Secondary Minerals Research Articles

ВПЛИВ МІГРАЦІЇ ФЛЮЇДІВ НА МАГНІТНУ МІНЕРАЛОГІЮ ҐРУНТІВ

Background. The war in Ukraine arises the urgent need to intensify hydrocarbon production on its own territory in order to maintain and develop the country's energy independence. The effectiveness, low cost and relevance of the involvement are demonstrated by magnetic methods of studies of the near surface geological section and the soil for the oil and gas prospecting. Methods. The methodology of magnetic studies for the hydrocarbon prospecting is based on the methods of studying the environmental magnetism and soil, precision magnetic survey of natural systems and authigenic models of changes in magnetic mineralogy under the influence of hydrocarbon fluid migration. Results. The crucial aim is to distinguish the sources of the formation of the magnetic minerals. In most cases, soils contain minerals of natural pedogenic origin, authigenic secondary magnetic minerals, and sometimes detrital fine-coarse magnetic phases. For Ukraine, magnetite, maghemite, hematite, and goethite are the most common magnetic minerals of soils of the pedogenic origin. At the same time, the experience of conducting magnetic mineralogical analyzes of soils in the territories of oil and gas deposits indicates the presence of iron sulfides. First of all, monoclinic pyrrhotite is identified. The soils also contain accompanying hexagonal pyrrhotite, pyrite, and greigite. The results of thermomagnetic analyzes and hysteresis loops of soil samples collected at the territories of hydrocarbon deposits are presented and their mineral composition is analyzed. Conclusions. The results of the study of the impact of hydrocarbon fluid migration (microseepage) on the change in the mineral composition of soils indicate significant informativeness and the perspective of introducing the method into the complex of geological exploration works at various stages. Authigenic changes of magnetic minerals in the near surface geological section and soil, as well as natural and anthropogenic accumulation of hydrocarbon products in soils, cause changes in magnetic properties and form magnetic field anomalies.

Simultaneous Estimation of Quercetine and Betanine by RP-HPLC from Herbal Formulations Used in Nutritional Deficiencies

Background: Medicinal plants have curative properties due to the presence of various complex chemical substances of different compositions, which are found as secondary plant metabolites in one or more parts of the plants. Moringa oleifera from Moringaceae and Beta vulgaris root are, native to India, grows in the tropical and subtropical regions of the world. It is commonly known as 'drumstick tree' or 'horseradish tree' or 'miracle tree’. Incorporation of more herbal powder leads to much complexity. Above plants were chosen for their utmost nutritional values. Result: Herbal tablet and granules were prepared and evaluated further for various Physico-chemical parameters as a nutritional supplement. Promising results indicate that prepared formulations have potential as supplements. Conclusion: Present communication mainly focused on estimation of marker components by Reverse Phase-High Performance Liquid Chromatography. It showed the presence of enough number of secondary metabolites and minerals which can be easily consumed by all age groups.

Lithological and mineralogical signs of the formation and destruction of the Bashkirian stage oil deposits within the Sokskaya saddle

Oil deposits in sections of the Bashkirian stage of the Sokskaya saddle are considered. It has been established those oil-bearing limestones are represented by leached peloidal-clumpy grainstones. The rocks were formed within the shallow shelf of sedimentation basin of normal salinity. The active hydrodynamics of the aquatic environment predetermined the dense structural packing of organic residues. The migration of aggressive oil-water fluids contributed to leaching of calcite cement from grainstones. Subsequently, the pore-cavernous space was filled with oil. The introduction of edge formation waters into oil-bearing reservoirs contributed to the oxidation of oil and the manifestation of secondary diagenetic mineralization. The initial stage of waterflooding was indicated by dolomitization of reservoir rocks. Due to an increase in the partial pressure of carbon dioxide in the pore space of rocks, calcite is metasomatically replaced by diagenetic dolomite. At this stage of reservoir rock alteration, a relatively small amount of oil is recovered from oil-bearing formations. The introduction of formation waters enriched with sulfate ions into reservoir layers leads to the precipitation of gypsum-anhydrite aggregates in the pore space of oil-bearing limestones. Calcium sulfate minerals clog the pore-capacitive space of reservoir rocks, reducing their productivity. At the stage of precipitation of gypsum-anhydrite aggregates, mainly mineralized brines with an admixture of oil are extracted from reservoir rocks.

