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Volume 6
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Minerals, Volume 6, Issue 4 (December 2016) – 35 articles

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1872 KiB  
Article
Cemented Backfilling Technology of Paste-Like Based on Aeolian Sand and Tailings
by Qinli Zhang, Qiusong Chen and Xinmin Wang
Minerals 2016, 6(4), 132; https://doi.org/10.3390/min6040132 - 16 Dec 2016
Cited by 29 | Viewed by 4441
Abstract
Aeolian sand, tailings, and #32.5 Portland cement were used to produce backfilling aggregate, and physicochemical evaluations and proportioning tests were conducted. It is revealed that a mixture of aeolian sand and tailings can be used as a backfilling aggregate for the complementarities [...] Read more.
Aeolian sand, tailings, and #32.5 Portland cement were used to produce backfilling aggregate, and physicochemical evaluations and proportioning tests were conducted. It is revealed that a mixture of aeolian sand and tailings can be used as a backfilling aggregate for the complementarities of their physicochemical properties; e.g., high Al2O3 content in the aeolian sand and CaO content in the tailings, coarse particles of aeolian sand and fine particles of tailings, etc. In addition, the optimal backfilling aggregate was shown to have a mass fraction of 72%–74%, a cement–sand ratio of 1:8, and an aeolian sand proportion of 25%. Furthermore, viscometer tests were used to analyze the rheological characteristics, and the slurry in these optimized proportions exhibited shear thinning phenomena with an initial yield stress, which belongs to paste-like—a cemented backfilling slurry with a higher mass fraction than a two-phase flow and better flowability than a paste slurry. Finally, the application of this backfilling technology shows that it can not only realize safe mining, but also bring huge economic benefits, and has some constructive guidance for environmental protection. Full article
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Figure 1
<p>Compressive strength of specimens cured for 28 days when the cement–sand ratio is 1:8, with varying mass fraction and aeolian sand proportion.</p> Full article ">Figure 2
<p>Slump test: (<b>a</b>) presents specimen (mass fraction of 74%) with slump values of 260 mm, which can realize self-flowing; (<b>b</b>) shows specimen (mass fraction of 76%) with slump values of 180 mm, which is too poor to realize self-flowing [<a href="#B18-minerals-06-00132" class="html-bibr">18</a>].</p> Full article ">Figure 3
<p>Compressive strength of specimens cured for different times with varying cement–sand ratio, where aeolian sand proportion is 25% and mass fraction is 72% cured for 28 days, when the cement–sand ratio is 1:8.</p> Full article ">Figure 4
<p>Typical stress–strain curves of specimens for different curing times where the cement–sand ratio is 1:12 and the aeolian sand proportion is 25%.</p> Full article ">Figure 5
<p>(<b>a</b>) SEM image of a specimen with aeolian sand proportion of 0%; (<b>b</b>) SEM image of a specimen with aeolian sand proportion of 25%; and (<b>c</b>) The element composition analysis of the area marked in (<b>b</b>) by energy dispersive spectroscopy (EDS).</p> Full article ">Figure 6
<p>Shear stress and viscosity curves with stress rate of specimens.</p> Full article ">Figure 7
<p>Backfilling craft process: 1—deep-cone thickener; 2—nuclear densimeter; 3—cement storehouse; 4—star feeder; 5—electronic steelyard; 6—spiral feeder; 7—high-seated field pond; 8—electromagnetic flow meter 1; 9—horizontal sand silo; 10—electronic rake; 11—material-stabilization silo; 12—vibrated feeder; 13—belt conveyer; 14—belt weigher; 15—hopper; 16—mixing tank; 17—densimeter; 18—electromagnetic flow meter 2; 19—pipeline; 20—stope (goaf).</p> Full article ">
11968 KiB  
Article
Mineralogical Composition of Urinary Stones and Their Frequency in Patients: Relationship to Gender and Age
by Behnam Keshavarzi, Nasrin Yavar Ashayeri, Farid Moore, Dariush Irani, Sina Asadi, Alireza Zarasvandi and Mehrdad Salari
Minerals 2016, 6(4), 131; https://doi.org/10.3390/min6040131 - 14 Dec 2016
Cited by 14 | Viewed by 11828
Abstract
This investigation reports the mineralogy and possible pathological significance of urinary stones removed from patients in Fars province, Iran. X-ray diffraction (XRD), scanning electron microscopy (SEM) and polarizing microscope (PM) techniques were used to investigate the mineralogical compositions of urinary stones. The identified [...] Read more.
This investigation reports the mineralogy and possible pathological significance of urinary stones removed from patients in Fars province, Iran. X-ray diffraction (XRD), scanning electron microscopy (SEM) and polarizing microscope (PM) techniques were used to investigate the mineralogical compositions of urinary stones. The identified mineral components include whewellite, weddellite, hydroxyapatite, uricite and cystine. These techniques revealed that the whewellite and uricite were the most common mineral phases. Platy-like/monoclinic whewellite, prismatic/monoclinic uric acid and hexagonal cystine crystals were revealed by SEM. Biominerals (calcium carbonate) and quartz were also identified in PM images. Of the variables determining the type of precipitated minerals, the effects of pH on depositional conditions proved to be the most apparent parameter, as shown by occurrences and relationships among the studied minerals. Our results revealed the importance of detailed knowledge of mineralogical composition in assessing the effects of age and sex. The highest incidence of urinary stones was observed in the 40–60 age group. Calcium oxalate and uric acid stones are more frequent in men than women. Finally, the study concluded that knowledge of the mineralogical composition of urinary stones is important as it helps the scientific community to explain the chemistry and the etiology of the calculi in the urinary system. Full article
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<p>Rietveld graph of sample MB-15. Goodness-of-fit indicator as well as R-factors were: X<sup>2</sup> = 1.56, R<sub>wp</sub> = 20.46%, and R<sub>exp</sub> = 16.33%.</p> Full article ">Figure 2
<p>Rietveld graph of sample FPo-2. Goodness-of-fit indicator as well as R-factors were: X<sup>2</sup> = 1.88, R<sub>wp</sub> = 17.95%, and R<sub>exp</sub> = 13.70%.</p> Full article ">Figure 3
<p>Rietveld graph of sample MP-6. Goodness-of-fit indicator as well as R-factors were: X<sup>2</sup> = 1.99, R<sub>wp</sub> = 20.80%, and R<sub>exp</sub> = 14.71%.</p> Full article ">Figure 4
<p>Rietveld graph of sample MK-6. Goodness-of-fit indicator as well as R-factors were: X<sup>2</sup> = 2.06, R<sub>wp</sub> = 22.26%, and R<sub>exp</sub> = 15.48%.</p> Full article ">Figure 5
<p>Macroscopic images of some the urinary stones analyzed in this study: renal stone with composition of cystine (<b>a</b>); renal stone with major constituents of whewellite and uricite in minor constituents (<b>b</b>); and bladder stone with uricite mineral (<b>c</b>).</p> Full article ">Figure 6
<p>Platy-like calcium oxalate (CO) crystal (<b>a</b>); hexagonal cystine (Cys) crystal (<b>b</b>); and prismatic uric acid (UA) crystal (<b>c</b>) at scanning electron microscopy view.</p> Full article ">Figure 7
<p>Polarizing microscopic images of calcium oxalate stones: (<b>a</b>) laminar texture in the whewellite mineral; (<b>b</b>) Concentric and radiate laminations of whewellite mineral of calcium oxalate stone around invisible nuclei; (<b>c</b>) Concentric laminations around a dark brown amorphous core in calcium oxalate stones.</p> Full article ">Figure 8
<p>Polarizing microscopic images of uric acid stone (UA).</p> Full article ">Figure 9
<p>Radial texture of whewellite mineral (Whe) with high content of iron oxide (FeO).</p> Full article ">Figure 10
<p>Polarizing microscopic image of mixed kidney stone: uric acid in center and whewellite in rim of stone.</p> Full article ">Figure 11
<p>Polarizing microscopic images of biominerals in the uric acid stone: (<b>a</b>) fibrous aragonite (Arg); (<b>b</b>) rhombus aragonite.</p> Full article ">Figure 12
<p>Polarizing microscopic images of amorphous vaterite (Vat) biomineral (<b>a</b>); and amorphous Quartz (Si) in calcium oxalate stone (<b>b</b>) in sample MPo-3.</p> Full article ">
8554 KiB  
Article
Pressure–Temperature–Fluid Constraints for the Poona Emerald Deposits, Western Australia: Fluid Inclusion and Stable Isotope Studies
by Dan Marshall, Peter J. Downes, Sarah Ellis, Robert Greene, Lara Loughrey and Peter Jones
Minerals 2016, 6(4), 130; https://doi.org/10.3390/min6040130 - 9 Dec 2016
Cited by 28 | Viewed by 6198
Abstract
Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of [...] Read more.
Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of 335–525 °C and pressures ranging from 70 to 400 MPa. The large range in pressure and temperature likely reflects some post entrapment changes and re-equilibration of oxygen isotopes. Secondary emerald-hosted fluid inclusions indicate subsequent emerald precipitation from higher salinity fluids. Likewise, the δ18O-δD of channel fluids extracted from Poona emerald is consistent with multiple origins yielding both igneous and metamorphic signatures. The combined multiple generations of emerald precipitation, different fluid compositions, and the presence of both metamorphic and igneous fluids trapped in emerald, likely indicate a protracted history of emerald precipitation at Poona conforming to both an igneous and a metamorphic origin at various times during regional lower amphibolite to greenschist facies metamorphism over the period ~2710–2660 Ma. Full article
(This article belongs to the Special Issue Fluid Inclusions: Study Methods, Applications and Case Histories)
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<p>Index map (inset) and interpreted geological map of the Poona mineral field, Yilgarn Craton, Western Australia showing specimen localities (modified after [<a href="#B4-minerals-06-00130" class="html-bibr">4</a>,<a href="#B12-minerals-06-00130" class="html-bibr">12</a>], YT—Youanmi Terrane, MD—Murchison Domain, SCD—Southern Cross Domain, EGS—Eastern Goldfields Superterrane).</p> Full article ">Figure 2
<p>Emerald in pegmatite from the Poona region. Quartz (qtz), altered potassic feldspar (ksp) and muscovite (mu) are in textural equilibrium with the emerald (brl). The emerald is clear in plane polarized light, but shown here under crossed polars exhibits growth zoning. Sample MDC1811.</p> Full article ">Figure 3
<p>Electron microprobe data for FeO, Cr<sub>2</sub>O<sub>3</sub>, and V<sub>2</sub>O<sub>3</sub> superimposed on a cathodoluminescence image of the emerald shown in <a href="#minerals-06-00130-f002" class="html-fig">Figure 2</a>. The emerald displays multiple growth zones including a partially resorbed core. The outer zones are dark in CL and correspond to enriched concentrations of FeO, Cr<sub>2</sub>O<sub>3</sub>, and V<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 4
<p>Ternary FeO–Cr<sub>2</sub>O<sub>3</sub>–V<sub>2</sub>O<sub>3</sub> (wt %) plots of Poona emerald compositions (dark and light green hexagons, corresponding to emerald and green beryl respectively) superimposed on the worldwide emerald compositions from literature data compiled in [<a href="#B6-minerals-06-00130" class="html-bibr">6</a>,<a href="#B7-minerals-06-00130" class="html-bibr">7</a>,<a href="#B25-minerals-06-00130" class="html-bibr">25</a>,<a href="#B27-minerals-06-00130" class="html-bibr">27</a>]. Data are normalized from wt % microprobe analyses (<a href="#minerals-06-00130-t001" class="html-table">Table 1</a>), with Fe data reported as FeO. Other Australian emerald data are from Menzies and Emmaville-Torrington.</p> Full article ">Figure 5
<p>Al versus the sum of other Y-site cations, in atoms per formula unit. The Poona emerald compositions are superimposed on worldwide emerald data compiled from the literature in [<a href="#B6-minerals-06-00130" class="html-bibr">6</a>,<a href="#B7-minerals-06-00130" class="html-bibr">7</a>,<a href="#B25-minerals-06-00130" class="html-bibr">25</a>,<a href="#B27-minerals-06-00130" class="html-bibr">27</a>]. The dark and light green hexagons correspond to emerald vs. beryl compositions in the Poona samples.</p> Full article ">Figure 6
<p>Mg + Mn + Fe versus monovalent channel-site cations, in atoms per formula unit. The Poona compositions (dark and light green hexagons) are superimposed on worldwide emerald data compiled from the literature in [<a href="#B6-minerals-06-00130" class="html-bibr">6</a>,<a href="#B7-minerals-06-00130" class="html-bibr">7</a>,<a href="#B25-minerals-06-00130" class="html-bibr">25</a>,<a href="#B27-minerals-06-00130" class="html-bibr">27</a>].</p> Full article ">Figure 7
<p>Channel H<sub>2</sub>O versus emerald Na<sub>2</sub>O contents for a variety of emerald deposits. Comparison to the new fit (Equation (3)) is shown in black signature relative to the previously derived equations of [<a href="#B6-minerals-06-00130" class="html-bibr">6</a>,<a href="#B26-minerals-06-00130" class="html-bibr">26</a>] shown in grey solid and dashed signatures respectively.</p> Full article ">Figure 8
<p>Photomicrograph of an assemblage of primary two-phase fluid inclusions occurring within growth zones in beryl (<a href="#minerals-06-00130-f002" class="html-fig">Figure 2</a>). The fluid inclusions are oriented with their long axes parallel to the c-axis of the host crystal, as is typical of primary fluid inclusions in emerald [<a href="#B7-minerals-06-00130" class="html-bibr">7</a>,<a href="#B25-minerals-06-00130" class="html-bibr">25</a>]. Photomicrograph taken in plane polarised light.</p> Full article ">Figure 9
<p>Two-dimensional box and whisker plot for two-phase liquid-rich fluid primary and secondary fluid inclusions from Poona emerald. Total homogenisation and ice melting temperatures are shown on the ordinate and abscissa axes respectively. The number of fluid inclusions measured for the primary assemblages are 4, 4, 5, 4, 5, 5, and 2 respectively. All secondary assemblages had four inclusions per assemblage. Data ranges less than the Q1 and Q3 conjugates are not shown.</p> Full article ">Figure 10
<p>Channel δD H<sub>2</sub>O versus δ<sup>18</sup>O for the Poona emerald (green rectangles; <a href="#minerals-06-00130-t004" class="html-table">Table 4</a>) superimposed on data from a number of world localities compiled from [<a href="#B6-minerals-06-00130" class="html-bibr">6</a>,<a href="#B28-minerals-06-00130" class="html-bibr">28</a>]. The isotopic compositional fields are from [<a href="#B42-minerals-06-00130" class="html-bibr">42</a>], including the extended (Cornubian) magmatic water box (grey). MWL = Meteoric Water Line, SMOW = standard mean ocean water.</p> Full article ">Figure 11
<p>Pressure–temperature diagram showing all of the individual FI isochores for the FIT-1, 2, and three Poona fluid inclusions hosted in emerald. The pressure–temperature constraints from the stable isotope thermometry combined with all of the isochores and the FIA displaying the least amount of post-entrapment-changes (<a href="#minerals-06-00130-t003" class="html-table">Table 3</a>, FIT-1, FIA-2) are shown in light and dark grey shaded areas respectively. The individual isochores are labelled with the first digit representing the FIT, the second digit representing the FIA, and the fourth and/or third digits representing the individual FI number from <a href="#minerals-06-00130-t003" class="html-table">Table 3</a>. The liquid–vapour curve for a 12 wt % NaCl–H<sub>2</sub>O fluid, derived from the data of [<a href="#B36-minerals-06-00130" class="html-bibr">36</a>], is shown in grey with grey text.</p> Full article ">
2505 KiB  
Article
Adsorption Behavior of Cd2+ and Zn2+ onto Natural Egyptian Bentonitic Clay
by Nagwa Burham and Mahmoud Sayed
Minerals 2016, 6(4), 129; https://doi.org/10.3390/min6040129 - 8 Dec 2016
Cited by 41 | Viewed by 5414
Abstract
In the present work, an Egyptian bentonitic clay sample has been structurally characterized using different techniques such as XRD, IR, SEM, and EDX analyses then evaluated as a sorbent for heavy metal ions removal. The characterization results showed that the clay sample is [...] Read more.
In the present work, an Egyptian bentonitic clay sample has been structurally characterized using different techniques such as XRD, IR, SEM, and EDX analyses then evaluated as a sorbent for heavy metal ions removal. The characterization results showed that the clay sample is in the bentonite form with montmorillonite and kaolinite as mixed-clay minerals. The specific surface area (SSA) and cation exchange capacity (CEC) were determined using methylene blue test and they were found to be 367 m2/g and of 85 meq/100 g, respectively. The applicability of this clay sample for Cd (II) and Zn (II) removal from aqueous media was tested using batch procedures. Experimental parameters affecting the removal process were analyzed to get optimum conditions for the process. The experimental kinetic data were fitted very well to pseudo-second order with very high correlation coefficients. The Freundlich model appeared to correlate the adsorption data much better than Langmuir model with maximum adsorption capacities of 8.2 and 9.45 mg/g for Cd2+ and Zn2+, respectively. Successful application of the studied adsorbent for the removal of Cd2+ and Zn2+ ions from natural water samples greatly supports its potential for practical application. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>XRD pattern of the Na–B sample.</p> Full article ">Figure 2
<p>FT-IR spectrum of the Na–B sample.</p> Full article ">Figure 3
<p>SEM-EDX analysis of the Na–B sample.</p> Full article ">Figure 4
<p>Effect of pH on the removal of Cd (II) and Zn (II) onto Na–B at initial metal ion concentration = 0.8 ppm, shaking time = 60 min., sorbent dose = 0.05 g/25 mL.</p> Full article ">Figure 5
<p>Effect of sorbent dosage on the removal of Cd (II) and Zn (II) onto Na–B at (initial metal ion concentration = 0.8 ppm, shaking time = 60 min., pH = 6.5).</p> Full article ">Figure 6
<p>Effect of shaking time on the removal of Cd (II) and Zn (II) onto Na–B at (initial metal ion concentration = 0.8 ppm, sorbent content = 0.02 g/25 mL, pH = 6.5).</p> Full article ">Figure 7
<p>Linear fitting of experimental data to pseudo-first order kinetic model with (<b>a</b>) Cadmium and (<b>b</b>) Zinc.</p> Full article ">Figure 8
<p>Linear fitting of experimental data to pseudo-second order kinetic model with (<b>a</b>) Cadmium and (<b>b</b>) Zinc.</p> Full article ">Figure 9
<p>Non-linear fitting of experimental data to Langmuir and Freundlich adsorption isotherms with (<b>a</b>) Cadmium and (<b>b</b>) Zinc.</p> Full article ">
728 KiB  
Review
Experiences and Future Challenges of Bioleaching Research in South Korea
by Danilo Borja, Kim Anh Nguyen, Rene A. Silva, Jay Hyun Park, Vishal Gupta, Yosep Han, Youngsoo Lee and Hyunjung Kim
Minerals 2016, 6(4), 128; https://doi.org/10.3390/min6040128 - 2 Dec 2016
Cited by 46 | Viewed by 9531
Abstract
This article addresses the state of the art of bioleaching research published in South Korean Journals. Our research team reviewed the available articles registered in the Korean Citation Index (KCI, Korean Journal Database) addressing the relevant aspects of bioleaching. We systematically categorized the [...] Read more.
