought us a new perspective on soil remediation through passivating Mn minerals and inactivating SOM.

Evaluation of preservation protocols for oxygen‐sensitive minerals within laminated aquatic sediments

AbstractLaminated sediments can record seasonal changes in sedimentation of material from anoxic waters, including minerals of the redox‐sensitive elements Fe, Mn, and S that form under varying oxygen levels, mineral saturation conditions, and from microbial metabolism. However, preserving the oxygen‐sensitive minerals for identification is challenging when preservation of the spatial arrangement of laminae is also required. In this study, we compare methods for embedding sedimentary materials from anoxic waters and sediments from Brownie Lake, Minnesota, USA for analysis of the speciation for Fe, Mn, and S using synchrotron‐based X‐ray absorption near edge spectroscopy (XANES). We found that acetone dehydration and resin replacement in a 100% N2 glovebox successfully preserved the speciation of Fe and Mn minerals within laminated sediments. However, acetone removed some sulfur species from sediments, and epoxies contained sulfur species, which challenged identification of native sulfur species. Results from this study will aid researchers who are interested in spatial analysis of oxygen sensitive sediments, soils, or microbial mats in choosing a preservation method.

Hematite-mediated Mn(II) abiotic oxidation under oxic conditions: pH effect and mineralization

Interactions between manganese (Mn) and iron (Fe) are widespread processes in soils and sediments, however, the abiotic transformation mechanisms are not fully understood. Herein, Mn(II) oxidation on hematite were investigated at various pH under oxic condition. Mn(II) oxidation rates increased from 3 × 10−4 to 8 × 10−2 h−1 as pH increased from 7.0 to 9.0, whereas hematite enhanced Mn(II) oxidation rates to 1 h−1. During oxidation process, high pH could promote the oxidation of Mn(II) into Mn minerals, resulting in the rapid consumption of the newly-formed H+, and high pH facilitated Mn(II) adsorption and oxidation by altering Mn(II) reactivity and speciation. Only granule-like hausmannite was found on the hematite surface at pH 7.0, whereas hausmannite particles and feitknechtite and manganite nanowires were formed at pH from 7.5 to 9.0. Moreover, a co-shell structured nanowire composed of manganite and feitknechtite was observed owing to autocatalytic reactions. Specifically, electron transfers between Mn(II) and O2 occurred on the surface or through bulk phase of hematite, and direct electron transfers in the O2-Mn(II) complex and indirect electron transfers in the O2-Fe(II/III)-Mn(II) complex may both have contribution to the overall reactions. The findings provide a comprehensive interpretation of Fe-Mn interaction and have implications for the formation of soil Fe-Mn oxyhydroxides with unique properties in controlling element cycling.

Proximate composition and mineral content of spices increasingly employed in the Mediterranean diet.

The present study aimed to investigate the nutritional constituents of common market available spices in the United Arab Emirates. Seven commonly consumed spices namely, ginger (Zingiber officinale), cinnamon (Cinnamomum verum), black seed (Nigella sativa), fenugreek (Trigonella foenum-graecum), cardamom (Elettaria cardamomum), cloves (Syzygium aromaticum) and saffron (Crocus sativus) were obtained from local markets. Proximate analyses were performed according to AOAC procedures. Assessment of major (Ca, K, Mg, Na, P and S) and minor (Co, Cu, Fe, Mn and Zn) elements was conducted using inductively coupled plasma optical emission spectrometry (ICP-OES). Findings revealed varying macronutrient, micronutrient and mineral contents which are highly valuable for dietary purposes. The present study demonstrates that these edible spices could be used for nutritional support, due to their micro and macronutrient contents.

Elemental Analysis of Propolis Tinctures by Microwave Plasma – Atomic Emission Spectrometry (MP-AES)

Propolis tinctures are popular alternative medicines, but mandatory labeling requirements relating to the inorganic content or percentage of ethanol are absent. Knowing the elemental content is useful for quality assurance/quality control of the tinctures between batches, as well as the safety of the products for consumers. Microwave plasma – atomic emission spectrometry (MP-AES) is a relatively low-cost, robust, multielemental technique that can analyze ethanolic extracts of propolis following minimum sample preparation. However, there are no published papers using MP-AES for this application. The technique was evaluated for the determination of sixteen elements in lab-made preparations and in 23 products from markets in Mexico. The matrix effects of the ethanol content of the samples were also evaluated and were found to affect the detection limit of some elements. There was high variability in the elemental composition of the major (K, Fe, Mg, and Na) and minor (Al, Cd, Co, Cr, Cu, Mn, Ni, and Zn) elements among the samples. The median concentrations of cadmium, and lead in the propolis tinctures were below 0.28 µg·L−1 and 2.8 µg·L−1, respectively.