Provenance of Beach Sands in the Northern Gulf of Guinea, SW Cameroon

Abstract Petrographical, mineralogical and geochemical studies were carried out on the beach sands of Limbe (South-West Cameroon) to highlight their provenance, source rocks alteration and the tectonic framework. The Limbe beach sediments were classified as sandy litharenite type. The sediments were derived from mafic and andesite source rocks. The sediments are composed of quartz, olivine, augite, amphibole, pyroxene, plagioclase, potassium feldspar, muscovite and biotite, indicating the primary phases of magmatic source rocks; kaolinite and illite in the secondary phase; and rutile in their residual composition. The presence of ferromagnesian minerals indicates that they were derived from the mafic rocks, which are the basalts of the Cameroon Volcanic Line (CVL). However, the presence of quartz associated with plagioclase and feldspars suggests that alkaline granites played a minor role in the sedimentation of the Limbe beaches. Total Quartz - Total Feldspar - Total Lithic Fragments (Qt-Ft-Lt) mineralogical relationships demonstrate that these beach sediments would be formed in an undissected arc tectonic context, typical of volcanic sources with high relief producing black sands or sands enriched in iron oxides. Their microscopic characteristics of angular to subangular shapes suggest that the magmatic sources are proximal to the shoreline deposits. The characteristics of microporosity, iron oxide inclusions, conchoidal fracture, heavy mineral grains, and opaque minerals support this proximal source. The conchoidal fractures defining the angularity of these beach sediments would suggest its derivation from crystalline rocks. The predominance of heavy minerals suggests that the rocks proximal to the beach have been altered. The abundance of primary minerals associated with these secondary heavy minerals justifies the existence of unweathered lithic grains in the source rocks and an alteration that occurred under a tropical monsoon climate that ranged from semi-humid to humid. The use of the multi-element tectonic discrimination diagram implies an arc framework that is compatible with the geology of the study area.

Novel Crushing Technique for Measuring δ18O and δ2H Values of Fluid Inclusions (H2O) in Quartz Mineral Veins Using Cavity Ring‐Down Spectroscopy

Fluid inclusions in mineralized fracture infillings (i.e., veins) could preserve information about subsurface fluids like temperature and salinity. The isotopic composition of water in these fluid inclusions could provide direct evidence of the provenance of these mineral‐forming fluids. So far, the isotope compositions of fluid inclusions have been mainly derived from carbonate veins and other precipitates, like speleothems. The aim of this study is to analyse the δ18O and δ2H isotopic compositions of aqueous fluid inclusions of quartz veins using a cavity ring‐down spectroscopy (CRDS) analyser in combination with a moisturized nitrogen background and mechanical crusher. For this study, we analysed δ18O and δ2H values of fluid inclusions in quartz veins from three north‐western European locations formed during the Variscan orogeny. Prior to crushing, the fluid‐rich quartz fraction was separated from the pure quartz fraction, from other mineral phases and host rock by using conventional heavy liquids and magnet separation. Raman spectrometry detected some rare occurrences of hydrocarbon, methane, and nitrogen in the fluid inclusions. The samples were sequentially crushed to elucidate the potential impact of different fluid inclusion assemblages (FIA) on the δ18O and δ2H values. The results from single and sequential mechanical crushing, together with interlaboratory comparisons, exhibit reliable and consistent isotopic patterns across locations with high precision (for δ18O: 1σ SD < 0.8‰; for δ2H: 1σ SD < 1.5‰). The obtained data occur in three different clusters for three study zones, providing evidence for the presence of meteoric‐derived fluids in the fold‐and‐thrust belts of the Variscan orogeny. These findings demonstrate that the CRDS approach can be successfully applied to quartz minerals, investigating fluid pathways within the upper crust and the formation of these secondary minerals.

