Manganese Minerals Research Articles

Zircon U–Pb geochronology of manganese-rich rocks from the Borborema Province, Northeast Brazil: adding a new piece to the global inventory of Paleoproterozoic manganese mineralization

Zircon U–Pb geochronology of manganese-rich rocks from the Borborema Province, Northeast Brazil: adding a new piece to the global inventory of Paleoproterozoic manganese mineralization

INESITE, HUBEITE, RUIZITE, APOPHYLLITE, AND MANGANOAN ILVAITE FROM CAVNIC, EASTERN CARPATHIANS, ROMANIA

The rare minerals, inesite, Ca2Mn2+7Si10O28(OH)2·5H2O, hubeite, Ca2Mn2+Fe3+Si4O12(OH)·2H2O, and ruizite, Ca2Mn3+Si4O11(OH)4·2H2O, were determined, for the first time, by optical and XRD analyses, at Cavnic (Baia Mare Neogene metallogenetic district, Eastern Carpathians, Romania) in a gold-bearing, base metal deposit. Inesite was refined as triclinic, in space group P1 (2), and has the following unit-cell parameters (refined from X-ray powder diffraction data): a = 8.927(7) Å, b = 9.245(8) Å, c = 11.954(9) Å; α = 91.80(2)°, β = 132.60(1)°, γ = 94.37(3)°, V = 719.45(12)Å3. Hubeite was also refined as triclinic, in space group P1, and has as unit-cell parameters: a = 9.960(7) Å, b = 13.870(9) Å, c = 6.562(4) Å, V = 601.19(17) Å3; α = 133.19(5)°, β =101.50(3)°, γ = 66.27(4)°. Ruizite was refined on a monoclinic cell, space group A2 (5) and has the following unit-cell parameters: a = 11.974(9)Å, b = 6.175(5)Å, c = 9.052(7)Å, V = 669.12 (9)Å3; β = 91.34(3)°. Apophyllite, KCa4Si8O20(F,OH)·8H2O, is tetragonal, space group P4/mnc (128), and has a = 8.960(3) Å, c = 15.767(7) Å and V = 1265.80(11) Å3. The terms identified represent a solid solutions series between the two end-members, fluorapophyllite and hydroxyapophyllite. Manganoan ilvaite, CaFe2+Fe3+(Fe2+, Mn)(Si2O7)(O)(OH), crystallizes in the space group Pnam (62), and has as unit-cell parameters: a = 13.008(7) Å; b = 8.865(5) Å; c = 5.845(3) Å, V = 674.02(9) Å3. The textural relations of inesite /hubeite/ruizite /apophyllite/manganoan ilvaite assemblage show that the oldest mineral is manganoan ilvaite, as inesite and hubeite overgrow and engulf this mineral. Hubeite is indicative for mildly oxidizing crystallization, conditions. Both hubeite and ruizite are Ca-Mn hydrated silicates. However, all Mn is divalent in hubeite and trivalent in ruizite. In addition, ruizite is Fe-free, whereas hubeite contains significant Fe3+. Ruizite Ca2Mn3+Si4O11(OH)4.2H2O was formed under higher oxidizing conditions as compared with hubeite. Sudoite and specularite also occurs in this oxidized assemblage. Sudoite, Mg2(Al.Fe3+)3Si3O10(OH)8, is monoclinic and has as space group C2m (12) and as unit-cell parameters a = 5.237(2) Å, b = 9.070(5) Å, c = 14.285(8), β = 97.00, V = 673.47(14) Å3. The carbonate closely associated to this assemblage is a Mn- and Ca-bearing siderite, which crystallizes in space group R-3c (167), having as unit-cell parameters: a = 4.694(1) Å; c = 15.386(5) Å, and V = 293.53(13) Å3. The secondary minerals occurring in this assemblage as determined by X-ray powder diffraction are: gold, sphalerite, pyrite, and galena. The origin of vein assemblage inesite /hubeite /ruizite /apophyllite is hydrothermal (epithermal); there exist indications of a genesis at low temperature, around 200°C. The assemblage indicated before is grown on manganoan ilvaite, which is the oldest mineral in this association. There are no signs of the genesis of manganoan ilvaite /inesite /hubeite /ruizite assemblage at the expense of higher T anhydrous manganese minerals such as rhodonite or johannsenite.