This article addresses the state of the art of bioleaching research published in South Korean Journals. Our research team reviewed the available articles registered in the Korean Citation Index (KCI, Korean Journal Database) addressing the relevant aspects of bioleaching. We systematically categorized the target metal sources as follows: mine tailings, electronic waste, mineral ores and metal concentrates, spent catalysts, contaminated soil, and other materials. Molecular studies were also addressed in this review. The classification provided in the present manuscript details information about microbial species, parameters of operation (e.g., temperature, particle size, pH, and process length), and target metals to compare recoveries among the bioleaching processes. The findings show an increasing interest in the technology from research institutes and mineral processing-related companies over the last decade. The current research trends demonstrate that investigations are mainly focused on determining the optimum parameters of operations for different techniques and minor applications at the industrial scale, which opens the opportunity for greater technological developments. An overview of bioleaching of each metal substrate and opportunities for future research development are also included. Full article
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<p>Metal removal efficiencies obtained by chemical (i.e., sulfuric or ferric chloride leaching) and bioleaching using <span class="html-italic">A. ferrooxidans</span>. The results were obtained at optimum operating conditions: pH, 2; pulp density, 2% (<span class="html-italic">w</span>/<span class="html-italic">v</span>); agitation speed, 120 rpm; and, temperature, 25 ± 2 °C. Data obtained from Bayat and Sari 2010 [<a href="#B22-minerals-06-00128" class="html-bibr">22</a>].</p> Full article ">Figure 2
<p>Number of publications related to bioleaching over time. This graph is based on publications presented in the Korean Journal Database (Thomson Reuters ISI Web of Science).</p> Full article ">
943 KiB  
Article
Optimizing Performance of SABC Comminution Circuit of the Wushan Porphyry Copper Mine—A Practical Approach
by Wei Zhang
Minerals 2016, 6(4), 127; https://doi.org/10.3390/min6040127 - 2 Dec 2016
Cited by 5 | Viewed by 13167
Abstract
This research is focused on the Phase I SABC milling circuit of the Wushan porphyry copper mine. Improvements to the existing circuit were targeted without any significant alterations to existing equipment or the SABC circuit. JKSimMet simulations were used to test various operating [...] Read more.
This research is focused on the Phase I SABC milling circuit of the Wushan porphyry copper mine. Improvements to the existing circuit were targeted without any significant alterations to existing equipment or the SABC circuit. JKSimMet simulations were used to test various operating and design conditions to improve the comminution process. Modifications to the SABC comminution circuit included an increase in the SAG mill ball charge from 8% to 10% v/v; an increase in the mill ball charge from 23% v/v to 27% v/v; an increase in the maximum operating power draw in the ball mill to 5800 kW; the replacement of the HP Series pebble crusher with a TC84 crusher; and the addition of a pebble bin. Following these improvements, an increase in circuit throughput, a reduction in energy consumption, and an increase in profitability were obtained. Full article
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Figure 1
<p>Wushan Phase I SABC circuit layout and equipment specifications.</p> Full article ">Figure 2
<p>JKSimMet screen snapshot of the Wushan Phase I SABC circuit simulation (key is provided at the top middle section of diagram).</p> Full article ">Figure 3
<p>Energy distribution in the SABC comminution circuit.</p> Full article ">Figure 4
<p>Configuration and performance of the SABC circuit if maximum theoretical processing capacity is reached (key is provided at the top middle section of diagram).</p> Full article ">
6867 KiB  
Article
Fibrous Platinum-Group Minerals in “Floating Chromitites” from the Loma Larga Ni-Laterite Deposit, Dominican Republic
by Thomas Aiglsperger, Joaquín A. Proenza, Francisco Longo, Mercè Font-Bardia, Salvador Galí, Josep Roqué and Sandra Baurier-Aymat
Minerals 2016, 6(4), 126; https://doi.org/10.3390/min6040126 - 30 Nov 2016
Cited by 6 | Viewed by 5224
Abstract
This contribution reports on the observation of enigmatic fibrous platinum-group minerals (PGM) found within a chromitite body included in limonite (“floating chromitite”) from Ni-laterites in the Dominican Republic. Fibrous PGM have a Ru-Os-Ir-Fe dominated composition and are characterized by fibrous textures explained by [...] Read more.
This contribution reports on the observation of enigmatic fibrous platinum-group minerals (PGM) found within a chromitite body included in limonite (“floating chromitite”) from Ni-laterites in the Dominican Republic. Fibrous PGM have a Ru-Os-Ir-Fe dominated composition and are characterized by fibrous textures explained by grain-forming fibers which are significantly longer (1–5 µm) than they are wide (~100 nm). Back-scattered electron (BSE) images suggest that these nanofibers are platinum-group elements (PGE)-bearing and form <5 µm thick layers of bundles which are oriented orthogonal to grains’ surfaces. Trace amounts of Si are most likely associated with PGE-bearing nanofibers. One characteristic fibrous PGM was studied in detail: XRD analyses point to ruthenian hexaferrum. However, the unpolished fibrous PGM shows numerous complex textures on its surface which are suggestive for neoformation processes: (i) features suggesting growth of PGE-bearing nanofibers; (ii) occurrence of PGM nanoparticles within film material (biofilm?) associated with PGE-bearing nanofibers; (iii) a Si-rich and crater-like texture hosting PGM nanoparticles and an Ir-rich accumulation of irregular shape; (iv) complex PGM nanoparticles with ragged morphologies, resembling sponge spicules and (v) oval forms (<1 µm in diameter) with included PGM nanoparticles, similar to those observed in experiments with PGE-reducing bacteria. Fibrous PGM found in the limonite may have formed due to supergene (bio-)weathering of fibrous Mg-silicates which were incorporated into desulphurized laurite during stages of serpentinization. Full article
(This article belongs to the Special Issue Mineral Deposit Genesis and Exploration)
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<p>(<b>A</b>) The location of the Loma Caribe peridotite and an orthophotograph of the Falcondo mining area highlighting the Loma Larga ore deposit. The inset shows an idealized Ni-laterite soil profile from the Falcondo mining area as well as a field observation of the PGE-rich “floating chromitite” within limonite (width of image: ~1 m); (<b>B</b>) Simplified geological map of the central section of the Loma Caribe peridotite (modified from [<a href="#B17-minerals-06-00126" class="html-bibr">17</a>,<a href="#B18-minerals-06-00126" class="html-bibr">18</a>]).</p> Full article ">Figure 2
<p>Back-scattered electron (BSE) images of fibrous platinum-group minerals (PGM). (<b>A</b>) fibrous PGM with an anhedral shape; note the fractured lower part of the grain revealing numerous layers of nanofiber-bundles; (<b>B</b>) close-up of nanofiber-bundles; (<b>C</b>) subhedral fibrous PGM; (<b>D</b>) anhedral fibrous PGM with a void in its central part; (<b>E</b>) close-up showing a void with radially propagating nanofiber-bundles; (<b>F</b>) anhedral fibrous PGM; (<b>G</b>) fibrous PGM with an elongated morphology; note that nanofiber-bundles have a symmetric distribution and are orthogonal to the surface of the grain; (<b>H</b>) close-up showing the central part of an elongated fibrous PGM; (<b>I</b>) anhedral fibrous PGM hosting two rounded voids.</p> Full article ">Figure 3
<p>BSE and secondary electron images (SE) of a fibrous PGM showing numerous features: (<b>A</b>) overview; note the isometric, subhedral shape of the grain; (<b>B</b>) close-up of the platinum-group elements (PGE)-bearing nanofiber-bundles; (<b>C</b>) features suggesting either “healing of cracks” or misalignments of nanofibers; (<b>D</b>) layers of PGE-bearing nanofiber-bundles which are oriented orthogonal to the grain’s surface; (<b>E</b>) SE image close-up of nanofibers; (<b>F</b>) BSE image close-up of the same area as in (<b>E</b>); note the bright occurring center of the nanofibers in the BSE image, suggesting the presence of PGE; (<b>G</b>,<b>H</b>) close-up of the contact between PGE-bearing nanofiber-bundles and associated film material (biofilm?) hosting PGM nanoparticles in SE (<b>G</b>) and BSE (<b>H</b>); (<b>I</b>,<b>J</b>) close-up of the film material showing layering and numerous PGM nanoparticles in SE (<b>I</b>) and in BSE (<b>J</b>); (<b>K</b>) detail of the zone around the crater-like texture in the central part of the grain with associated Ir-rich accumulation and complex morphologies of PGM nanoparticles; note the different size and shape of PGM nanoparticles within the dark (Si-rich) crater-like texture compared to its immediate vicinity; (<b>L</b>) approximately 500 nm long oval forms with included PGM nanoparticles resembling observations related to PGE depositing bacteria [<a href="#B21-minerals-06-00126" class="html-bibr">21</a>].</p> Full article ">Figure 3 Cont.