Mineralogical characteristics and fluid inclusions of the Dashuixiabei crystalline graphite deposit in the Dunhuang block

AbstractGraphite is a strategic mineral resource of the world. The Dashuixiabei (DSXB) crystalline graphite deposit is located in the Dongbatu area in the Altyn crystalline graphite metallogenic belt. This study presents data from x‐ray diffraction (XRD), scanning electron microscopy (SEM), laser Raman spectroscopy, and fluid inclusions analysis conducted on the DSXB crystalline graphite deposit. The graphite is flake shaped, with a diameter of 0.1–0.4 mm. A group of extremely complete cleavage was observed under SEM, and the overall distribution was a flake. The C content in graphite is greater than 90 wt%, followed by N, O, and so on. The results of XRD analysis show that the lattice parameters of the DSXB crystalline graphite is a = 0.246–0.2465 nm, c = 0.6714–0.6715 nm, and V = 0.03519–0.03532 nm3. The degree of graphitization ranges from 0.8490 to 0.8519, indicating that the graphite crystal structure is relatively intact, the average metamorphic temperature is 552°C, and the content of 3R polytypes ranges from 13.16% to 13.25%. It is concluded that the metamorphic rocks of the DSXB crystalline graphite deposit have undergone medium‐grade metamorphism. The Raman spectral peaks show that DSXB crystalline graphite has a high degree of crystallinity. The DSXB crystalline graphite ore is dominated by hydrothermal fluids with medium‐low temperature and medium‐low salinity, and the vapor phase of the fluid inclusions is composed of CH4. There may be a superposition of the main and secondary mineralization stages. The crystalline graphite from the DSXB deposit shows high quality and stable ore quality, which has good metallogenic conditions and development and utilization prospects.

Eco-friendly hybrid binders based on waste from the chemical industry

The purpose of the study is to show the possibility of using high-tonnage waste from the chemical industry in the production of building materials. Methods and materials. Methods of data comparison and analysis were used. Solid residues of distiller sludge with a moisture content of 25-30%, an active calcium oxide content of 12-13% and quartz sand with a grain size of 2.2, humidity of 5-6% were used as materials. Results. Compositions and methods for obtaining a cement-free binder based on the solid residue of soda and quartz sand production are proposed. The possibility of obtaining a binder based on the solid residue of distiller slurries according to two technological schemes: drying of the solid residue and grinding together with quartz sand; firing of the solid residue and grinding together with quartz sand, has been confirmed by our tests. The introduced concept of “Eco-friendly hybrid cements” (Eco-friendly hybrid binders (EHB)) emphasizes that they are binders made up of multicomponent mineral raw materials of secondary resources. Practical significance. Solid by-products of the chemical industry can be used as an auxiliary inorganic component. This will make it possible to create eco-friendly hybrid cements ready for use, which are sealed only with water, which contributes to the development of such binders by industry and the rational use of secondary mineral resources.

Reasons for the low productivity of the Bashkirian stage oil deposits on the southwestern slope of the South Tatar arch

Oil deposits of the Bashkirian stage of low-amplitude uplifts on the southwestern slope of the South Tatar arch are considered. It has been established that in the sections of the Bashkirian stage, only the upper two oil deposits are potentially productive. The reservoir rocks are composed of leached packstone-grainstone. The oil productivity of the upper oil reservoir is determined by the intensity of leaching of carbonate rocks and the nature of oil saturation, while the lower one is determined by the degree of oxidation of oils and the manifestation of secondary mineralization. Oxidation of oil from the lower reservoir oil deposit is associated with the penetration of peripheral stratal water enriched with sulphate ions and magnesium ions. Deposition of diagenetic calcite, dolomite and gypsum-anhydrite aggregates in previously formed leaching caverns leads to a decrease in porosity and connectivity within reservoir layers. For low-amplitude uplifts, there is a tendency for oil productivity to decrease as the proportion of diagenetic mineralization increases.

