Sample records for chromites

  1. Geophysical Hunt for Chromite in Ophiolite

    Directory of Open Access Journals (Sweden)

    Mubarik Ali


    Full Text Available Ophiolite of Oman are famous world over, and are favorite for exploring chromite, which is a source of chromium that is used widely in steel, nichrome, and plating and painting industries. The best known chromite deposits are found in the Bushveld complex of South africa, however countries like Pakistan and Oman are also contributing but less than 2% of the world production. Chromite is found in the mantle rocks such as peridotite and its altered products. Large economic deposits are generally found in stratiform structure and the smaller ones in pod-like or tabular lenses. In Oman the chromite deposits occur in Oman ophiolite (Semile, mainly in the mantle sequence comprising harzburgite and dunite. The mining efforts for chromite in Oman are in progress but not on scientific grounds. On a site called Izki (670 m asl the chromite was expected on the top of a hill in a small area (150x50 m of ophiolite, and mining through pitting procedure was tried over there but remained unsuccessful. Geophysical methods were applied in the same area to search out the possibility of the existence of the ore. Since chromite is denser, more conductive and magnetically less susceptible deposit as compared to the host rocks harzburgite and serpentinite, it is expected that the existence of a shallow sizable ore body would generate favorable gravity, magnetic, and resistivity signals. The integrated geophysical study (gravity, magnetic and resistivity reveals the probability of chromite within 30 m depth. For confirmation the drilling was recommended on a point upto a depth of 35 meters. The drilling could not be continued beyond 12 meters depth due to reasons known to the lease owner. The drilling showed harzburgite up to 8 meters depth, then a chromite layer of 0.7 meter thickness, after that harzburgite started for the next 3 meters depth. This state of affairs confirms not only the presence of chromite but also the revealing power of geophysics.


    Institute of Scientific and Technical Information of China (English)

    S.L. Zheng; Y. Zhang


    A new method for chromate cleaning production named chromite caustic fusion pro-cess, is advanced by Institute of Chemical Metallurgy, the Chinese Academy of Sci-ences. With sodium hydroxide as reaction medium, the new process is composed ofthree procedures: liquid phase oxidation of chromite - metastable phase separation -carbonation ammonium transition. Generally illustrating the new process and its fea-tures, this paper mainly studies the thermodynamics of chromite oxidation. The newprocess has much better practical results than the conventional chromate productionprocess in which sodium carbonate is used as reaction medium. The superiority is alsoshown through thermodynamic studies.``

  3. Chromite Enrichment in the Recent Fluviatile Sediments, North Iraq


    Al Juboury, Ali I. [علي الجبوري; Ismail, Sabah A.; Ghazal, Mohsin M.


    The Recent sediments from North Iraq are characterized by a higher content of chromite. This paper deals with the mineralogy and geochemistry of chromite in the heavy mineral assemblages from Recent fluvial sediments in an attempt to elucidate its distribution and source rock. The heavy fraction is composed of iron oxides and chromite forming about 50% of the total heavies. Chromite forms up to 80% of the opaque minerals at some areas in North Iraq. The non-opaque heavy minerals are composed ...

  4. Mechanical properties of lanthanum and yttrium chromites

    Energy Technology Data Exchange (ETDEWEB)

    Paulik, S.W.; Armstrong, T.R. [Pacific Northwest National Lab., Richland, WA (United States)


    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  5. Reduction Mechanism of Chromite Ore in Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    LI Yi-wei; DING Wei-zhong; LU Xiong-gang; XU Kuang-di


    The structural changes and reduction degree of chromite ore in blast furnace were studied by optical micrograph analysis, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDXA). The smelting reduction mechanism of chromite in blast furnace was primarily discussed.

  6. Carbothermal reduction kinetics of mechanically activated chromite with graphite


    Kenan Yıldız


    The carbothermal reduction kinetics of mechanically activated chromite with graphite under an argon atmosphere was investigated at temperatures between 1100 and 1400°C. Zhuravlev-Lesokhin-Tempelman (ZLT) method was used in the reduction kinetics for non-activated chromite and the activation energy was calculated as 401.7 kJ/mol. Solid-state diffusion method was used in the reduction kinetics for 60 min-activated chromite and the activation energy was calculated as 283.3 kJ/mol. This decrease ...

  7. Placer chromite along south Maharashtra, central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gujar, A.R.; Ambre, N.V.; Iyer, S.D.; Mislankar, P.G.; Loveson, V.J.

    1 National Institute of Oceanography (CSIR), Dona Paula, Goa 403 004, India 2 Beach Placer Mining Department, Central Institute of Mining and Fuel Research (CSIR), Dhanbad 826 015, India We describe here the onshore occurrence of placer chromite... textural features and the chemistry, a few chromite grains were studied under the scanning electron microscope (SEM, JEOL JSM-5800) coupled with an Energy Disper- sive System (EDS LINK). The surficial textural features were then identified following...

  8. Occupational health assessment of chromite toxicity among Indian miners

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    Alok Prasad Das


    Full Text Available Elevated concentration of hexavalent chromium pollution and contamination has contributed a major health hazard affecting more than 2 lakh mine workers and inhabitants residing in the Sukinda chromite mine of Odisha, India. Despite people suffering from several forms of ill health, physical and mental deformities, constant exposure to toxic wastes and chronic diseases as a result of chromite mining, there is a tragic gap in the availability of ′scientific′ studies and data on the health hazards of mining in India. Occupational Safety and Health Administration, Odisha State Pollution Control Board and the Odisha Voluntary Health Association data were used to compile the possible occupational health hazards, hexavalent chromium exposure and diseases among Sukinda chromite mines workers. Studies were reviewed to determine the routes of exposure and possible mechanism of chromium induced carcinogenicity among the workers. Our studies suggest all forms of hexavalent chromium are regarded as carcinogenic to workers however the most important routes of occupational exposure to Cr (VI are inhalation and dermal contact. This review article outlines the physical, chemical, biological and psychosocial occupational health hazards of chromite mining and associated metallurgical processes to monitor the mining environment as well as the miners exposed to these toxicants to foster a safe work environment. The authors anticipate that the outcome of this manuscript will have an impact on Indian chromite mining industry that will subsequently bring about improvements in work conditions, develop intervention experiments in occupational health and safety programs.

  9. Sulfuric acid leaching kinetics of South African chromite

    Institute of Scientific and Technical Information of China (English)

    Qing Zhao; Cheng-jun Liu; Pei-yang Shi; Bo Zhang; Mao-fa Jiang; Qing-song Zhang; Ron Zevenhoven; Henrik Saxn


    The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching con-ditions. The dimensionless change in specific surface area and the conversion rate of the chromite were observed to exhibit a proportional re-lationship. A modified shrinking particle model was developed to account for the change in reactive surface area, and the model was fitted to experimental data. The resulting model was observed to describe experimental findings very well. Kinetics analysis revealed that the leach-ing process is controlled by a chemical reaction under the employed experimental conditions and the activation energy of the reaction is 48 kJ·mol–1.

  10. Melting of Pre-Reduced Chromite Pellet Bearing Carbon

    Institute of Scientific and Technical Information of China (English)

    ZHANG You-ping; XUE Zheng-liang; LI Zheng-bang; ZHANG Jia-wen; YANG Hai-sen; ZHOU Yu-sheng


    As the raw material for hot metal containing chromium from 20% to 40%, carbon-beared chromite pellets made from three kinds of typical chromite were reduced at 1 300 ℃ for 30 min and then kept at 1 550-1 600℃ for 10 min. The effect of Cr2 O3/FeO mass ratio in pellets on chromium content in hot metal and the yield of chromium were investigated. The results indicated that the highest chromium content is in hot metal produced from South African UG2 ore, but slag volume produced with Indian chromite is the smallest. The yield of chromium is only 60% to 75%, due to short melting time, high melting point and large surface tension of the slag with high Al2 O3 and MgO content, which influences the separation between metal and slag.

  11. Speciation and recovery of chromium from chromite ore processing residues. (United States)

    Sreeram, K J; Ramasami, T


    The processing of chromite ore is associated with the generation of large quantities of solid wastes containing chromium, which have been disposed of as landfill for many years. The mobilization and operational speciation of chromium contained in soils contaminated with metal salts are important in terms of the environment. Several methods have been employed for the extraction and recovery of solid wastes. Chromium contained in contaminated soils and solid wastes can be categorized as exchangeable, oxidizable, carbonate-bound, reducible and residual. The results from this study indicate a need for efficient leaching methodologies in chromite ore processing plants to decrease the non-detrital fractions of chromium in the residue. Aggressive methodologies are required to recover chromium from the detrital fractions. The potential benefits of employing sodium peroxide for the complete recovery of chromium from chromite residue have been demonstrated, and the need to ensure the safety of the process has been emphasized.

  12. Impact assessment of chromite mining on groundwater through simulation modeling study in Sukinda chromite mining area, Orissa, India. (United States)

    Dhakate, Ratnakar; Singh, V S; Hodlur, G K


    The pre-Cambrian chromites ore deposits in Sukinda valley, Jajpur District, Orissa, India, are well known for chromite ore deposits. The exploitation of the ore is carried out through open cast mining method since the last few decades. In the process, the overburden and ore dumps are stored on ground surface, where leaching of chromite and other toxic element takes place particularly during monsoon seasons. This leachate may cause threat to groundwater in the vicinity. An integrated approach has been adopted to evaluate possibility of pollution due to mine seepage and leachate migration on groundwater regime. The approach involves geophysical, hydrogeological, hydro-chemical and aquifer modeling studies. The investigation has the significance as many habitats surround the mining area facing groundwater problems.

  13. Stratiform chromite deposit model: Chapter E in Mineral deposit models for resource assessment (United States)

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II


    A new descriptive stratiform chromite deposit model was prepared which will provide a framework for understanding the characteristics of stratiform chromite deposits worldwide. Previous stratiform chromite deposit models developed by the U.S. Geological Survey (USGS) have been referred to as Bushveld chromium, because the Bushveld Complex in South Africa is the only stratified, mafic-ultramafic intrusion presently mined for chromite and is the most intensely researched. As part of the on-going effort by the USGS Mineral Resources Program to update existing deposit models for the upcoming national mineral resource assessment, this revised stratiform chromite deposit model includes new data on the geological, mineralogical, geophysical, and geochemical attributes of stratiform chromite deposits worldwide. This model will be a valuable tool in future chromite resource and environmental assessments and supplement previously published models used for mineral resource evaluation.

  14. SEM, optical, and Moessbauer studies of submicrometer chromite in Allende (United States)

    Housley, R. M.


    New scanning electron and optical microscope results are presented showing that sub-micrometer chromite is abundant along healed cracks and grain boundaries in Allende chondrule olivine. Some wider healed cracks also contain pentlandite and euhedral Ni3Fe grains. Also reported are Moessbauer measurements on Allende HF-HCl residues confirming a high Fe(+++)/Fe(++) ratio.

  15. Advances towards a Clean Hydrometallurgical Process for Chromite

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    Bo Zhang


    Full Text Available Because of the acute toxicity of Cr(VI-bearing substances, the pollution problem caused by chromite process residue has become a worldwide concern. In the view of relevant studies, the technologies based on the alkali treatment cannot fundamentally resolve the pollution problem, because the oxidation of Cr(III to Cr(VI is unavoidable during chromite decomposition. In contrast, the oxidation of Cr(III to Cr(VI can be controlled by the sulfuric acid treatment of chromite, and the Cr(VI pollution can be eliminated from the original source of production. Many research studies focusing on the resolutions of the key obstacles hindering the development of the sulfuric acid treatment process have been carried out, and significant progress has been achieved. In this study, a clean hydrometallurgical process without the generation of hexavalent chromium is demonstrated. First, the chromite was decomposed and leached by sulfuric acid solution in the presence of an oxidant. Then, iron was hydrothermally removed from the acid solution as the precipitate of jarosite. Finally, chromium salts were obtained by adjusting the basicity of the solution, separation and drying. With the aim of realizing industrialization, future research emphasis on the development of the sulfuric acid treatment process is proposed in this study.

  16. Applications and Preparation Methods of Copper Chromite Catalysts: A Review

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    Ram Prasad


    Full Text Available In this review article various applications and preparation methods of copper chromite catalysts have been discussed. While discussing it is concluded that copper chromite is a versatile catalyst which not only catalyses numerous processes of commercial importance and national program related to defence and space research but also finds applications in the most concerned problem worldwide i.e. environmental pollution control. Several other very useful applications of copper chromite catalysts are in production of clean energy, drugs and agro chemicals, etc. Various preparation methods about 15 have been discussed which depicts clear idea about the dependence of catalytic activity and selectivity on way of preparation of catalyst. In view of the globally increasing interest towards copper chromite catalysis, reexamination on the important applications of such catalysts and their useful preparation methods is thus the need of the time. This review paper encloses 369 references including a well-conceivable tabulation of the newer state of the art. Copyright © 2011 by BCREC UNDIP. All rights reserved.(Received: 19th March 2011, Revised: 03rd May 2011, Accepted: 23rd May 2011[How to Cite: R. Prasad, and P. Singh. (2011. Applications and Preparation Methods of Copper Chromite Catalysts: A Review. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 63-113. doi:10.9767/bcrec.6.2.829.63-113][How to Link / DOI: || or local: ] | View in 

  17. Geological and Mineralogical-technological features chromite ore from nickel-weathering crusts Average Bug

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    Perkov E.S.


    Full Text Available Conditions of occurrence and distribution features of chromites ore bodies in the ultra-basic nickel bearing weathering crusts of Middle Bug Area are considered. Main types of exogenous chromites ores in weathering crusts and beyond of them are identified as well as mineralogical, chemical and grain features of mineralization are given. Obtained data are substantiated in order to apply them while developing the efficient schemes of mining and processing of exogenous chromites ores.

  18. Brief report on thermodynamics of chromium slags and kinetic modelling of chromite reduction (1995-96)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Yamping; Holappa, L. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Metallurgy


    This article summaries the research work on thermodynamics of chromium slags and kinetic modelling of chromite reduction. The thermodynamic properties of FeCr slag systems were calculated with the regular solution model. The effects of CaO/MgO ratio, Al{sub 2}0{sub 3} amount as well as the slag basicity on the activities of chromium oxides and the oxidation state of chromium were examined. The calculated results were compared to the experimental data in the literature. In the kinetic modelling of the chromite reduction, the reduction possibilities and tendencies of the chromite constitutes with CO were analysed based on the thermodynamic calculation. Two reaction models, a structural grain model and a multi-layers reaction model, were constructed and applied to simulate the chromite pellet reduction and chromite lumpy ore reduction, respectively. The calculated reduction rates were compared with the experimental measurements and the reaction mechanisms were discussed. (orig.) SULA 2 Research Programme; 4 refs.

  19. Optics of Chromites and Charge-Transfer Transitions

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    Andrei V. Zenkov


    Full Text Available Specific features of the charge-transfer (CT states and O2p→Cr3d transitions in the octahedral (CrO69− complex are considered in the cluster approach. The reduced matrix elements of the electric-dipole transition operator are calculated on many-electron wave functions of the complex corresponding to the initial and final states of a CT transition. Modeling the optic spectrum of chromites has yielded a complicated CT band. The model spectrum is in satisfactory agreement with experimental data which demonstrates the limited validity of the generally accepted concept of a simple structure of CT spectra.

  20. Electron microscopy of microwave-synthesized rare-earth chromites


    Schmidt, Rainer; Prado-Gonjal, Jesus; Avila, David; Amador, Ulises; Moran, Emilio


    The perovskite rare-earth (RE) chromite series (RE)CrO3 (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu) has been synthesized in our laboratory using microwave techniques. In this work we will demonstrate how X-ray diffraction (XRD), Rietveld refinement of XRD pattern and complementary High Resolution Transmission Electron Microscopy (HRTEM) were used to confirm that the desired crystal structure had been formed. Field-emission scanning electron microscopy (FE-SEM) gave clear ...

  1. Synthesis and Characterization of Hydrophilic and Semiconductor Cadmium Chromite Nanostructures (United States)

    Mousavi, Zahra; Salavati-Niasari, Masoud; Soofivand, Faezeh; Esmaeili-Zare, Mahdiyeh; Hamadanian, Masood


    Cadmium chromite nanostructures were synthesized in high yield by a simple co-precipitation method. CdCr2O4 nanostructures have been achieved using cadmium nitrate tetrahydrate and CrCl3·6H2O as precursors by a co-precipitation method. The effects of various parameters including alkaline agent, pH value, reaction temperature, and surfactant type were investigated to discover the optimum conditions, and it was found that the size and morphology of products can be affected by these parameters. The structure, morphology and surface chemistry of CdCr2O4 powder were investigated by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. X-ray diffraction patterns indicated the chromite spinel phase with good crystallinity and an average crystallite size of approximately 20 nm. The hydrophilicity of the calcined oxides was investigated by wetting experiments and the sessile drop technique which were carried out at room temperature in air to determine the surface and interfacial interactions.


    Energy Technology Data Exchange (ETDEWEB)

    Ms. Xiaolei Sun; Professor George W. Roberts


    Work during the report period was concentrated on developing analytical techniques. Thin-layer chromatography (TLC) was used in an attempt to define the best mobile phase to separate the components of ''spent'' tetrahydroquinoline by liquid chromatography in a silica gel column. Conditions have been defined for separating the light gases produced by the reaction of carbon monoxide (CO) and hydrogen (H{sub 2}) over promoted ''zinc chromite'' catalysts. This will be done with a temperature-programmed Carboxen-1000 column, using a thermal conductivity detector for analysis. A Petrocol DM 150 capillary column will be purchased to separate the heavier products, which will be analyzed using a flame ionization detector.

  3. Borohydride electro-oxidation by Ag-doped lanthanum chromites

    Indian Academy of Sciences (India)

    S Suresh Balaji; A Usha; V V Giridhar


    The electrocatalytic activity of Ag-doped lanthanum chromites electrode materials viz., LaCr0.4Ag0.6O3 and LaCr0.7Ag0.3O3 prepared by decomposing the precursor complex is studied. Pure LaCrO3 is synthesized by combustion route using oxalic acid as a fuel. The decomposition behaviour of the assynthesized powder obtained in the latter method is characterized by TGA-DTA and XRD. Both the precursor complex and the as-synthesized powder are calcined at 900°C for 7 and 10 h, respectively. XRD of the final product after calcinations indicated the formation of perovskite phase with minor amounts of impurity phases of component oxides in the Ag-doped lanthanum chromites and pure perovskite phase in the undoped one. The surface morphology of the perovskites is studied by SEM. The electrocatalytic activity of the perovskite powders for borohydride oxidation is studied by using cyclic voltammetry (CV) at a catalyst loading of 0.7 mgcm−2 for both Ag-doped and undoped LaCrO3 coated on glassy carbon substrate. Calibration plots are obtained by plotting the anodic peak current versus concentration of borohydride in the range of 20-100 mM. The sensitivities of the three perovskites towards borohydride oxidation indicated that LaCr0.4Ag0.6O3 is the best among all the perovskites studied giving a value of 1.395 A/mM.

  4. Lanthanum chromite colloidal processing; Processamento coloidal de cromito de lantanio

    Energy Technology Data Exchange (ETDEWEB)

    Setz, Luiz Fernando Grespan


    Lanthanum chromite (LaCrO{sub 3}) is currently the most studied material for applications such as solid oxide fuel cell inter connector (HTSOFC). The complexity of microstructures and geometries of HTSOFC devices, require a precise control of processing parameters to get the desired combination of properties and this, the use of techniques involving concentrated ceramic slips conformation are appropriate, therefore, is well controlled, assist in obtaining homogeneous parts, reproductive and complex geometries. Thus, studies involving the surface chemistry, the stability conditions and slips flow behaviour in the forming conditions, provide important elements for processes control in the inter connectors manufacture, where more applied settings have slots and channels for the gases passage. Thus, surface chemistry, stability and rheological behaviour of strontium and cobalt doped LaCrO{sub 3} (La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3}) slips prepared with ethanol and water, were studied. The doped lanthanum chromite was produced by combustion synthesis in the IPEN/SP labs. The influence of parameters: p H (water), dispersant concentration, homogenization times and conditions, solid concentration, different ratios binder:plasticizer in the stability and the flow behavior of ceramic suspensions prepared were evaluated. The La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} products obtained by casting aqueous slips in a plaster mould, using alkaline p H and anionic polyelectrolyte and tapes obtained by using ethanol as a dispersant medium, after sintering at 1600 deg C/4h presented theoretical density > 94%, suitable for use as HTSOFC inter connector. (author)

  5. [Qualitative and quantitative analysis of various elements in chromite ore by ICP-AES]. (United States)

    Zhang, Yang; Zheng, Shi-li; Wang, Xiao-hui; Xu, Hong-bin; Zhang, Yi


    Kind of the elements in chromite ore was firstly determined by ICP-AES. Twenty nine elements, such as Cr, Fe, Al, Mg, Zn, Ca and Ni, were contained in the chromite sample based on the qualitative analysis. Then the contents of main elements Cr, Fe, Al, Mg, Ca, T, Si, Mn and V were measured. The chromite samples processing procedures have two steps, the first is decomposition by nitrate carbonate and sodium tetraborate at 950 degrees C for 30 min, then leaching by dilute hydrochloric acid at 80 degrees C for 10 min. The method showed satisfactory precision and accuracy with the RSDs between 0.48% and 2.05% and the recovery rates between 90.5% and 111.3%.

  6. Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

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    Federica Zaccarini


    Full Text Available Several chromite deposits located in the in the South and Southeast Arms of Sulawesi, Indonesia, have been investigated by electron microprobe. According to the variation of the Cr# = Cr/(Cr + Fe3+, the chromite composition varies from Cr-rich to Al-rich. Small platinum-group minerals (PGM, 1–10 μm in size, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with chlorite along cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with amphibole, chlorite, Co-pentlandite and apatite. Small blebs of irarsite (less than 2 μm across have been found associated with grains of awaruite and Co-pentlandite in the chlorite gangue of the chromitites. Grains of olivine, occurring in the silicate matrix or included in fresh chromite, have been analyzed. They show a composition typical of mantle-hosted olivine. The bimodal composition and the slight enrichment in TiO2 observed in some chromitites suggest a vertical zonation due to the fractionation of a single batch magma with an initial boninitic composition during its ascent, in a supra-subduction zone. This observation implies the accumulation of Cr-rich chromitites at deep mantle levels and the formation of the Al-rich chromitites close or above the Moho-transition zone. All of the laurites are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperature of around 1200 °C and a sulfur fugacity below the sulfur saturation. Irarsite possibly represents a low temperature, less than 400 °C, exsolution product.

  7. Compositional variations in the Mesoarchean chromites of the Nuggihalli schist belt, Western Dharwar Craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir Kanti; Rosing, Minik Thorleif


    -98)) and pyroxene grains (Mg-numbers = 97-99). Compositional variability on the scale of a single chromite grain occurs in the form of zoning, and it is common in the accessory chromite grains in serpentinite and in the altered grains in chromitite. In the zoned grains, the composition of the core is modified...... has been used to compute the nature of the parental melt. The parental melt calculations indicate derivation from a high-Mg komatiitic basalt that is similar to the composition of the komatiitic rocks reported from the greenstone sequences of the Western Dharwar Craton. Tectonic discrimination...

  8. Performance evaluation of commercial copper chromites as burning rate catalyst for solid propellants

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    Milton Faria Diniz


    Full Text Available Copper chromites are well known as burning rate catalysts for the combustion of composite solid propellants, used as a source of energy for rocket propulsion. The propellant burning rate depends upon the catalyst characteristics such as chemical composition and specific surface area. In this work, copper chromite samples from different suppliers were characterized by chemical analysis, FT-IR spectroscopy and by surface area measurement (BET. The samples were then evaluated as burning rate catalyst in a typical composite propellant formulation based on HTPB binder, ammonium perchlorate and aluminum. The obtained surface area values are very close to those informed by the catalyst suppliers. The propellant processing as well as its mechanical properties were not substantially affected by the type of catalyst. Some copper chromite catalysts caused an increase in the propellant burning rate in comparison to the iron oxide catalyst. The results show that in addition to the surface area, other parameters like chemical composition, crystalline structure and the presence of impurities might be affecting the catalyst performance. All evaluated copper chromite samples may be used as burning rate catalyst in composite solid propellant formulations, with slight advantages for the SX14, Cu-0202P and Cu-1800P samples, which led to the highest burning rate propellants.

  9. Determining the Impactor of the Ordovician Lockne Crater: Oxygen Isotopes in Chromite Versus Sedimentary PGE Signatures (United States)

    Schmitz, B.; Heck, P. R.; Alwmark, C.; Kita, N. T.; Peucker-Ehrenbrink, B.; Ushikubo, T.; Valley, J. W.


    Oxygen isotopic results for chromite from the Lockne cCater and new PGE results show that the claims by Tagle and Schmitt (2008, LPSC abstr. #1418) that the Lockne Crater was caused by a nonmagmatic iron meteorite lacks substance entirely.

  10. An Exercise in X-Ray Diffraction Using the Polymorphic Transition of Nickel Chromite. (United States)

    Chipman, David W.


    Describes a laboratory experiment appropriate for a course in either x-ray crystallography or mineralogy. The experiment permits the direct observation of a polymorphic transition in nickel chromite without the use of a special heating stage or heating camera. (Author/GS)


    We evaluated a method for delivering ferrous iron into the subsurface to enhance chemical reduction of Cr(VI) in a chromite ore processing solid waste (COPSW). The COPSW is characterized by high pH (8.5 -11.5), high Cr(VI) concentrations in the solid phase (up to 550 mg kg-1) and...

  12. Beneficiation of Konya-Beyşehir Chromite for Producing Concentrates Suitable for Industry (United States)

    Öztürk, Fatma Deniz; Abakay Temel, Halime


    Turkey has a 6% share of world chromite mining and possesses 25 million tons of reserves. Despite their economic importance, the most important Turkish chromite reserves have not been extensively studied with respect to their composition. In this study, the possibility of upgrading Konya-Beyşehir (Turkey) chromite to produce chromite concentrates suitable for industry is investigated. Two groups of enrichment experiments were made. The effects of some parameters that markedly influence the separation of a shaking table, such as the amplitude and slope of the shaking table and the frequency of strokes were investigated in the first group of experiments, The shaking table experiments were planned and carried out using the statistical methods of Design of Experiments (Yate's and ANOVA) in the second group of experiments. As a result, it was found that a concentrate containing 46.89% Cr2O3 content with a yield of 85.18% was obtained from a feed containing 3.98% Cr2O3 content in 0.2 + 0.1 mm size fraction.

  13. Chromite/titanate based perovskites for application as anodes in solid oxide fuel cells

    NARCIS (Netherlands)

    Pudmich, G.; Boukamp, B.A.; Gonzalez-Cuenca, M.; Jungen, W.; Zipprich, W.; Tietz, F.


    Perovskites containing lanthanides, partially substituted by alkaline-earth elements and transition metals like Cr, Ti, Fe or Co show a very broad range of physical properties. Therefore several perovskite materials, based on lanthanum chromite and strontium titanate were synthesised and investigate

  14. Occurrence and emplacement of chromite ores in Sindhudurg district, Maharashtra, India

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Babu, E.V.S.S.K.; Mislankar, P.G.; Gujar, A.R.; Ambre, N.V.; Loveson, V.J.

    and are associated with metamorphic and ultrabasic rocks, consist of octahedral grains of chromite, while clinochlore is present between the interstices of these grains. The Kankavali (janoli) and Wagda ores revealed a dominance of Cr sub(2) O sub(3) followed by Fe...

  15. Insight into the Consolidation Mechanism of Oxidized Pellets Made from the Mixture of Magnetite and Chromite Concentrates (United States)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Zhang, Qiang; Shi, Benjing; Zhang, Feng


    To produce more competitive stainless steel products, the utilization of low-cost chromite concentrate is of great importance. In a previous study, a high-quality product pellet (CMP) for blast furnace smelting process made from a mixture of 40 wt pct chromite and 60 wt pct magnetite concentrates was manufactured by a high-pressure grinding rollers pretreatment. In this work, an insight into the consolidation mechanism of CMP is taken in comparison with the oxidized pellets (MP) made from 100 pct magnetite concentrate by adopting the scanning electron microscopy, energy-dispersive spectrometer, and X-ray diffractometer. The mineralogy of the pellets and the morphology of the preheated and roasted mineral particles are demonstrated. To gain better understanding of the consolidation mechanism of CMP, the thermodynamics of chromite-magnetite spinel system and hematite-sesquioxide corundum system in air are considered by using FactSage software. It can be found that the solid-state bonding is the dominant form in the consolidation of CMP, which mainly depends on the recrystallization of hematite, the solid solution bonding in adjacent areas of both magnetite-chromite particles and chromite-chromite particles. The latter two bonds rely on the formation of the miscible sesquioxide and spinel solid solution at the contact areas of particles, which is largely affected by the oxidizability of magnetite and chromite spinels. When more chromite concentrate is blended, the weak bonding among the chromite particles gradually becomes the dominant factor, which will lead to the decrease of the mechanical strength of fired pellets. The presence of a small quantity of siliceous liquid phase in CMP is believed to be beneficial to the hardening by accelerating the ion diffusion rate and forming slag bonds.

  16. High temperature oxidation resistance of rare earth chromite coated Fe-20Cr and Fe-20Cr-4Al alloys

    Directory of Open Access Journals (Sweden)

    Marina Fuser Pillis


    Full Text Available Doped lanthanum chromite has been used in solid oxide fuel cell (SOFC interconnects. The high costs involved in obtaining dense lanthanum chromite have increased efforts to find suitable metallic materials for interconnects. In this context, the oxidation behavior of lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys at SOFC operation temperature was studied. Isothermal oxidation tests were carried out at 1000 °C for 20, 50 and 200 hours. Cyclic oxidation tests were also carried out and each oxidation cycle consisted of 7 hours at 1000/°C followed by cooling to room temperature. The oxidation measurements and the results of SEM/EDS as well as XRD analyses indicated that lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys were significantly more resistant to oxidation compared with the uncoated alloys.

  17. Effect of Chromite-Silica Sands Characteristics on Performance of Ladle Filler Sands for Continuous Casting

    Institute of Scientific and Technical Information of China (English)


    Free opening rate is mainly determined by the performance of the ladle filler sand. High free opening rates of ladles are required in steel making to improve steel quality. Chromite ladle filler sands are one of the most widely used ladle filler sand. Several operative variables and materials characteristics affect the performance of the sands. Three sets of chromite ladle filler sands were selected and researches were focused on the sintering hehaviour and per- formance of the sands under operative conditions. The effect of particle size distribution on sintering, microstruc- ture, flowability, and permeability were presented. In all cases, the particle size varies from 0.1 to 1.5 mm corre- sponding to free flowing powders. One of the samples has higher permeability factor in comparison with others due to low particle size distribution. The other sample presents very good free opening due to its very good flowability and permeability factor.

  18. Chemical and mineralogical characterization of chromite ore processing residue from two recent Indian disposal sites. (United States)

    Matern, Katrin; Kletti, Holger; Mansfeldt, Tim


    Chromite ore processing residue (COPR) is a hazardous waste. Nevertheless, deposition of COPR in uncontrolled surface landfills is still common practice in some countries. Whereas old (between at least 40 and 180 years) COPR from the temperate zone has been intensively investigated, information on COPR in other regions is restricted. Relatively young (ore processing and preventing the migration of Cr(VI) into water bodies are the main challenges when dealing with these COPR.

  19. Peridotite hosted chromite, magnesite and olivine deposits of West Anatolia: A review (United States)

    Zedef, Veysel


    Turkey has important chromite, magnesite and olivine deposits within peridotite host rocks. The peridotites (harzburgite, verlite, lherzolite and dunite) are mostly serpentinised as a result of metasomatic reaction of olivine and pyroxene minerals with percolating water. The serpentinites are generally an important part of ophiolitic complexes which displays a discontinuous belts all over the country. The chromite deposits are often related to cumulates and tectonites (as Alpine and/or podiform type deposits) and despite their small reserves, their grade can reach up to 58 %. In most deposits, a little enrichment efforts, the grade of chromite can easily be reached from 25 % to 40-45 %. The magnesite deposits of West Anatolia is especially concentrated in three provinces. These provinces are Konya, Kutahya and Eskisehir. The magnesites are of cryptocrystalline type and, like chromite deposits, their reserve are small but have high grade with low FeO-CaO and high MgO ratio. Once again, these deposits are found within serpentinised peridotites of ultramafic belts. The total (proven and inferred) magnesite reserves are approximately 200 million tons, and these are mostly cryptocrystalline character. A small amount of sedimentary magnesite deposits also present in Denizli (SW Anatolia) and Erzincan (Eastern Anatolia). The olivine deposits are found within peridotites of Western Anatolia. Especially, the Kızıldag olivine deposits (located between the border of Antalya and Konya provinces) are noteworthy with its huge (9 billion tons) reserves. The main olivine mineral is forsterite (Mg2SiO4) which has economically important when compared to other olivine mineral fayalite. The deposits have no quality problem but have a serious disadvantages since its location far from the ports and railway stations.

  20. Optical constants of various chromites as determined by Kramers-Kronig analysis. (United States)

    Anki, M M; Lefez, B


    The infrared optical constants of a few different powders of chromites, XCr(2)O(4) (where X is Fe, Ni, Mg, Zn, or Cu), have been determined by Kramers-Kronig analysis of their infrared transmission and reflection spectra. The knowledge of these constants allows one to predict the different thin-layer infrared reflection spectra and to compare them, when it is possible, with the reflection spectra calculated with n and k obtained by the use of the classical oscillator method.

  1. Flocculation of chromite ore fines suspension using polysaccharide based graft copolymers

    Indian Academy of Sciences (India)

    N C Karmakar; B S Sastry; R P Singh


    Graft copolymers are being experimented at the laboratory scale as flocculants. All the four graft copolymers, viz. starch--polyacrylamide, amylopectin--polyacrylamide, sodium alginate--polyacylamide and carboxymethyl cellulose--polyacrylamide performed well as flocculants on chromite ore fines suspension. Amylopectin--polyacrylamide, in particular, performed superior to the rest of the series from the point of view of settling velocity of flocs which is the most important aspect in solid–liquid separation.

  2. Investigation of nanocrystalline zinc chromite obtained by two soft chemical routes

    Energy Technology Data Exchange (ETDEWEB)

    Gingasu, Dana [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, Bucharest 060021 (Romania); Mindru, Ioana, E-mail: [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, Bucharest 060021 (Romania); Culita, Daniela C.; Patron, Luminita; Calderon-Moreno, Jose Maria; Preda, Silviu [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, Bucharest 060021 (Romania); Oprea, Ovidiu [“Politehnica” University of Bucharest, Faculty of Chemistry, Polizu Street 1-7, Bucharest (Romania); Osiceanu, Petre [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, Bucharest 060021 (Romania); Morena Pineda, Eufemio [School of Chemistry, University of Manchester, Oxford Road, M 13 9PL Manchester (United Kingdom)


    Graphical abstract: - Highlights: • Two soft chemical routes to synthesize zinc chromites are described. • Glycine is used as chelating agent (precursor method) and fuel (solution combustion method). • The synthesized chromites have crystallite size in the range of 18–27 nm. • An antiferromagnetic (AFM) transition is observed at about T{sub N} ∼ 18 K. - Abstract: Zinc chromite (ZnCr{sub 2}O{sub 4}) nanocrystalline powders were obtained by two different chemical routes: the precursor method and the solution combustion method involving glycine-nitrates. The complex compound precursors, [ZnCr{sub 2}(NH{sub 2}CH{sub 2}COO){sub 8}]·9H{sub 2}O and [ZnCr{sub 2}(NH{sub 2}CH{sub 2}COOH){sub 4.5}]·(NO{sub 3}){sub 8}·6H{sub 2}O, were characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet–visible spectroscopy (UV–vis) and thermal analysis. The structure, morphology, surface chemistry and magnetic properties of ZnCr{sub 2}O{sub 4} powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), infrared and Raman spectroscopy (RS), ultraviolet–visible spectroscopy (UV–vis) and magnetic measurements. X-ray diffraction patterns indicated the chromite spinel phase with good crystallinity and an average crystallite size of approximately 18–27 nm. The band gap values ranged between 3.31 and 3.33 eV. The magnetic measurements indicated an antiferromagnetic transition at T{sub N} ∼ 17.5/18 K.

  3. Survival times of anomalous melt inclusions from element diffusion in olivine and chromite. (United States)

    Spandler, C; O'Neill, H St C; Kamenetsky, V S


    The chemical composition of basaltic magma erupted at the Earth's surface is the end product of a complex series of processes, beginning with partial melting and melt extraction from a mantle source and ending with fractional crystallization and crustal assimilation at lower pressures. It has been proposed that studying inclusions of melt trapped in early crystallizing phenocrysts such as Mg-rich olivine and chromite may help petrologists to see beyond the later-stage processes and back to the origin of the partial melts in the mantle. Melt inclusion suites often span a much greater compositional range than associated erupted lavas, and a significant minority of inclusions carry distinct compositions that have been claimed to sample melts from earlier stages of melt production, preserving separate contributions from mantle heterogeneities. This hypothesis is underpinned by the assumption that melt inclusions, once trapped, remain chemically isolated from the external magma for all elements except those that are compatible in the host minerals. Here we show that the fluxes of rare-earth elements through olivine and chromite by lattice diffusion are sufficiently rapid at magmatic temperatures to re-equilibrate completely the rare-earth-element patterns of trapped melt inclusions in times that are short compared to those estimated for the production and ascent of mantle-derived magma or for magma residence in the crust. Phenocryst-hosted melt inclusions with anomalous trace-element signatures must therefore form shortly before magma eruption and cooling. We conclude that the assumption of chemical isolation of incompatible elements in olivine- and chromite-hosted melt inclusions is not valid, and we call for re-evaluation of the popular interpretation that anomalous melt inclusions represent preserved samples of unmodified mantle melts.

  4. Platinum-group element abundance and distribution in chromite deposits of the Acoje Block, Zambales Ophiolite Complex, Philippines (United States)

    Bacuta, G.C.; Kay, R.W.; Gibbs, A.K.; Lipin, B.R.


    Platinum-group elements (PGE) occur in ore-grade concentration in some of the chromite deposits related to the ultramafic section of the Acoje Block of the Zambales Ophiolite Complex. The deposits are of three types: Type 1 - associated with cumulate peridotites at the base of the crust; Type 2 - in dunite pods from the top 1 km of mantle harzburgite; and Type 3 - like Type 2, but in deeper levels of the harzburgite. Most of the deposites have chromite compositions that are high in Cr with Cr/(Cr + Al) (expressed as chromium index, Cr#) > 0.6; high-Al (Cr# Pd, thought to be characteristic of PGE-barren deposits) and positive slope (Ir Platinum and Pd occur as alloy inclusions (and possibly as solid solution) in interstitial Ni-Cu sulfides and as tellurobismuthides in serpentine and altered sulfides. Variability of PGE distribution may be explained by alteration, crystal fractionation or partial melting processes. Alteration and metamorphism were ruled out, because PGE contents do not correlate with degree of serpentinization or the abundance and type (hydroxyl versus non-hydroxyl) of silicate inclusions in chromite. Preliminary Os isotopic data do not support crustal contamination as a source of the PGEs in the Acoje deposits. The anomalous PGE concentrations in Type 1 high-Cr chromite deposits are attributed to two stages of enrichment: an early enrichment of their mantle source from previous melting events and a later stage of sulfide segregation accompanying chromite crystallization. High-Al chromite deposits which crystallized from basalts derived from relatively low degrees of melting owe their low PGE content to partitioning of PGEs in sulfides and alloys that remain in the mantle. High-Cr deposits crystallized from melts that were previously enriched with PGEs during early melting events of their mantle source; Pt and Pd ore concentrations (ppm levels) are attained by segregation of magmatic sulfides. The Acoje deposits indicate that ophiolites are a

  5. Preparation of Ca Doped Lanthanum Chromite by Sol-Gel Process

    Institute of Scientific and Technical Information of China (English)

    Zang Bangqiang; Ao Qing; Li Dehui; Sun Liangcheng; Liu Ruwei


    Super fine particles of calcium-doped lanthanum chromites were prepared by the sol-gel process in which the chelating agent was citric acid and the dispersant agent was ethylene glycol. The phase of fine particles was analyzed by XRD and the size and shape of the particles were investigated by TEM. The result shows that the nano-particles of La1-xCaxCrO3 can be obtained by the way of Ca2+ complex singly with citric acid and being calcined at 700 ℃.

  6. Application of Full Factorial Experimental Design and Response Surface Methodology for Chromite Beneficiation by Knelson Concentrator

    Directory of Open Access Journals (Sweden)

    Gul Akar Sen


    Full Text Available The present work is undertaken to determine the effect of operational variables, namely: feed rate, centrifugal force and fluidization water flow rate on the efficiency of Knelson concentrator for chromite ore beneficiation. A full factorial design with three factors at three levels and response surface methodology (RSM were applied for this purpose. The quadratic models were developed to predict the concentrate Cr2O3 grade and recovery as the process responses. The results suggest that all the variables affect the grade and recovery of the Cr2O3 concentrate to some degree. However, the fluidization water rate was found as the most effective parameter.

  7. Characterizing toxic Cr(VI) contamination in chromite mine overburden dump and its bacterial remediation. (United States)

    Dhal, B; Das, N N; Thatoi, H N; Pandey, B D


    Cr(VI) generated due to natural oxidation of chromite mineral present in chromite mine overburden (COB) dumps of Sukinda, India, has been characterized by different physico-chemical methods. The Cr(VI) was found to be associated with goethite matrix at a contamination level of 500 mg Cr(VI)kg(-1) of COB. Bacillus sp. isolated from the overburden sample exhibiting high tolerance to the hexavalent chromium, was used for the remediation of Cr(VI) in the overburden. The process was optimized while varying the parameters such as pH (2-9), pulp density (10-60%) and temperature (25-40 °C). Optimal reduction of more than 98% of Cr(VI) in the COB sample was achieved in 16 h at pH∼7.0 and 60% pulp density with the Bacillus sp. (4.05 × 10(7)cells mL(-1)) in absence of media. The exponential rate equation yielded rate constant value of 2.14 × 10(-1)h(-1) at 60% pulp density. The mode of bio-reduction of Cr(VI) in the overburden sample was established by FT-IR, XRD, EPMA and SEM-EDS studies.

  8. Magnetic properties of rare earth HoCrO3 chromites

    Institute of Scientific and Technical Information of China (English)

    SU Yuling; ZHANG Jincang; FENG Zhenjie; LI Zijiong; SHEN Yan; CAO Shixun


    The temperature dependence of the magnetic properties was systemically studied by dc/ac magnetization and specific heat measurement for heavy rare earth HoCrO3 chromites.The results revealed the existence of complex phase coexistence and competitive magnetic behavior in HoCrO3 chromites.It was found that,in the region of higher temperature above 141.0 K,HoCrO3 behaved as a typical Cufie-Weiss paramagnetic (PM).And in the region of low temperature,a novel magnetization behavior was observed with negative magnetization (diamagnetism-like) characteristics under an external field of 100 Oe and M-Tcurves exhibited two symmetrical branches for field cooling (FC) and zero field cooling (ZFC) modes.This behavior indicated the coexistence of canted antiferromagnetic (CAFM) and weak ferromagnetic (FM) phase.These also exhibited the existence of competition mechanism below characteristic temperature TN1=141.0 K and the magnetic order of Ho ion below 7.5 K.The current complex magnetization might be attributed to the interaction between paramagnetic Ho3+moments and canted Cr3+ moments.

  9. Microbial leaching of chromite overburden from Sukinda mines, Orissa, India using Aspergillus niger (United States)

    Biswas, Supratim; Samanta, Saikat; Dey, Rajib; Mukherjee, Siddhartha; Banerjee, Pataki C.


    Leaching of nickel and cobalt from two physical grades (S1, 125-190 μm, coarser and S3, 53-75 μm, finer) of chromite overburden was achieved by treating the overburden (2% pulp density) with 21-d culture filtrate of an Aspergillus niger strain grown in sucrose medium. Metal dissolution increases with ore roasting at 600°C and decreasing particle size due to the alteration of microstructural properties involving the conversion of goethite to hematite and the increase in surface area and porosity as evident from X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (DT-TGA), and field emission scanning electron microscopy (FESEM). About 65% Ni and 59% Co were recovered from the roasted S3 ore employing bioleaching against 26.87% Ni and 31.3% Co using an equivalent amount of synthetic oxalic acid under identical conditions. The results suggest that other fungal metabolites in the culture filtrate played a positive role in the bioleaching process, making it an efficient green approach in Ni and Co recovery from lateritic chromite overburden.

  10. Petrogenesis of chromites from the Manipur ophiolite belt, NE India: evidence for a supra-subduction zone setting prior to Indo-Myanmar collision (United States)

    Pal, Tapan; Bhattacharya, Anindya; Nagendran, G.; Yanthan, N. M.; Singh, R.; Raghumani, N.


    The Manipur ophiolite belt within the Western Ophiolite Belt of the Indo-Myanmar Ranges (IMR), consists of tectonised to massive serpentinised peridotite, dunite pods, chromitite pods/lenses, cumulates, dykes, volcanic rocks and pelagic sediments. Chromitite pods and lenses hosted in peridotitic mantle rocks show magmatic textures, post magmatic brecciation and ferritchromitisation. Electron microprobe analyses show two types of massive chromitite, with one group having high-Cr (Cr# 75-76), medium-Al (Al2O3 12.2-12.4 wt%) chromites (Sirohi-type) and the other group (Gamnom-type) having a wide range of compositions with generally lower Cr and higher Al (Cr# 65-71, Al2O3 15.7-19 wt%). Accessory chromites in peridotitic mantle rocks have consistently low Cr (Cr# 38-39) and high Al (Al2O3 34-35 wt%), whereas chromites in dunite pods have intermediate compositions (Cr# ~60; Al2O3 20.7-21.2 wt%). The chromite chemistry suggests moderate (20 %) partial melting of the tectonised mantle harzburgite. The estimated Al2O3melt, (FeO/MgO)melt and TiO2melt for the Sirohi-type chromites indicate boninitic parentage, whereas chromite compositions from the Gamnom area suggest mixed boninitic—island arc tholeiitic magmas. The compositions of magmatic chromites suggest that the Manipur ophiolite was formed in a supra-subduction zone (SSZ) setting.

  11. PGE distribution in the Chromite bearing mafic-ultramafic Kondapalli Layered Complex, Krishna district, Andhra Pradesh, India

    Directory of Open Access Journals (Sweden)

    Meshram Tushar M.


    Full Text Available The Kondapalli Layered Complex (KLC is a dismembered mafic-ultramafic layered intrusion, mainly composed of gabbroic and anorthositic rocks with subordinate ultramafics and chromitite. Chromitite occurs as lenses, pods, bands and disseminations. Platinum group of minerals (PGMs occur as inclusions within chromite and silicates. The study indicates an inhomogeneous distribution of PGMs and distinct dominance of IPGEs over the PPGEs. The average ΣPGE content of chromite of KLC varies from 64 ppb to 576 ppb with Pt ranging from 5 to 495 ppb, Pd 5 to 191 ppb, Ir 3 to 106 ppb, Ru 3 to 376 ppb and Rh 3 to 135 ppb. The PGMs identified in the KLC indicate primary deposition of the IPGE, preceding chromite, indicating its orthomagmatic nature. Most of the PGM grains are usually below 10 μm. The identified PGMs are Laurite (RuS2, irarsite (Ir, As, S, iridosmine (Os, Ir, undetermined Os-Ir sulphide and Ru-Os-Ir-Zn alloys. Chromite also contains inclusions of pentlandite, millerite, chalcopyrite and pyrite. Study indicating that the KLC have orthomagmatic origin for PGE which are dominated by IPGE group and formed under surpa-subduction zone peridotite setting.

  12. Experimental study on solid state reduction of chromite with rising temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kekkonen, M.; Syynimaa, A.; Holappa, L.


    The solid state reduction of preoxidized sintered chromite pellets, raw pellets, process pellets and lumpy ores have been studied with rising temperature 700-1520 deg C under CO-atmosphere in order to better simulate the conditions in the upper part of a real submerged arc furnace. According to the reduction degree curves the reduction behaviour of chromite pellets seems to be similar. The reduction rate was slow at the beginning but increased rapidly when the temperature reached about 1000 deg C. The final reduction degree was highest in the case of process pellets and lowest in the case of raw pellet. In the case of preoxidized pellets there was not much difference of the reduction rate and final reduction degree between different oxidation states. In the case of lumpy ores the reduction rate and the final reduction degree was much lower compared to the pellets. Optical photographs, phase and microanalysis show that the reduction has proceeded further in the surface of the samples and confirmed also that the reduction degree remained lower in the case of raw pellet and lumpy ores which was also seen from the reduction degree curves. According to the experiments in the case of preoxidized pellets the effect of oxidation state on the reduction rate was not observed due to small difference in the oxidation state of the samples. But when comparing the reduction of preoxidized pellets and unoxidised raw pellet we can say that preoxidation promotes the reduction. The final reduction degree of the raw pellet remained lower than in the case of preoxidized pellets. (orig.)

  13. Hydrothermal synthesis of perovskite strontium doped lanthanum chromite fine powders and its sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rendon-Angeles, J.C., E-mail: [Research Institute for Advanced Studies of the NPI, Campus-Saltillo, Ramos Arizpe 25900, Coah. (Mexico); Research Laboratory of Hydrothermal Chemistry, Kochi University, Kochi 780-8520 (Japan); Yanagisawa, K. [Research Laboratory of Hydrothermal Chemistry, Kochi University, Kochi 780-8520 (Japan); Matamoros-Veloza, Z. [Saltillo Institute of Technology, Dep. Metal-Mecanica, Saltillo 25820, Coah. (Mexico); Pech-Canul, M.I.; Mendez-Nonell, J. [Research Institute for Advanced Studies of the NPI, Campus-Saltillo, Ramos Arizpe 25900, Coah. (Mexico); Torre, S. Diaz-de la [Research Institute for Technology Innovation, CIITEC-IPN, Azcapotzalco 02250 (Mexico)


    Sr doped lanthanum chromite powders with two different compositions, La{sub 0.9}Sr{sub 0.1}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3}, were prepared from precursor lanthanum chromite gels obtained by the coprecipitation method, followed by hydrothermal treatments at temperatures from 400 to 450 {sup o}C, for various reaction times varying from 0.5 to 2 h. The reaction products were characterized by XRD, SEM and TEM techniques. The powder was cold isostatically pressed at 200 MPa, and then sintered in air at 1500 {sup o}C for several intervals (1-20 h). Relative density measurements were conducted by helium pycnometry and the microstructure was revealed by SEM after thermal etching. The X-ray diffraction patterns of the powders corresponding to La{sub 0.9}Sr{sub 0.1}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} nominal compositions obtained at 400 and 425 {sup o}C for 1 h, respectively, were indexed with that of the orthorhombic single LaCrO{sub 3} phase. SEM and TEM micrographs showed that the particles had irregular peanut-like morphology, and the average particle size was 300 nm. Furthermore, the maximum relative density of the La{sub 0.8}Sr{sub 0.2}CrO{sub 3} sample obtained by the heat treatment in air at 1500 {sup o}C for 20 h was 97% of the theoretical density and the average grain size of the sintered pellet was of 5 {mu}m. The electric conductivity and activation energy determined for this pellet were 14477.3 S m{sup -1} and 0.13 eV, respectively.

  14. Fabrication of Sr- and Co-doped lanthanum chromite interconnectors for SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Setz, L.F.G. [Departamento de Engenharia de Materiais, Universidade Federal de Sao Carlos - DEMa/UFSCar (Brazil); Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Santacruz, I. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Universidad de Malaga, 29071 Malaga (Spain); Colomer, M.T., E-mail: [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain); Mello-Castanho, S.R.H. [Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Moreno, R. [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain)


    Graphical abstract: FESEM micrographs of the fresh fracture surfaces for the La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} sintered specimens cast from optimised suspensions with 13.5, 15 and 17.5 vol.% solids loading. Aqueous suspensions were prepared using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h. Highlights: {yields} Optimum casting slips were achieved with 3 wt.% of ammonium polyacrylate and 1 wt.% of tetramethylammonium hydroxide. -- Abstract: Many studies have been performed dealing with the processing conditions of electrodes and electrolytes in solid oxide fuel cells (SOFCs). However, the processing of the interconnector material has received less attention. Lanthanum chromite (LaCrO{sub 3}) is probably the most studied material as SOFCs interconnector. This paper deals with the rheology and casting behaviour of lanthanum chromite based materials to produce interconnectors for SOFCs. A powder with the composition La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} was obtained by combustion synthesis. Aqueous suspensions were prepared to solids loading ranging from 8 to 17.5 vol.%, using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. The influence of the additives concentrations and suspension ball milling time were studied. Suspensions prepared with 24 h ball milling, with 3 wt.% and 1 wt.% of PAA and TMAH, respectively, yielded the best conditions for successful slip casting. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h leading to relatively dense materials.

  15. The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt: Petrological and geochemical characteristics and mineralization

    Institute of Scientific and Technical Information of China (English)

    Gehad M.Saleh


    The podiform chromitites occur in a well-preserved mantle sequence consisting of lherzolite-harzburgite with abundant lenses of olivine dunite. The podiform chromitite deposits are common as small and irregularly shaped masses in the Southeastern Desert (SED) of Egypt. The podiform chromitites exhibit a wide range of compositions from high Cr to high Al varieties. The Cr of chrome spinel ranges from 0.67 to 0.88 in olivine-dunite, quite similar to that of the high-Cr chromitite, whereas it is around 0.62 in lherzolite-harzburgite. Primary hydrous mineral inclusions, amphibole and phlogopite, in chrome spinel have been reported for the first time from the Pan-African Proterozoic podiform chromitites. On the other hand, petrographic and geochemical evidence suggests that podiform chromitites in the SED of Egypt were formed as a result of crystallization of mafic melts, probably of boninitic composition, the boninitic parental magmas were probably produced by a second stage of melting above a subduction zone. Three types of chromite ores can be distinguished within the SED of Egypt: (a) sulphide-poor podiform ores; (b) brecciated ores; and (c) sulphide-rich ores. Two textural types of inclusions in chromite are distinguished: (1) primary silicate inclusions generally have high Mg-number (>96), Cr and Ni, and are dominated by pargasitic amphibole, forsterite, diopside, enstatite and Na-phlogopite. A diversity of primary and secondary platinum group minerals (PGM) is described from the chromitites, including alloys, sulphides, sulpharsenides and arsenides of Ru, Os, Ir, Rh, Ni, Cu, Fe and Co; (2) in addition to primary PGM and hydrous silicates, the fluids are of low to moderate salinity, sodium-dominated aqueous solutions with complex gas contents. Variable amounts of water, hydrogen, hydrocarbons, carbon dioxides and nitrogen have been determined in inclusion-rich samples. The chondrite-normalized PGE patterns of lherzolite-harzburgite and olivine-dunite have

  16. A comparison of selected Precambrian Brazilian chromitites: Chromite, PGE-PGM, and Re/Os as parental source indicators (United States)

    Girardi, V. A. V.; Ferrario, A.; Correia, C. T.; Diella, V.


    Mineralogical and geochemical studies were carried out in chromitites belonging to the mafic-ultramafic bodies of Niquelândia, Luanga, and Campo Formoso, which are, respectively, included in the Goiás Massif and the Amazon and São Francisco cratons. The main platinum-group minerals (PGM) included or associated with chromite grains are laurite in Niquelândia and Campo Formoso and sperrylite and braggite in Luanga. The most common primary base metal sulfides (BMS) are pentlandite, chalcopyrite, and minor pyrrhotite. Also present are base metal alloys (BMA), such as awaruite, and the BMS millerite, pyrite, and copper as secondary mineral phases linked to later alteration process. The Luanga chromites display the lowest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios. The chondrite-normalized profiles are strongly enriched in the platinum PGE subgroup (PPGE, Pt, Pd, Rh). The average Pd/Ir ratio (24.2) and 187Os/ 188Os values (0.17869-0.18584) are very high. Niquelândia chromites have higher Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios than Luanga. Its PGE contents are low and chondrite-normalized profiles depleted, mainly in the PPGE subgroup. The average Pd/Ir ratio (0.45) and 187Os/ 188Os values (0.12598-0.12777) are low. Campo Formoso chromites have the highest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios; its average Pd/Ir ratio (0.72) and chondrite-normalized profiles (except the pronounced Ru spike) are closer to those of Niquelândia. The remarkable differences in terms of chromite bulk-composition, PGE contents and patterns, Pd/Ir ratios, and 187Os/ 188Os values associated with probable distinctions in the inferred geochemical compositions of the respective parental magmas indicate that the Luanga and Niquelândia complexes originated from distinct parental sources. Geochemical and isotopic features indicate that Luanga chromitites and associated rocks are consistent with a parental magma, either originated from an enriched mantle reservoir or strongly contaminated

  17. A search for H-chondritic chromite grains in sediments that formed immediately after the breakup of the L-chondrite parent body 470 Ma ago (United States)

    Heck, Philipp R.; Schmitz, Birger; Rout, Surya S.; Tenner, Travis; Villalon, Krysten; Cronholm, Anders; Terfelt, Fredrik; Kita, Noriko T.


    A large abundance of L-chondritic material, mainly in the form of fossil meteorites and chromite grains from micrometeorites, has been found in mid-Ordovician 470 Ma old sediments globally. The material has been determined to be ejecta from the L chondrite parent body breakup event, a major collision in the asteroid belt 470 Ma ago. In this study we search the same sediments for H-chondritic chromite grains in order to improve our understanding of the extraterrestrial flux to Earth after the asteroid breakup event. We have used SIMS in conjunction with quantitative SEM/EDS to determine the three oxygen isotopic and elemental compositions, respectively, of a total of 120 randomly selected, sediment-dispersed extraterrestrial chromite grains mainly representing micrometeorites from 470 Ma old post-breakup limestone from the Thorsberg quarry in Sweden and the Lynna River site in Russia. We show that 99% or more of the grains are L-chondritic, whereas the H-chondritic fraction is 1% or less. The L-/H-chondrite ratio after the breakup thus was >99 compared to 1.1 in today's meteoritic flux. This represents independent evidence, in agreement with previous estimates based on sediment-dispersed extraterrestrial chromite grain abundances and sedimentation rates, of a two orders of magnitude higher post-breakup flux of L-chondritic material in the micrometeorite fraction. Finally, we confirm the usefulness of three oxygen isotopic SIMS analyses of individual extraterrestrial chromite grains for classification of equilibrated ordinary chondrites. The H- and L-chondritic chromites differ both in their three oxygen isotopic and elemental compositions, but there is some overlap between the groups. In chromite, TiO2 is the oxide most resistant to diagenesis, and the combined application of TiO2 and oxygen three-isotope analysis can resolve uncertainties arising from the compositional overlaps.

  18. Hexavalent chromium reduction by aerobic heterotrophic bacteria indigenous to chromite mine overburden

    Directory of Open Access Journals (Sweden)

    Dey Satarupa


    Full Text Available Microbiological analysis of overburden samples collected from chromite mining areas of Orissa, India revealed that they are rich in microbial density as well as diversity and dominated by Gramnegative (58% bacteria. The phenotypically distinguishable bacterial isolates (130 showed wide degree of tolerance to chromium (2-8 mM when tested in peptone yeast extract glucose agar medium. Isolates (92 tolerating 2 mM chromium exhibited different degrees of Cr+6 reducing activity in chemically defined Vogel Bonner (VB broth and complex KSC medium. Three potent isolates, two belonging to Arthrobacter spp. and one to Pseudomonas sp. were able to reduce more than 50 and 80% of 2 mM chromium in defined and complex media respectively. Along with Cr+6 (MIC 8.6-17.8 mM, the isolates showed tolerance to Ni+2, Fe+3, Cu+2 and Co+2 but were extremely sensitive to Hg+2 followed by Cd+2, Mn+2 and Zn+2. In addition, they were resistant to antibiotics like penicillin, methicillin, ampicillin, neomycin and polymyxin B. During growth under shake-flask conditions, Arthrobacter SUK 1201 and SUK 1205 showed 100% reduction of 2 mM Cr+6 in KSC medium with simultaneous formation of insoluble precipitates of chromium salts. Both the isolates were also equally capable of completely reducing the Cr+6 present in mine seepage when grown in mine seepage supplemented with VB concentrate.

  19. Microstructural analyses of Cr(VI) speciation in chromite ore processing Residue (COPR)

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, MARIA; FAKRA, SIRINE C .; Marcus, Matthew A.; Moon, Deok Hyun; Dermatas, Dimitris


    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30percent of its total Cr(VI) (6000 mg/kg) as large crystals(>20 ?m diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50percent of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmilleritewasalso likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment ofHBCOPRis challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to ~;;50percent of Cr(VI) in GB COPR.

  20. Crystal Defects and Cation Redistribution Study on Nanocrystalline Cobalt-Ferri-Chromites by Positron Annihilation Spectroscopy

    Directory of Open Access Journals (Sweden)

    Kunal B. Modi


    Full Text Available Positron lifetime and Doppler broadening measurements were carried out on nanocrystalline (grain size ~60–65 nm samples of the Cr3+-substituted cobalt ferrite system with general chemical formula CoCrxFe2−xO4 (x=0.0−2.0 synthesized by the coprecipitation technique. The results indicated selective trapping of positrons in large vacancy clusters initially at the tetrahedral (A- sites and then with Cr3+-substitution up to concentration (x=0.7, at the octahedral (B- sites. The results are consistent with the cation distribution determined from X-ray diffraction line intensity calculations, which indicated partial inversion of the inverse spinel ferrite, subsequent stabilization over a range of substitution (x=0.7 to 1.7, and finally the full inversion to the normal spinel chromite (CoCr2O4, x=2.0. In the intermediate range of substitution, lattice contraction prevented a fraction of Co2+ ions released from the (B- sites from entering the tetrahedral sites, and these vacancies at the (A- sites trapped positrons. Although the samples were composed of nanocrystalline grains, only an insignificant fraction of positrons were diffused and annihilated at the grain surfaces, since the grain sizes and the thermal diffusion length of positrons nearly overlapped.

  1. Solidification/stabilization of chromite ore processing residue using alkali-activated composite cementitious materials. (United States)

    Huang, Xiao; Zhuang, RanLiang; Muhammad, Faheem; Yu, Lin; Shiau, YanChyuan; Li, Dongwei


    Chromite Ore Processing Residue (COPR) produced in chromium salt production process causes a great health and environmental risk with Cr(VI) leaching. The solidification/stabilization (S/S) of COPR using alkali-activated blast furnace slag (BFS) and fly ash (FA) based cementitious material was investigated in this study. The optimum percentage of BFS and FA for preparing the alkali-activated BFS-FA binder had been studied. COPR was used to replace the amount of BFS-FA or ordinary Portland cement (OPC) for the preparation of the cementitious materials, respectively. The immobilization effect of the alkali-activated BFS-FA binder on COPR was much better than that of OPC based cementitious material. The potential for reusing the final treatment product as a readily available construction material was evaluated. X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS) analysis indicated that COPR had been effectively immobilized. The solidification mechanism is the combined effect of reduction, ion exchange, precipitation, adsorption and physical fixation in the alkali-activated composite cementitious material.

  2. Evaluation of the treatment of chromite ore processing residue by ferrous sulfate and asphalt. (United States)

    Moon, Deok Hyun; Wazne, Mahmoud; Koutsospyros, Agamemnon; Christodoulatos, Christos; Gevgilili, Halil; Malik, Moinuddin; Kalyon, Dilhan M


    The effectiveness of the treatment of chromite ore processing residue (COPR) with ferrous sulfate and encapsulation into asphalt were explored separately and in combination. The asphalt treatment was conducted by mixing COPR or ferrous sulfate pretreated COPR with varying amounts of asphalt. To assess the efficacy of the treatment, the leachability of toxicity characteristic leaching procedure (TCLP) total chromium (Cr) from all treated samples was determined for curing periods up to 16 months. X-ray absorption near edge structure (XANES) analyses were also performed to evaluate the Cr(6+) concentration in the selected samples. The combination treatment of ferrous sulfate and the encapsulation of the treated COPR into asphalt reduced the TCLP total Cr concentration to lower than the regulatory limit of 5mg/L for Cr contaminated soils, after 16 months. However, the Cr concentrations were still higher than the universal treatment standards (UTS) of 0.6 mg/L for hazardous waste. On the other hand, treatment with ferrous sulfate alone or the encapsulation of the COPR in asphalt failed to meet the TCLP total Cr concentration of 5mg/L, after 16 months. XANES analyses results showed that more than 75% Cr(6+) reduction was achieved upon pretreatment with ferrous sulfate.

  3. Structural, Optical, and Magnetic Characterization of Spinel Zinc Chromite Nanocrystallines Synthesised by Thermal Treatment Method

    Directory of Open Access Journals (Sweden)

    Salahudeen A. Gene


    Full Text Available The present study reports the structural and magnetic characterization of spinel zinc chromite (ZnCr2O4 nanocrystallines synthesized by thermal treatment method. The samples were calcined at different temperatures in the range of 773 to 973 K. Polyvinylpyrrolidone was used to control the agglomeration of the nanoparticles. The average particle size of the synthesized nanocrystals was determined by powder X-ray diffraction which shows that the crystallite size increases from 19 nm at 773 K to 24 nm at 973 K and the result was in good agreement with the transmission electron microscopy images. The elemental composition of the samples was determined by energy dispersed X-ray spectroscopy which confirmed the presence of Zn, Cr, and O in the final products. Fourier transform infrared spectroscopy also confirmed the presence of metal oxide bands for all the samples calcined at different temperature. The band gap energy was calculated from UV-vis reflectance spectra using the Kubelka-Munk function and the band gap energy of the samples was found to decrease from 4.03 eV at 773 K to 3.89 eV at 973 K. The magnetic properties were also demonstrated by electron spin resonance spectroscopy, the presence of unpaired electrons was confirmed, and the resonant magnetic field and the g-factor of the calcined samples were also studied.

  4. Comparison of the Oxidation Behaviors of High FeO Chromite and Magnetite Concentrates Relevant to the Induration of Ferrous Pellets (United States)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Li, Xiaobo


    Oxidation process plays an important role in producing sufficiently strong ferrous pellets for blast furnace, and the oxidation behavior of pellet feed greatly affects the quality of pellets. As a supplementary research to earlier published work, the present study fixes its particular attention on the fundamental oxidation behavior of a high FeO South African chromite concentrate in comparison to that of typical magnetite concentrate using differential scanning calorimetry, X-ray diffraction analysis, and thermogravimetry at various temperatures ranging from 473 K to 1273 K (200 °C to 1000 °C). The reaction mechanism and phase transformation during the oxidation process of chromite spinel is further explained by thermodynamics calculation performed by FactSage software. Besides, routine laboratory preheating-roasting test of single ore pellets is also conducted to reveal the relevance of oxidizability to the consolidation of pellets. The results show that the chromite spinel possesses much poorer oxidizability than magnetite, usually accompanying complex phase transformations via a preferential nucleation of Fe-rich sesquioxide from the chromite spinel matrix at low temperatures and thereafter the formation of Cr-rich sesquioxide on the substrate of Fe-rich phase at high temperatures. The oxidation of chromite spinel is inferior to that of magnetite from the viewpoint of thermodynamics and dynamic kinetics. Good inherent oxidizability of raw materials is found to have a positive effect on the induration process of pellet.

  5. Trace-element fingerprints of chromite, magnetite and sulfides from the 3.1 Ga ultramafic-mafic rocks of the Nuggihalli greenstone belt, Western Dharwar craton (India) (United States)

    Mukherjee, Ria; Mondal, Sisir K.; González-Jiménez, José M.; Griffin, William L.; Pearson, Norman J.; O'Reilly, Suzanne Y.


