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1.
The minerals of the jarosite group, including the jarosite-beudantite-segnitite and jarosite-beaverite-osarizawaite isomorphic series, were studied with M?ssbauer spectroscopy. All the samples were collected from the oxidation zones of the South Urals sulfide deposits. In contrast to the jarosite containing one Fe3+ doublet in the M?ssbauer spectrum, the Pb-bearing members of the jarosite group—beudantite and beaverite—have two doublets in their spectra. Fe3+ is distributed at two sites with similar isomer shifts and different quadrupole splitting. The quantitative ratio of those doublets in the structure is roughly equal. The M?ssbauer spectra of the intermediate jarosite-beudantite and beaverite-osarizawaite members are superpositions of the jarosite and beudantite spectrum types with a prevalent jarosite doublet and larger quadrupole splitting. An admixture of antimony increases the Fe3+ content in the doublet with smaller quadrupole splitting. The unequal Fe3+ distribution in those two sites may be related to the ordering of cations in octahedrons. The appearance of two different Fe3+ sites probably resulted from the local coordinating role of Pb rather than from isomorphic replacement in anion groups.  相似文献   

2.
A representative collection of structurally characterized eudialyte-group minerals (EGM) with varying relative concentrations of Fe2+ and Fe3+ ions from several localities was investigated at room temperature by 57Fe Mössbauer spectroscopy coupled with magnetometric, optical, and X-ray powder diffraction methods. To refine the Mössbauer parameters of isomer shift and quadrupole splitting for Fe2+ and Fe3+ in different types of coordination polyhedra (planar quadrangle, square pyramid, and distorted octahedron) in EGM structures, we also collected Mössbauer parameters for gillespite and labuntsovite. The main purpose of this work is to determine the location of Fe3+ in different sites in typical eudialyte, rastsvetaevite, georgbarsanovite, and some of their naturally hydrated and heat-treated analogs, and investigate the kinetics and oxidation mechanisms of iron ions in their structures. Our study has confirmed the presence of Fe2+ ions in the planar quadrangle and square pyramid in primary eudialytes, as well as the presence of Fe3+ ions in the square pyramid and distorted octahedron in primary, naturally hydrated, and heat-treated eudialytes. According to this study, hydrated eudialytes are characterized by the location of Fe3+ ions mainly in octahedra with OH groups and/or water molecules at trans vertices, while heat-treated eudialytes are characterized by their location in square pyramids with an O2? anion at the apical vertex.  相似文献   

3.
The Jinbaoshan Pt–Pd deposit in Yunnan, SW China, is hosted in a wehrlite body, which is a member of the Permian (∼260 Ma) Emeishan Large Igneous Province (ELIP). The deposit is reported to contain one million tonnes of Pt–Pd ore grading 0.21% Ni and 0.16% Cu with 3.0 g/t (Pd + Pt). Platinum-group minerals (PGM) mostly are ∼10 μm in diameter, and are commonly Te-, Sn- and As-bearing, including moncheite (PtTe2), atokite (Pd3Sn), kotulskite (PdTe), sperrylite (PtAs2), irarsite (IrAsS), cooperite (PtS), sudburyite (PdSb), and Pt–Fe alloy. Primary rock-forming minerals are olivine and clinopyroxene, with clinopyroxene forming anhedral poikilitic crystals surrounding olivine. Primary chromite occurs either as euhedral grains enclosed within olivine or as an interstitial phase to the olivine. However, the intrusion has undergone extensive hydrothermal alteration. Most olivine grains have been altered to serpentine, and interstitial clinopyroxene is often altered to actinolite/tremolite and locally biotite. Interstitial chromite grains are either partially or totally replaced by secondary magnetite. Base-metal sulfides (BMS), such as pentlandite and chalcopyrite, are usually interstitial to the altered olivine. PGM are located with the BMS and are therefore also interstitial to the serpentinized olivine grains, occurring within altered interstitial clinopyroxene and chromite, or along the edges of these minerals, which predominantly altered to actinolite/tremolite, serpentine and magnetite. Hydrothermal fluids were responsible for the release of the platinum-group elements (PGE) from the BMS to precipitate the PGM at low temperature during pervasive alteration. A sequence of alteration of the PGM has been recognized. Initially moncheite and atokite have been corroded and recrystallized during the formation of actinolite/tremolite, and then, cooperite and moncheite were altered to Pt–Fe alloy where they are in contact with serpentine. Sudburyite occurs in veins indicating late Pd mobility. However, textural evidence shows that the PGM are still in close proximity to the BMS. They occur in PGE-rich layers located at specific igneous horizons in the intrusion, suggesting that PGE were originally magmatic concentrations that, within a PGE-rich horizon, crystallized with BMS late in the olivine/clinopyroxene crystallization sequence and have not been significantly transported during serpentinization and alteration.  相似文献   