FORMS OF FERRUM IN PROFILE-DIFFERENTIATED SOILS OF PRECARPATHIAN UKRAINE AND THEIR ROLE IN DIAGNOSTICS OF SOIL-FORMING PROCESSES

The profiles of sod-podzolic surface-gleyed soils (Stagnic Retisols) and brown podzolic soil profile (Neocambic Gleyic Retisols) are characterized by differentiation of gross Ferrum content and moderately low degree of Ferrum content. The composition of gross Ferrum is dominated by Fes, the maximum share of which is characteristic of A2B g horizon. The minimum content of Fes belongs to A1A2 g, which indicates the processes of destruction of primary and secondary minerals in the upper part of the profile. The accumulation of Ferrum oxides was diagnosed in the ortstein and nodules of the studied soils. The Schwertman coefficient in the neoplasms of the over-illuvial part of the profile is 0.6-0.7, which confirms the theory of their formation under the predominant action of the gleyish-eluvial process. The slight influence of modern gleiing process and their relict origin are observed in transition horizon.

Mechanism of Action and Validation of the Traditional Medicinal use of Grewia Tenax Fruits in Sudan to Encounter Iron Deficiency Anemia

Introduction: In Sudan, Grewia tenax fruits, are known commonly as Goddaim. The fruit’s pericarp is used traditionally for a long time as a juice or a porridge to treat iron deficiency anemia (IDA). Traditional Goddaim users have a very strong belief in its effectiveness. However, the pattern of hemoglobin improvement follows an initial fast increase followed by a decline upon continuing its use. Some previous studies have attributed its effect to high iron content, while the iron quantity was too small. This work attempts to find an explanation for its mechanism of action by screening the fruit extract and its respective fractions for secondary metabolites, minerals, vitamins, and fibre. Methods: Entailed three methodologies: Chemical analysis to identify quantified minerals, ascorbic acid and non-digestible fibers, Phytochemical Analysis to separate and identify secondary metabolites using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS-MS technique), and estimation of radical scavenging activities of crude fruit extract and its respective chloroform and ethyl acetate fractions by inhibition of the 2,2-diphenylpicrylhydrazyl (DPPH). Results: Ascorbic acid and indigestible fibres were revealed in the aqueous extract. Secondary metabolites were flavonoids (e.g., quercetin, kaempferol), organic acids (e.g., ferulic acid, chlorogenic acid), β-carboline alkaloids (e.g., 3-hydroxy-tetrahydroharman) identified in the chloroform, and ethyl acetate fractions. The in vitro antioxidant activity of G. tenax fruit extract was confirmed spectrophotometrically. Conclusion: It can be concluded that the initial enhancement of iron absorption through ascorbic acid and fibres, followed by iron uptake inhibition, could be explained by iron chelation by the chelators in the fruits. This paradoxical effect may qualify G. tenax fruits as a safety gauge for improving haemoglobin levels without compromising iron excess once iron stores are filled by keeping the oxidative stress in check. This may present G. tenax fruits as a good and safe remedy that optimizes the treatment of IDA.

Antimony(V) behavior during the Fe(II)-induced transformation of Sb(V)-bearing natural multicomponent secondary iron mineral under acidic conditions