<p>BSE and secondary electron images (SE) of a fibrous PGM showing numerous features: (<b>A</b>) overview; note the isometric, subhedral shape of the grain; (<b>B</b>) close-up of the platinum-group elements (PGE)-bearing nanofiber-bundles; (<b>C</b>) features suggesting either “healing of cracks” or misalignments of nanofibers; (<b>D</b>) layers of PGE-bearing nanofiber-bundles which are oriented orthogonal to the grain’s surface; (<b>E</b>) SE image close-up of nanofibers; (<b>F</b>) BSE image close-up of the same area as in (<b>E</b>); note the bright occurring center of the nanofibers in the BSE image, suggesting the presence of PGE; (<b>G</b>,<b>H</b>) close-up of the contact between PGE-bearing nanofiber-bundles and associated film material (biofilm?) hosting PGM nanoparticles in SE (<b>G</b>) and BSE (<b>H</b>); (<b>I</b>,<b>J</b>) close-up of the film material showing layering and numerous PGM nanoparticles in SE (<b>I</b>) and in BSE (<b>J</b>); (<b>K</b>) detail of the zone around the crater-like texture in the central part of the grain with associated Ir-rich accumulation and complex morphologies of PGM nanoparticles; note the different size and shape of PGM nanoparticles within the dark (Si-rich) crater-like texture compared to its immediate vicinity; (<b>L</b>) approximately 500 nm long oval forms with included PGM nanoparticles resembling observations related to PGE depositing bacteria [<a href="#B21-minerals-06-00126" class="html-bibr">21</a>].</p> Full article ">Figure 4
<p>(<b>A</b>) Stereomicroscope image of the unpolished fibrous PGM grain showing metallic luster; (<b>B</b>) Debye rings for the fibrous PGM, observed on the two dimensional detector; (<b>C</b>) Rietveld refinement of the obtained one dimensional conventional diffractogram [<a href="#B19-minerals-06-00126" class="html-bibr">19</a>] and the resulting XRD pattern for the fibrous PGM (observed and calculated).</p> Full article ">Figure 5
<p>(<b>A</b>) BSE image of the polished fibrous PGM shown in <a href="#minerals-06-00126-f003" class="html-fig">Figure 3</a>A with an indicated area of element mapping and points of EMP analyses (EMPA); (<b>B</b>) close-up of polished PGE-bearing nanofibers next to EMPA point 2; (<b>C</b>) element mapping; note the elevated Si contents where nanofibers are present. For details see the main text.</p> Full article ">
12111 KiB  
Review
Paleozoic–Mesozoic Porphyry Cu(Mo) and Mo(Cu) Deposits within the Southern Margin of the Siberian Craton: Geochemistry, Geochronology, and Petrogenesis (a Review)
by Anita N. Berzina, Adel P. Berzina and Victor O. Gimon
Minerals 2016, 6(4), 125; https://doi.org/10.3390/min6040125 - 29 Nov 2016
Cited by 20 | Viewed by 6770
Abstract
The southern margin of the Siberian craton hosts numerous Cu(Mo) and Mo(Cu) porphyry deposits. This review provides the first comprehensive set of geological characteristics, geochronological data, petrochemistry, and Sr–Nd isotopic data of representative porphyry Cu(Mo) and Mo(Cu) deposits within the southern margin of [...] Read more.
The southern margin of the Siberian craton hosts numerous Cu(Mo) and Mo(Cu) porphyry deposits. This review provides the first comprehensive set of geological characteristics, geochronological data, petrochemistry, and Sr–Nd isotopic data of representative porphyry Cu(Mo) and Mo(Cu) deposits within the southern margin of the Siberian craton and discusses the igneous processes that controlled the evolution of these magmatic systems related to mineralization. Geochronological data show that these porphyry deposits have an eastward-younging trend evolving from the Early Paleozoic to Middle Mesozoic. The western part of the area (Altay-Sayan segment) hosts porphyry Cu and Mo–Cu deposits that generally formed in the Early Paleozoic time, whereas porphyry Cu–Mo deposits in the central part (Northern Mongolia) formed in the Late Paleozoic–Early Mesozoic. The geodynamic setting of the region during these mineralizing events is consistent with Early Paleozoic subduction of Paleo-Asian Ocean plate with the continuous accretion of oceanic components to the Siberian continent and Late Paleozoic–Early Mesozoic subduction of the west gulf of the Mongol–Okhotsk Ocean under the Siberian continent. The eastern part of the study area (Eastern Transbaikalia) hosts molybdenum-dominated Mo and Mo–Cu porphyry deposits that formed in the Jurassic. The regional geodynamic setting during this mineralizing process is related to the collision of the Siberian and North China–Mongolia continents during the closure of the central part of the Mongol–Okhotsk Ocean in the Jurassic. Available isotopic data show that the magmas related to porphyritic Cu–Mo and Mo–Cu mineralization during the Early Paleozoic and Late Paleozoic–Early Mesozoic were mainly derived from mantle materials. The generation of fertile melts, related to porphyritic Mo and Mo–Cu mineralization during the Jurassic involved variable amounts of metasomatized mantle source component, the ancient Precambrian crust, and the juvenile crust, contributed by mantle-derived magmatic underplating. Full article
(This article belongs to the Special Issue Mineral Deposit Genesis and Exploration)
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Figure 1
<p>Paleozoic-Mesozoic magmatism within the southern margin of the Siberian craton and the location of principal porphyry Cu(Mo) and Mo(Cu) deposits. 1–3: Magmatic belts. 1—Early Paleozoic; 2—Late Paleozoic to Early Mesozoic; 3—Mesozoic; 4—faults; 5—porphyry Cu(Mo) deposits; 6—porphyry Mo(Cu) deposits.</p> Full article ">Figure 2
<p>Geological map of the Sora deposit: 1—gabbro, monzogabbro, syenogabbro (Kogtakh complex); 2—syenodiorite, syenite, granodiorite, diorite, monzonite (Martaiga complex); 3—leucogranite, aplite (Tygertysh complex); 4—K-feldspar metasomatites; 5–6: Ore-bearing porphyry complex, 5—granite porphyries I, 6—granite porphyries II; 7—barren dikes; 8—faults; 9—contour of the breccia ore; 10—quartz-molybdenite veins.</p> Full article ">Figure 3
<p>Geological map of the Aksug deposit (modified after Dobryanskiy et al. [<a href="#B41-minerals-06-00125" class="html-bibr">41</a>]). 1–5: The Tannu-Ola series; 1—gabbro; 2—diorite; 3—pyroxen-hornblende quartz diorite; 4—hornblende quartz diorite; 5—tonalite; 6–8: the Aksug porphyry series, 6—porphyry tonalite; 7—granodiorite porphyry I; 8—granodiorite porphyry II; 9—the granite-aplite series: dikes of granodiorite, granite, aplite; 10—the Lower Devonian volcano-sedimentary series; 11—recent sediments; 12—faults; 13—ore zone.</p> Full article ">Figure 4
<p>Geological map of the Erdenetiin Ovoo deposit (modified after [<a href="#B99-minerals-06-00125" class="html-bibr">99</a>]). The Selenge complex: 1—gabbro; 2—granosyenite; 3—granodiorite; porphyry complex: 4—diorite porphyry, granodiorite porphyry; postore dikes: 5—felsite; 6—monzodiorite porphyry; 7—andesite and trachyandesite porphyry; 8—faults; 9—ore zone.</p> Full article ">Figure 5
<p>Geological map of the Zhireken deposit. Plutonic series: 1—granite; ore-bearing series: 2—leucogranite; 3—granite porphyry; 4—mineralized stockwork; 5—faults.</p> Full article ">Figure 6
<p>Geological map of the Shakhtama deposit. 1—Shakhtama series: granite, granosyenite, granodiorite, monzonite, gabbro; 2—Ore-bearing porphyry series: granite, granodiorite, monzonite porphyry; 3—explosive breccia; 4—quartz-molybdenite veins; 5—faults.</p> Full article ">Figure 7
<p>Alkalis vs. SiO<sub>2</sub> diagram (<b>A</b>) with boundaries between the alkaline and subalkaline (tholeiitic) fields (after Irvine and Baragar [<a href="#B109-minerals-06-00125" class="html-bibr">109</a>] and Kuno [<a href="#B110-minerals-06-00125" class="html-bibr">110</a>]) and K<sub>2</sub>O vs. SiO<sub>2</sub> diagram (<b>B</b>) using the classification of Peccerillo and Taylor [<a href="#B111-minerals-06-00125" class="html-bibr">111</a>] for plutonic and porphyry rocks from the Aksug, Sora, Erdenetiin Ovoo, Zhireken, and Shakhtama deposits.</p> Full article ">Figure 8
<p>Diagram of εNd(t)–(<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> for magmatic rocks from the Aksug (<b>A</b>); Sora (<b>B</b>) and Erdenetiin Ovoo (<b>C</b>). The initial Sr and Nd isotopic ratios have been calculated at the ages based on U–Pb and <sup>40</sup>Ar/<sup>39</sup>Ar dating [<a href="#B55-minerals-06-00125" class="html-bibr">55</a>,<a href="#B56-minerals-06-00125" class="html-bibr">56</a>,<a href="#B102-minerals-06-00125" class="html-bibr">102</a>].</p> Full article ">Figure 9
<p>Diagram of primitive-mantle normalized trace elements patterns (<b>A</b>) and chondrite-normalized REE patterns (<b>B</b>) for typical mafic samples from the Aksug, Sora, and Erdenetiin Ovoo. Primitive mantle and chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 10
<p>Diagram of chondrite-normalized REE patterns for typical rocks of felsic and intermediate compositions from Aksug deposit. Chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 11
<p>Diagram of εNd(t)–MgO for magmatic rocks from the Aksug.</p> Full article ">Figure 12
<p>Diagram of primitive-mantle normalized trace elements patterns (<b>A</b>) and chondrite-normalized REE patterns (<b>B</b>) for typical granitoid samples from the Sora deposit. Primitive mantle and chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 13
<p>Diagram of chondrite-normalized REE patterns for high-K calc-alkaline (<b>A</b>) and calc-alkaline (<b>B</b>) granitoids from the Erdenetiin Ovoo deposit. Chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 14
<p>Plots of (La/Yb)<sub>n</sub> versus Yb<sub>n</sub> (<b>A</b>) and Sr/Y versus Y (<b>B</b>) for the Erdenetiin Ovoo granitoids after Drummond and Defant [<a href="#B115-minerals-06-00125" class="html-bibr">115</a>].</p> Full article ">Figure 15
<p>Diagram of primitive-mantle normalized trace elements patterns (<b>A</b>) and chondrite-normalized REE patterns (<b>B</b>) for typical samples from the Zhireken deposit. Primitive mantle and chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 16
<p>Diagram of εNd(t)–(<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> for magmatic rocks from the Zhireken deposit.</p> Full article ">Figure 17
<p>Diagram of primitive-mantle normalized trace elements patterns (<b>A</b>) and chondrite-normalized REE patterns (<b>B</b>) for typical samples from the Shakhtama deposit. Primitive mantle and chondrite normalizing values are after McDonough and Sun [<a href="#B112-minerals-06-00125" class="html-bibr">112</a>].</p> Full article ">Figure 18
<p>Diagram of εNd(t)–(<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> for magmatic rocks from the Shakhtama deposit.</p> Full article ">
25812 KiB  
Article
Genesis and Multi-Episodic Alteration of Zircon-Bearing Chromitites from the Ayios Stefanos Mine, Othris Massif, Greece: Assessment of an Unconventional Hypothesis on the Origin of Zircon in Ophiolitic Chromitites
by Argyrios Kapsiotis, Annie Ewing Rassios, Aspasia Antonelou and Evangelos Tzamos
Minerals 2016, 6(4), 124; https://doi.org/10.3390/min6040124 - 21 Nov 2016
Cited by 14 | Viewed by 6948
Abstract
Several small chromium (Cr) ore bodies are hosted within a unit of tectonically thinned dunite in the retired Ayios Stefanos mine of the western Othris ophiolite complex in Greece. Chromium ores consist of tectonically imprinted bodies of semi-massive to massive, podiform and lenticular [...] Read more.