Study on the ability of Eichhornia crassipes L. plant to absorb manganese from polluted water

This study was conducted on the Eichhornia crassipes plant and tested its ability to remove the Manganese (Mn) from contaminated water through the absorption of this element and its accumulation inside the tissues, and the plant was dosed with Mn element at a concentration of 0.8 mg/l, where the results showed after digesting the plant in the laboratory the ability of the root system of E.crassipes to absorb the mineral Manganese and accumulate it inside its tissues until it reached the highest values in 21st day of the experiment, its concentration was 181 mg/kg in the roots, while it reached the highest concentration of leaves in 14th day of the experiment even reach to 93.1 mg/kg. As for the percentage of Manganese removal, the results showed a significant ability of the E.crassipes to absorb the element Mn throughout the days of the experiment, where it recorded 99.7% in 7th, 14th day, while noted non-significant decrease at 21st day to record about 99.6% of the total concentration in water. Thus, we can submit a scientific explanation of the possibility of using the plant under study in the bioremediation of contaminated water.

Mineralogy and geochemistry of Kliripan manganese ore deposit, Hargorejo Village, Kokap District, Kulonprogo Regency

This study discusses the mineralogy and geochemistry of manganese deposits in the Kliripan area, where manganese had been mined since the Dutch occupancy until the 1970s. Although mining has been discontinued since then, the demand for manganese has increased in various industries, prompting exploration to continue to meet this demand. We performed petrographic, XRD, and XRF analysis of the ore and wall rock samples. Jasper and grainstone from the Sentolo Formation are the two lithologies where manganese mineralization occurs. Manganese-bearing minerals include pyrolusite, manganite, rhodochrosite, and lithiophorite, while the gangue minerals consist of quartz, calcite, hematite, and clay minerals. We interpret that Jasper is a product of alteration and has MnO content as high as 5.02 wt.%. Meanwhile, the economic grade manganese ore in grainstone has an MnO content up to 48.51 wt.%. The elements Ce, Zr, Co+Ni+Cu, are important discriminants to determine the type of manganese deposit. The results showed that the diagenetic process in reductive water formed the manganese ores. Oxidation of divalent manganese ion formed pyrolusite and manganite. Rhodochrosite crystallized when dilute manganese solution reacts with CO2 from limestone diagenesis. We concluded that the Kliripan manganese ore deposit has both hydrothermal and diagenetic deposits.

Ni-Co Bearing Laterites from Halmahera Island (Indonesia)

Eastern Indonesia, including the island of Halmahera, is a region with a high mineral potential, particularly Ni-Co, Au-Cu, and Ag ores, which are a globally important and critical source of raw materials (CRMs). The research was conducted within the framework of scientific cooperation between the Faculty of Geology, University of Warsaw (Poland), and PT Halmahera Resources Percasa Ltd. (Jakarta, Indonesia) Between the years of 2009 and 2011, 42 boreholes were drilled using an impact system (up to 15 m below surface) and 3 test pits (up to 8 m below surface). The presence of a laterite deposit containing Ni-Co mineralization was identified on the license area. The resources estimated in accordance with JORC Code, with a cut-off grade Ni ≥ 0.5%, equaling 185,510 t Ni and 17,747 t Co, with the stock of raw material amounting to 14.8 million t and with an average content of 1.00% Ni and 0.13% Co. The ore in the deposit has mixed character. To date, studies have shown the dominance of oxide ore, but saprolite composed of magnesium silicates was also identified in significant amount. The Ni mineralization in oxide ore (limonite) is bound to goethite and manganese minerals, while in the case of silicate (saprolite) ore, it occurs locally in the form of veins as well as zonally in the weathered serpentinites. Cobalt mineralization is almost entirely related to the Mn minerals that occur in the lower oxide zone. It has been found that both serpentinites and harzburgites (and possibly locally lherzolite) are the parent rocks for laterite deposit.