Fe(II)-induced phase transformations of secondary iron minerals have attracted considerable attention due to their influence on antimony (Sb) mobility. However, Fe(II)-induced natural multicomponent secondary iron mineral (nmSIM) transformations and the corresponding repartitioning of Sb on nmSIM under acidic conditions upon Fe(II) exposure have not been systematically examined. Herein, we investigated the effect of Fe(II) on nmSIM mineralogy and Sb mobility in Sb(V)-bearing nmSIM at pH 3.8 and 5.6 at various Fe(II) concentrations over 15 d. The Sb(V)-bearing nmSIM phase transformation occurred under both strongly and weakly acidic conditions without Fe(II) exposure, while the presence of Fe(II) significantly intensified the transformation, and substantial amounts of intermediary minerals, including jarosite, ferrihydrite, lepidocrocite and fougerite, formed during the initial reaction stage, especially at pH 5.6. X-ray diffraction (XRD) analyses confirmed that goethite and hematite were the primary final-stage transformation products of Sb(V)-bearing nmSIM, regardless of Fe(II) exposure. Throughout the Sb(V)-bearing nmSIM transformation at pH 3.8, Sb release was inversely related to the Fe(II) concentration in the initial stage, and after maximum release was achieved, Sb was gradually repartitioned onto the nmSIM. No Sb repartitioning occurred in the absence of Fe(II) at pH 5.6, but the introduction of Fe(II) suppressed Sb release and improved Sb repartitioning on nmSIM. This transformation was conducive to Sb reimmobilization on Sb(V)-bearing nmSIM due to the structural incorporation of Sb into the highly crystalline goethite and hematite generated by the Sb(V)-bearing nmSIM transformation, and no reduction of Sb(V) occurred. These results imply that Fe(II) can trigger mineralogical changes in Sb(V)-bearing nmSIM and have important impacts on Sb partitioning under acidic conditions. These new insights are essential for assessing the mobility and availability of Sb in acid mine drainage areas.

Authigenic mineralization in Surtsey basaltic tuff deposits at 50 years after eruption

Alteration of basaltic glass and in situ mineral growth are fundamental processes that influence the chemical and material properties of Earth’s oceanic crust. These processes have evolved at the basaltic island of Surtsey (SW Iceland) since eruptions terminated in 1967. Here, subaerial and submarine lapilli tuff samples from a 192 m-deep borehole drilled in 2017 (SE-02b) are characterized through petrographic studies, X-ray powder diffraction analyses, and SEM–EDS imaging and chemical analyses. The integrated results reveal (i) multi-stage palagonitization processes in basaltic glass and precipitation of secondary minerals from matrix pore fluids, (ii) multi-stage crystallization of secondary phillipsite, analcime and Al-tobermorite in the vesicles of basaltic pyroclasts and (iii) variations in palagonitization processes as a function of thermal and hydrological domains. Although temperature appears to be an important factor in controlling rates of secondary mineralization, the chemistry of original basaltic components and interstitial fluids also influences reaction pathways in the young pyroclastic deposits. The integration of systematic mineralogical analyses of the 50-year-old tuff from one of the most carefully monitored volcanic sites on Earth, together with temperature monitoring in boreholes since 1980, provide a reference framework for evaluating mineralogical evolution in other Surtseyan-type volcanoes worldwide.

Multitechnique characterization of secondary minerals near HI-SEAS, Hawaii, as Martian subsurface analogues

Secondary minerals in lava tubes on Earth provide valuable insight into subsurface processes and the preservation of biosignatures on Mars. Inside lava tubes near the Hawaii-Space Exploration and Analog Simulation (HI-SEAS) habitat on the northeast flank of Mauna Loa, Hawaii, a variety of secondary deposits with distinct morphologies were observed consisting of mainly sodium sulphate powders, gypsum crystalline crusts, and small coralloid speleothems that comprise opal and calcite layers. These secondary deposits formed as a result of hydrological processes shortly after the formation and cooling of the lava tubes and are preserved over long periods of time in relatively dry conditions. The coralloid speleothem layers are likely related to wet and dry periods in which opal and calcite precipitates in cycles. Potential biosignatures seem to have been preserved in the form of porous stromatolite-like layers within the coralloid speleothems. Similar secondary deposits and lava tubes have been observed abundantly on the Martian surface suggesting similar formation mechanisms compared to this study. The origin of secondary minerals from tholeiitic basalts together with potential evidence for microbial processes make the lava tubes near HI-SEAS a relevant analog for Martian surface and subsurface environments.