Several small chromium (Cr) ore bodies are hosted within a unit of tectonically thinned dunite in the retired Ayios Stefanos mine of the western Othris ophiolite complex in Greece. Chromium ores consist of tectonically imprinted bodies of semi-massive to massive, podiform and lenticular chromitites composed of chromian spinel [Cr-spinel] with high Cr# [Cr/(Cr + Al) = 0.51–0.66] and Mg# [Mg/(Mg + Fe2+) = 0.58–0.76], low Fe3+# [Fe3+/(Fe3+ + Fe2+) ≤ 0.43] and low TiO2 (≤0.21 wt %) content. This composition is characteristic of Cr-spinels in equilibrium with melts of intermediate affinity between island-arc tholeiites (IATs) and mid-ocean ridge basalts (MORBs). Several Cr-spinel crystals in these ores exhibit imperfect zones made up of spinel hosting oriented lamellae of Mg-silicates (mostly chlorite) locally overgrown by porous domains along grain boundaries and fractures. From the Cr-spinel core to the lamellae-rich rim Cr#, Mg# and Fe3+# generally increase (0.68–0.87, 0.78–0.88 and 0.55–0.80, respectively), whereas from the core or the spinel zones with oriented lamellae to the porous domains Mg# and Fe3+# generally decrease (0.45–0.74 and ≤0.51, correspondingly). The lamellae-rich rims formed at oxidizing conditions, whereas the porous rims resulted from a later reducing event. Several tiny (≤30 μm), subhedral to anhedral and elongated Zr-bearing silicate mineral grains were discovered mainly along open and healed fractures cutting Cr-spinel. Most of the Zr-bearing silicate minerals (30 out of 35 grains) were found in a chromitite boulder vastly intruded by a complex network of gabbroic dykes. The dominant Zr-bearing silicate phase is by far zircon displaying a homogeneous internal texture in cathodoluminescence (CL) images. Raman spectroscopy data indicate that zircons have experienced structural damage due to self-irradiation. Their trace-element contents suggest derivation from a plagioclase-bearing, low-SiO2 intermediate to mafic source. Combined micro-textural and minerochemical data repeat the possibility of zircon derivation from limited volumes of high-T fluids emanating from the gabbroic intrusions. Once zircon is precipitated in cracks, it may be altered to Ca-rich Zr-bearing silicate phases (i.e., armstrongite, calciocatapleiite). Almost all zircons in these samples show evidence of gains in solvent compounds (CaO, Al2O3 and FeO) possibly due to re-equilibration with late deuteric fluids. Full article
(This article belongs to the Special Issue Mineral Deposit Genesis and Exploration)
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<p>Distribution of ophiolites in the southernmost part of the Balkan Peninsula (modified after [<a href="#B30-minerals-06-00124" class="html-bibr">30</a>]). Key to lettering: V = Vourinos; P = Pindos; O = Othris (also marked by the open square). The initials F.Y.R.O.M. stand for Former Yugoslav Republic of Macedonia.</p> Full article ">Figure 2
<p>Geological map of the Othris ophiolite complex [<a href="#B33-minerals-06-00124" class="html-bibr">33</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) Geological map of the Ayios Stefanos region illustrating the bowing of structures synchronous to ‘hot’ nappe emplacement [<a href="#B36-minerals-06-00124" class="html-bibr">36</a>]; (<b>b</b>) The serpentinized dunite-harzburgite ductile-brittle thrust zone that separates the peridotite nappes in the Ayios Stefanos area; (<b>c</b>) A gabbroic dyke in the chromitite boulder within the quarry talus (this figure also appears in [<a href="#B36-minerals-06-00124" class="html-bibr">36</a>]). Abbreviations (in order of appearance): Cr = chromitite gallery (in b) and chromitite (in c); Sr = serpentinite; Gbr = gabbroic dyke.</p> Full article ">Figure 4
<p>Photomicrographs illustrating the petrographic characteristics of the Ayios Stefanos chromitites. (<b>a</b>) Reddish lobate Cr-spinel; (<b>b</b>) Chromian spinel displaying pull-apart‒like texture (marked by the white arrows); (<b>c</b>,<b>d</b>) Rutile exsolutions developed in three crystallographic orientations [Rt<sub>(a)</sub>, Rt<sub>(b)</sub>, Rt<sub>(c)</sub>]; (<b>e</b>) Bastite cut by late serpentine veins; (<b>f</b>) Serpentine showing hourglass texture. Abbreviations (in order of appearance): Chr = Cr-spinel; Srp = serpentine; Rt = rutile; Srp<sub>1</sub> = early serpentine; Srp<sub>2</sub> = late serpentine; PPL = plane polarized light; XPL = crossed polarized light; BSE = back scattered electron (image).</p> Full article ">Figure 5
<p>Photomicrographs illustrating Cr-spinel textural modification. (<b>a</b>) Chromian spinel surrounded by a dark grey rim; (<b>b</b>) The same image in XPL showing that the rim is surrounded by chlorite; (<b>c</b>) Chromian spinel almost entirely replaced by a bright (spinel) phase; (<b>d</b>) Porous spinel for Cr-spinel substitution; (<b>e</b>,<b>f</b>) Spongy spinel displaying elongation of pores; (<b>g</b>) Cr-spinel with a boundary made up of spinel mixed with Mg-silicates; (<b>h</b>) Close up of the white, open square in (<b>g</b>) illustrating the oriented Mg-silicate lamellae micro-texture in Cr-spinel. The intersection of Mg-silicate needles in three directions is also marked. Abbreviations (in order of appearance): Fe-Chr = altered spinel; Chl = chlorite; Fe-Chr<sub>1</sub> = lamellae-rich spinel; Fe-Chr<sub>2</sub> = porous spinel; Hgr = hydrogrossular; the rest as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a>.</p> Full article ">Figure 5 Cont.
<p>Photomicrographs illustrating Cr-spinel textural modification. (<b>a</b>) Chromian spinel surrounded by a dark grey rim; (<b>b</b>) The same image in XPL showing that the rim is surrounded by chlorite; (<b>c</b>) Chromian spinel almost entirely replaced by a bright (spinel) phase; (<b>d</b>) Porous spinel for Cr-spinel substitution; (<b>e</b>,<b>f</b>) Spongy spinel displaying elongation of pores; (<b>g</b>) Cr-spinel with a boundary made up of spinel mixed with Mg-silicates; (<b>h</b>) Close up of the white, open square in (<b>g</b>) illustrating the oriented Mg-silicate lamellae micro-texture in Cr-spinel. The intersection of Mg-silicate needles in three directions is also marked. Abbreviations (in order of appearance): Fe-Chr = altered spinel; Chl = chlorite; Fe-Chr<sub>1</sub> = lamellae-rich spinel; Fe-Chr<sub>2</sub> = porous spinel; Hgr = hydrogrossular; the rest as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a>.</p> Full article ">Figure 6
<p>Photomicrographs showing the micro-structural sites of zircons. (<b>a</b>–<b>c</b>) Zircon found along open or healed cracks in Cr-spinel; (<b>d</b>) Zircon hosted by porous spinel; (<b>e</b>,<b>f</b>) Zircon in cataclastic zones. Abbreviations: Zrn = zircon; the rest as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a> and <a href="#minerals-06-00124-f005" class="html-fig">Figure 5</a>.</p> Full article ">Figure 7
<p>Photomicrographs illustrating the impact of alteration on zircons. (<b>a</b>) Subhedral, altered zircon in Cr-spinel; (<b>b</b>) Elongated zircon; (<b>c</b>) Intergrowth of zircon with calciocatapleiite; (<b>d</b>–<b>f</b>) Almost complete armstrongite for zircon substitution. Abbreviations (in order of appearance): Zrn* = altered zircon; Arm = armstrongite; Cpl = calciocatapleiite; Mg-Si* = unidentified Zr-bearing Mg-silicate; the rest as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a>, <a href="#minerals-06-00124-f005" class="html-fig">Figure 5</a> and <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>.</p> Full article ">Figure 7 Cont.