Transformations and Speciation of Iodine in the Environment as a Result of Oxidation by Manganese Minerals

Transformations and Speciation of Iodine in the Environment as a Result of Oxidation by Manganese Minerals

Tunnel cation and water structures of todorokite: Insights into metal partitioning and isotopic fractionation

Tectomanganate todorokite and phyllomanganate vernadite are the two major manganese minerals in marine ferromanganese sediments that contain large quantities of trace metals. Todorokite has a less clear metal partitioning mechanism than vernadite, mainly because the metal cation and water structures in the tunnel cavities remain poorly understood. Here, we report the composition-dependent tunnel-cation site disorder of todorokite obtained from molecular dynamics (MD) simulations. Our simulations of homocationic Ni2+-, Zn2+-, Mg2+-, Ca2+-, or Na+-todorokite revealed that tunnel cations form inner-sphere (IS) complexes with Mn octahedral surface at low hydration states, but at higher hydration states, outer-sphere (OS) complexes are the dominant cation species located at the center of the tunnel. However, K+ and Cs+ form only IS complexes regardless of the tunnel hydration state. Optimum water contents were determined based on the free energy changes associated with water intercalation into the tunnel cavities calculated as a function of water content for two heterocationic todorokite models: Mg0.5Na0.4Ca0.1Mn6O12·nH2O (Mg/Mn = 0.08, average Mn oxidation state = +3.73) and Mg1.1K0.1Ca0.1Mn6O12·nH2O (Mg/Mn = 0.18, average Mn oxidation state = +3.58). These models emulate the chemical compositions of well-characterized terrestrial and marine todorokite samples, respectively. At each optimum water content, MD simulations revealed that OS complexes are the major Mg2+ species in the former model. However, IS complexes are the major Mg2+ species in the latter model, indicating that the tunnel cation speciation of diagenetic todorokite can be influenced by the sediment pore-fluid chemistry. The atomic tunnel cation and water structures of todorokite provide a molecular basis for understanding of metal partitioning to Mn oxides and interpretation of metal stable isotopes recorded in ferromanganese nodules.

Mineralogy and Origin of the Manganese Deposit in the Sulaimani Province, Kurdistan Region of Iraq: Insight to Serpentinization-Induced Manganese Production Scenario

The Manganese deposits in Sulaimani metallogenic province mainly occur within the top Qulqula Radiolarite chert unit of the Penjween ophiolite complex as strata bound type deposits near Kani Saif village, 15 km south of the Penjween district within the Imbricated zone, Kurdistan Region of Iraq. A restricted occurrence of massive manganese boulders was identified, 1 km north to the Mawat District, associated with the Oligocene Merga Red beds Group. The Qulqula Radiolarite represents the Middle Jurassic-Early Cretaceous sedimentary cover of Neo-Tethys oceanic crust deposits throughout the early to mature stages of the Neo-Tethys ocean opening along the northern and eastern margins of the Afro-Arabian plate. The field and petrographical data indicated that the nature of manganese mineralization in the area is of various forms including veins, brecciated, micronodules, banded and massive types. Reflected light microscopy, high resolution scanning electron microscope and X-ray diffraction reveal that the mineral assemblages are dominated by barunite, rhodinite, hematite, quartz and carbonate for the massive metamorphosed type deposit in the Mawat area. Meanwhile, the mineralogy of the vein, micronodule and banded types are simple and dominated by pyrolusite, hollandite minerals close to Kain Saif village. Combinations of the modal manganese minerals, filed and textural observations, a paragenetic-time model suggests that the manganese deposit in the area formed via a sequence of multiple processes (1) serpentinization of the upper mantle at mid oceanic ridge during the Cretaceous period, (2) deposition from diluted hydrothermal fluids in the Neo-Tethys mature oceanic basin, (3) the diagenetic modification of the manganese bearing sediment and (4) metamorphism of sediment a combing Zagros orogeny in Paleogene. Overall data suggest that the manganese deposits in the Kurdistan region of Iraq are cogenetic and spatially related to those which occur along the entire margin of the Arabian plates from Oman to Turkey associated with the radiolarite facies.