Incongruent dissolution of silicates and its impact on the environment: an example of a talc mine

The paper analyzes the process of incongruent dissolution of silicates taking place in close proximity to a talc mine. The chemical and phase composition as well as the concentrations and mobility of potentially toxic elements (PTE) in research material with varying levels of weathering were determined using instrumental (XRF, XRD) and chemical methods (extractions: BCR, aqua regia, water leaching, 0.05 M EDTA). It was demonstrated that the predominant minerals in the weathering crust include weathering-resistant minerals (i.e. quartz and muscovite) and secondary minerals (kaolinite, illite and interstratified minerals, vermiculite/chlorite) and that the predominant processes are hydrolysis and oxidation. The weathering process has an impact on the complexity of the chemical and mineral composition and the diverse structure of the weathering crust. A layer of Fe and Al oxides and hydroxides forms in the upper part of the weathering crust, while the amount of silica decreases. Low-mobility elements (i.e. Si, Al and Fe) react on the phase separation surface, causing the formation of clay minerals (i.e. vermiculite, montmorillonite) or Al and Fe hydroxides (e.g. goethite). The duration of weathering causes an increase in the content of PTEs in solid materials: multifold in the case of Cr (15), Ba (9), Pb (7), Zn (6) and considerably lower in the case of V (1.3), Sr (0.8) and Co (0.4). It was demonstrated that PTEs co-occur in several chemical fractions in the weathering crust and that the highest share of their total concentration are cations incorporated in the crystal lattice of minerals and bound by strong crystalline bonds (F4 46%). The lowest share was observed for the reducible fraction (9%) and the share of the oxidizable fraction was 29% The most mobile cations connected by the weakest bonds comprised only 16% of the total concentration. Based on the content of the readily soluble fraction of PTEs, it was concluded that the degree of weathering does not increase the environmental risk, but actually reduces it for Cr, Cr and Pb. The obtained Ecological Risk Index (ERI) values indicate that the ecological risk associated with the elements tested is low for the entire area, which means that natural weathering processes do not have any impact on environmental pollution.

Nickel isotope fractionation during intense weathering of basalt: Implications for Ni output from continental weathering

Nickel isotope fractionation during continental weathering is not well constrained due to the limited research on Ni isotopes during weathering of mafic rocks such as basalt. This study investigated two weathering profiles (strongly and extremely weathered) derived on basalts in tropical China. The strongly weathered profile was dominated by kaolinite and divided into three layers with depth (soil, saprolite and rock). The extremely weathered profile was mainly composed of Fe- and Al-(oxyhydr)oxides and kaolinite, and included a special ferricrust layer, iron-rich duricrust with ferruginous nodules, between the soil and saprolite. We analysed the Ni speciation (e.g. Fe-oxide phases and residual phase) and isotopic composition of soil, ferricrust, saprolite, rock and water samples in the weathering profiles. Pore water and groundwater were collected underlying the extremely weathered profile, and the size-distribution of particulate Ni (1 kDa–450 nm) in water samples was analysed.Nickel in both profiles was mainly hosted in the residual phase (>71% of total Ni) which included primarily secondary silicates and Al-(oxyhydr)oxides. Weathering intensity controlled the mineral compositions and physico-chemical properties of the weathering profiles as well as Ni isotopic variations. Nickel redistribution (∼30%) and isotope fractionation (Δ60Niregolith-rock = −0.08‰ to 0.07‰) were slight in the strongly weathered profile due to the dominance of secondary silicates in Ni speciation. For the extremely weathered profile, significant Ni depletion (∼67%) and isotope fractionation (Δ60Niregolith-rock = −0.25‰ to 0.32‰) were related to the transformation of secondary silicates into Fe- and Al-(oxyhydr)oxides during lateritic weathering. The positive correlation of δ60Ni and Ni concentrations indicated that Ni isotope fractionation was controlled by Ni adsorption and incorporation of secondary minerals. In the lower saprolite, the calculated isotope fractionation between Ni remaining in the profile and leaching to the solution (Δ60Nisolid-solution = −0.47‰) indicated that Ni isotope fractionation was mainly controlled by the preferential adsorption of isotopically light Ni on Fe- and Al-(oxyhydr)oxides. However, in the soil and ferricrust, acidic pH (∼5.0) might reduce Δ60Nisolid-solution to −0.28‰ by releasing the isotopically light adsorbed Ni, leading to the predominance of incorporated Ni in Fe- and Al-(oxyhydr)oxides. Specifically, the highest δ60Ni value (0.27 ± 0.05‰) and Ni concentration in the upper saprolite indicated that the isotopically heavy Ni leached from the soil and ferricrust was scavenged by precipitating secondary silicates. Finally, the estimated isotopic composition of Ni leached from the extremely weathered profile (δ60Nioutput = 0.02 ± 0.15‰) was close to that of pore water (0.06 ± 0.01‰) where Ni was mainly present in the particulate phase. Compared with groundwater (δ60Ni = 0.33 ± 0.04‰) dominated by dissolved Ni, Ni output from the profile likely consisted of isotopically heavy dissolved Ni and light particulate Ni. Overall, this study provides a comprehensive understanding of Ni redistribution and speciation in basalt weathering profiles, highlighting the significance of weathering intensity in controlling Ni isotope fractionation and its implications for Ni outputs from continental weathering.