<p>Photomicrographs illustrating the impact of alteration on zircons. (<b>a</b>) Subhedral, altered zircon in Cr-spinel; (<b>b</b>) Elongated zircon; (<b>c</b>) Intergrowth of zircon with calciocatapleiite; (<b>d</b>–<b>f</b>) Almost complete armstrongite for zircon substitution. Abbreviations (in order of appearance): Zrn* = altered zircon; Arm = armstrongite; Cpl = calciocatapleiite; Mg-Si* = unidentified Zr-bearing Mg-silicate; the rest as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a>, <a href="#minerals-06-00124-f005" class="html-fig">Figure 5</a> and <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>.</p> Full article ">Figure 8
<p>Cathodoluminescence (CL) images of selected Zr-bearing silicate crystals. (<b>a</b>) Zircon (marked by the red, open square in <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>c) with nearly homogeneous texture; (<b>b</b>–<b>e</b>) Zirconium-bearing silicates with irregular texture [originally depicted in <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>f and <a href="#minerals-06-00124-f007" class="html-fig">Figure 7</a>a–c (in the last figure the imaged zircon is marked by a red square)]; (<b>f</b>) Armstrongite (originally depicted in <a href="#minerals-06-00124-f007" class="html-fig">Figure 7</a>e) with very weak CL intensity.</p> Full article ">Figure 9
<p>(<b>a</b>–<b>c</b>) Single-element (WDS) X-ray maps of the zircon grain originally illustrated in <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>a; (<b>d</b>–<b>f</b>) Single-element (WDS) X-ray maps of the zircon grain originally illustrated in <a href="#minerals-06-00124-f007" class="html-fig">Figure 7</a>c (marked by the red square). Line scans are also shown for the zircon crystal depicted in <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>a, where the beginning of analyses is marked by the dark blue circle. Abbreviations are as in <a href="#minerals-06-00124-f004" class="html-fig">Figure 4</a> and <a href="#minerals-06-00124-f006" class="html-fig">Figure 6</a>.</p> Full article ">Figure 10
<p>Pristine Cr-spinel composition in terms of: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> vs. Cr<sub>2</sub>O<sub>3</sub>; (<b>b</b>) Cr# [= Cr/(Cr + Al)] vs. Mg# [= Mg/(Mg + Fe<sup>2+</sup>)]; (<b>c</b>) TiO<sub>2</sub> vs. Cr# and (<b>d</b>) TiO<sub>2</sub> vs. Al<sub>2</sub>O<sub>3</sub> (wt %). Fields for podiform and stratiform chromitites are from [<a href="#B42-minerals-06-00124" class="html-bibr">42</a>]. Fields for spinel in equilibrium with N-MORBs and boninites in (<b>b</b>) are from [<a href="#B43-minerals-06-00124" class="html-bibr">43</a>]. Fields for Cr-spinel in equilibrium with MORBs, IATs and boninites in (<b>c</b>) are from [<a href="#B44-minerals-06-00124" class="html-bibr">44</a>]. Compositional fields in (<b>d</b>) are from [<a href="#B45-minerals-06-00124" class="html-bibr">45</a>]. Abbreviations: (N-)MORBS = (normal) mid-ocean ridge basalts, IAT = island arc tholeiites, BABB = back-arc basin basalts; OIB = ocean islands basalts, LIP = large igneous province (basalts).</p> Full article ">Figure 11
<p>Variations of altered Cr-spinel in terms of: (<b>a</b>) Cr# vs. Mg#; (<b>b</b>) Fe<sup>3+</sup># vs. Mg#. The composition of Cr-spinel is contoured at a nominal <span class="html-italic">T</span> of 1200 °C for olivine compositions from Fo<sub>80</sub> to Fo<sub>96</sub> [<a href="#B43-minerals-06-00124" class="html-bibr">43</a>]. Abbreviations as in <a href="#minerals-06-00124-f005" class="html-fig">Figure 5</a>.</p> Full article ">Figure 12
<p>Single-element (EDS) X-ray maps on part of a Cr-spinel grain that displays oriented lamellae intergrowth texture.</p> Full article ">Figure 13
<p>Plot of major and minor element abundances in zircon in the following variation diagrams: (<b>a</b>) ZrO<sub>2</sub> vs. SiO<sub>2</sub>; (<b>b</b>) Al vs. Zr at. %; (<b>c</b>) HfO<sub>2</sub>/Y<sub>2</sub>O<sub>3</sub> vs. ZrO<sub>2</sub>/Y<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 14
<p>(<b>a</b>) Raman spectra in the wavenumber range of 100–1025 cm<sup>−1</sup> for the studied zircons; (<b>b</b>) Spectra of zircons normalized to the height of the <span class="html-italic">v</span><sub>3</sub>(SiO<sub>4</sub>) stretching mode at ~1008 cm<sup>−1</sup>.</p> Full article ">Figure 15
<p>Plots of the calculated Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> contents of the parental melts in equilibrium with chromitites. The MORB and Arc lines are from [<a href="#B53-minerals-06-00124" class="html-bibr">53</a>] using data on spinel-melt inclusions in MORB and arc lavas reported by [<a href="#B45-minerals-06-00124" class="html-bibr">45</a>,<a href="#B56-minerals-06-00124" class="html-bibr">56</a>]. The range of Cr-spinel and the calculated melt compositions from the chromitites of the shallow and deep mantle section in Oman [<a href="#B56-minerals-06-00124" class="html-bibr">56</a>] are shown for comparison. Only data of chromitite samples not associated with gabbroic intrusions were used for computation.</p> Full article ">Figure 16
<p>Trace element correlations for zircons. (<b>a</b>) Y (ppm) vs. U (ppm); (<b>b</b>) Y (ppm) vs. Th (ppm); (<b>c</b>) Hf (wt %) vs. Y (ppm). Fields in (<b>a</b>,<b>b</b>) are from [<a href="#B77-minerals-06-00124" class="html-bibr">77</a>]; fields in (<b>c</b>) are from [<a href="#B78-minerals-06-00124" class="html-bibr">78</a>] (I = kimberlites, II = ultramafic, mafic and intermediate rocks, III = quartz-bearing intermediate and felsic rocks, IV = felsic rocks with ‘high’ SiO<sub>2</sub> content, V = greisens, VI =alkaline rocks and alkaline metasomatites of alkaline complexes, VII = carbonatites).</p> Full article ">Figure 17
<p>Compositional changes in spinel phases from the examined chromitites expressed in a triangular Al-Fe<sup>3+</sup>-Cr diagram with special reference to the fields of the different metamorphic facies defined for Cr-spinels by [<a href="#B89-minerals-06-00124" class="html-bibr">89</a>,<a href="#B90-minerals-06-00124" class="html-bibr">90</a>,<a href="#B91-minerals-06-00124" class="html-bibr">91</a>]. Solvus determined at 600, 550 and 500 °C by [<a href="#B88-minerals-06-00124" class="html-bibr">88</a>] for Cr-spinel coexisting with forsteritic olivine (Fo<sub>90</sub>). Explanation of symbols as in <a href="#minerals-06-00124-f011" class="html-fig">Figure 11</a>.</p> Full article ">
11955 KiB  
Article
Quijarroite, Cu6HgPb2Bi4Se12, a New Selenide from the El Dragόn Mine, Bolivia
by Hans-Jürgen Förster, Luca Bindi, Günter Grundmann and Chris J. Stanley
Minerals 2016, 6(4), 123; https://doi.org/10.3390/min6040123 - 18 Nov 2016
Cited by 8 | Viewed by 5469
Abstract
Quijarroite, ideally Cu6HgPb2Bi4Se12, is a new selenide species from the El Dragόn mine, Department of Potosí, Bolivia. It most frequently occurs as lath-shaped thin plates (up to 150 µm in length and 20 µm in [...] Read more.