4.
The chemical zoning profile in metamorphic minerals is often used to deduce the pressure–temperature (P–T) history of rock. However, it remains difficult to restore detailed paths from zoned minerals because thermobarometric evaluation of metamorphic conditions involves several uncertainties, including measurement errors and geological noise. We propose a new stochastic framework for estimating precise P–T paths from a chemical zoning structure using the Markov random field (MRF) model, which is a type of Bayesian stochastic method that is often applied to image analysis. The continuity of pressure and temperature during mineral growth is incorporated by Gaussian Markov chains as prior probabilities in order to apply the MRF model to the P–T path inversion. The most probable P–T path can be obtained by maximizing the posterior probability of the sequential set of P and T given the observed compositions of zoned minerals. Synthetic P–T inversion tests were conducted in order to investigate the effectiveness and validity of the proposed model from zoned Mg–Fe–Ca garnet in the divariant KNCFMASH system. In the present study, the steepest descent method was implemented in order to maximize the posterior probability using the Markov chain Monte Carlo algorithm. The proposed method successfully reproduced the detailed shape of the synthetic P–T path by eliminating appropriately the statistical compositional noises without operator’s subjectivity and prior knowledge. It was also used to simultaneously evaluate the uncertainty of pressure, temperature, and mineral compositions for all measurement points. The MRF method may have potential to deal with several geological uncertainties, which cause cumbersome systematic errors, by its Bayesian approach and flexible formalism, so that it comprises potentially powerful tools for various inverse problems in petrology.  相似文献   

5.
Two new varieties of sulfate minerals, zincobotryogen and zincocopiapite, belonging to the botryogen group and the copiapite group, respectively, were found in the oxidation zone of a lead-zinc deposit, situated on the northern border of the extremely arid Tsadam basin. – Authors.  相似文献   

6.
Models of geochemical controls on elements of concern (EOCs; e.g., As, Se, Mo, Ni) in U tailings are dominated by ferrihydrite. However, the evolution of aqueous concentrations of Al and Mg through the Key Lake (KL) U mill bulk neutralization process indicates that secondary Al and Mg minerals comprise a large portion of the tailings solids. X-ray diffraction, Al K-edge XAS, and TEM elemental mapping of solid samples collected from a pilot-scale continuous-flow synthetic raffinate neutralization system of the KL mill indicate the secondary Al–Mg minerals present include Mg–Al hydrotalcite, amorphous Al(OH)3, and an amorphous hydrobasaluminite-type phase. The ferrihydrite present contains Al and may be more accurately described as Al–Fe(OH)3. In the final combined tailings sample (pH 10.5) collected from the model experiments using raffinate with Al, Mg, and Fe, solid phase EOCs were associated with Al–Fe(OH)3 and Mg–Al hydrotalcite. In model experiments using raffinate devoid of Fe, aqueous EOC concentrations decreased greatly at pH 4.0 (i.e., where ferrihydrite would precipitate) and largely remained in the solid phase when increased to the terminal pH of 10.5; this suggests Al–Mg minerals can control aqueous concentrations of EOCs in the raffinate in the absence of Fe. Maximum adsorption capacities for individual and mixtures of adsorbates by Mg–Al hydrotalcite were determined. A revised model of the geochemical controls in U mill tailings is presented in which Al and Mg minerals co-exist with Fe minerals to control EOC concentrations.  相似文献   

7.
Adsorption of dissolved copper and phosphate by natural and peroxide-treated marine sediments was compared. A three-fold increase in copper adsorption and a six-fold increase in phosphate adsorption was caused by the peroxide treatment. Indigenous organic matter evidently interferes with adsorption.Clay minerals coated with heptadecanoic acid adsorbed somewhat less copper, phosphate, and hexadecane than uncoated clays, but slightly more nonadecanoic acid and anthracene.  相似文献   

8.
Mineralogy and Petrology - Tourmaline-supergroup minerals are common gangue minerals in Sb-hydrothermal veins on Betliar – Straková, Čučma – Gabriela and...  相似文献   