    The 3.1 Ga Nuggihalli greenstone belt in the Western Dharwar craton is comprised of chromitite-bearing sill-like ultramafic-mafic rocks that are surrounded by metavolcanic schists (compositionally komatiitic to komatiitic basalts) and a suite of tonalite-trondhjemite-granodiorite gneissic rocks. The sill-like plutonic unit consists of a succession of serpentinite (after dunite)-peridotite-pyroxenite and gabbro with bands of titaniferous magnetite ore. The chromitite ore-bodies (length ≈30-500 m; width ≈2-15 m) are hosted by the serpentinite-peridotite unit. Unaltered chromites from massive chromitites (>80 % modal chromite) of the Byrapur and Bhaktarhalli chromite mines in the greenstone belt are characterized by high Cr# (100Cr/(Cr + Al)) of 78-86 and moderate Mg# (100 Mg/(Mg + Fe2+)) of 45-55. In situ trace-element analysis (LA-ICPMS) of unaltered chromites indicates that the parental magma of the chromitite ore-bodies was a komatiite lacking nickel-sulfide mineralization. In the Ga/Fe3+# versus Ti/Fe3+# diagram, the Byrapur chromites plot in the field of suprasubduction zone (SSZ) chromites while those from Bhaktarhalli lie in the MOR field. The above results corroborate our previous results based on major-element characteristics of the chromites, where the calculated parental melt of the Byrapur chromites was komatiitic to komatiitic basalt, and the Bhaktarhalli chromite was derived from Archean high-Mg basalt. The major-element chromite data hinted at the possibility of a SSZ environment existing in the Archean. Altered and compositionally zoned chromite grains in our study show a decrease in Ga, V, Co, Zn, Mn and enrichments of Ni and Ti in the ferritchromit rims. Trace-element heterogeneity in the altered chromites is attributed to serpentinization. The trace-element patterns of magnetite from the massive magnetite bands in the greenstone belt are similar to those from magmatic Fe-Ti-V-rich magnetite bands in layered intrusions, and magnetites from

  6. Heavy metal and nutrient concentration in soil and plants growing on a metalliferous chromite minespoil. (United States)

    Samantaray, S; Rout, G R; Das, P


    Metal contamination in soil and plant samples from a chromite mine and its adjoining regions was determined. The metal concentration varied in stem, leaf and root of different tree species. In the case of shrubs, the highest concentration of iron (18.5 mg kg(-1) was detected in the stem of Combretum roxburghii. The concentration of aluminium varied from 1.8 - 5.3 mg kg(-1) dry weight, whereas the nickel content was found to be the highest in the stem of Calotropis gigantea. In the case of herbs, chromium concentration was highest (60.9 mg kg(-1) dry weight) in Evovulus alsenoides and the lowest (18.8 mg kg(-1) dry weight) in Andrographis paniculata. There was a significant correlation observed between chromium in soil with the root of tree species like Lagerstroemia parviflora, Madhuca longifolia, Anogeissus latifolia and Haldina cordyfolia. Nickel in soil was significantly correlated with the stem and leaf of all the tree species except Chlroxylon sweitenta. Iron in soil showed correlation with the stem and leaf of Chloroxylon sweitenia. Among the shrubs (Calotropis gigantea, Combretum roxburghii and Smilax zeylancia), chromium in soil showed a correlation with the root. Nickel in soil was positively correlated with the stem and leaf of Calotropis gigantea and Combretum roxburghii. Among the herbs, chromium in the whole plant of Evolvulus alsenoids, Solanum surattense and Phyllanthus fraternus showed significant positive correlation with soil; nickel in Solanum surattense showed significant positive correlation with soil. The positive correlation coefficient was observed between iron in the whole plant and soil on Phyllanthus virgatus, Phyllanthus fraternus and Andrographis paniculata. The above information would be useful for the establishment of a vegetation cover on the minewaste heaps.

  7. Rapid synthesis of nanocrystalline magnesium chromite and ferrite ceramics with concentrated sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Michalsky, Ronald, E-mail:; Peterson, Brian A.; Pfromm, Peter H.


    Highlights: • Refractory ceramics are produced via rapid solar-thermal processing. • The formed chromite and ferrite spinels have a high specific surface area. • The presence of transition metal oxides enables reduction of Mg cations. • Dinitrogen is reduced only by chromium. • The spinels are stable in reducing environments and in the presence of solar radiation. - Abstract: High-temperature refractory ceramics and catalysts such as MgM{sub 2}O{sub 4} (M = Cr, Fe) are produced conventionally via energy-intensive solid-state syntheses (using 0.44–10 GJ electricity for sintering per ton oxide, equivalent to combustion of 48–1088 kg coal per ton oxide). This article reports rapid production of 17 ± 2 mol% MgFe{sub 2}O{sub 4} and 8.6 ± 0.9 mol% MgCr{sub 2}O{sub 4} after 30 min at 1200 °C employing 0.82 kW m{sup −2} sunlight concentrated at a geometric ratio of about 900 m{sup 2} m{sup −2} using a Fresnel lens. Solar radiation promotes the diffusion-limited ferrite formation (42 ± 5 μmol MgFe{sub 2}O{sub 4} per mol Fe{sub 2}O{sub 3} s{sup −1} vs. 26 ± 3 μmol mol{sup −1} s{sup −1} in absence of sunlight) while the transition metals promote the reduction of Mg{sup 2+}. The nanocrystalline and macroporous spinel has a specific surface area of 9.7–11.9 m{sup 2} g{sup −1} (in the order of sol–gel synthesis methods) and is stable under extreme conditions, i.e., high temperature, solar radiation, and reducing agents.

  8. Assessment of ferrous chloride and Portland cement for the remediation of chromite ore processing residue. (United States)

    Jagupilla, Santhi C; Wazne, Mahmoud; Moon, Deok Hyun


    Chromite Ore Processing Residue (COPR) is an industrial waste containing up to 7% chromium (Cr) including up to 5% hexavalent chromium [Cr(VI)]. The remediation of COPR has been challenging due to the slow release of Cr(VI) from a clinker like material and thereby the incomplete detoxification of Cr(VI) by chemical reagents. The use of sulfur based reagents such as ferrous sulfate and calcium polysulfide to detoxify Cr(VI) has exasperated the swell potential of COPR upon treatment. This study investigated the use of ferrous chloride alone and in combination with Portland cement to address the detoxification of Cr(VI) in COPR and the potential swell of COPR. Chromium regulatory tests, X-ray powder diffraction (XRPD) analyses and X-ray absorption near edge structure (XANES) analyses were used to assess the treatment results. The treatment results indicated that Cr(VI) concentrations for the acid pretreated micronized COPR as measured by XANES analyses were below the New Jersey Department of Environmental Protection (NJDEP) standard of 20 mg kg(-1). The Toxicity characteristic leaching procedure (TCLP) Cr concentrations for all acid pretreated samples also were reduced below the TCLP regulatory limit of 5 mg L(-1). Moreover, the TCLP Cr concentration for the acid pretreated COPR with particle size ⩽0.010 mm were less than the universal treatment standard (UTS) of 0.6 mg L(-1). The treatment appears to have destabilized all COPR potential swell causing minerals. The unconfined compressive strength (UCS) for the treated samples increased significantly upon treatment with Portland cement.

  9. Detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic. (United States)

    Liao, Chang-Zhong; Tang, Yuanyuan; Lee, Po-Heng; Liu, Chengshuai; Shih, Kaimin; Li, Fangbai


    A promising strategy for the detoxification and immobilization of chromite ore processing residue (COPR) in a spinel-based glass-ceramic matrix is reported in this study. In the search for a more chemically durable matrix for COPR, the most critical crystalline phase for Cr immobilization was found to be a spinel solid solution with a chemical composition of MgCr1.32Fe0.19Al0.49O4. Using Rietveld quantitative X-ray diffraction analysis, we identified this final product is with the phases of spinel (3.5wt.%), diopside (5.2wt.%), and some amorphous contents (91.2wt.%). The partitioning ratio of Cr reveals that about 77% of the Cr was incorporated into the more chemically durable spinel phase. The results of Cr K-edge X-ray absorption near-edge spectroscopy show that no Cr(VI) was observed after conversion of COPR into a glass-ceramic, which indicates successful detoxification of Cr(VI) into Cr(III) in the COPR-incorporated glass-ceramic. The leaching performances of Cr2O3 and COPR-incorporated glass-ceramic were compared with a prolonged acid-leaching test, and the results demonstrate the superiority of the COPR-incorporated glass-ceramic matrix in the immobilization of Cr. The overall results suggest that the use of affordable additives has potential in more reliably immobilizing COPR with a spinel-based glass-ceramic for safer disposal of this hazardous waste.

  10. The variability of ruthenium in chromite from chassignite and olivine-phyric shergottite meteorites: New insights into the behavior of PGE and sulfur in Martian magmatic systems (United States)

    Baumgartner, Raphael J.; Fiorentini, Marco L.; Baratoux, David; Ferrière, Ludovic; Locmelis, Marek; Tomkins, Andrew; Sener, Kerim A.


    The Martian meteorites comprise mantle-derived mafic to ultramafic rocks that formed in shallow intrusions and/or lava flows. This study reports the first in situ platinum-group element data on chromite and ulvöspinel from a series of dunitic chassignites and olivine-phyric shergottites, determined using laser-ablation ICP-MS. As recent studies have shown that Ru has strongly contrasting affinities for coexisting sulfide and spinel phases, the precise in situ analysis of this element in spinel can provide important insights into the sulfide saturation history of Martian mantle-derived melts. The new data reveal distinctive differences between the two meteorite groups. Chromite from the chassignites Northwest Africa 2737 (NWA 2737) and Chassigny contained detectable concentrations of Ru (up to 160 ppb Ru) in solid solution, whereas chromite and ulvöspinel from the olivine-phyric shergottites Yamato-980459 (Y-980459), Tissint, and Dhofar 019 displayed Ru concentrations consistently below detection limit (<42 ppb). The relatively elevated Ru signatures of chromite from the chassignites suggest a Ru-rich ( 1-4 ppb) parental melt for this meteorite group, which presumably did not experience segregation of immiscible sulfide liquids over the interval of mantle melting, melt ascent, and chromite crystallization. The relatively Ru-depleted signature of chromite and ulvöspinel from the olivine-phyric shergottites may be the consequence of relatively lower Ru contents (<1 ppb) in the parental melts, and/or the presence of sulfides during the crystallization of the spinel phases. The results of this study illustrate the significance of platinum-group element in situ analysis on spinel phases to decipher the sulfide saturation history of magmatic systems.

  11. Health risk assessment from contaminated foodstuffs: a field study in chromite mining-affected areas northern Pakistan. (United States)

    Nawab, Javed; Li, Gang; Khan, Sardar; Sher, Hassan; Aamir, Muhammad; Shamshad, Isha; Khan, Anwarzeb; Khan, Muhammad Amjad


    This study aimed to investigate the potential health risk associated with toxic metals in contaminated foodstuffs (fruits, vegetables, and cereals) collected from various agriculture fields present in chromite mining-affected areas of mafic and ultramafic terrains (northern Pakistan). The concentrations of Cr, Ni, Zn, Cd, and Pb were quantified in both soil and food samples. The soil samples were highly contaminated with Cr (320 mg/kg), Ni (108 mg/kg), and Cd (2.55 mg/kg), which exceeded their respective safe limits set by FAO/WHO. Heavy metal concentrations in soil were found in the order of Cr>Ni>Pb>Zn>Cd and showed significantly (p risk assessment revealed no potential risk for both adults and children for the majority of heavy metals, except Cd, which showed health risk index (HRI) >1 for children and can pose potential health threats for local inhabitants. Graphical Abstract Heavy metals released from chromite mining lead to soil and foodstuff contamination and human health risk.

  12. Environmental status of groundwater affected by chromite ore processing residue (COPR) dumpsites during pre-monsoon and monsoon seasons. (United States)

    Matern, Katrin; Weigand, Harald; Singh, Abhas; Mansfeldt, Tim


    Chromite ore processing residue (COPR) is generated by the roasting of chromite ores for the extraction of chromium. Leaching of carcinogenic hexavalent chromium (Cr(VI)) from COPR dumpsites and contamination of groundwater is a key environmental risk. The objective of the study was to evaluate Cr(VI) contamination in groundwater in the vicinity of three COPR disposal sites in Uttar Pradesh, India, in the pre-monsoon and monsoon seasons. Groundwater samples (n = 57 pre-monsoon, n = 70 monsoon) were taken in 2014 and analyzed for Cr(VI) and relevant hydrochemical parameters. The site-specific ranges of Cr(VI) concentrations in groundwater were <0.005 to 34.8 mg L(-1) (Rania), <0.005 to 115 mg L(-1) (Chhiwali), and <0.005 to 2.0 mg L(-1) (Godhrauli). Maximum levels of Cr(VI) were found close to the COPR dumpsites and significantly exceeded safe drinking water limits (0.05 mg L(-1)). No significant dependence of Cr(VI) concentration on monsoons was observed.


    We developed a method for disseminating ferrous iron in the subsurface to enhance chemical reduction of hexavalent chromium (Cr(VI)) in a chromite ore processing solid waste derived from the production of ferrochrome alloy. The method utilizes ferrous sulfate (FeSO4) in combinati...

  14. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite for methanol synthesis (United States)

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.


    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  15. Separation of gold, palladium and platinum in chromite by anion exchange chromatography for inductively coupled plasma atomic emission spectrometric analysis

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kwang Soon; Lee, Chang Heon; Park, Yeong Jae; Joe, Kih Soo; Kim, Won Ho [KAERI, Taejon (Korea, Republic of)


    A study has been carried out on the separation of gold, iridium, palladium, rhodium, ruthenium and platinum in chromite samples and their quantitative determination using inductively coupled plasma atomic emission spectrometry (ICP-AES). The dissolution condition of the minerals by fusion with sodium peroxide was optimized and chromatographic elution behavior of the rare metals was investigated by anion exchange chromatography. Spectral interference of chromium, a matrix of the minerals, was investigated on determination of gold. Chromium interfered on determination of gold at the concentration of 500 mg/L and higher. Gold plus trace amounts of iridium, palladium, rhodium and ruthenium, which must be preconcentrated before ICP-AES was separated by anion exchange chromatography after reducing Cr(VI) to Cr(III) by H{sub 2}O{sub 2}. AuCl{sup -}{sub 4} retained on the resin column was selectively eluted with acetone- HNO{sub 3}-H{sub 2}O as an eluent. In addition, iridium, palladium, rhodium and ruthenium remaining on the resin column were eluted as a group with concentrated HCl. However, platinum was eluted with concentrated HNO{sub 3}. The recovery yield of gold with acetone-HNO{sub 3}-H{sub 2}O was 100.7 {+-} 2.0 % , and the yields of palladium and platinum with concentrated HCl and HNO{sub 3} were 96.1 {+-} 1.8% and 96.6 {+-} 1.3%, respectively. The contents of gold and platinum in a Mongolian chromite sample were 32.6 {+-} 2.2 {mu}g/g and 1.6 {+-} 0.14 {mu}g/g, respectively. Palladium was not detected.

  16. Present situation and advances in the study of podiform chromite deposits%豆荚状铬铁矿床的研究现状及进展

    Institute of Scientific and Technical Information of China (English)



    The podiform chromite deposit constitutes the main source of metallurgical-grade chromite in industry, but its genesis remains one of the problems for which geologists all over the world show great concern.This paper outlined the status and latest progress in the study of podiform chromite deposits.The latest studies show that podiform deposits mainly occur in a certain layer of the mantle peridotite, which has been the lowest part of ophiolite (CMB, crust-mantle boundary) since Phanerozoic.The podiform chromite deposit-bearing mantle peridotites in the world usually exhibit vertical zoning of melting, with more basic material in the upper part and more acid material in the lower part.With the increasing of partial melting from the bottom upward, there appears lherzolite, harzburgite and dunite in turn.Alpine-type podiform chromite deposits generally have a fairly thick dunitic "envelop".After the mineralization of the podiform chromite deposit, the gravity of itself caused the sinking and dragging of some of the dunite around the ore body downward into the harzburegite fades side under the contact interface with the upside dunite facies, thus forming the typical dunitic "envelop" of the Alpine-type chromite deposit.The authors have thus reached the conclusion that the harzburgite facies under the contact interface is the best target area in search for large chromite deposits.Podiform deposits have a very close genetic relationship with harzburgite and dunite; however, it is really rare to find chromite deposits in lherzolite.The abundance of chromium in primitive mantle is much higher than that in the crust, the chromium element of chromitite was derived from primitive mantle itself, mainly coming from the alteration of associated spinel and the incongruent melting of the two pyroxene (chromium diopside and enstatite).With the increase of partial melting, the mantle peridotite gradually evolved in the magnesium-rich direction, and the mineralization of spinel

  17. The differential stress response of adapted chromite mine isolates Bacillus subtilis and Escherichia coli and its impact on bioremediation potential. (United States)

    Samuel, Jastin; Paul, Madona Lien; Ravishankar, Harish; Mathur, Ankita; Saha, Dipti Priya; Natarajan, Chandrasekaran; Mukherjee, Amitava


    In the current study, indigenous bacterial isolates Bacillus subtilis VITSUKMW1 and Escherichia coli VITSUKMW3 from a chromite mine were adapted to 100 mg L(-1) of Cr(VI). The phase contrast and scanning electron microscopic images showed increase in the length of adapted E. coli cells and chain formation in case of adapted B. subtilis. The presence of chromium on the surface of the bacteria was confirmed by energy dispersive X-ray spectroscopy (EDX), which was also supported by the conspicuous Cr-O peaks in FTIR spectra. The transmission electron microscopic (TEM) images of adapted E. coli and B. subtilis showed the presence of intact cells with Cr accumulated inside the bacteria. The TEM-EDX confirmed the internalization of Cr(VI) in the adapted cells. The specific growth rate and Cr(VI) reduction capacity was significantly higher in adapted B. subtilis compared to that of adapted E. coli. To study the possible role of Cr(VI) toxicity affecting the Cr(VI) reduction capacity, the definite assays for the released reactive oxygen species (ROS) and ROS scavenging enzymes (SOD and GSH) were carried out. The decreased ROS production as well as SOD and GSH release observed in adapted B. subtilis compared to the adapted E. coli corroborated well with its higher specific growth rate and increased Cr(VI) reduction capacity.

  18. Chromium speciation and fractionation in ground and surface waters in the vicinity of chromite ore processing residue disposal sites. (United States)

    Farmer, John G; Thomas, Rhodri P; Graham, Margaret C; Geelhoed, Jeanine S; Lumsdon, David G; Paterson, Edward


    Chromium concentrations of up to 91 mg l(-1) were found by ICP-OES for ground water from nine boreholes at four landfill sites in an area of S.E. Glasgow/S. Lanarkshire where high-lime chromite ore processing residue (COPR) from a local chemical works had been deposited from 1830 to 1968. Surface water concentrations of up to 6.7 mg l(-1) in a local tributary stream fell to 0.11 mg l(-1) in the River Clyde. Two independent techniques of complexation/colorimetry and speciated isotope dilution mass spectrometry (SIDMS) showed that Cr was predominantly (>90%) in hexavalent form (CrVI) as CrO4(2-), as anticipated at the high pH (7.5-12.5) of the sites. Some differences between the implied and directly determined concentrations of dissolved CrIII, however, appeared related to the total organic carbon (TOC) content. This was most significant for the ground water from one borehole that had the highest TOC concentration of 300 mg l(-1) and at which ultrafiltration produced significant decreases in Cr concentration with decreasing size fractions, e.g. complex. This showed for the main Cr-containing fraction, 100 kDa-0.45 microm, that the Cr was associated with a dark brown band characteristic of organic (humic) matter. Comparison of gel electrophoresis and FTIR results for ultrafilter retentates of ground water from this borehole with those for a borehole at another site where CrVI predominated suggested the influence of carboxylate groups, both in reducing CrVI and in forming soluble CrIII-humic complexes. The implications of this for remediation strategies (especially those based on the addition of organic matter) designed to reduce highly mobile and carcinogenic Cr(VI)O4(2-) to the much less harmful CrIII as insoluble Cr(OH)3 are discussed.

  19. Magnetization reversal behavior and magnetocaloric effect in SmCr0.85Mn0.15O3 chromites (United States)

    Kumar, Surendra; Coondoo, Indrani; Vasundhara, M.; Patra, Ajit K.; Kholkin, Andrei L.; Panwar, Neeraj


    We have synthesized SmCr0.85Mn0.15O3 (SCMO) chromites through the ceramic route. The compound crystallized into a distorted orthorhombic structure with the Pnma space group, which was confirmed from the Rietveld refinement of x-ray powder diffraction patterns. Neel temperature, noticed at 168 K from the temperature variation of magnetisation, smaller than that reported for SmCrO3, indicated the influence of Mn3+ substitution on decreasing the antiferromagnetic ordering. A phenomenon of magnetization reversal was observed in the SCMO compound. At low magnetic fields, i.e., 500 Oe, a single compensation temperature (defined as the temperature where magnetization became zero) around 106 K was observed in the field cooled magnetization curve. However, with the application of higher magnetic fields, i.e., under an applied field of 1000 Oe, a second compensation temperature was noticed around 8 K. With a further increase in the magnetic field, the magnetization remained positive in both field cooled and zero field cooled protocols. A normal magnetocaloric effect was observed through an indirect method of field dependence of magnetisation measured in the temperature range of 2-152 K. The magnetic entropy change (-ΔS) of ˜11.36 J kg-1 K-1 along with the relative cooling power (RCP) of ˜175.89 J kg-1 was obtained in the temperature range of 10-20 K for an applied field of 90 kOe, and their values at 50 kOe applied field were, respectively, almost twenty and forty times larger in magnitude in comparison to those for the SmCrO3 compound. The relatively large values of ΔS and RCP make the studied compound a potential candidate for magnetic refrigeration applications at low temperatures.

  20. Assessment of heavy metal tolerance and hexavalent chromium reducing potential of Corynebacterium paurometabolum SKPD 1204 isolated from chromite mine seepage

    Directory of Open Access Journals (Sweden)

    Amal Kanti Paul


    Full Text Available Corynebacterium paurometabolum SKPD 1204 (MTCC 8730, a heavy metal tolerant and chromate reducing bacterium isolated from chromite mine seepage of Odisha, India has been evaluated for chromate reduction under batch culture. The isolate was found to tolerate metals like Co(II, Cu(II, Ni(II, Mn(II, Zn(II, Fe(III and Hg(II along with Cr(VI and was resistant to different antibiotics as evaluated by disc-diffusion method. The isolate, SKPD 1204 was found to reduce 62.5% of 2 mM Cr(VI in Vogel Bonner broth within 8 days of incubation. Chromate reduction capability of SKPD 1204 decreased with increase in Cr(VI concentration, but increased with increase in cell density and attained its maximum at 1010 cells/mL. Chromate reducing efficiency of SKPD 1204 was promoted in the presence of glycerol and glucose, while the highest reduction was recorded at pH 7.0 and 35 °C. The reduction process was inhibited by divalent cations Zn(II, Cd(II, Cu(II, and Ni(II, but not by Mn(II. Anions like nitrate, phosphate, sulphate and sulphite was found to be inhibitory to the process of Cr(VI reduction. Similarly, sodium fluoride, carbonyl cyanide m-chlorophenylhydrazone, sodium azide and N, N,-Di cyclohexyl carboiimide were inhibitory to chromate reduction, while 2,4-dinitrophenol appeared to be neither promotive nor inhibitory to the process.

  1. Origins of chromite and magnetite in sedimentary rocks deposited in a shallow water environment in the 3.2 Ga Moodies Group, South Africa (United States)

    Otake, T.; Sakamoto, Y.; Itoh, S.; Yurimoto, H.; Kakegawa, T.


    *Otake, T. Div. of Sustainable Resources Engineering, Hokkaido Univ., Sapporo, Japan Sakamoto, Y. Dep. of Earth Science, Tohoku Univ., Sendai, Japan Itoh, S. Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Yurimoto. H. Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Kakegawa, T. Dep. of Earth Science, Tohoku Univ., Sendai, Japan Geochemical data from ferruginous chemical sedimentary rocks (e.g., Banded Iron Formation: BIF) have been used to reconstruct the surface environments of early Earth. However, only a few studies have investigated the geochemical characteristics of BIFs deposited in a shallow water environment during the Archean, which may have differed from those deposited in a deep water environment. Therefore, we investigated geological, petrographic and geochemical characteristics of ferruginous rocks deposited in a shallow water environment in the Moodies group, in the Barberton Greenstone Belt, South Africa. We obtained ferruginous rock samples in the Moodies group from both an outcrop and underground gold mine, and compared the characteristics of these samples. The 70 sedimentary rock samples were divided into groups based on the dominant Fe minerals they contain: Hematite-rich jaspilite (HM group), Magnetite-rich iron formation/shale/sandstone (MT group), and Siderite-rich sandstone (SD group). Samples in the HM group are predominantly composed of fine-grained quartz (< 20 μm) and hematite (< 5 μm), which are interpreted to be chemical precipitates. Samples in the MT group contain quartz, magnetite, siderite, ankerite, chlorite, biotite and chromite. The grain size of magnetite is much larger (20-150 μm) than that of hematite in the HM group. The magnetite is interpreted as a secondary mineral transformed from hematite during early diagenesis. Results of in situ oxygen isotope analysis by

  2. Microstructural development and characterization of lanthanum chromite-based ceramics to application in solid oxide fuel cells; Desenvolvimento microestrutural e caracterizacao de ceramicas a base de cromita de lantanio para aplicacao em celulas a combustivel de oxido solido

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, R.N.; Furtado, J.G. de M.; Soares, C.M.; Serra, E.T. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)], e-mail:


    This work has for objective to investigate and to characterize the microstructural development of lanthanum chromite-based ceramics (LaCrO{sub 3}) doped with earth alkaline metals, correlating the microstructural parameters (mainly the densification level) and processing parameters with the electrothermal properties reached. Lanthanum chromite-based ceramic systems doped with earth-alkaline metals (Ca, Mg and Sr) had been produced from respective metallic nitrates by solid state reactions process. The phase compositions were evaluated by X-ray diffraction and the densification level by Archimedes method. The microstructural characterization was effected by scanning electron microscopy, energy dispersive X-ray spectroscopy and thermal analysis techniques. Electrical tests were used to evaluate the electrical conductivity of the studied ceramics. The obtained results corroborate the literature comments concerning the difficulty of lanthanum chromite-based ceramics with high densification level and evidence the great influence of the nature of the dopants on the sintering mechanism and the microstructural and electric characteristics of the produced ceramics. The best ones results, in terms of densification and electrical conductivity, had been gotten through multiple doping with calcium and strontium, and in sintering temperature conditions lower that the normally considered to pure or monodoped lanthanum chromite-based ceramics. (author)

  3. Enhancing the stability of copper chromite catalysts for the selective hydrogenation of furfural with ALD overcoating (II) – Comparison between TiO2 and Al2O3 overcoatings

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongbo; Canlas, Christian; Kropf, A. Jeremy; Elam, Jeffrey W.; Dumesic, James A; Marshall, Christopher L.


    TiO2 atomic layer deposition (ALD) overcoatings were applied to copper chromite catalysts to increase the stability for 2-furfuraldehyde (“furfural”) hydrogenation. After overcoating, about 75% activity was preserved compared to neat copper chromite: much higher activity than an alumina ALD overcoated catalyst with a similar number of ALD cycles. The effects of ALD TiO2 on the active Cu nanoparticles were studied extensively using both in-situ TPR/isothermal-oxidation and in-situ furfural hydrogenation via Cu XAFS. The redox properties of Cu were modified only slightly by the TiO2 ALD overcoat. However, a subtle electronic interaction was observed between the TiO2 ALD layers and the Cu nanoparticles. With calcination at 500 °C the interaction between the TiO2 overcoat and the underlying catalyst is strong enough to inhibit migration and site blocking by chromite, but is sufficiently weaker than the interaction between the Al2O3 overcoat and copper chromite that it does not strongly inhibit the catalytic activity of the copper nanoparticles.

  4. Podiform chromite deposits (United States)

    U.S. Geological Survey, Department of the Interior — Location and characteristics of 1,124 individual mineral deposits of this type, with grade and tonnage models for chromium as well as several related elements.

  5. Doped Yttrium Chromite-Ceria Composite as a Redox-Stable and Sulfur-Tolerant Anode for Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Kyung J.; Coyle, Christopher A.; Marina, Olga A.


    A Ca- and Co-doped yttrium chromite (YCCC) - samaria-doped ceria (SDC) composite was studied in relation to a potential use as a solid oxide fuel cell (SOFC) anode material. Tests performed using the yttria-stabilized zirconia (YSZ) electrolyte-supported cells revealed that the electrocatalytic activity of the YCCC-SDC anode towards hydrogen oxidation at 800 C was comparable to that of the Ni-YSZ anode. In addition, the YCCC-SDC anode exhibited superior sulfur tolerant characteristics showing less than 10% increase in a polarization resistance, fully reversible, upon exposure to 20 ppm H2S at 800 C. No performance degradation was observed during multiple reduction-oxidation (redox) cycles when the anode was intentionally exposed to the air environment followed by the reduction in hydrogen. The redox tolerance of the YCCC-SDC anode was attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal chemical expansion upon redox cycling.


    Directory of Open Access Journals (Sweden)

    David Medved


    Full Text Available The interactions of magnesia-chromite refractory brick with Cu-Na2O.2SiO2 and CuO-Na2O.2SiO2 melts are studied and the chemical durability of corrosion products in water is evaluated. The corrosion tests confirm intensive infiltration of the slag melts into the tested refractory bricks and formation of Cr(6+ compounds. The molten copper partially oxidizes during corrosion test by air and penetrates into bricks. Interactions among periclase (MgO and chromite (FeCr2O4 grains with the melt Na2O.2SiO2 and copper oxides makes possible to form several compounds (e.g. Cu2MgO3, CuCrO4, CaCrO4, Na2CrO4, MgCrO4. Just the marked yellow spots, which were observed on the corroded brick surface after 30 days of free storage, suggest hydration of the high-temperature corrosion products. The yellow color of spots points out to chromates as Na2CrO4 and MgCrO4, which are well soluble in water. The leaching of corroded bricks in water (batch leaching test of a ratio of S (solid : W (water = 0.1 taking up to 28 days confirmed the Cr, Na, Mg and Ca ions leach-out. The pH value of solution increased up to 9 during leaching mainly as a consequence of elevated Na+ ion concentration. The Cr ion concentration rises in the solution up to 1 mmol.l-1. The observed moderate decrease of Cr ion concentration in the solution with the length of leaching indicates super-saturation of the solution and precipitation of the products.

  7. The enhancement effect of pre-reduction using zero-valent iron on the solidification of chromite ore processing residue by blast furnace slag and calcium hydroxide. (United States)

    Li, Jinchunzi; Chen, Zhonglin; Shen, Jimin; Wang, Binyuan; Fan, Leitao


    A bench scale study was performed to assess the effectiveness of the solidification of chromite ore processing residue (COPR) by blast furnace slag and calcium hydroxide, and investigate the enhancement effect of pre-reduction using zero-valent iron (ZVI) on the solidification treatment. The degree of Cr immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as the solid waste-extraction procedure for leaching toxicity-sulfuric acid & nitric acid method (Chinese standard HJ/T299-2007). Strength tests and semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The experimental results showed that the performance of pre-reduction/solidification (S/S) was superior to that of solidification alone. After pre-reduction, all of the S/S treated COPR samples met the TCLP limit for total Cr (5 mg L(-1)), whereas the samples with a COPR content below 40% met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg L(-1)). At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

  8. [Solidification/Stabilization of Chromite Ore Processing Residue (COPR) Using Zero-Valent Iron and Lime-Activated Ground Granulated Blast Furnace Slag]. (United States)

    Chen, Zhong-lin; Li, Jin-chunzi; Wang, Bin-yuan; Fan, Lei-tao; Shen, Ji-min


    The solidification/stabilization (S/S) of chromite ore processing residue (COPR) was performed using zero-valent iron (ZVI) and lime-activated ground granulated blast furnace slag (GGBFS). The degree of Cr immobilization was evaluated using the leaching procedure, mineral composition analysis and morphology analysis. Semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The results showed that after reduction, all of the S/S treated COPR samples met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg x L(-1)), the compressive strength of all the S/S samples could meet the compressive strength standard (15 MPa) for producing clay bricks, and Cr existed as the specie that bound to Fe/Mn oxides in the S/S samples. At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

  9. Comportamento reológico de suspensões aquosas de cromito de lantânio Rheological behaviour of lanthanum chromite aqueous suspension

    Directory of Open Access Journals (Sweden)

    L. F. G. Setz


    Full Text Available O cromito de lantânio (LaCrO3 é o material mais estudado para a produção de interconectores para células a combustível de ��xido sólido (SOFC. Devido a complexidade das microestruturas e geometrias das SOFCs, freqüentemente são necessárias, técnicas de processamento coloidal, os quais têm recebido maior atenção nos últimos anos por permitirem a obtenção de partes complexas com microestrutura controlada e reprodutíveis. Nos últimos anos, muito esforço tem sido direcionado ao processamento dos eletrólitos e eletrodos, mas aos componentes como o interconector, pouca atenção tem sido dada. Este artigo apresenta o estudo reológico e de conformação em moldes de gesso do cromito de lantânio para a produção de interconectores para SOFCs. A composição La0,80Sr0,20Cr0,92Co0,08O3, obtida por reação de combustão, foi utilizada. As suspensões aquosas foram preparadas com conteúdo de sólidos variando de 8 a 17,5% vol. utilizando-se, poliacrilato de amônia (PAA como polieletrólito/dispersante e hidróxido de tetrametilamônio (HTMA como provedor de alcalinidade. A influência da concentração dos aditivos e o tempo em moinho de bolas foram estudados. Os resultados indicam que o tempo 24 h de homogeneização em moinho de bolas, com 3% e 1%, em massa, de PAA e HTMA respectivamente, proporcionam as melhores condições para colagem em moldes de gesso, sendo possível obter peças após sinterização com densidades relativas elevadas.Lanthanum chromite (LaCrO3 is the most studied material for SOFC's interconnectors' production. The complexity of microstructures and geometries of SOFC devices often requires the use of colloidal processing techniques, which have received increased attention in the last years for obtaining complex parts with controlled microstructure and high reliability. Much effort has been devoted to the processing of electrodes and electrolytes but the other layers, such as that of interconnecting

  10. Neoproterozoic chromite-bearing high-Mg diorites in the western part of the Jiangnan orogen, southern China: Geochemistry, petrogenesis and tectonic implications (United States)

    Chen, Xin; Wang, Di; Wang, Xiao-Lei; Gao, Jian-Feng; Shu, Xu-Jie; Zhou, Jin-Cheng; Qi, Liang


    High-Mg diorites were discovered in the southern part of the ca. 830 Ma Dongma Pluton, northern Guangxi Province of southern China. The diorites (SiO2 = 59-65 wt%) are characterized by high MgO (6.7-8.9 wt%) contents and Mg-number [Mg# = 100 × Mg/(Mg + Fe)] (69-73), in contrary to the associated medium-Mg (MgO = 3.4-3.8 wt%, Mg# = 59-63) granodiorites in the Dongma main body and the low-Mg (MgO = 1.4-1.9 wt%, Mg# = 46-51) granodiorites in the Bendong Pluton to the north. Moreover, the high-Mg diorites show surprisingly high Cr (595-640 ppm) and Ni (171-194 ppm) concentrations, which are beyond the ranges of most coeval mafic rocks in the study area. Correspondingly, chromite crystals were separated from the high-Mg diorites and some of the medium-Mg granodiorites, and they show high Cr# [100 × Cr/(Cr + Al)] (average of 75), but low Mg# (0.34-2.51) and low Fe3 +. The decoupling of Cr# and Mg# and the existence of quartz + apatite mineral inclusion in chromites suggest Mg-Fe exchange that may be facilitated by the disequilibrium resulted from magma mixing. The high-Mg diorites show low La/Yb (6.8-8.5) and Sr/Y (2.1-3.1) ratios, significant negative anomalies of Nb and Ti and positive anomaly of Pb, resembling the Setouchi high-Mg andesites, despite of their relatively low Sr (71-100 ppm). All of the studied diorites and granodiorites show enriched Nd isotope compositions, with εNd(t) values (- 3.2 to - 5.9) a bit higher than some of the associated mafic rocks. Some of the high-Mg diorites show whole-rock εHf(t) (- 6.0 to - 6.2) coupled with Nd isotopes, similar to the associated mafic-ultramafic rocks in northern Guangxi, suggesting the metasomatism by melts of subducting sediments in the mantle source. Whereas, others show decoupled Nd-Hf isotopes that are similar to the medium- and low-Mg granodiorites [εHf(t) = - 1.8 to + 0.05], probably indicating the late magma mixing with granitic magmas at a crustal level for the dioritic magmas. We propose a two

  11. Effect of heterovalent substitutions in yttrium chromite on the hyperfine interactions of {sup 119}Sn{sup 4+} studied by Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fabritchnyi, Pavel B., E-mail: [Department of Chemistry, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Afanasov, Mikhail I.; Mezhuev, Evgeny M. [Department of Chemistry, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Wattiaux, Alain; Duttine, Mathieu [CNRS – Université de Bordeaux, Institut de Chimie de la Matière Condensée de Bordeaux, 33608 Pessac Cedex (France); Labrugère, Christine [CNRS – Université de Bordeaux, PLACAMAT UMS 3626, 33608 Pessac Cedex (France)


    In order to develop the {sup 119}Sn Mössbauer spectroscopic probe technique to study magnetically ordered materials, three Ca-substituted yttrium chromites, i.e. Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}, Y{sub 0.9}Ca{sub 0.1}Cr{sub 0.9}Ti{sub 0.1}O{sub 3} and Y{sub 0.8}Ca{sub 0.2}Cr{sub 0.8}Ti{sub 0.2}O{sub 3}, doped with 0.3 atom-% Sn{sup 4+}, were for the first time investigated. {sup 119}Sn Mössbauer spectra, recorded at 4.2 K, have allowed, through analysis of the magnetic hyperfine field values, probed by {sup 119}Sn nuclei, to gain insight into the local magnetically active surrounding of different Sn{sup 4+} ions. In all of these compounds, partial segregation of Sn{sup 4+} ions is revealed. In the case of Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}, neither highly oxidized Cr{sup 4+} nor Cr{sup 6+} species, expected to compensate for the Ca{sup 2+} positive charge deficit, is found in the vicinity of the {sup 119}Sn{sup 4+} probe. In the case of both studied Ti-containing chromites, {sup 119}Sn Mössbauer spectra have provided the original indirect evidence for the statistical distribution of Cr{sup 3+} and Ti{sup 4+} ions over the octahedral sites and permitted characterization of the occurring associates of Sn{sup 4+}. - Graphical abstract: Two kinds of Sn{sup 4+} associates allowing {sup 119}Sn Mössbauer spectra of tin-doped Y{sub 0.9}Ca{sub 0.1}Cr{sub 0.9}Ti{sub 0.1}O{sub 3} and Y{sub 0.8}Ca{sub 0.2}Cr{sub 0.8}Ti{sub 0.2}O{sub 3} to be accounted for. - Highlights: • {sup 119}Sn probe is tested as a source of information on the B-sublattice of AF perovskites. • Neither Cr{sup 3+} nor Cr{sup 6+} is detected nearby {sup 119}Sn{sup 4+} ions in Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}. • Cr{sup 3+} and Ti{sup 4+} are found to be randomly distributed in Y{sub 1−x}Ca{sub x}Cr{sub 1−x}Ti{sub x}O{sub 3} (x=0.1 or 0.2). • Sn{sup 4+} dopant segregations are revealed in all of the studied materials.

  12. Long-term stability of FeSO4 and H2SO4 treated chromite ore processing residue (COPR): Importance of H(+) and SO4(2). (United States)

    Wang, Xin; Zhang, Jingdong; Wang, Linling; Chen, Jing; Hou, Huijie; Yang, Jiakuan; Lu, Xiaohua


    In this study, the long-term stability of Cr(VI) in the FeSO4 and H2SO4 (FeSO4-H2SO4) treated chromite ore processing residue (COPR) after 400 curing days and the stabilization mechanisms were investigated. FeSO4-H2SO4 treatment significantly reduced toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) Cr(VI) concentrations to lower than the regulatory limit of 1.5mgL(-1) (HJ/T 301-2007, China EPA) even for the samples curing 400days, achieving an outstanding long-term stability. Our independent leaching tests revealed that H(+) and SO4(2-) have synergistic effect on promoting the release of Cr(VI), which would make Cr(VI) easier accessed by Fe(II) during stabilization. The contributions of H(+) and SO4(2-) to Cr(VI) release ratio were 25%-44% and 19%-38%, respectively, as 5mol H2SO4 per kg COPR was used. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and alkaline digestion analyses were also employed to interpret the possible stabilization mechanism. Cr(VI) released from COPR solid was reduced to Cr(III) by Fe(II), and then formed stable FexCr(1-x)(OH)3 precipitate. This study provides a facile and reliable scheme for COPR stabilization, and verifies the excellent long-term stability of the FeSO4-H2SO4 treated COPR.

  13. Detrital magnetite and chromite in Jack Hills quartzite cobbles: Further evidence for the preservation of primary magnetizations and new insights into sediment provenance (United States)

    Dare, Matthew S.; Tarduno, John A.; Bono, Richard K.; Cottrell, Rory D.; Beard, James S.; Kodama, Kenneth P.


    The magnetization of zircons from sedimentary rocks of the Jack Hills (Yilgarn Craton, Western Australia) provide evidence for a Hadean to Paleoarchean geodynamo, 4.0 to 4.2 billion years old. These magnetizations pass a microconglomerate test, attesting to the fidelity of Jack Hills zircons as recorders of these most ancient magnetic signals. The lack of pervasive remagnetization of the Jack Hills is also documented through a positive conglomerate test conducted on cobble-sized clasts. A key element of the latter test is the preservation of a high unblocking temperature magnetization that can survive peak metamorphic temperatures. Rock magnetic studies suggest the mineral carrier is magnetite. Herein, we investigate the magnetic mineral carriers in cobble samples through scanning electron microscope and microprobe analyses, conduct an inter-laboratory paleomagnetic study to evaluate sensitivities required to evaluate the weak magnetizations carried by the Jack Hills sediments, and assess provenance information constrained by the opaque minerals. These data confirm magnetite as a detrital phase and the presence of high unblocking temperature magnetizations, further supporting the posit that the Jack Hills sediments can preserve primary magnetic signatures. We note that some of these magnetizations are near the measurement resolution of standard cryogenic magnetometers and thus exacting laboratory procedures are required to uncover these signals. In addition to magnetite, the cobbles contain an assemblage of Mg poor Cr-Fe chromites, Ni-sulfides and pyrrhotite that suggest a source in a layered intrusion different from the granitoid source of the zircons. Any Hadean rock fragment in these sediments, if present, remains elusive.

  14. Meteorology drives ambient air quality in a valley: a case of Sukinda chromite mine, one among the ten most polluted areas in the world. (United States)

    Mishra, Soumya Ranjan; Pradhan, Rudra Pratap; Prusty, B Anjan Kumar; Sahu, Sanjat Kumar


    The ambient air quality (AAQ) assessment was undertaken in Sukinda Valley, the chromite hub of India. The possible correlations of meteorological variables with different air quality parameters (PM10, PM2.5, SO2, NO2 and CO) were examined. Being the fourth most polluted area in the globe, Sukinda Valley has always been under attention of researchers, for hexavalent chromium contamination of water. The monitoring was carried out from December 2013 through May 2014 at six strategic locations in the residential and commercial areas around the mining cluster of Sukinda Valley considering the guidelines of Central Pollution Control Board (CPCB). In addition, meteorological parameters viz., temperature, relative humidity, wind speed, wind direction and rainfall, were also monitored. The air quality data were subjected to a general linear model (GLM) coupled with one-way analysis of variance (ANOVA) test for testing the significant difference in the concentration of various parameters among seasons and stations. Further, a two-tailed Pearson's correlation test helped in understanding the influence of meteorological parameters on dispersion of pollutants in the area. All the monitored air quality parameters varied significantly among the monitoring stations suggesting (i) the distance of sampling location to the mine site and other allied activities, (ii) landscape features and topography and (iii) meteorological parameters to be the forcing functions. The area was highly polluted with particulate matters, and in most of the cases, the PM level exceeded the National Ambient Air Quality Standards (NAAQS). The meteorological parameters seemed to play a major role in the dispersion of pollutants around the mine clusters. The role of wind direction, wind speed and temperature was apparent in dispersion of the particulate matters from their source of generation to the surrounding residential and commercial areas of the mine.

  15. 阿富汗喀布尔超镁铁岩型铬铁矿成矿条件与找矿潜力探讨%Minerogenetic Conditions and Prospecting Potentials on Kabur Ultramafic-Type Chromite Deposit in Afghanistan

    Institute of Scientific and Technical Information of China (English)

    曹积飞; 孟广路; 张晶; 王斌; 李宝强; 计文化; 范堡城; 李慧英


    阿富汗喀布尔地块位于欧亚板块与印度板块碰撞交汇处,属特提斯喜马拉雅成矿域组成部分。伴随晚中生代、新生代以来新特提斯洋的拉张、闭合,喀布尔地块产生了大量与板块俯冲碰撞有关的超镁铁杂岩带,蛇纹石化普遍发育。该超镁铁岩带向东经巴基斯坦延伸至我国西藏境内,著名的罗布莎铬铁矿床可与之对比。洛加尔铬铁矿是喀布尔地块具代表性的、与始新世超镁铁岩有关的岩浆型矿床。典型矿床地质特征研究表明,洛加尔铬铁矿属与PPG型蛇绿岩有关的富铬型地幔橄榄岩熔融产物。通过典型矿床研究与区域成矿条件分析,认为喀布尔地区具良好的成矿地质背景,成矿条件优越,具寻找豆荚状铬铁矿床潜力。%Kabur block in Afghanistan,situating on intersection part between Eurasian plate and Indian plate, belong to component parts of Tethys-Himalaya metallogenic domain.Followed by tension,subduction and closure of Neo-Tethys ocean dating from late Mesozoic,Cenozoic era,a large number of ultrabasic complex belt related with plate subduction and collision generated in the Kabur block,and widespread developed serpentinization. This ultrabasic rock belt extend from Pakistan across eastern Tibet in China, Luo Busha chromite deposit can be comparative. Logar chromite deposit, one typical type of magmatic deposits on Afghanistan massif, is related with ultramafic rocks of Eocene. Ultramafic rock belt hosting ore deposit extends esteran toward to China Tibet through Pakistan, and can compared with ultramafic belt hosting Luo Busha chromite deposit. Analysis and researches about geological characteristics of typical deposit indicate that the Logar chromite deposit belongs to melting products of chromium-rich and mantle peridotite relating with PPG-type ophiolites. Throughing typical deposit studying and regional metallogenetic conditions analyzing, it is believed that Kabur

  16. Experimental Observations of the Patterns of Fungi-Mineral Surfaces Interactions with Muscovite, Biotite, Bauxite, Chromite, Hematite, Galena, Malachite, Manganite and Carbonate Substrates. (United States)

    Claeys, P.


    In an in vitro experimental work, mineral substrates of muscovite, biotite, bauxite, chromite, hematite, galena, malachite, manganite and carbonate were exposed to free fungal growth and interaction in Petri dishes under open conditions. All of the experimental minerals were examined by XRD for identity and purity. The 12-week experiment resulted in significant alteration of the mineral substrates. SEM, EDX, and XRD analysis showed secondary mineral biomineralization represented by different crystal morphologies of Ca- and Mg- oxalates (weddelite: CaC2O4·2H2O, whewellite CaC2O4·H2O and glushinskite: MgC2O4·2H2O), struvite: (NH4) MgPO4·6H2O, gypsum CaSO4.2H2O, and possible dolomite. Metals bioleached from the substrates included: Fe, Pb, S, Cu, Al as single crystals or aggregates, amorphous layers, amorphous aggregates, and linear forms influenced by the fungal filaments. Bauxite and manganite showed the strongest cases of bioleaching where Fe and Al were fungally extracted and deposited as separate mineral species from the Al-Fe oxides mixture, while Ca and S were extracted from the manganite substrate and deposited as gypsum. The bioleached metals were either deposited on the mineral substrates, attached to fungal filaments, embedded in the fungal mycelium or in the extracellular polysaccharide substance (EPS) layer. The EDX microanalysis of the fungal hyphae frequently revealed metal content adsorbed on the hyphae sheath surface. During the short period of the experiment, fungal interaction with the mineral surfaces produced significant biomechanical and biochemical bioweathering features: strong pitting of the mineral surfaces, exfoliation, tunnelling, dissolution, honeycomb-alveolar structures, perforations, fragmentation, and cementation. One important aspect of these interactions is the strong affinity of fungal hyphae to mineral surfaces. The fungi engulfed whole blocks of minerals in the hyphal network, irrespective of mineral surface topography with

  17. Identification and geochemical modeling of processes controlling leaching of Cr(VI) and other major elements from chromite ore processing residue (United States)

    Geelhoed, Jeanine S.; Meeussen, Johannes C. L.; Hillier, Stephen; Lumsdon, David G.; Thomas, Rhodri P.; Farmer, John G.; Paterson, Edward


    Chromite ore processing residue (COPR) contains very high levels of chromium as Cr(III) and Cr(VI) and has a pH of ˜11.5 to 12. Millions of tonnes of COPR have in the past been deposited in urban areas. We have studied the factors that control leaching of Cr(VI), Ca, Al, Si, and Mg from COPR by means of batch experiments, mineralogical characterization of COPR via X-ray powder diffraction and scanning electron microscopy, and chemical equilibrium modeling. Batch experiments at a range of pH values and two liquid:solid ratios showed that mineral solubility control exists for aqueous concentrations of Cr(VI) above pH 10. Calculations indicate that the solid phases that control the solubility of Cr(VI) at pH values above 11 are Cr(VI)-substituted hydrogarnet (Ca 3Al 2(H 4O 4,CrO 4) 3) and Cr(VI)-hydrocalumite (Ca 4Al 2(OH) 12CrO 4·6 H 2O), a layered double-hydroxide clay with chromate anions held in the interlayers. In the pH range 9.5 to 11, the description of the Cr(VI) concentration in solution was strongly improved by the incorporation in the model of Cr(VI)-ettringite (Ca 6Al 2(OH) 12(CrO 4) 3·26 H 2O), which precipitates as a secondary phase when hydrocalumite dissolves. The proposed model for leaching of COPR at high pH includes Cr(VI)-bearing hydrogarnet, Cr(VI)-hydrocalumite, Cr(VI)-ettringite, brucite, calcite, Ca 2Al 2(OH) 10·3 H 2O, CaH 2SiO 4, and gehlenite hydrate (Ca 2Al 2(OH) 6SiO 8H 8·H 2O). The model accurately predicts the concentrations of Cr(VI), Ca, Al, Si, and Mg in solution in the pH range 10 to 12 as well as the pH-buffering behavior. Below pH 8, a decrease in the Cr(VI) concentration in solution is observed, which may be attributed to sorption of chromate onto freshly precipitated Al and Fe hydroxide surfaces. Sulfate and carbonate show the same type of behavior as chromate. The chemistry of COPR shows similarities with cement and high-pH municipal waste incinerator bottom ash.

  18. 藏南罗布莎铬铁矿床铬尖晶石矿物学与矿床成因研究%Study on mineralogy of Cr-spinel and genesis of Luobusha chromite deposit in South Tibet

    Institute of Scientific and Technical Information of China (English)

    周二斌; 杨竹森; 江万; 侯增谦; 郭福生; 洪俊


    俯冲环境的转变过程,洋内俯冲带之上(SSZ)的弧间盆地环境是形成冶金级豆荚状铬铁矿的最为有利构造环境.研究提出了罗布莎铬铁矿的“三阶段”成矿模式,即,经历了大洋中眷预富集阶段,俯冲带之上主成矿阶段及之后的构造抬升改造阶段.纯橄岩与方辉橄榄岩接触带之下的方辉橄榄岩相带是寻找较大规模铬铁矿床的有利地带.%The Luobusha chromite deposit, which is the largest podiform deposit with maximum study in China, occurred in a fresh mantle peridotite in the east part of Yarlung Zangbo ophiolite belt in South Tibet The economic ore bodies of Luobusha chromite deposits are mainly hosted in a specific lithological horizon of harzburgite facies beneath the boundary of ophiolitic crust and mantle (beneath the Moho boundary) , and the ore type mainly includes massive, disseminated and nodular chromitite ores. Luobusha Cr-spinel have a large variety in composition, based on the chemical composition and the detailed mineralogical study of Cr-spinel, at least three crystalline epochs of the Cr-spinel in the Luobusha podiform chromite deposit can be recognized. (1) Pre-mineralization Cr-spinel : This kind of Cr-spinel is mainly as accessory mineral in the harzburgite, and occurred in the form of residual phenocryst, exsolution crystal and euhedral crystal with high A12O3 content, most of the Cr value of the Cr-spinel is less than 60, and has a negative correlation ship with Mg#. The overall evolution of this kind of Cr-spinel from exsolution crystal, residual phenocryst to euhedral crystal of Cr-spinel tends to be riched in Cr and Fe; (2) Main mineralization Cr-spinel can also be divided into two stages. The early stage of Cr-spinel, has a typical characteristic of Cr-riched, is a major mineral with anhedral crystal in a variety type of chromitite ores, and a minor mineral with euhedral crystal in dunite ' envelop' crust outside of the orebodies. Most of the Cr value of

  19. Studies on Effect of Impregnation with Sols on Pore Characteristic of Magnesia Chromite Brick Used in RH%浸溶胶对RH炉用镁铬砖气孔特性的影响研究

    Institute of Scientific and Technical Information of China (English)

    陈希来; 邹龙; 曹锟; 宋仪杰; 李亚伟; 徐国涛


    研究了浸铝溶胶、锆溶胶镁铬砖的气孔特性变化及对抗渣性能的影响.结果表明:浸溶胶后镁铬砖的气孔率减小、气孔孔径分布变好,确定合适的溶胶浸渍次数为3~4次;浸溶胶会提高镁铬砖的抗渣性能,铝溶胶更能提高材料的抗渣渗透性而锆溶胶则更能改善材料的抗渣侵蚀性.%Pore characteristic evolution and slag resistance of magnesia chromite brick impregnated with amumi-na sol and zirconia sol were studied. The results indicate that the porosity decreases and pore size distribution becomes better after the specimens impregnated with sols. The appropriate impregnation times is 3 or 4. The slag resistance characteristic is improved after the specimens impregnated with sols. Alumina sol can be beneficial to enhance the slag anti-penetration and zirconia sol is better to improve the slag anti-corrosion.

  20. Characteristics Research on Chromite from the Poyi Cu-Ni Sulfide-bearing Mafic-ultramafic Intrusions in the Beishan Block,Xinjiang%新疆北山坡-含铜镍镁铁-超镁铁质岩体铬铁矿特征研究

    Institute of Scientific and Technical Information of China (English)

    柴凤梅; 夏芳; 陈斌; 卢鸿飞


    The Poyi maiic-ultramafic intrusion is one of the most important Cu-Ni bearing complexes in Beishan area. This intrusion is composed of peridotite, pyroxenite and gabbro. Chromites occurs in the peridotite as an enhedral, subhedral and anhedral accessory mineral. The characteristics of chromites suggested that the primary magma of the Poyi intrusions must have been mantle-derived S-undersaturated mafic magma derived from asthenosphere mantle source even related to mantle plume and have experienced two stages evolution to form this intrusion. Some chromites enclosed within olivine may be crystallized from the primary magma in the deep magma chamber, and others enclosed within pyroxene and being interstitial crystals may be formed from the olivine- and sulfide-laden crystal mush in the high-level magma chamber. The chromites formed in the early stage of magma evolution are very important for the Cu-Ni sulphide deposit.%坡-镁铁-超镁铁质岩体为新疆北山地区一重要的含铜镍硫化物的侵入体.该岩体主要由橄榄岩、辉石岩和辉长岩组成.铬铁矿主要以副矿物形式现于橄榄岩中.它们以自形-半自形以及它形存在于橄榄石颗粒间或其内,部分为辉石包裹,偶见其包裹橄榄石.结合电子探针研究,认为坡一岩体母岩浆是来源于软流圈地幔或者与地幔柱有关的基性岩浆,原生岩浆经过了两个阶段的演化形成了目前的坡一岩体.包裹于橄榄石中的铬铁矿为岩浆早期深部岩浆房中结晶的产物,其他形式存在的铬铁矿为富含橄榄石和铬铁矿“晶粥”的演化岩浆结晶的结果.铬铁矿的结晶对坡一铜镍矿床的形成具有重要的意义.

  1. Ecosystem Health in Mineralized Terrane-Data from Podiform Chromite (Chinese Camp Mining District, California), Quartz Alunite (Castle Peak and Masonic Mining Districts, Nevada/California), and Mo/Cu Porphyry (Battle Mountain Mining District, Nevada) Deposits (United States)

    Blecker, Steve W.; Stillings, Lisa L.; Amacher, Michael C.; Ippolito, James A.; DeCrappeo, Nicole M.


    various mineralized terranes. We were also interested in examining these relations in the context of determining appropriate reference conditions with which to compare reclamation efforts. The purpose of this report is to present the data used to develop indices of soil and ecosystem quality associated with mineralized terranes (areas enriched in metal-bearing minerals), specifically podiform chromite, quartz alunite, and Mo/Cu porphyry systems. Within each of these mineralized terranes, a nearby unmineralized counterpart was chosen for comparison. The data consist of soil biological, chemical, and physical parameters, along with vegetation measurements for each of the sites described below. Synthesis of these data and index development will be the subject of future publications.

  2. 在表面活性剂存在下铬铁矿表土中镍的微生物萃取%Microbial extraction of nickel from chromite overburdens in the presence of surfactant

    Institute of Scientific and Technical Information of China (English)

    Sunil Kumar BEHERA; Lala Behari SUKLA


    The effect of surfactant polyoxyethylenesorbitan monolaurate (Tween-20) on the nickel bioleaching from pre-treated chromite overburden (COB),Sukinda with fungal strain Aspergillus niger,was examined in shake flasks.Along with the nickel recovery from COB by the fungal bioleaching,the effect of surfactant on the growth of the A.niger was also investigated.Results show that the addition of surfactant in low concentration was favorable for the recovery of nickel from pre-treated COB.Normally,the carbon source (sucrose) in the culture medium was utilized by the A.niger for its cellular metabolism and organic metabolites (bio acids) were produced,which were responsible for the bioleaching of minerals.However,the addition of surfactant (Tween-20)accelerated the rate of sucrose consumption by the fungi,and thus enhancing the extraction of nickel from pre-treated COB.During the study,around 39% nickel extraction was achieved in A.niger mediated bioleaching performed at 2% pulp density of pre-treated COB at 30 ℃,in the presence of surfactant whereas only 24% nickel was extracted without surfactant.%加入表面活性剂吐温20,用Aspergillus niger对预处理过的印度Sukinda铬铁矿表土在摇瓶中生物浸取镍.考察添加表面活性剂吐温20对黑曲霉菌Aspergillus niger生长及浸镍效果的影响.结果表明,添加低浓度的表面活性剂吐温20对黑曲霉菌从预处理过的铬铁矿表土中提取镍是有利的.通常,Aspergillus niger利用培养基中的碳源来进行细胞代谢,产生有机代谢物,从而生物浸出矿.添加表面活性剂吐温20加速了黑曲霉菌对碳源的消耗,从而改善了镍浸出效果.在预处理矿浆浓度为2%和温度为30℃的条件下,添加表面活性剂吐温20的镍浸取率能达到39%,没有表面活性剂的镍浸取率只有24%.

  3. China’s Largest Chromite Mine

    Institute of Scientific and Technical Information of China (English)



  4. Ilmenite, magnetite and chromite beach placers from south Maharashtra, central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gujar, A.R.; Ambre, N.V.; Mislankar, P; Iyer, S.D.

    distance of transportation. Ilmenite has TiO sub(2) in the range between 40.04 and 46.6 wt %. Based on ore microscopy studies, the magnetite grains appear to be of two types: pure magnetite and titano-magnetite. Compositionally, the total magnetite...

  5. The 3.1 Ga Nuggihalli chromite deposits, Western Dhawar craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir K.; Frei, Robert


    , peridotites, and anorthosites, along with the flat heavy REE patterns, resemble the pattern of Al-undepleted komatiites and indicate high degrees of partial melting of the mantle source. The LREE depleted pattern of peridotites reflects derivation from depleted mantle. The pyroxenite and gabbros show...

  6. On preconcentration of nickel from lateritic overburden of chromite by flotation. Pt. 1. Anionic collectors. Die flotative Voranreicherung von Nickel aus dem lateritischen Abraum von Chromit. T. 1. Anionische Sammler

    Energy Technology Data Exchange (ETDEWEB)

    Rao, G.V.; Gouri Charan, T.


    The preconcentration of nickel from lateritic material is considered as difficult task as the nickel in the most cases is finely disseminated in the ore-bodies. In this article a preconcentration route for nickel enrichment to above 2.5 times from a lateritic overburden material by flotation by means of new anionic collectors with trade names HOE F 2874, HOE F 2875 and Flotinor SM-15 along with sodium silicate and another new depressant with trade name Tylose CHR 100 M was suggested. By using any of these new collectors and depressant at optimised conditions established a nickel rich concentrate 1.6% Ni with 60% recovery could be obtained from an overburden material containing 0.6% Ni and a conceptual flowsheet to preconcentrate the nickel from such low grade overburden material was suggested. (orig.).

  7. Bio-reduction of Cr(VI) by exopolysaccharides (EPS) from indigenous bacterial species of Sukinda chromite mine, India. (United States)

    Harish, R; Samuel, Jastin; Mishra, R; Chandrasekaran, N; Mukherjee, A


    Chrome mining activity has contributed intensively towards pollution of hexavalent chromium around Sukinda Valley, Orissa, India. In an attempt to study the specific contribution of exopolysaccharides (EPS) extracted from indigenous isolates towards Cr(VI) reduction, three chromium (VI) tolerant strains were isolated from the effluent mining sludge. Based on the tolerance towards Cr(VI) and EPS production capacity, one of them was selected for further work. The taxonomic identity of the selected strain was confirmed to be Enterobacter cloacae (showing 98% similarity in BLAST search to E. cloacae) through 16S rRNA analysis. The EPS production was observed to increase with increasing Cr(VI) concentration in the growth medium, highest being 0.078 at 100 mg/l Cr(VI). The extracted EPS from Enterobacter cloacae SUKCr1D was able to reduce 31.7% of Cr(VI) at 10 mg/l concentration, which was relevant to the prevailing natural concentrations at Sukinda mine effluent sludge. The FT-IR spectral studies confirmed the surface chemical interactions of hexavalent chromium with EPS.

  8. An X-Ray Diffraction Study of an Inclusion in Diamond from the Luobusha Chromite Deposit in Tibet,China

    Institute of Scientific and Technical Information of China (English)

    SHI Nicheng; BAI Wenji; MA Zhesheng; FANG Qingsong; XIONG Ming; YAN Binggang; DAI Mingquan; YANG Jingsui


    Diamond was found in podiform chromitites of ophiolite and harzburgite from Luobusha, Tibet. There are silicate inclusions in some diamond grains from this area. In the present work, the CCD (charge coupled detector) technology of X-ray powder diffraction was applied to the study of the inclusion in diamond from the ophiolite of Tibet. Diffraction patterns are obtained even though the inclusion is only 20 μm in crystal size. The results show that the inclusion in diamond consists of talc and clinochrysotile. Therefore, it is clear that the diamond from the ophiolite of Luobusha, Tibet, is natural diamond rather than a synthetic one.

  9. Magnetization reversal in mixed ferrite-chromite perovskites with non magnetic cation on the A-site (United States)

    Billoni, Orlando V.; Pomiro, Fernando; Cannas, Sergio A.; Martin, Christine; Maignan, Antoine; Carbonio, Raul E.


    In this work, we have performed Monte Carlo simulations in a classical model for RFe1-x Cr x O3 with R  =  Y and Lu, comparing the numerical simulations with experiments and mean field calculations. In the analyzed compounds, the antisymmetric exchange or Dzyaloshinskii-Moriya (DM) interaction induced a weak ferromagnetism due to a canting of the antiferromagnetically ordered spins. This model is able to reproduce the magnetization reversal (MR) observed experimentally in a field cooling process for intermediate x values and the dependence with x of the critical temperatures. We also analyzed the conditions for the existence of MR in terms of the strength of DM interactions between Fe3+ and Cr3+ ions with the x values variations.

  10. Distribution of Platinum-Group Elements in Chromite Ores of the Sorkhband Ultramafic Complex, Kerman, Southeastern Iran (United States)

    Najafzadeh, Alireza; Arvin, Mohsen; Ahmadipour, Hamid; Pan, Yuanming


    The Ordovician Sorkhband ultramafic complex lies in southern Kerman Province of Iran. The wedge shape complex covers an area of more than 100 km2 and is divided into: lower part comprises of dunites, largest podiform chromitite deposits in Iran (Faryab mine), olivine clinopyroxenite dykes and massive's, wehrlite and olivine websterite dykes; and upper part comprises of clinopyroxene bearing harzburgites, with subordinate lenses and dykes of dunite, massive and dyke like olivine clinopyroxenite and minor orthopyroxenite dykes with no significant chromitite mineralization. Chromitite orebodies exhibit variable sizes and shapes, forming pods, lenses, bands, vein-like bodies and rich dissemination. Podiform chromitites in dunite form tabular to lenticular bodies although may occur also as pencil-like masses. The chromitites occur in four distinct textural modes. Massive, disseminated, banded and nodular chromitites are the most common textural types and commonly grade into one other. Massive chromitites have sharp contacts with the enclosing dunite whereas disseminated bodies grade outward into dunite and occasionally pass into interbanded chromitite and dunite. A detailed electron microprobe study reveals very high Cr#, Mg# and very low TiO2 contents for chromian spinels in chromitites. The Sorkhband chromitites contain up to 440 ppb total PGE, and display a systematic enrichment in IPGE relative to PPGE, with a steep negative slope in the PGE spidergrams and very low PPGE/IPGE ratios, a feature typical of ophiolitic podiform chromitites worldwide. The mineral chemistry data and PGE geochemistry of the chromitites indicates that the Sorkhband ultramafic complex was generated from an arc-related magma with boninitic affinity in a supra-subduction zone setting.

  11. Study of chromites YbMIICr2O5,5 (MII - Mg, Ca, Sr, Ba by X-ray diffraction

    Directory of Open Access Journals (Sweden)

    B. Kasenov


    Full Text Available Compounds of composition YbMeMnFeO5,5 (Me – Mg, Ca, Sr, Ba are synthesized from Yb2O3, , Cr2O3 and MgCO3, CaCO3, SrCO3, BaCO3 by solid phase method. X-ray powder diffraction showed that the compound YbMgCr2O5,5, YbCaCr2O5,5, YbSrCr2O5,5, YbBaCr2O5,5 crystallizes in the tetragonal crystal system.

  12. Metallographic study of heat-treated chrome ore briquettes

    Energy Technology Data Exchange (ETDEWEB)

    Patnaik, S.K.; Mohanty, J.N.; Satapathy, B.K.; Nayak, B.; Tripathy, A.K.; Dey, D.N.


    The paper deals with the metallographic study of heat treated chromite and chromite-coke composite briquettes. The briquettes, prepared from chromite concentrate of Orissa Mines using molasses-lime, dextrinelime and tamarind seed as binders, were subjected to different temperatures and examined metallographically. The change of phase with temperature was analysed by X-ray diffraction.

  13. 辽西豆荚状铬铁矿的发现及其意义%The discovery of podiform chromite in west Liaoning and its implication for plate tectonics

    Institute of Scientific and Technical Information of China (English)

    李江海; 牛向龙; 陈征; 冯军; 黄雄南


    在辽西建平新太古代变质基底构造混杂带内首次识别出豆荚状铬铁矿.铬铁矿石显示特征的豆荚状构造、褶皱条带、透镜构造、豆状构造、拉长网孔构造等,它们可以与蛇绿岩内典型的豆荚状铬铁矿进行对比.依据同位素年龄制约,辽西豆荚状铬铁矿形成于2.50Ga 前后.结合该区已报道的新太古代变基性火山岩具有大洋拉斑玄武岩成分特点、并广泛发育新太古代高压麻粒岩,可以认为辽西地区新太古代期间曾发生大规模的板块俯冲及碰撞作用过程.

  14. RH炉浸渍管用镁铬砖的损毁行为分析%Analyzing the Wear Behavior of Magnesia Chromite Brick (MKB)Used in RH Snorkel

    Institute of Scientific and Technical Information of China (English)

    陈希来; 李亚伟; 徐国涛; 薛改凤; 邹龙; 刘黎


    Used MKB in RH Snorkel of WISCO was analyzed by means of ICP-AES, XRD, optical microscope,SEM and mercury porosimetry ,and the aim is to clarify the wear behavior of MKB. The results show that adhering slag and cracks are found in the used MKB. The penetration and corrosion layer are mainly constituted by low-melting point cacoclasite and iron as well as its oxides. There is a dense layer with 40μm thickness formed between the penetration and corrosion layer and initial MKB, which mainly consists of FeO and MgO-Al2O3 spinel. The wear behavior of MKB includes two stages. Firstly, molten slag and steel can easily penetrate the open pores of MKB due to its high apparent porosity and large pore diameter,and then the penetrated slag and steel accelerate the erosion and peeling off of MKB. Thus, improving the porous characteristics will be an important route to decrease or inhibit the wear of MKB.%利用化学分析、X射线衍射仪、光学显微镜、扫描电镜及压汞仪等方法对武钢RH精炼炉浸渍管用后镁铬残砖进行了分析,旨在找出镁铬砖的损毁行为.结果表明:残砖粘渣且存有裂纹.残砖渗透、侵蚀层主要有低熔点的钙铝黄长石和铁及其氧化物;在渗透、侵蚀层与原砖层之间存在由FeO和镁铝尖晶石组成的约40 μm厚的致密过度层.镁铬砖的损毁主要包括2部分,前期主要是砖体气孔率高、气孔直径大造成的熔渣及钢水渗透,后期是渗透的熔渣及钢水加剧砖体的溶蚀及热剥落;因此改善镁铬砖的气孔特性将会成为减缓其损毁的重要途径.

  15. Photo(electro)chemical oxidation of water by the persulfate ion over aqueous suspensions of strontium titanate SrTiO3 containing lanthanum chromite LaCrO3

    NARCIS (Netherlands)

    Thewissen, D.H.M.W.; Timmer, K.; Eeuwhorst‐Reinten, M.; Tinnemans, A.H.A.; Mackor, A.


