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Minerals, Volume 5, Issue 2 (June 2015) – 15 articles , Pages 117-366

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1098 KiB  
Article
Notes on the Potential for the Concentration of Rare Earth Elements and Yttrium in Coal Combustion Fly Ash
by James C. Hower, John G. Groppo, Kevin R. Henke, Madison M. Hood, Cortland F. Eble, Rick Q. Honaker, Wencai Zhang and Dali Qian
Minerals 2015, 5(2), 356-366; https://doi.org/10.3390/min5020356 - 23 Jun 2015
Cited by 59 | Viewed by 6461
Abstract
Certain Central Appalachian coals, most notably the Fire Clay coal with a REY-enriched volcanic ash fall tonstein, are known to be enriched in rare earth elements. The Fire Clay tonstein has a greater contribution to the total coal + parting REY than would [...] Read more.
Certain Central Appalachian coals, most notably the Fire Clay coal with a REY-enriched volcanic ash fall tonstein, are known to be enriched in rare earth elements. The Fire Clay tonstein has a greater contribution to the total coal + parting REY than would be inferred from its thickness, accounting for about 20%–35% of the REY in the coal + parting sequence. Underground mining, in particular, might include roof and floor rock and the within-seam partings in the mined product. Beneficiation, necessary to meet utility specifications, will remove some of the REY from the delivered product. In at least one previously published example, even though the tonstein was not present in the Fire Clay coal, the coal was enriched in REY. In this case, as well as mines that ship run-of-mine products to the utility, the shipped REY content should be virtually the same as for the mined coal. At the power plant, however, the delivered coal will be pulverized, generally accompanied by the elimination of some of the harder rock, before it is fired into the boiler. Overall, there are a wide range of variables between the geologic sample at the mine and the power plant, any or all of which could impact the concentration of REY or other critical materials in the coal combustion products. Full article
(This article belongs to the Special Issue Rare Earth: From Exploration to Mining)
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3110 KiB  
Article
Autogenous Tumbling Media Assessment to Clean Weathered Surfaces of Waste-Rock Particles from a Basalt Quarry
by Baran Tufan
Minerals 2015, 5(2), 346-355; https://doi.org/10.3390/min5020346 - 17 Jun 2015
Cited by 1 | Viewed by 7402
Abstract
In this study, the optimum feed composition in autogenous tumbling of basalt waste-rock particles to clean their weathered surface was determined. The weathered surfaces of basalt are generally cut out consequent to extraction of basalt columns in quarry operations. The inefficiently cut out [...] Read more.
In this study, the optimum feed composition in autogenous tumbling of basalt waste-rock particles to clean their weathered surface was determined. The weathered surfaces of basalt are generally cut out consequent to extraction of basalt columns in quarry operations. The inefficiently cut out portions of basalt cause formation of huge quarry waste dumps causing visual pollution on roadsides. Mixtures of different particle size fractions of basalt waste-rock particles were experimented to achieve the optimum feed material composition. The minimum loss of commercially available basalt particles and maximum clear surface was intended. The results were compared with respect to weight loss (%) and reflectance values of used and generated samples. Full article
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1888 KiB  
Article
Use of Iron Powder to Obtain High Yields of Leptothrix Sheaths in Culture
by Tomoko Suzuki, Tatsuki Kunoh, Daisuke Nakatsuka, Hideki Hashimoto, Katsunori Tamura, Hitoshi Kunoh and Jun Takada
Minerals 2015, 5(2), 335-345; https://doi.org/10.3390/min5020335 - 04 Jun 2015
Cited by 9 | Viewed by 5859
Abstract
The Leptothrix species, Fe-oxidizing bacteria, produce an extracellular, microtubular sheath with a complicated organic–inorganic hybrid nature. We have discovered diverse industrial functions for this material, e.g., electrode material for Li-ion batteries, catalyst enhancers, pigments, plant growth promoters, and plant protectants. To consistently obtain [...] Read more.