Different fates of Sb(III) and Sb(V) during the formation of jarosite mediated by Acidithiobacillus ferrooxidans

Secondary iron-sulfate minerals such as jarosite, which are easily formed in acid mine drainage, play an important role in controlling metal mobility. In this work, the typical iron-oxidizing bacterium Acidithiobacillus ferrooxidans ATCC 23270 was selected to synthesize jarosite in the presence of antimony ions, during which the solution behavior, synthetic product composition, and bacterial metabolism were studied. The results show that in the presence of Sb(V), Fe2+ was rapidly oxidized to Fe3+ by A. ferrooxidans and Sb(V) had no obvious effect on the biooxidation of Fe2+ under the current experimental conditions. The presence of Sb(III) inhibited bacterial growth and Fe2+ oxidation. For the group with Sb(III), products with amorphous phases were formed 72 hr later, which were mainly ferrous sulfate and pentavalent antimony oxide, and the amorphous precursor was finally transformed into a more stable crystal phase. For the group with Sb(V), the morphology and structure of jarosite were changed in comparison with those without Sb. The biomineralization process was accompanied by the removal of 94% Sb(V) to form jarosite containing the Fe-Sb-O complex. Comparative transcriptome analysis shows differential effects of Sb(III) and Sb(V) on bacterial metabolism. The expression levels of functional genes related to cell components were much more downregulated for the group with Sb(III) but much more regulated for that with Sb(V). Notably, cytochrome c and nitrogen fixation-relevant genes for the A.f_Fe2+_Sb(III) group were enhanced significantly, indicating their role in Sb(III) resistance. This study is of great value for the development of antimony pollution control and remediation technology.

Experimental timing of pyrite oxidation under various leaching conditions: consequences for rates of weathering in geological profiles

Pyrite (FeS2) is one of the most abundant sulfides on Earth and has already been studied in numerous ways for decades because of its rapid oxidation and the associated environmental impacts. This study proposes a new experimental physico-chemical approach (air, tridistilled water and water drip exposure) to determine the oxidation rate of pyrite using surface and depth data via XPS (X-ray Photoelectron Spectroscopy) analyses. Our experimental study of almost pure pyrite reveals a maximum oxidation rate of 11.7 ± 1.8 nm day−1 for drip exposure with precipitation of sulfates or Fe-oxides depending on the experimental condition. The oxidation rates obtained under various experimental conditions may be extrapolated to weathering rates of different zones of supergene profiles/ores (leached zone, saprolite and cementation zone). The extrapolation suggests a maximum rate of 4.3 ± 0.6 m Ma−1, which is consistent with data obtained by isotope dating of weathering profiles. Under geological conditions however, the oxidation rate of pyrite may be influenced by additional parameters, such as the nature of the host rock, its porosity/permeability, the climate, the influence of an oxidizing environment, and the mineralization of secondary minerals.