    The photodecomposition of the S2O2‐ 8 ion to the SO2‐ 4 ion with concomitant oxidation of water to molecular oxygen over n‐type SrTiO3 powders mixed with LaCrO3 (mole fraction x = 0–1), using UV light (λ > 300 nm), is considerably faster than the photochemical (UV) decomposition of S2O2‐ 8 in water

  16. 超基性岩矿物化学特征与成矿关系讨论

    Institute of Scientific and Technical Information of China (English)



    The most productive chromite ore deposits are formed by crystallizing from chromite-ore magmas under definite physico-chemical conditions. The formation of chromite ore is controlled mainly by the degree of differentiation of ultrabasic magma. How to diagnose uitrabasic magmatie differentiation is key to the understanding of the mechanism of formation of chromite ore. It is considered that chromite ore is derived from ulttabasic rocks. The rock-forming minerals include olivine, pyroxene and spinel. The minerals are well homomorphous minerals. The contents of major chemical elements in these minerals show little variation. On the contrary in those ultrubasie rocks which show no association with chromite ore deposits the contents of the elements vary over a wide range. Abundant data available.indicate that chromite ore deposits arc derived from chrore.ire-ore magmas resulting from the transport and accumulation of chromic elements. Since the transport and accumulation of chromic elements follows the statistical law,we must study the mechanism of formation of ehromite ore from the statistical point of view. If chromite ore is formed from spinel under the action of gravitation o.r other dynamic actions, we must elucidate the mechanism of formation of chromite ore from the dynamic viewpoint.

  17. 48 CFR 25.104 - Nonavailable articles. (United States)


    .... Chalk, English. Chestnuts. Chicle. Chrome ore or chromite. Cinchona bark. Cobalt, in cathodes, rondelles..., blocks, and pigs. Triprolidine hydrochloride. Tungsten. Vanilla beans. Venom, cobra. Water chestnuts....

  18. Mekanik aktive edilmiş kromitin grafitle karbotermal redüksiyon kinetiği


    Yıldız, Kenan


    The carbothermal reduction kinetics of mechanically activated chromite with graphite under an argon atmosphere was investigated at temperatures between 1100 and 1400°C. Zhuravlev-Lesokhin-Tempelman (ZLT) method was used in the reduction kinetics for non-activated chromite and the activation energy was calculated as 401.7 kJ/mol. Solid-state diffusion method was used in the reduction kinetics for 60 min-activated chromite and the activation energy was calculated as 283.3 kJ/mol. This decrease ...

  19. Effects of Zirconium Silicate and Chromite Addition on the Microstructure and Bulk Density of Magnesia-magnesium Aluminate Spinel-based Refractory Materials%硅酸锆和铬铁矿添加物对MgO-镁铝尖晶石耐火材料性能的影响

    Institute of Scientific and Technical Information of China (English)





    Institute of Scientific and Technical Information of China (English)

    王超会; 刘剑虹; 顾晓华; 赵家林


    1800℃高温电炉是材料研究过程中重要的高温设备,在本文中通过对铬酸镧加热元件的性能分析,扬长避短,采用电阻丝与铬酸镧加热棒共同作为热源的双加热系统,设计了合理可行的高温耐热和和隔热材料,并进行了升温性能的测定,以及最大温升速度的测定,得出了该高温炉的基本性能.%1800 ℃ high temperature furnace is an important high temperature equipment of material process.In this paper the properties of lanthanum chromium heating elements was analyzed to advantage,using nickel-chromium resistance wire and lanthanum chromium stick together as the double heating system.Reasonable feasible high-temperature and insulation materials were designed, and the performance testing of temperature and the determination of the maximum temperature rise rate were conducted, then the basic properties of the high-temperature furnace was obtained.

  1. The I-Xe System in the IVA Iron Meteorite Steinbach (United States)

    Pravdivtseva, O.; Meshik, A.; Hohenberg, C. M.


    Non-metallic phases from IVA Steinbach were separated and identified to be troilite, chromite, tridymite, and clino- and orthopyroxene. Xenon isotopic compositions are measured to identify possible iodine carrier phases suitable for the I-Xe dating.

  2. A Stranger in the Midst: Searching for Relict Grains from Rare Meteorite Types in Mid-Ordovician Limestone Strata (United States)

    Martin, E.; Schmitz, B.


    A layer of Mid-Ordovician limestone harbors exceptional amounts of L-chondritic chromite grains. The layer also contains grains from potentially rarer types of meteorites, following the discovery of the fossil meteorite Österplana 065.

  3. Extraterrestrial components from deep sea sediments of Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rudraswami, N.G.; ShyamPrasad, M.

    chondrites to be major contributors. In addition, relict chromite grains and dusty olivines observed in several cosmic spherules suggested that at least 3% of the cosmic material that rains on the earth is sourced from ordinary chondrites. The Australasian...

  4. Boundaries of intergrowths between mineral individuals: A zone of secondary mineral formation in aggregates (United States)

    Brodskaya, R. L.; Bil'Skaya, I. V.; Lyakhnitskaya, V. D.; Markovsky, B. A.; Sidorov, E. G.


    Intergrowth boundaries between mineral individuals in dunite of the Gal’moenan massif in Koryakia was studied in terms of crystal morphology, crystal optics, and ontogenesis. The results obtained allowed us to trace the staged formation of olivine and chromite and four generations of these minerals. Micro-and nanotopography of boundary surfaces between intergrown mineral individuals of different generations was examined with optic, electron, and atomic force microscopes. The boundaries between mineral individuals of different generations are distinguished by their microsculpture for both olivine and chromite grains. Both minerals demonstrate a compositional trend toward refinement from older to younger generations. The decrease in the iron mole fraction in olivine and chromite is accompanied by the crystallization of magnetite along weakened zones in olivine of the first generation and as outer rims around the chromite grains of the second generation observable under optic and electronic microscopes. The subsequent refinement of chromite results in the release of PGE from its lattice, as established by atomic power microscopy. The newly formed PGM are localized at the boundaries between mineral individuals and, thus, mark a special stage in the ontogenetic evolution of mineral aggregates. Further recrystallization is expressed in the spatial redistribution of grain boundaries and the formation of monomineralic intergrowth boundaries, i.e., the glomerogranular structure of rock and substructures of PGM, chromite, and olivine grains as intermediate types of organization of the granular assemblies in the form of reticulate, chain, and cellular structures and substructures of aggregates.

  5. Two step, PID and model predictive control using artificial neural network applied on semi-batch reactor


    Macků, Lubomír; Sámek, David


    Článek se zabývá řízením polodávkového reaktoru používaného v procesu recyklace chromitého odpadu enzymatickou hydrolýzou. Chromitý odpad pochází z procesu chromočinění při zpracování přírodní kůže. Recyklační technika odděluje chrom od proteinu ve formě chromitého filtračního koláče. Všechny produkty tohoto procesu jsou dále využitelné, jedná se tedy o bezodpadní technologii. V reaktoru dochází k opakovanému využití chromitého kalu (chromitého filtračního koláče). Regulace polodávkového reak...

  6. 河南某铬铁矿床中铬尖晶石蚀变的地球化学研究

    Institute of Scientific and Technical Information of China (English)



    In the light of mineral assemblages, mineralogical generation and genesis of chromite ores, some geochemical aspects are investigated with respect to . relative abundance, the transportion and association mechanisms of Cr and related elements in the process of metasomatie alteration of primary chromian spinel during migmatization. The formation of Fe-chromite is a result of metasomatism from primary magnesian Al-chromite through ultrametamorphism. A knowledge of its chemical characteristics will not only be desirable to understanding the chemistry of the oreforming fluid during later metasomatism, but also provide valuable informatinns as to the transport of Cr and some other points concerning geochemical evolution. Critical influence of SiO2 and Al2O3 concentrations has been recognized upon the enrichment and dispersion of Cr in the course of ultrametamorphism.

  7. Synthesis of chromium and ferrochromium alloy in molten salts by the electro-reduction method

    Directory of Open Access Journals (Sweden)

    Ge X.


    Full Text Available In this work, we successfully applied the Fray-Farthing-Chen Cambridge electro-reduction process on the preparation of chromium from chromium oxide, and for the first time, the synthesis of ferrochromium alloy from chromium oxide and iron oxide mixture and the chromite ore in molten calcium chloride. The present work systematically investigated the influences of sintered temperature of the solid precursor, electrochemical potential, electrolysis temperature and time on the products by using a set of advanced characterization techniques, including XRD and SEM/EDS analyses. In particular, our results show that this process is energy-friendly and technically-feasible for the direct extraction of ferrochromium alloy from chromite ore. Our findings thus provide useful insights for designing a novel green process to produce ferrochromium alloy from low-grade chromite ore or stainless steel slag.

  8. Stability of solid oxide fuel cell materials

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, T.R.; Bates, J.L.; Coffey, G.W.; Pederson, L.R. [Pacific Northwest National Lab., Richland, WA (United States)] [and others


    Chromite interconnection materials in an SOFC are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. Because such conditions could lead to component failure, the authors have evaluated thermal, electrical, chemical, and structural stabilities of these materials as a function of temperature and oxygen partial pressure. The crystal lattice of the chromites was shown to expand for oxygen partial pressures smaller than 10{sup {minus}10} atm, which could lead to cracking and debonding in an SOFC. Highly substituted lanthanum chromite compositions were the most susceptible to lattice expansion; yttrium chromites showed better dimensional stability by more than a factor of two. New chromite compositions were developed that showed little tendency for lattice expansion under strongly reducing conditions, yet provided a good thermal expansion match to other fuel cell components. Use of these new chromite interconnect compositions should improve long-term SOFC performance, particularly for planar cell configurations. Thermodynamic properties of substituted lanthanum manganite cathode compositions have been determined through measurement of electromotive force as a function of temperature. Critical oxygen decomposition pressures for Sr and Ca-substituted lanthanum manganites were established using cells based on a zirconia electrolyte. Strontium oxide and calcium oxide activities in a lanthanum manganite matrix were determined using cells based on strontium fluoride and calcium fluoride electrolytes, respectively. The compositional range of single-phase behavior of these ABO{sub 3}-type perovskites was established as a function of A/B cation ratios and the extent of acceptor doping. Before this work, very little thermodynamic information was in existence for substituted manganite compositions. Such information is needed to predict the long-term stability of solid oxide fuel cell assemblies.

  9. High resolution seismic reflection, an exploration tool within an underground environment (example from Zimbabwe) (United States)

    Mutyorauta, J. J.

    Metallurgical grade chromite ore in Zimbabwe is mined from two underground mines, Peak Mine and Railway Block Mine, in Shurugwi. Peak Mine is at present just over 800 m deep. In the search for new chromite ore bodies, such a depth limits the application of the conventional geophysical exploration tools. Exploration diamond drilling is becoming more and more an expensive resort. Alternative and effective geophysical techniques are therefore being actively sought after. The high resolution seismic reflection technique, carried out right within Peak Mine, has the potential to become a useful exploration tool.

  10. A Silicate Inclusion in Puente del Zacate, a IIIA Iron Meteorite (United States)

    Olsen, Edward J.; Davis, Andrew M.; Clayton, Robert N.; Mayeda, Toshiko K.; Moore, Carleton B.; Steele, Ian M.


    The IIIA and IIIB iron meteorites are considered to have formed in the cores of asteroids. A silicate inclusion within the IIIA meteorite Puente del Zacate consisting of olivine (Fa_4), low-calcium pyroxene (Fs_6Wo_1), chromium diopside (Fs_3Wo47), plagioclase (An14Or_4), graphite, troilite, chromite, daubreelite, and iron metal resembles inclusions in IAB iron meteorites. The oxygen isotopic composition of the Puente del Zacate inclusion is like chromite and phosphate inclusions in other IIIA and IIIB irons. The Puente del Zacate inclusion may have been derived from the lower mantle of the IIIAB parent asteroid.

  11. Exsolutions of Diopside and Magnetite in Olivine from Mantle Dunite, Luobusa Ophiolite, Tibet, China

    Institute of Scientific and Technical Information of China (English)

    REN Yufeng; CHEN Fangyuan; YANG Jingsui; GAO Yuanhong


    The exsolutions of diopside and magnetite occur as intergrowth and orient within olivine from the mantle dunite, Luobusa ophiolite, Tibet. The dunite is very fresh with a mineral assemblage of olivine (>95%) + chromite (1%-4%) + diopside (<1%). Two types of olivine are found in thin sections: one (Fo = 94) is coarse-grained, elongated with development of kink bands, wavy extinction and irregular margins; and the other (Fo = 96) is fine-grained and poly-angled. Some of the olivine grains contain minor Ca, Cr and Ni. Besides the exsolutions in olivine, three micron-size inclusions are also discovered. Analyzed through energy dispersive system (EDS) with unitary analytical method, the average compositions of the inclusions are: Na20, 3.12%-3.84%; MgO, 19.51%-23.79%; Al2O3,9.33%-11.31%; SiO2, 44.89%-46.29%; CaO, 11.46%-12.90%; Cr2O3, 0.74%-2.29%; FeO, 4.26%-5.27%, which is quite similar to those of amphibole. Diopside is anhedral filling between olivines, or as micro-inclusions oriented in olivines. Chromite appears euhedral distributed between olivines,sometimes with apparent compositional zone. From core to rim of the chromite, Fe content increases and Cr decreases; and Al and Mg drop greatly on the rim. There is always incomplete magnetite zone around the chromite. Compared with the nodular chromite in the same section, the euhedral chromite has higher Fe3O4 and lower MgCr2O4 and MgAl2O4 end member contents, which means it formed under higher oxygen fugacity environment. With a geothermometer estimation, the equilibrium crystalline temperature is 820℃-960℃ for olivine and nodular chromite, 630℃-770℃ for olivine and euhedral chromite, and 350℃-550℃ for olivine and exsoluted magnetite, showing that the exsolutions occurred late at low temperature. Thus we propose that previously depleted mantle harzburgite reacted with the melt containing Na, Al and Ca, and produced an olivine solid solution added with Na+,Al3+, Ca2+, Fe3+, Cr3+. With temperature

  12. Cr-Bearing Inclusions in IVA Irons: Implication for Cr and Volatile Behaviors in the Metallic Cores (United States)

    Isa, J.; McKeegan, K. D.; Wasson, J. T.


    We found inclusions that contribute to bulk Cr concentrations and found fO2 or fS2 changes during crystallization. O-isotope compositions of chromite are mass-dependently lighter than other IVA oxides. Also, we discovered a new mineral MnCr2S4.


    Institute of Scientific and Technical Information of China (English)


    <正>20102341 Bao Peisheng(Institute of Geology,Chinese Academy of Geological Science,Beijing 100037,China)Further Discussion on the Genesis of the Podiform Chromite Deposits in the Ophiolites-Questioning about the Rock:Melt Interaction Metallogeny(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,28(12),2009,p.1741-1761

  14. Chondritic osmium isotopic composition of late Archean convecting upper mantle:Evidence from Zunhua podiform chromitites, Hebei, North China

    Institute of Scientific and Technical Information of China (English)

    XIA Qiongxia; ZHI Xiachen; LI Jianghai; HUANG Xiongnan


    Podiform chromite deposits are a characteristic feature of the mantle sequences of harzburgitic ophiolites. The chromites usually have very low Re and high Os contents, which makes it the most resistant phase remaining from the primary magmatic history of the ultramafic sections of ophiolites. The podiform chromite is one of the robust indicators of initial Os isotopic compositions of the ophiolites where podiform chromites were derived from, which provides strong evidence for the origin and evolution of oceanic lithosphere. The Re and Os contents and the Os isotopic compositions of seven podiform chromitites from Zunhua ophiolitic mélange belt, North China are reported in this study. The Re contents range from 0.019 to 0.128 ng/g, Os from 8.828 to 354.0 ng/g, and the 187Os/188Os ratio from 0.11003 to 0.11145. Three massive chromitites among the sample set have very high Os contents (>300 ng/g), and their 187Os/188Os ratios range from 0.11021 to 0.11030, averaging 0.11026 ± 0.00005 (σ), equivalent to a γOs = -0.12 ± 0.06 at 2.6 Ga, which means that the Os isotopic composition of convecting upper mantle is chondritic in late Archean. It is the Os isotopic composition of podiform chromitites that are derived from the oldest ophiolite in the world till now.

  15. Platinum-Group Minerals in Chromitites of the Niquelândia Layered Intrusion (Central Goias, Brazil: Their Magmatic Origin and Low-Temperature Reworking during Serpentinization and Lateritic Weathering

    Directory of Open Access Journals (Sweden)

    Nelson Angeli


    Full Text Available A variety of platinum-group-minerals (PGM have been found to occur associated with the chromitite and dunite layers in the Niquelândia igneous complex. Two genetically distinct populations of PGM have been identified corresponding to phases crystallized at high temperatures (primary, and others formed or modified during post-magmatic serpentinization and lateritic weathering (secondary. Primary PGM have been found in moderately serpentinized chromitite and dunite, usually included in fresh chromite grains or partially oxidized interstitial sulfides. Due to topographically controlled lateritic weathering, the silicate rocks are totally transformed to a smectite-kaolinite-garnierite-amorphous silica assemblage, while the chromite is changed into a massive aggregate of a spinel phase having low-Mg and a low Fe3+/Fe2+ ratio, intimately associated with Ti-minerals, amorphous Fe-hydroxides, goethite, hematite and magnetite. The PGM in part survive alteration, and in part are corroded as a result of deep chemical weathering. Laurite is altered to Ru-oxides or re-crystallizes together with secondary Mg-ilmenite. Other PGM, especially the Pt-Fe alloys, re-precipitate within the altered chromite together with kaolinite and Fe-hydroxides. Textural evidence suggests that re-deposition of secondary PGM took place during chromite alteration, controlled by variation of the redox conditions on a microscopic scale.

  16. Controlled reactions between chromia and coating on alloy surface

    DEFF Research Database (Denmark)

    Linderoth, Søren


    An electrically conducting Sr-doped lanthanum chromite (LSC) coating has been produced by reacting a coating of fine particles of La oxide and Sr oxide with chromia formed as an external scale on a metallic alloy. In addition to the formation of LSC the coating also resulted in much reduced...... buckling of the underlying chromia layer compared with a non-coated alloy....

  17. Domestic Production Issues in Chromium and Platinum-Group Metals (United States)


    Protection Agency. OPA 87-005. Washington: Government Printing Office, May 1987. 16. Foley, Jeffrey Y. and James C. Barker . Chromite Deposits Along...Mining, Metallurgical, and Petroleum Engineers, 1976. 52. Stowe, Clive W. Evolution of Chromium Ore Fields. New York: Van Nostrand Reinhold Company

  18. Five Major State-Level Copper,Lead, Zinc Resource Succession Bases in Tibet Have Initially Taken Shape

    Institute of Scientific and Technical Information of China (English)


    According to the Chengdu Center of China Geological Survey,five major state-level copper-lead-zinc resource succession bases in Tibet have initially taken shape,featuring tremendous resource potentials.It has been learned that these five major resource succession bases are respectively copper-lead-zinc molybdenum iron prospecting development base in Central Tibet,chromite

  19. The Preparation and Characterization of Materials. (United States)

    Wold, Aaron


    Presents several examples illustrating different aspects of materials problems, including problems associated with solid-solid reactions, sintering and crystal growth, characterization of materials, preparation and characterization of stoichiometric ferrites and chromites, copper-sulfur systems, growth of single crystals by chemical vapor…

  20. Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions (United States)

    Wiggers de Vries, D. F.; Drury, M. R.; de Winter, D. A. M.; Bulanova, G. P.; Pearson, D. G.; Davies, G. R.


    As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beam-scanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond have similar crystallographic orientations to the host, within ±0.4°. The chromite inclusions record a systematic change in Mg# and Cr# from core to the rim of the diamond that corresponds with a ~80°C decrease of their formation temperature as established by zinc thermometry. A chromite inclusion, positioned adjacent to a boundary between two major diamond growth zones, is multi-faceted with preferred octahedral and cubic faces. The chromite is surrounded by a volume of non-luminescent diamond (CL halo) that partially obscures any diamond growth structures. The CL halo has apparent crystallographic morphology with symmetrically oriented pointed features. The CL halo is enriched in ~200 ppm Cr and ~80 ppm Fe and is interpreted to have a secondary origin as it overprints a major primary diamond growth structure. The diamond zonation adjacent to the chromite is complex and records both syngenetic and protogenetic features based on current inclusion entrapment models. In this specific case, a syngenetic origin is favoured with the complex form of the inclusion and growth layers indicating changes of growth rates at the diamond-chromite interface. Combined EBSD and 3D-CL imaging appears an extremely useful tool in resolving the ongoing discussion about the timing of inclusion growth and the significance of diamond inclusion studies.

  1. High carbon ferro-chromium by self-reducing process: Fundamentals

    Directory of Open Access Journals (Sweden)

    Adolfo Pillihuaman Zambrano


    Full Text Available Fe-Cr-C production is a very high electrical energy consuming process. When self-reducing agglomerates are used,it is expected to reduce up to 10% of this electrical energy. This paper presents the fundamental aspects of the reactions involved for reduction of chromites from self-reducing agglomerates. Brazilian chromite containing 41.2%Cr2O3 was mixed with petroleum coke and agglomerated with cement as the binder. The concept of “initial slag” was introduced and it was assumed that this “initial slag” is formed by fluxing agents, coke ash, silica, binder and only dissolution of 5% of the gangue from the chromite. This concept is important since the gangue of chromite is composed mainly of refractory oxides (MgO+Al2O3, which are difficult to dissolve into slag. The effects of “initial slag” composition, one with low liquidus temperature(~1700K and other with high liquidus temperature (~1750K were investigated. The mixture was pelletized, dried and submitted to a temperature of 1773K until completion of the reaction. The reaction fraction as a function of time was determined. The results show that pellets containing components with liquid slag phase formed at higher temperature presented significant better reduction behavior than pellet with the liquid slag phase formed at lower temperature. The scanning electron microscopy analysis showed that a liquid phase was formed but the pellet did not collapse and indicated that thecoalescence of the metallic phase depends on the dissolution of the pre-reduced particles of the chromite into slag.

  2. Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells (United States)

    Zhong, Zhi-Min; Goldsby, Jon C.


    Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the

  3. The Cedrolina Chromitite, Goiás State, Brazil: A Metamorphic Puzzle

    Directory of Open Access Journals (Sweden)

    Yuri de Melo Portella


    Full Text Available The Cedrolina chromitite body (Goiás-Brazil is concordantly emplaced within talc-chlorite schists that correspond to the poly-metamorphic product of ultramafic rocks inserted in the Pilar de Goiás Greenstone Belt (Central Brazil. The chromite ore displays a nodular structure consisting of rounded and ellipsoidal orbs (up to 1.5 cm in size, often strongly deformed and fractured, immersed in a matrix of silicates (mainly chlorite and talc. Chromite is characterized by high Cr# (0.80–0.86, high Fe2+# (0.70–0.94, and low TiO2 (av. = 0.18 wt % consistent with variation trends of spinels from metamorphic rocks. The chromitite contains a large suite of accessory phases, but only irarsite and laurite are believed to be relicts of the original igneous assemblage, whereas most accessory minerals are thought to be related to hydrothermal fluids that emanated from a nearby felsic intrusion, metamorphism and weathering. Rutile is one of the most abundant accessory minerals described, showing an unusually high Cr2O3 content (up to 39,200 ppm of Cr and commonly forming large anhedral grains (>100 µm that fill fractures (within chromite nodules and in the matrix or contain micro-inclusions of chromite. Using a trace element geothermometer, the rutile crystallization temperature is estimated at 550–600 °C (at 0.4–0.6 GPa, which is in agreement with P and T conditions proposed for the regional greenschist to low amphibolite facies metamorphic peak of the area. Textural, morphological, and compositional evidence confirm that rutile did not crystallize at high temperatures simultaneously with the host chromitite, but as a secondary metamorphic mineral. Rutile may have been formed as a metamorphic overgrowth product following deformation and regional metamorphic events, filling fractures and incorporating chromite fragments. High Cr contents in rutile very likely are due to Cr remobilization from Cr-spinel during metamorphism and suggest that Ti was

  4. A New Martian Meteorite from Antarctica:Grove Mountains (GRV) 020090

    Institute of Scientific and Technical Information of China (English)

    MIAO Bingkui; OUYANG Ziyuan; WANG Daode; JU Yitai; WANG Guiqin; LIN Yangting


    Reported in this paper are the petrology and mineral chemistry of GRV 020090, the second Martian meteorite collected from the Grove Mountains, Antarctica. This meteorite, with a mass of 7.54 g, is completely covered by a black and glazy fusion crust. It has two distinct textural regions. The interstitial region is composed of euhedral grains of olivine,pigeonite, and anhedral interstitial maskelynite, with minor chromite, augite, phosphates and troilite. The poikilitic region consists of three clasts of pyroxenes, each of which has a pigeonite core and an augite rim. A few grains of subhedral to rounded olivine and euhedral chromite are enclosed in the pyroxene oikocrysts. GRV 020090 is classified as a new member of lherzolitic shergottites based on the modal composition and mineral chemistry. This work will shed light on the composition of Martian crust and magmatism on the Mars.

  5. Chvorinov’s rule and determination of coefficient of heat accumulation of moulds with non-quartz base sands

    Directory of Open Access Journals (Sweden)

    T. Elbel


    Full Text Available Application of the „Chvorinov’s rule“ for calculation of the total time of casting solidification made also possible to determine chilling effect of foundry moulds (coefficient of heat accumulation of the mould, bf with use of mixtures with new kinds of non-quartz base sands (Magnesite, Chromite, Olivine, Dunite, Kerphalit. Processes by several authors (G. Halbart, A. I. Vejnik, G. A. Anisovich were used for mathematical treatment of measurement results and determination of bf. The highest values were achieved for magnesite moulds followed by chromite ones; the lowest values, approximately half-ones, represented the Dunite moulds. At the same time the results made possible to determine „the Chvorinov’s mean solidification constants“ (k that are in direct proportional dependence on bf and indirect proportional to solidification time (τ1.

  6. Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

    Directory of Open Access Journals (Sweden)



    Full Text Available Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite or compositional (e.g. mantle spinel remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite facies along 100 m-wide shear zones, followed by intense serpentinization (M3 and narrow 1-3 m-wide shear zones (M4 containing asbestos.

  7. Synthesis of Nanocrystalline La1-xSrxCrO3 by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    Ao Qing; Zhao Xinming; Li Dehui; Sun Liangcheng


    The nanocrystalline La1-xSrxCrO3 was prepared by sol-gel method using La( NO3 )3 · 6H2O, Sr( NO3 )2 and respectively. The phase transformation from dry-gel to crystal was investigated by means of TG, DSC and XRD. Influences of temperature and Sr quantity on particle-diameters were observed by HREM. The experimental results show that the best calcined temperature is near 800 ℃. The particle-diameters decrease with the increase of Sr quantity. The chromite phase formed continuously during crystallization process, which is mainly composed of four steps: ( 1 ) Carbonates first formed by decomposing metal citrates. (2) The decomposition of carbonates occurred metal oxides. (3) La0. 9Sr0.1 CrO4 were synthesized by the reaction of metal oxides. (4) Chromite phase formed lastly due to the decomposition of chromate phase.

  8. Magnetic Behavior of Some Rare-Earth Transition-Metal Perovskite Oxide Systems

    Institute of Scientific and Technical Information of China (English)

    Kenji Yoshii; Akio Nakamura; Masaichiro Mizumaki; Naoshi Ikeda; Jun'ichiro Mizuki


    Magnetic properties were investigated for the rare-earth 3d-transition metal oxides with the perovskite structure. Intriguing magnetic phenomena were reviewed for a few systems:magnetization peak effect in the titanates, magnetization reversal in the chromites and metallic ferromagnetism in the cobaltites. The results suggest an important role of the rare-earth ions for the magnetic properties of such complex oxides.

  9. Stability of solid oxide fuel cell materials

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, T.R.; Bates, J.L.; Chick, L.A. [Pacific Northwest Lab., Richland, WA (United States)


    Interconnection materials in a solid oxide fuel cell are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. The thermal expansion characteristics of substituted lanthanum and yttrium chromite interconnect materials were evaluated by dilatometry as a function of oxygen partial pressures from 1 atm to 10{sup -18} atm, controlled using a carbon dioxide/hydrogen buffer.

  10. Conditions of stichtite (Mg6Cr2(OH)16[CO3]·4H2O) formation and its geochemical and isotope record of early phanerozoic serpentinizing environments (United States)

    Melchiorre, Erik B.; Bottrill, Ralph; Huss, Gary R.; Lopez, Amanda


    Stichtite is a magnesium-chromium hydroxycarbonate mineral found in association with early Phanerozoic chromite-rich serpentinite rocks of Tasmania, Australia and Tehuitzingo, Mexico. Elemental analysis of stichtite shows a range of compositions within the Cr-Fe-Al hydrotalcite group, with compositional trends associated with each discrete serpentinite host body. Elemental and textural analysis of stichtite-associated chromite indicates that stichtite forms in fore-arc setting rocks through interaction of chromite and methane-rich serpentinizing fluids. The degree to which chromite is replaced by stichtite is inferred to correlate with the length of time that the host rocks spent within the "stichtite window." Carbon stable-isotope analyses of stichtite suggest carbon sourcing from marine kerogen with a minor marine carbonate component in some samples. The carbon and hydrogen stable isotope profile of stichtite ranges from the field of methane from active serpentinizing zones, to organic thermogenic methane. The association of the stichtite 2H polytype (nee barbertonite) with aragonite ± antigorite suggests this is a higher pressure/temperature polytype of stichtite. Reaction completion textures, isotopic values, and qualitative mineral thermobarometric indicators indicate that stichtite forms during serpentinization of fore-arc setting rocks in a methane/H2-rich environment within fluid conduits, ranging from low temperatures and pressures near the surface, to depths where pressure is up to 0.8-1.2 GPa and temperature is up to ∼300 °C. These unique chemical, isotopic, and textural properties of stichtite from distinct serpentinite bodies likely record the duration of serpentinization at specific thermobarometric conditions, and provide a window into the conditions associated with a potentially habitable environment on early Earth and other bodies of the solar system.

  11. 菲律宾采矿业期待腾飞%Philippines's Mining Industry Awaiting Prosperity

    Institute of Scientific and Technical Information of China (English)



    Because of its favorable location, the Philippines possess sufficient natural mineral materials according to its relatively small territory. The Philippines used to be one of the top 10 world producers of copper, gold, nickel and chromites in the 1980s. Since then, however, its mining industry has steadily deteriorated owing to some reasons. This essay probes into the process of its development, its drawbacks and its prospect.

  12. Meteorite Seymchan structure (United States)

    Hontsova, S. S.; Petrova, E. V.; Muftahetdinova, R. F.; Chulanova, V. N.; Grokhovsky, V. I.


    The meteorite Seymchan specimen was studied using optical microscopy and scanning electron microscopy. Olivine grains have roundish shapes, which was formed during matter cooling. Different features of the metal structure such as plessite structure and Neimann bands were observed. The oxide edges were observed in the boundaries between phases. The oxides were formed in the terrestrial conditions. The boundary regions between metal and olivine in the meteorite contain grains of troilite, schreibersite, and chromite.

  13. Mineral resource potential of the Stillwater Complex and adjacent rocks in the northern part of the Mount Wood and Mount Douglas quadrangles, southwestern Montana (United States)

    Page, Norman J; Dohrenwend, John C.


    The Stillwater Complex contains the largest potential chromite and platinum metal resources and second largest nickel resources in the United States. The Ultramafic zone has produced about 900,000 long tons of chromite concentrate and contains unmined reserves equivalent to 2,520,000 long tons of Cr2O3. Nickel and copper sulfide minerals that occur in the Basal zone and adjacent hornfelsed metasedimentary rocks represent one of the largest nickel potentials in the United States---a known reserve of 150 million tons of 0.25 percent nickel and 0.25 percent copper. The complex has been estimated to contain the largest potential source of platinum metals in the United States---possibly over 150 million troy ounces in the lower chromite zones and the Basal zone. In addition, the anorthosites in the Banded and Upper zones are reported to represent a potential alumina resource of almost 2 billion tons. An iron-formation also is present in the adjacent Precambrian metasedimentary rocks, and a coal bed is present in the Upper Cretaceous Eagle Sandstone nearby. The eventual utilization of these resources depends on the availability of large quantities of energy, and thus they may not be recovered unless new sources of energy or new recovery techniques are developed.

  14. Development of regenerable copper-based sorbents for hot gas cleanup. Technical report, September 1, 1995--November 30, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Slimane, R.B.; Hill, A.H. [Institute of Gas Technology, Chicago, IL (United States)


    The overall objective of this study is to determine the effectiveness of the copper-chromite sorbent (developed in previous ICCI-funded projects) for longer duration application under optimum conditions in the temperature range of 550{degrees}-650{degrees}C to minimize sorbent reduction and degradation during the cyclic process. To achieve this objective, several formulations of copper chromite sorbents are prepared. These sorbent formulations are screened for their desulfurization and regeneration capability at predetermined temperatures and gas residence times. The durability of the best sorbent formulation identified in the screening tests is evaluated in ``long-term`` durability tests conducted at the optimum operating conditions. This includes testing the sorbent in pellet and granular forms in packed- and fluidized-bed reactors. During this quarter, twenty one copper chromite-based sorbent formulations were prepared. Two sorbent formulations that have acceptable crush strength, designated as CuCr-10 and CuCr-21, were tested over 5 and 6 cycles respectively. The results indicate that both sorbents are reactive toward H{sub 2}S at 650{degrees}C and that the reactivity of the sorbents are relatively constant over the first 5 to 6 cycles. The H{sub 2}S prebreakthrough concentrations were generally about 20 to 30 ppm, making them suitable for IGCC application.

  15. Diamond exploration and mantle structure imaging using PIXE microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, C.G.; Griffin, W.L.; Win, T.T. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience


    Geochemical methods of diamond exploration rely on recognizing indicator minerals that formed in the earth`s upper mantle, within the diamond stability field, and were entrained in rapidly rising volatile-rich magmas and emplaced in or on the crust. Diamond is only stable at high pressure. Therefore, diamond exploration commonly targets prospects containing high pressure minerals, such as low-Ca, high-Cr (`G10`) garnets and high-Cr chromites, similar to inclusions in diamonds. However, this procedure can be ambiguous; some barren pipes contain abundant `G10` garnets. while such garnets are extremely rare in the Argyle pipe, the world`s largest diamond producer. Similarly, high-Cr chromites are shed by a wide variety of barren rock types. PIXE microanalysis of trace elements in concentrate garnets and chromites from kimberlites and other volcanic rocks helps to remove the ambiguities by pinning down the source temperature (T), pressure (P) and local (paleo)geotherm (P-T relation), which permits the rich store of trace element information in these minerals, reflecting rock chemistry and metasomatic processes, to be placed in a stratigraphic context. 11 refs., 4 figs.

  16. Petrological, geochemical and isotopic characteristics of the Collo ultramafic rocks (NE Algeria) (United States)

    Laouar, Rabah; Satouh, Adel; Salmi-Laouar, Sihem; Abdallah, Nachida; Cottin, Jean-Yves; Bruguier, Olivier; Bosch, Delphine; Ouabadi, Aziouz; Boyce, Adrian J.; Fallick, Anthony E.


    The ultramafic rocks of the Collo region in northeastern Algeria crop out as "stratified" masses that cut across older metamorphic formations of the Petite Kabylie basement. Based on petrological compositions and mineralogical observations, these rocks are mainly peridotites and serpentinites. The peridotites are identified as lherzolites, but dunites may occur rarely. The lherzolites are composed of olivine, orthopyroxene, clinopyroxene and chromian spinel. Their chemical composition shows high MgO (34.4-37.5 wt%), Cr (0.14-0.27 wt%), Ni (0.14-0.26 wt%) and Co (34-133 ppm) contents and low CaO and Al2O3 concentrations (0.02-2.2 wt% and 0.5 to 2.8 wt%, respectively). The chromite, which represents approximately 1-3% of the rock, is ubiquitous and shows two different generations: primary millimetric euhedral crystals and secondary fine xenomorphic grains and interstitial aggregates. The primary chromites are alumino-ferro-magnesian crystals that show high Al2O3 (25.77%-27.36%) and MgO (10.70%-13.36%). Cr# (100 × Cr/(Al + Cr)) ranges from 45 to 48, and Mg# (100 × Mg/(Mg + Fe2+)) from 49 to 59. The secondary interstitial grains are iron-rich chromites. They show low Al2O3 (4.67%-9.54%) and MgO (4.60%-4.65%). Cr# is relatively high (77-88), whereas Mg# shows relatively low values, ranging from 22 to 25. Primary chromite and whole-rock chemistry show that the Collo ultramafic rocks belong to Alpine-type peridotites that were emplaced within an orogenic setting. The oxygen isotopic composition of both peridotites and chromites is consistent with their derivation from a mantle source (δ18O ranges from +3.0 to +5.9‰). Low δ18O values (<+4.4‰) are recorded in serpentinites and are attributed to the effect of serpentinization processes through high-temperature metasomatic fluids. Magnesite-bearing serpentinites show the lowest δ18O values. These are interpreted as the result of surface water input.

  17. Formation and modification of chromitites in the mantle (United States)

    Arai, Shoji; Miura, Makoto


    Podiform chromitites have long supplied us with unrivaled information on various mantle processes, including the peridotite-magma reaction, deep-seated magmatic evolution, and mantle dynamics. The recent discovery of ultrahigh-pressure (UHP) chromitites not only sheds light on a different aspect of podiform chromitites, but also changes our understanding of the whole picture of podiform chromitite genesis. In addition, new evidence was recently presented for hydrothermal modification/formation chromite/chromitite in the mantle, which is a classical but innovative issue. In this context, we present here an urgently needed comprehensive review of podiform chromitites in the upper mantle. Wall-rock control on podiform chromitite genesis demonstrates that the peridotite-magma reaction at the upper mantle condition is an indispensable process. We may need a large system in the mantle, far larger than the size of outcrops or mining areas, to fulfill the Cr budget requirement for podiform chromitite genesis. The peridotite-magma reaction over a large area may form a melt enriched with Na and other incompatible elements, which mixes with a less evolved magma supplied from the depth to create chromite-oversaturated magma. The incompatible-element-rich magma trapped by the chromite mainly precipitates pargasite and aspidolite (Na analogue of phlogopite), which are stable under upper mantle conditions. Moderately depleted harzburgites, which contain chromite with a moderate Cr# (0.4-0.6) and a small amount of clinopyroxene, are the best reactants for the chromitite-forming reaction, and are the best hosts for podiform chromitites. Arc-type chromitites are dominant in ophiolites, but some are of the mid-ocean ridge type; chromitites may be common beneath the ocean floor, although it has not yet been explored for chromitite. The low-pressure (upper mantle) igneous chromitites were conveyed through mantle convection or subduction down to the mantle transition zone to form

  18. Screening of candidate corrosion resistant materials for coal combustion environments -- Volume 4. Final report, January 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Boss, D.E.


    The development of a silicon carbide heat exchanger is a critical step in the development of the Externally-Fired Combined Cycle (EFCC) power system. SiC is the only material that provides the necessary combination of resistance to creep, thermal shock, and oxidation. While the SiC structural materials provide the thermomechanical and thermophysical properties needed for an efficient system, the mechanical properties of the SiC tubes are severely degraded through corrosion by the coal combustion products. To obtain the necessary service life of thousands of hours at temperature, a protective coating is needed that is stable with both the SiC tube and the coal combustion products, resists erosion from the particle laden gas stream, is thermal-shock resistant, adheres to SiC during repeated thermal shocks (start-up, process upsets, shut-down), and allows the EFCC system to be cost competitive. The candidate protective materials identified in a previous effort were screened for their stability to the EFCC combustion environment. Bulk samples of each of the eleven candidate materials were prepared, and exposed to coal slag for 100 hours at 1,370 C under flowing air. After exposure the samples were mounted, polished, and examined via x-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy. In general, the alumina-based materials behaved well, with comparable corrosion depths in all five samples. Magnesium chromite formed a series of reaction products with the slag, which included an alumina-rich region. These reaction products may act as a diffusion barrier to slow further reaction between the magnesium chromite and the slag and prove to be a protective coating. As for the other materials; calcium titanate failed catastrophically, the CS-50 exhibited extension microstructural and compositional changes, and zirconium titanate, barium zironate, and yttrium chromite all showed evidence of dissolution with the slag.

  19. Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

    Energy Technology Data Exchange (ETDEWEB)

    Morton, D.; Lewis, N.; Hanson, M.; Rice, S.; Sanders, P.


    Alloy 600 corrosion coupon tests were performed: (1) to quantify the temperature dependency of general corrosion and (2) to characterize the composition and structure of bulk surface corrosion films for comparison with ongoing primary water SCC (PWSCC) crack tip corrosion film analyses. Results suggest that the thermal activation energy of Alloy 600 corrosion is consistent with the thermal activation energy of nickel alloy PWSCC. Analytical investigations of the structure and composition of Alloy 600 bulk surface corrosion oxides revealed a duplex (inner and outer) oxide layer structure. The outer layer is discontinuous and comprised of relatively large (1 to 3 {micro}m) nickel ferrite crystals and smaller ({approx}0.1 {micro}m) chromium containing nickel ferrite crystals. The inner layer consists of a relatively continuous chromite spinel (major phase) and chromia (Cr{sub 2}O{sub 3} minor phase) which formed through non-selective oxidation. Chromia and dealloyed Alloy 600 (highly Ni enriched metal) were only observed at 337 C (640 F) and only along the boundaries of deformation induced fine grains and subcells. Specimens having deformation free surfaces exhibited continuous uniform inner chromite spinel oxide layers. Specimens with machining induced surface deformation produced non-uniform inner layer oxides (chromite spinel, Cr{sub 2}O{sub 3} and unoxidized material). PWSCC crack tip oxides, in contrast, were fine grain (no duplex structure) and consisted of both chromium rich spinels and ''NiO'' structure oxides. Generally, nickel rich oxides were more abundant under more oxidized conditions (reduced coolant hydrogen) and spinel rich crack tip oxides were favored under more reducing conditions (increased coolant hydrogen). Bulk surface corrosion film thickness did not correlate with observed SCC growth rates. These results suggest that corrosion is not the rate controlling step of PWSCC but rather that PWSCC and corrosion have a common rate

  20. Conodont dating of the Middle Ordovician breccia cap-rock limestone on Osmussaar Island, northwestern Estonia

    Directory of Open Access Journals (Sweden)

    Johanna I. S. Mellgren


    Full Text Available Various mechanisms have hitherto been suggested to explain the formation of the Kundan (Middle Ordovician Osmussaar Breccia in northwestern Estonia. Following the recent discovery of L-chondritic chromite in these peculiar, sand-penetrated strata, it seems plausible that the breccia is impact-related. Herein, the conodont faunas of three thin limestone intervals overlying the breccia at Osmussaar Island have been investigated, with the aim of establishing the age of the event in terms of the Baltoscandian conodont-based biostratigraphical scheme. Based on the presence of Microzarkodina ozarkodella, the limestone directly overlying the breccia is assigned to the M. ozarkodella Subzone of the Lenodus (Eoplacognathus? pseudoplanus Zone. This is reinforced by means of a faunal shift between this sample interval and the subsequent one, which is directly comparable with a faunal shift in the Mäekalda section, mainland Estonia. The middle, orthoceratite-yielding interval is assigned to the uppermost L. (E.? pseudoplanus Zone (or, alternatively, the lowermost Eoplacognathus suecicus Zone, whereas the uppermost interval, an oolitic limestone, is referable to the E. foliaceus Subzone, corresponding to the lower part of the Lasnamägi Stage. These results support a connection between the Osmussaar event and the stratigraphic interval yielding abundant meteorites and/or high levels of L-type chromite in Sweden, as they both can be referred to the lower and/or middle part of the Kunda Stage. The minor difference in age between the first limestones deposited after the brecciation and the meteorite and L-chromite-yielding interval in Baltoscandia can be explained as caused by a period of non-deposition, seen as numerous hiatuses of various extent in the Kunda Stage in northwestern Estonia.

  1. Magnetic properties of pure and Fe doped HoCrO3 thin films fabricated via a solution route (United States)

    Yin, Shiqi; Sauyet, Theodore; Guild, Curt; Suib, S. L.; Jain, Menka


    Multiferroic properties of orthorhombically distorted perovskite rare-earth chromites, such as HoCrO3, are being investigated extensively in recent years. In the present work, we report on the effect of Fe substitution on the magnetic properties of HoCrO3 thin films. Thin films of HoCrO3 and HoCr0.7Fe0.3O3 were fabricated via a solution route on platinized silicon substrates. Structural properties of the films were evaluated by X-ray diffraction and Raman spectroscopy techniques. The surface morphology and cross-sections of the films were examined using scanning electron microscopy. Optical band gaps of pure and Fe doped HoCrO3 films are found to be 3.45 eV and 3.39 eV, respectively. The magnetization measurements show that the Néel temperatures (where Cr3+ orders) for the HoCrO3 and HoCr0.7Fe0.3O3 films are 134 and 148 K, respectively. In a magnetic field of 2 T, the maximum entropy change and relative cooling power, two parameters to evaluate the magnetocaloric properties of a material, were 0.813 J/kg K at 11 K and 21.1 J/kg for HoCrO3 film, in comparison with 0.748 J/kg K at 15 K and 26.8 J/kg for HoCr0.7Fe0.3O3 film. To our knowledge, this is the first work exploring the band gap and magnetocaloric properties of rare-earth chromite thin films. These findings should inspire the development of rare-earth chromite thin films for temperature control of nanoscale electronic devices and sensors in the low temperature region (< 30 K).

  2. Development of regenerable copper-based sorbents for hot gas cleanup: Final technical report, September 1, 1995--August 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Slimane, R.B.; Wangerow, J.R.


    The overall objective of this study was to determine the effectiveness of the copper-chromite sorbent (developed in previous ICCI-funded projects) for longer duration application under optimum conditions in the temperature range of 550{degrees}-650{degrees}C to minimize sorbent reduction and degradation during the cyclic process. Three (3) formulations of attrition resistant granules of the copper chromite sorbent (i.e., CuCr-10, CuCr-21, and CuCr-29) as well as one (1) copper chromite sorbent in pellet form (i.e., CuCr-36) were selected for cyclic desulfurization tests. The desulfurization and regeneration capabilities of the selected formulations as well as the effects of operating parameters were determined, to identify the {open_quotes}best{close_quotes} sorbent formulation and the optimum operating conditions. The durability of the {open_quotes}best{close_quotes} sorbent formulation was determined in {open_quotes}long-term{close_quotes} multicycle tests conducted at the optimum operating conditions. The attrition resistance of the selected formulations were determined and compared with those of other sorbents, including a limestone, a dolomite, and a commercial zinc titanate sorbent. The results obtained in this study indicate that, the CuCr-29 sorbent has excellent attrition resistance and desulfurization performance, which are far superior to the commercial zinc titanate sorbents. The optimum desulfurization temperature in terms of sorbent efficiency and utilization appears to be about 600{degrees}C. Sorbent regeneration at 750{degrees}C ensured complete conversion of the copper sulfide to oxide without sulfate formation or reactivity deterioration in subsequent cycles.

  3. Stability of solid oxide fuel cell materials

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, T.R.; Pederson, L.R.; Stevenson, J.W.; Raney, P.E. [Pacific Northwest Lab., Richland, WA (United States)


    The phase stability and sintering behavior of materials used in SOFCs has been evaluated. The sintering behavior of Ca and Sr doped lanthanum. manganite (the preferred SOFC cathode material) is highly dependent on the relative proportion of A and B site cations in the material. Ca and Sr doped lanthanum chromite (the preferred interconnect material) have been shown to rapidly expand in reducing atmospheres at temperatures as low as 700{degrees}C. This expansion is due to the reduction of Cr{sup 4+} to Cr{sup 3+} in reducing environments.

  4. Magnetocaloric properties of rare-earth substituted DyCrO3 (United States)

    McDannald, A.; Jain, M.


    Recently, there has been a focus on the need for efficient refrigeration technology without the use of expensive or harmful working fluids, especially at temperatures below 30 K. Solid state refrigeration, based on the magnetocaloric effect, provides a possible solution to this problem. The rare-earth chromites (RCrO3), especially DyCrO3, with its large magnetic moment dysprosium ion, are potential candidates for such an application. The Dy3+ ordering transition at low temperatures (cooling power of 237 J/kg at 40 kOe and 5 K) indicates that this material system is well suited for low temperature (<30 K) solid state refrigeration applications.

  5. The Ozernoye meteorite: New data on mineralogy (United States)

    Erokhin, Yu. V.; Koroteev, V. A.; Khiller, V. V.; Burlakov, E. V.; Ivanov, K. S.; Kleimenov, D. A.


    New data on the mineral composition of the Ozernoye meteorite, found in the Kurgan region in 1983, are presented. It has been found that that the meteorite's matter is composed of olivine (chrysolite), orthopyroxene (bronzite), clinopyroxene (augite), maskelynite, chromite, ilmenite, metals Fe and Ni (kamasite, taenite), sulfides (troilite, pentlandite), chlorapatite, and merrillite. Augite, taenite, pentlandite, and merrillite were identified in the Ozernoye meteorite for the first time. The chemical compositions are given for all these minerals. The meteorite itself is an ordinary chondrite stone belonging to petrological type L5.

  6. The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure (United States)

    Barnes, S. J.


    The Cr distributions for a synthetic silicate melt equilibrated with bronzitic orthopyroxene and chromite spinel between 1334 and 1151 C over a range of oxygen fugacities between the nickel-nickel oxide and iron-wuestite buffers are studied. The occurrence, chemical composition, and structure of the orthopyroxene-silicate melt and the spinel-silicate melt are described. It is observed that the Cr content between bronzite and the melt increases with falling temperature along a given oxygen buffer and decreases with falling oxygen fugacity at a given temperature; however, the Cr content of the melt in equilibrium with spinel decreases with falling temperature and increases with lower oxygen fugacity.

  7. Studies on Environmentally Friendly Leaching Processes in China

    Institute of Scientific and Technical Information of China (English)


    The newly developed green leaching processes for chromium, lead and gold extraction from ores or concentrates are described. The chromium is extracted from the iron chromite ore with fused sodium hydroxide at 500-550°C as sodium chromate. The galena in lead sulfide concentrate is converted into lead carbonate in ammonium or sodium carbonate solution at 50-80°C followed by the separation of lead carbonate formed from the unconverted sulfide ores by flotation. Gold associated with sulfide ore (such as pyrite and chalcopyrite) can be extracted into sodium thiosulfate solution without any pretreatment such as roasting, high pressure aqueous oxidation or bacteria pre-leaching.

  8. Magnetic features in REMeO{sub 3} perovskites and their solid solutions (RE=rare-earth, Me=Mn, Cr)

    Energy Technology Data Exchange (ETDEWEB)

    Moure, Carlos, E-mail: [Instituto de Cerámica y Vidrio, CSIC, Electroceramics Department, Kelsen No. 5, 28049 Cantoblanco, Madrid (Spain); Peña, Octavio [Institut des Sciences Chimiques de Rennes, UMR 6226, Université de Rennes 1, 35042 Rennes (France)


    Magnetic hysteresis displacement, thermal inversion of the magnetization, hysteresis loops jumps and crossing branches of hysteresis loops at low magnetic fields are reviewed. Most of these phenomena have been observed in magnetic oxide systems, particularly in perovskite-type manganites and chromites. The paper takes into account structural considerations and different geometrical parameters, such as volume or thin layers. - Highlights: ►Review of both spin reversal phenomena thermal and displacive. ► Study of the crossing branches of the magnetic hysteresis loops. ► Review of the behavior of some stepped hysteresis loops.

  9. Caracterização e classificação quanto ao risco ambiental do estéril da mina de cromita do município de Andorinha, Bahia

    Directory of Open Access Journals (Sweden)

    Aline Maria dos Santos Teixeira


    Full Text Available The mineral waste studied was host rock from a chromite mine located in Andorinha/Bahia, extracted and stockpiled in yards without specific application. Host rock was submitted to chemical analysis, XRD, SEM-EDS, IR and TGA and classified according to ABNT standards for solid waste classification. Analyses confirmed that this host rock, classified as ultrabasic, consists mainly of dolomite, calcite and diopside. Hazard assessment results showed this host rock should be classified as class II B - inert waste, important for its potential application in agriculture as a soil acidity correction agent.

  10. Transport of the reducible species through a La/sub 0. 8/Sr/sub 0. 2/CrO/sub 3/ cathode in the high-temperature electrolysis of steam

    Energy Technology Data Exchange (ETDEWEB)

    Barbi, G.B.; Mari, C.M.


    The kinetics of the reduction of the water molecule at the interface between strontium-doped lanthanum chromite (SDLC) and yttria-stabilized zirconia (YSZ) has been investigated. The cathodic layer consists of a 12 thick SDLC layer covered with a 2 thick porous platinum layer. The results are compared with those obtained previously with a 2 SDLC thick double-layer electrode. The charge transfer contribution to the total overvoltage is dominant as compared to the diffusion polarization component. The diffusion coefficient of oxygen in this perovskite oxide, although not measured, appears to be very high.

  11. 大型不锈钢铸件粘砂及表面烧结机理研究与改进%Mechanisum and Prevention of Surface Burnning-on of Large Sized Stainness Steel Casting

    Institute of Scientific and Technical Information of China (English)

    扈广麒; 王培; 彭凡; 肖纳敏


    对采用呋喃树脂自硬铬矿砂生产高铬不锈钢水轮机叶片铸件表面易出现"釉化"涂料层、界面型砂"釉化"烧结和粘砂缺陷进行了研究,并提出了解决措施.铸件粘砂的主要原因为钢液透过涂料层渗入铬矿砂,在界面发生氧化还原反应,将铬铁矿砂的铁还原出来,还原出的铁和砂粒形成致密混合物,并附着在铸件表面形成"釉化"烧结层.还原出的铁和铬渣以及砂粒中的未反应物,形成了致密的机械混合物,和铸件金属直接相连,附着在铸件的表面,形成粘砂.锆英粉涂料本身也和高铬钢发生微弱的化学反应.用新型添加剂及复合涂料改进型砂和替代锆英粉涂料,提高了钢液和铬矿砂界面涂料层的致密度、化学稳定性和耐火性,可以有效地解决这类问题.%Some defects such as coating glazing, interface sand glazing and sintering and sand fusion always appear on surface of cast high-chromium stainless steel hydraulic turbine blade castings when using furan resin chromite sand. The main reason for these defects is the infiltration of liquid steel through the coating to chromite and the redox reaction took place which reduces iron out of chromite sand. First, the iron and sand are mixed together and become dense mixture, and then iron, sand and the un-reacted material in sand are mixed together to form dense mechanical mixtures attached to the surface of casting causing the sand burning. Second, a weak chemical reaction occurs between zircon powder coating and the high-chromium steel. According to the analyses, the powder coating with higher chemical stability and fire resistance was chosen instead of zircon powder coating. Additionally, the corundum powder coating can improve the coasting density at the interface of the molten steel and chromite sand. And this method is useful for solving such kind of problems.

  12. Residual Separation of Magnetic Fields Using a Cellular Neural Network Approach (United States)

    Albora, A. M.; Özmen, A.; Uçan, O. N.

    - In this paper, a Cellular Neural Network (CNN) has been applied to a magnetic regional/residual anomaly separation problem. CNN is an analog parallel computing paradigm defined in space and characterized by the locality of connections between processing neurons. The behavior of the CNN is defined by the template matrices A, B and the template vector I. We have optimized weight coefficients of these templates using Recurrent Perceptron Learning Algorithm (RPLA). The advantages of CNN as a real-time stochastic method are that it introduces little distortion to the shape of the original image and that it is not effected significantly by factors such as the overlap of power spectra of residual fields. The proposed method is tested using synthetic examples and the average depth of the buried objects has been estimated by power spectrum analysis. Next the CNN approach is applied to magnetic data over the Golalan chromite mine in Elazig which lies East of Turkey. This area is among the largest and richest chromite masses of the world. We compared the performance of CNN to classical derivative approaches.

  13. Unusual Mantle Mineral Group from Chromitite Orebody Cr-11 in Luobusa Ophiolite of Yarlung-Zangbo Suture Zone, Tibet

    Institute of Scientific and Technical Information of China (English)

    Xu Xiangzhen; Yang Jingsui; Chen Songyong; Fang Qingsong; Bai Wenji; Ba Dengzhu


    A wide variety of unusual mantle has been reported from podiform chromitite orebodies Cr-31 and Cr-74 in the Luobusa (罗布莎) ophiolite, Tibet. A detailed investigation of chromitite ore-body Cr-11, located in the Kangjinla (康金拉) district at the eastern end of the ophiolite, has revealed many of the same minerals, including diamond, moissanite, and some native elements, alloys, oxides, sulphides, silicates, carbonates, and tungstates. This orebody is particularly rich in diamonds, with over 1 000 grains recovered from about 1 100 kg sample of chromitite. More detailed studies and experi-ments are needed to understand the origin and significance of these unusual minerals because they have not been found in situ. It is a great breakthrough in mineralogical research that we have picked up more than 40 kinds of minerals from the Kangjinla chromite deposit in Luobusa. It is notable that a large amount of diamonds were firstly discovered from the Kangjinla chromite deposit as well as many other unusual minerals, such as moissanites, rutiles, native irons, and metal alloys. Especially, that diamond was found again in different chromitites In the same ophiolite belt provided new key evidence for discussing the origin of the diamond and the hosted ehromitite and ophiolite. The mantle mineral group in Tibet has great significance in mineralogy and geodynamics.

  14. Nature and genesis of Kalimantan diamonds (United States)

    Smith, Chris B.; Bulanova, Galina P.; Kohn, Simon C.; Milledge, H. Judith; Hall, Anne E.; Griffin, Brendan J.; Pearson, D. Graham


    The origin of alluvial diamonds from the four main diamond mining districts in Kalimantan was studied through characterisation of their properties, and determination of PT and age of formation of representative collections of diamonds from four localities of the island. The diamonds are mostly colourless, yellow or pale brown, shiny surfaced, dodecahedroids, octahedron/dodecahedroids, and more rarely cube combination forms. They are intensively resorbed. They have surface radiation damage and show abrasion features indicative of fluvial transportation and crustal recycling. The diamonds were polished down to expose internal structures and mineral inclusions. The majority of the diamonds are internally homogeneous or have simple octahedral zonation and show plastic deformation. Analysis by Fourier transform infra red spectroscopy of their N content and aggregation characteristics shows that many diamonds are well-aggregated type IaB implying a long-term, mantle residence time and/or high temperatures of formation. Identified inclusion parageneses are 68% peridotitic and 32% eclogitic. The peridotitic inclusions are represented by olivine, chromite, garnet, orthopyroxene and pentlandite. Olivines (Fo 92-93) belong to the dunite-harzburgite paragenesis, with one at Fo 90 identified as lherzolitic. Chromite inclusions with 65-66 wt.% Cr 2O 3 and 4.2 GPa) are consistent with a paleo-heat flow of 38 to 40 mW/m 2 and derivation from 120 to 160 km depth, i.e. subcontinental mantle lithosphere conditions similar to diamonds from African and Yakutian cratonic situations.

  15. Cosmic-ray exposure ages of fossil micrometeorites from mid-Ordovician sediments at Lynna River, Russia

    CERN Document Server

    Meier, Matthias M M; Lindskog, Anders; Maden, Colin; Wieler, Rainer


    We measured the He and Ne concentrations of 50 individual extraterrestrial chromite grains recovered from mid-Ordovician (lower Darriwilian) sediments from the Lynna River section near St. Petersburg, Russia. High concentrations of solar wind-like He and Ne found in most grains indicate that they were delivered to Earth as micrometeoritic dust, while their abundance, stratigraphic position and major element composition indicate an origin related to the L chondrite parent body (LCPB) break-up event, 470 Ma ago. Compared to sediment-dispersed extraterrestrial chromite (SEC) grains extracted from coeval sediments at other localities, the grains from Lynna River are both highly concentrated and well preserved. As in previous work, in most grains from Lynna River, high concentrations of solar wind-derived He and Ne impede a clear quantification of cosmic-ray produced He and Ne. However, we have found several SEC grains poor in solar wind Ne, showing a resolvable contribution of cosmogenic 21Ne. This makes it possi...

  16. Investigation on some ceramic materials for electrochemical device applications. [ZrO[sub 2]-CeO[sub 2]-Y[sub 2]O[sub 3]; Y-Sr-Cr-O; La-Sr-Cr-O

    Energy Technology Data Exchange (ETDEWEB)

    Patil, D.S.; Venkatramani, N.; Rohatgi, V.K. (Laser and Plasma Technology Div., Bhabha Atomic Research Center, Bombay (India)); Mutsuddy, B.C. (Inst. of Materials Processing, Michigan Technological Univ., Houghton (United States))


    The recent developments in the field of high temperature technology demand materials with tailor-made electrical properties. These conductors play an important role in many practical applications. Energy conversion devices like fuel cells require solid electrolyte materials with ionic conductivity and electrodes with electronic conductivity. Mixed conductors are useful for hightemperature electrolysis of water vapor resulting in substantial energy savings in comparision with conventional electrolysis techniques. Because of their stability and reasonably high conductivity the cubic fluorite oxides of zirconia-ceria and chromite-based perovskites have received considerable attention for such applications. Ceramics based on tetragonal zirconia polycrystal (TZP) are being projected as potential fuel cell electrolyte materials. Microwave processing of these materials is a promising approach for the future development of ceramic devices for various electrochemical applications. As a part of the program designed to develop suitable materials for some of these applications, this paper will cover the method of preparation and electrical conductivity study performed on (ZrO[sub 2])[sub 0.85](CeO[sub 2])[sub 0.12](Y[sub 2]O[sub 3])[sub 0.03] and doped chromites A[sub 1-x]Sr[sub x]CrO[sub 3] (A = La, Y). We have also successfully sintered the Y-TZP ceramics to density close to the theoretical by using microwave energy and a single mode applicator. Some of the results will be presented in this paper.

  17. V Xanes in Spinels as an Oxy-Barometer in Meteorites with Implications for Redox Variations in the Inner Solar System (United States)

    Righter, K.; Sutton, S.; Danielson, L.; Pando, K.; Le, L.; Newville, M.


    The variation of oxygen fugacity within inner solar system materials spans a range of nearly 15 orders of magnitude. Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or con-strained such as FeTi oxides, olivine-opx-spinel, or some other oxy-barometer. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO2 using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO2 of many of these achondrites is not well known, other than being "reduced" and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in achondrite. Because the V pre-edge peak intensity and energy in chromites varies with fO2, and this has been calibrated over a large fO2 range, we can apply this relation to rocks for which we otherwise have no fO2 constraints.

  18. Characterization of corrosion scale formed on stainless steel delivery pipe for reclaimed water treatment. (United States)

    Cui, Yong; Liu, Shuming; Smith, Kate; Yu, Kanghua; Hu, Hongying; Jiang, Wei; Li, Yuhong


    To reveal corrosion behavior of stainless steel delivery pipe used in reclaimed water treatment, this research focused on the morphological, mineralogical and chemical characteristics of stainless steel corrosion scale and corroded passive film. Corrosion scale and coupon samples were taken from a type 304 pipe delivering reclaimed water to a clear well in service for more than 12 years. Stainless steel corrosion scales and four representative pipe coupons were investigated using mineralogy and material science research methods. The results showed corrosion scale was predominantly composed of goethite, lepidocrocite, hematite, magnetite, ferrous oxide, siderite, chrome green and chromite, the same as that of corroded pipe coupons. Hence, corrosion scale can be identified as podiform chromite deposit. The loss of chromium in passive film is a critical phenomenon when stainless steel passive film is damaged by localized corrosion. This may provide key insights toward improving a better comprehension of the formation of stainless steel corrosion scale and the process of localized corrosion. The localized corrosion behavior of stainless steel is directly connected with reclaimed water quality parameters such as residual chlorine, DO, Cl(-) and SO4(2-). In particular, when a certain amount of residual chlorine in reclaimed water is present as an oxidant, ferric iron is the main chemical state of iron minerals.

  19. Olivine and Ca-Phosphate in the Diogenites Manegaon and Roda (United States)

    Domanik, K. J.; Sideras, L. C.; Drake, M. J.


    The textural relationships between the different primary minerals in igneous rocks provide one of the most fundamental pieces of evidence available for inferring the crystallization history of their parent magmas. Unfortunately, the high degree of brecciation that characterizes most diogenites, along with the low modal abundance and small grain sizes of minerals other than orthopyroxene, combine to make identifying and interpreting such textural relationships extremely difficult in this class of meteorites. A few descriptions of primary igneous contacts between orthopyroxene and chromite, troilite, and to a lesser extent, olivine in diogenites have been provided in the literature. In addition to these, in previous work, our research group has characterized several types of igneous contacts between Ca-pyroxene, plagioclase and orthopyroxene in the Bilanga diogenite. We have also described primary igneous inclusions of troilite + kamacite + chromite + Ca-pyroxene +/- Ca-phosphate in orthopyroxene (i.e. Metal/Troilite- Ball inclusions) in the diogenites Bilanga, Manegaon, Johnstown, Roda, Shalka, and Tatahouine. However, for the most part, detailed data on igneous textural relations between minerals other than orthopyroxene in diogenites are still sparse. Of the diogenite samples that we have examined,

  20. Non-destructive analyses on a meteorite fragment that fell in the Madrid city centre in 1896. (United States)

    Garcia-Guinea, Javier; Tormo, Laura; Rubio Ordoñez, Alvaro; Garcia-Moreno, Olga


    The historical Madrid meteorite chondrite fell in 1896 showing thin melt veins with a 65% of brecciated forsterite fragments surrounded by a fine grained matrix formed by troilite, chromite and Fe-Ni blebs. It exhibits a delicate iron infill, neo-formation of troilite in pockets and shock veins and neo-formation of Na-feldspar formed at high temperature and fast quenching. The semi-quantitative mineral determinations were performed with IMAGEJ freeware and chemical mappings resulting in the following approximated compositions: olivine (~55%); augite (~10%); enstatite (~10%); plagioclase (~10%); chromite (~2%); troilite (~4%), kamacite-taenite α-γ-(Fe, Ni) (~7%) and merrillite (~7%). The specimen was also studied by computer tomography, micro-Raman spectroscopy and spectral cathodoluminescence. X-ray diffraction patterns were also recorded in non-destructive way on a polished surface because of the small size of the specimen. This combination of non-destructive techniques provides an improved knowledge on the Madrid-1896 meteorite compared to the previous study performed on the same specimen carried out twenty years ago by electron probe microanalysis and optical microscopy in destructive way. Limits of these techniques are the specimen's size in the analytical chambers and the threshold resolution of the microscopes analyzing shock veins micro-crystals.

  1. Structural characterization and electron density distribution studies of (La{sub 0.8}Ca{sub 0.2})(Cr{sub 0.9−x}Co{sub 0.1}Mn{sub x})O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, R. [Research Centre and Post Graduate Department of physics, The Madura College, Madurai 625011 (India); Thenmozhi, N., E-mail: [PG and Research Department of Physics, NMSSVN College, Nagamalai, Madurai 625019 (India); Fu, Yen-Pei [Department of materials Science and Engineering, National Dong-Hwa University, Shou-Feng, Hualien 974, Taiwan (China)


    The doped lanthanum chromite (La{sub 0.8}Ca{sub 0.2})(Cr{sub 0.9−x}Co{sub 0.1}Mn{sub x})O{sub 3} (x=0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV–visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46 eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).

  2. Weathering and transport of chromium and nickel from serpentinite in the Coast Range ophiolite to the Sacramento Valley, California, USA (United States)

    Morrison, Jean M.; Goldhaber, Martin B.; Mills, Christopher T.; Breit, George N.; Hooper, Robert L.; Holloway, JoAnn M.; Diehl, Sharon F.; Ranville, James F.


    A soil geochemical study in northern California was done to investigate the role that weathering and transport play in the regional distribution and mobility of geogenic Cr and Ni, which are both potentially toxic and carcinogenic. These elements are enriched in ultramafic rocks (primarily serpentinite) and the soils derived from them (1700–10,000 mg Cr per kg soil and 1300–3900 mg Ni per kg soil) in the Coast Range ophiolite. Chromium and Ni have been transported eastward from the Coast Range into the western Sacramento Valley and as a result, valley soil is enriched in Cr (80–1420 mg kg−1) and Ni (65–224 mg kg−1) compared to median values of U.S. soils of 50 and 15 mg kg−1, respectively. Nickel in ultramafic source rocks and soils is present in serpentine minerals (lizardite, antigorite, and chrysotile) and is more easily weathered compared to Cr, which primarily resides in highly refractory chromite ([Mg,Fe2+][Cr3+,Al,Fe3+]2O4). Although the majority of Cr and Ni in soils are in refractory chromite and serpentine minerals, the etching and dissolution of these minerals, presence of Cr- and Ni-enriched clay minerals and development of nanocrystalline Fe (hydr)oxides is evidence that a significant fractions of these elements have been transferred to potentially more labile phases.

  3. A regenerable copper-based sorbent for H{sub 2}S removal from coal gases

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Slimane, R.B. [Institute of Gas Technology, Des Plaines, IL (United States)


    This paper reports on research conducted for the development of copper-based sorbents for hot coal gas desulfurization applications in the temperature range of 550-650{degree}C. A thermodynamic analysis is given to rationalize the selection of chromia (Cr{sub 2}O{sub 3}), and its potential superiority to alumina (Al{sub 2}O{sub 3}), for the stabilization of copper oxide (Cu{sub 2}O) against complete reduction to elemental copper (Cu) upon exposure to a fuel gas in the indicated temperature range. The results of packed-bed experiments carried out for the determination of optimum operating conditions as well as the evaluation of the long-term durability and regenerability of a selected copper chromite sorbent was presented and discussed. The regenerable copper chromite sorbent developed, designated as CuCr-29, is capable of achieving less than 5 ppmv H{sub 2}S concentration in the cleaned fuel gas. The optimum desulfurization temperature in terms of sorbent efficiency (terminal H{sub 2}S levels in the cleaned fuel gas) and utilization (sulfur capacity at breakthrough or effective capacity) for this sorbent is determined to be about 600{degree}C. Sorbent regeneration with a dilute O{sub 2}-N{sub 2} gas mixture at 750{degree}C ensured complete conversion of the copper sulfide to oxide without sulfate formation or reactivity deterioration in subsequent cycles.