The Leptothrix species, Fe-oxidizing bacteria, produce an extracellular, microtubular sheath with a complicated organic–inorganic hybrid nature. We have discovered diverse industrial functions for this material, e.g., electrode material for Li-ion batteries, catalyst enhancers, pigments, plant growth promoters, and plant protectants. To consistently obtain material with the qualitative and quantitative stability needed for industrial applications, we focused on developing an optimum culture system for sheath synthesis by the Leptothrix sp. strain OUMS1. Although we have used Fe plates as an Fe source in the liquid silicon-glucose-peptone medium (SGP), the plates do not yield a consistent quality or precise mass, and formation of Fe-encrusted sheath is restricted to a surface of the plates, which limits harvest yield. In this study, to obtain a high yield of sheaths, we cultured OUMS1 in SGP supplemented with Fe powders. The addition of Fe powders to the medium (up to 14.0 g/L) did not adversely influence growth of OUMS1. The final yield of sheaths was about 10-fold greater than in the Fe plate culture. The sheaths also maintained a microtubular form and crystalline texture similar to those produced on Fe plates in SGP. The results proved the usefulness of Fe powder for consistently high yields of Fe-encrusted sheaths of stable quality. Full article
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2414 KiB  
Article
The Challenge of Integrating OHS into Industrial Project Risk Management: Proposal of a Methodological Approach to Guide Future Research (Case of Mining Projects in Quebec, Canada)
by Adel Badri
Minerals 2015, 5(2), 314-334; https://doi.org/10.3390/min5020314 - 01 Jun 2015
Cited by 15 | Viewed by 9076
Abstract
Although risk management tools are put to good use in many industrial sectors, some large projects have been met with numerous problems due to failure to take occupational health and safety (OHS) into consideration. In spite of the high level of risk and [...] Read more.
Although risk management tools are put to good use in many industrial sectors, some large projects have been met with numerous problems due to failure to take occupational health and safety (OHS) into consideration. In spite of the high level of risk and uncertainty associated with many industrial projects, the number of studies of methods for managing all known risks systematically remains small. Under effervescent economic conditions, industries must meet several challenges associated with frequent project start-ups. In highly complex and uncertain environments, rigorous management of risk remains indispensable for avoiding threats to the success of projects. Many businesses seek continually to create and improve integrated approaches to risk management. This article puts into perspective the complexity of the challenge of integrating OHS into industrial project risk management. A conceptual and methodological approach is proposed to guide future research focused on meeting this challenge. The approach is based on applying multi-disciplinary research modes to a complex industrial context in order to identify all scenarios likely to contain threats to humans or the environment. A case study is used to illustrate the potential of the proposed approach for application and its contribution to meeting the challenge of taking OHS into consideration. On-site researchers were able to develop a new approach that helped two mining companies in Quebec (Canada) to achieve successful integration of OHS into expansion projects. Full article
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924 KiB  
Article
Demonstration Plant Equipment Design and Scale-Up from Pilot Plant of a Leaching and Solvent Extraction Process
by Fátima Arroyo, Constantino Fernández-Pereira and Pilar Bermejo
Minerals 2015, 5(2), 298-313; https://doi.org/10.3390/min5020298 - 28 May 2015
Cited by 10 | Viewed by 11209
Abstract
Germanium recovery from coal fly ash by hydrometallurgical procedures was studied at the pilot scale (5 kg of fly ash/h). Results were used to design the equipment of a demonstration-sized plant (200 kg of fly ash/h). The process is based on hydrometallurgical operations: [...] Read more.
Germanium recovery from coal fly ash by hydrometallurgical procedures was studied at the pilot scale (5 kg of fly ash/h). Results were used to design the equipment of a demonstration-sized plant (200 kg of fly ash/h). The process is based on hydrometallurgical operations: firstly a germanium extraction from fly ash by leaching and a consequent Ge separation from the other elements present in the solution by solvent extraction procedures. Based on the experimental results, mass balances and McCabe-Thiele diagrams were applied to determine the number of steps of the solvent extraction stage. Different arrangements have been studied and a countercurrent process with three steps in extraction and six steps in elution was defined. A residence time of 5 min was fixed in both the extraction and elution stages. Volumetric ratios in extraction and stripping were: aqueous phase/organic phase = 5 and organic phase/stripping phase = 5, so a concentration factor of 25 is achieved. Mixers and decanters were completely defined. The maximum extracted and eluted germanium was estimated and a global efficiency of 94% was achieved. The cost-effectiveness of the equipment was estimated using the Lang factors. Full article
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827 KiB  
Review
Testing of Ore Comminution Behavior in the Geometallurgical Context—A Review
by Abdul Mwanga, Jan Rosenkranz and Pertti Lamberg
Minerals 2015, 5(2), 276-297; https://doi.org/10.3390/min5020276 - 19 May 2015
Cited by 34 | Viewed by 13592
Abstract
Comminution tests are an important element in the proper design of ore beneficiation plants. In the past, test work has been conducted for particular representative reference samples. Within geometallurgy the entire ore body is explored in order to further identify the variation within [...] Read more.