Nizkorazmernyy magnetizm v namibite Cu(BiO)2VO4OH

A synthetic analog of rare secondary mineral namibite Cu(BiO)2VO4OH has been obtained by the hydrothermal method. The crystal structure of this compound contains isolated uniform chains of vertex-connected copper–oxygen octahedra. Magnetic susceptibility (χ) and magnetization (M) measurements have not indicated the long-range order in the temperature interval 2–300 K. Specific heat (Cp) measurements suggest the formation of a spin-liquid state at low temperatures. X-band electron paramagnetic resonance data recorded at low temperatures have demonstrated only a signal from impurities. First-principles calculations have estimated the exchange interaction in the chains as J = 555 K, whereas exchange interactions between the chains turn out to be one to two orders of magnitude smaller. Thus, namibite represents a rare example of an unordered half-integer spin chain.

Exploring Greenockite: Occurrences and Geological Setting

Greenockite, mineral containing cadmium, is of significant scientific interest owing to its remarkable properties and potential applications in the field of science. It commonly forms in hydrothermal ore deposits as a secondary mineral due to complex cadmium-sulfur interactions influenced by temperature. Typically, it replaces zinc minerals like sphalerite, depending on the abundance of cadmium and zinc in hydrothermal fluids. Solid solubility in the ZnS CdS system occurs at high temperatures, with immiscibility observed under specific conditions. Greenockite forms at relatively low temperatures (100°C to 200°C) and is influenced by factors such as oxygen fugacity, hydrogen sulfide activity, and chloride ion content. Its hexagonal zinc blende structure results in diverse crystal forms, including rods, wires, and whiskers, often adorned with bismuth drops. Experimental studies have identified factors affecting its formation, such as solid solubility, precipitation mechanisms, pH levels, and fluid composition. Its vibrant coloration, attributed to cadmium concentration, varies from pale yellow to deep orange-red. Geologically, it is present in diverse settings, including metamorphosed zinc oxide mineralization, granites, fumaroles, pegmatites, and sediment-hosted Pb-Zn deposits, with a unique occurrence in gabbroic rock at the Babbitt deposit. In India, Greenockite has been identified in the Bagada orogenic gold prospect, situated within the Paleoproterozoic Mahakoshal belt, Central Indian Tectonic Zone (CITZ). Additionally, it is found in hydrothermal deposits of Pb-Zn mines of Zawar. It is exclusively encountered within specific geological settings, primarily as a secondary product. This paper provides a comprehensive exploration of its geological occurrences, distribution, associations, and exceptions.

Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation

Hydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in FeII (average ~5911 µmol/L) and SO4 (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subsequent precipitation of poorly crystallized Fe-oxyhydroxysulfate (schwertmannite) occurs and causes acidification (pH~2.8). However, the removal of dissolved loads as solid phases significantly improves the groundwater quality of the downgradient as an outflow. The rainwater isotopic values (δD ~−8.88‰ and δ18O ~−65.86‰) closely matched with the groundwater showing very little isotopic modification, which points to a short residence time of groundwater. The displacement of δD and δ18O values (slope = 5.3) from the meteoric water line reflected the evaporative enrichment of the lake water. The isotopic signature also revealed longer residence times of epilimnion than the hypolimnion waters which are dominated by groundwater. The lake is dimictic and showed abrupt changes in physicochemical parameters along the interface (~0.30 m thick) when separating the epilimnion (upper 4 m) from the hypolimnion (bottom 1.5 m). Lake sediments were found to be dominated by clay size fraction occurring as laminations (thickness: 1~0.5 mm) that reflect seasonal sedimentation. Higher schwertmannite formation in the south as compared to the north (recharge side) also serves as a scavenger of potentially toxic elements which is probably a natural solution to man-made problems. Schwertmannite transformation to goethite releases sulfate which is reduced and fixed as secondary sulfide minerals over time. Overall, waters are of a Ca–SO4 to Ca–Mg–SO4 type with distinct inflow (FeII/FeIII > 2.5) and outflow (FeII/FeIII < 0.5) of groundwater.