  4. Structural characterization and electron density distribution studies of (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3 (United States)

    Saravanan, R.; Thenmozhi, N.; Fu, Yen-Pei


    The doped lanthanum chromite (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3 (x=0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV-visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46 eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).

  5. Magneto-thermal conduction and magneto-caloric effect in poly and nano crystalline forms of multiferroic GdCrO3 (United States)

    Uma, S.; Philip, J.


    Gadolinium chromite, GdCrO3, belongs to the family of rare earth chromites, exhibiting multiferroism with coupling between electric polarization and magnetic ordering. It is understood that the interaction between Gd3+ and Cr3+ ions is responsible for switchable polarization in this system. Below Néel temperature the spins of Cr3+ ions interact in anti-parallel through super exchange mechanism, giving rise to antiferromagnetic ordering at around 169 K in poly and nanocrystalline phases of this material. In order to understand the nature of spin-lattice coupling and magnon-phonon interaction in the intermediate temperature range (150-250 K), the magneto-thermal conduction and magneto-caloric effect in poly and nanocrystalline forms of this material are reported. These properties show anomalies around 169 K, which is described as due to spin-phonon coupling. When particle sizes are reduced to nanometer scales, thermal conductivity decreases significantly while specific heat capacity increases. The former is explained as due to reduction in phonon mean free path and phonon scattering from nanoparticle interfaces, while the latter is ascribed to contributions from Einstein oscillators at weakly bound atoms at the interfaces of nanocrystals.

  6. Novel Approaches to the Production of Higher Alcohols From Synthesis Gas. Quarterly report, January 1 - March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, George W


    Effort during this quarter was devoted to three areas: 1) analyzing the data from earlier runs with "zinc chromite"catalyst and three different slurry liquids: decahydronaphthalene (Decalin®, DHN), tetrahydronaphthalene (tetralin, THN) and tetrahydroquinoline (THQ); 2) analyzing newly-obtained data from earlier thermal stability tests on DHN and THN, and 3) carrying out a thermal stability test on THQ. Both the activity and selectivity of "zinc chromite" catalyst depended on the slurry liquid that was used. The catalyst activity for methanol synthesis was in the order: THQ > DHN > THN. Despite the basic nature of THQ, it exhibited the highest dimethyl ether (DME) production rates of the three liquids. Gas chromatography/mass spectroscopy (GC/MS) analyses of samples of THN and DHN were taken at the end of standard thermal stability tests at 375°C. With both liquids, the only measurable compositional change was a minor amount of isomerization. Analysis of a sample of THN after a thermal stability test at 425°C showed a small reduction in molecular weight, and a significant amount of opening of the naphthenic ring. Preliminary data from the tehrmal stability test of THQ showed that this molecule is more stable than DHN, but less stable than THN.

  7. Using vanadium in spinel as a sensor of oxygen fugacity in meteorites: Applications to Mars, Vesta, and other asteroids.

    Energy Technology Data Exchange (ETDEWEB)

    Righter, K.; Sutton, S.; Danielson, L.; Pando, K.; Le, L.; Newville, M. (Jacobs Engineering); (NASA JSC); (Hamilton Sundstrand); (UC)


    Some meteorites do not contain mineral assemblages required to apply traditional oxy-barometers. Here we introduce a technique using vanadium X-ray absorption features in spinels to characterize the oxygen fugacity of meteoritic dunites, pyroxenites, and chondrites. Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO{sub 2} using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO{sub 2} of many of these samples is not well known, other than being 'reduced' and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO{sub 2}, and this has been calibrated over a large fO{sub 2} range, we can apply this relation to rocks for which we otherwise have no fO{sub 2} constraints.

  8. Optimization of {sup 18}O measurement using NRA for studies of isotopic content in fossil meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Borysiuk, M., E-mail: [Division of Nuclear Physics, Department of Physics, Lund University, Box 118, SE-221 00 Lund (Sweden); Kristiansson, P.; Arteaga-Marrero, N.; Elfman, M.; Golubev, P.; Nilsson, E.J.C.; Nilsson, C.; Pallon, J.; Salim, N. [Division of Nuclear Physics, Department of Physics, Lund University, Box 118, SE-221 00 Lund (Sweden)


    In this work, we discuss the possibility of a new approach to measuring oxygen isotope ratios in fossil meteorite samples, specifically one based on nuclear reaction analysis (NRA). Variations of oxygen ratios within meteoritic chromite grains can help to determine the type of meteorite to which the grains originally belonged. In this work, we have evaluated the possibility to use the reaction {sup 18}O(p, {alpha}){sup 15}N just above the 846 keV resonance to estimate the relative oxygen-18 content in a number of test samples. Another technique has to be employed for oxygen-16 measurements. A large area segmented silicon detector is used to detect the produced {alpha} particles. Results of the experimental {sup 18}O measurements for a number of samples including four extraterrestrial chromite grains are presented and compared with SIMNRA simulations. The advantage of a segmented silicon detector in the form of inherent pile-up suppression can be clearly seen in the current work.

  9. Thermodynamic Modelling of Fe-Cr-Ni-Spinel Formation at the Light-Water Reactor Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kurepin, V.A.; Kulik, D.A.; Hitpold, A.; Nicolet, M


    In the light water reactors (LWR), the neutron activation and transport of corrosion products is of concern in the context of minimizing the radiation doses received by the personnel during maintenance works. A practically useful model for transport and deposition of the stainless steel corrosion products in LWR can only be based on an improved understanding of chemical processes, in particular, on the attainment of equilibrium in this hydrothermal system, which can be described by means of a thermodynamic solid-solution -aqueous-solution (SSAS) model. In this contribution, a new thermodynamic model for a Fe-Cr-Ni multi-component spinel solid solutions was developed that considers thermodynamic consequences of cation interactions in both spinel sub-Iattices. The obtained standard thermodynamic properties of two ferrite and two chromite end-members and their mixing parameters at 90 bar pressure and 290 *c temperature predict a large miscibility gap between (Fe,Ni) chromite and (Fe,Ni) ferrite phases. Together with the SUPCRT92-98 thermo- dynamic database for aqueous species, the 'spinel' thermodynamic dataset was applied to modeling oxidation of austenitic stainless steel in hydrothermal water at 290*C and 90 bar using the Gibbs energy minimization (GEM) algorithm, implemented in the GEMS-PSI code. Firstly, the equilibrium compositions of steel oxidation products were modelIed as function of oxygen fugacity .fO{sub 2} by incremental additions of O{sub 2} in H{sub 2}O-free system Cr-Fe- Ni-O. Secondly, oxidation of corrosion products in the Fe-Cr-Ni-O-H aquatic system was modelIed at different initial solid/water ratios. It is demonstrated that in the transition region from hydrogen regime to oxygen regime, the most significant changes in composition of two spinel-oxide phases (chromite and ferrite) and hematite must take place. Under more reduced conditions, the Fe-rich ferrite (magnetite) and Ni-poor chromite phases co-exist at equilibrium with a metal Ni

  10. Unlocking the zinc isotope systematics of iron meteorites (United States)

    Bridgestock, L. J.; Williams, H.; Rehkämper, M.; Larner, F.; Giscard, M. D.; Hammond, S.; Coles, B.; Andreasen, R.; Wood, B. J.; Theis, K. J.; Smith, C. L.; Benedix, G. K.; Schönbächler, M.


    Zinc isotope compositions (δ66Zn) and concentrations were determined for metal samples of 15 iron meteorites across groups IAB, IIAB, and IIIAB. Also analyzed were troilite and other inclusions from the IAB iron Toluca. Furthermore, the first Zn isotope data are presented for metal-silicate partitioning experiments that were conducted at 1.5 GPa and 1650 K. Three partitioning experiments with run durations of between 10 and 60 min provide consistent Zn metal-silicate partition coefficients of ∼0.7 and indicate that Zn isotope fractionation between molten metal and silicate is either small (at less than about ±0.2‰) or absent. Metals from the different iron meteorite groups display distinct ranges in Zn contents, with concentrations of 0.08-0.24 μg/g for IIABs, 0.8-2.5 μg/g for IIIABs, and 12-40 μg/g for IABs. In contrast, all three groups show a similar range of δ66Zn values (reported relative to ‘JMC Lyon Zn’) from +0.5‰ to +3.0‰, with no clear systematic differences between groups. However, distinct linear trends are defined by samples from each group in plots of δ66Zn vs. 1/Zn, and these correlations are supported by literature data. Based on the high Zn concentration and δ66Zn ≈ 0 determined for a chromite-rich inclusion of Toluca, modeling is employed to demonstrate that the Zn trends are best explained by segregation of chromite from the metal phase. This process can account for the observed Zn-δ66Zn-Cr systematics of iron meteorite metals, if Zn is highly compatible in chromite and Zn partitioning is accompanied by isotope fractionation with Δ66Znchr-met≈-1.5‰. Based on these findings, it is likely that the parent bodies of the IAB complex, IIAB and IIIAB iron meteorites featured δ66Zn values of about -1.0 to +0.5‰, similar to the Zn isotope composition inferred for the bulk silicate Earth and results obtained for chondritic meteorites. Together, this implies that most solar system bodies formed with similar bulk Zn isotope

  11. Generalized corrosion of nickel base alloys in high temperature aqueous media: a contribution to the comprehension of the mechanisms; Corrosion generalisee des alliages a base nickel en milieu aqueux a haute temperature: apport a la comprehension des mecanismes

    Energy Technology Data Exchange (ETDEWEB)

    Marchetti-Sillans, L


    In France, nickel base alloys, such as alloy 600 and alloy 690, are the materials constituting steam generators (SG) tubes of pressurized water reactors (PWR). The generalized corrosion resulting from the interaction between these alloys and the PWR primary media leads, on the one hand, to the formation of a thin protective oxide scale ({approx} 10 nm), and on the other hand, to the release of cations in the primary circuit, which entails an increase of the global radioactivity of this circuit. The goal of this work is to supply some new comprehension elements about nickel base alloys corrosion phenomena in PWR primary media, taking up with underlining the effects of metallurgical and physico-chemical parameters on the nature and the growth mechanisms of the protective oxide scale. In this context, the passive film formed during the exposition of alloys 600, 690 and Ni-30Cr, in conditions simulating the PWR primary media, has been analyzed by a set of characterization techniques (SEM, TEM, PEC and MPEC, XPS). The coupling of these methods leads to a fine description, in terms of nature and structure, of the multilayered oxide forming during the exposition of nickel base alloys in primary media. Thus, the protective part of the oxide scale is composed of a continuous layer of iron and nickel mixed chromite, and Cr{sub 2}O{sub 3} nodules dispersed at the alloy / mixed chromite interface. The study of protective scale growth mechanisms by tracers and markers experiments reveals that the formation of the mixed chromite is the consequence of an anionic mechanism, resulting from short circuits like grain boundaries diffusion. Besides, the impact of alloy surface defects has also been studied, underlining a double effect of this parameter, which influences the short circuits diffusion density in oxide and the formation rate of Cr{sub 2}O{sub 3} nodules. The sum of these results leads to suggest a description of the nickel base alloys corrosion mechanisms in PWR primary

  12. ELNES investigations of the oxygen K-edge in spinels. (United States)

    Docherty, F T; Craven, A J; McComb, D W; Skakle, J


    The results of a systematic study of the oxygen K-edge electron energy-loss spectroscopy (ELNES) from a series of aluminium- and chromium-containing spinels are presented. Extra fine structure in the region up to 10 eV above the edge onset is observed for the chromium-containing compounds and is assigned to transitions to states created by mixing of oxygen 2p and metal 3d orbitals. The experimental data has been simulated using the multiple scattering code, FEFF8. Good agreement was obtained in the case of magnesium aluminate, but relatively poor agreement was obtained in the case of the chromites. The possible fingerprints in the oxygen K-edge ELNES corresponding to a high degree of inversion the spinel structure and to a tetragonal distortion of the cubic structure are discussed.

  13. Effect of Burning Rate Modifiers on Subatmospheric Flame Temperatures of AP/HTPB Composite Solid Propellants

    Directory of Open Access Journals (Sweden)

    S. Krishnan


    Full Text Available Using 30 um. pt and Pt 13 percent Rh thermocouples, flame temperatures of uncatalysed andcatalysed ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/lffPB composite solidpropellants were measured under subatmospheric conditions. Ferric oxide F e 2 and copper chromite(CC were the catalysts used. The study demonstrates that Fe2O3 catalysed propellant, notwithstandingits least combustion efficiency undt;r subatmospheric conditions and weak gas-phase flame, has themaximum burning rate enhancement. This is argued to be due to the increased surface and subsurfacereactions caused by Fe2O3. CC-catalysed propellant burns to the least subatmospheric pressure withminimum loss in combustion efficiency indicating that this class of propellant may be more suitablefor base-bleed applications.

  14. Magnetic properties of sonochemically synthesized CoCr2O4 nanoparticles (United States)

    Dutta, Dimple P.; Manjanna, J.; Tyagi, A. K.


    Cobalt chromite (CoCr2O4) is a potential multiferroic material. In order to understand the temperature dependent magnetic transitions on particle morphology, here we prepared CoCr2O4 nanoparticles by sonochemical technique. We used powder x-ray diffraction, transmission electron microscopy, selected area electron diffraction, superconducting quantum interference device magnetometer, and ac susceptibility measurement techniques for characterization. The low-temperature magnetic behavior of CoCr2O4 nanoparticles have been investigated in more detail. While the bulk CoCr2O4 exhibits two magnetic transitions viz., Tc≈98 K and Ts≈26 K, the nanoparticles here showed a Tc≈84 K and Ts≈25 K. We tentatively attribute this shift in Tc to finite size effects.

  15. Advanced Sensor Arrays and Packaging

    Energy Technology Data Exchange (ETDEWEB)

    Ryter, John Wesley [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Romero, Christopher J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramaiyan, Kannan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brosha, Eric L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    Novel sensor packaging elements were designed, fabricated, and tested in order to facilitate the transition of electrochemical mixed-potential sensors toward commercialization. Of the two designs completed, the first is currently undergoing field trials, taking direct measurements within vehicle exhaust streams, while the second is undergoing preliminary laboratory testing. The sensors’ optimal operating conditions, sensitivity to hydrogen, and long-­term baseline stability were also investigated. The sensing capabilities of lanthanum chromite (La0.8Sr0.2CrO3) and indium-­doped tin oxide (ITO) working electrodes were compared, and the ITO devices were selected for pre-­commercial field trials testing at a hydrogen fuel cell vehicle fueling station in California. Previous data from that fueling station were also analyzed, and the causes of anomalous baseline drift were identified.

  16. Development of High Quality Magnesite—Chrome Bricks for Secondary Steelmaking Furnaces

    Institute of Scientific and Technical Information of China (English)

    LIYong; LIUShensheng; 等


    This paper describes developments of high quality magnesite-chrome bricks used for secondary steelmaking furnaces,mainly including direct-bond-ed magnesite-chrome brick,fully synthesized(co-clinker) magnesite-chrome brick,semi-rebonded magnesite-chrome brick and fused grain rebonded magnesite-chroe brick,Investigations have also been conducted on the effects of various chromites on the properties of the direct bonded magnesite-chrome brick,effects of different sesquioxides (CrO3,Al3O3,Fe2O3) on the properties of the fully synthe-sized(co-clinker) magnesite-hrome brick and ef-fects of ZrO2,Cr-Fe alloy,ultra-fine powders on the properties of the fused grain rebonded brick and the semi-rebonded magnesite-chrome brick ,Applica-tions of the bricks in various secondary steelmaking furnaces have been briefly introduced as well.

  17. Study of Chelyabinsk LL5 meteorite fragment with a light lithology and its fusion crust using Mössbauer spectroscopy with a high velocity resolution

    Energy Technology Data Exchange (ETDEWEB)

    Maksimova, Alevtina A.; Petrova, Evgeniya V.; Grokhovsky, Victor I. [Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002 (Russian Federation); Oshtrakh, Michael I., E-mail:; Semionkin, Vladimir A. [Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation and Department of Experimental Physics, Institute of Physics and Technology, Ura (Russian Federation)


    Study of Chelyabinsk LL5 ordinary chondrite fragment with a light lithology and its fusion crust, fallen on February 15, 2013, in Russian Federation, was carried out using Mössbauer spectroscopy with a high velocity resolution. The Mössbauer spectra of the internal matter and fusion crust were fitted and all components were related to iron-bearing phases such as olivine, pyroxene, troilite, Fe-Ni-Co alloy, and chromite in the internal matter and olivine, pyroxene, troilite, Fe-Ni-Co alloy, and magnesioferrite in the fusion crust. A comparison of the content of different phases in the internal matter and in the fusion crust of this fragment showed that ferric compounds resulted from olivine, pyroxene, and troilite combustion in the atmosphere.

  18. Enhancing the hexavalent chromium bioremediation potential of Acinetobacter junii VITSUKMW2 using statistical design experiments. (United States)

    Pulimi, Mrudula; Jamwal, Subika; Samuel, Jastin; Chandrasekaran, Natarajan; Mukherjee, Amitava


    The Cr(VI) removal capability of Acinetobacter junii VITSUKMW2 isolated from the Sukinda chromite mine site was evaluated and enhanced using statistical design techniques. The removal capacity was evaluated at different pH values (5-11) and temperatures (30-40 degrees C) and with various carbon and nitrogen sources. Plackett- Burman design was used to select the operational parameters for bioremediation of Cr(VI). Three parameters (molasses, yeast extract, and Cr(VI) concentration) were chosen for further optimization using central composite design. The optimal combination of parameters was found to be 14.85 g/l molasses, 4.72 g/l yeast extract, and 54 mg/l initial Cr(VI), with 99.95% removal of Cr(VI) in 12 h. A. junii VITSUKMW2 was shown to have significant potential for removal of Cr(VI).

  19. Evaluation of electromagnetic absorbing capacity of materials in foundry industry

    Directory of Open Access Journals (Sweden)

    D. Nowak


    Full Text Available In the paper, a research on determining the standing wave ratio as a measure of electromagnetic absorbing capacity of moulding materials is presented. Preliminary tests performed using a microwave strip line showed that high-silica, chromite and magnesite moulding sands are characterised by low absorbing capacity of microwaves. It was demonstrated that microwave absorbing capacity is significantly affected by chemical compounds included in the examined substrates. It was found that use of a microwave strip line permits precise determining characteristic microwave absorbing capacities of various moulding materials and thus their suitability for microwave drying/hardening of moulds and cores or for other foundry processes. Such a microwave drier can be applied for identifying mass components and for determining e.g. base granularity by means of precisely determined reflection ratios |Γ| and positions of minimum signal values.

  20. Effect of Bi2O3 Additives on Properties of La0.7Ca0.3CrO3

    Institute of Scientific and Technical Information of China (English)

    Zhong Honghai; Zhou Xiaoliang; Liu Xingqin; Meng Guangyao


    Sintering characteristics of Ca-doped lanthanum chromite [La(Ca)CrO3] powder, prepared by gel-casting process were studied by measuring density and the evaluation of micro structural information. Bi2O3 is found to be an effective sintering additive for this material. The amount of Bi2O3 is altered to investigate Bi2O3 effect on the properties of La0.7Ca0.3CrO3. The amount of 10% (mass fraction) Bi2O3 is suitable to increase sinter-ability of La0.7Ca0.3CrO3. Increased concentration of point defects arising form substitution of Bi in La site is the plausible cause of enhanced sintering. Measurement of electrical conductivity and thermal expansion coefficient indicate that the doping of Bi2O3 does not have any significant effect on these properties.

  1. Petrography and Metamorphism of the Metasedimentary Country-Rocks of the Jacurici Valley Chromitite-Hosting Mafic-Ultramafic Complexes, Bahia, Northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Eliane A. Del Lama


    Full Text Available This paper deal with on the metasedimentary country-rocks of the chromite-bearing ultramafic rocks that occur in the “Jacurici River Valley Chromium District” northeastern Bahia, Brazil. This region presents a complex geologic-petrologic framework of rocks that were intensely deformed, metamorphosed and transformed by metasomatic processes, making it difficult to interpret their volutionary/metamorphic record. Although the metasedimentary country rocks have also been affected by such processes, it is possible to distinguish evidence of a previous high-grade metamorphism that affected them. Thermobarometric data for the observed mineralogical associations indicate P-T conditions around 750-800ºC and 7-8 kb for the metamorphic peak, based mainly on the presence of olivine in marbles and the cordierite-garnet-sillimanitespinel association in aluminous gneisses.

  2. Geochemical prospecting for copper and nickel in the Wulgai and Tor Tangi areas southeast of Hindubagh, Quetta Division, Pakistan (United States)

    Stanin, S. Anthony; Wahid, M.A.; Khan, Shamsher


    Showings of magnetite, copper, and possible nickel mineralization in the Hindubagh chromite mining district are near Wulgai and Tor Tangi. Several hundred samples of clastic material from dry streambeds in these areas were sieved for the minus-80-mesh fraction and analyzed for copper using 2, 2'-biquinoline and for nickel using alpha-furildioxime. The copper threshold is 75 ppm, and the nickel threshold is 400 ppm. A geochemical map has been prepared that shows nine areas of anomalously high copper and six areas of high nickel. The nickel anomalies may represent secondary dispersion patterns derived from the erosion of nickeliferous ultramafic rocks of the Hindubagh intrusive complex. Copper showings in and near four of the anomalous copper areas indicate that detailed geological investigation and detailed geochemical sampling of rocks, soil, and unconsolidated clastic material are required to determine the source of the anomalies.

  3. Crystallization Age and Source Signature of Chassigny (United States)

    Misawa, K.; Shih, C.-Y.; Reese, Y.; Nyquist, L. E.


    Chassigny is the Martian dunite composed of cumulate olivine (92%), chromite (1.4%), pyroxene (5%) and interstitial feldspar (1.7%). Although nakhlites (clinopyroxenite) are less intensely affected by shock metamorphism, Chassigny has been subjected to a peak shock pressure of about 35 GPa. The cosmic-ray exposure age of Chassigny (11.3 +/- 0.6 Ma) is comparable to those of nakhlites, suggesting launch pairing of these meteorites. Prior chemical and isotopic studies of Chassigny suggest that the meteorite crystallized approx. 1.3 Ga ago and is closely related to nakhlites. Nevertheless, compared to other Martian meteorites there are limited isotopic data for Chassigny. To examine the relationship of Chassigny to nakhlites, we have undertaken new Rb-Sr and Sm-Nd isotopic studies. Here we present the new Sm-Nd isotopic data for Chassigny and discuss the nature of its source materials.

  4. A Plastic Flow and Rheomorfic Differentiation of the Mantle Ultramafic Rocks

    Directory of Open Access Journals (Sweden)

    D. E. Saveliev


    Full Text Available In this paper, the general characteristics of morphological features of the ophiolitic ultramafic rock formations are discussed. The ultramafic rocks are the fragments of upper mantle, which were exposed on the surface due to tectonic events. It is shown that their main chemical and structural characteristic is a stratification accompanied by separation of the rheologically weakest dunite bodies usually containing the economic amount of chromite ore. Based on results of conducted analysis, we propose a new hypothesis of petro- and ore genesis in the upper mantle. Using the thermodynamic approach, we developed the rheomorfic model of the differentiation of the mantle matter. This model solves many problems inherent to currently used magmatic or metasomatic models.

  5. 洮南球粒陨石的物质组成和组构研究

    Institute of Scientific and Technical Information of China (English)



    On February 28, 1965, the Taonan chondrite fell near the northwest of Taonan County,Jilin Province (122°E, 45°47'N). The total recovered mass was about 3.75 kg in weight(2,550, 1,100 and 100 g). Tts chemical composition shows that the Taonan chondrite belongs to L-group chondrites. Petrochemically, it should be designated to type 5. The major minerals present in the chondrite include:olivine (Fo=23±% ), orthopyroxene (Fs=20±%), plagioclase, zircon, quartz, kamacite, taenite, troilite, chromite native copper and cassiterite. Shock effect is obvious in olivine and orthopyroxene. Two stages of evolution have been involved in the crystallization of troilite.

  6. The Behaviour of Chromium Isotopes during the Oxidative Weathering of Ultramafic Rocks

    DEFF Research Database (Denmark)

    Paulukat, Cora Stefanie; Døssing, Lasse Nørbye; Mondal, Sisir K.;

    Ore Group in the southern Singhbhum Craton (Orissa, India)[3]. A modern weathering profile was logged in an active open cast chromite mine (Sukinda valley). The Cr isotope data of samples from the weathering profile are fractionaed. While the least weathered horizons at the base of the profile reflect......The chromium isotope system has been proven to be a redox-sensitve proxy in ancient and modern environmental studies (e.g. [1], [2]). In this study we investigated Cr isotope fractionation during soil formation from Archean (3.1-3.3 Ga) ultramafic rocks, intruded into metamorphic rocks of the Iron...... are characterised by a Cr loss of up to 74 %. These data are consistent with the findings of Crowe et al. [2] who also studied the effects of weathering of ultramafic rocks in Indonesia on the Cr isotope system. These authors demonstrate that oxidation of Cr(III) to Cr(VI) in the soils is accompanied by isotopic...

  7. Influence of the sintering temperature on the structural and electronic properties of LaCrO{sub 3} doped with barium; Influencia da temperatura de sinterizacao nas propriedades estruturais e eletronicas de LaCrO{sub 3} dopadas com bario

    Energy Technology Data Exchange (ETDEWEB)

    Silva, A.L.A. da; Souza, M.V.M.M., E-mail: [Universidade Federal do Rio de Janeiro (LabTecH/EQ/UFRJ), RJ (Brazil). Escola de Quimica. Lab. de Tecnologias do Hidrogenio; Rocco, A.M. [Universidade Federal do Rio de Janeiro (GMCE/EQ/UFRJ), RJ (Brazil). Escola de Quimica. Grupo de Materiais Condutores e Energia


    Ba-doped lanthanum chromites were synthesized by combustion method, utilizing urea and glycine as fuel agents. The powders were calcined (800 deg C/6 h), pelletized, sintered in various temperatures and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density/porosity and electrical conductivity. The diffractograms of the sintered samples presented a well-defined structure, with presence of secondary phases which increase with the sintering temperature. The samples presented low densities and a high porosities (40 - 50%), which was also observed in SEM analysis. The urea-synthesized sample presented a higher conductivity (10.4 S/cm at 1000 deg C), which is related to the influence of the fuel agent in the material properties. (author)

  8. Platinum-group minerals in the LG and MG chromitites of the eastern Bushveld Complex, South Africa (United States)

    Oberthür, Thomas; Junge, Malte; Rudashevsky, Nikolay; de Meyer, Eveline; Gutter, Paul


    The chromitites of the Bushveld Complex in South Africa contain vast resources of platinum-group elements (PGE); however, except for the economic upper group (UG)-2 chromitite seam, information on the distribution of the PGE in the ores and on the mineralogical nature, assemblages, and proportions of platinum-group minerals (PGM) is essentially missing. In the present geochemical and mineralogical study, PGE concentrates originating from the lower group (LG)-6 and middle group (MG)-1/2 chromitites were investigated with the intention to fill this gap of knowledge. Chondrite-normalized PGE patterns of bulk rock and concentrates are characterized by a positive slope from Os to Rh, a slight drop to Pt, and an increase to Pd again. The pronounced similarities of the PGE patterns indicate similar primary processes of PGE concentration in the chromitites, namely "sulfide control" of the PGE mineralization, i.e., co-precipitation of chromite and sulfide. Further, the primary control of PGE concentration in chromitites appears to be dual in character: (i) base-level concentrations of IPGE (up to ˜500 ppb) hosted within chromite and (ii) co-precipitation of chromite and sulfide, the latter containing virtually the entire remaining PGE budget. Sulfides (chalcopyrite, pentlandite, and pyrite; pyrrhotite is largely missing) are scarce within the chromitites and occur mainly interstitial to chromite grains. Pd and Rh contents in pentlandite are low and erratic. Essentially, the whole PGE inventory of the ores occurs in the form of discrete PGM. The PGM are almost always associated with sulfides. The dominant PGM are various Pt-Pd-Rh sulfides (cooperite/braggite [(Pt,Pd)S] and malanite/cuprorhodsite [CuPt2S4]/[CuRh2S4]), laurite [RuS2], the main carrier of the IPGE (Os, Ir, Ru), sulfarsenides [(Rh,Pt,Ir)AsS], sperrylite [PtAs2], Pt-Fe alloys, and a large variety of mainly Pd-rich PGM. The LG and MG chromitites have many characteristics in common and define a general, "typical

  9. Highly Siderophile Elements in Pallasites and Diogenites, Including the New Pallasite, CMS 04071 (United States)

    Danielson, L. R.; Humayun, M.; Righter, K.


    Pallasites are long thought to represent a metallic core-silicate mantle boundary, where the IIIAB irons are linked to the crystallization history of the metallic fraction, and the HED meteorites may be linked to the silicate fraction. However, measurement of trace elements in individual metallic and silicate phases is necessary in order to fully under-stand the petrogenetic history of pallasites, as well as any magmatic processes which may link pallasites to both IIIAB irons and HED meteorites. In order to achieve this objective, abundances of a suite of elements were measured, including the highly siderophile elements (HSEs), in kamacite, taenite, troilite, schreibersite, chromite and olivine for the pallasites Admire, Imilac, Springwater, CMS 04071. In the diogenites GRO 95555, LAP 91900, and MET 00436, metal, sulfide, spinel, pyroxene, and silica were individually measured.

  10. SBSTM 铬矿球团生产工艺分析%Productive Process Analysis of SBSTM Chromic-ore Pellets

    Institute of Scientific and Technical Information of China (English)



    SBSTM is developed by Outotec company in Finland,which is the more mature production process of producing chromite pelletizing in the world.This process has completely solved the problem of the applying of the ore fines which is bottleneck of high carbon Ferro-chrome production.SBSTM process has a great advantage and broad application prospect.%芬兰 Outotec 公司研发的 SBSTM(Steel Belt Sintering)钢带焙烧铬矿球团技术是国际上比较成熟的铬铁球团生产工艺,它彻底解决了高碳铬铁生产的瓶颈—粉矿使用问题,应用前景广阔。

  11. Experimental Determination of Spinel/Melt, Olivine/Melt, and Pyroxene/Melt Partition Coefficients for Re, Ru, Pd, Au, and Pt (United States)

    Righter, K.; Campbell, A. J.; Humayun, M.


    Experimental studies have identified spinels as important hosts phases for many of the highly siderophile elements (HSE). Yet experimental studies involving chromite or Cr-rich spinel have been lacking. Experimental studies of partitioning of HSEs between silicate, oxides and silicate melt are plagued by low solubilities and the presence of small metallic nuggets at oxygen fugacities relevant to magmas, which interfere with analysis of the phases of interest. We have circumvented these problems in two ways: 1) performing experiments at oxidized conditions, which are still relevant to natural systems but in which nuggets are not observed, and 2) analysis of run products with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), allowing a combination of high sensitivity and good spatial resolution.

  12. LaCrO3 composite coatings for AISI 444 stainless steel solid oxide fuel cell interconnects

    Directory of Open Access Journals (Sweden)

    Wilson Acchar


    Full Text Available Doped lanthanum chromite-based ceramics are the most widely used interconnector material in solid fuel cells (SOFC since they exhibit significant electrical and thermal conductivity, substantial corrosion resistance and adequate mechanical strength at ambient and high temperatures. The disadvantage of this material is its high cost and poor ductility. The aim of this study is to determine the mechanical and oxidation behavior of a stainless steel (AISI 444 with a LaCrO3 deposition on its surface obtained through spray pyrolisis. Coated and pure AISI 444 materials were characterized by mechanical properties, oxidation behavior, X-ray diffraction and scanning electronic microscopy. Results indicated that the coated material displays better oxidation behavior in comparison to pure stainless steel, but no improvement in mechanical strength. Both materials indicate that deformation behavior depends on testing temperatures.

  13. 铬酸盐化

    Institute of Scientific and Technical Information of China (English)


    [ 篇名] Chromate-free conversion coatings for aluminum, [篇名 ] Chrome-Free Conversion Coating for in Service Repair of Aircraft Components, [ 篇名 ] Chromium remediation or release: effect of iron (Ⅱ)sulfate addition on chromium (Ⅵ) leaching from columns of chromite ore processing residue, [篇名] Coating steel wires by polymers in hydrodynamic drawing, [篇名 ] Composition of chromate conversion coatings formed on multi-layered thin films of AA2024-T3 matrix and Al{sub}2Cu, Al{sub}CuMg and Al{sub}20Cu {sub }2(MnFe){ sub } 3, [篇名] Conversion coating science and technology: is it evolving or is it stuck? [篇名] Corrosion and biofouling control in refinery cooling water system using sewage water as a makeup.

  14. Novel Approaches to the Production of Higher Alcohols From Synthesis Gas. Quarterly report, January 1 - March 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, George W


    A modified analytical system was assembled and calibrated, in preparation for a second run with cesium (Cs)-promoted "zinc chromite" catalyst. A new column for the on-line gas chromatography (GC) was purchased for the analysis of various light olefin and paraffin isomers. A run was carried out in the continuous stirred autoclave using the Cs-promoted catalyst. Decahydronaphfialene was used as the slurry liquid. Reaction conditions were 375°C, 2000 psig total pressure, 0.5 H₂/CO ratio, and 5000 sL/Kg (cat.)-hr. Analysis of the data from this run is in progress. A manuscript on the thermal stability of potential slurry liquids was submitted to 'Industrial and Engineering Chemistry Research,' and a paper was presented at the 1997 Spring National Meeting of the American Institute of Chemical Engineers, Houston, Texas.

  15. A FORTRAN program to implement the method of finite elements to compute regional and residual anomalies from gravity data (United States)

    Agarwal, B. N. P.; Srivastava, Shalivahan


    In view of the several publications on the application of the Finite Element Method (FEM) to compute regional gravity anomaly involving only 8 nodes on the periphery of a rectangular map, we present an interactive FORTRAN program, FEAODD.FOR, for wider applicability of the technique. A brief description of the theory of FEM is presented for the sake of completeness. The efficacy of the program has been demonstrated by analyzing the gravity anomaly over Salt dome, South Houston, USA using two differently oriented rectangular blocks and over chromite deposits, Camaguey, Cuba. The analyses over two sets of data reveal that the outline of the ore body/structure matches well with the maxima of the residuals. Further, the data analyses over South Houston, USA, have revealed that though the broad regional trend remains the same for both the blocks, the magnitudes of the residual anomalies differ approximately by 25% of the magnitude as obtained from previous studies.

  16. Catalyst in Basic Oleochemicals

    Directory of Open Access Journals (Sweden)

    Eva Suyenty


    Full Text Available Currently Indonesia is the world largest palm oil producer with production volume reaching 16 million tones per annum. The high crude oil and ethylene prices in the last 3 – 4 years contribute to the healthy demand growth for basic oleochemicals: fatty acids and fatty alcohols. Oleochemicals are starting to replace crude oil derived products in various applications. As widely practiced in petrochemical industry, catalyst plays a very important role in the production of basic oleochemicals. Catalytic reactions are abound in the production of oleochemicals: Nickel based catalysts are used in the hydrogenation of unsaturated fatty acids; sodium methylate catalyst in the transesterification of triglycerides; sulfonic based polystyrene resin catalyst in esterification of fatty acids; and copper chromite/copper zinc catalyst in the high pressure hydrogenation of methyl esters or fatty acids to produce fatty alcohols. To maintain long catalyst life, it is crucial to ensure the absence of catalyst poisons and inhibitors in the feed. The preparation methods of nickel and copper chromite catalysts are as follows: precipitation, filtration, drying, and calcinations. Sodium methylate is derived from direct reaction of sodium metal and methanol under inert gas. The sulfonic based polystyrene resin is derived from sulfonation of polystyrene crosslinked with di-vinyl-benzene. © 2007 BCREC UNDIP. All rights reserved.[Presented at Symposium and Congress of MKICS 2007, 18-19 April 2007, Semarang, Indonesia][How to Cite: E. Suyenty, H. Sentosa, M. Agustine, S. Anwar, A. Lie, E. Sutanto. (2007. Catalyst in Basic Oleochemicals. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3: 22-31.  doi:10.9767/bcrec.2.2-3.6.22-31][How to Link/DOI: || or local:

  17. Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C

    Directory of Open Access Journals (Sweden)

    Crill Patrick


    Full Text Available Abstract Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine. The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution. It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.

  18. Mineral chemistry of the Tissint meteorite: Indications of two-stage crystallization in a closed system (United States)

    Liu, Yang; Baziotis, Ioannis P.; Asimow, Paul D.; Bodnar, Robert J.; Taylor, Lawrence A.


    The Tissint meteorite is a geochemically depleted, olivine-phyric shergottite. Olivine megacrysts contain 300-600 μm cores with uniform Mg# ( 80 ± 1) followed by concentric zones of Fe-enrichment toward the rims. We applied a number of tests to distinguish the relationship of these megacrysts to the host rock. Major and trace element compositions of the Mg-rich core in olivine are in equilibrium with the bulk rock, within uncertainty, and rare earth element abundances of melt inclusions in Mg-rich olivines reported in the literature are similar to those of the bulk rock. Moreover, the P Kα intensity maps of two large olivine grains show no resorption between the uniform core and the rim. Taken together, these lines of evidence suggest the olivine megacrysts are phenocrysts. Among depleted olivine-phyric shergottites, Tissint is the first one that acts mostly as a closed system with olivine megacrysts being the phenocrysts. The texture and mineral chemistry of Tissint indicate a crystallization sequence of: olivine (Mg# 80 ± 1) → olivine (Mg# 76) + chromite → olivine (Mg# 74) + Ti-chromite → olivine (Mg# 74-63) + pyroxene (Mg# 76-65) + Cr-ulvöspinel → olivine (Mg# 63-35) + pyroxene (Mg# 65-60) + plagioclase, followed by late-stage ilmenite and phosphate. The crystallization of the Tissint meteorite likely occurred in two stages: uniform olivine cores likely crystallized under equilibrium conditions; and a fractional crystallization sequence that formed the rest of the rock. The two-stage crystallization without crystal settling is simulated using MELTS and the Tissint bulk composition, and can broadly reproduce the crystallization sequence and mineral chemistry measured in the Tissint samples. The transition between equilibrium and fractional crystallization is associated with a dramatic increase in cooling rate and might have been driven by an acceleration in the ascent rate or by encounter with a steep thermal gradient in the Martian crust.

  19. 任邱球粒陨石

    Institute of Scientific and Technical Information of China (English)



    March 23, 1916 witnessed the fall of the Renqiu meteorite near the town of Renqin(38°40' N, 116°08' E). This meteorite, weighing about 300gm, was found in 1975 by Peking Astronomical Planelarium. X-ray diffraction analyses and microseopie identification have given: olivine (22% Fa), orthopyroxene (14% FS), pLagiocLase,troilite, kamocite, taenite, whitlockite, chromite. Chemieal analyses reveal: SiO2 40.52,TiO2 0.088, Al2O3 2.41, Cr2O3 0.56, FeO 14.20, MnO 0.46, MgO 24.44, CaO 2.01, Na2O 0.96, K2O 0.12, H2O 0.12, H2O- 0.39, H2O+ 0.38, P2O5 0.20, Fe° 6.71, Ni 1.13, FeS 5.48, Co 0.058, Cu 0.015, Zn 0.005, C 0.17, total 100.31. The modal mineral proportion gives : olivine 41.96%, pyroxene 31.90%, plagioclase 10.01%, orthoclase 0.71%, chromite 0.83%, titanite 0.17%, whitlockite 0.44%, metellie Fe-Ni (kamocite and taenite)7.84% and troilite 5.48%. It is shown from the typically chemical analysis of L-group that the meteorite should be classified as an recrystallized L-6 chondrite.

  20. Mineralogy of new Antarctic achondrites with affinity to Lodran and a model of their evolution in an asteroid (United States)

    Takeda, Hiroshi; Mori, Hiroshi; Hiroi, Takahiro; Saito, Jun


    We studied five new Antartic achondrites, MacAlpine Hills (MAC) 88177, Yamato (Y)74357, Y75274, Y791491 and Elephant Moraine (EET)84302 by mineralogical techniques to gain a better understanding of the mineral assemblages of a group of meteorites with an affinity to Lodran (stony-iron meteorite) and their formation processes. This group is being called lodranites. These meteorites contain major coarse-grained orthopyroxene (Opx) and olivine as in Lodran and variable amounts of FeNi metal and troilite etc. MAC88177 has more augite and less FeNi than Lodran; Y74357 has more olivine and contains minor augite; Y791491 contains in addition plagioclase. EET84302 has an Acapulco-like chondritic mineral assembladge and is enriched in FeNi metal and plagioclase, but one part is enriched in Opx and chromite. The EET84302 and MAC88177 Opx crystals have dusty cores as in Acapulco. EET84302 and Y75274 are more Mg-rich than other members of the lodranite group, and Y74357 is intermediate. Since these meteorites all have coarse-grained textures, similar major mineral assemblages, variable amounts of augite, plagioclase, FeNi metal, chromite and olivine, we suggest that they are related and are linked to a parent body with modified chondritic compositions. The variability of the abundances of these minerals are in line with a proposed model of the surface mineral assemblages of the S asteroids. The mineral assemblages can best be explained by differing degrees of loss or movements of lower temperature partial melts and recrystallization, and reduction. A portion of EET84302 rich in metal and plagioclase may represent a type of component removed from the lodranite group meteorites. Y791058 and Caddo County, which were studied for comparison, are plagioclase-rich silicate inclusions in IAB iron meteorites and may have been derived by similar process but in a different body.

  1. Origin and significance of high nickel and chromium concentrations in Pliocene lignite of the Kosovo Basin, Serbia

    Energy Technology Data Exchange (ETDEWEB)

    Ruppert, L.; Finkelman, R.; Boti, E.; Milosavljevic, M.; Tewalt, S.; Simon, M.; Dulong, F. [US Geological Survey, Reston, VA (United States)


    Trace element data from 59 Pliocene lignite cores from the lignite field in the Kosovo Basin, southern Serbia, show localized enrichment of Ni and Cr (33-304 ppm and 8-176 ppm, respectively, whole-coal basis). Concentrations of both elements decrease from the western and southern boundaries of the lignite field. Low-temperature ash and polished coal pellets of selected bench and whole-coal samples were analyzed by X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray analyses. These analyses show that most of the Ni and Cr are incorporated in detrital and, to a lesser degree, in authigenic minerals. The Ni- and Cr-bearing detrital minerals include oxides, chromites, serpentine-group minerals and rare mixed-layer clays. Possible authigenic minerals include Ni-Fe sulfates and sulfides. Analyses of three lignite samples by a supercritical fluid extraction technique indicate that some (1-11%) of the Ni is organically bound, Ni- and Cr-bearing oxides, mixed-layer clays, chromites and serpentine-group minerals were also identified in weathered and fresh samples of laterite developed on serpentinized Palaeozoic peridotite at the nearby Glavica and Cikatovo Ni mines. The detrital Ni- and Cr-bearing minerals identified in lignite samples from the western part of the Kosovo Basin may have been transported into the paleoswamp by rivers that drained the two Palaeocene laterites. Some Ni may have been transported directly into the paleoswamp in solution or, alternatively, Ni may have been leached from detrital minerals by acidic peat water and adsorbed onto organic matter and included into authigenic mineral phases. No minable source of Ni and Cr is known in the southern part of the lignite field; however, the mineral and chemical data from the lignite and associated rocks suggest that such a source area may exist. 15 refs., 10 figs., 6 tabs.

  2. Solid speciation and availability of nickel and chromium in Ni mining spoils (United States)

    Raous, Sophie; Garnier, Jérémie; Sterckeman, Thibaul; Echevarria, Guillaume; Becquer, Thierry; Thomas, Fabien


    Nickel mining of ultramafic laterites generates different types of wastes, topsoils and ores that are too poor in Ni to be currently processed. These are mixed and stored on heaps which could be a potential source of Ni and Cr pollution. Chemical reactivity of the main metal bearing phases present in the mining spoils of Goiás (Brasil) was investigated. Principally a silicated 'saprolite' material and a Fe-oxide rich limonitic material were isolated from the wastes. Their total Ni and Cr content are high, respectively for Ni and Cr : 7,170 and 54,970 mg kg-1 in limonite and 12,200 and 12,650 mg kg-1 in saprolite. The main metal-bearing minerals, identified and localized using XRD, TEM-EDX, Raman spectroscopy and Mossbaüer spectrometry are well-crystallized minerals: goethite (75%), hematite (13%) and chromite in limonite and ferruginous smectite, talc and chromite in saprolite. Single and sequential extractions showed that the amounts of 1M KCl exchangeable Ni and Cr reached respectively 7.1% and 0.03% of total contents in saprolite. Moreover, Cr(VI) extraction by KH2PO4 showed that more than 2% (980 mg kg-1) of total Cr was under this labile toxic form in limonite. This study allowed us to determine the main reactions controlling the Ni and Cr mobility in the spoils i.e. Ni2+ cationic exchange in saprolitic spoil and CrO32- surface complexation in limonitic spoil. This study allowed us to demonstrate the need of chemical rehabilitation of mining wastes in order to avoid the dispersion of the high contents of Ni and Cr available. It constitutes the system definition needed to predict the Cr and Ni mobility in ultramafic mining spoils.

  3. ASTER, ALI and Hyperion sensors data for lithological mapping and ore minerals exploration. (United States)

    Beiranvand Pour, Amin; Hashim, Mazlan


    This paper provides a review of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI), and Hyperion data and applications of the data as a tool for ore minerals exploration, lithological and structural mapping. Spectral information extraction from ASTER, ALI, and Hyperion data has great ability to assist geologists in all disciplines to map the distribution and detect the rock units exposed at the earth's surface. The near coincidence of Earth Observing System (EOS)/Terra and Earth Observing One (EO-1) platforms allows acquiring ASTER, ALI, and Hyperion imagery of the same ground areas, resulting accurate information for geological mapping applications especially in the reconnaissance stages of hydrothermal copper and gold exploration, chromite, magnetite, massive sulfide and uranium ore deposits, mineral components of soils and structural interpretation at both regional and district scales. Shortwave length infrared and thermal infrared bands of ASTER have sufficient spectral resolution to map fundamental absorptions of hydroxyl mineral groups and silica and carbonate minerals for regional mapping purposes. Ferric-iron bearing minerals can be discriminated using six unique wavelength bands of ALI spanning the visible and near infrared. Hyperion visible and near infrared bands (0.4 to 1.0 μm) and shortwave infrared bands (0.9 to 2.5 μm) allowed to produce image maps of iron oxide minerals, hydroxyl-bearing minerals, sulfates and carbonates in association with hydrothermal alteration assemblages, respectively. The techniques and achievements reviewed in the present paper can further introduce the efficacy of ASTER, ALI, and Hyperion data for future mineral and lithological mapping and exploration of the porphyry copper, epithermal gold, chromite, magnetite, massive sulfide and uranium ore deposits especially in arid and semi-arid territory.

  4. H2O-driven generation of picritic melts in the Middle to Late Triassic Stuhini arc of the Stikine terrane, British Columbia, Canada (United States)

    Milidragovic, Dejan; Chapman, John B.; Bichlmaier, Sebastian; Canil, Dante; Zagorevski, Alex


    Basaltic to andesitic compositions predominate island arc magmatism; ultramafic magmas are rare. Ultramafic (MgO = 21-33 wt.%) tuff breccia, lapilli tuff, and ash tuff of the Middle to Upper Triassic Stuhini Group were erupted in the Stikine arc of the North American Cordillera shortly preceding an episode of prolific porphyry Cu-Mo(-Au) mineralization. The ultramafic tuff shows accumulation (20-65%) of olivine (Fo91) and minor chromite into a subalkaline picritic parental magma with MgO ∼16 wt.%. Despite the inferred high MgO content of the parental liquid, chromite phenocrysts record relatively low liquidus temperatures (oxygen fugacities one to three log units above the fayalite-magnetite-quartz (FMQ) buffer. The primary picritic magmas likely contained 5-7 wt.% H2O, inferred on the basis of olivine-liquid thermometry and thermal models for subduction zones, thus alleviating the need for catastrophic thermal perturbations in the mantle wedge. Instead, efficient release of water through slab dehydration at 2.5-3.0 GPa allows generation of picritic melts at ordinary mantle wedge temperatures through moderate degrees (F = 0.10- 0.15) of hydrous flux melting. The volatile-rich nature of the melt and the predominant extensional regime in the overlying lithosphere of Stikinia facilitated the near-adiabatic ascent of the Stuhini Group picrites. The high H2O content of the rapidly ascending picrite melt may have played a key role in transport of metals into the crust of the Stikinia and subsequent porphyry mineralization.

  5. Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C. (United States)

    Neubeck, Anna; Duc, Nguyen Thanh; Bastviken, David; Crill, Patrick; Holm, Nils G


    Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.


    Directory of Open Access Journals (Sweden)

    A. Beiranvand Pour


    Full Text Available Studying the ophiolite complexes using multispectral remote sensing satellite data are interesting because of high diversity of minerals and the source of podiform chromitites. This research developed an approach to discriminate lithological units and detecting host rock of chromitite bodies within ophiolitic complexes using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER and Landsat Thematic Mapper (TM satellite data. Three main ophiolite complexes located in south of Iran have been selected for the study. Spectral transform techniques, including minimum noise fraction (MNF and specialized band ratio were employed to detect different rock units and the identification of high-potential areas of chromite ore deposits within ophiolitic complexes. A specialized band ratio (4/1, 4/5, 4/7 of ASTER, MNF components and Spectral Angle Mapper (SAM on ASTER and Landsat TM data were used to distinguish ophiolitic rock units. Results show that the specialized band ratio was able to identify different rock units and serpentinized dunite as host rock of chromitites within ophiolitic complexes, appropriately. MNF components of ASTER and Landsat TM data were suitable to distinguish ophiolitic rock complexes at a regional scale. The integration of SAM and Feature Level Fusion (FLF used in this investigation discriminated the ophiolitic rock units and prepared detailed geological map for the study area. Accordingly, high potential areas (serpentinite dunite were identified in the study area for chromite exploration targets.The approach used in this research offers the image processing techniques as a robust, reliable, fast and cost-effective method for detecting serpentinized dunite as host rock of chromitite bodies within vast ophiolite complexes using ASTER and Landsat TM satellite data.

  7. Platinum group elements geochemistry of ultramafic and associated rocks from Pindar in Madawara Igneous Complex, Bundelkhand massif, central India

    Indian Academy of Sciences (India)

    V Balaram; S P Singh; M Satyanarayanan; K V Anjaiah


    Ultramafic rocks comprising dunite, harburgite, lehzolite, olivine webserite and websterite occur as intrusives in the form of small hillocks at around Pindar into the granite–gneisses of Bundelkhand Gneissic Complex (BnGC). The peridotites are dominated by olivine cumulates where chromite and precious metal-bearing sulphides crystallized along with pyroxenes, subsequent to crystallization of olivine into the interstitial spaces of cumulates during cooling. Ultramafic rocks of Pindar are characterized by high MgO (up to 46.0 wt%) and FeO (up to 5.8 wt%); low SiO2 (40.8 to 48.0 wt%), TiO2 (0.2 to 0.5 wt%), Al2O3 (∼3.2 wt% av.), CaO(∼ 2.7 wt% av.) and Cu (11 to 73 g/g). Cr and Ni values range from 2297 to 3150 g/g and 2434 to 2767 g/g, respectively. Distribution of Ir (up to 20 ng/g), Ru (27 to 90 ng/g), Rh (3 to 14 ng/g), Pt (18 to 72 ng/g), Pd (10 to 27 ng/g) and Au (22 to 57 ng/g) indicate platinum group element (PGE) and associated gold mineralization in these ultramafic rocks. A mineral phase representing sperrylite (PtAs2) was also identified within the sulphides in Scanning electron microscopy with energy dispersive spectrometer (SEM–EDS) studies. The primitive mantle-normalized siderophile elements pattern shows platinum group element PGE (PPGE) enrichment (Rh, Pt, Pd). Discrimination diagrams of Pd/Ir vs. Ni/Cu, Pd/Pt vs. Ni/Cu, Cu/Pd vs. Pd, and Cu vs. Pd for the peridotites of Pindar attribute to affinity towards komatiite magma, derived from high degree of partial melting of prolonged depleted mantle, and the sulphur saturation condition incurred during the crystallization of chromite which was favourable for PGE mineralization.

  8. Evolution of ore deposits on terrestrial planets (United States)

    Burns, R. G.


    Ore deposits on terrestrial planets materialized after core formation, mantle evolution, crustal development, interactions of surface rocks with the hydrosphere and atmosphere, and, where life exists on a planet, the involvement of biological activity. Core formation removed most of the siderophilic and chalcophilic elements, leaving mantles depleted in many of the strategic and noble metals relative to their chondritic abundances. Basaltic magma derived from partial melting of the mantle transported to the surface several metals contained in immiscible silicate and sulfide melts. Magmatic ore deposits were formed during cooling, fractional crystallization and density stratification from the basaltic melts. Such ore deposits found in earth's Archean rocks were probably generated during early histories of all terrestrial planets and may be the only types of igneous ores on Mars. Where plate tectonic activity was prevalent on a terrestrial planet, temporal evolution of ore deposits took place. Repetitive episodes of subduction modified the chemical compositions of the crust and upper mantles, leading to porphyry copper and molybdenum ores in calc-alkaline igneous rocks and granite-hosted tin and tungsten deposits. Such plate tectonic-induced mineralization in relatively young igneous rocks on earth may also have produced hydrothermal ore deposits on Venus in addition to the massive sulfide and cumulate chromite ores associated with Venusian mafic igneous rock. Sedimentary ore deposits resulting from mechanical and chemical weathering in reducing atmospheres in Archean earth included placer deposits (e.g., uraninite, gold, pyrite ores). Chromite, ilmenite, and other dense unreactive minerals could also be present on channel floors and in valley networks on Mars, while banded iron formations might underlie the Martian northern plains regions. As oxygen evolved in earth's atmosphere, so too did oxide ores. By analogy, gossans above sulfide ores probably occur on Mars

  9. Luminescence and micro-Raman investigations on inclusions of unusual habit in chrysoprase from Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Ayvac Latin-Small-Letter-Dotless-I kl Latin-Small-Letter-Dotless-I , M., E-mail: [Celal Bayar University, Faculty of Arts and Sciences, Department of Physics, 45010 Muradiye-Manisa (Turkey); Garcia-Guinea, J.; Jorge, A. [Museo Nacional Ciencias Naturales, Jose Gutierrez Abascal 2, Madrid 28006 (Spain); Akal Latin-Small-Letter-Dotless-I n, I.; Kotan, Z. [Celal Bayar University, Faculty of Arts and Sciences, Department of Physics, 45010 Muradiye-Manisa (Turkey); Can, N., E-mail: [Celal Bayar University, Faculty of Arts and Sciences, Department of Physics, 45010 Muradiye-Manisa (Turkey)


    Chemical analyses performed on chrysoprase from Turkey have shown many trace elements as well as rare earth impurities. Quantitative chemical analyses of inclusions in minerals can improve our understanding of the chemistry of surface. The environmental scanning electron microscope (ESEM) with an attached X-ray energy dispersive system (EDS) is capable of producing rapid and accurate major element chemical analyses of individual inclusions in crystals larger than about 30 {mu}m in diameter. The samples were examined with lifetime-resolved and spatially-resolved cathodoluminescence (CL), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Spatially resolved CL results at room temperature were recorded for two different areas. Bulk area displays with low CL emission and pores contain iron phases such as chromite, hematite and anatase which cause the green color. For the raw data in the lifetime resolved CL spectrum, at least three broad emission bands were detected in a yellow band of the highest intensity at about 550 nm, a weaker orange band at about 650 nm, and a red band at 720 nm. It is assumed that there are links between the CL emissions and the presence of some transition metal and REE elements, but it is obvious that all trace elements do not play a direct role. Micro-Raman measurements were performed on chrysoprase and these showed a characteristic intensive Raman band peaked at 464 cm{sup -1} which can be inferred to {nu}{sub 2} doubly symmetric bending mode of [SiO{sub 4}/M] centers. Raman spectrum of all inclusions found in the material are also given and discussed in detail. - Highlights: Black-Right-Pointing-Pointer Luminescence and Raman investigations of Chrysoprase. Black-Right-Pointing-Pointer Characteristic intensive Raman band peaked at 464 cm{sup -1}. Black-Right-Pointing-Pointer Ironed phases such as chromite, hematite and anatase.

  10. Synthesis and equation of state of high pressure phase of chromium-bearing spinel (United States)

    Shieh, S. R.; Khan, T.; Prescher, C.; Prakapenka, V.; MI, Z.


    Chromium-bearing spinel (Mg,Fe)Cr2O4 can be found in the Earth's crust, upper mantle, and even in meteorites. Mantle derived chromium-bearing spinel suggests that its high pressure phase may be existing at deep mantle but however its high pressure elastic property is not well understood yet. In situ synchrotron X-ray diffraction studies of magnesiochromite and chromite using the laser-heated diamond anvil cell were performed at GSECARS, Advanced Photon Source, to explore their high pressure phases and elastic property. Our results on magnesiochromite showed dissociation of MgCr2O4 to Cr2O3+MgO at ~15 GPa and to modified Ludwigite (mLd)-type Mg2Cr2O5+Cr2O3 below and above ~1500 K, respectively. At above 20 GPa, only a single phase CaTi2O4-type structure of MgCr2O4 was observed at 1400-2000 K. Pressure-volume data of CaTi2O4 type structure of MgCr2O4 fitted to Birch-Murnaghan equation of state yield zero-pressure volume (V0) = 264.4(8) Å3, bulk modulus (K0) = 185.4(4) GPa, and pressure derivative (K0') = 4; and mLd-type Mg2Cr2O5 yields: V0 = 338.9(8) Å3, K0 = 186.5(6) GPa, K0' = 4. For CaTi2O4 type structure of natural chromite, our fitted P-V data show V0 = 261(1) Å3, K0 = 175.4(2) GPa, and K0' = 4.

  11. Use of synchrotron XANES and Cr-doped coal to further confirm the vaporization of organically bound Cr and the formation of chromium(VI) during coal oxy-fuel combustion. (United States)

    Chen, Juan; Jiao, Facun; Zhang, Lian; Yao, Hong; Ninomiya, Yoshihiko


    Through the use of synchrotron XANES and Cr-doped brown coal, extensive efforts have been made to clarify the volatility of organically bound Cr during oxy-fuel combustion and the mode of occurrence and leachability of Cr in resulting fly ashes. As the continuation of our previous study using raw coal, the Cr-doped coal has been tested in this study to improve the signal-to-noise ratio for Cr K-edge XANES spectra, and hence the accuracy for Cr(VI) quantification. As has been confirmed, the abundant CO(2) as a balance gas for oxy-firing has the potential to inhibit the decomposition of organically bound Cr, thereby favoring its retention in solid ash. It also has the potential to promote the oxidation of Cr(III) to Cr(VI) to a minor extent. Increasing the oxygen partial pressure, particularly in the coexistence of HCl in flue gas, favored the oxidation of Cr(III) into gaseous Cr(VI)-bearing species such as CrO(2)Cl(2). Regarding the solid impurities including Na(2)SO(4) and CaO, Na(2)SO(4) has proven to preferentially capture the Cr(III)-bearing species at a low furnace temperature such as 600 °C. Its promoting effect on the oxidation of Cr(III) to Cr(VI), although thermodynamically available at the temperatures examined here, is negligible in a lab-scale drop tube furnace (DTF), where the particle residence time is extremely short. In contrast, CaO has proven facilitating the capture of Cr(VI)-bearing species particularly oxychloride vapors at 1000 °C, forming Ca chromate with the formulas of CaCrO(4) and Ca(3)(CrO(4))(2) via a direction stabilization of Cr(VI) oxychloride vapor by CaO particle or an indirect oxidation of Cr(III) via the initial formation of Ca chromite. The fly ash collected from the combustion of Cr-doped coal alone has a lower water solubility (i.e., 58.7%) for its Cr(VI) species, due to the formation of Ba/Pb chromate and/or the incorporation of Cr(VI) vapor into a slagging phase which is water-insoluble. Adding CaO to coal increased the

  12. Martian Dunite NWA 2737: Petrographic Constraints on Geological History, Shock Events, and Olivine Color

    Energy Technology Data Exchange (ETDEWEB)

    Treiman,A.; Dyar, M.; McCanta, M.; Noble, S.; Pieters, C.


    Meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ?85% vol. olivine (Mg, molar Mg/(Mg + Fe), of 78.3 {+-} 0.4%), which is notable because it is black in hand sample and brown in thin section. Other minerals include chromite, pyroxenes (augite, pigeonite, orthopyroxene), and diaplectic glass of alkali-feldspar composition. Aqueous alteration is minimal and appears only as slight dissolution of glass. NWA 2737 formed by accumulation of olivine and chromite from a basaltic magma; the other minerals represent magma trapped among the cumulus grains. Minerals are compositionally homogeneous, consistent with chemical equilibration in late and postigneous cooling. Two-pyroxene thermometry gives equilibration temperatures 1150 C, implying a significant time spent at the basalt solidus. Olivine-spinel-pyroxene equilibria give ?825 C (possibly the T of mesostasis crystallization) at an oxidation state of QMF-1. This oxidation state is consistent with low Fe3+ in olivine (determined by EMP, Moessbauer spectra, and synchrotron micro-XANES spectroscopy) and with {approx}10% of the iron in pyroxene being Fe3+. NWA 2737 experienced two shock events. The first shock, to stage S5-S6, affected the olivine by producing in it planar deformation features, intense mosaicism and lattice strain, and abundant droplets of iron-nickel metal, 5-15 nm in diameter. At this stage the olivine became deeply colored, i.e., strongly absorbing at visible and near-infrared (NIR) wavelengths. This shock event and its thermal pulse probably occurred at {approx}170 Ma, the Ar-Ar age of NWA 2737. The colored olivine is cut by ribbons of coarser, uncolored olivine with long axes along [100] and shorter axes on {l_brace}021{r_brace} planes: These are consistent with the easy slip law for olivine [100]{l_brace}021{r_brace}, which is activated at moderate strain

  13. High-temperature hydrothermal activities around suboceanic Moho: An example from diopsidite and anorthosite in Wadi Fizh, Oman ophiolite (United States)

    Akizawa, Norikatsu; Tamura, Akihiro; Fukushi, Keisuke; Yamamoto, Junji; Mizukami, Tomoyuki; Python, Marie; Arai, Shoji


    Reaction products between hydrothermal fluids and uppermost mantle harzburgite-lowermost crustal gabbro have been reported along Wadi Fizh, northern Oman ophiolite. They are named mantle diopsidite (MD) or crustal diopsidite (CD) depending on the stratigraphic level. They construct network-like dikes crosscutting structures of the surrounding harzburgite or gabbro. The MD is mainly composed of diopsidic clinopyroxene, whereas the CD is of diopsidic clinopyroxene and anorthitic plagioclase. Here, we report a new reaction product, crustal anorthosite (CA), from the lowermost crustal section. The CA is always placed in the center of the CD network, and mainly consists of anorthitic plagioclase with minor titanite and chromian minerals such as chromite and uvarovite. Aqueous fluid inclusions forming negative crystals are evenly distributed in minerals of the CA. The fluid inclusions contain angular-shaped or rounded daughter minerals as calcite or calcite-anhydrite composite, which were identified by Raman spectroscopic analysis. We estimated their captured temperature at 530 °C at least by conducting microthermometric analysis of the fluid inclusions. Furthermore, we examined their chemical characteristics by direct laser-shot sampling conducted by laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS). The results indicate that the trapped aqueous fluids contain an appreciable amount of Na, but no K and Cr. Hydrothermal fluids involved in the CA formation transported Cr, which was probably taken up from chromite seams in the uppermost mantle section. Cr got soluble by forming complexes with anions as SO42-, CO32- and Cl-. In addition, these hydrothermal fluids transported Fe, Mg and trace elements (Ti, Sr, Y, Zr and rare-earth elements) governing whole-rock chemical compositions of the MDs, CDs and CAs. Our estimation for the condition of CA formation yielded rather low temperatures (530-600 °C), which indicates a later stage production of the CA

  14. Grain-scale alignment of melt in sheared partially molten rocks: implications for viscous anisotropy (United States)

    Pec, Matej; Quintanilla-Terminel, Alejandra; Holtzman, Benjamin; Zimmerman, Mark; Kohlstedt, David


    Presence of melt significantly influences rheological properties of partially molten rocks by providing fast diffusional pathways. Under stress, melt aligns at the grain scale and this alignment induces viscous anisotropy in the deforming aggregate. One of the consequences of viscous anisotropy is melt segregation into melt-rich sheets oriented at low angle to the shear plane on much larger scales than the grain scale. The magnitude and orientation of viscous anisotropy with respect to the applied stress are important parameters for constitutive models (Takei and Holtzman 2009) that must be constrained by experimental studies. In this contribution, we analyze the shape preferred orientation (SPO) of individual grain-scale melt pockets in deformed partially molten mantle rocks. The starting materials were obtained by isostatically hot-pressing olivine + basalt and olivine + chromite + basalt powders. These partially molten rocks were deformed in general shear or torsion at a confining pressure, Pc = 300 MPa, temperature, T = 1200° - 1250° C, and strain rates of 10-3 - 10-5 s-1to finite shear strains, γ, of 0.5 - 5. After the experiment, high resolution backscattered electron images were obtained using a SEM equipped with a field emission gun. Individual melt pockets were segmented and their SPO analyzed using the paror and surfor methods and Fourier transforms (Heilbronner and Barret 2014). Melt segregation into melt-rich sheets inclined at 15° -20° antithetic with respect to the shear plane occurs in three-phase system (olivine + chromite + basalt) and in two-phase systems (olivine + basalt) twisted to high strain. The SPO of individual melt pockets within the melt-rich bands is moderately strong (b/a ≈ 0.8) and is always steeper (20° -40°) than the average melt-rich band orientation. In the two-phase system (olivine + basalt) sheared to lower strains, no distinct melt-rich sheets are observed. Individual grain-scale melt pockets are oriented at 45° -55

  15. Ultra-reducing conditions in average mantle peridotites and in podiform chromitites: a thermodynamic model for moissanite (SiC) formation (United States)

    Golubkova, Anastasia; Schmidt, Max W.; Connolly, James A. D.