Comminution tests are an important element in the proper design of ore beneficiation plants. In the past, test work has been conducted for particular representative reference samples. Within geometallurgy the entire ore body is explored in order to further identify the variation within the resource and to establish spatial geometallurgical domains that show the differential response to mineral processing. Setting up a geometallurgical program for an ore deposit requires extensive test work. Methods for testing the comminution behavior must therefore be more efficient in terms of time and cost but also with respect to sample requirements. The integration of the test method into the geometallurgical modeling framework is also important. This paper provides an overview of standard comminution test methods used for the investigation of ore comminution behavior and evaluates their applicability and potential in the geometallurgical context. Full article
(This article belongs to the Special Issue Advances in Geometallurgy)
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1471 KiB  
Article
Carbon Dioxide Sorption Isotherm Study on Pristine and Acid-Treated Olivine and Its Application in the Vacuum Swing Adsorption Process
by Jiajie Li and Michael Hitch
Minerals 2015, 5(2), 259-275; https://doi.org/10.3390/min5020259 - 04 May 2015
Cited by 31 | Viewed by 6529
Abstract
This paper investigates the potential of pristine and acid-treated olivine as a substrate for CO2 capture using a vacuum swing adsorption (VSA) process from the gas-solid phase. The experiments tested the isotherm of pure CO2 adsorption with partial pressure from 10 [...] Read more.
This paper investigates the potential of pristine and acid-treated olivine as a substrate for CO2 capture using a vacuum swing adsorption (VSA) process from the gas-solid phase. The experiments tested the isotherm of pure CO2 adsorption with partial pressure from 10−5 to 1 bar at ambient temperature. The CO2 adsorption capacity and actual expected working capacity (EWC) curves of pristine and acid-treated olivine were determined. Isotherm studies predict that physisorption dominates chemisorptions at ambient temperatures. The adsorption capacity enhances with the increase of specific surface area, pore volume, and the appearance of Mg complexed on the mineral’s surface. Actual EWC studies showed that acid-treated olivine is an adsorbent choice for the VSA process, due to enhanced CO2 adsorption capacities compared to olivine and the potential for 100% recovery of CO2 during the regeneration process. Pristine olivine is not suitable for the VSA process because of bad regenerability, but it can be used in capturing and sequestering dilute CO2 in process streams. Our research reveals excellent viability for the application of VSA in the area of CO2 capture using pristine olivine and acid-treated olivine. Full article
(This article belongs to the Special Issue CO2 Sequestration by Mineral Carbonation: Challenges and Advances)
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1207 KiB  
Article
Study on the Activation of Scheelite and Wolframite by Lead Nitrate
by Gang Zhao, Shuai Wang and Hong Zhong
Minerals 2015, 5(2), 247-258; https://doi.org/10.3390/min5020247 - 16 Apr 2015
Cited by 63 | Viewed by 6635
Abstract
The activation of scheelite and wolframite by lead nitrate with benzohydroxamic acid (BHA) as collector was investigated by means of micro flotation test, zeta potential measurement, X-ray photoelectron spectroscopy (XPS) analyses and density functional theory (DFT) calculation. The flotation results confirmed that the [...] Read more.