9.
《Applied Geochemistry》2001,16(1):85-93
An experimental study has been undertaken concerning the adsorption of radioelements on mixtures of minerals. The question is whether the adsorption of trace elements by rocks and soils can be easily predicted from the properties of the constituent minerals. The goal of these experiments was the comparison between the measurements of distribution coefficients of some radioelements for pure minerals and for binary mixtures according to the Doehlert’s uniform shell designs and to test an additive law of combination of Kd. The results showed that when one of the constituents acts as a dilutant in the mixture, i.e. it presents a very low adsorption capacity with respect to some trace element, then the relations of additivity of Kd are fulfilled. Otherwise, these relations are not satisfied and this is probably caused, in the present cases, by interactions from solubilized species.  相似文献   

10.
Aluminous, high-temperature clay minerals form from alteration of tholeiitic basaltic glass and calcic plagioclase during hydrothermal venting on the crest of the East Pacific Rise at 21°N. The clay alteration assemblages are layered crusts (up to 1 mm thick) completely replacing glass and calcic plagioclase adjacent to surfaces exposed to hydrothermal fluids. The interiors of the affected basalt samples have unaltered appearances and oxygen isotopic compositions just slightly heavier than that of MORB. The surficial alteration crusts are mixtures of beidellitic smectite (aluminous, dioctahedral), randomly interstratified mixed-layer Al-rich chlorite/smectite, minor chlorite, an x-ray amorphous aluminosilicate material, and possible minor serpentine (amesite). A δ18O value of +4.1 ± 0.2%. (SMOW) is determined for the beidellitic smectite. Assuming that this smectite equilibrated with hydrothermal fluid having an oxygen isotope value between that of seawater (0%.) and 350°C hydrothermal fluid from EPR, 21°N vents (+1.6%.), an equilibration temperature between 290°C and 360°C is calculated for the beidellitic smectite. This is substantially higher than any previously reported temperature for an oceanic smectite. The mixed-layer Al-rich chlorite/smectite has a δ18O value of +3.5%., which corresponds to equilibration at 295°–360°C. The aluminous composition of the alteration assemblage is uncommon for clay minerals produced by submarine hydrothermal basalt alteration. We suggest that this assemblage is largely the product of high-temperature interaction between basalt glass + plagioclase and Mg-poor, acidic hydrothermal fluids, with possibly some contribution of Mg from bottom seawater, and that the aluminous clays either incorporate Al3+ remobilized from basalt by lowpH hydrothermal fluids, or are residual phases remaining after intense alteration of basaltic glass + plagioclase.  相似文献   

11.
Summary A large number of podiform chromitite bodies of massive, disseminated and nodular type have been located in ultramafic units, composed of depleted mantle harzburgite and dunite of the Marmaris Peridotite from Ortaca (Mula, SW Turkey). The chromite ore bodies are surrounded by dunite envelopes of variable thickness, exhibiting transitional boundaries to harzburgite host rocks. Chromitites, containing a large number of inclusions, i.e. silicates, base metal sulphides and alloys, and platinum-group minerals (PGM) have a wide range of chemical composition. The Cr# [Cr/(Cr+Al)] values of most chromitites are high (0.61–0.81) and Mg# [Mg/(Mg+Fe2+)] values range between 0.65 and 0.71 with TiO2 content lower than 0.24wt.%, which may reflect the crystallization of chromites from boninitic magmas in supra-subduction setting environment.Platinum-group minerals (PGM) such as laurite, erlichmanite and Os–Ir alloys, silicates such as olivine, clinopyroxene and amphibole, and base metal sulphides (BM-S), alloys (BM-A) and arsenides (BM-As) are found as inclusions in chromite or in the serpentine matrix. Platinum-group element (PGE) concentrations of the Ortaca chromitites (OC) are low in all samples. Total PGE (Ir+Ru+Rh+Pt+Pd) ranges from 63ng/g to 266ng/g and Pd/Ir ratios range between 0.23 and 4.75. PGE content is higher and the Pd/Ir ratio lower in Cr-rich chromitites compared to Al-rich ones. There is a strong negative correlation between the Cr# and Pd/Ir ratios (r=–0.930). The PGE patterns show a negative slope from Ru to Pt and a positive slope from Pt to Pd. The low PGE content in the majority of the OC may reflect a lack of sulphur saturation during an early stage of their crystallization. The laurite compositions show a wide range of Ru–Os substitution caused by relatively low temperature and increasing f(S2) during the chromite crystallization. The high Cr# of and hydrous silicate mineral inclusions in chromite imply that chromite crystallized in a supra-subduction setting.  相似文献   