    Natural moissanite (SiC) is reported from mantle-derived samples ranging from lithospheric mantle keel diamonds to serpentinites to podiform chromitites in ophiolites related to suprasubduction zone settings (Luobusa, Dongqiao, Semail, and Ray-Iz). To simulate ultra-reducing conditions and the formation of moissanite, we compiled thermodynamic data for alloys (Fe-Si-C and Fe-Cr), carbides (Fe3C, Fe7C3, SiC), and Fe-silicides; these data were augmented by commonly used thermodynamic data for silicates and oxides. Computed phase diagram sections then constrain the P- T- fO2 conditions of SiC stability in the upper mantle. Our results demonstrate that: Moissanite only occurs at oxygen fugacities 6.5-7.5 log units below the iron-wustite buffer; moissanite and chromite cannot stably coexist; increasing pressure does not lead to the stability of this mineral pair; and silicates that coexist with moissanite have X Mg > 0.99. At upper mantle conditions, chromite reduces to Fe-Cr alloy at fO2 values 3.7-5.3 log units above the moissanite-olivine-(ortho)pyroxene-carbon (graphite or diamond) buffer (MOOC). The occurrence of SiC in chromitites and the absence of domains with almost Fe-free silicates suggest that ultra-reducing conditions allowing for SiC are confined to grain scale microenvironments. In contrast to previous ultra-high-pressure and/or temperature hypotheses for SiC origin, we postulate a low to moderate temperature mechanism, which operates via ultra-reducing fluids. In this model, graphite-/diamond-saturated moderately reducing fluids evolve in chemical isolation from the bulk rock to ultra-reducing methane-dominated fluids by sequestering H2O into hydrous phases (serpentine, brucite, phase A). Carbon isotope compositions of moissanite are consistent with an origin of such fluids from sediments originally rich in organic compounds. Findings of SiC within rocks mostly comprised by hydrous phases (serpentine + brucite) support this model. Both the hydrous phases

  16. Zimbabwean mine dumps and their impacts on river water quality a reconnaissance study (United States)

    Meck, Maideyi; Love, David; Mapani, Benjamin

    Zimbabwe has a substantial number of mines and 67 minerals have been mined in the country since 1900 but at present only 30 different minerals are being mined. Exploitation of a variety of ores, in rocks of diverse composition, provides the potential for a range of pollution problems. The severity and extent of contamination differs with the type of minerals mined. This paper presents part of the results of a broad study, carried out across Zimbabwe, which assessed the potential of different mine tailings dumps to cause environmental problems. The dumps considered in the study were divided into six dump types, namely: gold-mine dumps, base-metal mine dumps (dumps associated with the mining of nickel, zinc, copper and lead), minor-metals mine dumps (dumps associated with mining of antimony, arsenic, and selenium), platinum-group metal mine dumps, chromite and asbestos mine dumps, and sulphur (pyrite) mine dumps. The elemental chemistry of the dumps and physical characteristics (pH, total dissolved solids) of the dumps, tailings’ leachates, and stream waters around the dumps were used to assess the potential of the dumps to pollute water bodies. Samples were collected in both the dry and wet seasons. The dispersion and pollution patterns were derived from Eh-pH conditions around the dumps after considering the mobility of the elements present in these dumps under different Eh-pH conditions. In this paper potential to pollute is considered as the likelihood of the elements to disperse under the prevailing conditions at the dump. The concentrations of elements, type of elements and the potential dispersion and pollution patterns from each dump were used to characterise potential risk of water pollution associated with the different dump types. The results showed a slight increase in concentrations of most elements studied in downstream waters compared to upstream waters. The dump conditions varied from acidic to alkaline, and so the elements studied have different

  17. Age, origin, and thermal evolution of the ultra-fresh 1.9 Ga Winnipegosis Komatiites, Manitoba, Canada (United States)

    Waterton, Pedro; Pearson, D. Graham; Kjarsgaard, Bruce; Hulbert, Larry; Locock, Andrew; Parman, Stephen; Davis, Bill


    The Proterozoic spans the longest portion of earth's history, yet in contrast to the Archaean, the record of komatiites and related high MgO igneous rocks from this Eon is sparse. This paper describes the pristine Palaeoproterozoic Winnipegosis Komatiites, from Manitoba, Canada, which form part of the Circum-Superior Belt large igneous province. We present a comprehensive petrographical investigation, mineral and bulk rock geochemistry, and Al-in-olivine thermometry for the Winnipegosis Komatiites, along with new U-Pb SHRIMP dating of zircons from a mafic unit, which yield an age of 1870.3 ± 7.1 Ma for the Winnipegosis Komatiite Belt. The komatiites are Al-undepleted and dominated by massive olivine porphyritic flows with a median thickness of 6 m. Differentiated flows containing layers of olivine spinifex are present, but rare. Trace element data indicate the komatiites were derived from depleted mantle, and subsequently contaminated with 2-3% continental crust. Temperatures from Al-in-olivine thermometry are consistent with a nominally dry melt, and combined with olivine-melt Mg-Fe partitioning, suggest a parental melt with 24 wt% MgO and a liquidus (olivine) temperature of 1501 °C, approximately 100 °C cooler than their hottest Archaean counterparts. At 1424 °C chromite joined olivine as a crystallising phase. Olivine and chromite phenocrysts were re-mixed with residual melt shortly before or during komatiite eruption, which occurred by the time the magma had cooled to 1321 °C. Combined geochemical and geological evidence requires that the Winnipegosis Komatiites erupted onto rifting continental crust. Their high liquidus temperatures require anomalously hot mantle. Considering the Winnipegosis Komatiites in the context of the broader Circum-Superior Belt, we suggest that these magmas formed from a mantle plume that was deflected towards the margins of the Superior craton by strong gradients in lithospheric thickness. This interpretation of the mode of

  18. Empleo de cromitas refractarias para la obtención de fundentes aglomerados utilizados en la soldadura automática por arco sumergido (SAW

    Directory of Open Access Journals (Sweden)

    Perdomo-González, L.


    Full Text Available In the present work high carbon ferrochrome (load ferrochrome and slags are obtained, starting frora the métallurgie reductive processing of refractory chromites. The obtaining of alloys and slags is studied using an experiment design based in the relationships among components. The chemical compositions of alloys and slags guarantee their application for the conformation of alloys loads and matrix fluxes amassed for the superficial filling by means of submerged arc welding (SAW. The melting-reduction process is carried out in an electric arc furnace.

    En el presente trabajo se obtienen ferrocromo de alto carbono (ferrocromo de carga y escorias a partir del proceso de reducción de cromitas refractarias. Mediante la utilización de un diseño de experimento de relaciones entre componentes, se estudia la obtención de aleaciones y escorias. La composición química de ambas garantiza su aplicación para la conformación de cargas aleantes y matrices de fundentes aglomerados, para el relleno superficial mediante soldadura automática por arco sumergido (SAW. El proceso de fusión-reducción se realiza en un horno eléctrico de arco.

  19. Regional tectonics, geology, magma chamber processes and mineralisation of the Jinchuan nickel-copper-PGE deposit, Gansu Province, China: A review

    Directory of Open Access Journals (Sweden)

    T.M. (Mike Porter


    The Jinchuan ultramafic intrusion was injected into three interconnected sub-chambers, each containing a separate orebody. It essentially comprises an olivine-orthopyroxene-chromite cumulate, with interstitial orthopyroxene, clinopyroxene, plagioclase and phlogopite, and is predominantly composed of lherzolite (∼80%, with an outer rim of olivine pyroxenite and cores of mineralised dunite. Mineralisation occurs as disseminated and net-textured sulphides, predominantly within the dunite, with lesser, PGE rich lenses, late massive sulphide accumulations, small copper rich pods and limited mineralised diopside skarn in wall rock marbles. The principal ore minerals are pyrrhotite (the dominant sulphide, pentlandite, chalcopyrite, cubanite, mackinawite and pyrite, with a variety of platinum group minerals and minor gold. The deposit underwent significant post-magmatic tremolite-actinolite, chlorite, serpentine and magnetite alteration. The volume of the Jinchuan intrusion accounts for <3% of the total parental magma required to generate the contained olivine and sulphide. It is postulated that mafic melt, intruded into the lower crust, hydraulically supported by density contrast buoyancy from below the Moho, ponded in a large staging chamber, where crystallisation and settling formed a lower sulphide rich mush. This mush was subsequently injected into nearby shallow dipping faults to form the Jinchuan intrusion.

  20. Development of a standard reference material for Cr(vi) in contaminated soil (United States)

    Nagourney, S.J.; Wilson, S.A.; Buckley, B.; Kingston, H.M.S.; Yang, S.-Y.; Long, S.E.


    Over the last several decades, considerable contamination by hexavalent chromium has resulted from the land disposal of Chromite Ore Processing Residue (COPR). COPR contains a number of hexavalent chromium-bearing compounds that were produced in high temperature industrial processes. Concern over the carcinogenic potential of this chromium species, and its environmental mobility, has resulted in efforts to remediate these waste sites. To provide support to analytical measurements of hexavalent chromium, a candidate National Institute of Standards and Technology (NIST) Standard Reference Material?? (SRM 2701), having a hexavalent chromium content of approximately 500 mg kg -1, has been developed using material collected from a waste site in Hudson County, New Jersey, USA. The collection, processing, preparation and preliminary physico-chemical characterization of the material are discussed. A two-phase multi-laboratory testing study was carried out to provide data on material homogeneity and to assess the stability of the material over the duration of the study. The study was designed to incorporate several United States Environmental Protection Agency (USEPA) determinative methods for hexavalent chromium, including Method 6800 which is based on speciated isotope dilution mass spectrometry (SIDMS), an approach which can account for chromium species inter-conversion during the extraction and measurement sequence. This journal is ?? The Royal Society of Chemistry 2008.

  1. Determination of the bioaccessibility of chromium in Glasgow soil and the implications for human health risk assessment. (United States)

    Broadway, Andrew; Cave, Mark R; Wragg, Joanna; Fordyce, Fiona M; Bewley, Richard J F; Graham, Margaret C; Ngwenya, Bryne T; Farmer, John G


    The Unified Bioaccessibility Method (UBM), which simulates the fluids of the human gastrointestinal tract, was used to assess the oral bioaccessibility of Cr in 27 Glasgow soils. These included several contaminated with Cr(VI), the most toxic form of Cr, from the past disposal of chromite ore processing residue (COPR). The extraction was employed in conjunction with the subsequent determination of the bioaccessible Cr by ICP-OES and Cr(VI) by the diphenylcarbazide complexation colorimetric procedure. In addition, Cr(III)-containing species were determined by (i) HPLC-ICP-MS and (ii) ICP-OES analysis of gel electrophoretically separated components of colloidal and dissolved fractions from centrifugal ultrafiltration of extracts. Similar analytical procedures were applied to the determination of Cr and its species in extracts of the complexes. Insertion of oral bioaccessible fraction data into the SNIFFER human health risk assessment model identified site-specific assessment criteria (for residential land without plant uptake) that were exceeded by the soil total Cr (3680 mg kg(-1)) and Cr(VI) (1485 mg kg(-1)) concentration at only the most COPR-Cr(VI)-contaminated location. However, the presence of measurable Cr(VI) in the <10 μm fraction of the two most highly Cr(VI)-contaminated soils demonstrated that inhalation of Cr(VI)-containing dust remains the most potentially harmful exposure route.

  2. Size dependence of structure and magnetic properties of CoCr2O4 nanoparticles synthesized by hydrothermal technique (United States)

    Tian, Zhaoming; Zhu, Changming; Wang, Junfeng; Xia, Zhengcai; Liu, Yong; Yuan, Songliu


    The size dependence of structure and magnetic behavior has been investigated on spinel chromite CoCr2O4 nanoparticles (NPs) with different particles from ~2.8 to ~19.7 nm, synthesized by a hydrothermal technique. The microstructure analysis shows that the lattice parameter increases monotonically with reduced particle sizes. Compared with the bulk sample, all synthesized NPs exhibit lower Curie temperature (TC~87 K) from paramagnetic (PM) to collinear short-range ferrimagnetic (FiM) state, and this PM-FiM transition is gradually degraded with decreased particle sizes and nearly vanishes for ~2.8 nm NPs. No magnetic transition from short-range FiM order to long-range spiral spin structure is found at low temperatures contrast to the bulk ones. Instead, a cluster spin-glass (SG) transition appears for NPs with D≤5.4 nm. The dynamic behavior of the cluster SG can be described by a power law with the spin relaxation time in the range of 10-10-10-8 s and critical exponent zv‧=9.9±0.6, in accordance with a three-dimensional Ising SG behavior. The glass transition temperature (Tg) decreases from 16.3 K for ~5.4 nm to 12.8 K for ~2.8 nm NPs.

  3. Caracterización metalográfica de capas cromadas por difusión // Metallographic characterization of diffusion chromized layers

    Directory of Open Access Journals (Sweden)

    J. E. González Ruiz


    Full Text Available En el trabajo se aborda la aplicación de procesos de cromado difusivo obtenidos a partir de mineral de cromo refractariomediante el método metalotérmico. En primer término se realiza una caracterización metalográfica de las capas cromadas pordifusión y sus zonas adyacentes en aceros AISI 1015, 1045, 1055 y W108, de forma adicional se estudia un hierro fundido conuna matriz predominantemente perlítica y un contenido de carbono de 3%.También es tratado el efecto ejercido por el contenido de carbono presente en los materiales anteriormente mencionados sobreel espesor de las capas y en los valores de microdureza alcanzados en la sección transversal de éstas, haciendo énfasis en lazona compuesta por carburos complejos de cromo - hierro.\\Palabras claves: Cromado di fusivo, di fusión, recubrimiento, deposición, cromi ta._______________________________________________________________________AbstractIn this work, a valorization of the influence of base metal carbon contents in the morphology, microhardness and depth of thechromium diffusive layers, obtained from Cuban refractory chromites was realized. For this purpose a low – carbon – steel1015 ( AISI , two medium carbon steel contents 1045 and 1055 ( AISI and a high carbon steel contents W 108 ( AISI .Furthermore, a cast iron with a perlitic matrix was selected.Key words: Di f fusion chromized, deposi t ion, chromi t es, layer.

  4. Cr-isotope fractionation during oxidative weathering of ultramafic rocks and its impact on river waters

    DEFF Research Database (Denmark)

    Paulukat, Cora Stefanie; Døssing, Lasse Nørbye; Mondal, Sisir K.;

    We investigated Cr isotope fractionation during soil formation from Precambrian ultramafic rocks. A soil profile was logged in an active open-cast chromite mine (Sukinda Valley, India). In addition, mine and river waters, as well as seawater were collected to trace the Cr-isotope signal...... into the sea. The aim of the study is to recognize Cr isotope fractionation processes within the mining-area and the impact of the mine runoff on the δ53Cr of the nearby river. The weathering profile shows a distinct upward trend to more negative δ53Cr values. While the well preserved rocks at the base closely...... reflect mantle inventory (-0.124±0.101‰ 1), the δ53Cr from the more weathered upper part of the profile is as low as -1.28±0.022‰. These data are consistent with the findings of Crowe et al. (in press). They demonstrated that Cr(III) becomes oxidised during rock weathering, which leads to an isotopic...

  5. Contamination of soil, medicinal, and fodder plants with lead and cadmium present in mine-affected areas, Northern Pakistan. (United States)

    Nawab, Javed; Khan, Sardar; Shah, Mohammad Tahir; Qamar, Zahir; Din, Islamud; Mahmood, Qaisar; Gul, Nayab; Huang, Qing


    This study aimed to investigate the lead (Pb) and cadmium (Cd) concentrations in the soil and plants (medicinal and fodder) grown in chromite mining-affected areas, Northern Pakistan. Soil and plant samples were collected and analyzed for Pb and Cd concentrations using atomic absorption spectrometer. Soil pollution load indices (PLIs) were greater than 2 for both Cd and Pb, indicating high level of contamination in the study area. Furthermore, Cd concentrations in the soil surrounding the mining sites exceeded the maximum allowable limit (MAL) (0.6 mg kg(-1)), while the concentrations of Pb were lower than the MAL (350 mg kg(-1)) set by State Environmental Protection Administration (SEPA) for agriculture soil. The concentrations of Cd and Pb were significantly higher (P soil of the mining-contaminated sites as compared to the reference site, which can be attributed to the dispersion of toxic heavy metals, present in the bed rocks and waste of the mines. The concentrations of Pb and Cd in majority of medicinal and fodder plant species grown in surrounding areas of mines were higher than their MALs set by World Health Organization/Food Agriculture Organization (WHO/FAO) for herbal (10 and 0.3 mg kg(-1), respectively) and edible (0.3 and 0.2 mg kg(-1), respectively) plants. The high concentrations of Cd and Pb may cause contamination of the food chain and health risk.

  6. Magnetic couplings in the quasi-2D triangular Heisenberg antiferromagnets {alpha}-ACr{sub 2}O{sub 4} (A=Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, V., E-mail: [Laboratoire CRISMAT, ENSICAEN, UMR 6508 CNRS, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Martin, C. [Laboratoire CRISMAT, ENSICAEN, UMR 6508 CNRS, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Damay, F.; Andre, G. [Laboratoire Leon Brillouin, UMR 12, CEA-Saclay, CEA-CNRS, 91191 Gif-sur-Yvette Cedex (France)


    We carried out a comparative study of the A=Ca, Sr, Ba compounds of the {alpha}-ACr{sub 2}O{sub 4} series, a family of layered chromites, which can be classified as S=3/2 quasi-2D triangular Heisenberg antiferromagnets (2DTHAF). The sizeable distortion, with respect to the perfect triangle lattice, of the spin layer topology can be progressively decreased by increasing the size of A{sup 2+}, which leads to an increase of both the average distance between nearest-neighbouring Cr{sup 3+} and of the interplane spacing. The evolution with A{sup 2+} of the antiferromagnetic transition T{sub N}, the intraplane coupling J, and the interplane coupling J Prime has been determined on the basis of magnetization and heat capacity measurements and is discussed in the framework of the standard theoretical models describing quasi 2DTHAF. - Highlights: Black-Right-Pointing-Pointer Increasing the ionic radius of A{sup 2+} has a non-monotonous impact on T{sub N}. Black-Right-Pointing-Pointer The small single-ion anisotropy can split the antiferromagnetic transition. Black-Right-Pointing-Pointer The intraplane coupling is consistent with direct exchange. Black-Right-Pointing-Pointer The interplane coupling derived from standard 2DTHAF models is questionable.

  7. Mineralogy and composition of chromitites and host peridotites from the Colkahan ultramafic complex (Nazdasht mine), Kerman, southeastern Iran (United States)

    Najafzadeh, Ali Reza


    Several chromitite pods of variable sizes are hosted in dunite-harzburgite of the about 14 km2 mining district of Nazdasht, in the Colkahan ultramafic complex, located in the Haji Abad-Esfandagheh district in the Kerman province, southeastern Iran. Olivine, orthopyroxene, and to a lesser extent clinopyroxene of a highly refractory nature, are the primary silicates found in the dunites and harzburgites. The matrix minerals between chromian spinel grains are serpentinized olivine and pyroxene, Cr-rich chlorite (kaemmererite), uvarovite, and veins of magnesite. Chromian spinel mainly occurs as massive chromitite pods and as thin massive chromitite bands together with minor disseminations in dunites and harzburgites. Chromian spinels in massive chromitites show relatively high Cr-numbers (0.60-0.82), Mg-numbers (0.54-0.74) and very low TiO2 contents (averaging 0.16 wt.%) which may reflect the crystallization of chromite from a boninitic magma. The Fe3+-number is very low, down to discrimination diagrams based on mineral chemistry of peridotites are consistent with the differentiation of arc related magmas with boninitic affinity and support the supra-subduction paleogeodynamic setting of Haji Abad-Esfandagheh district previously proposed by some authors.

  8. 溧水陨石的物质成分和球粒结构的研究

    Institute of Scientific and Technical Information of China (English)

    王夕岳; 王思潮


    On September 10, 1978, the Lishui ehondrite fell near Lishui County, Jiangsu Province (31°38'N, 118°59″E). The recovered mass was 498g in weight. Chemical analysis gave: SiO2 39.10, FeO 13.64, TiO2 0.112, Al2O3 1.952, CaO 1.691,MgO 25.46, K2O 0.106, Na2O 1.041, P2O5 0.255, MnO 0.325, Cr2O3 0.533, CO3 0.056, Fe 7.488, Ni 1.293, Pb0.008, Zn 0.062, FeS 6.405, HsO+ 0.10, total 99.683. Fifteen minerals identified in the meteorite are chrysolite (Fa 24%), bronzite,hypersthene, kamaeite, taenite, treifite, plagioclase, chromite, whithockite, apatite,calcite, quartz, zircon, magnetite, and hematite. Modal analysis gave: the first 7 minerals totalling 97.89% (olivine 45.36%, pyroxene 27.98%). The texture of chondrite is very complicated. Chondrules may be classified as monasomatic and polysomatic.Ones there is a wide range of textural type in polysomatie chondrules. Chemico-petrological studies have shown that the meteorite belongs to L-greup ehondrites,and petrologically to type 5.

  9. Production of fatty alcohol from palm oil methyl ester

    Directory of Open Access Journals (Sweden)

    Tongurai, C.


    Full Text Available Fatty alcohol is an important raw material for the production of surfactants, and is currently in demand by markets and has a high potential for growth. Moreover, fatty alcohol can be made from methylester that is produced from fats and natural oil. The production of fatty alcohol involved hydrogenation using the suspension method process and methyl ester in palm oil as the raw material. Copper chromite was used as the catalyst for the hydrogenationreaction and the experiment was proceeded in a close system pressure reaction vessel. The reaction was conducted at approximately 150-250oC, 1100-1700 psig, 2-8% catalyst W/V of methyl ester and reaction timefrom 5-20 hr. After the reaction, the products were analysed to check for percent conversion using gas chromatography (GC. The hydrogenation reaction began at 200oC. The best hydrogenation reaction for theproduction of fatty alcohol occurred at 250oC, 1700 psig, 6% catalyst and reaction time of 20 hr, which gave a purity greater than 97%.

  10. Pure CuCr2O4 nanoparticles: Synthesis, characterization and their morphological and size effects on the catalytic thermal decomposition of ammonium perchlorate (United States)

    Hosseini, Seyed Ghorban; Abazari, Reza; Gavi, Azam


    In the present paper a pure phase of the copper chromite spinel nanoparticles (CuCr2O4 SNPs) were synthesized via the sol-gel route using citric acid as a complexing agent. Then, the CuCr2O4 SNPs has been characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the next step, with the addition of Cu-Cr-O nanoparticles (NPs), the effects of different parameters such as Cu-Cr-O particle size and the Cu/Cr molar ratios on the thermal behavior of Cu-Cr-O NPs + AP (ammonium perchlorate) mixtures were investigated. As such, the catalytic effect of the Cu-Cr-O NPs for thermal decomposition of AP was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA/DSC results showed that the samples with different morphologies exhibited different catalytic activity in different stages of thermal decomposition of AP. Also, in the presence of Cu-Cr-O nanocatalysts, all of the exothermic peaks of AP shifted to a lower temperature, indicating the thermal decomposition of AP was enhanced. Moreover, the heat released (ΔH) in the presence of Cu-Cr-O nanocatalysts was increased to 1490 J g-1.

  11. Rapid high-performance sample digestion of base metal ores using high-intensity infrared radiation with determination by nitrogen-based microwave plasma optical spectrometry

    Directory of Open Access Journals (Sweden)

    Yong Wang


    Full Text Available Infrared sample digestion technology has been rapidly developed in recent years and its application and digestion performance on a variety of ores of base metals was assessed in this study, using a 6-channel infrared digester. Digestion times of 10 min or less were achieved for all base metal ores investigated, including oxides, sulfides, and silicates of Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, W, and Zn. Performance criteria for all samples were excellent, reflected in z values of less than 2 in all cases. Various acid digestion methods were developed for the selected ore samples under high intensity infrared radiation and delivered virtually complete recoveries of all of the elements of interest. Chromite, the notoriously refractory chromium ore was digested within 10 min and gave 100% recovery of chromium. These digestions were accomplished without resorting to perchloric acid and, for most sample types, without hydrofluoric acid, significantly improving the workplace safety for analysts. Between-channel variation of the analyte recoveries from the 6-channel unit were generally below 2%, suggesting that the digestion methods developed with this platform provide reproducible results to meet various sample preparation demands. The high speed and analyte recovery of these digestions makes this methodology especially attractive for prospectors and developers who demand rapid and reliable results from exploration samples.

  12. A Petrographic and Mineralogical Study of Volcanic Rocks from the Mayaxueshan Area, North Qilian Fold Belt, NW China

    Institute of Scientific and Technical Information of China (English)

    徐达伟; 萧炎宏


    The Ordovician volcanic rocks in the Mayaxueshan area have been pervasively altered or metamorphosedand contain abundant secondary minerals such as albite, chlorite, epidote, prehnite, pumpellyite, actinolite, titanite, quartz,and/or calcite. They were denoted as spilites or spilitic rocks in terms of their petrographic features and mineral assem-blages. The metamorphic grades of the volcanic rocks are equivalent to that of the intercalated metaclastic rocks. Thisindicates that both the spilitic volcanic rocks and metaclastic rocks in the Mayaxueshan area have formed as a result ofCaledonian regional metamorphism. We suggest that the previously denoted spilitic rocks or altered volcanic rocks shouldbe re-denoted as metabasalts or metabasaltic rocks. The metamorphic grade of the volcanic rocks increases with their age:prehnite-pumpellyite facies for the upper part of the Middle Ordovician volcanic rocks, prehnite-pumpellyite to lowergreenschist facies for the lower part of the Middle Ordovician volcanic rocks, and lower greenschist facies for the LowerOrdovician volcanic rocks. The P-T conditions are estimated as T = 240 - 290C and P = 1.5 - 4.5 kbar for the lower partof the Middle Ordovician rocks, and T = ~ 300~C for the Lower Ordovician rocks. The variations of mineral assemblagesoccurring at different domains of the volcanic rocks were controlled by the variations of the effective bulk composition inthose domains during metamorphism. The geochemical characteristics of Mg-Al chromite in the Mayaxueshan volcanicrocks are consistent with an origin of island arc environment.

  13. Investigations of Protective Coatings for Castings of High-manganese Cast Steels

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    M. Holtzer


    Full Text Available When cast steel castings are made in moulding sands on matrices of high-silica sand, which has a low fire resistance the problem of theso-called chemical penetration is distinctly visible. Whereas this effect appears to a small degree only when moulding sand matrices are of chromite, zircon or olivine sands. Therefore in case of making castings of high-manganese cast steel (e.g. Hadfield steel sands not containing free silica should be applied (e.g. olivine sand or in case of a high-silica matrix protective coatings for moulds and cores should be used. Two protective coatings, magnesite alcoholic (marked as coating 1 and coating 2 originated from different producers and intended for moulds for castings of the Hadfield steel, were selected for investigations. Examinations of the basic properties were performed for these coatings: viscosity, thermal analysis, sedimentation properties, wear resistance. In order to estimate the effectiveness of protective coatings the experimental castings were prepared. When applying coating 1, the surface quality of the casting was worse and traces of interaction between the casting material (cast steel and the coating were seen. When protective coating 2 was used none interactions were seen and the surface quality was better.

  14. Exsolution of ilmenite and Cr-Ti magnetite from olivine of garnet-wehrlite

    Institute of Scientific and Technical Information of China (English)

    LIU; Xiangwen; JIN; Zhenmin; QU; Jing


    Exsolution of rod-like ilmenite (Ilm) and Cr-Ti magnetite (Mt) have been found in olivine of garnet-wehrlite from the core of Chinese Continental Sciences Drilling (CCSD). Their composition, morphology, crystal structure and their topotaxies with host olivine have been studied in detail by the transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) technique. It shows that rod-like Ilm exsolution reported in this paper has similar characteristic with that of Alpe Arami olivine, while Cr-Ti magnetite exsolution mentioned in this paper has large discrepancy with chromite exsolution in Alpe Arami olivine. These observations suggest that both of the exsolutions found in this paper should be solid solution phases in β-olivine at their first period, then experiencing decomposition of solid solution and therefore forming Ilm and Cr-Ti magnetite exsolution with the pressure decreasing. So, this garnet-wehrlite perhaps had been ever located in mantle transition zone with a minimum depth of 300 km.


    Directory of Open Access Journals (Sweden)

    Fuat IŞIK


    Full Text Available The study area is located within the Central Anatolian Massif around Yeşilhisar (Kayseri. The oldest rock units in the area are ophiolitic rocks which are mainly found as gabbro and dunites. The gabbros are dark green,blackish green coloured and hard, thin-medium granular hipidiomorf textured. Main Composition of gabbroic rocks are hornblende, clinopyroxen, plagioclase, quartz and opaque minerals, sphene and spinel are accessory minerals. The dunites are yellowish, greenish yellow coloured and fragile and stockwork textured. The main components of the dunites are olivine, pyroxen and chromite. The gabbroic rocks are mainly toleitic and can be classified as metaaluminious rocks. Main and trace element variations indicate that the fractionation of hornblende and Fe-Ti oxide minerals. Ratio of Condridite normalized Light REE to Heavy REE displays no enrichment La/LuN = 0.26. Trace and REE contents of the gabbroic rocks indicate that these rocks were a product of MORB like source.

  16. The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys (United States)

    Barrett, Charles A.


    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m (PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. the cobalt levels ranged from 0 wt pct to the nominal commercial content in each alloy. the alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200, and 100 hr, respectively. An oxidation attack parameter, Ka, derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the Cr/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr allys while a 5.0 wt pct Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides, perhaps due to the formation of the omnipresent trirutile Ni(Ta, Cb, Mo, W)2O6. Both scales break down as increasing amounts of NiO are formed.

  17. Oxidation of low cobalt alloys (United States)

    Barrett, C. A.


    Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

  18. Magnetocaloric properties of rare-earth substituted DyCrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    McDannald, A. [Material Science and Engineering Department, University of Connecticut, Storrs, Connecticut 06269 (United States); Jain, M., E-mail: [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)


    Recently, there has been a focus on the need for efficient refrigeration technology without the use of expensive or harmful working fluids, especially at temperatures below 30 K. Solid state refrigeration, based on the magnetocaloric effect, provides a possible solution to this problem. The rare-earth chromites (RCrO{sub 3}), especially DyCrO{sub 3}, with its large magnetic moment dysprosium ion, are potential candidates for such an application. The Dy{sup 3+} ordering transition at low temperatures (<10 K) likely causes a large magnetocaloric response in this material. This study investigates the possibility of tuning the magnetocaloric properties through the use of rare-earth substitution. Both Y{sup 3+} and Ho{sup 3+} substitutions were found to decrease the magnetocaloric response by disrupting the R{sup 3+} ordering. Whereas Er{sup 3+} substitution was found to increase the magnetocaloric response, likely due to an increase in the R{sup 3+} ordering temperature. The large magnetocaloric entropy change of Er{sup 3+} substituted DyCrO{sub 3} (10.92 J/kg K with a relative cooling power of 237 J/kg at 40 kOe and 5 K) indicates that this material system is well suited for low temperature (<30 K) solid state refrigeration applications.

  19. Iron isotopic fractionation and origin of chromitites in the paleo-Moho transition zone of the Kop ophiolite, NE Turkey (United States)

    Zhang, Peng-Fei; Zhou, Mei-Fu; Su, Ben-Xun; Uysal, Ibrahim; Robinson, Paul T.; Avcı, Erdi; He, Yong-Sheng


    The paleo-Moho transition zone (MTZ) of the Kop ophiolite in NE Turkey is mainly composed of dunites, which are locally interlayered with chromitites and contain minor relics of harzburgites. Large Fe isotopic variations were observed for magnesiochromite (- 0.14 to 0.06‰) and olivine (- 0.12 to 0.14‰) from the MTZ rocks. In individual samples, magnesiochromite has lighter Fe isotopic compositions than olivine, which was probably caused by subsolidus Mg-Fe exchange between them. Both magnesiochromite and olivine display an increasing trend of δ56Fe along a profile from chromitite to dunite. This trend reflects continuous fractional crystallization in a magma chamber, which resulted in heavier Fe isotopes concentrated in the evolved magmas. In each cumulate cycle of chromitite and dunite, dunite was formed from relatively evolved melts after massive precipitation of magnesiochromite. Mixing of more primitive and evolved melts in the magma chamber was a potential mechanism for triggering the crystallization of magnesiochromite, generating chromitite layers in the cumulate pile. Before mixing happened, the primitive melts had reacted with mantle harzburgites during their ascendance; whereas the evolved melts may lie on the olivine-chromite cotectic near the liquidus field of pyroxene. Variable degrees of magma mixing and differentiation are expected to generate melts with different δ56Fe values, accounting for the Fe isotopic variations of the Kop MTZ.

  20. Effects of thermal metamorphism on compositions of lunar spinels (United States)

    Misra, K. C.; Taylor, L. A.


    The reported study represents an attempt to evaluate experimentally the compositional and textural changes that are likely to be observed in the Fe-Ti-Cr spinels of lunar igneous rocks by subsequent thermal metamorphism. The Apollo 12 igneous rock, 12018,43, was chosen for this investigation because an earlier study of another fraction of this rock by El Goresy et al. (1971) has reported an almost continuous trend of spinel compositions between Cr-Ulvoespinel and Ti-chromite. The nature of the compositional changes in the heated spinels (and ilmenites) is found to be such that the changes cannot be explained by intragranular adjustments alone. In the heated sample, pyroxene grains adjacent to the high-Ti spinels show a decrease in FeO, and an increase in MgO and Al2O3 at the interface. This may account for the MgO depletion and a part of the FeO enrichment in the high-Ti spinels. It is believed that the heating experiment demonstrates that thermal metamorphism of lunar basalts is likely to modify the compositions of their preexisting spinels (and ilmenites).

  1. Mineralogical composition of the meteorite El Pozo (Mexico): a Raman, infrared and XRD study. (United States)

    Ostrooumov, Mikhail; Hernández-Bernal, Maria del Sol


    The Raman (RMP), infrared (IR) and XRD analysis have been applied to the examination of mineralogical composition of El Pozo meteorite (an ordinary chondrite L5 type; village Valle of Allende, founded in State of Chihuahua, Mexico: 26°56'N and 105°24'W, 1998). RMP measurements in the range of 100-3500 cm(-1) revealed principal characteristic bands of the major minerals: olivine, two polymorph modifications of pyroxene (OPx and CPx) and plagioclase. Some bands of the minor minerals (hematite and goethite) were also identified. All these minerals were clearly distinguished using IR and XRD techniques. XRD technique has shown the presence of some metallic phases such as kamacite and taenite as well as troilite and chromite. These minerals do not have characteristic Raman spectra because Fe-Ni metals have no active modes for Raman spectroscopy and troilite is a weak Raman scatterer. Raman mapping microspectroscopy was a key part in the investigation of El Pozo meteorite's spatial distribution of the main minerals because these samples are structurally and chemically complex and heterogeneous. The mineral mapping by Raman spectroscopy has provided information for a certain spatial region on which a spatial distribution coexists of the three typical mineral assemblages: olivine; olivine+orthopyroxene; and orthopyroxene.

  2. The use of SEM/EDS method in mineralogical analysis of ordinary chondritic meteorite

    Directory of Open Access Journals (Sweden)

    Breda Mirtič


    Full Text Available The aim of this study was to evaluate the potential of scanning electron microscopy coupled with energy dispersiveX-ray spectroscopy (SEM/EDS for determination of mineral phases according to their stoichiometry and assessment of mineral composition of ordinary chondritic meteorite. For the purposes of this study, H3 type ordinary chondritic meteorite Abbott was selected. SEM/EDS allows identification and characterisation of mineralphases, whose size is below the resolution of an optical microscope. Mineral phases in chondrules and interstitial matrix were located in backscattered electron (BSE mode and were assessed from atomic proportions of constituent elements, obtained by the EDS analysis. SEM/EDS analyses of mineral phases showed that Abbott meteorite is characterised by Fe-rich (Fe, Ni-alloy kamacite, Fe-sulphide troilite or pyrrhotite, chromite, Mg-rich olivine, orthopyroxene bronzite or hypersthene, clinopyroxene Al-diopside, acid plagioclase oligoclase, accessory mineral chlorapatite and secondary minerals Fe-hydroxides (goethite or lepidocrocite. Results of semi-quantitative analyses confirmed that most of analysed mineralphases conform well to stoichiometric minerals with minor deviations of oxygen from stoichiometric proportions. Comparison between mineral phases in chondrules and interstitial matrix was also performed, however it showed no significant differences in elemental composition.Differences in chemical composition between minerals in interstitial matrix and chondrules are sometimes too small to be discernedby the SEM/EDS, therefore knowledge of SEM/EDS capabilities is important for correct interpretation of chondrite formation.

  3. Laboratory photometry of regolith analogues: Effect of porosity (United States)

    Kar, A.; Sen, A. K.; Gupta, R.


    New Laboratory phase curves are presented, to examine the effect of porosity on reflectance as a function of phase angle for grain size having dimension about half, twice and those larger than the illuminating wavelength. The experimental setup used for generating reflectance data is a goniometric device developed at the Department of Physics, Assam University, Silchar, India. Some of the well-documented samples having different sizes were chosen; alumina, olivine, basalt, rutile, chromite and iron. The sample surfaces were prepared with different porosities, in order to simulate natural regolith surface as much as possible. The wavelength of observation is 632.8 nm. A model based on the Radiative Transfer Equation is presented here to analyze and model the laboratory data. In the present modelling work, the empirical relation of Hapke, Mie theory and Henyey-Greenstein phase function are used. For particles having dimension about half, twice to the wavelength, Mie theory is used to calculate single scattering albedo. Although the Mie theory is insufficient for describing the scattering properties of particles larger than the wavelength, for such large particle single scattering albedo (SSA) is estimated through method of best fit. It has been found that, the porosity has a distinguishable effect on reflectance. Also the contribution of multiple scattering function for different porosity is examined. Further the results presented in the current work, demonstrates the light scattering properties of a diverse collections of regolith like samples.

  4. Oxidative release of chromium from Archean ultramafic rocks, its transport and environmental impact – A Cr isotope perspective on the Sukinda valley ore district (Orissa, India)

    DEFF Research Database (Denmark)

    Paulukat, Cora Stefanie; Døssing, Lasse Nørbye; Mondal, Sisir K.;


    This study investigates Cr isotope fractionation during soil formation from Archean (3.1–3.3 Ga) ultramafic rocks in a chromite mining area in the southern Singhbhum Craton (Orissa, India). The Cr-isotope signatures of two studied weathering profiles, range from non-fractionated mantle values...... to negatively fractionated values as low as δ53Cr = −1.29 ± 0.04‰. Local surface waters are isotopically heavy relative to the soils. This supports the hypothesis that during oxidative weathering isotopically heavy Cr(VI) is leached from the soils to runoff. The impact of mining pollution is observed downstream...... in controlling the hazardous impact of Cr(VI) on health and environment. The positive Cr isotope signatures of the Brahmani estuary and coastal seawater collected from the Bay of Bengal further indicate that the positively fractionated Cr isotope signal from the catchment area is preserved during its transport...

  5. Reactions of metal ions at surfaces of hydrous iron oxide (United States)

    Hem, J.D.


    Cu, Ag and Cr concentrations in natural water may be lowered by mild chemical reduction involving ferric hydroxide-ferrous ion redox processes. V and Mo solubilities may be controlled by precipitation of ferrous vanadate or molybdate. Concentrations as low as 10-8.00 or 10-9.00 M are readily attainable for all these metals in oxygen-depleted systems that are relatively rich in Fe. Deposition of manganese oxides such as Mn3O4 can be catalyzed in oxygenated water by coupling to ferrous-ferric redox reactions. Once formed, these oxides may disproportionate, giving Mn4+ oxides. This reaction produces strongly oxidizing conditions at manganese oxide surfaces. The solubility of As is significantly influenced by ferric iron only at low pH. Spinel structures such as chromite or ferrites of Cu, Ni, and Zn, are very stable and if locally developed on ferric hydroxide surfaces could bring about solubilities much below 10-9.00 M for divalent metals near neutral pH. Solubilities calculated from thermodynamic data are shown graphically and compared with observed concentrations in some natural systems. ?? 1977.

  6. A Mineralogical study of nickel mattes from the kalgoorlie nickel smelter, kalgoorlie, western australia (United States)

    Page, Michael L.


    The mineralogy of mattes from Western Mining Corporation Limited’s new nickel flash furnace at Kalgoorlie, Western Australia, are dominated by pentlandite, heazlewoodite and awaruite (Ni-Fe alloy). Magnetite, bornite solid-solution, chromite, and fayalite constitute the minor and trace phases. The optical and scanning electron microscopes, electron microprobe, and the X-ray diffractometer were used to examine the matte samples. Pentlandite and awaruite form subhedral to skeletal crystals and are commonly surrounded by complex intergrowths, some showing exsolution textures, of pentlandite, heazlewoodite, and sometimes bornite. In comparison to products from the old flash furnace, which had separate slag cleaning electric furnaces, these new mattes contain much larger quantities of alloy. The large alloy content results from the incorporation of the slag-cleaning electrodes and the addition of coke to the flash furnace, which produce the strong reducing conditions necessary for significant alloy growth. Matte chemistry not only controls which phases are present, but to some extent also influences the composition of these phases. Even though pentlandite-heazlewooditeawaruite-bornite is the equilibrium assemblage in the Ni-Fe-Cu-S system at temperatures below 550 °C, the variation in mineral composition suggests that disequilibrium was present during crystallization of the samples.

  7. Mesosiderites on Vesta: A Hyperspectral VIS-NIR Investigation (United States)

    Palomba, E.; Longobardo, A.; DeSanctis, M. C.; Mittlefehldt, D. W.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Frigeri, A.; Tosi, F.; Zambon, F.; Russell, C. T.; Raymond, C. A.


    The discussion about the mesosiderite origin is an open issue since several years. Mesosiderites are mixtures of silicate mineral fragments or clasts, embedded in a FeNi metal matrix. Silicates are very similar in mineralogy and texture to howardites [1]. This led some scientists to conclude that mesosiderites could come from the same parent parent asteroid of the howardite, eucrite and diogenite (HED) meteorites [2, 3]. Other studies found a number of differences between HEDs and mesosiderite silicates that could be explained only by separate parent asteroids [4]. Recently, high precision oxygen isotope measurements of m esosiderites silicate fraction were found to be isotopically identical to the HEDs, requiring common parent body, i.e. 4 Vesta [5]. Another important element in favor of a common origin was given by the identification of a centimeter-sized mesosiderite clast in a howardite (Dar al Gani 779): a metal-rich inclusion with fragments of olivine, anorthite, and orthopyroxene plus minor amounts of chromite, tridymite, and troilite [6]. The Dawn mission with its instruments, the Infrared Mapping Spectrometer (VIR) [7], the Framing Camera [8] and the Gamma-Ray and Neutron Detector (GRaND) [9] confirmed that Vesta has a composition fully compatible with HED meteorites [10]. We investigate here the possibility to discern mesosiderite rich locations on the surface of Vesta by means of hyperspectral IR images.

  8. Development of novel copper-based sorbents for hot-gas cleanup. Technical report, March 1, 1992--May 31, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Hill, A.H.; Wangerow, J.R. [Institute of Gas Technology, Chicago, IL (United States); Flytzani-Stephanopoulos, M.; Bo, L.; Patel, C. [Massachusetts Inst. of Tech., Cambridge, MA (United States)


    The objective of this investigation is to evaluate several novel copper-based binary oxides for their suitability as regenerable sorbents for hot gas cleanup application in the temperature range of 650{degrees} to 850{degrees}C. During this quarter cyclic sulfidation/regeneration tests of the sorbents Cu{sub 2}Cr-O and Cu-Ce-0 were conducted using different compositions of the feed gases to investigate the effects of H{sub 2}0, H{sub 2} and CO. These tests were conducted in a packed-bed microreactor at 850{degrees}C. The results of these tests showed that H{sub 2} and CO (along with C02) had a significant effect on the H{sub 2}S pre-breakthrough levels, whereas H{sub 2}0 did not have an effect. The physical properties of the fresh and reacted samples of the Cu-2Cr-O and Cu-Ce-0 sorbents prepared in this program and used in the cyclic sulfidation/regeneration tests were also measured. In addition, sulfidation/regeneration tests were conducted using two commercial copper chromite sorbents (G-13 and G-89, United Catalyst, Inc.) and a zinc titanate sorbent (L-3014) in a one-inch fluidized-bed reactor at 650{degrees}C. The G-13 sorbent appears to have a much higher sulfur capacity than the G-89 sorbent.

  9. Estimation of individual dust exposure by magnetopneumography in stainless steel production. (United States)

    Huvinen, M; Oksanen, L; Kalliomäki, K; Kalliomäki, P L; Moilanen, M


    The objectives of the study were to measure the magnetic dust lung burden of workers in stainless steel production by magnetopneumography (MPG) and to investigate the relationship of the results with air-borne concentrations of dust, total and hexavalent chromium as well as urinary excretion of chromium. There were 128 workers from the chromite mine, sintering plant, ferrochrome smelter, stainless steel smelting shop, cold rolling mill and welding shop in the exposed groups and five persons from the office staff in the control group. The remanent magnetic field (RMF) in the lungs was slightly elevated among workers in the ferrochromium and steel smelting shops; the levels were, however, lower than those reported for welders earlier and those observed in the welding/repair shop. Workers in the mine, concentrator and sintering plants and in the cold rolling mill exhibited remanent magnetic fields comparable to the referents. There was a relationship between the RMF and the actual urinary chromium concentration. Miners and concentrator and sintering plant workers showed retarded relaxation rate (ReR) of the remanent magnetic field. However, the RMF of the first two of these groups were low (< 0.1 nT) and this made it difficult to measure the ReR accurately. The duration of exposure correlated weakly but significantly with the relaxation rate, while smoking was not related to it.

  10. Hf, Zr, and REE partition coefficients between ilmenite and liquid - Implications for lunar petrogenesis (United States)

    Nakamura, Y.; Fujimaki, H.; Nakamura, N.; Tatsumoto, M.; Mckay, G. A.


    Partition coefficients (D) between ilmenite and coexisting liquid were determined under near-lunar conditions for Hf, Zr, and REE. Through isotope dilution analysis, ilmenite D values of 0.41 and 0.33 were obtained for Hf and Zr respectively, values significantly lower than those of ilmenite from a kimberlite megacryst. Partition coefficients of REE for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst, and the lunar (Lu) partition coefficient is 0.056. These results suggest that ilmenite was significant in the lunar-Hf evolution of lunar mare basalts. Using lunar and Hf D values for ilmenite, the Lu-Hf evolution of lunar cumulates and the coexisting magma was examined for various crystallization sequences. The Lu-Hf variation trend of most high-Ti mare basalts is explained by a small degree of partial cumulate melting, though a higher degree is required to explain the variation of very low-Ti basalts, green glass, and Apollo 12 low-Ti basalts. Apollo 15 low-Ti basalts may require chromite crystallization as well.

  11. Preparation of sodium bichromate dihydrate by hydrothermal oxidizing reaction%碳素铬铁水热法制红矾钠

    Institute of Scientific and Technical Information of China (English)



    在碳素铬铁水热法制铬酸钠的基础上,充分利用二氧化碳的酸化、催化作用,可在不增添设备和原料的情况下,使反应产物由含少量游离碱的铬酸钠碱性液,转变为含少量铬酸钠的重铬酸钠溶液,同时碱耗下降1/3.该反应可用纯碱代替烧碱.结果表明,采用炉料铬粉水热反应制得的红矾钠成本可望低于铬铁矿焙烧法的成本.%Based on hydrothermal oxidizing reaction of high content carbon ferrochrome for manufacturing sodium chromate, the reaction product sodium chromate alkaline solution containing a small amount of free alkali was converted into sodium bichromate solution containing a small amount of sodium chromate,and meanwhile alkali consumption declined by 1/3,by taking full advantage of acidification and catalytic effect of carbon dioxide, and without adding equipment and raw material. Soda can be used to replace caustic soda in the reaction.Experiment results showed that sodium bichromate cost of applying high content carbon ferrochrome powder hydrothermal oxidizing reaction promises to be less than that of high-temperature chromite roasting.

  12. Review: Perspectives on the metallic interconnects for solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    ZHUWei-zhong; YANMi


    The various stages and progress in the development of interconnect materials for solid oxide fuel cells (SOFCs )over the last two decades are reviewed. The criteria for the application of materials as interconnects are highlighted. Interconnects based on lanthanum chromite ceramics demonstrate many inherent drawbacks and therefore are only useful for SOFCs operating around 1000℃. The advance in the research of anode-supported flat SOFCs facilitates the replacement of ceramic interconnects with metallic ones due to their significantly lowered working temperature. Besides, interconnects made of metals or alloys offer many advantages as compared to their ceramic counterpart. The oxidation response and thermal expansion behaviors of various prospective metallic interconnects are examined and evaluated. The minimization of contact resistance to achieve desired and reliable stack performance during their projected lifetime still remains a highly challenging issue with metallic interconnects. Inexpensive coating materials and techniques may play a key role in promoting the commercialization of SOFC stack whose interconnects are constructed of some current commercially available alloys. Alternatively, development of new metallic materials that are capable of forming stable oxide scales with sluggish growth rate and sufficient electrical conductivity is called for.

  13. Perspectives on the metallic interconnects for solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    ZHU Wei-zhong; YAN Mi


    The various stages and progress in the development of interconnect materials for solid oxide fuel cells (SOFCs) over the last two decades are reviewed. The criteria for the application of materials as interconnects are highlighted. Interconnects based on lanthanum chromite ceramics demonstrate many inherent drawbacks and therefore are only useful for SOFCs operating around 1000 ℃. The advance in the research of anode-supported flat SOFCs facilitates the replacement of ceramic interconnects with metallic ones due to their significantly lowered working temperature. Besides, interconnects made of metals or alloys offer many advantages as compared to their ceramic counterpart. The oxidation response and thermal expansion behaviors of various prospective metallic interconnects are examined and evaluated. The minimization of contact resistance to achieve desired and reliable stack performance during their projected lifetime still remains a highly challenging issue with metallic interconnects. Inexpensive coating materials and techniques may play a key role in pro moting the commercialization of SOFC stack whose interconnects are constructed of some current commercially available alloys. Alternatively, development of new metallic materials that are capable of forming stable oxide scales with sluggish growth rate and sufficient electrical conductivity is called for.


    Institute of Scientific and Technical Information of China (English)

    Slobodan; Jankovic


    Three global metallogenic belts were formed in the world during Mesozoic and post-Mesozoic times. Two of them are situated along the western and eastern Pacific margins, and the third one - the Tethyan Eurasian metallogenic belt (TEMB) is related to the domain of Eurasian plate and flanked on the south by the Afro-Arabian and Indian plates. The general tectonic evolution of the realm where the TEMB was formed is closely connected with the history of Tethys. The emplacement of ore deposits and the development of regional metallogenic units are related to a definitive time interval and to specific tectonic settings such as: (1) Intracontinental rifting along the northern margin of Gondwana and/or fragments already separated; (2) Oceanic environments (i.e. ophiolite complexes and ocean floor sediments) host podiform chromite deposits, volcano-sedimentary cupriferous pyrite deposits (Cyprus type), stratiform manganese deposits, and sporadically PGE deposits; (3) Subduction related settings involve mainly porphyry copper deposits, hydrothermal massive sulphide polymetallic deposits, and epithermal deposits. So far identified mineralization of porphyry copper exceeds in the TEMB over 100 million tons of copper metal; and(4) Collision and post-collision continent-continent setting includes deposits of lead-zinc, antimony, gold, in some sectors tin deposits, as well. The giant deposits of Li-pegmatite occur sporadically.The TEMB is almost a continuously mineralized belt, but within it, some sectors display specific features of tectonic settings, association of elements, minerals and morphogenetic types of mineralization.

  15. Metallic copper in ordinary chondrites (United States)

    Rubin, Alan E.


    Metallic Cu of moderately high purity (approximately 985 mg/g Cu, approximately 15 mg/g Ni) occurs in at least 66% of ordinary chondrites (OC) as heterogeneously distributed, small (typically less than or equal to 20 micrometers) rounded to irregular grains. The mean modal abundance of metallic Cu in H, L and LL chondrites is low: 1.0 to 1.4 x 10(exp -4) vol%, corresponding to only 4 - 5 % of the total Cu in OC whole rocks. In more than 75% of the metallic-Cu-bearing OC, at least some metallic Cu occurs at metallic-Fe-Ni-troilite grain boundaries. In some cases it also occurs within troilite, within metallic Fe-Ni, or at the boundaries these phases form with silicates or chromite. Ordinary chondrites that contain a relatively large number of occurrences of metallic Cu/sq mm have a tendency to have experienced moderately high degrees of shock. Shock processes can cause local melting and transportation of metallic Fe-Ni and troilte; because metallic Cu is mainly associated with these phases, it also gets redistributed during shock events. In the most common petrographic assemblage containing metallic Cu, the Cu is adjacent to small irregular troilite grains surrounded by taenite plus tetrataenite; this assemblage resembles fizzed troilite and may have formed by localized shock melting or remelting of a metal-troilite assemblage.

  16. ZnCr2O4 Nanoparticles: Facile Synthesis, Characterization, and Photocatalytic Properties (United States)

    Mousavi, Zahra; Soofivand, Faezeh; Esmaeili-Zare, Mahdiyeh; Salavati-Niasari, Masoud; Bagheri, Samira


    In this work, zinc chromite (ZnCr2O4) nanostructures have been synthesized through co-precipitation method. The effect of various parameters such as alkaline agent, pH value, and capping agent type was investigated on purity, particle size and morphology of samples. It was found that particle size and morphology of the products could be greatly influenced via these parameters. The synthesized products were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectra, X-ray energy dispersive spectroscopy (EDS), photoluminescence (PL) spectroscopy, diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometry (VSM). The superhydrophilicity of the calcined oxides was investigated by wetting experiments and a sessile drop technique which carried out at room temperature in air to determine the surface and interfacial interactions. Furthermore, the photocatalytic activity of ZnCr2O4 nanoparticles was confirmed by degradation of anionic dyes such as Eosin-Y and phenol red under UV light irradiation. The obtained ZnCr2O4 nanoparticles exhibit a paramagnetic behavior although bulk ZnCr2O4 is antiferromagnetic, this change in magnetic property can be ascribed to finite size effects.

  17. Stainless steel corrosion scale formed in reclaimed water: Characteristics, model for scale growth and metal element release. (United States)

    Cui, Yong; Liu, Shuming; Smith, Kate; Hu, Hongying; Tang, Fusheng; Li, Yuhong; Yu, Kanghua


    Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiform chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HClO results in higher ferric content inside the scales. Cl(-) and SO4(2-) ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales.

  18. The Igwisi Hills extrusive 'kimberlites' (United States)

    Reid, A. M.; Donaldson, C. H.; Dawson, J. B.; Brown, R. W.; Ridley, W. I.


    The petrography and mineral chemistry of volcanic rocks from the Igwisi Hills in Tanzania are discussed. There is considerable evidence to suggest that the Igwisi rocks are extrusive kimberlites: a two-component nature with high P-T minerals in a low P-T matrix; the presence of chrome pyrope, Al enstatite, chrome diopside, chromite and olivine; a highly oxidized, volatile-rich matrix with serpentine, calcite, magnetite, perovskite; high Sr, Zr, and Nb contents; occurrence in a narrow isolated vent within a stable shield area. The Igwisi rocks differ from kimberlite in the lack of magnesian ilmenite, the scarcity of matrix phlogopite, and the overall low alkali content. They apparently contain material from phlogopite-bearing garnet peridotites with a primary mineral assemblage indicative of equilibrium at upper mantle temperatures and pressures. This primary assemblage was brought rapidly to the surface in a gas-charged, carbonate-rich fluid. Rapid upward transport, extrusion, and rapid cooling have tended to prevent reaction between inclusions and the carbonate-rich matrix that might otherwise have yielded a more typical kimberlite.

  19. Comparison of Different Machine Learning Algorithms for Lithological Mapping Using Remote Sensing Data and Morphological Features: A Case Study in Kurdistan Region, NE Iraq (United States)

    Othman, Arsalan; Gloaguen, Richard


    Topographic effects and complex vegetation cover hinder lithology classification in mountain regions based not only in field, but also in reflectance remote sensing data. The area of interest "Bardi-Zard" is located in the NE of Iraq. It is part of the Zagros orogenic belt, where seven lithological units outcrop and is known for its chromite deposit. The aim of this study is to compare three machine learning algorithms (MLAs): Maximum Likelihood (ML), Support Vector Machines (SVM), and Random Forest (RF) in the context of a supervised lithology classification task using Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) satellite, its derived, spatial information (spatial coordinates) and geomorphic data. We emphasize the enhancement in remote sensing lithological mapping accuracy that arises from the integration of geomorphic features and spatial information (spatial coordinates) in classifications. This study identifies that RF is better than ML and SVM algorithms in almost the sixteen combination datasets, which were tested. The overall accuracy of the best dataset combination with the RF map for the all seven classes reach ~80% and the producer and user's accuracies are ~73.91% and 76.09% respectively while the kappa coefficient is ~0.76. TPI is more effective with SVM algorithm than an RF algorithm. This paper demonstrates that adding geomorphic indices such as TPI and spatial information in the dataset increases the lithological classification accuracy.

  20. Preliminary Assessment of Non-Fuel Mineral Resources of Afghanistan, 2007 (United States)



    Introduction Afghanistan has abundant mineral resources, including known deposits of copper, iron, barite, sulfur, talc, chromium, magnesium, salt, mica, marble, rubies, emeralds, lapis lazuli, asbestos, nickel, mercury, gold and silver, lead, zinc, fluorspar, bauxite, beryllium, and lithium (fig. 1). Between 2005 and 2007, the U.S. Agency for International Development (USAID) funded a cooperative study by the U.S. Geological Survey (USGS) and the Afghanistan Geological Survey (AGS) to assess the non-fuel mineral resources of Afghanistan as part of the effort to aid in the reconstruction of that country. An assessment is an estimation or evaluation, in this instance of undiscovered non-fuel mineral resources. Mineral resources are materials that are in such form that economic extraction of a commodity is currently or potentially feasible. In this assessment, teams of scientists from the USGS and the AGS compiled information about known mineral deposits and then evaluated the possible occurrence of undiscovered deposits of all types. Quantitative probabilistic estimates were made for undiscovered deposits of copper, mercury, rare-earth elements, sulfur, chromite, asbestos, potash, graphite, and sand and gravel. These estimates were made for undiscovered deposits at depths less than a kilometer. Other deposit types were considered and discussed in the assessment, but quantitative estimates of numbers of undiscovered deposits were not made. In addition, the assessment resulted in the delineation of 20 mineralized areas for further study, of which several may contain resources amenable to rapid development.

  1. Yarlongite:A New Metallic Carbide Mineral

    Institute of Scientific and Technical Information of China (English)

    SHI Nicheng; BAI Wenji; LI Guowu; XIONG Ming; FANG Qingsong; YANG Jingsui; MA Zhesheng; RONG He


    Yarlongite occurs in ophiolitic chromitite at the Luobusha mine(29°5'N 92°,5'E,about 200 km ESE of Lhasa),Qusum County,Shannan Prefecture,Tibet Autonomous Region,People'S Republic of China.Associated minerals are:diamond,moissanite,wiistite,iridium("osmiridium"), osmium("iridosmine"),periclase,chromite,native irun,native nickel,native chromium,forsterite. Cr-rich diopside,intermetallic compounds Ni-Fe-Cr,Ni-Cr,Cr-C,etc.Yariongite and its associated minerals were handpicked from a large heavy mineral sample of chromitite.The metallic carbides associated with yarlongite are cohenite,tongbaite,khamrabaevite and qusongite(IMA2007.034). Yarlongite occurs as irregular grains,with a size between 0.02 and 0.06 mm,steel-grey colour,H Mohs:5 1/2-6.Tenacity:brittle.Cleavage:{0 0 1}perfect.Fracture:conchoidal.Chemical formula: (Cr4Fe4Ni)∑9C4,or(Cr,Fe,Ni)∑9C4,Crystal system:Hexagonal,Space Group:P63/mc,a=18.839(2)A,C =4.4960(9)A,V=745.7(2)A3,Z=6,Density(calc.)=7.19 g/cm3(with simplified formula).Yarlongite has been approved as a new mineral by the CNMNC(IMA2007-035).Holotype material is deposited at the Geological Museum of China(No.M11650).

  2. 鲁西白彦砾岩中金刚石特征及来源探讨%Study on Diamond Characteristics and Source in Baiyan Conglomerate in Luxi Area

    Institute of Scientific and Technical Information of China (English)



    By comparing characteristics of the diamond which is derived from Baiyan conglomerate with known dia⁃mond original mineral belt in Mengyin and reservoir in this area, combining with content distribution of indicative mineral chromite and content changes of diamond in Baiyan conglomerate, it is indicated that there are three possi⁃ble sources in the diamond of Baiyan conglomerate:first is derived from known diamond original mineral belt in Mengyin county;second is derived from unknown near sources original mine; third is derived from reservoir posi⁃tion in the area.%通过对白彦砾岩中金刚石、蒙阴已知金刚石原生矿带及区内储集层位金刚石特征进行对比,结合对白彦砾岩中金刚石的指示性矿物铬铁矿含量分布及白彦砾岩中金刚石含量变化情况,分析认为白彦砾岩中金刚石有3种可能来源:一是来源于蒙阴已知金刚石原生矿带,二是来源于未知的近源原生矿,三是来源于区内除李官组及本溪组储集层之外的其他储集层。

  3. Magnetism at spinel thin film interfaces probed through soft x-ray spectroscopy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chopdekar, R.V.; Liberati, M.; Takamura, Y.; Kourkoutis, L. Fitting; Bettinger, J. S.; Nelson-Cheeseman, B. B.; Arenholz, E.; Doran, A.; Scholl, A.; Muller, D. A.; Suzuki, Y.


    Magnetic order and coupling at the interfaces of highly spin polarized Fe{sub 3}O{sub 4} heterostructures have been determined by surface sensitive and element specific soft x-ray spectroscopy and spectromicroscopy techniques. At ambient temperature, the interface between paramagnetic CoCr{sub 2}O{sub 4} or MnCr{sub 2}O{sub 4} and ferrimagnetic Fe{sub 3}O{sub 4} isostructural bilayers exhibits long range magnetic order of Co, Mn and Cr cations which cannot be explained in terms of the formation of interfacial MnFe{sub 2}O{sub 4} or CoFe{sub 2}O{sub 4}. Instead, the ferrimagnetism is induced by the adjacent Fe{sub 3}O{sub 4} layer and is the result of the stabilization of a spinel phase not achievable in bulk form. Magnetism at the interface region is observable up to 500 K, far beyond the chromite bulk Curie temperature of 50-95 K.

  4. Gibbs energy of formation of cobalt divanadium tetroxide (United States)

    Jacob, K. T.; Pandit, S. Shashidhara


    The Gibbs energy of formation of V 2O 3-saturated spinel CoV 2O 4 has been measured in the temperature range 900-1700 K using a solid state galvanic cell, which can be represented as Pt, Co + CoV 2O 4 + {V2O3}/{(CaO)}{ZrO2}/{Co} + CoO, Pt. The standard free energy of formation of cobalt vanadite from component oxides can be represented as CoO (rs) + V 2O 3 (cor) → CoV 2O 4 (sp), ΔG° = -30,125 - 5.06 T (± 150) J mole -1. Cation mixing on crystallographically nonequivalent sites of the spinel is responsible for the decrease in free energy with increasing temperature. A correlation between "second law" entropies of formation of cubic 2-3 spinels from component oxides with rock salt and corundum structures and cation distribution is presented. Based on the information obtained in this study and trends in the stability of aluminate and chromite spinels, it can be deduced that copper vanadite is unstable.

  5. Distribution and characteristics of diamonds from Myanmar (United States)

    Win, T. T.; Davies, R. M.; Griffin, W. L.; Wathanakul, P.; French, D. H.


    Diamonds occur in headless placers at several locations within Myanmar. Twenty-six stones from the Momeik area of northern Myanmar and 111 stones from the Theindaw area of southern Myanmar have been studied to characterise their morphology, crystal forms, colour, degree of resorption, surface features, internal structures, mineral inclusions, and nitrogen content and aggregation state. Most stones grew originally as octahedra, but now show very high degrees of resorption, and highly polished surfaces, reflecting transport in a magma. Etch features are abundant, and breakage and abrasion are common, due to alluvial transport. Brown radiation spots are common, suggesting that these diamonds have a long history in surface environments. Cathodoluminescence (CL) images of plates and whole stones commonly display marked oscillatory zoning of yellow and blue bands, outlining octahedral growth zones. Many other stones show uniform yellow CL. Syngenetic mineral inclusions identified thus far are mainly of peridotitic paragenesis and include olivine, chromite and native iron. Infrared spectroscopy studies show that ˜10% of the diamonds have very low-N contents (Type II diamonds). More N-rich diamonds show high degrees of aggregation (Type IaAB). Both types are consistent with derivation from the upper mantle, rather than from crustal metamorphic sources. The primary source of these diamonds is believed to be an alkaline igneous rock (lamproitic rather than kimberlitic) but they may have reached their present locations via a secondary collector such as a sedimentary rock.

  6. Ultrasound Velocity Measurements in the Geometrically Frustrated Spinel MgCr2O4 (United States)

    Watanabe, Tadataka; Kousaka, Yusuke; Tomiyasu, Keisuke


    Magnesium chromite spinel MgCr2O4 is a geometrically frustrated magnet with the Néel temperature TN˜13 K, and the Weiss temperature θW= -390 K. Recent inelastic neutron scattering experiments provided a compelling evidence for the spin molecular ground states in not only the paramagnetic phase but also the antiferromagnetic phase. We performed ultrasound velocity measurements of MgCr2O4 in all the symmetrically independent elastic moduli of C11, (C11-C12)/2, and C44. Temperature dependence of all of these elastic moduli exhibits a remarkable softening in the paramagnetic phase. Taking into account the absence of orbital degrees of freedom in Cr^3+ (3d^3) in MgCr2O4, the spin degrees of freedom should play a significant role for the elastic softening. The most probable origin for the elastic softening in the paramagnetic phase is the strong coupling of the acoustic phonons to the molecular spin fluctuations.

  7. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4 (United States)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji


    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  8. Na-rich character of metasomatic/metamorphic fluids inferred from preiswerkite in chromitite pods of the Khoy ophiolite in Iran: Role of chromitites as capsules of trapped fluids (United States)

    Zaeimnia, Fatemeh; Arai, Shoji; Mirmohammadi, Mirsaleh


    We report a new occurrence of preiswerkite, a rare Na- and Al-rich trioctahedral mica (Na-analog of eastonite), from a high-Al (Cr# of chromite 0.4) chromitite pod of the Khoy meta-ophiolite in northwestern Iran. The preiswerkite is euhedral and associated with Ca-Cr-Al-garnet, clinochlore, titanite, and calcite. Preiswerkite and associated minerals fill cavities in the chromitite pod and are absent in the surrounding peridotites. The preiswerkite-rich aggregate is possibly representative of aqueous fluid supplied to the mantle section of the Khoy ophiolite. Peraluminous conditions, which are indispensable for preiswerkite formation, were established only in the pool of fluid trapped by the high-Al chromitite. The fluid and preiswerkite precipitates were isolated from the peridotite by the chromitite capsule. The Na-rich fluid was a precursor of the serpentinization fluid. The fluid is an analog of the fluid released from the subducting slab, which can precipitate jadeite under high-pressure conditions.

  9. Sulfide mineralization in ultramafic rocks of the Faryab ophiolite complex, southern Kerman

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Rajabzadeh


    Full Text Available Introduction Worldwide, Ni-Cu and PGE magmatic sulfide deposits are confined to the lower parts of stratiform mafic and ultramafic complexes. However, ophiolite mafic and ultramafic complexes have been rarely explored for sulfide deposits despite the fact that they have been extensively explored and exploited for chromite. Sulfide saturation during magmatic evolution is necessary for sulfide mineralization, in which sulfide melts scavenge chalcophile metals from the parent magma and concentrate them in specific lithological zones. The lack of exploration for sulfides in this environment suggests that sulfide saturation is rarely attained in ophiolite-related magmas. Some ophiolites, however, contain sulfide deposits, such as at Acoje in Philippines, and Cliffs in Shetland, U.K. (Evans, 2000; Naldrett, 2004. The Faryab ophiolite complex in southern Kerman Province, the most important mining area for chromite deposits in Iran, is located in the southwest part of the Makran Zone. Evidence of sulfide mineralization has been reported there by some authors (e.g. Rajabzadeh and Moosavinasab, 2013. This paper discusses the genesis of sulfides in the Faryab ophiolite using mineral chemistry of the major mineral phases in different rocks of the ophiolite column in order to determine the possible lithological location of sulfide deposits. Materials and methods Seventy three rock samples from cumulate units were collected from surficial occurrences and drill core. The samples were studied using conventional microscopic methods and the mineralogy confirmed by x-ray diffraction. Electron microprobe analysis was carried out on different mineral phases in order to determine the chemistry of the minerals used in the interpretation of magma evolution in the Faryab ophiolite. Lithologically, the Faryab ophiolite complex is divided into two major parts: the northern part includes magmatic rocks and the southern part is comprised of rocks residual after partial

  10. Sm-Nd, Rb-Sr, and Mn-Cr Ages of Yamato 74013 (United States)

    Nyquist, L. E.; Shih, C.- Y.; Reese, Y.D.


    Yamato 74013 is one of 29 paired diogenites having granoblastic textures. The Ar-39 - Ar-40 age of Y-74097 is approximately 1100 Ma. Rb-Sr and Sm-Nd analyses of Y-74013, -74037, -74097, and -74136 suggested that multiple young metamorphic events disturbed their isotopic systems. Masuda et al. reported that REE abundances were heterogeneous even within the same sample (Y-74010) for sample sizes less than approximately 2 g. Both they and Nyquist et al. reported data for some samples showing significant LREE enrichment. In addition to its granoblastic texture, Y-74013 is characterized by large, isolated clots of chromite up to 5 mm in diameter. Takeda et al. suggested that these diogenites originally represented a single or very small number of coarse orthopyroxene crystals that were recrystallized by shock processes. They further suggested that initial crystallization may have occurred very early within the deep crust of the HED parent body. Here we report the chronology of Y-74013 as recorded in chronometers based on long-lived Rb-87 and Sm-147, intermediate- lived Sm-146, and short-lived Mn-53.

  11. Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii (United States)

    Pitcher, L.; Helz, R.T.; Walker, R.J.; Piccoli, P.


    Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35??years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9??wt.%, with temperatures prior to quench ranging from 1140????C to ambient (110????C). Five eruption samples were also analyzed. Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006-1.40??ppb for Os and 0.0006-2.01??ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF6 in some of the most magnesian samples. Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values

  12. Iron Mineralogy and Aqueous Alteration on Mars from the MER Moessbauer Spectrometers. Chapter 15 (United States)

    Morris, Richard V.; Klingelhoefer, Goestar


    The twin Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) used MIMOS II Moessbauer spectrometers to analyze martian surface materials in the first application of extraterrestrial Moessbauer spectroscopy. The instruments acquired spectra that identified the speciation of Fe according to oxidation state, coordination state, and mineralogical composition and provided quantitative information about the distribution of Fe among oxidation states, coordination states, and Fe-bearing phases. A total of 12 unique Fe-bearing phases were identified: Fe(2+) in olivine, pyroxene, and ilmenite; Fe(2+) and Fe(3+) in magnetite and chromite; Fe(3+) in nanophase ferric oxide (npOx), hematite, goethite, jarosite, an unassigned Fe3+ sulfate, and an unassigned Fe(3+) phase associated with jarosite; and Fe(0) in kamacite. Weakly altered basalts at Gusev crater (SO3 = 2.5 +/- 1.4 wt.% and Fe(3+)/Fe(sub T) = 0.24 +/- 0.11) are widespread on the Gusev plains and occur in less abundance on West Spur and Husband Hill in the Columbia Hills. Altered low-S rocks (SO3 = 5.2 +/- 2.0 wt.% and Fe(3+)/Fe(sub T) = 0.63 +/- 0.18) are the most common type of rock in the Columbia Hills. Ilm-bearing, weakly altered basalts were detected only in the Columbia Hills, as was the only occurrence of chromite in an altered low-S rock named Assemblee. Altered high-S rocks (SO3 > 14.2 wt.% and Fe(3+)/Fe(sub T) = 0.83 +/- 0.05) are the outcrop rocks of the ubiquitous Burns formation at Meridiani Planum. Two Fe(0)-bearing rocks at Meridiani Planum (Barberton and Heat Shield Rock) are meteorites. Laguna Class soil is weakly altered (SO3 = 6 +/- 2 wt.% and Fe(3+)/Fe(sub T) = 0.29 +/- 0.08) and widely distributed at both Gusev crater and Meridiani Planum, implying efficient global mixing processes or a global distribution of precursor rocks with comparable Fe mineralogical compositions. Paso Robles Class soil is heavily altered (SO3 approx. 31 wt.% and Fe(3+)/Fe(sub T) = 0.83 +/- 0

  13. Materials for Advanced Ultrasupercritical Steam Turbines Task 4: Cast Superalloy Development

    Energy Technology Data Exchange (ETDEWEB)

    Thangirala, Mani


    demonstrated the importance of proper heat treat cycles for Homogenization, and Solutionizing parameters selection and implementation. 3) Step blocks casting of Nimonic 263: Carried out casting solidification simulation analysis, NDT inspection methods evaluation, detailed test matrix for Chemical, Tensile, LCF, stress rupture, CVN impact, hardness and J1C Fracture toughness section sensitivity data and were reported. 4) Centrifugal Casting of Haynes 282, weighing 1400 lbs. with hybrid mold (half Graphite and half Chromite sand) mold assembly was cast using compressor casing production tooling. This test provided Mold cooling rates influence on centrifugally cast microstructure and mechanical properties. Graphite mold section out performs sand mold across all temperatures for 0.2% YS; %Elongation, %RA, UTS at 1400°F. Both Stress-LMP and conditional Fracture toughness plots data were in the scatter band of the wrought alloy. 5) Fundamental Studies on Cooling rates and SDAS test program. Evaluated the influence of 6 mold materials Silica, Chromite, Alumina, Silica with Indirect Chills, Zircon and Graphite on casting solidification cooling rates. Actual Casting cooling rates through Liquidus to Solidus phase transition were measured with 3 different locations based thermocouples placed in each mold. Compared with solidification simulation cooling rates and measurement of SDAS, microstructure features were reported. The test results provided engineered casting potential methods, applicable for heavy section Haynes 282 castings for optimal properties, with foundry process methods and tools. 6) Large casting of Haynes 282 Drawings and Engineering FEM models and supplemental requirements with applicable specifications were provided to suppliers for the steam turbine proto type feature valve casing casting. Molding, melting and casting pouring completed per approved Manufacturing Process Plan during 2014 Q4. The partial valve casing was successfully cast after casting methods were

  14. Subduction-related prograde metamorphism of the ultramafic members of the Central-Sudetic Ophiolite (SW Poland) (United States)

    Wojtulek, Piotr; Puziewicz, Jacek; Ntaflos, Theodoros


    The Central-Sudetic Ophiolite (CSO) consists of Ślęża (SM), Braszowice-Brzeźnica (BBM), Szklary (SZM) and Nowa Ruda massifs. Ultramafic rocks occurring in ŚM, BBM and SM have MgO/SiO2 (0.82-1.20) and Al2O3/SiO2 (~0.01) ratios typical for serpentinized mantle peridotites. They are enriched in Cs, Pb and Sb and depleted in Rb, Ba, Nb, La, Ce, Sr, Zr, Er and Y relative to primitive mantle. The serpentinites are antigorite ones, pseudomorphic chrysotile varieties occur sparsely. Serpentinites from each massif contain specific non-serpentine phases. Ślęża serpentinites contain primary olivine-chromite aggregates, olivine and clinopyroxene aggregates interpreted as basaltic melt percolation phases, secondary olivine with magnetite inclusions (locally with cleavage) and secondary microcrystalline olivine-clinopyroxene-magnetite aggregates ("brownish aggregates") with bastite and mesh textures. The BBM serpentinites contain primary olivine-chromite aggregates, primary diopside grains, secondary magnetite-bearing olivine and tremolite. The SZM serpentinites contain olivine, tremolite and enstatite grains. Enstatite (Mg# = 92.8-93.0) contains >0.2 wt.% Cr2O3 and >0.7 Al2O3. All secondary non-serpentine phases are intergrown by antigorite. Very low overall trace element contents, Cs and high Pb-Sb anomalies of the CSO serpentinites are similar to subduction zone related serpentinites not affected by later fluid refertilization. Mineral assemblages shows prograde alteration of the rocks: (1) low-T serpentinization I forming pseudomorphic lizardite-chrysotile serpentinites; (2) antigorite recrystallization; (3) deserpentinization forming secondary olivine with magnetite inclusions, "brownish structures", tremolite and/or enstatite; (4) high-T serpentinization II forming antigorite intergrowths. Alteration degree is different in each massif: rocks from the SM are the most altered, they contain antigorite-olivine-enstatite-tremolite assemblage typical for temperatures

  15. Alpe Arami garnet peridotite from depth >300 km: revisited in 15 years (Invited) (United States)

    Dobrzhinetskaya, L.; Lesher, C. E.; Bozhilov, K. N.; Green, H. W.


    In the mid-1990s we recognized that collisional orogenic belts with UHP metamorphic rocks of crustal affinities, might contain mantle peridotites uplifted from depths of >300km (Dobrzhinetsklaya et al., 1996). We proposed that ilmenite rods + chromite flakes in olivine are the result of exsolution, and that they imply high solubility of TiO2 in Ol at high P-T. The conclusion that the Alpe Arami peridotite massif originates from great depth remains controversial despite the subsequent discovery of Cpx inclusions in Grt containing exsolution lamellae of clinoenstatite displaying antiphase domains. The latter observation requires that the originally precipitated pyroxene had a high-pressure C2/c space group structure consistent with an origin from >8 GPa (~250 km) (Bozhilov et al., 1999). We used confocal laser scanning microscopy to obtain quantitative 3D measurements of Ilm abundance in Ol. We find that Ilm rods can reach >1 vol. % in Ol supporting our contention that Ilm rods exsolved from olivine at 9-12 GPa, e.g. >300 km (Bozhilov et al., 2003). Arguments that Ilm rods hosted by Ol are reaction products from the breakdown of Ti-clinohumite (Risold et al., 2003) are unconvincing given that Ti-clinohumite breakdown does not produce Ilm + chromite that are characteristic of Alpe Arami olivine. Likewise, we have confirmed the high solubility of Ti in olivine at high P-T conditions in multianvil experiments (Dobrzhinetskaya et al., 2000) - findings that are strengthened by the experiments of Tinker & Lesher (2001). Using Focused Ion Beam we prepared TEM foils of the later experiments and confirm that the concentration of TiO2 in Ol increases with pressure under nearly isothermal conditions. Two reactions are proposed to account for these observations. If Ti enters the octahedral site of olivine, either an oxide phase must be formed or a phase richer in SiO2 than olivine must be consumed, leading to reaction 1: 6MgSiO3 + 2FeTiO3 = 2Ti△SiO4 + 3Mg2SiO4 + Fe2SiO4 [1

  16. Petrogenesis of Mesoproterozoic lamproite dykes from the Garledinne (Banganapalle) cluster, south-western Cuddapah Basin, southern India (United States)

    Rao, N. V. Chalapathi; Atiullah; Kumar, Alok; Sahoo, Samarendra; Nanda, Purnendu; Chahong, Ngazimpi; Lehmann, B.; Rao, K. V. S.


    We report mineral chemistry and whole-rock major and trace-element geochemistry for a recent find of Mesoproterozoic (~1.4 Ga) lamproites from the Garledinne (Banganapalle) cluster, south-western part of the Paleo-Mesoproterozoic Cuddapah Basin, southern India. The Garledinne lamproites occur as WNW-ESE-trending dykes that have undergone varying degree of pervasive silicification and carbonate alteration. Nevertheless, their overall texture and relict mineralogy remain intact and provide important insights into the nature of their magmas. The lamproite dykes have porphyritic to weakly porphyritic textures comprising pseudomorphed olivine macrocrysts and microphenocrysts, titanian phlogopite microphenocrysts, spinel having a compositional range from chromite to rarely magnesiochromite, Sr-rich apatite and niobian rutile. The Garledinne and other Cuddapah Basin lamproites (Chelima and Zangamarajupalle) collectively lack sanidine, clinopyroxene, potassic richterite, and titanite and are thus mineralogically distinct from the nearby Mesoproterozoic lamproites (Krishna and Ramadugu) in the Eastern Dharwar Craton, southern India. The strong correlation between various major and trace elements coupled with high abundances of incompatible and compatible trace elements imply that alteration and crustal contamination have had a limited effect on the whole-rock geochemistry (apart from K2O and CaO) of the Garledinne lamproites and that olivine fractionation played an important role in their evolution. The Garledinne lamproites represent small-degree partial melts derived from a refractory (previously melt extracted) peridotitic mantle source that was subsequently metasomatised (enriched) by carbonate-rich fluids/melts within the garnet stability field. The involvement of multiple reservoirs (sub-continental lithospheric mantle and asthenosphere) has been inferred in their genesis. The emplacement of the Garledinne lamproites is linked to extensional events, across the various

  17. Facile synthesis of spinel CuCr{sub 2}O{sub 4} nanoparticles and studies of their photocatalytic activity in degradation of some selected organic dyes

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bappi; Bhuyan, Bishal [Department of Chemistry, National Institute of Technology Silchar, Silchar, 788010, Assam (India); Purkayastha, Debraj Dhar, E-mail: [Department of Chemistry, National Institute of Technology Silchar, Silchar, 788010, Assam (India); Dhar, Siddhartha Sankar, E-mail: [Department of Chemistry, National Institute of Technology Silchar, Silchar, 788010, Assam (India); Behera, Satyananda [Department of Ceramic Engineering, National Institute of Technology Rourkela, Rourkela, 769008, Odisha (India)


    Copper chromite (CuCr{sub 2}O{sub 4}) spinel nanoparticle catalysts have been successfully synthesized employing urea assisted co-precipitation followed by calcination. The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and N{sub 2} adsorption-desorption isotherm (BET). The XRD pattern revealed formation of tetragonal body-centered CuCr{sub 2}O{sub 4} and TEM image showed quasi-spherical particles of size 5–35 nm. The photocatalytic activity of CuCr{sub 2}O{sub 4} was evaluated in degradation of some organic dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB), without and with the assistance of H{sub 2}O{sub 2} under solar irradiation. The CuCr{sub 2}O{sub 4} photocatalysts showed high activity in degradation of RhB (93.6%) and MO (92.3%), but low activity in degradation of MB (80.6%). The catalyst reusability was tested by conducting the degradation of RhB dye with the spent catalyst and it was observed that the catalyst did not show any significant loss in its activity even after five cycles. - Highlights: • CuCr{sub 2}O{sub 4} nanoparticles were synthesized by urea assisted co-precipitation followed by calcination. • The XRD pattern revealed formation of tetragonal body-centered CuCr{sub 2}O{sub 4}. • The TEM images showed the material to be quasi-spherical in shape with sizes 5–35 nm. • CuCr{sub 2}O{sub 4} nanoparticles exhibited pronounced photocatalytic activity.

  18. Elucidating the mechanism of Cr(VI) formation upon the interaction with metal oxides during coal oxy-fuel combustion. (United States)

    Chen, Juan; Jiao, Facun; Zhang, Lian; Yao, Hong; Ninomiya, Yoshihiko


    The thermodynamics underpinning the interaction of Cr-bearing species with basic metal oxides, i.e. K2O, Fe2O3, MgO and CaO, during the air and oxy-fuel combustion of coal have been examined. The synchrotron-based X-ray adsorption near-edge spectroscopy (XANES) was used for Cr speciation. For the oxides tested, Cr(VI) formation is dominated by the reduction potential of the metals. The oxides of Ca(2+) with high reduction potential favored the oxidation of Cr(III), same for K(+). The other two basic metals, Fe2O3 and MgO with lower reduction potentials reacted with Cr(III) to form the corresponding chromites at the temperatures above 600°C. Coal combustion experiments in drop-tube furnace have confirmed the rapid capture of Cr vapors, either trivalent or hexavalent, by CaO into solid ash. The existence of HCl in flue gas favored the vaporization of Cr as CrO2Cl2, which was in turn captured by CaO into chromate. Both Fe2O3 and MgO exhibited less capability on scavenging the Cr(VI) vapor. Particularly, MgO alone exhibited a low capability for capturing the vaporized Cr(III) vapors. However, its co-existence with CaO in the furnace inhibited the Cr(VI) formation. This is beneficial for minimizing the toxicity of Cr in the coal combustion-derived fly ash.

  19. Design of a Compact and Versatile Bench Scale Tubular Reactor

    Directory of Open Access Journals (Sweden)

    R. Prasad


    Full Text Available A compact and versatile laboratory tubular reactor has been designed and fabricated keeping in view of reducing capital cost and minimising energy consumption for gas/vapor-phase heterogeneous catalytic reactions. The reactor is consisted of two coaxial corning glass tubes with a helical coil of glass tube in between the coaxial tubes serving as vaporiser and pre-heater, the catalyst bed is in the inner tube. A schematic diagram of the reactor with detailed dimensions and working principles are described. The attractive feature of the reactor is that the vaporiser, pre-heater and fixed bed reactor are merged in a single compact unit. Thus, the unit minimises separate vaporiser and pre-heater, also avoids separate furnaces used for them and eliminate auxiliary instrumentation such as temperature controller etc. To demonstrate the system operation and illustrate the key features, catalyst screening data and the efficient collection of complete, and accurate intrinsic kinetic data are provided for oxidation of CO over copper chromite catalyst. CO oxidation is an important reaction for auto-exhaust pollution control. The suitability of the versatile nature of the reactor has been ascertained for catalytic reactions where either volatile or vaporizable feeds can be introduced to the reaction zone, e.g. oxidation of iso-octane, reduction of nitric oxide, dehydrogenation of methanol, ethanol and iso-propanol, hydrogenation of nitrobenzene to aniline, etc. Copyright (c 2009 by BCREC. All Rights reserved.[Received: 10 February 2009, Accepted: 9 May 2009][How to Cite: R. Prasad, G. Rattan. (2009. Design of a Compact and Versatile Bench Scale Tubular Reactor. Bulletin of Chemical Reaction Engineering and Catalysis, 4(1: 5-9.  doi:10.9767/bcrec.4.1.1250.5-9][How to Link/ DOI:

  20. Fragments of ancient lunar crust: Ferroan noritic anorthosites from the descartes region of the Moon (United States)

    Norman, M. D.; Alibert, C.; Mcculloch, M. T.


    Noritic anorthosite clasts from breccia 67016 have bulk compositions similar to that of the upper crust of the Moon and petrogenetic affinities with pristine ferroan anorthosites. Rb-Sr and Sm-Nd isotopic compositions of mineral separates from one of these clasts suggest very old (greater than or = 4.4 Ga) ages, but interpretation of these data is complicated by the multi-stage history of the clasts which involved magmatic crystallization, brecciation, subsolidus recrystallization, and sulfide metasomatism. These clasts record some of the earliest events on the Moon, including early crust formation, accretionary bombardment, and degassing of the lunar interior. Modal analyses of these clasts show they are now composed of about 70 percent plagioclase, 28 percent pyroxene, 2 percent troilite, and minor amounts of ilmenite and chromite. No metallic iron, phosphates, or other trace phases were observed. Olivine is very rare, occurring only as relicts within secondary troilite+pyroxene intergrowths which may reflect reaction of olivine with sulfurous vapors. PIXE proton microprobe analyses of the sulfides show that the metasomatism was accompanied by enrichments of Cu, Zn, Ni, Se, and Sb. The clasts have been only mildly shocked since the observed texture was established. Major and minor element mineral compositions are very homogeneous and strikingly similar to those of pristine ferroan anorthosites. Pyroxene compositions indicate equilibration temperatures of 850-900 C. Except for the sulfide and chalcophile element metasomatism, these clasts appear to be essentially monomict and probably represent a noritic member of the ferroan anorthosite suite. Their low Ni contents and Ni/Co ratios are consistent with the interpretation of these clasts as igneous rocks which have escaped mixing with meteoritic material.

  1. Alternative granular media for the metal casting industry. Final report, September 30, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Guichelaar, P.J.; Ramrattan, S.N.; Tieder, R.E. [Michigan Technological Univ., Houghton, MI (United States)


    Silica sand for foundry use is inexpensive to purchase, readily transported and widely available. As a result, it is universally used. However, three factors are becoming increasingly significant as more environmental regulations are promulgated. First, the disposal of waste foundry sand has become an excessively burdensome cost. Second, the phase changes which occur in the silica structure on heating and cooling cause thermal breakdown of the sand into smaller unusable fractions. Third, silica is a relatively weak mineral. Alternatives to silica sand which can withstand the rigors of repetitive reuse must be seriously evaluated as a way to control production costs of the domestic metal casting industry. Chromite sands, olivine sands and carbon sands have each been successfully used to solve operating problems and thus have developed their specific niches in the foundry materials inventory. However, there are several other materials that are candidates for replacing silica sand, such as fused alumina, sintered bauxite and sintered oil well proppants. These media, and others that are generically similar, are manufactured for specific purposes. Compositions and shapes could be readily tailored for used in a metal casting environment of total recycling and materials conservation. This study examines materials that are readily available as alternatives to silica sand from a functionality perspective and a cost perspective. Some of the alternative materials are natural and others are synthetic and thus referring to them as ``sands`` has the potential to cause confusion; the generic term ``granular medium`` is used in this study to mean any material that could functionally substitute for silica sand in the foundry process.

  2. The crater-facies kimberlite system of Tokapal, Bastar District, Chhattisgarh, India (United States)

    Mainkar, Datta; Lehmann, Bernd; Haggerty, Stephen E.


    observed, and phlogopite is very rare. Very limited microdiamond testing (two 18-kg samples) proved negative; however, the composition of chromite grains indicate crystallization in the diamond stability field.

  3. Mineral deposit characteristics and distribution in the James Bay region of Quebec; Styles et repartition des gites metalliferes du territoire de la Baie-James (Quebec)

    Energy Technology Data Exchange (ETDEWEB)

    Gauthier, M. [Montreal Univ., Quebec, Dept. des Sciences de la Terre et de son Atmosphere, PQ (Canada)


    The James Bay region differs even more from the Abitibi Sub-province by the fact that Archean proto-continents proto-continents (older than 2.8 Ga) occur in this region, a situation similar to the Western Superior Province. Moreover, remnants of Meso-Archean arenitic platform sequences found on these proto-cratons contain uraniferous pyritic quartz-pebbles conglomerate that bear many similarities with the Witwater strand deposits of South Africa. As in the Western Superior Province, chromite deposits and PGE-nickel deposits are common in these cratonic terranes. The Kenoran Orogeny affected all the territory. Rare-element pegmatites and orogenic gold deposits are associated with the regional metamorphism and tectonic corridors. A uraniferous pegmatite field in northern James Bay strongly suggests the possibility of metamorphic remobilization of Meso-Archean uraniferous pyritic paleo-placers. Proterozoic continental and platform sequences also overlie the Archean rocks, preserved in a system of grabens that transect the James Bay region. Silver-rich five-element veins (Bi-Co-Ni-Ag-U) occur in horsts surrounding these Proterozoic grabens. Unconformity-related pitchblende vein fields also surround the grabens. Large, medium-grade, strata-bound uranium deposits are found in a basal euxinic lacustrine sequence that locally occurs at the base of Proterozoic red-bed formations. The regional distribution of the Meso-Archean uraniferous pyritic conglomerates, Neo-Archean uraniferous pegmatites and Proterozoic pitchblende veins in the Archean basement, and also of Proterozoic strata-bound U-Cu deposits, suggests a classical example of metallic heritage through time. (author)

  4. Soil-plant relationship of Pteropyrum olivieri, a serpentine flora of Wadh, Balochistan, Pakistan and its use in mineral prospecting

    Directory of Open Access Journals (Sweden)

    Shahid Naseem


    Full Text Available Biogeochemical investigation of Pteropyrum olivieri, a flora of Wadh area in perspective of plant-soil-rock relationship has been made. It is a native of Irano-Turanian region which extended into Saharo-Sindian region of Pakistan. The distribution of P. olivieri and some other co-ecological flora in relation to lithology was also discussed. Field observations showed its controlled population on the serpentine soil. The average abundance of Mg and Ca in soil was estimated as 2.43% and 5.46 respectively. The Mg/Ca ratio of the soils of the study area was below unity (0.445, indicating pedogenesis from serpentinite. Quantitative estimation of Cr, Ni, Co and Cu in soils and plant ash was made. Distribution of these elements has been discussed in context with soil chemistry, average abundance in plant ash and the exclusion mechanism of the flora. The concentration of Cr, Ni and Co in the twigs of P. olivieri is more than the average abundance in the plant ash, while Cu concentration was less. Relationship among Cr, Ni, Co and Cu has been established using scatter-grams to evaluate biogeochemistry of the P. olivieri. Bio-concentration factor (BCF of the specie attributed Co>Cu>Ni>Cr trend. Present study signifies a number of anomalous zones which can be utilized for the exploration of new hidden mineral deposits in and around Wadh area. The rocks in the anomalous zone served as good host for podiform chromite and associated mineralization.

  5. 常德陨石雨物质成分和球粒结构的初步研究

    Institute of Scientific and Technical Information of China (English)



    On Mareh 11,1977,the Changde stone meteorite shower fell near the town of Changde,Hunan Province(29°05'N,111°45'E).The total recovered mass vas 1.81kg in weight(900g,254g,220g,184g,50g,20g,11.8g,20g,20g,18.3g,and 113g)X-ray diffraction analyses and microseopic identification have indicated the presence of the following minerals:olivine(175,Fa),orthopyroxene(18% Fs),elinopyroxene,plagioclase,orthoclase,whitlockite,kamocite,taenite,troilite and chromite,Turbid glass has been found in chondrules.Shock effect has bee also observed in olivinc and pyroxene.Chemical analyses have given;SiO2 37.61,TiO2 0.086,Al2O3 2.18,Cr2O3 0.52,FeO 8.00,MnO 0.18,MgO22.87,CaO 1.92,Na2O 0.87,K2O 0.11,H2O- 0.06,H2O+0.06,P2O5 0.21,Fe°18.44,Ni 1.80,Co0.091,Cu0.014,Zn0.006,FeS5.59,C 0.16,total 100.78 Model analysis gives;olivine 26.86%,pyroxene 36.62%,plagioclase 9.06%,orthoclase 0.65%,whitlockite 0.46%,titanite 0.17%,kamocite and taenite 20.24%,troilite 5.59%,Chemieo-petrological stndies have shown that the meteorite bclongs to H-group chondrites,and petrologically to Type 5.Based upon the textures of the chondrules,a model of the evolution for the Changde chondrite is presented.

  6. Olivine in Martian Meteorite Allan Hills 84001: Evidence for a High-Temperature Origin and Implications for Signs of Life (United States)

    Shearer, C. K.; Leshin, L. A.; Adcock, C. T.


    Olivine from Martian meteorite Allan Hills (ALH) 84001 occurs as clusters within orthopyroxene adjacent to fractures containing disrupted carbonate globules and feldspathic shock glass. The inclusions are irregular in shape and range in size from approx. 40 microns to submicrometer. Some of the inclusions are elongate and boudinage-like. The olivine grains are in sharp contact with the enclosing orthopyroxene and often contain small inclusions of chromite The olivine exhibits a very limited range of composition from Fo(sub 65) to Fo(sub 66) (n = 25). The delta(sup 18)O values of the olivine and orthopyroxene analyzed by ion microprobe range from +4.3 to +5.3% and are indistinguishable from each other within analytical uncertainty. The mineral chemistries, O-isotopic data, and textural relationships indicate that the olivine inclusions were produced at a temperature greater than 800 C. It is unlikely that the olivines formed during the same event that gave rise to the carbonates in ALH 84001, which have more elevated and variable delta(sup 18)O values, and were probably formed from fluids that were not in isotopic equilibrium with the orthopyroxene or olivine The reactions most likely instrumental in the formation of olivine could be either the dehydration of hydrous silicates that formed during carbonate precipitation or the reduction of orthopyroxene and spinel If the olivine was formed by either reaction during a postcarbonate beating event, the implications are profound with regards to the interpretations of McKay et al. Due to the low diffusion rates in carbonates, this rapid, high-temperature event would have resulted in the preservation of the fine-scale carbonate zoning' while partially devolatilizing select carbonate compositions on a submicrometer scale. This may have resulted in the formation of the minute magnetite grains that McKay et al attributed to biogenic activity.

  7. The Distant Morphological and Petrological Features of Shock Melt Veins in the Suizhou L6 Condrite

    Energy Technology Data Exchange (ETDEWEB)

    X Xie; Z Sun; M Chen


    The morphology and petrology of distinct melt veins in the Suizhou L6 chondrite have been investigated using scanning electron microscopy, electron microprobe analyses, and Raman spectroscopy, synchrotron energy-dispersive diffraction, and transmission electron microscopy. It is found that the melt veins in the Suizhou meteorite morphologically are the simplest, straightest, and thinnest among all shock veins known from meteorites. At first glance, these veins look like fine fractures, but petrologically they are solid melt veins of chondritic composition and consist of fully crystalline materials of two distinct lithological assemblages, with no glassy material remaining. The Suizhou melt veins contain the most abundant high-pressure mineral species when compared with all other veins known in chondrites. Thus, these veins in Suizhou are classified as shock veins. All rock-forming and almost all accessory minerals in the Suizhou shock veins have been transformed to their high-pressure polymorphs, and no fragments of the precursor minerals remain in the veins. Among the 11 high-pressure mineral phases identified in the Suizhou veins, three are new high-pressure minerals, namely, tuite after whitlockite, xieite, and the CF phase after chromite. On the basis of transformation of plagioclase into maskelynite, it is estimated that the Suizhou meteorite experienced shock pressures and shock temperatures up to 22 GPa and 1000 C, respectively. Shearing and friction along shock veins raised the temperature up to 1900-2000 C and the pressure up to 24 GPa within the veins. Hence, phase transition and crystallization of high-pressure minerals took place only in the Suizhou shock veins. Fast cooling of the extremely thin shock veins is regarded as the main reason that up to 11 shock-induced high-pressure mineral phases could be preserved in these veins.

  8. Spatial Evolution of the Chromium Contamination in Soils from the Assopos to Thiva Basin and C. Evia (Greece and Potential Source(s: Anthropogenic versus Natural Processes

    Directory of Open Access Journals (Sweden)

    Charalambos Vasilatos


    Full Text Available The investigation of the contamination in soil, plants and groundwater revealed a spatial evolution, with an increasing trend in the Cr, Fe, Ni, Mn and Co contents in soils from the Assopos to Thiva basin, followed by C. Evia and Ni-laterite deposits, suggesting that the latter and their parent ophiolites are a potential source for these metals. In contrast, the contamination in groundwater by Cr(VI, ranging from 2 to 360 μg/L Cr, and a varying degree of salinization is probably due to both human activities and natural processes. A diverse source for the contamination of soil and groundwater in the Assopos-Thiva basins is consistent with the increasing trend of the Mg/Si ratio and Cr(VI concentration in water. The use of deep karst-type aquifer instead of the shallow-Neogene one may provide a solution to the crucial environmental problem. The selective extraction by EDTA and alkaline solution showed that Cr and Fe are less available than Mn. The Cr contents in plants range from <1 to tens of mg/kg, due probably to the high resistance of chromite. However, the average Crtotal contents in plants/crops are higher than normal or sufficient values, whilst Crtotal accumulation [(% metals in plants × 100/metal in soil] and Cr(VI accumulation are relatively low. There is a very good positive correlation between accumulation factors for Cr and Fe (R2 = 0.92, suggesting a similarity concerning their uptake.

  9. Method and device for electroextraction of heavy metals from technological solutions and wastewater (United States)

    Khalemsky, Aron Mikhailov; Payusov, Sergei Abramovic; Kelner, Leonid; Jo, Jae


    The basic principles of the method for heavy metals electroextraction from technological solutions and wastewater includes pretreating to remove Chromium-6 and high concentrations of heavy metals and periodically treating in a six-electrode bipolar cylindrical electroreactor made of non-conducting material to achieve lower accepted levels of impurities. Six cylindrical steel electrodes form two triode stacks and are fed with three-phase alternating current of commercial frequency (50-60 Hz), which can be pulsed. Each phase of the three-phase current is connected to three electrodes of one triode stack or in parallel to two triode stacks. The parallel connection of three-phase current to two triode stacks is performed so that the same phase of the three phase current is connected in parallel with each two opposite electrodes of six electrodes located along the periphery, or with two adjacent electrodes. A bipolar stationary aluminum electrode is situated in the inter-electrode space. In one of the embodiments, the bipolar electrode is made of a perforated heat-resistant plastic container filled with secondary aluminum and duralumin scrap. In another embodiment, the bipolar electrode of aluminum or duralumin scrap may be made without a perforated container and is placed in the inter-electrode space as a bulk scrap. In this case, to prevent shorts, each of six steel electrodes is placed in isolated perforated plastic shell with holes of 5 mm in diameter. Non-ferrous metals are extracted in a form of ferrite-chromites, and aluminates as well as hydroxyl salts deposited in the inter-electrode space without electrolysis deposits on electrodes. Deposits are separated from solution by known methods of filtration.

  10. Innovative methodology for recovering titanium and chromium from a raw ilmenite concentrate by magnetic separation after modifying magnetic properties. (United States)

    Lv, Jin-Fang; Zhang, Han-Ping; Tong, Xiong; Fan, Chun-Lin; Yang, Wen-Tao; Zheng, Yong-Xing


    Raw ilmenite concentrate containing Cr can be either as a resource or as one kind of the most hazardous solid waste. In order to recover titanium and chromium from the raw concentrate which was separated from the Promenade deposit, Gaza province, Mozambique, an innovative technology using modification of magnetic property followed by magnetic separation was proposed. Magnetic property, phase and surface morphology of the sample before and after oxidizing roasting were firstly characterized by magnetism, chemistry, XRD and MLA analyses to interpret the mechanism of oxidizing roasting of the ilmenite. Then, these factors such as oxidizing roasting temperature, residence time and magnetic induction affecting on magnetic separation performance were examined and the optimum process parameters were determined. A commercial concentrate containing 47.94% TiO2 and 0.23% Cr2O3 was obtained and the recovery of TiO2 and Cr2O3 was 78.52% and 5.42%, respectively. The tailing obtained was preliminarily concentrated by a high-intensity magnetic separator and a rough chromite concentrate was gained. In order to further purify the rough one, reducing roasting was carried out to transform the minerals containing hematite into the minerals containing magnetite, followed by a low-intensity magnetic separation. The effects of these parameters such as temperature, carbon powder dosage, holding time and magnetic induction on magnetic separation performance were investigated and the optimal conditions were determined. A concentrate containing 28.65% Cr2O3 was obtained and the total recovery of Cr2O3 was 84.18%.

  11. A chilled margin of komatiite and Mg-rich basaltic andesite in the western Bushveld Complex, South Africa (United States)

    Maier, W. D.; Barnes, S.-J.; Karykowski, B. T.


    A chill sequence at the base of the Lower Zone of the western Bushveld Complex at Union Section, South Africa, contains aphanitic Mg-rich basaltic andesite and spinifex-textured komatiite. The basaltic andesite has an average composition of 15.2 % MgO, 52.8 % SiO2, 1205 ppm Cr, and 361 ppm Ni, whereas the komatiite has 18.7 % MgO, 1515 ppm Cr, and 410 ppm Ni. Both rock types have very low concentrations of immobile incompatible elements (0.14-0.72 ppm Nb, 7-31 ppm Zr, 0.34-0.69 ppm Th, 0.23-0.27 wt% TiO2), but high PGE contents (19-23 ppb Pt, 15-16 ppb Pd) and Pt/Pd ratios (Pt/Pd 1.4). Strontium and S isotopes show enriched signatures relative to most other Lower Zone rocks. The rocks could represent a ~20 % partial melt of subcontinental lithospheric mantle. This would match the PGE content of the rocks. However, this model is inconsistent with the high SiO2, Fe, and Na2O contents and, in particular, the low K2O, Zr, Hf, Nb, Ta, Th, LREE, Rb, and Ba contents of the rocks. Alternatively, the chills could represent a komatiitic magma derived from the asthenosphere that underwent assimilation of the quartzitic floor accompanied by crystallization of olivine and chromite. This model is consistent with the lithophile elements and the elevated Sr and S isotopic signatures of the rocks. However, in order to account for the high Pt and Pd contents of the magma, the mantle must have been twice as rich in PGE as the current estimate for PUM, possibly due to a component of incompletely equilibrated late veneer.

  12. Remote compositional analysis of lunar olivine-rich lithologies with Moon Mineralogy Mapper (M3) spectra (United States)

    Isaacson, P.J.; Pieters, C.M.; Besse, S.; Clark, R.N.; Head, J.W.; Klima, R.L.; Mustard, J.F.; Petro, N.E.; Staid, M.I.; Sunshine, J.M.; Taylor, L.A.; Thaisen, K.G.; Tompkins, S.


    A systematic approach for deconvolving remotely sensed lunar olivine-rich visible to near-infrared (VNIR) reflectance spectra with the Modified Gaussian Model (MGM) is evaluated with Chandrayaan-1 Moon Mineralogy Mapper (M 3) spectra. Whereas earlier studies of laboratory reflectance spectra focused only on complications due to chromite inclusions in lunar olivines, we develop a systematic approach for addressing (through continuum removal) the prominent continuum slopes common to remotely sensed reflectance spectra of planetary surfaces. We have validated our continuum removal on a suite of laboratory reflectance spectra. Suites of olivine-dominated reflectance spectra from a small crater near Mare Moscoviense, the Copernicus central peak, Aristarchus, and the crater Marius in the Marius Hills were analyzed. Spectral diversity was detected in visual evaluation of the spectra and was quantified using the MGM. The MGM-derived band positions are used to estimate the olivine's composition in a relative sense. Spectra of olivines from Moscoviense exhibit diversity in their absorption features, and this diversity suggests some variation in olivine Fe/Mg content. Olivines from Copernicus are observed to be spectrally homogeneous and thus are predicted to be more compositionally homogeneous than those at Moscoviense but are of broadly similar composition to the Moscoviense olivines. Olivines from Aristarchus and Marius exhibit clear spectral differences from those at Moscoviense and Copernicus but also exhibit features that suggest contributions from other phases. If the various precautions discussed here are weighed carefully, the methods presented here can be used to make general predictions of absolute olivine composition (Fe/Mg content). Copyright ?? 2011 by the American Geophysical Union.

  13. Chromium availability in ultramafic soils from New Caledonia. (United States)

    Becquer, T; Quantin, C; Sicot, M; Boudot, J P


    The sources and potential availability of chromium (Cr) on soils formed on ultramafic rocks were investigated with mineralogical studies and selective chemical extractions. Soil solutions were collected in the field (i) along a soil toposequence under natural vegetation with ceramic cups; (ii) under grass in a mandarin trees plantation with tension-free tube lysimeters. On selected soil solutions, the Cr(VI) was determined colorimetrically with the s-diphenylcarbazide method and total Cr by ICP-AES and speciation of Cr(VI) was performed with the MINEQL+ V 4.5 software. The main mineralogical sources of Cr were Cr-substituted goethite and chromite. Up to 90 mg kg(-1) of Cr was extracted by KH(2)PO(4), whereas KCl extractable Cr was very low, indicating that exchangeable Cr was mainly in the highly toxic Cr(VI) form in these soils. Under natural vegetation, the Cr concentrations in the soil solutions remained relatively low (<20 microg l(-1)) due to the high retention of the Cr(VI) anions by Fe-oxides. The Cr concentrations were larger in well aerated colluvial soils, where high levels of Mn-oxides are able to oxidize Cr(III) to Cr(VI), than in piedmont soil where the Mn-oxide content is lower, or in alluvial soils from the lowlands, where waterlogging occurs. Cr concentrations reached 700 microg l(-1) in the field that was fertilized with high amount of phosphorus, due to the exchange of Cr(VI) with phosphate. In such conditions, toxicity phenomena for crops can be expected.

  14. Alcohol synthesis in a high-temperature slurry reactor

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, G.W.; Marquez, M.A.; McCutchen, M.S. [North Carolina State Univ., Raleigh, NC (United States)


    The overall objective of this contract is to develop improved process and catalyst technology for producing higher alcohols from synthesis gas or its derivatives. Recent research has been focused on developing a slurry reactor that can operate at temperatures up to about 400{degrees}C and on evaluating the so-called {open_quotes}high pressure{close_quotes} methanol synthesis catalyst using this reactor. A laboratory stirred autoclave reactor has been developed that is capable of operating at temperatures up to 400{degrees}C and pressures of at least 170 atm. The overhead system on the reactor is designed so that the temperature of the gas leaving the system can be closely controlled. An external liquid-level detector is installed on the gas/liquid separator and a pump is used to return condensed slurry liquid from the separator to the reactor. In order to ensure that gas/liquid mass transfer does not influence the observed reaction rate, it was necessary to feed the synthesis gas below the level of the agitator. The performance of a commercial {open_quotes}high pressure {close_quotes} methanol synthesis catalyst, the so-called {open_quotes}zinc chromite{close_quotes} catalyst, has been characterized over a range of temperature from 275 to 400{degrees}C, a range of pressure from 70 to 170 atm., a range of H{sub 2}/CO ratios from 0.5 to 2.0 and a range of space velocities from 2500 to 10,000 sL/kg.(catalyst),hr. Towards the lower end of the temperature range, methanol was the only significant product.

  15. The crystallization of shoshonitic to peralkaline trachyphonolitic magmas in a H2O-Cl-F-rich environment at Ischia (Italy), with implications for the feeder system of the Campania Plain volcanoes (United States)

    Melluso, L.; Morra, V.; Guarino, V.; de'Gennaro, R.; Franciosi, L.; Grifa, C.


    Bulk-rock and mineralogical characterization of massive samples (lava flows, lava domes, scoria, spatter), chosen to be representative of different activity periods and of the whole known compositional range of Ischia island (Roman Magmatic Province, Campanian district) is reported in this paper. The rocks vary in composition from shoshonites to peralkaline trachyphonolites. Crystallization started with Al-rich chromite inclusions and their host magnesian olivine in shoshonites and latites, and ended with låvenite, rinkite, kochite, hiortdahlite, hainite, Mn-aenigmatite, britholite and Ti-Zr-rich aegirine in the groundmass of the peralkaline trachyphonolites. Removal of feldspar-bearing assemblages (with calcic-to-sodic plagioclase in shoshonites and latites, sodic sanidine and anorthoclase in trachytes and trachyphonolites) is established throughout the compositional range, and is accompanied by interaction between variably evolved magmas (with their differing phenocryst assemblage), mostly in mafic and intermediate compositions. This led to enrichment in Mn, alkalis, Zr, Nb, REE, Rb, Th, U, Cl and F, and depletion in Mg, Fe, V, Ca, Ba, Sr and Eu in the most evolved magmas. The Ischian rocks have a tendency to sodic affinity and by peculiar mineral compositions and compositional trends, which do not indicate extremely oxidizing conditions. The Ischian rocks thus differ from the Phlegrean Fields analogues and the ultrapotassic, more silica undersaturated rocks of Somma-Vesuvius. Overall, variations in the chemical compositions of the rocks and their trends imply unrelated feeding systems and thus are inconsistent with the hypothesis of a common magma reservoir beneath the main volcanic areas of the Campanian Plain.

  16. A technique for monitoring SO2 in combustion exhausts: Use of a non-Nernstian sensing element in combination with an upstream catalytic filter

    Energy Technology Data Exchange (ETDEWEB)

    West, David L [ORNL; Montgomery, Fred C [ORNL; Armstrong, Timothy R. [ORNL


    Detection of sulfur dioxide (SO2) at high temperature (600 750 oC) in the presence of some interferents found in typical combustion exhausts (oxides of nitrogen (NO2 and NO, "NOx"), CO2, CO, and hydrocarbon (C3H6)) is described. The detection scheme involves use of a catalytic filter in front of a non-Nernstian sensing element. The catalytic filter was a Ni:Cr powder bed operating at 850 oC and the sensing elements were pairs of platinum (Pt) and oxide (Ba-promoted copper chromite ((Ba,Cu)xCryOz) and Sr-modified lanthanum ferrite (LSF)) electrodes on yttria-stabilized zirconia. The Ni:Cr powder bed was capable of reducing the sensing element response to NOx, CO, and C3H6, but the presence of NOx (100 ppm by volume) still interfered with the SO2 response of the Pt-(Ba,Cu)xCryOz sensing element at 600 oC, causing approximately a 7 mV (20%) reduction in the response to 120 ppm SO2 and a response equivalent to about 20 ppm SO2 in the in the absence of SO2. The Pt-LSF sensing element, operated at 750 oC, did not suffer from this NOx interference but at the cost of a reduced SO2 response magnitude (120 ppm SO2 yielded ~10 mV, in contrast to ~30 mV for the Pt-(Ba,Cu)xCryOz sensing element). The powder bed and Pt-LSF sensing element were operated continuously over approximately 350 hours, and the response to SO2 drifted downward by about 7%, with most of this change occurring during the initial 100 hours of operation.

  17. Petrology and geochemistry of a peridotite body in Central- Carpathian Paleogene sediments (Sedlice, eastern Slovakia

    Directory of Open Access Journals (Sweden)

    Koppa Matúš


    Full Text Available We studied representative samples from a peridotite body situated NE of Sedlice village within the Central- Carpathian Paleogene sediments in the Central Western Carpathians. The relationship of the peridotite to the surrounding Paleogene sediments is not clear. The fractures of the brecciated peridotite margin are healed with secondary magnesite and calcite. On the basis of the presented bulk-rock and electron microprobe data, the wt. % amounts of mineral phases were calculated. Most of calculated “modal” compositions of this peridotite corresponds to harzburgites composed of olivine (∼70-80 wt. %, orthopyroxene (∼17-24 wt. %, clinopyroxene ( < 5 wt. % and minor spinel ( < 1 wt. %. Harzburgites could originate from lherzolitic protoliths due to a higher degree of partial melting. Rare lherzolites contain porphyroclastic 1-2 mm across orthopyroxene (up to 25 wt. %, clinopyroxene (∼ 5-8 wt. % and minor spinel ( < 0.75 wt. %. On the other hand, rare, olivine-rich dunites with scarce orthopyroxene porphyroclasts are associated with harzburgites. Metamorphic mineral assemblage of low-Al clinopyroxene (3, tremolite, chrysotile, andradite, Cr-spinel to chromite and magnetite, and an increase of fayalite component in part of olivine, indicate low-temperature metamorphic overprint. The Primitive Mantle normalized whole-rock REE patterns suggest a depleted mantle rock-suite. An increase in LREE and a positive Eu anomaly may be consequence of interactive metamorphic fluids during serpentinization. Similar rocks have been reported from the Meliatic Bôrka Nappe overlying the Central Western Carpathians orogenic wedge since the Late Cretaceous, and they could be a potential source of these peridotite blocks in the Paleogene sediments.

  18. Mineralogy and geochemistry of Bobov Dol coals, Bulgaria

    Energy Technology Data Exchange (ETDEWEB)

    Vassilev, S.V.; Yossifova, M.G.; Vassileva, C.G. (Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Applied Mineralogy)


    The mineralogy, elemental composition and modes of occurrence of 49 elements in nine composite samples of Bobov Dol high-ash coals were studied by optical microscopy, scanning and transmission electron microscopy, X-ray diffractometry and chemical analysis. The major minerals were quartz, kaolinite, illite, plagioclase and K-feldspar and the minor minerals and phases were pyrite, marcasite, siderite, calcite, dolomite, gypsum, muscovite, montmorillonite and volcanic glass. The accessory minerals include a wide variety of minerals, such as galena, pyrrhotite, magnetite, hematite, goethite, chromite, rutile, anatase, corundum, gibbsite, biotite, chlorite, zircon, enstatite, garnet, jarosite, alunite, barite, polyhalite, aragonite, ankerite, witherite, apatite, halite and sylvite. The modes of occurrence and some genetic peculiarities of the above-mentioned minerals are described. Thirty-three elements occurred in concentrations higher than the respective Clarke values; especially S, Rb, Nb, Hf, Zn, Cu, Pb, Mn, Ti and U. The concentration trends and modes of occurrence of the trace elements are also discussed. In decreasing order of significance, the trace elements probably occur as element-organic compounds, as impurities in the mineral constituents, as major components in the minerals, as major and impurity components in the inorganic amorphous constituents, and in the fluid constituents. The Bobov Dol coals have undergone complex syngetenic, diagenetic and epigenetic mineralization processes associated with hydrothermal and volcanic activities. These processes were also accompanied by intensive tectonic movements, and possibly, by a later change from continental to marine sedimentation in the area after burial of the coal. 38 refs., 1 fig., 6 tabs., 5 plates.

  19. The effect of bonding environment on iron isotope fractionation between minerals at high temperature (United States)

    Sossi, Paolo A.; O'Neill, Hugh St. C.


    Central to understanding the processes that drive stable isotope fractionation in nature is their quantification under controlled experimental conditions. The polyvalent element iron, given its abundance in terrestrial rocks, exerts controls on the structural and chemical properties of minerals and melts. The iron isotope compositions of typical high temperature minerals are, however, poorly constrained and their dependence on intensive (e.g. fO2) and extensive (e.g. compositional) variables is unknown. In this work, experiments involving a reference phase, 2 M FeCl2·4H2O(l), together with an oxide mix corresponding to the bulk composition of the chosen mineral were performed in a piston cylinder in Ag capsules. The oxide mix crystallised in situ at 1073 K and 1 GPa, in equilibrium with the iron chloride, and was held for 72 h. In order to characterise the effect of co-ordination and oxidation state on the isotope composition independently, exclusively Fe2+ minerals were substituted in: VIII-fold almandine, VI-fold ilmenite, fayalite and IV-fold chromite and hercynite. Δ57FeMin-FeCl2 increases in the order VIII ion. The composition of the VIFe2+-bearing minerals is similar to that of the aqueous FeCl2 fluid. To the degree that this represents the speciation of iron in fluids exsolving from magmas, the fractionation between them should be small, unless the iron is hosted in magnetite. By contrast, predominantly Fe2+-bearing mantle garnets should preserve a much lighter δ57Fe than their lower pressure spinel counterparts, a signature that may be reflected in partial melts from these lithologies. As the Fe-O bond lengths in fayalite and ilmenite are comparable, their isotope compositions overlap, suggesting that high Ti mare basalts acquired their heavy isotopic signature from ilmenite that crystallised late during lunar magma ocean solidification.

  20. Production of pure hydrogen by ethanol dehydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Santacesaria, E.; Carotenuto, G.; Tesser, R.; Di Serio, M. [Naples ' ' Federico II' ' Univ. (Italy). Dept. of Chemistry


    Hydrogen production from bio-ethanol is one of the most promising renewable processes to generate electricity using fuel cells. In this work, we have studied the production of pure hydrogen as by product of ethanol dehydrogenation reaction. This reaction is promoted by copper based catalysts and according to the catalyst used and the operative conditions gives place to acetaldehyde or ethyl acetate as main products. We studied in particular the performance of a commercial copper/copper chromite catalyst, supported on alumina and containing barium chromate as promoter that has given the best results. By operating at low pressure and temperature with short residence times, acetaldehyde is more selectively produced, while, by increasing the pressure (10-30 bars), the temperature (200-260 C) and the residence time (about 100 (grams hour/mol) of ethanol contact time) the selectivity is shifted to the production of ethyl acetate. However, in both cases pure hydrogen is obtained, as by product, that can easily be separated. Hydrogen obtained in this way is exempt of CO and can be directly fed to fuel cells without any inconvenience. In this work, runs performed in different operative conditions have been reported with the scope to individuate the best conditions. A carrier of H{sub 2} 6% in N{sub 2} has been used. The studied catalyst has also shown a good thermal stability with respect to sintering phenomena, that generally occurs during the dehydrogenation on other copper catalysts. Hydrogen productivities of 8-39 mol{sub H2} (gcat){sup -1}(h){sup -1} have been obtained for the explored temperature range 200-260 C. At last, the most accredited reaction mechanism is reported and discussed on the basis of the obtained results. (orig.)

  1. Copper-based sorbents for hot coal gas desulfurization systems

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Slimane, R.B.; Zarnegar, M.K. [Inst. of Gas Technology, Des Plaines, IL (United States)] [and others


    High-temperature coal gas desulfurization has been recognized as essential in the development of emerging power generation technologies such as the Integrated Gasification Combined Cycle (IGCC), aiming to improve both the efficiency and environmental performance of power generation from coal. Hot gas desulfurization may be accomplished by using regenerable mixed metal oxides sorbents which can reduce the H{sub 2}S content of the coal gas to a few ppmv over many sulfidation/regeneration cycles. The focus of much of the current research on hot gas desulfurization has been on the use of zinc-based sorbents. Although these sorbents have been the subject of extensive pilot-scale and process development work, zinc-based sorbents have been shown to suffer from sulfate formation and zinc volatilization, leading to sorbent degradation over multicycle use, increasing sorbent replacement costs and the overall cost of hot gas desulfurization processes. A novel copper-chromite sorbent has been developed at IGT for hot coal gas desulfurization under the sponsorship of the Illinois Clean Coal Institute (ICCI). Results obtained so far indicate that this sorbent, in granular form (i.e., CuCr-29), has a much higher attrition resistance compared to the commercial granular zinc titanate sorbent, as well as excellent desulfurization efficiency. Furthermore, unlike most zinc titanate sorbents, the reactivity of IGT`s CuCr-29 sorbent gradually and consistently improved during the 20 cycles tested. The sorbent preparation techniques developed at IGT have been applied to produce highly reactive and attrition resistant sorbent pellets for moving-bed applications.

  2. Copper-based sorbents for coal gas desulfurization at moderate temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Slimane, R.B.; Abbasian, J.


    In a previous paper, the authors reported on the development of a regenerable copper chromite sorbent, designated as CuCr-29, that is capable of achieving less than 5 ppmv H{sub 2}S concentration in the cleaned fuel gas at about 600 C. This paper reports on recent research carried out to develop a new class of copper-based sorbents for hot fuel gas desulfurization applications in the moderate temperature range of 350--550 C that is currently of industrial interest. A reproducible sorbent preparation technique has been extended to the formulation of highly reactive and attrition-resistant sulfur sorbents based on reagent-grade oxides of copper, manganese, and alumina. The results of packed-bed experiments carried out for the evaluation of the performance of several copper-based sorbents at 350 and 450 C as well as the assessment of the long-term durability and regenerability of one selected formulation are presented and discussed. Three copper-based sorbents were shown to exhibit excellent sulfur removal efficiency and effective capacity, with one formulation (IGTSS-145) being particularly effective in the range of 450--600 C and two formulations (IGTSS-179 and IGTSS-326A) for the range of 350--450 C. The IGTSS-326A formulation maintained excellent sulfur removal efficiency (<1 ppmv H{sub 2}S in the cleaned fuel gas) as well as excellent effective sulfur capacity throughout extended durability testing. This sorbent was also shown to have significantly high attrition resistance, as determined in accordance with the ASTM D5757-95 procedure. These results strongly suggest the suitability of this formulation as a candidate sorbent for demonstration in the Sierra Pacific (Pinon Pine) Clean Coal Technology IGCC Demonstration Program.

  3. Development of regenerable copper-based sorbents for hot gas desulfurization

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Slimane, R.B.; Hill, A.H. [Inst. of Gas Technology, Des Plaines, IL (United States); Honea, F.I. [Illinois Clean Coal Inst., Carbondale, IL (United States)


    The implementation of hot gas cleanup systems heavily depends on the development of regenerable sorbents for removal of sulfur-containing species (mainly H{sub 2}S) from the fuel gas stream at elevated temperatures (i.e., >350 C) from levels of several thousand ppm down to a few ppm, over many sulfidation/regeneration cycles. In addition, these sorbents must have high sulfur capacity, good sulfidation kinetics, good mechanical strength, and good chemical and structural stability over multicycle testing. Zinc-based sorbents, such as zinc titanates, are the leading contenders for hot gas desulfurization. However, these sorbents have been shown to suffer from zinc volatilization at elevated temperatures, resulting in sorbent deterioration and losses through attrition, loss of reactivity, leading to increasing sorbent replacement costs and overall cost of electricity. Copper-based sorbents do not suffer from volatilization problems due to the high melting point of the metal. However, bulk copper oxide is easily reduced to elemental copper in a reducing fuel gas environment, which in turn results in insufficient level of desulfurization. Fortunately, the sorbent desulfurization performance can be greatly enhanced by combining copper oxide with other oxides to minimize or prevent sorbent reduction during the sulfidation stage. This paper reports on research conducted to-date on the development of copper-based sorbents for hot coal gas desulfurization. The results of packed-bed experiments carried out for the determination of optimum operating conditions and for the evaluation of the long-term durability and regenerability of selected copper chromite sorbents are presented and discussed.

  4. Catalytic hydrotreating of biomass liquefaction products to produce hydrocarbon fuels: Interim report

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, D.C.; Baker, E.G.


    Research catalytic hydrotreatment of biomass liquefaction products to a gasoline has been technically demonstrated in a bench-scale continuous processing unit. This report describes the development of the chemistry needed for hydrotreatment of both high pressure and pyrolyzate biomass liquefaction products and outlines the important processing knowledge gained by the research. Catalyst identity is important in hydrotreatment of phenolics. Hydrogenation catalysts such as palladium, copper chromite, cobalt and nickel show activity with nickel being the most active. Major products include benzene, cyclohexane, and cyclohexanone. The hydrotreating catalysts cobalt-molybdenum, nickel-molybdenum and nickel-tungsten exhibit some activity when added to the reactor in the oxide form and show a great specificity for hydrodeoxygenation of phenol without saturation of the benzene product. The sulfide form of these catalysts is much more active than the oxide form and, in the case of the cobalt-molybdenum, much of the specificity for hydrodeoxygenation is retained. Substitution on the phenolic ring has only marginal effects on the hydrotreating reaction. However, the methoxy (OCH/sub 3/) substituent on the phenol ring is thermally unstable relative to other phenolics tested. The pyrolysis products dominate the product distribution when cobalt-molybdenum is used as the hydrotreating catalyst for methoxyphenol. The product from catalytic hydrotreatment of high-pressure biomass liquefaction products confirms the model compounds studies. Catalytic processing at 350 to 400/sup 0/C and 2000 psig with the sulfided cobalt-molybdenum or nickel-molybdenum catalyst produced a gasoline-like product composed of cyclic and aromatic compounds. Oxygen contents in products were in the range of 0 to 0.7 wt % and hydrogen to carbon atomic ratios ranged from 1.5 to 2.0. 46 refs., 10 figs., 21 tabs.

  5. LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Song, Rak-Hyun; Shin, Dong Ryul [Korea Institute of Energy Research, Taejon (Korea, Republic of); Dokiya, Masayuki [National Institute of Materials and Chemical Research, Ibaraki (Japan)


    In the planar SOFC, the interconnect materials plays two roles as an electrical connection and as a gas separation plate in a cell stack. The interconnect materials must be chemically stable in reducing and oxidizing environments, and have high electronic conductivity, high thermal conductivity, matching thermal expansion with an electrolyte, high mechanical strength, good fabricability, and gas tightness. Lanthanum chromite so far has been mainly used as interconnect materials in planar SOFC. However, the ceramic materials are very weak in mechanical strength and have poor machining property as compared with metal. Also the metallic materials have high electronic conductivity and high thermal conductivity. Recently some researchers have studied metallic interconnects such as Al{sub 2}O{sub 3}/Inconel 600 cermet, Ni-20Cr coated with (LaSr)CoO{sub 3}, and Y{sub 2}O{sub 3-} or La{sub 2}O{sub 3}-dispersed Cr alloy. These alloys have still some problems because Ni-based alloys have high thermal expansion, the added Al{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and La{sub 2}O{sub 3} to metals have no electronic conductivity, and the oxide formed on the surface of Cr alloy has high volatility. To solve these problems, in this study, LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC was investigated. The LaCrO{sub 3}-dispersed Cr can be one candidate of metallic interconnect because LaCrO{sub 3} possesses electronic conductivity and Cr metal has relatively low thermal expansion. The content of 25 vol.% LaCrO{sub 3} Was selected on the basis of a theoretically calculated thermal expansion. The thermal expansion, electrical and oxidation properties were examined and the results were discussed as related to SOFC requirements.

  6. Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles (United States)

    Kamran, M.; Ullah, Asmat; Mehmood, Y.; Nadeem, K.; Krenn, H.


    Effect of silica (SiO2) coating concentration on structural and magnetic properties of multiferroic cobalt chromite (CoCr2O4) nanoparticles have been studied. The nanoparticles with average crystallite size in the range 19 to 28 nm were synthesised by sol-gel method. X-ray diffraction (XRD) analysis has verified the composition of single-phase cubic normal spinel structure of CoCr2O4 nanoparticles. The average crystallite size and cell parameter decreased with increasing SiO2 concentration. TEM image revealed that the shape of nanoparticles was non-spherical. Zero field cooled/field cooled (ZFC/FC) curves revealed that nanoparticles underwent a transition from paramagnetic (PM) state to collinear short-range ferrimagnetic (FiM) state, and this PM-FiM transition temperature decreased from 101 to 95 K with increasing SiO2 concentration or decreasing crystallite size. A conical spin state at Ts = 27 K was also observed for all the samples which decreased with decreasing average crystallite size. Low temperature lock-in transition was also observed in these nanoparticles at 12 K for uncoated nanoparticles which slightly shifted towards low temperature with decreasing average crystallite size. Saturation magnetization (Ms) showed decreasing trend with increasing SiO2 concentration, which was due to decrease in average crystallite size of nanoparticles and enhanced surface disorder in smaller nanoparticles. The temperature dependent AC-susceptibility also showed the decrease in the transition temperature (Tc), broadening of the Tc peak and decrease in magnetization with increasing SiO2 concentration or decreasing average crystallite size. In summary, the concentration of SiO2 has significantly affected the structural and magnetic properties of CoCr2O4 nanoparticles.

  7. Investigation of Usability as Industrial Raw Material of Olivine Occurrences: A Case Study from Gelendost - Isparta, Southwestern Turkey (United States)

    Cengiz, Oya; Kurşunluoğlu, Mustafa


    Olivine occurrences are located in the northwest of Madenli and Eğirler villages in Gelendost-Isparta, Southwestern Turkey. The aim of this study is to investigate usability as an industrial raw material of olivine formations in the peridotite. For this purpose, geological, mineralogical and geochemical properties of olivine-rich rocks outcropping in the field were examined. Allochthonous units belonging to Beyşehir-Hoyran Nappes are formed in the Upper Eocene settlement aged Şarkikaraağaç Ophiolites, the Upper Cretaceous Eğirler Formation that contains wild flysch, and the Upper Triassic Deliktaş Formation that consists of recrystallized massive limestone. The Anamas-Akseki Autochthonous units are the Jurassic-Cretaceous Hacıalabaz formation, which consists of dolomite and limestone, the Neogene deposits and the Quaternary alluvium. Harzburgite and dunite are observed in peridotite at the bottom of Şarkikaraağaç Ophiolite. They are dominant rocks of olivine occurrences in the field and include mainly olivine, enstatite, stockwork and vein magnesite, and locally chromite. The concentrations of major oxides for harzburgite samples vary between 41.98 and 44.59% SiO2, between 41.32 to 45.74% MgO, and between 8.75 and 9.82% Fe2O3. The samples ranged from 0.1-4.50% loss on ignition of significance for their usability. Major oxide contents and loss on ignition values of olivine-rich harzburgite samples in the study area partly comply with the standard values that have been determined to be suitable for usage in industry. Consequently, olivine occurrences in the study area are used as olivine sand in industry.

  8. Phase separation and exchange bias effect in Ca doped EuCrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Dongmei, E-mail: [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Wang, Xingyu; Zheng, Jiashun; Qian, Xiaolong [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Yu, Dehong; Sun, Dehui [Bragg Institute, Australian Nuclear Science and Technology Organization, Kirrawee DC, NSW 2232 (Australia); Jing, Chao [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Lu, Bo [Analysis and Measurement Center and Laboratory for Microstructures of Shanghai University, Shanghai 200444 (China); Kang, Baojuan; Cao, Shixun; Zhang, Jincang [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China)


    The rare-earth chromites have attracted increasing interests in recent years, as a member of a few single-phase multiferroic materials. We studied the structure and magnetic property of a series of Ca-doped EuCrO{sub 3} samples by using X-ray powder diffraction and Physical Property Measurement System. Phase separation, rotation of magnetization in M(T) curve and exchange bias effect have been identified. The Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3} polycrystalline sample may be intrinsically phase-separated, with Cr{sup 3+}-rich, Cr{sup 4+}-rich canted antiferromagnetic regions surrounded by spin glass-like frustrated phase, resulting in several magnetic features including: (1) a broad and slow increase of M(T) curve with the decrease of temperature; (2) rotation of magnetization with increasing cooling field; (3) exchange bias and glassy magnetism. The rotation of magnetization is ascribed to the rotation of the moment of Cr{sup 4+}-rich regions, arising from the competition between exchange coupling energy and magnetostatic energy. The exchange bias effect suggests the formation of weak ferromagnetic unidirectional anisotropy during field cooling, due to the exchange coupling among weak ferromagnetic domains and surrounding spin glass-like regions. This result helps understanding the interaction among different magnetic domains and phases in a complex system. - Highlights: • Exchange bias effect and glassy magnetism were observed in Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3}. • Rotation of the moments of Cr{sup 4+}-rich regions result in the rotation of magnetization in M(T) curve. • Spin glass-like regions contribute to the observed exchange bias effect.

  9. Nature and evolution of Neoproterozoic ocean-continent transition: Evidence from the passive margin of the West African craton in NE Mali (United States)

    Renaud, Caby


    The Timétrine massif exposed west of the Pan-African suture zone in northeastern Mali belongs to the passive margin of the West African craton facing to the east intra-oceanic arc assemblages and 730 Ma old pre-collisional calc-alkaline plutons. The Timétrine lithologic succession includes from the base to the top Mesoproterozoic cratonic to passive margin formations overlain by deep-sea Fe-Mg schists. Submarine metabasalts and two ultramafic massifs of serpentinized mantle peridotites are inserted as olistoliths towards the top whereas turbidites of continental origin represent the younger unit. Field and petrological data have revealed a distinct metasedimentary sequence attached to the serpentinized peridotites. It essentially consists of impure carbonates, Fe jaspers and polymictic breccias containing altered blocks of mantle peridotites, most rocks being enriched in detrital chromite. This association is interpreted as reworked chemical and detrital sediments derived from the alteration of mafic-ultramafic rocks. It is argued that mantle exhumation above sea floor took place during the Neoproterozoic rifting and crustal thinning period under possible tropical conditions, as suggested by the large volume of silicified serpentinites. In spite of greenschist facies metamorphic overprint characterized by widespread Fe-rich blue amphiboles that are not diagnostic of high-pressure conditions, it is possible to reconstruct a former ocean-continent transition similar to that evidenced for the Mesozoic period, followed by the deposition of syn-to post rift terrigeneous turbidites roughly coeval with ocean spreading some time before 800 Ma. It is concluded that the serpentinite massifs were tectonically emplaced first in an extensional setting, then incorporated within deep-sea sediments as olistoliths and finally transported westward during late Neoproterozoic collisional tectonics onto the West African craton.

  10. Basin-scale contributions of Cr, Ni and Co from Ortegal Complex to the surrounding coastal environment (SW Europe). (United States)

    Prego, Ricardo; Caetano, Miguel; Ospina-Alvarez, Natalia; Raimundo, Joana; Vale, Carlos


    The enrichment of Cr and Ni in the coastal zones is usually associated with anthropogenic sources such as the tanning, galvanization, ceramic, and cement industries. However, geological complexes of specific lithologic composition located near shorelines may act as natural sources of metals to the continental shelf. Cape Ortegal (SW Europe) is an ultramafic complex that has Cr, Ni and Co enriched in rocks due to the minerals chromite, chromospinel, gersdorfite and pentlandite. Thus, the hypothesis that this geological complex contributes to metal enrichment in Ortigueira and Barqueiro Rias and the adjacent continental shelf was tested. Chromium, Ni, and Co were determined in water and in suspended particulate matter of ria tributaries, rainfall, surface sediments, mussels, and algae. High contents of Cr (max. 1670mg·kg(-1)) and Ni (max. 1360 mg · kg(-1)) were found in the sediments surrounding Cape Ortegal and the Ortigueira Ria as a result of erosion of exposed cliffs. Dissolved Cr and Ni concentrations in fluvial waters were significantly higher in the rivers that crosses the Ortegal Complex, i.e. Lourido (0.47 μg Cr · L(-1); 9.4 μg Ni · L(-1)) and Landoi (0.37 μg Cr · L(-1); 4.3 μg Ni · L(-1)), in comparison with the nearby basin out of the complex influence (Sor River: fluvial contributions of Cr and Ni to the Ortigueira Ria were higher than fluxes into the Barqueiro Ria. Moreover, the increase in Cr and Ni in the rainfall in summer demonstrated the importance of the atmosphere pathway for introducing these elements into the aquatic environment. As a consequence, the contents of these metals in soft tissues and shell of mussels and algae from the Ortigueira Ria were higher than the organisms from Barqueiro Ria. Thus, geological complexes, such as the Cape Ortegal, located in an uncontaminated area, can increase the land-sea exchange of trace metals.

  11. CO2 Energy Reactor - Integrated Mineral Carbonation: Perspectives on Lab-Scale Investigation and Products Valorization

    Directory of Open Access Journals (Sweden)

    Rafael M Santos


    Full Text Available To overcome the challenges of mineral CO2 sequestration, Innovation Concepts B.V. is developing a unique proprietary Gravity Pressure Vessel (GPV reactor technology, and has focussed on generating reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy, thereby reducing energy demand of conventional reactor designs, in addition to offering other benefits. In this paper, a perspective on the status of this technology and outlook for the future is provided. To date, laboratory-scale tests of the envisioned process have been performed in a tubular rocking autoclave reactor. The mineral of choice has been olivine (~Mg1.6Fe2+0.4(SiO4 + ppm Ni/Cr, although asbestos, steel slags and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties have been tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers, solids loading, and mixing rate. The products (carbonates, amorphous silica and chromite have been physically separated (based on size, density and magnetic properties, characterized (for chemistry, mineralogy and morphology and tested in intended applications (as pozzolanic carbon-negative building material. Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable industrial process.

  12. The origin of spheroidal patterns of weathering in the Pados-Tundra mafic-ultramafic complex, Kola Peninsula, Russia

    Directory of Open Access Journals (Sweden)

    A.Y. Barkov


    Full Text Available We document a new and unusual occurrence of patterns of protruding spheroidal weathering developed in a dunitic rock of the Pados-Tundra mafic-ultramafic complex of Early Proterozoic age, Kola Peninsula, Russia. It provides an example similar to that reported recently from a mineralized harzburgite in the Monchepluton layered complex in the same region. These patterns are genetically different from common results of “normal spheroidal weathering” sensu stricto. The spheroidally weathered dunite at Pados-Tundra consists of a high-Fo olivine, Ol (Fo 87. 5, which is, in fact, not altered. Accessory grains of aluminous chromite are present. Relief spheroids (1.5 to 4 cm in diameter; up to ~5 vol. % are distributed sparsely and heterogeneously. They are hosted by the olivine matrix and composed of talc, Tlc, and tremolite, Tr, (Mg# = 95-96 formed presumably at the expense of orthopyroxene, Opx, (i.e., pre-existing oikocrysts during a deuteric (autometasomatic alteration. In contrast, oikocrystic Opx (En 86.0 is quite fresh in related spheroids at Monchepluton, in which only minor deuteric alteration (Tlc + Tr are observed. We infer that (1 the ball-shaped morphology of the weathered surface is a reflection of the presence of oikocrysts of Opx, which crystallized after Ol at the magmatic stage; they were entirely replaced by the deuterically induced Tlc + Tr at Pados-Tundra. (2 Differential rates of weathering are implied for rock-forming minerals in these ultramafic rocks, with a higher resistance of Opx vs. Fo-rich Ol, and Tlc + Tr vs. Fo-rich Ol. (3 The ball-like shape of the large spheroids, produced by magmatic processes, may likely represent an additional factor of their higher stability to weathering in the superficial environment. Similar patterns can be expected in other mafic-ultramafic complexes, especially in layered intrusions.