The activation of scheelite and wolframite by lead nitrate with benzohydroxamic acid (BHA) as collector was investigated by means of micro flotation test, zeta potential measurement, X-ray photoelectron spectroscopy (XPS) analyses and density functional theory (DFT) calculation. The flotation results confirmed that the addition of lead nitrate can markedly enhance the recovery of scheelite and wolframite. In the zeta potential curves obvious positive shifts were observed with the presence of lead nitrate. Lead was detected on mineral surface in microscopic analysis and the survey XP spectra. Both the electrokinetic study and XPS analyses indicated that lead ion can be adsorbed onto mineral surface. In DFT calculation, the coordination model of BHA with metal hydroxyl ions (Ca(OH)+, Mn(OH)+, Fe(OH)+ and Pb(OH)+) was simulated and their binding energy were also calculated. The calculated results revealed that the binding ability of BHA and Pb(OH)+ is the strongest, indicating that BHA can preferentially coordinate with Pb ion compared with Ca, Mn and Fe ions. Full article
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6466 KiB  
Article
Approaches to the Low Grade Metamorphic History of the Karakaya Complex by Chlorite Mineralogy and Geochemistry
by Sema Tetiker, Hüseyin Yalçın and Ömer Bozkaya
Minerals 2015, 5(2), 221-246; https://doi.org/10.3390/min5020221 - 16 Apr 2015
Cited by 7 | Viewed by 8079
Abstract
In this study, chlorite is used to investigate the diagenetic-metamorphic evolution and accurate geological history of the different units belonging to the Karakaya complex, Turkey. Primary and secondary chlorite minerals in the very low-grade metamorphic rocks display interference colors of blue and brown [...] Read more.
In this study, chlorite is used to investigate the diagenetic-metamorphic evolution and accurate geological history of the different units belonging to the Karakaya complex, Turkey. Primary and secondary chlorite minerals in the very low-grade metamorphic rocks display interference colors of blue and brown and an appearance of optical isotropy. Chlorites are present in the matrix, pores, and/or rocks units as platy/flaky and partly radial forms. X-ray diffraction (XRD) data indicate that Mg-Fe chlorites with entirely IIb polytype (trioctahedral) exhibit a variety of compositions, such as brunsvigite-diabantite-chamosite. The major element contents and structural formulas of chlorite also suggest these were derived from both felsic and metabasic source rocks. Trace and rare earth element (REE) concentrations of chlorites increase with increasing grade of metamorphism, and these geochemical changes can be related to the tectonic structures, formational mechanics, and environments present during their generation. Full article
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719 KiB  
Article
Study on the Optimization of the Industrial Structure in a Mining Economic Region: Taking Carbon Emissions as a Restriction
by Li Li, Yalin Lei, Lianrong Zhao and Xianhai Li
Minerals 2015, 5(2), 203-220; https://doi.org/10.3390/min5020203 - 14 Apr 2015
Cited by 19 | Viewed by 5082
Abstract
In the first decade of the 21st century, as a typical coal province and mining economic region, Shanxi province made a great contribution to the national economic construction and reform. At the same time, coal mining has caused serious damage to the ecological [...] Read more.
In the first decade of the 21st century, as a typical coal province and mining economic region, Shanxi province made a great contribution to the national economic construction and reform. At the same time, coal mining has caused serious damage to the ecological environment, excessive use of resources, the deterioration of the ecological environment and a decline in the sustainable development capacity. Overreliance on a resource-based economy leads to problems such as a poorly developed economy and a single industrial structure. In this context, Shanxi province has to take actions to transform its industrial structure into a low-carbon development model as soon as possible. This paper measures the values of the consumption coefficients of capital investments, electric power and CO2 emissions by establishing a Grey Model (1, 1) using the data from 2007 to 2011 and designing the optimization scheme of the three industrial structures from 2015 to 2020 by establishing a grey dynamic linear programming model for Shanxi province. The results show that the industrial structure in Shanxi province needs to be improved. It is revealed that the proportion of three industries in Shanxi province should change from 6:46:48 in 2015 to 6:41:54 in 2020. At the same time, among the seven largest sectors in terms of carbon emissions in the secondary industry, Shanxi government may continue to promote the development of the coal-bed methane and the coal chemical industry in the coal industry, while the other six sectors should be limited. Full article
1060 KiB  
Article
Use of Phosphate Solubilizing Bacteria to Leach Rare Earth Elements from Monazite-Bearing Ore
by Doyun Shin, Jiwoong Kim, Byung-su Kim, Jinki Jeong and Jae-chun Lee
Minerals 2015, 5(2), 189-202; https://doi.org/10.3390/min5020189 - 02 Apr 2015
Cited by 72 | Viewed by 10214
Abstract
In the present study, the feasibility to use phosphate solubilizing bacteria (PSB) to develop a biological leaching process of rare earth elements (REE) from monazite-bearing ore was determined. To predict the REE leaching capacity of bacteria, the phosphate solubilizing abilities of 10 species [...] Read more.