TEXTURAS DOS MINERAIS DE MINÉRIO DA REGIÃO AMAZÔNICA. PARTE 1

Ore minerals are usually characterized to the formation of mineral deposits. Textures can provide evidence of the nature of processes such as initial ore deposition, post-deposition rebalancing or metamorphism, deformation, annealing and weathering. The recognition and interpretation of textures is usually the most important step in understanding the origin and evolution of an ore. As they are ores that contain high economic value, and their study is necessary to correctly define the metallurgical alternatives for an adequate process of obtaining metallic products. Among the most important mines that are operating in Carajás are N4 (iron), Azul (manganese), Sossego and Salobo (copper) and Onca Puma (nickel). Most ores, show opaque characteristics that can be well studied by microscopy of opaque minerals, but others with SEM/EDS. The textures of these ore minerals are distinctive among them, highlighting the disseminated copper minerals subject to mineral liberation and micritic manganese minerals and fines granulates nickel-bearing minerals, ready for metallurgical extraction. Keywords: bornite; chalcopyrite; cryptomelane; chysotile; lizardite.

Geology and minerageny of the Bestobe deposit (Central Kazakhstan)

Polygenic stratiform deposits are the largest in the world in terms of barite and manganese reserves, as well as lead and zinc reserves. In the mineral resource complex of the Republic of Kazakhstan, they are of great importance and are distinguished as an independent genetic Atasu type. In the article, the deposits of the Zhailma graben-syncline in a large riftogenic structure are considered as a reference for the Atasu type. The geological structure of the Bestobe stratiform polymetallic deposit located in the eastern part of the Zhailma synclinorium is presented. The stratigraphy of ore formations, mineralization features, morphology of the ore body and the pattern of zoning the distribution of elements in the ore-bearing rocks of the Bestobe deposit are shown. A feature of the deposit is the combination of layered iron-manganese and lead-zinc ores and superimposed zinc-lead-barite mineralization; the sharply subordinate role of hydrothermal-sedimentary ores in the total reserves of lead and zinc; comparative abundance of lead, copper and silver sulfosalts. The analysis of the materials indicates that mineralization at the Bestobe deposit is complex. Its main value is polymetallic ores. The role of iron ore mineralization of the deposit is insignificant. Manganese mineralization is practically absent. Polymetallic ores are conventionally subdivided into lead-zinc-barite, lead-barite, barite and lead-zinc. Strontium is a constant impurity in barites. Lead is mainly concentrated in galena; its insignificant amount is found in geocronite, boulangerite, jamsonite, bournonite, cerussite, anglesite, pyromorphite, plumboyarosite. The bulk of zinc is concentrated in the form of sphalerite.

Super-hydration and reduction of manganese oxide minerals at shallow terrestrial depths

Manganese oxides are ubiquitous marine minerals which are redox sensitive. As major components of manganese nodules found on the ocean floor, birnessite and buserite have been known to be two distinct water-containing minerals with manganese octahedral interlayer separations of ~7 Å and ~10 Å, respectively. We show here that buserite is a super-hydrated birnessite formed near 5 km depth conditions. As one of the most hydrous minerals containing ca. 34.5 wt. % water, super-hydrated birnessite, i.e., buserite, remains stable up to ca. 70 km depth conditions, where it transforms into manganite by releasing ca. 24.3 wt. % water. Subsequent transformations to hausmannite and pyrochroite occur near 100 km and 120 km depths, respectively, concomitant with a progressive reduction of Mn4+ to Mn2+. Our work forwards an abiotic geochemical cycle of manganese minerals in subduction and/or other aqueous terrestrial environments, with implications for water storage and cycling, and the redox capacity of the region.