  13. Production of a microcapsule agent of chromate-reducing Lysinibacillus fusiformis ZC1 and its application in remediation of chromate-spiked soil. (United States)

    Huang, Jun; Li, Jingxin; Wang, Gejiao


    Lysinibacillus fusiformis ZC1 is an efficient Cr(VI)-reducing bacterium that can transform the toxic and soluble chromate [Cr(VI)] form to the less toxic and precipitated chromite form [Cr(III)]. As such, this strain might be applicable for bioremediation of Cr(VI) in soil by reducing its bioavailability. The study objective was to prepare a microcapsule agent of strain ZC1 for bioremediation of Cr(VI)-contaminated soil. Using a single-factor orthogonal array design, the optimal fermentation medium was obtained and consisted of 6 g/L corn flour, 12 g/L soybean flour, 8 g/L NH4Cl and 6 g/L CaCl2. After enlarged fermentation, the cell and spore densities were 5.9 × 10(9) and 1.7 × 10(8) cfu/mL, respectively. The fermentation products were collected and embedded with 1 % gum arabic and 1 % sorbitol as the microcapsule carriers and were subsequently spray-dried. Strain ZC1 exhibited viable cell counts of (3.6 ± 0.44) × 10(10) cfu/g dw after 50-day storage at room temperature. In simulated soil bioremediation experiments, 67 % of Cr(VI) was reduced in 5 days with the inoculation of this microcapsule agent, and the Cr(VI) concentration was below the soil Cr(VI) standard level. The results demonstrated that the microcapsule agent of strain ZC1 is efficient for bioremediation of Cr(VI)-contaminated soil.

  14. Platinum-group elements and minerals in the lower and middle group chromitites of the western Bushveld Complex, South Africa (United States)

    Junge, Malte; Oberthür, Thomas; Osbahr, Inga; Gutter, Paul


    The chromitites of the Bushveld Complex in South Africa contain vast resources of platinum-group elements (PGE). However, knowledge of the distribution and the mineralogical siting of the PGE in the lower group (LG) and middle group (MG) chromitite seams of the Bushveld Complex is limited. We studied concentrates from the LG-6 and MG-2 chromitites of the western Bushveld Complex by a variety of microanalytical techniques. The dominant PGM are sulfides, namely laurite, cooperite-braggite, and malanite-cuprorhodsite, followed by PGE-sulfarsenides, sperrylite, and Pt-Fe alloys. Laurite is the most abundant PGM (vol%). The matching sets of PGM present in the LG and MG chromitites of both the western and the eastern Bushveld Complex, and in the UG-2 chromitite, show strong similarities which support the assumption of a characteristic and general chromitite-related PGM assemblage. Palladium and Rh contents in pentlandite are low and erratic although maximum contents of 7730 ppm Pd and 6020 ppm Rh were detected. Rare thiospinels of the polydymite-linnaeite-greigite series have PGE contents of 1430 ppm Pt, 5370 ppm Rh, and 1460 ppm Pd. The various PGE occur in different deportment: Platinum is generally present in the form of discrete PGM (sulfides, arsenides, alloys). Palladium is present as a large variety of discrete PGM and also incorporated in pentlandite. Rhodium forms discrete PGM and is occasionally present in pentlandite. The IPGE (Os, Ir, and Ru) are dominantly incorporated in laurite (often as inclusions in chromite) and also occur as sulfarsenides.

  15. Mineralogy and Geochemistry of the Pliocene Iron-Rich Laterite in the Vatera Area, Lesvos Island, Greece and Its Genesis

    Institute of Scientific and Technical Information of China (English)



    A nickel laterite deposit occurs in the Vatera area of Lesvos Island, Greece, and is transgressively developed on serpentinized basic rock (norite). The overlying sedimentary rocks include marls and marly limestones with sandstone intercalations and belong to the Pliocene sediments. The following lateritic zones are defined from the bottom to top layers: a) bedrock (norite); b) serpentinized zone; c) goethitic zone. The bedrock consists of the following primary minerals: basic plagioclase, orthopyroxenes and clinopyroxenes. The serpentinized zone includes clinochrysotile, lizardite, antigorite clinoenstatite, calcite and dolomite while in the goethic zone there are goethite, quartz, pyrite, chromite, dolomite. Al2O3, Fe2O3, CaO,Na2O, K2O, Ba, Sr, Ni, C and S are enriched in the goethitic zone. Nickel enrichment is related to the formation of nickeliferons minerals substituting for Mg or/and Fe in the goethite and pyrite. Enrichment of Ni in the matrix may be due to the presence of amorphous Ni-silicates (pimelite). There is a significant change (decrease) in the concentration of Ni from the top to bottom parts of the laterite formation, indicating that there was no tendency to migrate downwards (immature laterite). A second support of the immaturity of the Vatera laterite is the incomplete oxidation of ferrous iron to form ferric iron hydroxides. Under tropical/subtropical conditions, which dominated from the end of Miocene to the Pliocene the norite rocks of the Vatera area altered in response to reaction with acid solutions enriched in CO2. Due to hydrolysis and oxidation of pyroxenes, Mg2 +, H4 SiO4 and Ni2 + were removed in the continental acid solutions.

  16. Mineralogy and Geochemistry of the Pliocene Iron—Rich Laterite in the Vatera Area,Lesvos Island,Greece and Its Genesis

    Institute of Scientific and Technical Information of China (English)



    A nickel laterite deposit occurs in the Vatera area of Lesvos Island,Greece ,and is transgressively developed on serpentinized basic rock (norite).The overlying sedimentary rocks include marls and marly limestones with sandstone intercalations and belong to the Pliocene sed-iments.The following alteritic zones are defined from the bottom to top layers:a)bedrock (norite);b)serpentinized zone;c)goethitic zone.The bedrock consists of the following pri-mary minerals:basic plagioclase,orthopyroxenes and clinopyroxenes.The serpentinized zone includes clinochrysotile,lizardite,antigorite clinoenstatite,calcite and dolomite while in the goethic zone there are goethite,quartz,pyrite,chromite,dolomite.Al2O3 ,Fe2O3,CaO,Na2O,K2O,Ba,Sr,Ni,C and S are enriched in the goethitic zone .Nickel enrichment is re-lated to the formation of nickeliferons minerals substituting for Mg or/and Fe in the goethite and pyrite.Enrichment of Ni in the matrix may be due to the presence of amorphous Ni-sili-cates(pimelite).There is a significant change(decrease)in the concentration of Ni from the top to bottom parts of the laterite formation,indicating that there was no tendency to migrate downwards(immature laterite).A second support of the immaturity of the Vatera laterite is the incomplete oxidation of ferrous iron to form ferric iron hydroxides.Under tropical/subtropical conditions,which dominated from the end of Miocene to the Pliocene the norite rocks of the Vatera area altered in response to reaction with acid solutions enriched in CO2.Due to hydrolysis and oxidation of pyroxenes,Mg2+,H4SiO4 and Ni2+ were removed in the continental acid solutions.

  17. Mapping of groundwater potential zones in Salem Chalk Hills, Tamil Nadu, India, using remote sensing and GIS techniques. (United States)

    Thilagavathi, N; Subramani, T; Suresh, M; Karunanidhi, D


    This study proposes to introduce the remote sensing and geographic information system (GIS) techniques in mapping the groundwater potential zones. Remote sensing and GIS techniques have been used to map the groundwater potential zones in Salem Chalk Hills, Tamil Nadu, India. Charnockites and fissile hornblende biotite gneiss are the major rock types in this region. Dunites and peridodites are the ultramafic rocks which cut across the foliation planes of the gneisses and are highly weathered. It comprises magnesite and chromite deposits which are excavated by five mining companies by adopting bench mining. The thickness of weathered and fracture zone varies from 2.2 to 50 m in gneissic formation and 5.8 to 55 m in charnockite. At the contacts of gneiss and charnockite, the thickness ranges from 9.0 to 90.8 m favoring good groundwater potential. The mine lease area is underlined by fractured and sheared hornblende biotite gneiss where groundwater potential is good. Water catchment tanks in this area of 5 km radius are small to moderate in size and are only seasonal. They remain dry during summer seasons. As perennial water resources are remote, the domestic and agricultural activities in this region depend mainly upon the groundwater resources. The mines are located in gently slope area, and accumulation of water is not observed except in mine pits even during the monsoon period. Therefore, it is essential to map the groundwater potential zones for proper management of the aquifer system. Satellite imageries were also used to extract lineaments, hydrogeomorphic landforms, drainage patterns, and land use, which are the major controlling factors for the occurrence of groundwater. Various thematic layers pertaining to groundwater existence such as geology, geomorphology, land use/land cover, lineament, lineament density, drainage, drainage density, slope, and soil were generated using GIS tools. By integrating all the above thematic layers based on the ranks and

  18. Cooling History and Redox State of NWA 8694 Chassignite: Comparison with Chassigny and NWA 2737 (United States)

    Mikouchi, T.; Takenouchi, A.; Zolensky, M. E.


    NWA 8694 is a new chassignite whose constituent minerals are more Fe-rich than those in the other known chassignites (Chassigny and NWA 2737), and may suggest a petrogenetic relationship to nakhlites. In this abstract we report mineralogy of NWA 8694 to infer its cooling rate and redox state, and discuss its thermal and shock history in comparison with other chassignites. NWA 8694 is a cumulate dunite of approximately 2 mm olivine with interstitial pyroxene and feldspar. Olivine is homogeneous (Fo(sub 55-56)), but Ca decreases at the approximately 50-100 micrometer rim (0.25-0.1 wt% CaO). Because the Ca-depleted rim is narrower than those in other chassignites (approximately 50 ?micrometer), NWA 8694 may have cooled slightly faster than the others (approximately 30 C/yr), but would be in the same order. Pyroxenes are low- and high-Ca pyroxenes, both exhibiting sub-micron exsolution textures (0.2-0.3 micrometer wide lamellae with the spacing of 0.8-1.8 micrometers). Although the low-Ca pyroxene host has an orthopyroxene composition (Wo approximately 2), the EBSD analysis suggests a pigeonite structure (P2(sub 1)/c), which is also reported from the Chassigny pyroxene. The size of exsolution texture is a bit smaller, but broadly similar to those in other chassignites, implying a similar fast cooling rate (35-43 C/yr). Feldspars are isotropic (plagioclase: clustered around An25Or10, K-feldspar: approximately An19Or78), suggestive of extensive shock metamorphism, consistent with undulatory extinction of olivine. Feldspar compositions are around the equilibrium isotherm of approximately 800 C. The olivine and chromite compositions give an equilibration temperature of 760-810 C and logfO2 of QFM+/-0.3. The inferred fast cooling rate and high fO2 of NWA 8694 are both similar to those of Chassigny and NWA 2737, and suggest a common formation condition (e.g., thick lava flow or shallow intrusion) under oxidizing condition. The Fe-rich mineral compositions of NWA 8694 may be

  19. 一个新陨落的L6-5型球粒陨石——广饶陨石

    Institute of Scientific and Technical Information of China (English)

    侯渭; 王道德


    The Guangrao meteorite,weighing 1.9kg,fell on June 21,1980 near Gnaugrao County,Shandong Provinee(37.1°N,118.4°E).Mineralogical and chemical compositions of the meteorite from Guangrao County were determined,indicating an olivine-hypersthene chondrite with perfect recrystallization structure.It is composed mainly of olivine(Fa24)and orthopyroxene(Fs 10),and minor amounts of plagioclase,kamacite,taenite,troilite,chromite,and a negligible amount of native copper.Textural features of the Guangrao meteorite show that there are only a few chondrules with distinct outlines,as identified in thin sections.Examined in polarized cross light,it was found that the meteorite is of high petrographic type,belonging to type 6-5 chondrites of Van Schmus and Wood(1967).The preliminary results of wet chemical analysis are given as follows:SiO2 39.81,MgO 25.09,FeO 15.78,Al2O3 2.08,CaO 1.93,Na2O 1.00,K2O 0.13,Cr2O3 0.52,MnO 0.27,TiO2 0.13,P2O5 0.26,Cu0.012,Fe 6.3,Ni1.55,Co0.055,FeS5.91,H2O- 0.033,H2O+ 0.016,total Fe22.38(%);the ratios of SiO2/MgO 1.59,Fe0/Fe 0.28,Fe/Si 0.61.Si/Mg 1.06;Fe(mole %)24.In accordance with the bulk chemical composition,the Guangrao meteorite belongs to L-group chondrites,A preliminary hypothesis for L6-5 chondrite is suggested on the basis of the homogeneity and composition of silicate minerals and the apparent lack of chondrules with distinet outlines and reerytallized matrix.

  20. Petrogenesis and tectonic setting of the Bondla mafic-ultramafic complex, western India: Inferences from chromian spinel chemistry (United States)

    Ishwar-Kumar, C.; Rajesh, V. J.; Windley, B. F.; Razakamanana, T.; Itaya, T.; Babu, E. V. S. S. K.; Sajeev, K.


    Crustal-scale shear/suture zones hold prime importance because they are one of the critical parameters used for paleogeographic configurations of supercontinental assemblies. The Kumta suture, located on the western margin of peninsular India, has been interpreted as the eastern extension of the Betsimisaraka suture zone of Madagascar. This suture separates the Karwar block (ca. 3200 Ma tonalite-trondhjemite-granodiorite (TTG) and amphibolite) in the west from a quartzite-dominated shelf that overlies ca. 2571 Ma quartzo-feldspathic gneisses of the Dharwar block in the east. The NW/SE-trending Bondla ultramafic-mafic complex, situated in the arc just west of the Kumta suture, comprises gabbro, troctolite, wehrlite, dunite, peridotite, pyroxenite, chromitite and chromian spinel-bearing serpentinite. In this paper, we study the chemistry of Cr-spinels in chromitites and serpentinites to help understand their paleo-tectonic environments. The Cr-spinel in Bondla chromitites and serpentinites shows variations in Cr# [Cr/(Cr + Al)] ranging from 0.54 to 0.58 and 0.56 to 0.64 respectively; also, the Mg# [Mg/(Mg + Fe)] varies from 0.56 to 0.67 and 0.41 to 0.63 respectively. The Cr-spinels in serpentinites have strong chemical zoning with distinctive ferrian chromite rims (Mg# 0.41-0.63), whereas the Cr-spinels in chromitites are generally homogeneous with only occasional weak zoning. The spinel-core crystallization temperature in the serpentinite is estimated to be above 600 °C (the spinel stability field was calculated for equilibrium with Fo90 olivine), which suggests the core composition is chemically unaltered. The Cr-spinels in all studied samples have low-Al2O3 (15-23 wt%) and moderate to high-Cr# (0.54-0.69), suggesting derivation from a supra-subduction zone arc setting. The chemistry of clinopyroxene in serpentinite indicates a wide range of crystallization temperatures from 969 °C to 1241 °C at 1.0 GPa. The calculated parental magma composition was similar to

  1. Origin of Peculiar Horizons from the Nuvvuagittuq Greenstone Belt: Testing the Conglomerate Hypothesis (United States)

    Kitayama, C.; Thomassot, E.; Wing, B. A.


    matrix. Preliminary results suggest that the matrix hosts many zircon, monazite and xenotime neoblasts as well as a variety of sulfide minerals, while most of the trace minerals in the dominant type of potential clasts are euhedral sulfides, with rare chromite-rich regions. Trace zircon and monazite are more common in the subordinate type of potential clasts, with zircon occasionally exhibiting that show a concentric but truncated zonation. And finally, we are also measuring sulfur isotope compositions of sulfides from the potential clasts and from the matrix. The key principle linking these two consistency tests is the presence or absence of mineralogical, mineral chemical, and isotopic heterogeneity.

  2. Melt Segregation & LPO in Anorthite-Basalt Deformed in Torsion (United States)

    Zimmerman, M. E.; Kohlstedt, D. L.


    Deformation in the middle and lower crust is in large part controlled by the rheology of feldspar. Seismic studies have shown that the middle crust of orogenic belts is partially molten. Structural studies of mylonites and migmatites from these terrains record large strain deformation. Therefore, we performed torsional shear deformation experiments on fine grained (10 μ m) samples of Beaver Bay anorthite (An70) +/- 10 vol% basalt to shear strains γ = 2-6 to investigate the development of lattice preferred orientation (LPO) and melt segregation at large shear strains. We performed experiments in a gas medium apparatus equipped with an internal torque cell at T = 1450 K, P = 300 MPa, and constant twist rate. Melt segregated in the An70 + basalt samples into melt-rich bands oriented at ˜20° to the shear plane and antithetic to the shear direction. The spacing between bands is ˜0.5 mm. Distortion of the iron jacket demonstrates that strain localized in the melt-rich bands. We determined the LPO of An70 with scanning electron microscopy using electron back scatter diffraction (SEM-EBSD). In patterns from an An70+ basalt sample deformed to γ ≈ 2.5, (001) planes are aligned subparallel to the shear plane and [100] axes are concentrated close to the shear direction. Both the (001) and the [100] are rotated counter clockwise from the shear direction by 20-25° . The formation of melt-rich bands is consistent with results from simple shear experiments on olivine + chromite + basalt and olivine + FeS +/- basalt, as well as An70 + basalt and indicates that deformation can drive melt segregation. Deformation drives the self organization of melt-rich bands and decreases the effective viscosity of the rock. The LPO is consistent with results from experiments on albite in shear and anorthite in compression and compatible with slip dominantly on (001) with [100] as the slip direction. A similar back rotation, attributed to partitioning of the strain between melt-rich and

  3. Combined Whole-Rock to Nano-Scale Investigations Reveal Contrasting Response of Pt-Os and Re-Os Isotope Systematics During Magmatic and Post-Magmatic Processes (United States)

    Coggon, J. A.; Luguet, A.; Lorand, J. P.; Fonseca, R.; Wainwright, A.; Appel, P.; Hoffmann, J. E.; Nowell, G. M.


    Advances in single-grain and micro- and nano-analytical techniques in recent years have been particularly important to the study of highly siderophile elements (HSE) and have contributed significantly to our knowledge and understanding of their host phases and behaviour. Furthermore, whole-rock- to nano-scale studies provide new perspectives for investigation of HSE isotope systematics. Recent multi-scale 187Re-187Os and 190Pt-186Os studies facilitate comparison, to a previously unattainable degree, of the differing responses of these two decay systems to magmatic and post-magmatic processes. It is well established that mafic-ultramafic melts are sensitive to disturbance of their Re-Os isotope systematics by crustal assimilation, due to the incompatibility and resulting enrichment of Re in crustal lithologies. In contrast the very long half-life and extremely low atomic abundance of 190Pt, combined with relatively low Pt concentrations in crustal rocks, generally render the Pt-Os isotope system insensitive to modification during assimilation. However, using new single chromite grain data (Coggon et al., 2015) from the >3.811 Ga Ujaragssuit nunât layered ultramafic body, Greenland, we show that it is possible to distinguish two distinct episodes of 187Os/188Os modification; Country rock contamination of the parent melt was followed by later metamorphic disturbance of the isotope system. The Pt-Os data (Coggon et al., 2013) from the same samples show no evidence of crustal assimilation, but preserve signatures of mantle melting at ~4.1 Ga as well as disturbance during metamorphism. Macro- to micro-petrographic study clearly demonstrates that Pt, Re and Os are hosted by different mineral phases, of different origins, in these samples. This, together with the physical parameters of the decay systems reported above, leads to the dissimilar behaviour and response of the 187Re-187Os and 190Pt-186Os isotope systems during both magmatic and post-magmatic processes and

  4. Regional tectonics, geology, magma chamber processes and mineralisation of the Jinchuan nickel-copper-PGE deposit, Gansu Province, China:A review

    Institute of Scientific and Technical Information of China (English)

    T.M. Mike Porter


    The Jinchuan Ni-Cu-PGE deposit (>500 Mt@1.2%Ni, 0.7%Cu, w0.4 g/t PGE), one of the largest magmatic sulphide deposits in the world, is located within the westernmost terrane of the North China Craton. It is hosted within the 6.5 km long, Neoproterozoic (w0.83 Ga) Jinchuan ultramafic intrusion, emplaced as a sill-like body into a Palaeoproterozoic suite of gneisses, migmatites, marbles and amphibolites, below an active intracratonic rift. The parental magma was high-Mg basalt, generated through melting of sub-crustal lithospheric mantle by a mantle plume during the initiation of Rodinia supercontinent breakup. The lower Palaeozoic collision of the exotic Qilian Block with the breakup-related southern margin of the craton accreted a subduction complex, and emplaced voluminous granitic intrusions and foreland basin sequences within the craton, to as far north as Jinchuan. During the Cainozoic, allochthonous lower Palaeozoic rocks were thrust up to 300 km to the northeast over cratonic basement, to within 25 km of the Jinchuan deposit. The Jinchuan ultramafic intrusion was injected into three interconnected sub-chambers, each containing a separate orebody. It essentially comprises an olivine-orthopyroxene-chromite cumulate, with interstitial orthopyroxene, clinopyroxene, plagioclase and phlogopite, and is predominantly composed of lherzolite (w80%), with an outer rim of olivine pyroxenite and cores of mineralised dunite. Mineralisation occurs as disseminated and net-textured sulphides, predominantly within the dunite, with lesser, PGE rich lenses, late massive sulphide accumulations, small copper rich pods and limited mineralised diopside skarn in wall rock marbles. The principal ore minerals are pyrrhotite (the dominant sulphide), pentlandite, chalcopyrite, cubanite, mackinawite and pyrite, with a variety of platinum group minerals and minor gold. The deposit underwent significant post-magmatic tremolite-actinolite, chlorite, serpentine and magnetite alteration. The

  5. Thermobarometry of mantle-derived garnets and pyroxenes of Kola region (NW Russia: lithosphere composition, thermal regime and diamond prospectivity

    Directory of Open Access Journals (Sweden)

    Dmitry R. Zozulya


    Full Text Available More than 700 pyrope, chrome diopside and chromite grains recovered from Quaternary sediments of the Kola craton, and from the Ermakovsky kimberlite in the Terskii Coast field were analyzed in order to determine their P-T parameters. Ni-thermometry on pyropes from SE Kola gives a range of temperatures between 650–1250 °C, corresponding to a sampling interval of c. 75–190 km. Pyrope compositions imply a stratified structure to the SE Kola lithospheric mantle, with G10-pyropes absent in the shallow mantle (75–110 km where the bulk of the G9-pyropes are sourced, while a deeper mantle horizon, between110 and 190 km, has contributed abundant G10-pyropes. Approximately 16 % of all these pyropes are derived from the diamond stability field. The Ni-temperatures of garnets from the Ermakovsky kimberlite reveal a relatively shallow sampling interval of the mantle (c.75–140 km, dominantly within the graphite-stability field. P-T values for peridotitic chrome diopsides imply that most grains from SE Kola were derived from the graphite stability field, apparently originating from non-diamondiferous alkaline-ultramafic dykes. Nevertheless, c. 15 % of SE Kola diopsides have been derived from the stability field of diamond. Diopsides from SW Kola mostly plot in the diamond stability field. 20 % of diopsides from central Kolaare derived from the diamond stability field, whereas diopsides from northern Kola region all fall within the stability field of graphite. The maximum depth of diopside xenocryst sampling varies from up to 200 km in SE and SW Kola, to 170 km in central Kola, and only to 140 km in the northern Kola region. The P-T values for chrome diopsides imply significant regional differences in heat flow: 38–44 mW/m^2 within the southern part of Kola adjacent to the Kandalaksha graben; 35–38 mW/m^2 towards the SE and SW away from the graben; 38–44 mW/m^2 in central Kola; and up to 50 mW/m^2 in northernmost Kola. These data indicate that

  6. FE-SEM/EDS and μ-IR combined analysis of HED meteorites in relation to infrared spectra of Vesta-like asteroids (United States)

    Ferrari, Marco; Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Rotundi, Alessandra


    Knowing the chemico-mineralogical composition of an extraterrestrial body is key to understanding its geological evolution. For this reason, remote-sensing instruments that can gather compositional data by using infrared spectroscopy are often part of the spacecraft missions. In order to acquire a fuller grasp of these data it is fundamental to compare them to analogue samples analysed by means of spectroscopy techniques.This study is focused on the Howardite-Eucrite-Diogenite meteorites (HEDs) [1] originated from the differentiated asteroid 4 Vesta [2]; this hypothesis was lately reinforced by the data provided by the Dawn mission [3].These meteorites consist of pyroxene basalts either brecciated or not (eucrites), brecciated orthopyroxenites (diogenites) and polymictic breccias of diogenites and eucrites originated by impacts on their parent body's surface (howardites).Here we report a FE-SEM/EDS and μ-IR spectroscopy combined study of three HED meteorite samples: 1) NWA 7159, a monomictic brecciated eucrite consisting of exolved orthopyroxene (Fs56.6-57.1 Wo2.0-1.9) and anorthite with accessory silica polymorph and ilmenite; 2) NWA 7490 a diogenite with a cumulate texture dominated by orthopyroxene (Fs24.1-26 Wo3.4-4.6), with Ca-plagioclase, minor olivine and chromite and troilite as accessory minerals; 3) NWA 2698, an howardite with eucritic pyroxene (Fs45-40 Wo7-20).The FE-SEM backscattered images coupled with the EDS maps gives information on the morphology (e.g. grain size and texture) and chemistry of the three samples. The μ-IR spectrometer provides reflectance spectra of the selected features of interest and spectral maps of larger areas. With the combined analyses we obtained a comprehensive mineralogical framework for the three HED samples. It was proven that the mineralogical heterogeneity of the HED meteorites is consistent with the spectroscopic diversity seen on Vesta [4], thus this study helps in better constraining and characterising the

  7. Extremely depleted lithospheric mantle and diamonds beneath the southern Zimbabwe Craton (United States)

    Smith, Chris B.; Pearson, D. Graham; Bulanova, Galina P.; Beard, Andrew D.; Carlson, Richard W.; Wittig, Nadine; Sims, Keith; Chimuka, Lovemore; Muchemwa, Ellah


    Inclusion-bearing diamonds, mantle xenoliths, and kimberlite concentrates from the Cambrian-aged Murowa and Sese kimberlites have been studied to characterise the nature of the lithospheric mantle beneath the southern Zimbabwe Craton. The diamonds are mostly octahedral, moderately rich in nitrogen with moderate to high aggregation, and contain mainly dunite-harzburgite mineral inclusions. Similarly, dunite xenoliths predominate over harzburgite and lherzolite and carry olivines with Mg/Mg + Fe (Mg#) values of 0.92-0.95, spanning the average signatures for Kaapvaal Craton peridotites. Eclogitic xenoliths are extremely rare, in contrast to the Kaapvaal mantle lithosphere. The Zimbabwe mantle assemblage has been only slightly affected by later silicic metasomatism and re-fertilisation with re-introduction of pyroxenes in contrast to the Kaapvaal and many cratonic lithospheric blocks elsewhere where strong metasomatism and re-fertilisation is widespread. Pyroxene, garnet and spinel thermobarometry suggests an ambient 40 mW m - 2 geotherm, with the lithosphere extending down to 210 km at the time of kimberlite eruption. Whole rock peridotite Re-Os isotope analyses yield T RD model ages of 2.7 to 2.9 Ga, providing minimum estimates of the time of melt depletion, are slightly younger in age than the basement greenstone formation. These model ages coincide with the mean T RD age of > 200 analyses of Kaapvaal Craton peridotites, whereas the average Re-Os model age for the Zimbabwe peridotites is 3.2 Ga. The Os data and low Yb n/Lu n ratios suggest a model whereby thick lithospheric mantle was stabilised during the early stages of crustal development by shallow peridotite melting required for formation of residues with sufficiently high Cr/Al to stabilise chromite which then transforms to low Ca, high Cr garnet. Sulphide inclusions in diamond produce minimum T RD model ages of 3.4 Ga indicating that parts of the lithosphere were present at the earliest stages of crust

  8. Syngenetic inclusions of yimengite in diamond from Sese kimberlite (Zimbabwe) — evidence for metasomatic conditions of growth (United States)

    Bulanova, G. P.; Muchemwa, E.; Pearson, D. G.; Griffin, B. J.; Kelley, S. P.; Klemme, S.; Smith, C. B.


    Syngenetic inclusions of yimengite K (Cr, Ti, Mg, Fe, Al) 12O 19, a potassium member of the magnetoplumbite mineral group, have been recorded in an octahedral macrodiamond from the Sese kimberlite (50 km south of Masvingo, Zimbabwe). One yimengite inclusion carries lamellae of chromite suggesting peridotitic diamond paragenesis. The diamond and inclusions were studied in situ in a plate polished parallel to (011). Cathodoluminescence (CL) imaging has shown blue colour and octahedral zonation of the diamond, lack of cracks and the location of five yimengites in different growth zones. Nitrogen (N) contents (at. ppm) in the diamond determined by Fourier transform infrared spectroscopy (FTIR) steadily decrease from 576 (core) to 146 (rim). N aggregation (%1aB) is correspondingly 40% in the core and 30% in the rim. Hydrogen (H) content is high in the core, moderate in the intermediate and very high in the rim zones. Four yimengites were dated using the laser 40Ar/ 39Ar method. Three inclusions yielded total gas ages that agree with, or are younger than, or within error of, the Sese kimberlite eruption age (538±11 Ma) but may be compromised by gas loss. One inclusion, with the highest tapped interface gas yield, gave a total gas age of 892±21 Ma that is a likely minimum yimengite age. Time-T °C constraints from N aggregation systematics give a range of possible ages from kimberlite eruption date back to Archean and do not resolve the variable results of the 40Ar/ 39Ar dating. Compared with the published chemistry of yimengite from kimberlites, inclusions from the Sese diamond contain higher Al, Mg, and Sr and have lower concentration of Fe 3+. The chondrite-normalised REE pattern of the yimengite shows enrichment in LREE and depletion in HREE, but LREE/HREE fractionations are lower than for lindsleyite-mathiasite series mantle titanates and rather similar to the REE concentrations in kimberlite and lamproite rocks. It is suggested that Sese yimengite formed in the

  9. Model parameter estimations from residual gravity anomalies due to simple-shaped sources using Differential Evolution Algorithm (United States)

    Ekinci, Yunus Levent; Balkaya, Çağlayan; Göktürkler, Gökhan; Turan, Seçil


    An efficient approach to estimate model parameters from residual gravity data based on differential evolution (DE), a stochastic vector-based metaheuristic algorithm, has been presented. We have showed the applicability and effectiveness of this algorithm on both synthetic and field anomalies. According to our knowledge, this is a first attempt of applying DE for the parameter estimations of residual gravity anomalies due to isolated causative sources embedded in the subsurface. The model parameters dealt with here are the amplitude coefficient (A), the depth and exact origin of causative source (zo and xo, respectively) and the shape factors (q and ƞ). The error energy maps generated for some parameter pairs have successfully revealed the nature of the parameter estimation problem under consideration. Noise-free and noisy synthetic single gravity anomalies have been evaluated with success via DE/best/1/bin, which is a widely used strategy in DE. Additionally some complicated gravity anomalies caused by multiple source bodies have been considered, and the results obtained have showed the efficiency of the algorithm. Then using the strategy applied in synthetic examples some field anomalies observed for various mineral explorations such as a chromite deposit (Camaguey district, Cuba), a manganese deposit (Nagpur, India) and a base metal sulphide deposit (Quebec, Canada) have been considered to estimate the model parameters of the ore bodies. Applications have exhibited that the obtained results such as the depths and shapes of the ore bodies are quite consistent with those published in the literature. Uncertainty in the solutions obtained from DE algorithm has been also investigated by Metropolis-Hastings (M-H) sampling algorithm based on simulated annealing without cooling schedule. Based on the resulting histogram reconstructions of both synthetic and field data examples the algorithm has provided reliable parameter estimations being within the sampling limits of

  10. International Field School on Permafrost, Polar Urals, 2012 (United States)

    Streletskiy, D. A.; Grebenets, V.; Ivanov, M.; Sheinkman, V.; Shiklomanov, N. I.; Shmelev, D.


    The international field school on permafrost was held in the Polar Urals region from June, 30 to July 9, 2012 right after the Tenth International Conference on Permafrost which was held in Salekhard, Russia. The travel and accommodation support generously provided by government of Yamal-Nenets Autonomous Region allowed participation of 150 permafrost young research scientists, out of which 35 students from seven countries participated in the field school. The field school was organized under umbrella of International Permafrost Association and Permafrost Young Research Network. The students represented diverse educational backgrounds including hydrologists, engineers, geologists, soil scientists, geocryologists, glaciologists and geomorphologists. The base school camp was located near the Harp settlement in the vicinity of Polar Urals foothills. This unique location presented an opportunity to study a diversity of cryogenic processes and permafrost conditions characteristic for mountain and plain regions as well as transition between glacial and periglacial environments. A series of excursions was organized according to the following topics: structural geology of the Polar Urals and West Siberian Plain (Chromite mine "Centralnaya" and Core Storage in Labitnangy city); quaternary geomorphology (investigation of moraine complexes and glacial conditions of Ronamantikov and Topographov glaciers); principles of construction and maintains of structures built on permafrost (Labitnangy city and Obskaya-Bovanenkovo Railroad); methods of temperature and active-layer monitoring in tundra and forest-tundra; cryosols and soil formation in diverse landscape condition; periglacial geomorphology; types of ground ice, etc. Every evening students and professors gave a series of presentations on climate, vegetation, hydrology, soil conditions, permafrost and cryogenic processes of the region as well as on history, economic development, endogenous population of the Siberia and the

  11. Spectroscopic analysis of chromium bioremediation products (United States)

    Varadharajan, C.; Nico, P. S.; Yang, L.; Marcus, M. A.; Steefel, C.; Larsen, J. T.; Beller, H. R.; Brodie, E. L.


    Remediation of chromium contamination frequently involves reducing the toxic and soluble hexavalent form, Cr(VI), to the relatively harmless and mostly immobile trivalent state, Cr(III). The objective of this study is to identify the biogeochemical reactions that control in situ chromium reduction in the presence of different dominant electron acceptors, i.e., NO3-, Fe(III), and SO42-. It was hypothesized that indirect, abiotic reduction of Cr(VI) by reduced metabolic products [Fe(II) and sulfides] would dominate over direct enzymatic reduction by denitrifying, iron-reducing, or sulfate-reducing bacteria. It is further hypothesized that the enzymatic reduction of Cr(VI) would produce relatively pure chromium hydroxide precipitates, whereas indirect reduction would result in mixed Cr-Fe hydroxide solid phases. Flow-through columns containing homogenized sediments from the 100H site at Hanford, WA were subjected to nitrate-, sulfate- or iron-reducing conditions in the presence of 5 µM Cr(VI) and 5 mM lactate. Cr(VI) was depleted in the effluent solutions from the nitrate- and sulfate-reducing columns; however only a small amount of Cr(VI) was removed under iron-reducing conditions. Preliminary analysis of micro X-ray absorption spectra indicate that the untreated and iron-reducing column sediments contained pre-existing Cr in the form of primary minerals, e.g. chromite and/or Cr-bearing micas. However, there was an increase in the relative abundance of mixed-phase Cr-Fe hydroxides, i.e., Cr1-xFex(OH)3 in the nitrate- and sulfate-treated columns. A possible explanation for the observations is that the production of Fe(II) was enhanced under the nitrate- and sulfate- reducing conditions, and was most likely sulfide-driven in the latter case. The Fe(II) was subsequently available for reduction of Cr(VI) resulting in the mixed-phase precipitates. The results from the spectroscopic analysis support the hypothesis that Fe(II)-mediated Cr reduction prevails over direct

  12. Immiscible silicate liquids and phosphoran olivine in Netschaëvo IIE silicate: Analogue for planetesimal core-mantle boundaries (United States)

    Van Roosbroek, Nadia; Hamann, Christopher; McKibbin, Seann; Greshake, Ansgar; Wirth, Richard; Pittarello, Lidia; Hecht, Lutz; Claeys, Philippe; Debaille, Vinciane


    We have investigated a piece of the Netschaëvo IIE iron meteorite containing a silicate inclusion by means of electron microprobe analysis (EMPA) and transmission electron microscopy (TEM). Netschaëvo contains chondrule-bearing clasts and impact melt rock clasts were also recently found. The examined inclusion belongs to the latter and is characterized by a porphyritic texture dominated by clusters of coarse-grained olivine and pyroxene, set in a fine-grained groundmass that consists of new crystals of olivine and a hyaline matrix. This matrix material has a quasi-basaltic composition in the inner part of the inclusion, whereas the edge of the inclusion has a lower SiO2 concentration and is enriched in MgO, P2O5, CaO, and FeO. Close to the metal host, the inclusion also contains euhedral Mg-chromite crystals and small (olivine crystallites containing up to 14 wt% P2O5, amorphous material, and interstitial Cl-apatite crystals. The Si-rich silicate glass globules show a second population of Fe-rich silicate glass droplets, indicating they formed by silicate liquid immiscibility. Together with the presence of phosphoran olivine and quenched Cl-apatite, these textures suggest rapid cooling and quenching as a consequence of an impact event. Moreover, the enrichment of phosphorus in the silicate inclusion close to the metal host (phosphoran olivine and Cl-apatite) indicates that phosphorus re-partitioned from the metal into the silicate phase upon cooling. This probably also took place in pallasite meteorites that contain late-crystallizing phases rich in phosphorus. Accordingly, our findings suggest that oxidation of phosphorus might be a general process in core-mantle environments, bearing on our understanding of planetesimal evolution. Thus, the Netschaëvo sample serves as a natural planetesimal core-mantle boundary experiment and based on our temperature estimates, the following sequence of events takes place: (i) precipitation of olivine (1400-1360 °C), (ii) re

  13. Pd-Ag chronology of volatile depletion, crystallization and shock in the Muonionalusta IVA iron meteorite and implications for its parent body (United States)

    Horan, M. F.; Carlson, R. W.; Blichert-Toft, J.


    Muonionalusta, a Group IVA iron meteorite, was analyzed for its 107Pd-107Ag isotope systematics by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in order to better constrain the initial Solar System abundance of 107Pd and to provide high resolution chronology of the evolution of its parent body. Six metal samples from Muonionalusta yield Ag abundances between 0.1012 and 1.461 ng/g, 107Ag/109Ag between 1.131 and 1.805, with 108Pd/109Ag ratios of 2201 to 52,300. The metal Pd/Ag and Ag isotopic data are correlated with a slope corresponding to a 107Pd/108Pd of (2.15±0.30)×10-5. If the Pd-Ag and Pb-Pb isotope systems closed at the same time in Muonionalusta, i.e., 2-3 Ma after CAI formation, then an initial Solar System ratio of 107Pd/108Pd=(2.8±0.5)×10-5 can be inferred. One troilite sample contains 8.478 ng/g Ag and has a 107Ag/109Ag ratio of 1.0833; its Pd concentration is 205.2 ng/g corresponding to a low 108Pd/109Ag of 13.56. The Pd-Ag results for this troilite plot near the extrapolation of the line passing through the metal points and define an initial 107Ag/109Ag that is substantially higher than chondritic, indicating that Muonionalusta formed from a precursor with high Pd/Ag. Pd and Ag concentrations in Muonionalusta metal suggest fractional crystallization from a source having Pd/Ag>4500, but the initial Ag isotopic composition for Muonionalusta troilite limits the duration of the high Pd/Ag to an interval of ≤0.6 Ma before cooling to closure of the Pd-Ag system. This result suggests that depletion of Ag and other volatile elements occurred shortly before accretion and cooling of the IVA parent body, and may have been associated with violent disruption of a progenitor to the IVA parent. Another troilite sample, its chromite inclusions and adjacent metal were isotopically homogenized locally after 107Pd had decayed, possibly by a later episode of shock >50 Ma after Solar System formation.

  14. Kimberlite Ascent: Insights from Olivine (United States)

    Brett, C.; Russell, K.


    Olivine is ubiquitous in both extrusive and intrusive kimberlite deposits worldwide. Within kimberlite, it is mainly present as xenocrysts derived from the disaggregation of mantle-derived peridotitic xenoliths. Many textural and chemical features within the mantle-derived olivine xenocrysts result from post entrainment processes. On that basis, these features record physical and chemical changes attending kimberlite ascent and can be used to elucidate the transport and eruption of kimberlite magma. Our textural study of kimberlitic olivine is based on intrusive and pyroclastic kimberlite from the Diavik kimberlite cluster and from the Igwisi Hills kimberlitic lava flows. Based on these observations and the physical and chemical properties of olivine we derive a relative sequence of textural events. Textural features include: sealed cracks, healed cracks, phases trapping in cracks, rounded grains, overgrowths and phase trapping in overgrowths. These features record processes that operate in kimberlite during ascent, and from these features we create a summary model for kimberlite ascent: -- Olivine is incorporated into kimberlitic melts in peridotitic mantle xenoliths continuously during ascent. Xenolith incorporation is focused at the crack tip where the stress regime is highest. -- Shortly after the incorporation of these xenocrysts the tensile strength of the xenoliths is reached at a maximum of 2 km from its source. Disaggregation of mantle xenoliths (producing xenocrysts) is facilitated by expansion of the minerals within the xenoliths causing intra-crystal slip (i.e. along grain boundaries). -- Continued decompression causes olivine to also break in tension approximately 20 km from source. The void space produced by the failure of the crystals (inter-crystal cracks) is filled with melt and crystals consisting of primary carbonate (high-Sr), chromite and spinel crystals. The carbonate later crystallizes to produce sealed fractures. -- Mechanical rounding of

  15. Síntese de pós de LaMnO3 e LaCrO3 dopados com Sr pelo método de combustão: caracterização estrutural e avaliação termodinâmica Synthesis of Sr-doped LaMnO3 and LaCrO3 powders by combustion method: structural characterization and thermodynamic evaluation

    Directory of Open Access Journals (Sweden)

    A. L. A. da Silva


    Full Text Available Manganita de lantânio dopada com estrôncio (LSM e cromita (LSC em pó, bem como as correspondentes amostras não dopadas, foram sintetizadas pelo método de combustão, usando dois diferentes combustíveis (ureia e glicina. A ignição da mistura reacional com ureia leva mais tempo e a temperatura máxima é maior do que usando glicina, para as amostras dopadas. Os cálculos teóricos de calor de reação e temperatura de chama adiabática indicam condições favoráveis à combustão. No entanto, a calcinação é uma etapa essencial para uma boa cristalização da fase perovskita. Os padrões de difração de raios X mostraram a formação apenas da fase perovskita para as amostras sintetizadas com uréia. Os tamanhos de cristalitos estão na faixa de 19-25 nm, com valores menores quando a ureia é usada como combustível. Análises de microscopia eletrônica de varredura mostraram a presença de aglomerados, formados por partículas finas de diferentes formas. A análise termogravimétrica revelou que a perda de peso é muito maior para as manganitas, com queima completa dos orgânicos em 850-900 ºC.Lanthanum strontium manganite (LSM and chromite (LSC powders, as well as the corresponding non-doped samples, were synthesized by the combustion method, using two different fuels (urea and glycine. The ignition of the reagent mixture with urea takes a longer time and the maximum temperature is higher than using glycine, for doped samples. The theoretical calculations of exothermic heat and adiabatic flame temperatures indicate favorable conditions for combustion to occur. However, calcination is an essential step for a good crystallization of perovskite phase. X-ray diffraction patterns showed formation of only perovskite phase for the samples synthesized with urea. The crystallite sizes are in the range of 19-25 nm, with smaller values when urea was used as fuel. Scanning electron microscopy showed the presence of agglomerates, formed by fine

  16. Quantifying Density, Water Adsorption and Equilibration Properties of Wind Tunnel Materials (United States)

    Yu, Xinting; Horst, Sarah; He, Chao; Bridges, Nathan; Burr, Devon M.; Sebree, Joshua


    Aeolian processes are found on various planetary bodies including Earth, Venus, Mars, Titan, Triton, Pluto, and Comet 67P. Wind tunnels can simulate aeolian processes under different planetary parameters, with the robustness of results relying on experimental conditions and understanding of experimental materials. Threshold wind speed, the minimum wind speed to initiate saltation, is one parameter that can be investigated in wind tunnels. Liquid water adsorbed on wind tunnel materials could greatly enhance the threshold wind speed by increasing the interparticle force, density, and effective size of particles. Previous studies have shown that this effect could increase the threshold by 100% by putting 0.3-0.6% of water into typical dry quartz sand (Fecan et al. 1998). In order to simulate the weight of particles on other planetary bodies where gravity is significantly lower than on Earth, low-density materials are used in planetary wind tunnels, including walnut shells, activated charcoal, iced tea, and instant coffee.We first quantified the densities for all wind tunnel materials using a pycnometer and updated the density for low-density materials (e.g., walnut shells have density of 1.4 g/cm3 instead of 1.1 g/cm3 in the literature (Greeley et al. 1980)). Then we present a set of measurements that quantify water adsorption for both low and high-density materials (sand, basalt, and chromite). We first measured the water content and equilibration timescales for the materials through gravimetric measurements. We found low-density materials tend to have much more water (>5%) compared to high-density materials ( 6 hrs) compared to high-density materials (10-50 minutes). Since only water adsorbed on the particle surface would change the interparticle force, we then separate the surface and internal water using thermo-gravimetric analysis, and found that >80% of the water is still on the surface. Thus we assume water adsorption for low-density materials could greatly

  17. Controls on Highly Siderophile Element Concentrations in Martian Basalt: Sulfide Saturation and Under-Saturation (United States)

    Righter, Kevin


    Highly siderophile elements (HSE; Re, Au and the platinum group elements) in shergottites exhibit a wide range from very high, similar to the terrestrial mantle, to very low, similar to sulfide saturated mid ocean ridge basalt (e.g., [1]). This large range has been difficult to explain without good constraints on sulfide saturation or under-saturation [2]. A new model for prediction of sulfide saturation places new constraints on this problem [3]. Shergottite data: For primitive shergottites, pressure and temperature estimates are between 1.2-1.5 GPa, and 1350-1470 C [4]. The range of oxygen fugacities is from FMQ-2 to IW, where the amount of Fe2O3 is low and thus does not have a significant effect on the S saturation values. Finally, the bulk compositions of shergottites have been reported in many recent studies (e.g., [5]). All of this information will be used to test whether shergottites are sulfide saturated [3]. Modeling values and results: The database for HSE partition coefficients has been growing with many new data for silicates and oxides [6-8] to complement a large sulfide database [9- 11]. Combining these data with simple batch melting models allows HSE contents of mantle melts to be estimated for sulfide-bearing vs. sulfide-free mantle. Combining such models with fractional crystallization modeling (e.g., [12]) allows HSE contents of more evolved liquids to be modeled. Most primitive shergottites have high HSE contents (and low S contents) that can be explained by sulfide under-saturated melting of the mantle. An exception is Dhofar 019 which has high S contents and very low HSE contents suggesting sulfide saturation. Most evolved basaltic shergottites have lower S contents than saturation, and intermediate HSE contents that can be explained by olivine, pyroxene, and chromite fractionation. An exception is EET A79001 lithology B, which has very low HSE contents and S contents higher than sulfide saturation values . evidence for sulfide saturation

  18. Ophiolitic detritus in Kimmeridgian resedimented limestones and its provenance from an eroded obducted ophiolitic nappe stack south of the Northern Calcareous Alps (Austria

    Directory of Open Access Journals (Sweden)

    Gawlick Hans-Jürgen


    Full Text Available The causes for the Middle to Late Jurassic tectonic processes in the Northern Calcareous Alps are still controversially discussed. There are several contrasting models for these processes, formerly designated “Jurassic gravitational tectonics”. Whereas in the Dinarides or the Western Carpathians Jurassic ophiolite obduction and a Jurassic mountain building process with nappe thrusting is widely accepted, equivalent processes are still questioned for the Eastern Alps. For the Northern Calcareous Alps, an Early Cretaceous nappe thrusting process is widely favoured instead of a Jurassic one, obviously all other Jurassic features are nearly identical in the Northern Calcareous Alps, the Western Carpathians and the Dinarides. In contrast, the Jurassic basin evolutionary processes, as best documented in the Northern Calcareous Alps, were in recent times adopted to explain the Jurassic tectonic processes in the Carpathians and Dinarides. Whereas in the Western Carpathians Neotethys oceanic material is incorporated in the mélanges and in the Dinarides huge ophiolite nappes are preserved above the Jurassic basin fills and mélanges, Jurassic ophiolites or ophiolitic remains are not clearly documented in the Northern Calcareous Alps. Here we present chrome spinel analyses of ophiolitic detritic material from Kimmeridgian allodapic limestones in the central Northern Calcareous Alps. The Kimmeridgian age is proven by the occurrence of the benthic foraminifera Protopeneroplis striata and Labyrinthina mirabilis, the dasycladalean algae Salpingoporella pygmea, and the alga incertae sedis Pseudolithocodium carpathicum. From the geochemical composition the analysed spinels are pleonastes and show a dominance of Al-chromites (Fe3+–Cr3+–Al3+ diagram. In the Mg/(Mg+ Fe2+ vs. Cr/(Cr+ Al diagram they can be classified as type II ophiolites and in the TiO2 vs. Al2O3 diagram they plot into the SSZ peridotite field. All together this points to a harzburgite

  19. A metallic interconnect for a solid oxide fuel cell stack (United States)

    England, Diane Mildred

    A solid oxide fuel cell (SOFC) electrochemically converts the chemical energy of reaction into electrical energy. The commercial success of planar, SOFC stack technology has a number of challenges, one of which is the interconnect that electrically and physically connects the cathode of one cell to the anode of an adjacent cell in the SOFC stack and in addition, separates the anodic and cathodic gases. An SOFC stack operating at intermediate temperatures, between 600°C and 800°C, can utilize a metallic alloy as an interconnect material. Since the interconnect of an SOFC stack must operate in both air and fuel environments, the oxidation kinetics, adherence and electronic resistance of the oxide scales formed on commercial alloys were investigated in air and wet hydrogen under thermal cycling conditions to 800°C. The alloy, Haynes 230, exhibited the slowest oxidation kinetics and the lowest area-specific resistance as a function of oxidation time of all the alloys in air at 800°C. However, the area-specific resistance of the oxide scale formed on Haynes 230 in wet hydrogen was unacceptably high after only 500 hours of oxidation, which was attributed to the high resistivity of Cr2O3 in a reducing atmosphere. A study of the electrical conductivity of the minor phase manganese chromite, MnXCr3-XO4, in the oxide scale of Haynes 230, revealed that a composition closer to Mn2CrO4 had significantly higher electrical conductivity than that closer to MnCr 2O4. Haynes 230 was coated with Mn to form a phase closer to the Mn2CrO4 composition for application on the fuel side of the interconnect. U.S. Patent No. 6,054,231 is pending. Although coating a metallic alloy is inexpensive, the stringent economic requirements of SOFC stack technology required an alloy without coating for production applications. As no commercially available alloy, among the 41 alloys investigated, performed to the specifications required, a new alloy was created and designated DME-A2. The oxide scale

  20. Reconnaissance geologic map of the Dubakella Mountain 15 quadrangle, Trinity, Shasta, and Tehama Counties, California (United States)

    Irwin, William P.; Yule, J. Douglas; Court, Bradford L.; Snoke, Arthur W.; Stern, Laura A.; Copeland, William B.


    Cretaceous (about 120 Ma) metamorphic age. Remnants of the Great Valley sequence of dominantly Cretaceous marine sedimentary strata, which once covered much of the southern fringe of the Klamath Mountains, are present at three places in the Dubakella Mountain quadrangle. Mineral production in the quadrangle has included small amounts of gold, chromite, and manganese. This map of the Dubakella Mountain 15' quadrangle is a digital rendition of U.S. Geological Survey Miscellaneous Field Studies Map MF-1808, with various improvements and additions.

  1. Optimizing the application of magnetic nanoparticles in Cr(VI) removal (United States)

    Simeonidis, Konstantinos; Kaprara, Efthymia; Mitrakas, Manassis; Tziomaki, Magdalini; Angelakeris, Mavroidis; Vourlias, Georgios; Andritsos, Nikolaos


    The presence of heavy metals in aqueous systems is an intense health and environmental problem as implied by their harmful effects on human and other life forms. Among them, chromium is considered as an acutely hazardous compound contaminating the surface water from industrial wastes or entering the groundwater, the major source of drinking water, by leaching of chromite rocks. Chromium occurs in two stable oxidation states, Cr(III) and Cr(VI), with the hexavalent form being much more soluble and mobile in water having the ability to enter easily into living tissues or cells and thus become more toxic. Despite the established risks from Cr(VI)-containing water consumption and the increasing number of incidents, the E.U. tolerance limit for total chromium in potable water still stands at 50 μg/L. However, in the last years a worldwide debate concerning the establishment of a separate and very strict limit for the hexavalent form takes place. In practice, Cr(VI) is usually removed from water by various methods such as chemical coagulation/filtration, ion exchange, reverse osmosis and adsorption. Adsorption is considered as the simplest method which may become very effective if the process is facilitated by the incorporation of a Cr(VI) to Cr(III) reduction stage. This work studies the potential of using magnetic nanoparticles as adsorbing agents for Cr(VI) removal at the concentration levels met in contaminated drinking water. A variety of nanoparticles consisting of ferrites MFe2O4 (M=Fe, Co, Ni, Cu, Mn, Mg, Zn) were prepared by precipitating the corresponding bivalent or trivalent sulfate salts under controlled acidity and temperature. Electron microscopy and X-ray diffraction techniques were used to verify their crystal structure and determine the morphological characteristics. The mean particle size of the samples was found in the range 10-50 nm. Batch Cr(VI) removal tests were performed in aqueous nanoparticles dispersions showing the efficiency of ferrite

  2. Thorium partitioning in Greek industrial bauxite investigated by synchrotron radiation and laser-ablation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Gamaletsos, P. [Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupolis, 15784 Zographou (Greece); Godelitsas, A., E-mail: [Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupolis, 15784 Zographou (Greece); Mertzimekis, T.J. [Department of Physics, University of Athens, Panepistimioupolis, 15771 Zographou (Greece); Goettlicher, J.; Steininger, R. [Karlsruhe Institute of Technology, Institute for Synchrotron Radiation, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Xanthos, S. [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Berndt, J.; Klemme, S. [Institut fuer Mineralogie, Corrensstrasse 24, Universitaet Muenster, 48149 Muenster (Germany); Kuzmin, A. [Institute of Solid State Physics, University of Latvia, Kengaraga st. 8, 1063 Riga (Latvia); Bardossy, G. [Hungarian Academy of Sciences, H-1051 Budapest (Hungary)


    Typical red-brown (Fe-rich) and high-quality white-grey (Fe-depleted) bauxite samples from active mines of the Parnassos-Ghiona area, central Greece, were investigated. According to XRF and ICP-MS analyses their actinide content, and particularly of Th, is relatively increased. Fe-depleted samples contain up to 62.75 ppm Th corresponding to 220 Bq/kg due to {sup 228}Ac ({sup 232}Th-series), whereas Fe-rich samples are less Th-radioactive (up to 58.25 ppm Th, 180 Bq/kg due to {sup 228}Ac). Powder-XRD patterns showed that Th-enriched (Fe-depleted) bauxite consists mostly of diaspore (AlOOH polymorph), anatase and rutile (TiO{sub 2} polymorphs). SEM-EDS indicated the presence of Ti-Fe-containing phases (e.g. ilmenite, FeTiO{sub 3}), chromite (Cr-spinel) and besides LREE-minerals (mostly bastnaesite/parisite-group) and zircon (ZrSiO{sub 4}) hosting a part of the bulk Th. The presence of Th in diaspore and in Ti-containing phases (not detected by SEM-EDS as in the case of REE-minerals and zircon) was investigated, into distinct pisoliths of Fe-depleted bauxite, using {mu}-XRF and {mu}-XAFS in the SUL-X beamline of the ANKA Synchrotron facility (KIT, Germany). XAFS spectra of Th salts and Th-containing reference materials were obtained as well. Accordingly it was revealed, for the first time in the literature, that Ti-phases, and particularly anatase, host significant amounts of Th. This novel conclusion was complementary supported by LA-ICP-MS analyses indicated an average of 73 ppm Th in anatase grains together with abundant Nb (3356 ppm), Ta (247 ppm) and U (33 ppm). The Th L{sub III}-edge XAFS spectra as compared to reference materials, give also evidence that Th{sup 4+} may not replace Ti{sup 4+} in distorted [TiO{sub 6}] fundamental octahedral units of anatase and ilmenite lattice (CN = 6). The occupation of either extraframework sites of higher coordination (CN = 6.9 or even CN = 7.4), according to EXAFS signals evaluation, or of defected/vacant (**) sites is more

  3. An integrated geochemical, geophysical and mineralogical study of river sediments in alpine area and soil samples near steel plant, in Austria (United States)

    Irfan, M. I.; Meisel, T.


    Concentration of nickel and chromium in any part of the ecosystem is important for environmental concerns in particular human health due to the reason that some species of them can cause health problem e.g. dermatitis and cancer. Sediment samples collected form a river Vordernberger Bach (Leoben, Austria) in an alpine region and soil samples collected in an area adjacent to steel production unit in same narrow valley were investigated. In previous studies a correlation between magnetic susceptibility values and concentration of nickel and chromium showed that a magnetic susceptibility meter can be used to point out the contaminated areas as in-situ device. The purpose of the whole study is to understand the real (point or diffuse, anthropogenic or geogenic) sources of contamination of soils, water and river sediments through heavy metal deposition. Unseparated, magnetic and non-magnetic fractions of soil samples were investigated for geochemical and mineralogical aspects with XRF, ICP-MS, EMPA, Multi-Functional Kappabridge (MFK1) and laser ablation coupled with ICP-MS. Mineralogical study of sediment samples for several sampling points with higher Ni and Cr content was performed. Sediment samples were sieved below 1.4 mm and then a concentrate of heavy minerals was prepared in the field through panning. Concentrated heavy minerals were then subjected for heavy liquid separation in the laboratory. Separated magnetic and non-magnetic fractions below 0.71/0.1 mm and density greater than 2.9 g/cm3 were selected for mineralogical investigation. The abundance of typical anthropogenic particles, e.g., spherical, tinder, roasted ores, iron and steel mill slag was observed under the microscope. Magnetite (mostly anthropogenic), maghemite, chromspinel, chromite (type I & II), (Ca,Al)-ferrite, wustite, apatite (anthropogenic), olivine mixed crystals, calcium silicate and spinel (anthropogenic) are found in magnetic fraction. Non-magnetic fractions contain hematite, siderite

  4. Cooperative Jahn–Teller effect and the role of strain in the tetragonal-to-cubic phase transition in MgxCu1 − xCr2O4

    Directory of Open Access Journals (Sweden)

    Serena C. Tarantino


    Full Text Available Temperature and composition dependences of the I41/amd → Fd\\bar 3m phase transition in the MgxCu1 − xCr2O4 spinel solid solution, due to the melting of the cooperative Jahn–Teller distortion, have been studied by means of single-crystal X-ray diffraction. Crystals with x = 0, 0.10, 0.18, 0.43, 0.46, 0.53, 1 were grown by flux decomposition methods. All crystals have been refined in the tetragonal I41/amd space group except for the Mg end-member, which has cubic symmetry. In MgxCu1 − xCr2O4 the progressive substitution of the Jahn–Teller, d9 Cu2+ cation with spherical and closed-shell Mg2+ has a substantial effect on the crystal structure, such that there is a gradual reduction of the splitting of a and c unit-cell parameters and flattening of the tetrahedra. Single-crystal diffraction data collected in situ up to T = 1173 K show that the tetragonal-to-cubic transition temperature decreases with increasing Mg content. The strength of the Cu—Cu interaction is, in effect, modulated by varying the Cu/Mg ratio. Structure refinements of diffraction data collected at different temperatures reveal that heating results in a gradual reduction in the tetrahedron compression, which remains significant until near the transition temperature, however, at which point the distortion of the tetrahedra rapidly vanishes. The spontaneous strain arising in the tetragonal phase is large, amounting to 10% shear strain, et, and ∼ 1% volume strain, Vs, in the copper chromite end-member at room temperature. Observed strain relationships are consistent with pseudoproper ferroelastic behaviour (e_{\\rm t}^2 ∝ Vs ∝ q_{\\rm JT}^2, where qJT is the order parameter. The I41/amd → Fd\\bar 3m phase transition is first order in character for Cu-rich samples and then evolves towards second-order character. Although a third order term is permitted by symmetry in the Landau expansion, this behaviour appears to be more accurately represented by a 246

  5. Precious metal enrichment at low-redox in terrestrial native Fe-bearing basalts investigated using laser-ablation ICP-MS (United States)

    Howarth, Geoffrey H.; Day, James M. D.; Pernet-Fisher, John F.; Goodrich, Cyrena A.; Pearson, D. Graham; Luo, Yan; Ryabov, Viktor V.; Taylor, Lawrence A.


    Primary native Fe is a rare crystallizing phase from terrestrial basaltic magmas, requiring highly reducing conditions (fO2 group elements [PGE], Pd, Pt, Rh, Ru, Ir, Os), as well as Ni and Cu, to economic abundances. Three localities are known globally where native Fe bearing mafic rocks occur: (1) Paleocene basalts of Disko Island, West Greenland; (2) a Miocene lava of the Bühl basalts, Germany; and (3) mafic intrusions associated with the Late Permian Siberian flood basalts. In this contribution, we report major- and minor-element compositions and HSE concentrations for the main alloy phases (FeNi metal and cohenite) and sulfide, for all three known global occurrences of native Fe bearing basalt. Total HSE abundances in metal grains, obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), are lowest in the Bühl basalt, (∼0.05 ppm), intermediate in the Disko Island basalts (4-8 ppm), and highest the Siberian Khungtukun and Dzhaltul intrusions (10-30 ppm). These differences demonstrate that, while native Fe formation is the result of carbonaceous crustal assimilation, HSE enrichment is not ubiquitous during this process. The Siberian occurrences are characterized by Pt PGE (PPGE: Pt, Pd) enrichment relative to the Ir PGE (IPGE: Rh, Ru, Ir, Os), consistent with models of early stage fractionation of olivine, chromite and metallic IPGE in staging magma reservoirs, prior to the addition of C-rich crustal materials in the shallow crust. Relative to Noril'sk Ni-Cu-PGE sulfide ores, the Siberian native Fe basalts are enriched in the PPGE relative to the IPGE, but exhibit Ru enrichments. In contrast, Disko Island native Fe rocks do not show significant fractionation of the PPGE from the IPGE, but have positive Re and Ru anomalies and high Os/Ir ratios. To reconcile these observations, we present a general model where some parental melts experienced early-stage crustal assimilation in staging magma reservoirs, prior to reduction by carbon

  6. Thorium partitioning in Greek industrial bauxite investigated by synchrotron radiation and laser-ablation techniques (United States)

    Gamaletsos, P.; Godelitsas, A.; Mertzimekis, T. J.; Göttlicher, J.; Steininger, R.; Xanthos, S.; Berndt, J.; Klemme, S.; Kuzmin, A.; Bárdossy, G.


    Typical red-brown (Fe-rich) and high-quality white-grey (Fe-depleted) bauxite samples from active mines of the Parnassos-Ghiona area, central Greece, were investigated. According to XRF and ICP-MS analyses their actinide content, and particularly of Th, is relatively increased. Fe-depleted samples contain up to 62.75 ppm Th corresponding to 220 Bq/kg due to 228Ac ( 232Th-series), whereas Fe-rich samples are less Th-radioactive (up to 58.25 ppm Th, 180 Bq/kg due to 228Ac). Powder-XRD patterns showed that Th-enriched (Fe-depleted) bauxite consists mostly of diaspore (AlOOH polymorph), anatase and rutile (TiO 2 polymorphs). SEM-EDS indicated the presence of Ti-Fe-containing phases (e.g. ilmenite, FeTiO 3), chromite (Cr-spinel) and besides LREE-minerals (mostly bastnäsite/parisite-group) and zircon (ZrSiO 4) hosting a part of the bulk Th. The presence of Th in diaspore and in Ti-containing phases (not detected by SEM-EDS as in the case of REE-minerals and zircon) was investigated, into distinct pisoliths of Fe-depleted bauxite, using μ-XRF and μ-XAFS in the SUL-X beamline of the ANKA Synchrotron facility (KIT, Germany). XAFS spectra of Th salts and Th-containing reference materials were obtained as well. Accordingly it was revealed, for the first time in the literature, that Ti-phases, and particularly anatase, host significant amounts of Th. This novel conclusion was complementary supported by LA-ICP-MS analyses indicated an average of 73 ppm Th in anatase grains together with abundant Nb (3356 ppm), Ta (247 ppm) and U (33 ppm). The Th LIII-edge XAFS spectra as compared to reference materials, give also evidence that Th 4+ may not replace Ti 4+ in distorted [TiO 6] fundamental octahedral units of anatase and ilmenite lattice (CN = 6). The occupation of either extraframework sites of higher coordination (CN = 6.9 or even CN = 7.4), according to EXAFS signals evaluation, or of defected/vacant (**) sites is more probable. This is likely explained by the difficulty of

  7. Materials for Advanced Ultrasupercritical Steam Turbines Task 4: Cast Superalloy Development

    Energy Technology Data Exchange (ETDEWEB)

    Thangirala, Mani


    demonstrated the importance of proper heat treat cycles for Homogenization, and Solutionizing parameters selection and implementation. 3) Step blocks casting of Nimonic 263: Carried out casting solidification simulation analysis, NDT inspection methods evaluation, detailed test matrix for Chemical, Tensile, LCF, stress rupture, CVN impact, hardness and J1C Fracture toughness section sensitivity data and were reported. 4) Centrifugal Casting of Haynes 282, weighing 1400 lbs. with hybrid mold (half Graphite and half Chromite sand) mold assembly was cast using compressor casing production tooling. This test provided Mold cooling rates influence on centrifugally cast microstructure and mechanical properties. Graphite mold section out performs sand mold across all temperatures for 0.2% YS; %Elongation, %RA, UTS at 1400°F. Both Stress-LMP and conditional Fracture toughness plots data were in the scatter band of the wrought alloy. 5) Fundamental Studies on Cooling rates and SDAS test program. Evaluated the influence of 6 mold materials Silica, Chromite, Alumina, Silica with Indirect Chills, Zircon and Graphite on casting solidification cooling rates. Actual Casting cooling rates through Liquidus to Solidus phase transition were measured with 3 different locations based thermocouples placed in each mold. Compared with solidification simulation cooling rates and measurement of SDAS, microstructure features were reported. The test results provided engineered casting potential methods, applicable for heavy section Haynes 282 castings for optimal properties, with foundry process methods and tools. 6) Large casting of Haynes 282 Drawings and Engineering FEM models and supplemental requirements with applicable specifications were provided to suppliers for the steam turbine proto type feature valve casing casting. Molding, melting and casting pouring completed per approved Manufacturing Process Plan during 2014 Q4. The partial valve casing was successfully cast after casting methods were

  8. Marché des catalyseurs d'hydrogénation des corps gras Market of Hydrogenation Catalysts for Fats and Derivatives

    Directory of Open Access Journals (Sweden)

    Barraque M.


    Full Text Available L'institut Français du Pétrole (IFP ayant acquis une grande expérience dans le domaine des catalyseurs, notamment d'hydrogénation, le Département Evaluation a effectué à diverses reprises des études qui en évaluent les marchés potentiels. L'analyse qui suit a été réalisée en vue de déterminer les débouchés possibles des catalyseurs utilisés dans l'hydrogénation des corps gras; elle couvre l'industrie alimentaire, l'hydrogénation des acides gras d'origine animale ou végétale, la production d'alcools gras et d'amines grasses. Ce marché dépasse 60 millions de dollars/an et correspond à près de 11 000 t/an de catalyseurs utilisés. Ces valeurs tiennent compte des consommations captives de catalyseurs produits par les compagnies utilisatrices. Ce chiffre d'affaires est du même ordre que celui des catalyseurs d'hydrogénation utilisés dans la synthèse des grands intermédiaires pétrochimiques. Plus de 64 % des applications concernent l'industrie alimentaire : production de margarine et shortening, hydrogénation d'huiles de salade et de friture aux États-Unis. Alors que la consommation de catalyseurs utilisés en lipochimie est très fortement concentrée dans les principales régions industrialisées : États-Unis, Europe occidentale et Japon, celle de I'lindustrie alimentaire est beaucoup plus dispersée : les 3 régions précitées représentent moins de 64 % de la consommation mondiale. Les débouchés estimés représentent des chiffres d'affaires annuels de 41×10·6 dollars pour l'industrie alimentaire, 8,3×10·6 dollars pour la production d'acide gras, 11×10·6 dollars pour la production d'alcools gras et 1,3×10·6 dollars pour la production d'amines grasses. Ces hydrogénations sont effectuées en présence de nickel sur support (industrie alimentaire, production d'acides gras et d'amines secondaires et tertiaires, en présence de nickel de Raney (production d'amines primaires ou de chromite de cuivre

  9. Phosphorus zoning in olivine of Kilauea Iki lava lake, Hawaii (United States)

    Fabbrizio, Alessandro; Beckett, John R.; Baker, Michael B.; Stolper, Edward M.


    low P chambers and P enriched zones were also observed; near the margins of the crystals is possible to find the presence of discontinuous sets of P-enriched bands that generally outline euhedral crystal forms; some crystals are characterized by P-enriched ghosts of relict crystals in their interior that are associated with probable undercooling and/or with an initial pulse of rapid crystal growth [8, 10]. Phenocrysts and microphenocrysts are frequently unzoned in major and minor divalent cations (Fe, Mg, Mn, Ca, Ni), but all are zoned in P. Variations in Cr and Al correlate spatially with P but are much fainter or absents, in some crystal the P-enriched bands are superimposed with small crystals of chromite (≤1 μm) aligned along the P zoning. Probably these chromites were formed by precipitation from the original Cr and Al bands. In no case was observed Ti zoning. [1] Richter D.H. et al. (1970) US Geol Surv Prof Pap 537-E, 73 p. [2] Richter D.H., Moore J.G. (1966) US Geol Surv Prof Pap 537-B, 26 p. [3] Helz R.T. (1980) Bull Volcanol 43-4, 675-701. [4] Helz R.T. et al. (1984) US Geol Surv Open File Rep 84-484, 72 p. [5] Hardee H.C. et al. (1981) Geophys Res Lett 8, 1211-1214. [6] Helz R.T., Wright T.L. (1983) US Geol Surv Open File Rep 83-326, 66 p. [7] Helz R.T. (1987) Geochem Soc Spec Pub 1, 241-258. [8] Beckett J.R. et al. (2008) LPSC abs. 1726. [9] Mccanta M.C. et al. (2008) LPSC abs. 1807. [10] Milmann-Barris M.S. et al. (2008) CMP 155, 739-765. [11] Mccanta M.C. et al. (2008) GCA 72-12, S1, A610.