In the present study, the feasibility to use phosphate solubilizing bacteria (PSB) to develop a biological leaching process of rare earth elements (REE) from monazite-bearing ore was determined. To predict the REE leaching capacity of bacteria, the phosphate solubilizing abilities of 10 species of PSB were determined by halo zone formation on Reyes minimal agar media supplemented with bromo cresol green together with a phosphate solubilization test in Reyes minimal liquid media as the screening studies. Calcium phosphate was used as a model mineral phosphate. Among the test PSB strains, Pseudomonas fluorescens, P. putida, P. rhizosphaerae, Mesorhizobium ciceri, Bacillus megaterium, and Acetobacter aceti formed halo zones, with the zone of A. aceti being the widest. In the phosphate solubilization test in liquid media, Azospirillum lipoferum, P. rhizosphaerae, B. megaterium, and A. aceti caused the leaching of 6.4%, 6.9%, 7.5%, and 32.5% of calcium, respectively. When PSB were used to leach REE from monazite-bearing ore, ~5.7 mg/L of cerium (0.13% of leaching efficiency) and ~2.8 mg/L of lanthanum (0.11%) were leached by A. aceti, and Azospirillum brasilense, A. lipoferum, P. rhizosphaerae and M. ciceri leached 0.5–1 mg/L of both cerium and lanthanum (0.005%–0.01%), as measured by concentrations in the leaching liquor. These results indicate that determination of halo zone formation was found as a useful method to select high-capacity bacteria in REE leaching. However, as the leaching efficiency determined in our experiments was low, even in the presence of A. aceti, further studies are now underway to enhance leaching efficiency by selecting other microorganisms based on halo zone formation. Full article
(This article belongs to the Special Issue Advances in Biohydrometallurgy)
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4018 KiB  
Article
Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling
by Hassan Fayed and Saad Ragab
Minerals 2015, 5(2), 164-188; https://doi.org/10.3390/min5020164 - 30 Mar 2015
Cited by 19 | Viewed by 7389
Abstract
A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as [...] Read more.
A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines. Full article
(This article belongs to the Special Issue Flotation Technologies for the Future)
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3455 KiB  
Article
Flotation Bubble Delineation Based on Harris Corner Detection and Local Gray Value Minima
by Weixing Wang and Liangqin Chen
Minerals 2015, 5(2), 142-163; https://doi.org/10.3390/min5020142 - 30 Mar 2015
Cited by 15 | Viewed by 7358
Abstract
Froth image segmentation is an important and basic part in an online froth monitoring system in mineral processing. The fast and accurate bubble delineation in a froth image is significant for the subsequent froth surface characterization. This paper proposes a froth image segmentation [...] Read more.
Froth image segmentation is an important and basic part in an online froth monitoring system in mineral processing. The fast and accurate bubble delineation in a froth image is significant for the subsequent froth surface characterization. This paper proposes a froth image segmentation method combining image classification and image segmentation. In the method, an improved Harris corner detection algorithm is applied to classify froth images first. Then, for each class, the images are segmented by automatically choosing the corresponding parameters for identifying bubble edge points through extracting the local gray value minima. Finally, on the basis of the edge points, the bubbles are delineated by using a number of post-processing functions. Compared with the widely used Watershed algorithm and others for a number of lead zinc froth images in a flotation plant, the new method (algorithm) can alleviate the over-segmentation problem effectively. The experimental results show that the new method can produce good bubble delineation results automatically. In addition, its processing speed can also meet the online measurement requirements. Full article
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2377 KiB  
Article
Evaluation of Uranium Concentration in Soil Samples of Central Jordan
by Ned Xoubi
Minerals 2015, 5(2), 133-141; https://doi.org/10.3390/min5020133 - 25 Mar 2015
Cited by 14 | Viewed by 8814
Abstract
Naturally occurring radionuclides such as uranium, thorium and their decay products (226Ra, 222Rn) are present in a number of geological settings in Jordan. Motivated by the existence of uranium anomalies ‎coupled with its lack of conventional ‎‎energy ‎‎resources, Jordan decided [...] Read more.