MICROBIOLOGICAL QUALITY, CHEMICAL AND SENSORY ASSESSMENT OF LOCALLY PACKAGED CASHEW NUTS SOLD IN BENIN CITY, NIGERIA

Chemical, microbial and sensory analyses of processed cashew nuts (Anacardium occidentale) samples commonly marketed in Benin City was evaluated using standard methods. The pH and moisture content ranged from 4.9±0.05 -5.6±0.06 and 3.42±0.05 - 5.35±0.3% respectively. Proximate analysis showed the cashew nut samples contained protein (32.55 ± 0.00- 35.73 ± 0.10 %), carbohydrate (17.70 ± 0.40-19.39 ± 0.00 %), lipid (9.18 ± 0.30-10.37 ± 0.20 %), ash ( 8.76 ± 0.50-9.65 ± 0.13%) and fibre (7.57 ± 0.30-8.14 ± 0.10 % ) in the range indicated respectively. The minerals with the highest concentration include potassium, phosphorus and magnesium in the range 662±5.50-665±3.20, 588±1.86-593±2.10 and 293±2.41-297±3.10mg/100g in that order. Of all the minerals manganese had the least concentration of 1.67±0.35-1.70±0.60mg/100g. Microorganisms isolated from stored processed cashew nut samples include: Staphylococcus aureus, S. epidermidis, Bacillus spp, Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Saccharomyces spp, Penicillium digitatum, Penicillium spp, Rhizopus nigricans and Mucor pusillus. No Escherichia coli and Salmonella spp were isolated from the samples. The fungal count after 28 days storage in various packaging material revealed less than 103 cfu/g for two of the samples. Sensory evaluation showed that storage in glass bottle is the best as it rated closest to the fresh product after 28 days storage at 28±20C.

Evidence for the oxidation of Earth\u2019s crust from the evolution of manganese minerals

Analysis of manganese mineral occurrences and valence states demonstrate oxidation of Earth’s crust through time. Changes in crustal redox state are critical to Earth’s evolution, but few methods exist for evaluating spatially averaged crustal redox state through time. Manganese (Mn) is a redox-sensitive metal whose variable oxidation states and abundance in crustal minerals make it a useful tracer of crustal oxidation. We find that the average oxidation state of crustal Mn occurrences has risen in the last 1 billion years in response to atmospheric oxygenation following a 66 ± 1 million-year time lag. We interpret this lag as the average time necessary to equilibrate the shallow crust to atmospheric oxygen fugacity. This study employs large mineralogical databases to evaluate geochemical conditions through Earth’s history, and we propose that this and other mineral data sets form an important class of proxies that constrain the evolving redox state of various Earth reservoirs.

Diurnal Oxidation for Manganese Minerals in the Arctic Ocean

The relative abundance of different oxidation states for this important micronutrient varies on the basis of how much available sunlight there is.

Genetic diagnosis of basal ganglia disease in childhood.

To correlate clinical, radiological, and biochemical features with genetic findings in children with bilateral basal ganglia lesions of unknown aetiology, and propose a diagnostic algorithm for early recognition. Children with basal ganglia disease were recruited in a 2-year prospective multicentre study for clinical, biomarker, and genetic studies. Radiological pattern recognition was examined by hierarchical clustering analysis. We identified 22 genetic conditions in 30 out of 62 paediatric patients (37 males, 25females; mean age at onset 2y, SD 3; range 0-10y; mean age at assessment 11y, range 1-25y) through gene panels (n=11), whole-exome sequencing (n=13), and mitochondrial DNA (mtDNA) sequencing (n=6). Genetic aetiologies included mitochondrial diseases (57%), Aicardi-Goutières syndrome (20%), and monogenic causes of dystonia and/or epilepsy (17%) mimicking Leigh syndrome. Radiological abnormalities included T2-hyperintense lesions (n=26) and lesions caused by calcium or manganese mineralization (n=9). Three clusters were identified: the pallidal, neostriatal, and striatal, plus the last including mtDNA defects in the oxidative phosphorylation system with prominent brain atrophy. Mitochondrial biomarkers showed poor sensitivity and specificity in children with mitochondrial disease, whereas interferon signature was observed in all patients with patients with Aicardi-Goutières syndrome. Combined whole-exome and mtDNA sequencing allowed the identification of several genetic conditions affecting basal ganglia metabolism. We propose a diagnostic algorithm which prioritizes early use of next-generation sequencing on the basis of three clusters of basal ganglia lesions.