  10. Petrology and Geochemistry of LEW 88663 and PAT 91501: High Petrologic L Chondrites (United States)

    Mittlefehldt, D. W.; Lindstrom, M. M.; Field, S. W.


    Primitive achondrites (e.g., Acapulco, Lodran) are believed to be highly metamorphosed chondritic materials, perhaps up to the point of anatexis in some types. Low petrologic grade equivalents of these achondrites are unknown, so the petrologic transition from chondritic to achondritic material cannot be documented. However, there are rare L chondrites of petrologic grade 7 that may have experienced igneous processes, and study of these may yield information relevant to the formation of primitive achondrites, and perhaps basaltic achondrites, from chondritic precursors. We have begun the study of the L7 chondrites LEW 88663 and PAT 91501 as part of our broader study of primitive achondrites. Here, we present our preliminary petrologic and geochemical data on these meteorites. Petrology and Mineral Compositions: LEW 88663 is a granular achondrite composed of equant, subhedral to anhedral olivine grains poikilitically enclosed in networks of orthopyroxene and plagioclase. Small grains of clinopyroxene are spatially associated with orthopyroxene. Troilite occurs as large anhedral and small rounded grains. The smaller troilite grains are associated with the orthopyroxene-plagioclase networks. PAT 91501 is a vesicular stone containing centimeter-sized troilite +/- metal nodules. Its texture consists of anhedral to euhedral olivine grains, anhedral orthopyroxene grains (some with euhedral clinopyroxene overgrowths), anhedral to euhedral clinopyroxene, and interstitial plagioclase and SiO2-Al2O3-K2O- rich glass. In some areas, olivine is poikilitically enclosed in orthopyroxene. Fine-grained troilite, metal, and euhedral chromite occur interstitial to the silicates. Average mineral compositions for LEW 88663 are olivine Fo(sub)75.8, orthopyroxene Wo(sub)3.4En(sub)76.2Fs(sub)20.4, clinopyroxene Wo(sub)42.6En(sub)47.8Fs(sub)9.6, plagioclase Ab(sub)75.0An(sub)21.6Or(sub)3.4. Mineral compositions for PAT 91501 are olivine Fo(sub)73.8, orthopyroxene Wo(sub)4.5En(sub)74.8Fs

  11. Determination of heavy metal elements in various soils by microwave assisted extraction with acid mixture and ICP-MS%混酸微波辅助萃取ICP-MS测定不同性质土壤中的重金属元素∗

    Institute of Scientific and Technical Information of China (English)

    孙婧; 马丽; 杨兆光; 王琳


    The extraction efficiency of heavy metals ( Pb, Cd, As, Cr, Ni, Cu and Zn) in soils was compared using four digestive solutions: HNO3 , HNO3⁃HCl, HNO3⁃HCl⁃H2 O2 and HNO3⁃HCl⁃HClO4 . The highest extraction efficiency was obtained with HNO3⁃HCl⁃HClO4 , followed by HNO3⁃HCl in six certified reference soils. The concentrations of acid extractable heavy metals were close to their total amounts except chromium. Due to the high proportion of chromite which is stable in environmental condition, it would be more appropriate to assess environmental risk of chromium using acid extractable concentrations. Adsorption of heavy metals to soils was related to parent materials. Due to strong adsorption to alluvial sediments, lead, zinc and copper were relatively difficult to be extracted. The adsorption of cadmium, nickel and arsenic to soil represented weak correlation with parent materials. The proposed extraction method was applied to extract heavy metals from sediments and field soils around a mining area. The results determined by ICP⁃MS illustrated that the sediments contained high concentrations of heavy metals and were likely water⁃carried alluviation of tailings. The field soils were contaminated by heavy metals by various degrees.%比较了硝酸( HNO3)、硝酸⁃盐酸( HNO3∶HCl=3∶1)、硝酸⁃盐酸⁃双氧水( HNO3∶HCl∶H2 O2=3∶1∶1)和硝酸⁃盐酸⁃高氯酸(HNO3∶HCl∶HClO4=3∶1∶1)等4种消解液对土壤中铅(Pb)、镉(Cd)、砷(As)、铬(Cr)、镍( Ni)、铜( Cu)和锌( Zn)等7种重金属元素的萃取效率。结果表明,硝酸⁃盐酸⁃高氯酸混合液的萃取效果最好,硝酸⁃盐酸混合液次之。通过对6种土壤标准物质的分析发现,除了Cr之外,其他重金属元素在土壤中的混酸微波可提取态含量与总含量接近。土壤中的Cr有一部分是以铬铁矿的形式存在,在环境中相对较为稳定,采用混酸

  12. Petrology, geochemistry, and age of low-Ti mare-basalt meteorite Northeast Africa 003-A: A possible member of the Apollo 15 mare basaltic suite (United States)

    Haloda, Jakub; Týcová, Patricie; Korotev, Randy L.; Fernandes, Vera A.; Burgess, Ray; Thöni, Martin; Jelenc, Monika; Jakeš, Petr; Gabzdyl, Pavel; Košler, Jan


    Northeast Africa 003 (NEA 003) is a lunar meteorite found as a two paired stones (6 and 118 g) in Libya, 2000 and 2001. The main portion (˜75 vol%) of the 118 g meteorite, used for this study, (NEA 003-A) consists of mare-basalt and a smaller adjacent portion (˜25 vol%) is a basaltic breccia (NEA 003-B). NEA 003-A has a coarse-grained magmatic texture consisting mainly of olivine, pyroxene and plagioclase. The late-stage mineral association is composed mainly of elongated plagioclase, ilmenite, troilite, fayalite, Si-K-rich glass, apatite, and a rare SiO 2 phase. Other accessory minerals include ulvöspinel, chromite, and trace Fe-Ni metal. Olivine and pyroxene contain shock-induced fractures, and plagioclase is completely converted into maskelynite. The Fe/Mn values of the whole rock, olivines and pyroxenes, and the bulk-rock oxygen isotopic composition provide evidence for the lunar origin of NEA 003-A meteorite. This is further supported by the presence of Fe-Ni metal and the anhydrous mineral association. NEA 003-A is geochemically and petrographically distinct from previously described mare-basalt meteorites and is not paired with any of them. The petrography and major element composition of NEA 003-A is similar to the composition of low-Ti olivine mare basalts from Apollo 12 and olivine-normative basalts from Apollo 15. The NEA 003-A meteorite shows obvious geochemical similarities in trace elements contents with Apollo 15 olivine-normative basalts and could represent a yet unknown geochemically primitive member of the olivine-normative basalt series. The meteorite is depleted in rare earth elements (REE) and incompatible trace elements indicating a primitive character of the parental magma. The bulk-rock chemical composition demonstrates that the parent melt of NEA 003-A was not contaminated with KREEP components as a result of magma mixing or assimilation processes. Results of crystallization modelling and low minimum cooling rate estimates (˜0.07

  13. Behavior of major and trace elements upon weathering of peridotites in New Caledonia : A possible site on ultramafic rocks for the Critical Zone Exploration Network (CZEN) ? (United States)

    Juillot, Farid; Fandeur, D.; Fritsch, E.; Morin, G.; Ambrosi, J. P.; Olivi, L.; Cognigni, A.; Hazemann, J. L.; Proux, O.; Webb, S.; Brown, G. E., Jr.


    Ultramafic rocks cover about 1% of the continental surfaces and are related to ophiolitic bodies formed near convergent plate boundaries (Coleman, 1977). The most typical ultramafic rocks are dunite and harzburgite, which are composed of easily weatherable ferromagnesian mineral species (olivines and pyroxenes), but also of more resistant spinels (chromite and magnetite). Oceanic serpentinization of these ultramafic rocks usually lead to partial transformation of these initial mineral assemblages by forming hydrous layer silicates such as serpentine (lizardite, chrysotile and antigorite) talc, chlorite and actinolite (Malpas, 1992). It also lead to the formation of highly sheared textures, which favor meteoric weathering through preferential water flows. Compared to their crystalline rock counterpart that covers most of the continental surfaces, these ultramafic rocks mainly differ by their lower SiO2, Al2O3 and K2O contents (less than 50%, 10% and 1%, respectively) and, on the opposite, much higher MgO content (more than 18%). Moreover, they commonly have higher concentrations in FeO and other trace elements, such as Ni, Cr, Mn and Co. Weathering of these rocks is then at the origin of major geochemical anomalies on continental surfaces, especially when they occur in tropical and subtropical regions. Such conditions are encountered in New Caledonia where one third of the surface is covered with peridotites (mainly harzburgite with small amounts of dunite) obducted about 35 millions years ago during large tectonic events in the Southwest Pacific at the Late Eocene (Cluzel et al., 2001). Tropical weathering of these ultramafic rocks lead to the development of thick lateritic regoliths where almost all Mg and Si have been leached out and Fe, Mn, Ni, Cr and Co have been relatively concentrated. In these oxisols, Ni, Cr and Co can exhibit concentration up to several wt%, which make them good candidates for ore mining (New Caledonia is the third Ni producer in the world

  14. Lithophile and siderophile element systematics of Earth's mantle at the Archean-Proterozoic boundary: Evidence from 2.4 Ga komatiites (United States)

    Puchtel, I. S.; Touboul, M.; Blichert-Toft, J.; Walker, R. J.; Brandon, A. D.; Nicklas, R. W.; Kulikov, V. S.; Samsonov, A. V.


    New Os isotope and highly siderophile element (HSE) abundance data, in combination with lithophile trace element and Sm-Nd, Lu-Hf, and Hf-W isotope data, are reported for komatiitic basalts from the Vetreny Belt and tonalites from the adjacent Vodla Block in the Fennoscandian Shield. Komatiitic basalts define a Re-Os isochron with an age of 2407 ± 6 Ma and an initial γ187Os = +1.7 ± 0.2 (2 SE). The Pt-Os data for chromite separates yield an average initial ε186Os = +0.03 ± 0.02 (2 SE). The 147Sm-143Nd and 176Lu-176Hf data for the komatiitic basalts give isochron ages and initial ratios of, respectively, 2403 ± 32 Ma and ε143Nd = -0.90 ± 0.09, and 2451 ± 79 Ma and ε176Hf = +0.4 ± 0.2 (2 SE). Bulk tonalites are characterized by average initial γ187Os, ε143Nd, and ε176Hf values of +304 ± 64, +1.8 ± 0.6, and +2.5 ± 1.6 (2 SE), respectively, when calculated for the ∼3.21 Ga age of the rocks. The komatiitic basalts and tonalites have μ142Nd values of, respectively, +0.5 ± 2.8 and -0.4 ± 5.2 (2 SD). By contrast, both the komatiitic basalts and tonalites exhibit positive 182W anomalies of +7.1 ± 4.5 and +12.6 ± 4.5 ppm (2 SD), respectively. The komatiitic basalts were derived from a komatiitic parental magma with ∼27 wt.% MgO; it was modified by both assimilation of the tonalites and fractional crystallization en route to the surface. Lithophile trace element data constrain the degree of crustal contamination to be 4.0 ± 0.4%. Highly siderophile element abundance data indicate that crustal contamination must have had a negligible effect on the Os isotopic composition of the komatiitic parental magma. By contrast, the Nd, Hf, and W isotope systematics of the komatiitic parental magma were strongly modified as a result of assimilation of the tonalites. The positive initial ε143Nd and ε176Hf values of the tonalites indicate that they formed via melting of a precursor with time-integrated suprachondritic Sm/Nd and Lu/Hf. This precursor was most

  15. In Situ Trace Element Measurements on Roda and the Origin of Diogenites (United States)

    Mittlefehldt, David W.; Herrin, J. S.


    The origin of diogenites remains poorly understood. A recent model interprets many diogenites to have been formed from melts that were derived by remelting initial magma ocean cumulates, and these penultimate parent melts were then contaminated by melts derived from remelting of the basaltic (eucritic) crust to form the ultimate diogenite parent melts [1] (hereafter the remelting model). This is a very complicated petrogenesis that has profound implications for the geological evolution of 4 Vesta if correct. This model was developed based on trace element analyses of bulk rock samples that had been leached in acids to remove phosphates; the compositions of the residues were interpreted to be close to those of cumulus orthopyroxenes plagioclase, chromite and olivine [1]. In situ measurements of phases in diogenites can be used to test this model. We have begun a campaign of laser ablation ICP-MS of orthopyroxene grains in diogenites for this purpose. Here we report our first results on one diogenite, Roda. We have determined a suite of trace lithophile elements on nine, mm-sized pyroxene grains separated from Roda that have previously been studied [2, 3]. A key observation supporting the remelting model is the very low Eu/Eu* of leached residues; values too low to represent orthopyroxene that crystallized from melts with chondritic Sm/Eu and Gd/Eu [1]. (Eu* = Eu interpolated from REE diagrams.) Crustal remelts have low Sm/Eu and Gd/Eu, and orthopyroxenes that crystallized from parent melts contaminated by them would have very low Eu/Eu* [1]. Roda grains have Eu/Eu* of 0.243 to 0.026; the latter a value lower than any measured on bulk diogenite leached residues (0.041) [1]. There is a general negative correlation between Eu/Eu* and some incompatible elements (Zr, Nb, Hf), but not others (LREE). This appears inconsistent with the remelting model as it would suggest an evolving parent melt with La de-creasing as Zr increased and Eu/Eu* decreased. Grain R-15 includes

  16. Identification And Interpretation Of Eclogite Protoliths Using Immobile Element Geochemistry: Some New Methodologies (United States)

    Pearce, J. A.; Robinson, P.; Yang, J.


    Methodologies for fingerprinting metabasalts have been applied to eclogites with mixed success. Some, including Alpine examples famously studied by Gary Ernst >30 years ago, have been successfully assigned to tectonic settings and the results used to understand the now-disappeared ocean and its margins. Others, however, present two particular, well-documented problems: 1) many are cumulates rather than lavas and so have very low abundances of some elements as well as non-liquid compositions; 2) the subduction and exhumation processes can lead to infiltration of the protolith by subduction- and crustally-derived fluids/melts before and after eclogite-facies metamorphism and so impart apparent subduction or continental character even when none existed. Here we demonstrate new methodologies for dealing with these issues, taking as an example the eclogites from the Chinese Continental Scientific Drilling (CCSD) Deep Borehole. We adopt a set of immobile element proxies that highlight the presence and behaviour of particular cumulate phases (e.g. Cr for chromite, Ni for olivine, Sc,V for clinopyroxene, Ti,V for oxide, Ga for plagioclase, P and Zr for apatite and zircon, Nb for interstitial melt). Using a training data set from well-studied cumulate sequences such as Bushveld and Skaergaard, we can assign protolith rock names on the basis of these proxy elements. Variation diagrams enable us identify the crystallization sequence of the plutonic protolith, itself a function of the original tectonic setting. For example, the Borehole contains a thick, eclogite-facies cumulate sequence which we can reconstruct in detail as a layered complex containing cumulate dunite and peridotite, mela-troctolite, troctolite, gabbro, ferrogabbro, ferrodiorite, quartz-diorite and tonalite. The iron enrichment and inferred saturation sequence of chr+ol-plag-cpx-mt-ap-zr are characteristic of low-oxygen fugacity, tholeiitic MORB and continental margin intrusions. In this, and more easily in

  17. Origin of the Luobusa diamond-bearing peridotites from the sub-arc mantle (United States)

    Liu, Chuanzhou; Zhang, Chang; Wu, Fuyuang; Chung, Sunlin


    -arc lithospheric mantle was exhumed at seafloor during the Early Cretaceous, in response to the fore-arc hyperextension (Maffione et al., 2015), and intruded by mafic dykes resulting from decompression melting of the ascended asthenosphere (Zhang et al., 2015). Reference Maffione, M. et al. Forearc hyperextension dismembered the south Tibetan ophiolites. Geology 46, 475-478 (2015). Robinson, P. T. et al. The origin and significance of crustal minerals in ophiolitic chromitites and peridotites. Gond. Res., 486-506 (2015). Yang, J. S. et al. Diamond- and coesite-bearing chromitites from the Luobusa ophiolite, Tibet. Geology 35, 875-878 (2007). Yang, J. S., Robinson, P. T. & Dilek, Y. Diamonds in ophiolites. Elements 10, 127-130 (2014). Zhang, C., Liu, C. Z., Wu, F. Y., Zhang, L. L. & Ji, W. Q. Geochemistry and geochronology of maifc rocks from the Luobusa ophiolite, South Tibet. Lithos, 10.1016/j.lithos.2015.1006.1031 (2015). Zhou, M. F., Robinson, P. T., Malpas, J. & Li, Z. J. Podiform chromitites in the Luobusa Ophiolite (Southern Tibet): Implications for melt-rock interaction and chromite segregation in the upper mantle. J. Petrol. 37, 3-21 (1996).

  18. Heavy mineral concentrations in the sandstones of Amij Formation with particular emphasis on the mineral chemistry and petrographic characteristics of monazite, western desert of Iraq (United States)

    Kettanah, Yawooz A.; Ismail, Sabah A.


    The heavy minerals in the clastic unit of the Lower Jurassic Amij Formation exposed in the western desert of Iraq were studied. The uppermost part of the clastic unit contains thin, placer-like black sandstone horizons that are radioactive and abnormally rich in heavy minerals (0.6-56%), dominated by opaque (65%) and transparent (35%) heavy minerals. The minerals, in the order of decreasing abundance are pseudorutile, goethite, zircon, hematite, magnetite, monazite, rutile, leucoxene, tourmaline, ilmenite, chromite, and few others. Electron probe microanalysis (EPMA), microscopic and autoradiographic observations and analysis showed that the monazite is monazite-(Ce) type with an average composition of (Ce0.39Nd0.16La0.19Pr0.04Sm0.02Gd0.02Eu0.01Y0·04Th0·06U0·01Ca0·05Fe0.01)(P0·98Si0.03)O4. Monazite consists predominantly of REE-oxides (57.93%) and P2O5 (29.31%), with minor amounts of ThO2 (6.60%), Y2O3 (1.92%), UO2 (0.76%), CaO (1.14%), SiO2 (0.69%), and FeOt (0.17%). The dominant compositional substitution operating between REE and P were a mixture of the complex cheralite type substitution ([REE]-2 [Th][Ca]) and the coupled huttonite type substitution ([REE]-1 [P]-1 [Th][Si]). The chondrite-normalized REE distribution patterns of monazite show enrichment in LREE with positive Eu- and Pr-anomalies of 1.46 and 9.13, respectively. The median values of (La/Sm)CN and (La/Nd)CN ratios are 4.35 and 1.97, respectively. Zircon which is the dominant transparent mineral is Hf-rich that is composed of 30.61% SiO2, 57.58% ZrO2, 7.03% HfO2, 2.04% Y2O3, 0.56% ThO2, 0.19% UO2, and 0.19% Al2O3 corresponding to a formula (Zr0.909Hf0.065Th0·004U0·001Y0.031)Σ1.011(Si3·966Al0.028)Σ0.999O4. Rutile and tourmaline form 7% and 4% of the heavy minerals. Ilmenite which is one of the predominant heavy minerals forms 2.5% of the opaques because it is pervasively altered to Ti-Fe oxides. In addition of zircon and monazite, the chemical compositions of most of the other heavy

  19. 南极格罗夫山陨石CRV 020043—一个特殊的E/H过渡型球粒陨石%GRV 020043-A Special Transition Chondrite Between E and H Group

    Institute of Scientific and Technical Information of China (English)

    李世杰; 王世杰; 刘燊; 李雄耀; 唐红; 李芃


    Grove Mountains (GRV) 020043 is a special chondrite, which has the same mineral assemblage as ordinary chondrite,but it has its own mineral compositions beyond those of the ordinary chondrites. The stone is composed of Low-Ca pyroxene (40 vol%), olivine (24vo1%), diopside (8 vol%), plagioclase (10vol%) ,troilite(4 vol%), Fe-Ni alloy (14 vol%), and trace of chromite and apatite. The silicates have homogeneous compositions, e. g. olivine (Fa10.4-12.4, average Fa11.0 ) and Low-Ca pyroxene (Fs10.1-11.6,average Fs10.9 ) , diopside ( Wo46.1-47.1 En49.0-49.2 Fs3.8-4.4 , average Wo46.6 En49.3 Fs4.0 ), plgioclase ( Ab55.7-72.5 Or2.1-5.0 An24.0-42.1, average Ab67.6 Or3.4 An29.0 ). Some chondrules in this meteorite are well defined with sharp edges, with the chondrules aboundence of 37 vol%. The matrix of the meteorite is moderately recrystallized. Its petrologic type is 4. Based on its mineral compositions, olivine model abundance and oxidation intensity of GRV 020043 are restricted between E and H groups. The chondrite is classified classed as a transition chondrite between E and H group.%南极格罗夫山陨石GRV 020043是一块特殊的球粒陨石,虽与普通球粒陨石有着相似的矿物组合,但矿物成分超出普通球粒陨石范围.主要矿物组合及其模式含量(vol%)是:斜方辉石40、橄榄石24、透辉石8、斜长石10、 Fe-Ni合金14、陨硫铁4 vol%、及少量铬铁矿和磷灰石.主要组成矿物成分均一,如斜方辉石(Fs10.1~11.6,平均Fs10.9)、橄榄石(Fa10.4-12.4,平均Fa11.0)、透辉石(Wo46.1-47.1En49.0-49.6Fs3.8-4.4,平均Wo46.6En49.3Fs4.0)、斜长石(Ab55.7-72.5Or2.1-5.0An24.0-42.1,平均 Ab67.6Or3.4An29.0)等.该陨石球粒轮廓清晰结构完整,球粒丰度37%(体积比),基质具有中等重结晶,岩石类型属于4型.根据矿物成分判断, GRV 020043陨石的氧化程度和橄榄石含量介于E群和H群之间,故将该陨石划分为E/H过渡型球粒陨石.

  20. Mineral replacements during carbonation of peridotite: implications for carbon dioxide sequestration in ultramafic rocks (United States)

    Beinlich, Andreas; Hövelmann, Jörn; Plümper, Oliver; Austrheim, Hâkon


    In contact with CO2, ultramafic rocks are known to be reactive and eventually form ophicarbonates and listwaenites. Here we present observations from serpentinized peridotite clasts from the Solund Devonian Basin, SW Norway. These clasts show evidence for a stepwise reaction history starting with initial serpentinization and resulting in the formation of carbonates (mainly calcite and dolomite) and quartz. Thus, they represent a natural analogue for CO2 sequestration in ultramafic rocks, which was proposed by the Inter Governmental Panel on Climate Change (IPCC 2005) as one possibility for long-term CO2 storage. In several layers of the basin, the carbonatized ultramafic clasts are important constituents and account for up to 20 vol. % of the basin infill. The investigated clasts show a concentric build-up with green to grey colored cores surrounded by mm to 10 cm thick zones of red to black shades. Textural evidence indicates the following alteration sequence: An early stage is represented by serpentinization of peridotite resulting in a typical mesh texture, with veins of serpentine and Ni-rich hematite surrounding compartments of relict olivine (Fo90). Subsequently, relict olivine breaks down to form an alteration product which is significantly depleted in Mg relative to the precursor olivine. In the more advanced ophicarbonate stage, compartments are filled with calcite, quartz, and talc. In the most advanced stage, quartz, calcite, and hematite dominate and occur together with minor amounts of chromite, talc, and chlorite. The textural evolution is accompanied by a decrease in whole-rock MgO from 40 to 2 wt. % and a CaO increase from 1 to 35 wt. %. All clasts are characterized by high Cr and Ni (1000-4000 and 500-3000 ppm, respectively) revealing their ultramafic origin. Transmission electron microscopy (TEM) observations indicate that the alteration product after olivine is composed of an amorphous material, which is compositionally close to serpentine

  1. Role of Granitic Intrusions and Serpentinization Processes in The Forming of Iron Deposits: Yellice-Dumluca Iron Deposits, Divrigi, Sivas, Turkey (United States)

    Ozturk, Ceyda; Ozcan Kilic, Cumhur; Unlu, Taner


    Divrigi iron ore deposit is one of the most important iron province in Turkey. Genesis of the Divrigi iron deposits is still highly controversial. In Divrigi-Yellice vicinity, no granitic intrusions takes place. Low grade (average 18-20% Fe3O4), 125 million tones magnetite formation in Yellice deposit is found within serpentinites. On the other hand, in Divrigi-Dumluca deposit, granitic intrusions cut the serpentinite units. In the contact between granitic and serpentinized rocks, high grade (%57 Fe), 8 million tones magnetite is substantive. Yellice deposit is consist of characteristic liquid magmatic phase minerals such as chromite, magnetite, pentlandite, pyrotine, chalcopyrite and also pyrite disseminations. Due to serpentinization process, secondary magnetites formed by the iron released from ferromagnesian minerals. Also pyrite and silicate minerals accompanies secondary magnetite occurences. In Dumluca deposit, ore minerals such as magnetite, hematite, pyrite, chalcopyrite, limonite, marcasite, millerite accompanied by characteristic skarn zone paragenesis, diopside, actinolite and quartz. Performed Confocal Raman Spectroscopy studies to determine the serpentine types show that, serpentine minerals of Yellice deposit is mainly antigorite with talc. But however, serpentine minerals of Dumluca deposit is mostly chrysotile. This difference suggests that, serpentinization in Yellice deposit occurred in high temperatures (450-550°C), otherwise in Dumluca deposit, serpentinization occurred in relatively low temperatures (350-400°C). Performed chemical analysis on ore samples shows the distinct differences in major oxides such as Fe2O3, MgO, SiO2, Al2O3, Na2O, Cr2O3 and in trace elements, Rb, Sr, Zr and Ni. Yellice samples have mean 48,79% Fe2O3, 28,24% MgO, 26,46% SiO2, 1,05% Al2O3, 0,02% Na2O, 0.712% Cr2O3 and 44,7 ppm Rb, 6,2 ppm Sr, 1,9 ppm Zr, 2592,9 ppm Ni values whereas Dumluca samples have mean 65,29% Fe2O3, 10,24% MgO, 37,66% SiO2, 4,38% Al2O3, 0,72% Na2

  2. Relaciones entre la zonalidad petrológica y metalogénica de los macizos lerzolíticos de las cadenas alpinas del Mediterráneo Occidental (Cordillera Bético-Rifeña y Kabylias

    Directory of Open Access Journals (Sweden)

    Torres-Ruiz, J.


    Full Text Available Gamet-lherzolite facies, Ariegite and Seiland subfacies of the spinel-lherzolite facies and plagioclase-lherzolite facies have been identified in the Serranía de Ronda, Beni Bousera and Collo lherzolitic massifs. These petrological facies occur in a zonal arrangement: gamet lherzolite are in contact with the overlaying metapelitic sequence and spinel then plagioclase lherzolite occur inwards, representing the innermost zones in the former mantle body. The various occurrences of mineralizations can be classified in two main groups: one of them is essentialIy made up of chromite and Ni arsenides with pyroxene and/or cordierite as gangue minerals; the other consists Qf Fe-Ni-Cu sulfides and graphite, with pyroxene, plagioclase and phlogopite as gangue minerals. In both groups, the ores with the more refractory composition were the first to crystallize in the hotter core of the diapir while those other with a more differentiated composition were formed later within the external zones. The close correlation between petrological and metallogenical roning supports a magmatic origin of the mineralizations related to the petrologic evolution of the mantle bodies. The mineralizing liquids• originated from magmas generated by partial melting of the peridotites. The former migrated outwards, from the internal part of the bodies, during which marked interaction with the enclosing rocks and complex fractionation processes took place under moderate to low pressure conditions.En los macizos lerzolíticos de la Serranía de Ronda, de Beni Bousera y de Collo se han identificado facies de lerzolitas con granate, facies de lerzolitas con espinela (subfacies Ariegita y Seiland y facies de lerzolitas con plagioclasa. Estas facies petrológicas se distribuyen de forma que las lerzolitas con granate se sitúan en contacto con la unidad metapelítica suprayacente, mientras que las lerzolitas con espinela y con plagioclasa lo hacen en posiciones progresivamente m

  3. Electrical characteristics of the hydroxyapatite for biomedical applications; Caracteristicas electricas de la hidroxiapatita para aplicaciones biomedicas

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Buisan N, M.G.; Mendez G, M.M. [Laboratorio de Corrosion, ESFM-IPN, 07738 Mexico D.F. (Mexico)


    The electric characteristics of hydroxyapatite films were studied (HAP) deposited on metallic substrates oxidized naturally. The substrates was made of steel 316L and of titanium. These materials are used in reconstructive surgery for prosthesis and osseous implants. The studies were carried out with the techniques of potentiostatic polarization and faraday impedance. The potentiostatic polarization reveals that the very well-known piezoelectricity of the HAp subsists after the coating processes (it captures thermal and spray-pyrolysis). Its also revealed a semiconductor behavior of the HAp that until now had not been reported. This characteristic is important, by its relationship with the stability of the HAp coating in front of corrosion processes in the alive tissues. The results of the impedance tests were mathematically analyzed starting from the Nyquist diagrams, of Bode and of power. The physical interpretation is presented under the form of equivalent circuits (CE). In the case of the HAp on a steel 316L substrate, the CE is a Rancles-Voigt module that corresponds to the behavior of a dielectric with flights. In the case of the titanium substrate an element of constant phase appears to high frequencies (CPE), in series with the Rancles-Voigt module. The CPE reveals the presence of a rectifier of the metal/SC-n type that only it could be located in the interface among the titanium and its natural oxide (TiO{sub 2}). The absence of the CPE in the case of the steel 316L substrate indicates that the natural oxide (Cr{sub 2}O{sub 3}) it doesn't form with the steel a Schottky diode, possibly because the chromite is as a SC-n degenerate. On the interface Ti/TiO{sub 2} exists results qualitatively identical by other researchers that have worked with the same impedance technique, but applied by humid via (EIS). The CE that have proposed are based on the anodic processes of accretion/dissolution of the film at low pH. This proposal is questioned by our results

  4. An experimental and petrologic investigation of the source regions of lunar magmatism in the context of the primordial differentiation of the moon (United States)

    Elardo, Stephen M.

    The primordial differentiation of the Moon via a global magma ocean has become the paradigm under which all lunar data are interpreted. The success of this model in explaining multiple geochemical, petrologic, and isotopic characteristics lunar geology has led to magma oceans becoming the preferred model for the differentiation of Earth, Mars, Mercury, Vesta, and other large terrestrial bodies. The goal of this work is to combine petrologic analyses of lunar samples with high pressure, high temperature petrologic experiments to place new and detailed constraints the petrogenetic processes that operated during different stages of lunar magmatism, the processes that have acted upon these magmas to obscure their relationship to their mantle source regions, and how those source regions fit into the context of the lunar magma ocean model. This work focuses on two important phases of lunar magmatism: the ancient crust-building plutonic lithologies of the Mg-suite dating to ~4.3 Ga, and the most recent known mare basaltic magmas dating to ~3 Ga. These samples provide insight into the petrogenesis of magmas and interior thermal state when the Moon was a hot, juvenile planet, and also during the last gasps of magmatism from a cooling planet. Chapter 1, focusing on Mg-suite troctolite 76535, presents data on chromite symplectites, olivine-hosted melt inclusions, intercumulus mineral assemblages, and cumulus mineral chemistry to argue that the 76535 was altered by metasomatism by a migrating basaltic melt. This process could effectively raise radioisotope systems above their mineral-specific blocking temperatures and help explain some of the Mg-suite-FAN age overlap. Chapter 2 focuses on lunar meteorites NWA 4734, 032, and LAP 02205, which are 3 of the 5 youngest igneous samples from the Moon. Using geochemical and isotopic data combined with partial melting models, it is shown that these basalts do not have a link to the KREEP reservoir, and a model is presented for low

  5. Some kinetics aspects of chlorine-solids reactions

    Directory of Open Access Journals (Sweden)

    Kanari, N.


    Full Text Available The present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl2+N2 (chlorination, Cl2+O2 (oxychlorination, and Cl2+CO (carbochlorination. Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III oxide was possible only above 500 °C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc.

    Este trabajo describe detalladas investigaciones cinéticas en algunas reacciones seleccionadas de cloro-sólido a través de medidas termogravimétricas. Los sólidos estudiados en este artículo incluyen óxidos químicos puros y sulfuros, así como sus materiales naturales de soporte. Los agentes de cloración empleados son mezclas de gases de Cl2+N2 (cloración, Cl2+O2 (oxicloración y Cl2+O2 (carbocloración. Los resultados se presentan como efecto de varios parámetros en el porcentaje de reacción de estos sólidos con los agentes de cloración. Se ha observado que la reactividad de estos sólidos a través de diferentes agentes de cloración varía ampliamente. Los sulfuros se pudieron

  6. Workshop on Oxygen in the Terrestrial Planets (United States)


    Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe

  7. Comportamento de sinterização do LaCrO3 dopado com Sr e Co Sintering behavior of Sr and Co doped LaCrO3

    Directory of Open Access Journals (Sweden)

    L. F. G. Setz


    Full Text Available O cromito de lantânio (LaCrO3, para ser utilizado como interconector, é fundamental que além da condutividade elétrica adequada, apresente alta densidade, contribuindo deste modo para estanqueidade tanto do hidrogênio presente no ânodo como do oxigênio presente no cátodo das células a combustível de óxido sólido. Utilizando-se LaCrO3 dopado com Sr e Co sintetizado pela rota de síntese por combustão, estudou-se o comportamento de densificação em função do tempo, da temperatura e da concentração dos aditivos. Os pós de cromito de lantânio obtidos foram caracterizados por meio de difração de raios X e método de Rietveld na determinação de parâmetros estruturais e quantificação de fases presentes, microscopia eletrônica de varredura, determinação de área de superfície específica e distribuição de tamanhos de partículas. As peças sinterizadas tiveram suas densidades determinadas pelo método de Arquimedes, análise por microscopia eletrônica de varredura para verificação das microestruturas formadas e de dilatometria na avaliação do coeficiente de expansão térmica. Os resultados mostram que o aumento da temperatura de sinterização tem maior influência no comportamento de densificação do LaCrO3 do que o tempo de tratamento, e o aumento na concentração de dopantes contribui acentuadamente nos processos de sinterização e densificação do material.Lanthanum chromite (LaCrO3 is one of the most adequate materials for use as interconnector in solid oxide fuel cell applications, due to its intrinsic properties, namely its good electrical conductivity and resistance to environment conditions in fuel cell operations. Due to difficulties in sintering, additives are usually added to help in the densification process. In this work, the influence of added cobalt and strontium, time and temperature in the sintering of LaCrO3 obtained by combustion synthesis, was studied. The LaCrO3 powders were characterized

  8. The Effect of Cr content on the Reflectance Properties of Mg-Spinel (United States)

    Williams, K. B.; Jackson, C.; Cheek, L.; Prissel, T. C.; Parman, S. W.; Pieters, C. M.


    Recent analyses of Moon Mineralogy Mapper (M3) data have identified an Mg-spinel lithology previously unobserved on the lunar surface [1,2]. Although some examples of chromite have been identified in M3 spectra for the Sinus Aestuum region [3], most spinel observations thus far appear to be Mg-Al spinel. This study seeks to identify the influence of chromium content on spectral characteristics of synthetic spinel in order to provide a calibration for interpreting spinel composition from M3 observations. Experiments to constrain the Cr and Fe content of the Mg-rich spinel will help characterize the melt involved in its formation, providing valuable information for models of its petrogenesis. Previous studies indicate that spinel displays a 2 μm absorption, corresponding to tetrahedrally coordinated Fe2+. At FeO contents ≥5 wt% [4], synthetic spinel have a 1 μm octahedral absorption due to the availability of Fe2+ to occupy additional sites in the mineral structure [5]. A separate absorption, centered at 0.55 μm, has been attributed to Cr3+. Given the competition between Cr3+ and Al3+ for octahedral crystallographic sites in spinel, the presence of Cr may influence the strength of the 1 μm iron absorption. Fe content and grain size have well-known effects on spectral reflectance band depth, however due to competition for octahedral sites the effect of Cr on reflectance properties within the 0.55-1 μm wavelengths has yet to be clearly identified. Two preliminary experiments successfully produced Mg-spinel containing Cr in octahedral sites, as evidenced by a well-defined 0.55 μm absorption in the spectra. The samples were produced by mixing reagent-grade oxide powders in approximately stoichiometric proportions, and sintering in a horizontal gas mixing furnace at fO2 IW for 72 hours. Sample 1 (mixed with Al2O3 in excess) resulted in spinel with 6% Cr2O3, 6% FeO. Sample 2 (mixed with stoichiometric Al2O3) contained 5% Cr2O3, 5% FeO. Microprobe analyses of this

  9. [The preparation and characterization of fine dusts carried out in the Clinica del Lavoro di Milano in support of experimental studies]. (United States)

    Occella, E; Maddalon, G; Peruzzo, G F; Foà, V


    This paper aims to illustrate the conditions selected at the Clinica del Lavoro of the University of Milan to prepare and analyze a large number of fine dust samples produced over a period of about 50 years, that were initially used for studies within the Clinic performed in its own facilities, and since 1956 were sent to other Italian and overseas laboratories (Luxembourg, UK, Germany, Norway, Sweden, South Korea, USA). The total quantity of material distributed (with maximum size 7-10 microns) was about 2 kg and consisted of the following mineral and artificial compounds: quartz, HF-treated quartz, tridymite, HF-treated tridymite, cristobalite, chromite, anthracite, quartz sand for foundry moulds, sand from the Lybian desert, vitreous silica, pumice, cement, as well small quantities of metallic oxides, organic resins, chrysotile, crocidolite, fibres (vitreous, cotton and polyamidic). About half of the entire quantity of dusts produced consisted of partially HF-treated tridymite. Initially, research on the etiology of silicosis used quartz dust samples, simply sieved or ventilated (consisting of classes finer than 0.04 mm, containing a 15-20% respirable fraction). From 1956 to 1960 the dusts were produced by manual grinding in an agate mortar, below about 10 microns, starting from quartz from Quincinetto (near Ivrea, Province of Turin), containing about 99.5% quartz: particle size and composition were checked using an optical-petrographic technique, with identification of the free and total silica content. Subsequently, the dusts used for biological research were obtained by grinding coarse material with a cast iron pestle and planetary mills, agate and corundum jars. The grinding products were sized by means of centrifugal classification, using the selector developed by N. Zurlo, ensuring control of dust size both optically and by means of wet levigators and hydraulic classifiers (in cooperation with the Institute of Mines of Turin Polytechnic School). After 1990

  10. Serpentinization reactions in peridotite from the Josephine ophiolite: implications for life on Mars (United States)

    Sonzogni, Y.; Treiman, A. H.


    Serpentinization of ocean crustal peridotite, both beneath the seafloor and as ophiolites on land, has been identified as a source of hydrogen that can support microbial activity. The similarity of Mars' crust to terrestrial ocean lithosphere thus suggests that ophiolites may be good analogs to some martian environments where life might have existed and may persist today. However, peridotite-water reactions are poorly understood in detail, and serpentinization is commonly idealized as isovolumetric or isochemical hydration of olivine to form serpentine, brucite, magnetite, and H2 gas. Here, a net-veined serpentinite from the Josephine ophiolite, California, was studied in order to characterize in detail the physical-chemical nature of its serpentinization. The extent of serpentinization in the studied sample is ~60%. Remnants of the original harzburgite include ~30% olivine, ~10% orthopyroxene, and accessory augite and chromite. Two generations of serpentinite veins are present, the distinction between them being in their textures (in SEM imagery); type 1 veins appear striated, while type 2 veins are massive. Both types of veins consist almost entirely of serpentine. Both types contain veins' centers, and as rare isolated grains elsewhere. No brucite has been identified by optical petrography, BSE/SEI/EDS imagery, or by electron microprobe point analyses. The serpentine mineral in both types of vein was identified as lizardite based on its foliate texture (as shown in SEM images), suggesting that serpentinization occurred at Tveins is more magnesian (Mg# 96) than the lizardite in type 2 veins (Mg# 93). Based on the mineral proportions in the serpentinite and original harzburgite and their mineral compositions, this reaction approximates the formation of type 1 serpentine veins: 22.5 Mg1.80Fe0.20SiO4 + 7.5 Mg0.91Fe0.09SiO3 + 31.15 H2O → 15 Mg2.88Fe0.12Si2O5(OH)4 + 1.13 Fe3O4 + 4.13 MgO(aq) + 31.15 H2. This reaction conserves Si and Fe, but is not isovolumetric nor

  11. Effect of chromium powder on physical and chemical properties of magnesia-chrome refractory%金属铬粉对镁铬耐火材料理化性能的影响

    Institute of Scientific and Technical Information of China (English)

    石辛未; 王福明; 熊曙波


    The magnesia-chrome specimens were prepared using magnesite clinker, chromite and chromium powder as raw materials, carboxymethylcellulose sodium as binder, after pressing, firing at 1 600 ℃ for 3 h to determine the effect of chromium powder on the physical and chemical properties of magnesia-chrome refrac-tory. The effect of chromium powder (mass percent were 0%, 0.3%, 0.5%, 1%, 1.5%respectively) on physical and chemical properties of magnesia-chrome refractory were researched, including, porosity rate, flexural strength, compressive strength and thermal shock resistance. The results show that the porosity of samples is obviously reduced and its strength is improved with the addition of 0.3 % chromium powder. However, the properties would be worsened if the addition of chromium powder were too excessive. The strength of the spec-imen added 1.5%chromium powder is obviously decreased with increased porosity. Moreover, the size of pores become larger, owing to the serious expansion of the oxidation reaction of chromium powder. To improve the properties of magnesia-chrome refractory, the addition of chromium powder should be around 0.3%.%为了研究金属铬粉对镁铬耐火材料各理化性能的影响,以镁砂、铬铁矿、金属铬粉为原料,羧甲基纤维素钠为结合剂,经压制并在1600℃下保温3 h烧制成镁铬耐火试样,系统研究金属铬粉的添加量(加入量分别为0%、0.3%、0.5%、1%、1.5%)对镁铬耐火材料气孔率、抗折强度、耐压强度和抗热震性的影响.结果表明,添加0.3%的金属铬粉可明显降低试样的气孔率,使试样致密烧结,强度也显著提高,但对抗热震性影响不明显;随着金属铬粉添加量的增多,各理化性能逐渐恶化,添加1.5%金属铬粉的试样强度明显降低,气孔率升高且气孔孔径明显变大,这是因为金属铬粉发生氧化反应产生严重的膨胀.为了提高镁铬耐火材料的理化性能,

  12. Chromium-rich lawsonite in high-Cr eclogites from the Făgăras Massif (South Carpathians) (United States)

    Negulescu, E.; Săbău, G.


    Lawsonite is a relatively rare phase in natural rocks, because of its thermal decomposition during exhumation, and Cr-bearing lawsonite being restricted to only a few occurrences worldwide. Here we report Cr-lawsonite in eclogites hosted in a medium-grade metamorphic complex. Several high-Cr eclogite lenses occur in the Topolog Complex (Făgăras Massif) of dominantly gneissic-amphibolitic composition. High Cr contents are the result of emerald-green mm-sized nodules containing Cr-rich minerals, embedded in a gray-green matrix of kyanite, clinopyroxene, garnet, amphibole, zoisite, and rutile. Garnets occur as porphyroblasts or in coronas around clinopyroxene aggregates probably replacing former magmatic pyroxene. Relict gabbroic textures (sometimes pegmatoid) and whole rock geochemistry indicate a gabbroic cumulate origin. The REE pattern, displaying a slight positive Eu anomaly and a tea spoon-shaped LREE depletion is also indicative of a cumulate origin, as also noted by Pe Piper & Piper (2002) for the Othrys gabbro (as well as others in the Vourinos and Pindos ophiolitic suites) with the same unusual REE-pattern. The emerald-green Cr-rich nodules are unevenly distributed in the rock, and always enclosed in Cr-rich clinopyroxenes (up to 5.46% Cr2O3) which may exhibit Cr-diffusion haloes towards normal Cr-free matrix pyroxene. The nodules consist of diablastic chromite, rutile and Cr-rich kyanite of up to 15.67 wt% Cr2O3, Cr-bearing epidote, to which Cr-rich staurolite (up to 10.45% Cr2O3; XMg up to 0.68) and Cr-rich lawsonite (up to 9.17% Cr2O3) may exceptionally associate. Cr concentrations in kyanite and lawsonite are, to our knowledge, the highest reported so far. Cr-lawsonite was identified in a single sample, as small single phase inclusions armoured in Cr-kyanite. Equilibrium PT-conditions of 2.6 GPa and 610o C were derived from the garnet-mantled clinopyroxene aggregates using multi-equilibria calculation with the PTGIBBS routine of Brandelik & Massonne

  13. Platinum Group Elements (PGE) geochemistry of komatiites and boninites from Dharwar Craton, India: Implications for mantle melting processes (United States)

    Saha, Abhishek; Manikyamba, C.; Santosh, M.; Ganguly, Sohini; Khelen, Arubam C.; Subramanyam, K. S. V.


    , Os and Ru concentrations range from 0.6 to 2.2 ppb, 0.2 to 0.6 ppb and 1.4 to 2.6 ppb respectively in IPGE. The PGE abundances in Bababudan komatiites were controlled by olivine fractionation whereas that in Gadwal boninites were influenced by fractionation of chromite and sulphides. The Al-undepleted Bababudan komatiites are characterized by low CaO/Al2O3, (Gd/Yb)N, (La/Yb)N, with positive Zr, Hf, Ti anomalies and high Cu/Pd, Pd/Ir ratios at low Pd concentrations suggesting the derivation of parent magma by high degrees (>30%) partial melting of mantle under anhydrous conditions at shallow depth with garnet as a residual phase in the mantle restite. The komatiites are geochemically analogous to Al-undepleted Munro type komatiites and their PGE compositions are consistent with Alexo and Gorgona komatiites. The S-undersaturated character of Bababudan komatiites is attributed to decompression and assimilation of lower crustal materials during magma ascent and emplacement. In contrast, the higher Al2O3/TiO2, lower (Gd/Yb)N, for Gadwal boninites in combination with negative Nb, Zr, Hf, Ti anomalies and lower Cu/Pd at relatively higher Pd/Ir and Pd concentrations reflect high degree melting of refractory mantle wedge under hydrous conditions in an intraoceanic subduction zone setting. Higher Pd/Ir ratios and S-undersaturation of these boninites conform to influx of fluids derived by dehydration of subducted slab resulting into high fluid pressure and metasomatism of mantle wedge.

  14. Conditions of crystallization of the Ural platinum-bearing ultrabasic massifs: evidence from melt inclusions (United States)

    Simonov, Vladimir; Puchkov, Victor; Prikhod'ko, Vladimir; Stupakov, Sergey; Kotlyarov, Alexey


    Conditions of the Ural platinum-bearing ultramafic massifs formation attract attention of numerous researchers. A most important peculiarity of such plutons is their dunite cores, to which commercial Pt deposits are related. There are a different opinions about genesis of these massifs and usual methods not always can solve this question. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization of the Nizhnii Tagil platinum-bearing ulrabasic massif (Ural) was obtained. The comparative analysis of Cr-spinels, containing melt inclusions, has shown essential differences of these minerals from chromites of the ultrabasic ophiolite complexes and of modern oceanic crust. Contents of major chemical components in the heated and quenched melt inclusions are close to those in the picrite and this testifies dunite crystallization from ultrabasic (to 24 wt.% MgO) magma. On the variation diagrams for inclusions in Cr-spinel the following changes of chemical compositions are established: during SiO2 growth there is falling of FeO, MgO, and increase of CaO, Na2O contents. Values of TiO2, Al2O3, K2O and P2O5 remain as a whole constant. Comparing to the data on the melt inclusions in Cr-spinel from the Konder massif, we see that values of the most part of chemical components (SiO2, TiO2, K2O, P2O5) are actually overlapped. At the same time, for the Nizhnii Tagil platinum-bearing massif the big maintenances of FeO and CaO in inclusions are marked. Distinct dependence of the majority of components from the MgO content in inclusions is observed: values TiO2, Al2O3 FeO, CaO and Na2O fall at transition to more magnesia melts. On the peculiarities of distribution of petrochemical characteristics melt inclusions in considered Cr-spinels are co-ordinated with the data on evolution of compositions of melts and rocks of model stratified ultramafic plutons during their crystallization in the magmatic chambers. On the

  15. Batisivite, V8Ti6[Ba(Si2O)]O28, a new mineral species from the derbylite group (United States)

    Reznitsky, L. Z.; Sklyarov, E. V.; Armbruster, T.; Galuskin, E. V.; Ushchapovskaya, Z. F.; Polekhovsky, Yu. S.; Karmanov, N. S.; Kashaev, A. A.; Barash, I. G.


    Batisivite has been found as an accessory mineral in the Cr-V-bearing quartz-diopside metamorphic rocks of the Slyudyanka Complex in the southern Baikal region, Russia. A new mineral was named after the major cations in its ideal formula (Ba, Ti, Si, V). Associated minerals are quartz, Cr-V-bearing diopside and tremolite; calcite; schreyerite; berdesinskiite; ankangite; V-bearing titanite; minerals of the chromite-coulsonite, eskolaite-karelianite, dravite-vanadiumdravite, and chernykhite-roscoelite series; uraninite; Cr-bearing goldmanite; albite; barite; zircon; and unnamed U-Ti-V-Cr phases. Batisivite occurs as anhedral grains up to 0.15-0.20 mm in size, without visible cleavage and parting. The new mineral is brittle, with conchoidal fracture. Observed by the naked eye, the mineral is black and opaque, with a black streak and resinous luster. Batisivite is white in reflected light. The microhardness (VHN) is 1220-1470 kg/mm2 (load is 30 g), the mean value is 1330 kg/mm2. The Mohs hardness is near 7. The calculated density is 4.62 g/cm3. The new mineral is weakly anisotropic and bireflected. The measured values of reflectance are as follows (λ, nm— R {max/'}/ R {min/'}): 440—17.5/17.0; 460—17.3/16.7; 480—17.1/16.5; 500—17.2/16.6; 520—17.3/16.7; 540—17.4/16.8; 560—17.5/16.8; 580—17.6/16.9; 600—17.7/17.1; 620—17.7/17.1; 640—17.8/17.1; 660—17.9/17.2; 680—18.0/17.3; 700—18.1/17.4. Batisivite is triclinic, space group P overline 1 ; the unit-cell dimensions are: a = 7.521(1) Å, b = 7.643(1) Å, c = 9.572(1) Å, α = 110.20°(1), β = 103.34°(1), γ = 98.28°(1), V = 487.14(7) Å3, Z = 1. The strongest reflections in the X-ray powder diffraction pattern [ d, Å ( I, %)( hkl)] are: 3.09(8)(12 overline 2 ); 2.84, 2.85(10)(021, 120); 2.64(8)(21 overline 3 ); 2.12(8)(31 overline 3 ); 1.785(8)(32 overline 4 ), 1.581(10)(24 overline 2 ); 1.432, 1.433(10)(322, 124). The chemical composition (electron microprobe, average of 237 point analyses

  16. Ascertainment and environment of the OIB-type basalts from the Dongbo ophiolite in the western part of Yarlung Zangbo Suture Zone%雅鲁藏布江缝合带西段东波蛇绿岩OIB型玄武岩的厘定及其形成环境

    Institute of Scientific and Technical Information of China (English)

    刘飞; 杨经绥; 陈松永; 梁凤华; 牛晓露; 李兆丽; 连东洋


    The western part of the Yarlung Zangbo Suture Zone (YZSZ) is divided into two sub-belts ; the genesis of the south plays a crucial role in the interpretation of the geological setting,magmatic and tectonic processes of the Neo-Tethyan Ocean.Previous research about the Dongbo ophiolite was poor,due to harsh natural environment and traffic inconvenience.This paper reports the data on petrography and geochemistry of OIB-ty-pe basalts and associated sedimentary rocks in the Dongho ophiolite and discusses their source characteristics and geological significance.Dongbo ophiolite consists of peridotite (including harzburgite,minor Cpx enriched harzburgite and dunite),mafic dikes and submarine volcanic-sendimentary rock sequences,no typical cumulates and pillow lavas.The stable marine volcanic-sedimentary sequences mainly composed of siliceous limestone,red chert,shale interbedded sandstone,basalt and basaltic volcaniclastie rocks.OIB-type basalts are characterized by low SiO2 and MgO,high TiO2,P2O5 and (K2O + Na2O)content,enrichment of Nb,Ta and REE,depletion of Th,K,Pb,Sr.Trace elements and Sr,Nd,Pb isotope data show that these basaltic lavas were derived from 2% to 5% partial melting of garnet spinel lherzolite.Siliceous rocks are of biogenlc origin,and show a close relation to terrigenous component and seamount or island arc basalts.Above evidences indicate that the Dongbo volcanosedimentary sequences have the typical seamount features,and the Dongbo ophiolite probably is related to a plume hotspot.Therefore,it can be considered,the plume hotspot underplating and interacting with the subcontinental lithospheric mantle of the Gondwana northern margin not only promoted opening the Daba-Xiugugabu Tethyan oceanic basin,but also prompted diamonds and other abnormal mantle minerals to be migrated upper mantle and wrapped in peridotite and chromite.%雅鲁藏布江缝合带(YZSZ)西段分为两支,南带蛇绿岩的成因对整个缝合带的性质和构造背景的探

  17. Influence of accumulation of heaps of steel slag on the environment: determination of heavy metals content in the soils

    Directory of Open Access Journals (Sweden)

    Javier Garcia-Guinea


    Full Text Available The presence of high level of heavy metals involves a human healthy risk that could induce chronic diseases. This work reports on the metal contamination due to heaps of steel-slag accumulated during more than 40 years in allotments and industrial areas in the southern part of Madrid (Spain. Several slag and soil samples were collected in an area of 10 km² and characterized by different conventional (XRD and XRF and no so common methods (ESEM, thermoluminescence and EDS-WDS. The analysis reveal the presence of: (i important amounts of Fe (43%, Mg (26%, Cr (1.1%, Mn (4.6%, S (6.5% in the form of Fe-rich slag phases (wustite, magnetite..., Si and Ca-rich phases (larnite, ghelenite..., Cr (chromite, Mn (bustamite and graphite, (ii traces of some other contaminants such as Cr (7700 ppm, Zn (3500 ppm, Ba (3000 ppm, Pb (700 ppm or Cu (500 ppm on pathway soil samples that come from the steel slag, and (iii Co (13 ppm, Pb (78 ppm and V (54 ppm in farmland soil samples. Although the existing heavy metals content is not appropriate for the current use, the extremely high metal contamination of the surrounding areas is more worrying. The properties of the soil farmlands (pH circa 7, 13% of clay, mainly illite, and 1-4% of organic matter content show suitable conditions for the retention of cationic metals, but further studies on the movilization of these elements have to be performed to determine the possibility of severe human health risks. This sort of study can provide useful information for the politicians regarding the appropriate use of the territory to prevent possible health hazard for the population.A presença de altos niveis de metais pesados envolve riscos à saúde humana e pode induzir doenças crônicas. Este trabalho relata a contaminação metálica causada por pilhas de escória siderúrgica acumulada durante mais de 40 anos em áreas industriais na parte sul de Madrid (Espanha. Amostras de escória e solo foram coletadas em uma área de

  18. PGE geochemistry of Jiding ophiolite in Tibet and its constraint on mantle processes

    Institute of Scientific and Technical Information of China (English)

    XIA; Bin


    ., Gorton, M. P., The origin of the fractionation of platinum-group elements in terrestrial magmas. Chem. Geol.. 1985,53: 303-323.[23]Mecher, F G., Thalhammer, T. V., The giant chromite deposits at Kempirsal. Ural: Constraints from trace element (PGE,REE) and isotope data, Mineralium Deposta, 1999, 34: 250-272.[24]Amosse. J., Analytical determination of PGE in geological samples by EAA and ICP-MS, in On Mineralisation Related to Mafic and Ultramafic Magmatism, Orleans, 1993.[25]Gueddari, K., Pioule, M., Amosse, J., Differentiation of platinum-group elements (PGE) and of gold during parting of peridotites in the lherzolitic massif of the Berico-Rifean rifean range (Ronda and Beni Bousera), Chem. Geol., 1996. 134:181-197.[26]Capobianco, C. J., Drake. M. J., Partioning of ruthenium, rhodium, palladium beteewn spinel and silicate melt and implications for platinum group element fractionation trends, Geochim. Cosmochim. Acta. 1990, 54: 869-874.[27]Mairer. W. D., Barnes, S. J., Platinum-group elements in silicate rocks of the lower, critical and main zonest at union section. western Bushveld complex, J. Petrol., 1999.40: 1647-1671.

  19. Metasomatismo en ortoanfibolitas de la Faja máfica-ultramáfica del río de las tunas, Mendoza Metasomatism in orthoamphibolites from the Río de Las Tunas mafic-ultramafic belt, Mendoza

    Directory of Open Access Journals (Sweden)

    M. Florencia Gargiulo


    áticos y la secuencia de reemplazo observada en ellos, sugieren que tales asociaciones se generaron a causa de un proceso metasomático, acontecido en condiciones de bajo grado a una presión menor a 4 kbar, durante los estadios finales del ciclo de metamorfismo regional evidenciado en el área.In this contribution, petro-mineralogical and chemical evidences of metasomatism in orthoamphibolites from the Río de Las Tunas mafic-ultramafic belt in Frontal Cordillera of Mendoza province are provided. These orthoamphibolites integrate the metamorphic basement of the Frontal Cordillera and they belong to the Guarguaráz Metamorphic Complex. These rocks show mineral associations and textural relationships indicating disequilibrium conditions between some of the mineral phases. Hornblendic amphibole crystals show a reaction border with development of clinopyroxene (ferroan dioside; meanwhile the calcicplagioclase is mostly replaced by a fine-grained matrix integrated by the mineral association of garnet-epidotes.l -prehnite-pumpellyite- albite. The amphibole and clinopyroxene crystals are also partially replaced by pumpellyite and/or chlorite, meanwhile the matrix is slightly replaced by muscovite and calcite. Garnet compositions belong to the grossular-andradite series and their average composition is: Alm05Adr53Prp01Sps04Grs36Uv01. Some crystals with Cr2O3 content between 11.69-13.17 wt.% and with a subtle chemical zonation (uvarovitic core: Alm03Adr13Prp00Sps02Grs35Uv47 with more grossularic border: Alm03Adr12 Prp00Sps01Grs44Uv40 occur in relationship with magnetite crystals with up to 20% of the chromite component. Pressure estimations based on the compositional zoning of amphibole crystals gave values between 2.5-4.5 kbar. The observed mineral associations together with the textural and chemical characteristics of these rocks show that this kind of orthoamphibolites is completely different from the classical amphibolites of igneous protoliths outcropping in the study area

  20. Oxygenates vs. synthesis gas

    Energy Technology Data Exchange (ETDEWEB)

    Kamil Klier; Richard G. Herman; Alessandra Beretta; Maria A. Burcham; Qun Sun; Yeping Cai; Biswanath Roy


    Methanol synthesis from H{sub 2}/CO has been carried out at 7.6 MPa over zirconia-supported copper catalysts. Catalysts with nominal compositions of 10/90 mol% and 30/70 mol% Cu/ZrO{sub 2} were used in this study. Additionally, a 3 mol% cesium-doped 10/90 catalyst was prepared to study the effect of doping with heavy alkali, and this promoter greatly increased the methanol productivity. The effects of CO{sub 2} addition, water injection, reaction temperature, and H{sub 2}/C0 ratio have been investigated. Both CO{sub 2} addition to the synthesis gas and cesium doping of the catalyst promoted methanol synthesis, while inhibiting the synthesis of dimethyl ether. Injection of water, however, was found to slightly suppress methanol and dimethyl ether formation while being converted to CO{sub 2} via the water gas shift reaction over these catalysts. There was no clear correlation between copper surface area and catalyst activity. Surface analysis of the tested samples revealed that copper tended to migrate and enrich the catalyst surface. The concept of employing a double-bed reactor with a pronounced temperature gradient to enhance higher alcohol synthesis was explored, and it was found that utilization of a Cs-promoted Cu/ZnO/Cr{sub 2}O{sub 3} catalyst as a first lower temperature bed and a Cs-promoted ZnO/Cr{sub 2}O{sub 3} catalyst as a second high-temperature bed significantly promoted the productivity of 2-methyl-1-propanol (isobutanol) from H{sub 2}/CO synthesis gas mixtures. While the conversion of CO to C{sub 2+} oxygenates over the double-bed configuration was comparable to that observed over the single Cu-based catalyst, major changes in the product distribution occurred by the coupling to the zinc chromite catalyst; that is, the productivity of the C{sub 1}-C{sub 3} alcohols decreased dramatically, and 2-methyl branched alcohols were selectively formed. The desirable methanol/2-methyl oxygenate molar ratios close to 1 were obtained in the present double

  1. Geology, petrology and geochronology of the Lago Grande layered complex: Evidence for a PGE-mineralized magmatic suite in the Carajás Mineral Province, Brazil (United States)

    Teixeira, Antonio Sales; Ferreira Filho, Cesar Fonseca; Giustina, Maria Emilia Schutesky Della; Araújo, Sylvia Maria; da Silva, Heloisa Helena Azevedo Barbosa


    ultramafic lithotypes render Nd model ages between 2.94 and 3.56 Ga, with variably negative ɛNd (T = 2.72 Ga) values (-0.32 to -4.25). The crystallization sequence of the intrusion and the composition of cumulus minerals, together with lithogeochemical and Nd isotopic results, are consistent with an original mantle melt contaminated with older continental crust. The contamination of mafic magma with sialic crust is also consistent with intra-plate rifting models proposed in several studies of the CMP. Lithogeochemical and isotopic data from the Lago Grande Complex may also be interpreted as the result of melting an old lithospheric mantle, and alternative models should not be disregarded. PGE mineralizations occur in chromitites and associated with base metal sulfides in the Lago Grande Complex. Chromitite has the highest PGE content (up to 10 ppm) and is characterized by high Pt/Pd ratio (4.3). Mantle-normalized profile of chromitite is highly enriched in PPGE and similar to those from Middle Group (MG) and Upper Group (UG) chromitites from the Bushveld Complex. Platinum group minerals (PGM) occur mainly at the edge of chromite crystals in the Lago Grande chromitite, consisting of arsenides and sulfo-arsenides. Sulfide-bearing harzburgite samples of the Lago Grande complex have PGE content of up to 1 ppm and low Pt/Pd (0.2-0.3) ratios. The 2722 ± 53 Ma U-Pb zircon age determined in this study for the Lago Grande Complex overlaps with the crystallization age of the Luanga Complex. Previous interpretation that the Lago Grande and Luanga layered intrusions are part of a magmatic suite (i.e., Serra Leste Magmatic Suite) is now reinforced by similar fractionation sequences, comparable petrological evolution and overlapped U-Pb zircon ages. The occurrence of the same styles of PGE mineralization in the Lago Grande and Luanga complexes, together with remarkably similar chondrite-normalized PGE profiles and PGE minerals for chromitites of both complexes, support the concept that

  2. Determination of Major and Minor Components in High-Cr Red Mud by X-ray Fluorescence Spectrometry with Fusion Sample Preparation%熔融制样X射线荧光光谱法测定高铬赤泥中主次量组分

    Institute of Scientific and Technical Information of China (English)

    朱忠平; 曾精华; 王长根; 吕立超


    be analyzed by X-ray Fluorescence Spectrometry (XRF).However,a use of sodium flux and a high dilution ratio are not conducive to sodium and low content elements.In this paper,a method of XRF analysis is developed for the determination of the major and minor components (Cr,Si,Al,Fe,Mg,Ca,Na,K,S,P,Ti,Mn and V)in high-Cr red mud by fused bead preparation with Li2B4O7-LiBO2(67∶33)flux,NH4NO3 oxidizer and saturated LiBr solution parting medium.When the dilution ratio of the melting sample is lower than 24∶1 ,the lower dilution ratio,the more serious is the corrosion on the Pt-Au crucible;the RSD (n=1 0)of the sample preparation method is at a minimum when the dilution ratio is 24∶1;the longer the melting time and the higher the melting temperature,the RSD becomes lower.The optimization conditions of fused bead are obtained when the dilution ratio is 24∶1 ,the melting temperature is 1 1 00℃ and the melting time is 1 5 min.The working curve was established by chromite,bauxite,clay,iron ore standards and manual preparation standard materials.The matrix effect and spectrum line overlap interference were corrected by a fundamental parameter method and standard regression.The results are consistent with certified values and the RSD (n=10)is from 0.3% to 3.9%.Compared with domestic and foreign XRF methods for chromium-containing minerals,this method uses no sodium salt,a fuse piece,conventional sample melting temperature (1 1 00℃),low dilution ratio (24 ∶1 )for sample preparation,and the sampling precision and analysis precision are low.The problem with XRF analysis of high-Cr red mud has been solved by this method,which can be used to analyze Cr,Al, Si and Fe in roasting,concentrates and tailings and other ores processed by sodium.

  3. Evolución metalogenética de las Sierras Pampeanas de Córdoba y sur de Santiago del Estero: Ciclos prepampeano y pampeano Metallogenic evolution of the Sierras Pampeanas of Córdoba and south of Santiago del Estero: Prepampean and Pampean cycles

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    D. Mutti


    éticas más significativas.This hypothesis of metallogenic evolution of the Sierras Pampeaneas of Córdoba and south of Santiago del Estero proposes the existence of five metallogenic stages, two of wich are treated in this paper: stage 1 belongs to the prepampean extensional cycle and is connected with the Neoproterozoic opening and expansion of the proto-Atlantic ocean. During this stage submarine volcanogenic deposits were developed such as Cu-Fe (Zn-Au-Ag-Co in basalts, W (B-F-Zn in impure limestones and dolomites, and Fe in silicoclastic sediments, as well as transition occurrences from them to MVT deposits of Cu (Au-Ag and Pb- Zn (Ag-Cu-Au in impure limestones and dolomites. Chromite magmatic deposits in mantle tectonites and of Fe-Ti in ultramaficmafic rocks in the transition crust-mantle zone are also related to stage 1. Distribution of the Prepampean deposits and their space relationship with the main submarine volcanogenic, SEDEX and MVT áreas in the proto-atlantic ocean are placed on a global reconstruction for Neoproterozoic age. The compressive Pampean - Famatinian cycle comprises two stages. Metallogenic stage 2 (Neoproterozoic - early Cambrian corresponds to the pampean orogenic cycle, during which numerous deformation structures and magmatism were developed. During this stage magmatic-metamorphic occurrences of Fe-Ti in ultramafic and mafic dikes in mantle tectonites, metasomatic occurrences of Fe-Ti in rodingites and Be-Li-U-ETR rich pegmatites were generated, besides transformation events comprising metamorphism, deformation, remobilization and recrystallization occurred in deposits of Cr, Cu-Fe (Zn-Au-Ag- Co, W (B-F-Zn, Cu (Au-Ag, Pb-Zn (Ag-Cu-Au and Fe, which affected their magnetic response.Ore deposits and occurrences included in the above metallogenic stages are distributed in this study in belts related to megastructures activated during the Prepampean and Pampean cycles and the most significant petrogenétic associations are indicated.


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    Lidia V. Solov’eva


    metasomatic phlogopite-amphibole aggregate mainly replace laminar intergrowths of one of pyroxenes and garnet and also develops in the re-crystallized fine-grained rock matrix. This suggests a considerable period of time between the crystallization of rocks of the pyroxenite-peridotite series and the development of phlogopite-amphibole metasomatism.The Phl-Ilm hyperbasites comprise a complex association of parageneses represented by garnet- and garnetless pyroxenites, websterites, olivine websterites, orthopyroxenites, lherzolites and olivinites. A specific feature of this series is high contents of K, Ti and Fe in the rocks and minerals. The content of phlogopite is widely variable, from a few percent to 40–80 %. The content of ilmenite ranges from a few percent to 15 %, rarely to 30–40 %. Mica and ilmenite contents sharply decrease in garnetized xenolithes, where these two minerals, as soon as olivine and pyroxenes are replaced by garnet.Euhedral, subhedral, sideronitic and porphyraceous structures in garnetless xenoliths suggest the primary magmatic genesis of the rocks. In the series of Phl-Ilm hyperbasites, a special type of parageneses is represented by strongly deformed phlogopite-amphibole rocks with newly-formed chromite and relict resorbed ilmenite and clinopyroxene. Phl-Ilm rock series is also characterized by a variety of autometasomatic and metasomatic reaction structures. Garnet and phlogopite develop nearly simultaneously at the sub-solidus stage: garnet develops due to cooling of the primary magmatic rocks, and phlogopite develops under the influence of residual rich in potassium and volatiles fluids – melts. Phlogopite in the rocks of the Phl-Ilm series form porphyraceous plates, late intergranular xenomorphic grains, porphyroblasts of the solidus stage and strongly deformed irregular plates in the phlogopite-amphibole rocks. Amphibole occurs in garnetless parageneses and deformed phlogopite-amphibole rocks in amounts of a few percent and up to 40–50