Naturally occurring radionuclides such as uranium, thorium and their decay products (226Ra, 222Rn) are present in a number of geological settings in Jordan. Motivated by the existence of uranium anomalies ‎coupled with its lack of conventional ‎‎energy ‎‎resources, Jordan decided that the development of ‎this indigenes ‎resource (uranium) is the first step in introducing nuclear power as part of its energy mix. Uranium deposits in Central Jordan were perceived not only as a secured resource that will ‎fulfill Jordan’s energy needs, but also as an economic asset that will ‎finance Jordan’s nuclear program. The average uranium concentration of 236 soil samples using ICP-Mass (inductively coupled plasma mass spectrometry) was found to be 109 parts per million (ppm). Results analysis revealed a wide range of 1066 ppm for uranium concentration, and a median of 41 ppm uranium. The measurements frequency distribution indicates that 72% of samples measured had a uranium content of less than 100 ppm, a concentration that characterizes overburden and tailings quality, rather than minable reserves. This paper presents and evaluates the concentration of uranium in central Jordan, being the most promising area with the highest radioactive anomalies in Jordan. Full article
(This article belongs to the Special Issue Uranium Minerals: From Resources to Environmental Impact)
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14591 KiB  
Article
Distribution and Substitution Mechanism of Ge in a Ge-(Fe)-Bearing Sphalerite
by Nigel J. Cook, Barbara Etschmann, Cristiana L. Ciobanu, Kalotina Geraki, Daryl L. Howard, Timothy Williams, Nick Rae, Allan Pring, Guorong Chen, Bernt Johannessen and Joël Brugger
Minerals 2015, 5(2), 117-132; https://doi.org/10.3390/min5020117 - 24 Mar 2015
Cited by 100 | Viewed by 8996
Abstract
The distribution and substitution mechanism of Ge in the Ge-rich sphalerite from the Tres Marias Zn deposit, Mexico, was studied using a combination of techniques at μm- to atomic scales. Trace element mapping by Laser Ablation Inductively Coupled Mass Spectrometry shows that Ge [...] Read more.
The distribution and substitution mechanism of Ge in the Ge-rich sphalerite from the Tres Marias Zn deposit, Mexico, was studied using a combination of techniques at μm- to atomic scales. Trace element mapping by Laser Ablation Inductively Coupled Mass Spectrometry shows that Ge is enriched in the same bands as Fe, and that Ge-rich sphalerite also contains measurable levels of several other minor elements, including As, Pb and Tl. Micron- to nanoscale heterogeneity in the sample, both textural and compositional, is revealed by investigation using Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) combined with Synchrotron X-ray Fluorescence mapping and High-Resolution Transmission Electron Microscopy imaging of FIB-prepared samples. Results show that Ge is preferentially incorporated within Fe-rich sphalerite with textural complexity finer than that of the microbeam used for the X-ray Absorption Near Edge Structure (XANES) measurements. Such heterogeneity, expressed as intergrowths between 3C sphalerite and 2H wurtzite on zones, could be the result of either a primary growth process, or alternatively, polystage crystallization, in which early Fe-Ge-rich sphalerite is partially replaced by Fe-Ge-poor wurtzite. FIB-SEM imaging shows evidence for replacement supporting the latter. Transformation of sphalerite into wurtzite is promoted by (111)* twinning or lattice-scale defects, leading to a heterogeneous ZnS sample, in which the dominant component, sphalerite, can host up to ~20% wurtzite. Ge K-edge XANES spectra for this sphalerite are identical to those of the germanite and argyrodite standards and the synthetic chalcogenide glasses GeS2 and GeSe2, indicating the Ge formally exists in the tetravalent form in this sphalerite. Fe K-edge XANES spectra for the same sample indicate that Fe is present mainly as Fe2+, and Cu K-edge XANES spectra are characteristic for Cu+. Since there is no evidence for coupled substitution involving a monovalent element, we propose that Ge4+ substitutes for (Zn2+, Fe2+) with vacancies in the structure to compensate for charge balance. This study shows the utility of synchrotron radiation combined with electron beam micro-analysis in investigating low-level concentrations of minor metals in common sulfides. Full article
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