12.
Hypersthene-garnet-sillimanite-quartz enclaves were studied in orthopyroxene-plagioclase and orthopyroxene-clinopyroxene crystalline schists and gneisses from shear zones exposed in Palenyi Island in the Early Proterozoic Belomorian Mobile Belt. Qualitative analysis of mineral assemblages indicates that these rocks were metamorphosed to the granulite facies (approximately 900°C and 10–11 kbar). Oxygen isotopic composition was determined in rock-forming minerals composing zones of the enclaves of various mineralogical and chemical composition. The closure temperatures of the isotopic systems obtained by methods of oxygen isotopic thermometry are close to the values obtained with mineralogical geothermometers (Grt-Opx and Grt-Bt) and correspond to the high-temperature granulite facies (860–900°C). Identified systematic variations in the δ18O values were determined in the same minerals from zones of different mineral composition. Inasmuch as these zones are practically in contact with one another, these variations in δ18O cannot be explained by the primary isotopic heterogeneity of the protolith. The model calculations of the extent and trend of the δ18O variations in minerals suggest that the only mechanism able to generate the zoning was fluid-rock interaction at various integral fluid/rock ratios in discrete zones. This demonstrates that a focused fluid flux could occur in lower crustal shear zones. The preservation of high-temperature isotopic equilibria of minerals testifies that the episode of fluid activity at the peak of metamorphism was very brief.  相似文献   

13.
Potassium fertilizer is in short supply in China. However, there is a considerable resource of insoluble potassium resources in the soil mineral or potassium-baring low-degrade rocks. Most of these kinds of potassium exist in aluminous silicate minerals from which potassium cannot be absorbed directly by plants. So it is very important to study how to release potassium from soil minerals or rocks by using biological action. Recently, a large number of researches on degradation of potassic mineral by bacterial but few by fungi have been reported. In order to study the degradation of potassic mineral by fungi, we isolated a strain of thermophilic fungi TH003, which can use potassic rock as nutrient source. The strain was identified as Aspergillus fumigatus based on its morphological characters and molecular biology. In this paper, the direct and indirect processes of mineral powder degradation with the strain of TH003 were studied： mineral powder was added in medium directly for cultivation so as to investigate the direct process. For the purpose of studying indirect process, mineral powder was wrapped up in a parcel using membrane with pore size of 0.22 μm, and then the parcels were added in the medium. The interaction between mineral granules and mycelia was observed by using TEM and AFM at different stages during the whole experimental procedure. The results showed that the effect of direct process is stronger than that of indirect process. For instance, the content of K^＋ is higher in both culture media and mycelia. Direct process includes mechanical demolishment, adsorption, parceling, phagocytosis, erosion and comprehensive effect, while indirect process only refers to erosion on the surface of mineral granules by metabolic products of mycelia. The technology of fermentation engineering was employed to study the biological effects of the strain of Aspergillus fumigatus TH003 on the minerals bating low-grade potassium. Nutrition factors and culture conditions that affect the process of mineral powder degrading with the strain of TH003 were studied in this paper. The results showed that glucose and corn steep are the optimal carbon and nitrogen resources in the strain culture medium, and that pH values range from 3.0 to 9.0.  相似文献   

14.
In the Noril’sk ore field, parkerite is a characteristic mineral of sulfide ore that metamorphosed under conditions of zeolite and prehnite-pumpellyite facies and of arsenide-calcite veins. The mineral occurs in ores containing bornite, anhydrite, magnetite, mackinawite (3–5 wt % Ni), valleriite, calcite, ankerite, native silver, native bismuth, violarite, Te-rich bismutohauchecornite, cupropentlandite enriched in Fe, Pd-rich breithauptite (1.5–2.5 wt % Pd), galena enriched in Cu (3.8 wt % Cu), and Ni arsenides and antimonides. Parkerite occurs in those place, where the primary ores have contained pockets and veins of graphic galena and chalcopyrite aggregates with associated Pt-Pd-Au-Ag minerals. Parkerite metacrysts in galena and Fe-Cu-Ni sulfides contain 6–16 and up to 5 wt % Pb, respectively. Parkerite rims replacing PGM aggregates and galena contain 1–3 wt % Pb. In calcite veins hosted in metamorphosed sulfide ores, parkerite is associated with native silver and bismuth, maucherite, cobaltite, chalcocite, and uraninite. Parkerite from these veins contains up to 0.5 wt % Pb. Thus, the Pb and Bi contents in parkerite basically depend on those of replaced minerals. Rare bismutohauchecornite is associated with parkerite.  相似文献   