Quijarroite, ideally Cu6HgPb2Bi4Se12, is a new selenide species from the El Dragόn mine, Department of Potosí, Bolivia. It most frequently occurs as lath-shaped thin plates (up to 150 µm in length and 20 µm in width) intimately (subparallel) intergrown with hansblockite, forming an angular network-like intersertal texture. Quijarroite is occasionally also present as sub- to anhedral grains up to 200 µm in length and 50 µm in width. It is non-fluorescent, black and opaque with a metallic luster and black streak. It is brittle, with an irregular fracture and no obvious cleavage and parting. In plane-polarized incident light, quijarroite is weakly pleochroic from cream to very slightly more brownish-cream, displaying no internal reflections. Between crossed polars, quijarroite is moderately anisotropic with pale orange-brown to blue rotation tints. Lamellar twinning on {110} is common; parquet twinning occurs rarely. The reflectance values in the air for the COM (Commission on Ore Mineralogy) standard wavelengths (R1 and R2) are: 46.7, 46.8 (470 nm), 47.4, 48.2 (546 nm), 47.1, 48.5 (589 nm), and 46.6, 48.7 (650 nm). Electron-microprobe analyses yielded a mean composition of Cu 13.34, Ag 1.02, Hg 7.67, Pb 16.87, Co 0.03, Ni 0.15, Bi 27.65, Se 33.52, total 100.24 wt %. The mean empirical formula, normalized to 25 apfu (atoms per formula unit), is (Cu5.84Ag0.26)Σ = 6.10(Hg1.06Ni0.07Co0.01)Σ = 1.14Pb2.27Bi3.68Se11.81 (n = 24). The simplified formula is Cu6HgPb2Bi4Se12. Quijarroite is orthorhombic, space group Pmn21, with a = 9.2413(8), b = 9.0206(7), c = 9.6219(8) Å, V = 802.1(1) Å3, Z = 1. The calculated density is 5.771 g·cm−3. The five strongest X-ray powder-diffraction lines (d in Å (I/I0) (hkl)) are: 5.36 (55) (111), 3.785 (60) (211), 3.291 (90) (022), 3.125 (100) (212), and 2.312 (50) (400). The crystal structure of quijarroite can be considered a galena derivative and could be derived from that of bournonite. It is a primary mineral, deposited from an oxidizing low-T hydrothermal fluid at a f S e 2 / f S 2 ratio greater than unity. The new species has been approved by the IMA-CNMNC (2016-052) and is named for the Quijarro Province in Bolivia, in which the El Dragón mine is located. Full article
(This article belongs to the Special Issue Se-Bearing Minerals: Structure, Composition, and Origin)
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<p>Back-scattered electron (BSE) image showing quijarroite (qu, dark grey) subparallel to and intergrown with hansblockite (hb, light grey) and associated with clausthalite (cl, bright).</p> Full article ">Figure 2
<p>BSE image showing acicular grains of quijarroite (qu) in the matrix and intergrown with watkinsonite (wa) and clausthalite (cl), and associated with grundmannite (gr).</p> Full article ">Figure 3
<p>Reflected light digital images of quijarroite (qu) in association with hansblockite (hb), clausthalite (cl), krut’aite-penroseite (k-p), klockmannite (kl), umangite (u), and eldragόnite (eld). Horizontal field of view is 200 µm. Left images: one polarizer; right images: Partly crossed polarizers.</p> Full article ">Figure 4
<p>The crystal structure of quijarroite (<b>a</b>) compared to that of bournonite (<b>b</b>) [<a href="#B14-minerals-06-00123" class="html-bibr">14</a>], both drawn down [001]. In quijarroite, dark blue spheres indicate the linearly coordinated Cu/Hg atoms, whereas light blue tetrahedra refer to the partially occupied Cu position (Cu<sub>0.75</sub>☐<sub>0.25</sub>). Light, dark green and red spheres refer to Bi, Pb and Se, respectively. In bournonite, light blue tetrahedra refer to Cu, whereas green, red and yellow spheres refer to Pb, As and S, respectively.</p> Full article ">Figure 5
<p>(Cu + Ag)−Hg−Bi (<span class="html-italic">% apfu</span>) ternary diagram showing the mean compositions of minerals of the Cu−Hg−Pb−Bi−Se system from El Dragón. Note the correspondence of quijarroite with phase “A” and hansblockite with phase “B” within analytical error. Data sources: [<a href="#B4-minerals-06-00123" class="html-bibr">4</a>,<a href="#B5-minerals-06-00123" class="html-bibr">5</a>], this paper and [<a href="#B2-minerals-06-00123" class="html-bibr">2</a>], for phases “A” and “B”.</p> Full article ">
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Article
Formation of Carbonate Nanoglobules by a Mixed Natural Culture under Hypersaline Conditions
by Nurgul Balci and Cansu Demirel
Minerals 2016, 6(4), 122; https://doi.org/10.3390/min6040122 - 11 Nov 2016
Cited by 16 | Viewed by 4578
Abstract
The present study demonstrated formation of Ca and P rich nanoglobules by a mixed natural halophilic population enriched from hypersaline lake sediments in laboratory culture experiments. Nanoglobules consisting of complex mixture of Ca, P, O, and C with minor amount of Mg occurred [...] Read more.
The present study demonstrated formation of Ca and P rich nanoglobules by a mixed natural halophilic population enriched from hypersaline lake sediments in laboratory culture experiments. Nanoglobules consisting of complex mixture of Ca, P, O, and C with minor amount of Mg occurred in the external envelop of bacterial cell in the first week of incubation at various Mg+2/Ca+2 ratios and salinity at 30 °C. Unlike the control experiments (e.g., non-viable cells and without cells), later aggregation and transformation of nanoglobules caused the precipitation of calcium and/or magnesium carbonates in variable amount depending on the Mg+2/Ca+2 ratios of the medium after 37 days of incubation. By showing the nucleation of carbonates on bacterial nanoglobules closely associated with the cell surfaces of mixed natural population this study emphasis that formation of nanoglobules may not be specific to a microbial strain or to activity of a particular microbial group. Formation of carbonate nanoglobules under various conditions (e.g., Mg+2/Ca+2 ratios, salinity) with the same halophilic culture suggest that the although metabolic activity of bacteria have an influence on formation of nanoglobules the mineralogy of nanoglobules may be controlled by the physicochemical conditions of the precipitation solution and the rate of mineral precipitation. Full article
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<p>Location of the study area and sampling points in Lake Acıgöl, SW Turkey.</p> Full article ">Figure 2
<p>Evolution of pH during the precipitation experiments: (<b>a</b>) M1–M4; and (<b>b</b>) M6–M8 experiments.</p> Full article ">Figure 3
<p>Evolution of Mg<sup>+2</sup> and Ca<sup>+2</sup> ions during the precipitation experiments: (<b>a</b>) M1–M2; (<b>b</b>) M3–M4; (<b>c</b>) M6–M7; (<b>d</b>) M8.</p> Full article ">Figure 4
<p>Evolution of total organic carbon (TOC) (<b>a</b>) and dissolved inorganic carbon (DIC) (<b>b</b>) during the precipitation experiments.</p> Full article ">Figure 5
<p>Light microscopic photographs of carbonate and struvite with a mix halophilic culture: (<b>a</b>,<b>b</b>) spherical calcite precipitate of different sizes formed (M3 and M6 experiments); (<b>c</b>) dumbbell-shaped dolomite precipitates (M6 and M8 experiments); and (<b>d</b>) small rounded aggregates around the bacterial colonies.</p> Full article ">Figure 6
<p>SEM photomicrographs of early precipitates in various experiments: (<b>a</b>,<b>b</b>) extensive formation of nanoglobules in the external envelop of cell and in EPS after three days incubation (M6 and M3 experiments, respectively); (<b>c</b>) nanoglobule and nanoglobules aggregates on cells after six days incubation (M4 experiment), note the nanoglobules delimiting ovoidal cell contours; (<b>d</b>) extensive formation of nanoglobule in the outer of bacterial cell after five days incubation (M4 experiment); (<b>e</b>) nanoglobules in the external envelop of <span class="html-italic">Virgibacillus marismortui strain TPA3-3</span> after three days incubation (M3 experiment); and (<b>f</b>) a closer view of e.</p> Full article ">Figure 7
<p>Energy dispersive (EDX) spectra of mineralized cells and nanoglobules indicated in <a href="#minerals-06-00122-f006" class="html-fig">Figure 6</a>. (<b>a</b>) EDX spectra of g in <a href="#minerals-06-00122-f006" class="html-fig">Figure 6</a>b; (<b>b</b>) EDX spectra of h in <a href="#minerals-06-00122-f006" class="html-fig">Figure 6</a>d; (<b>c</b>) EDX spectra of i in <a href="#minerals-06-00122-f006" class="html-fig">Figure 6</a>f.</p> Full article ">Figure 8
<p>SEM photomicrographs and EDX spectra of carbonate bioliths formed during 10 days of incubation: (<b>a</b>) calcite with spiny surfaces and nanoglobule aggregates closely associated with EPS and the cells (M6 experiment); note the early stage of calcite crystal associated with the cell in the area squared; (<b>b</b>) nanoglobule aggregates with EDX (g); (<b>c</b>) spherulite and dumbbell (M6 experiment); (<b>d</b>) a closer view of the area h square in c, note the aggregated nanoparticles on the surface of calcite (M6 experiment); (<b>e</b>) a closer view of the area i square in c, note irregular size of nanoglobules on the surface of spherulite (i) in c; and (<b>f</b>) aggregated nanoglobules and mineralized bacteria with EDX spectra of the squared area.</p> Full article ">Figure 9
<p>SEM photomicrographs of carbonate bioliths at the end of the experiments (37 days of incubation): (<b>a</b>) Calcite crystal (arrow indicate), drusiform calcite (<b>g</b>) formed accumulation of nanocrystals calcite with EDX in M3 experiment; (<b>b</b>) Isolated spherical bioliths. In square h hydromagnesite with fibrous radiated internal structure with EDX (<b>i</b>) (M8 experiment) and spheroidal hydromagnesite in square I; (<b>c</b>) A closer view of the area i square in b, note the nanoglobules around bacterial moulds (M7 experiment); (<b>d</b>) A closer view of the area h square in b, interior of fibrous radiated spherulite with reticulated zones and widespread bacterial moulds (M8 experiment); (<b>e</b>) Large spherulites and dumbbell shape bioliths (M6 experiment); (<b>f</b>) A closer view of the square area in e with EDX, surface of spherulite and the bacterial moulds is formed by aggregates of crystalline nanoparticles.</p> Full article ">Figure 10
<p>(<b>a</b>) Apatite crystal developed in M1 and M2 experiments; and (<b>b</b>) a closer view of the squared area in a.</p> Full article ">
4567 KiB  
Article
A New Experimental Approach to Improve the Quality of Low Grade Silica; The Combination of Indirect Ultrasound Irradiation with Reverse Flotation and Magnetic Separation
by Hamed Haghi, Mohammad Noaparast, Sied Ziaedin Shafaei Tonkaboni and Mirsaleh Mirmohammadi
Minerals 2016, 6(4), 121; https://doi.org/10.3390/min6040121 - 10 Nov 2016
Cited by 14 | Viewed by 5908
Abstract
Removal of iron impurities in silica is one of the most important issues in the glass industry. The most noted impurities are surface coating and staining on silica particles; additionally, some cases of inclusions are observed. The prepared silica sample, for this research [...] Read more.