Nation-wide concentration and spatial distribution of manganese with links to manganese mineralization in China

There has been an increasing demand for manganese (Mn) in modern industries for the production of steel and power batteries in China. However, the lack of Mn reserves and poor quality of Mn resources in China have increased dependence on imported Mn. Therefore, it is essential to understand the concentration and distribution of Mn throughout China. The China Geochemical Baselines project provides nationwide Mn baseline data from 3382 soil samples and 11,605 rock samples. Based on these data, this study presents the concentrations and spatial distribution of Mn in China. Manganese concentrations in the top and deep soil samples vary from 40 to 11,546 μg/g and from 46 to 11,595 μg/g, respectively; the median concentrations are 569 μg/g and 562 μg/g, respectively. The median Mn content of rock samples is 471 μg/g. Ultramafic and mafic rocks have relatively high-Mn concentrations (1007 and 1257 μg/g based on 51 and 551 samples, respectively). The spatial distribution pattern of Mn throughout China is mainly linked to lithology, geomorphic landscapes, and areas of mineralization. Parent rock types, particularly mafic rocks, may govern the distribution of Mn enrichment in the soil of China. The concentration centers of Mn anomalies (>P97.5) showed good correlation with known Mn mineralization. Therefore, the results of this study may provide exploration indicators and targets for Mn deposits.

Mohammadabad Manganese deposit, southwest Sabzevar basin, Iran: Evidence of sea-floor exhalation and geochemical studies in the late Cretaceous volcano-sedimentary sequence

The southwest Sabzevar basin in northeast Iran is one of the most important areas for volcanogenic stratiform manganese deposits. The Mohammadabad Mn deposit, found in this basin, is hosted by the upper late Cretaceous marly tuffs in a region that has an active history of tectonism. Their geology, mineralogy and geochemistry, including major, trace and rare earth elements (REE), are described in this work. The main ore minerals include pyrolusite, psilomelane, cryptomelane, with minor braunite and manganite. Four styles of manganese mineralization are recognized: (1) layered; (2) nodular; (3) disseminated; and (4) replacement to massive. Regardless of style, pyrolusite, psilomelane, and cryptomelane usually tend to parallel the stratification of sediments, while braunite veins occur in high angle fractures. The replacement of radiolarian and foraminiferal fossils by manganese minerals during diagenesis near the seawater-sediment interface suggests that mineralization occurred in oxygen-rich conditions under the influence of low-temperature hydrothermal fluids. The geochemistry of trace elements of manganese oxides and rare earth elements gives clear evidence of hydrothermal-exhalative origin for Mohammadabad deposit. In general, ore minerals have Co/Ni ratios above 0.12, and U/Th ratios vary from 0.13 to 11.29. The presence of negative Eu anomalies in manganese minerals shows that the ore-forming fluids were generally low-temperature and oxic during mineral formation. In-situ mineralogy studies based on SEM-EDS have distinguished syngeneic and diagenetic Mn systems during the formation of manganese mineralization. The Mohammadabad deposit is considered a typical case of volcanic hydrothermal exhalative-diagenetic Mn mineralization, in which minerals deposited when hydrothermal fluid was released from oxic to dysoxic water columns.

High Fe and Mn groundwater in the Nanchang, Poyang Lake Basin of China: hydrochemical characteristics and genesis mechanisms.

Based on the water quality test data of 257 groups of phreatic groundwater and 165 groups of confined groundwater in the Nanchang area and the redox conditions, acid-base conditions and the organic matter content in groundwater, we identified hydrochemical characteristics and genesis of groundwater with high Fe and Mn contents in Nanchang. The results showed that Fe and Mn exceeded the standard in both phreatic and confined groundwater. The over-standard rates of Fe and Mn in groundwater were 8.56-11.52% and 33.07-36.36%, respectively. The degree of pollution Fe and Mn in the confined groundwater is higher than that in the phreatic groundwater, and the degree of pollution caused by Mn is higher than that caused by Fe. The high Fe and Mn contents in groundwater were caused by the release of Fe and Mn minerals from the native environment due to changes in the groundwater environment of the study area. A mild redox environment (Eh < 100) and low pH value are favorable for Fe and Mn enrichment in groundwater. The presence of organic matter accelerates microbial activity and promotes the release of Fe and Mn from aquifer sediments. Therefore, the change in the native environment played an important role in the increase in Fe and Mn content in the study area.