15.
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16.
The creep property of rock under cyclic loading is very important in civil engineering. In order to establish a novel constitutive equation for rock under cyclic loading, a fractional-order viscoplastic body under cyclic loading was constructed based on fractional-order viscous element. A fractional-order visco-elastoplastic model (FVEPM) for rock was established by connecting constructed fractional-order viscoplastic body with Burgers model. The model was a Burgers model when the maximum value of cyclic loading was less than the critical strength of rock; otherwise, it was a FVEPM which can be used to reflect the transient, steady-state, and tertiary creep phases of rock. The cyclic loading was decomposed into a static load and a cyclic loading with a zero average stress. According to rheological mechanics theory, the rheology constitutive equation of rock under the static load can be derived. According to viscoelastic mechanics theory, the constitutive equation under cyclic loading with a zero average stress was established by introducing the variation parameters of energy storage and energy dissipation compliance caused by rock damage and fracture. Finally, a new dynamic constitutive equation of rock cyclic loading can be obtained by superimposing the constitutive equation under static load and cyclic loading with a zero average stress. Compared with existing test results of rock under cyclic loading, the proposed constitutive model can be used to describe the creep characteristics of rock under cyclic loading and reflect the presented fluctuation of strain curve of rock under cyclic loading.  相似文献   

17.
Mineralogical studies of the heavy fraction from a Holocene pyrope-rich garnet placer deposit at Vestřev (Krkonoše Piedmont Basin, Bohemian Massif) have identified the presence of very rare grains of platinum group minerals (PGM). Pt–Fe alloy grains are accompanied by Os–Ir–Ru minerals (native osmium, iridium, and ruthenium) with inclusions of Pt–Fe alloy and hongshiite (PtCu). This mineral assemblage is typical for several mantle settings including ophiolites. The chemistry of the Os–Ir–Ru minerals shows an enrichment of the PGM in Ru, which is typical of ophiolites. The grain morphology of PGM and pyrope-rich garnet (mostly rounded with numerous euhedral/subhedral grains) does not exclude a common source. In-situ laser-ablation MC-ICP-MS was used to measure the Re–Os isotopic compositions of single Os-rich grains, which show heterogeneous subchondritic Os isotopic compositions (187Os/188Os = 0.12082–0.12505 ± 0.00003). This precludes their low-temperature origin and indicates derivation of platinum-group elements (PGEs) essentially from mantle-derived rocks without a significant contribution of crustal Os. The mantle model age (TMA) and Re-depletion model age (TRD) model ages range from ~ 0.4 to ~ 1.0 Ga and most likely reflect a long history of melt depletion that affected the mantle sources of PGM.  相似文献   

18.
Potassium fertilizer is in short supply in China. However, there is a considerable resource of insoluble potassium resources in the soil mineral or potassium-baring low-degrade rocks. Most of these kinds of potassium exist in aluminous silicate minerals f…  相似文献   

19.
In terms of environmental mineralogy, the environmental properties of metallic minerals, including chemical activation, adsorption, pore effect and nanometer effect, have been analyzed. On the basis of the analysis of environmental properties of metallic minerals, the applications of iron-bearing sultides, iron and manganese oxides in the purification of wastewaters containing heavy metal ions （Cr^6＋ ,Hg^2＋ , Pb^2＋ , etc. ） have been summarized. Moreover, research on the application of metallic minerals in environmental protection has been anticipated. It should be a piece of dominating work for environmental mineralogie researchers in the future to lucubrate systematically the physical and chemical characteristics of the metallic mineral surfaces, further reveal the reciprocity process between metallic minerals and water surface, perfect the theory and model of the metallic minerals to remove contaminants, intensify study on the facilities and techniques of metallic minerals to remove contaminants, and entail well the extension and propagation of achievements.  相似文献   

20.
This paper reviews the history of the foundation of the Commission on New Minerals in Russia (1956) and the same Commission of the International Mineral Association (IMA). The terms mineral species, subspecies, and variety are considered. The nomenclature of mineral groups of lovozerite, eudialyte, and apatite is given as examples of using a root name and its suffixes.  相似文献   

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