Genesis of the Enkafela Mn deposit: a record of submarine hydrothermal activity in the Afar Depression, Northeast Ethiopia

ABSTRACT The genesis of the Enkafela Mn deposit and associated processes were investigated using field mapping, mineralogical and geochemical analyses by XRD, ICP-MS/AES and XRF. The geology is constituted by limestone, evaporites/gypsum, conglomerates and basalt. The orebody is hosted in the limestone and has two distinctive manganese layers: a massive bottom and powdery top. Pyrolusite, romanechite and birnessite are the major ore minerals. The geochemical results indicate elevated MnO (av. 70.25 wt-%), Ba (>10,000 ppm), Sr (>10,000 ppm) and depleted Fe2O3 (av. 0.37 wt-%) and other metals. The massive orebody has higher (172.9 ppm) REE content than the powdery ore (7.84 ppm). Chondrite normalised REE plot shows LREE enrichment for both orebodies. The massive manganese layer shows enrichment in Ce and no Eu anomaly. The powdery manganese is depleted in Ce and Eu. The geochemical and mineralogical studies indicate that the manganese mineralisation has dual sources: hydrogenous and hydrothermal sources (for the massive orebody), and hydrothermal (for the powdery). The data suggest that there was active submarine hydrothermal activity in Dallol associated with the regional geodynamic events while the area was inundated by the Red Sea during the Pleistocene.

Occurrence of Manganese Mineralization in Rayavalasa and Tudi Villages of Eastern Ghat Mobile Belts, Andhra Pradesh

In this paper, we have reported small bands of Manganiferous quartzite at S. Gopalapuram, Tudi, .Some other small occurrences also observed as float ore/boulders and/or small manganese ore observed north of Nandala-meta, Tangidi and Rayavalasa The pockets of Mn ores are lithologically controlled but the disposition of manganese bands are structur-ally controlled, localized near the hinge zones and at some parts in the limb areas. The Mn-rich silicates are converted to manganese ore due to leaching or oxidation. The relict phases of silicate with Mn-rich rim and inclu-sions indicate that they were derived during leaching. Some features such as colloform bands, relict silicates and rare pseudomorphs, indicate its secondary nature formed due to the alteration of manganiferous silicates. Braunite, and psilomelane are represented as the primary minerals. secondary minerals are made up of psilomelane, cryptomelane, py-rolusite, and goethite and are formed in the low grades of metamorphism. Analytical val-ues of manganese (Mn) in bedrock samples collected from the Mn-enriched horizons of calc-granulite and khondalite rock types range from 0.16% to 39.70%. The analytical results of float ore samples have maximum values of upto 23.64%

The origin of manganese formations at Çağalali Hill and Kevri̇kevr Hill related to the late Triassic rifting of the South Neotethys, SE Turkey: The geological, mineralogical and geochemical components

The Koçali Complex includes continental rifting and subduction-related units that make up the southern Neotethys. This complex is a folded, tectonic-segmented succession with lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganese deposits (the Tarasa and Konak formations) and ophiolitic units (the Kale formation). Manganese mineralizations in the host formation are found in banded, lenticular and massive forms within red to brown radiolarian cherts. Pyrolusite and polianite are the main manganese minerals, while psilomelane, manganite and minor hausmannite are other manganese minerals. Gangue minerals include quartz and carbonate, with minor barite being observed. The geochemical proofs (MnO: 8.98–73.64%, SiO2: 3.26–86%) originating from the main oxides indicates a hydrothermal rooted source for the manganese mineralization. This is confirmed by anomalies and trace element patterns including very low Fe/Mn (<0.1), low Co/Zn ratios (mean 0.86), very low ∑REE contents (mean 34.67), slightly negative Eu* value (mean 0.74) and low Ce* value (mean −0.23). Manganese-oxide mineralizations observed in the volcanic sedimentary succession of the Koçali Complex have been interpreted as hydrothermal deposits associated with volcanism during the post-rifting seafloor extension of the southern Neotethys during the Late Triassic period.

Sedimentary Setting and Ore-Forming Model in the Songtao Manganese Deposit, Southwestern China: Evidence from Audio-Frequency Magnetotelluric and Gravity Data

The break-up of the supercontinent Rodinia in the late Neoproterozoic led to the formation of the Nanhua rift basin within the South China Block. The Datangpo-type manganese deposit, which developed in the Nanhua rift basin, is one of the most important types of manganese deposits in South China. Although it is widely accepted that deep sedimentary structures significantly affect the manganese ore system, the relationship between the manganese deposits in South China and the Nanhua rifting process is still unclear. The origin of the manganese ore layer remains controversial. In this paper, we integrated the audio-frequency magnetotelluric (AMT) data, gravity data, and comprehensive geological and borehole data analysis to characterize the structure of the Datangpo-type manganese deposit in Songtao, Guizhou Province. The resistivity and density models produced an inclined layered structure, which correlated well with the coeval sediment strata of the Nanhua rift basin. A high-resistivity cap was observed from the surface to a depth of 800 m, corresponding to the Cambrian Loushanguan (ϵ3−4ls) and Palang dolomite formation (ϵ2p), which has helped the storage of the manganese ore. The most significant low-resistivity anomaly (25–40 Ω·m) resides at a depth of 1400 m in the Nantuo (Nh3n) gravel sandstone and Datangpo (Nh2d) silty and carbonaceous shale, corresponding to the ore-forming layer. This distinct low-resistivity layer was possibly produced by aqueous fluids and pyrite in the syn-sedimentary fault and alteration zone. The accumulations of sulfide minerals in the rock samples suggest a possible anoxic-euxinic deposition environment during the manganese mineralization and precipitation. The fault revealed in the resistivity models is perhaps a previous fault zone produced by extension in the Nanhua rifting process, which provided migration and upwelling channels for ore-forming minerals. Based on our resistivity models, density models, and geological survey, the manganese ore-forming model was derived, which can help to provide geophysical evidence for the origin of the Datangpo-type manganese deposit.

Environmental Aspects of Historical Ferromanganese Tailings in the Šibenik Bay, Croatia

The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the recently collected tailings, as well as in the dust collected on the roof of the plant during the production period, are bustamite and Mn-oxides. The same type of Mn mineral phases was also found in recently collected sediments from Šibenik Bay. Detailed chemical and phase analyses (XRD, BCR sequential analysis, aqua regia and lithium borate fusion) of the dust sample revealed high manganese values (24.1%), while granulometric analysis showed that 50% of the particles are smaller than PM2.5. The influence of the tailings is visible in the sediment, but the concentrations of the potentially toxic elements determined by the sequential BCR analysis are within the legal limits. Some higher values (20.3 g/kg Mn, 595 mg/kg Pb and 494 mg/kg Zn) are detected in the tailings, which are still exposed to weathering and as such should be additionally monitored. On the other hand, this material contains a considerable number of elements that could be considered lucrative (∑ REE up to 700 mg/kg, Mn up to 23 g/kg, Fe up to 37 g/kg and Al up to 25 g/kg), opening the possibility of reuse and recovery.