Removal of iron impurities in silica is one of the most important issues in the glass industry. The most noted impurities are surface coating and staining on silica particles; additionally, some cases of inclusions are observed. The prepared silica sample, for this research work, mostly was in the size range of 106–425 µm. Mineralogical studies indicated the existence of goethite, hematite, limonite and pyrite as the major iron impurities. The poor liberation degree of silica particles from clays encouraged the use of ultrasound irradiation to improve the efficiency of reverse flotation. The head sample contained 96.98% SiO2, 0.143% Fe2O3, 1.52% Al2O3, and 0.088% TiO2; Fe2O3 had to be reduced to below 0.04%. The reverse flotation tests were carried out with and without indirect ultrasound irradiation. The lowest Fe2O3 grade of the flotation yield was 0.058% and this was achieved using 2000 g/t of C4 collector with 15 min conditioning at neutral pH. C4 consisted of Aero 801, Aero 825, oleic acid and sodium oleate at equal dosage. As a result, a flowsheet was developed to include indirect ultrasound irradiation with reverse flotation and two stages of dry high intensity magnetic separation. In conclusion, the best product contained 98.43% SiO2, 0.034% Fe2O3, 0.90% Al2O3 and 0.051% TiO2. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>X-ray diffraction (XRD) pattern of the head sample.</p> Full article ">Figure 2
<p>(<b>a</b>) Designed setup for conditioning with/without ultrasound irradiation for the reverse flotation experiments including monitoring of pH and temperature; (<b>b</b>) operating zone of the Exolon induced roll magnetic separator in the cleaner stage; and (<b>c</b>) schematic flowsheet for purification of silica, combining ultrasound irradiation with reverse flotation and magnetic separation.</p> Full article ">Figure 3
<p>Effect of ultrasound irradiation on the SiO<sub>2</sub> and Fe<sub>2</sub>O<sub>3</sub> grades of the flotation concentrate.</p> Full article ">Figure 4
<p>Effect of ultrasound irradiation on the Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> grades of the flotation concentrate.</p> Full article ">Figure 5
<p>Effect of ultrasound irradiation on Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub> and Fe<sub>2</sub>O<sub>3</sub> removal in reverse flotation.</p> Full article ">Figure 6
<p>Effect of mixed collectors on yield, silica and impurity grades under different conditions.</p> Full article ">Figure 7
<p>Effect of mixed collectors on silica recovery and impurity removal under different conditions.</p> Full article ">Figure 8
<p>Effect of mixed collectors on the selectivity index of impurities under different conditions.</p> Full article ">Figure 9
<p>Effect of ultrasound irradiation on selectivity index and Fe<sub>2</sub>O<sub>3</sub> removal in dry high intensity magnetic separation.</p> Full article ">Figure 10
<p>Effect of ultrasound irradiation on product grades for the silica purification flowsheet.</p> Full article ">Figure 11
<p>Effect of ultrasound irradiation on Fe<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub> removal efficiency for the silica purification flowsheet.</p> Full article ">Figure 12
<p>Flow sheet of the silica processing plant and points of sampling [<a href="#B4-minerals-06-00121" class="html-bibr">4</a>].</p> Full article ">
8774 KiB  
Article
Mineralogy, Geochemistry and Fluid Inclusion Data from the Tumanpınarı Volcanic Rock-Hosted Fe-Mn-Ba Deposit, Balıkesir-Dursunbey, Turkey
by Ali Haydar Gultekin and Nurgul Balci
Minerals 2016, 6(4), 120; https://doi.org/10.3390/min6040120 - 4 Nov 2016
Cited by 4 | Viewed by 6791
Abstract
The Tumanpınarı mineralization is a volcanic rock-hosted epithermal Fe-Mn-Ba deposit located in the southwestern part of Dursunbey, Balıkesir, Turkey. The deposit constitutes one of the most important deposits of the Havran-Dursunbey metallogenic sub-province in which numerous Early Miocene Fe-Mn-Ba deposits are distributed. The [...] Read more.
The Tumanpınarı mineralization is a volcanic rock-hosted epithermal Fe-Mn-Ba deposit located in the southwestern part of Dursunbey, Balıkesir, Turkey. The deposit constitutes one of the most important deposits of the Havran-Dursunbey metallogenic sub-province in which numerous Early Miocene Fe-Mn-Ba deposits are distributed. The ore occurs as open-space fillings in faults, fractures, and breccias in the andesite. Early hydrothermal activity was responsible for four types of hypogene alteration in decreasing intensity: silicification, sericitization, hematization and argillic alteration. The mineral assemblage includes pyrolusite, psilomelane, hematite, and barite as well as minor magnetite, manganite, poliannite, limonite, braunite, bixbyite, galena, pyrite, and goethite. Mineralogically, three ore types are recognized as pyrolusite + psilomelane + hematite + barite ore, pyrolusite + psilomelane + poliannite ore and barite + pyrolusite + psilomelane + hematite ore (barite-dominant ore). In addition to Fe, Mn and Ba, the ore contains substantial quantities of Pb, Zn, As. Chemically, the transition from fresh to altered rocks has little effect on the elemental levels for Si, Al, Fe, Ca, Mg, K, Rb, Sr and H2O. The homogenization temperature of fluid inclusions hosted in the main stage quartz and barite ranged from 113 to 410 °C with salinities ranging from 0.4 to 14.9 eq. wt % NaCl, respectively. Overall, the available data suggest that the deposits formed as the result of the interaction of two aqueous fluids: a higher-salinity fluid (probably magmatic) and a dilute meteoric fluid. Full article
(This article belongs to the Special Issue Mineral Deposit Genesis and Exploration)
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<p>(<b>A</b>,<b>B</b>) Location of the study area; (<b>C</b>) The Alpine metallogenic units in northwestern Turkey; (<b>D</b>) General geological map of the Balıkesir-Dursunbey region [<a href="#B19-minerals-06-00120" class="html-bibr">19</a>]; (<b>E</b>) Geological map of the Tumanpınarı mineral area.</p> Full article ">Figure 2
<p>Local geological map of the study area, showing the ore veins, altered and unaltered andesite.</p> Full article ">Figure 3
<p>Hydrothermal alteration zones at the Tumanpınarı deposit.</p> Full article ">Figure 4
<p>Simplified paragenetic sequence of events in the Tumanpınarı area.</p> Full article ">Figure 5
<p>(<b>a</b>) Plot of volcanic rocks on Zr/TiO<sub>2</sub>–Nb/Y ratio diagram [<a href="#B26-minerals-06-00120" class="html-bibr">26</a>]; (<b>b</b>) Position of samples on K<sub>2</sub>O–SiO<sub>2</sub> variation diagram [<a href="#B7-minerals-06-00120" class="html-bibr">7</a>].</p> Full article ">Figure 6
<p>Trace element concentrations normalized to the composition of primitive mantle.</p> Full article ">Figure 7
<p>Variation in the concentrations of some elements in two sections crossing the Fe-Mn-Ba and Ba ores at Tumanpınarı.</p> Full article ">Figure 8
<p>Binary plots of (<b>a</b>) Rb vs. Sr; (<b>b</b>) H<sub>2</sub>O vs. Sr; (<b>c</b>) H<sub>2</sub>O vs. Rb; (<b>d</b>) H<sub>2</sub>O vs. MgO; and (<b>e</b>) P<sub>2</sub>O<sub>5</sub> vs. SiO<sub>2</sub> for the unaltered and altered andesite.</p> Full article ">Figure 9
<p>Homogenization temperature (Th) versus salinity for primary fluid inclusions contained in quartz and barite. Diagonal grid lines show fluid densities in gm/cm<sup>3</sup> from the system NaCl-H<sub>2</sub>O [<a href="#B29-minerals-06-00120" class="html-bibr">29</a>] Data from porphyry copper deposits, Mississippi Valey, Fengjia, Farsesh, Mayflower and Kızılcaören are from [<a href="#B30-minerals-06-00120" class="html-bibr">30</a>,<a href="#B31-minerals-06-00120" class="html-bibr">31</a>,<a href="#B32-minerals-06-00120" class="html-bibr">32</a>,<a href="#B33-minerals-06-00120" class="html-bibr">33</a>,<a href="#B34-minerals-06-00120" class="html-bibr">34</a>,<a href="#B35-minerals-06-00120" class="html-bibr">35</a>]. The inclusions in Tumanpınarı quartz and barite is shared by data from Fengjina, Farsash and Kızılcaören deposits containing Ba and F. (red point: quartz; blue point: barite).</p> Full article ">Figure 10
<p>Salinity vs. homogenization temperature (Th) plot of fluid inclusions from quartz and barite. Internal plot shows trend of increasing salinity with decreasing temperature in sample KB-6. This observed trend is associated with a positive increase of salinity due to streamloss under boiling conditions (red point: quartz; blue point: barite).</p> Full article ">Figure 11
<p>Temperature vs. depth diagram with boiling-point curves for H<sub>2</sub>O liquid (0 wt %) and for brine of different compositions given in wt % NaCl. The temperature at 0 m of each curve is the boiling point for the liquid at 1.013 bars (1.0 atm) load pressure [<a href="#B47-minerals-06-00120" class="html-bibr">47</a>].</p> Full article ">Figure 12
<p>Ore genesis model for Tumanpınarı.</p> Full article ">
4265 KiB  
Article
Iron Recovery from Discarded Copper Slag in a RHF Direct Reduction and Subsequent Grinding/Magnetic Separation Process
by Zhicheng Cao, Tichang Sun, Xun Xue and Zhanhua Liu
Minerals 2016, 6(4), 119; https://doi.org/10.3390/min6040119 - 3 Nov 2016
Cited by 23 | Viewed by 5092
Abstract
Studies on the direct reduction of carbon-bearing pellets made from discarded copper slag have been conducted in this paper. They include the influences of reduction coal content, limestone content, industrial sodium carbonate content, reduction temperature, reduction time and layers of carbon-bearing pellets on [...] Read more.
Studies on the direct reduction of carbon-bearing pellets made from discarded copper slag have been conducted in this paper. They include the influences of reduction coal content, limestone content, industrial sodium carbonate content, reduction temperature, reduction time and layers of carbon-bearing pellets on reduction effect. Finally, the optimum conditions have been obtained. The pilot scale experiment results show that the optimum conditions are the mass proportion of discarded copper slag, reduction coal, limestone and industrial sodium carbonate of 100:25:10:3, the reduction temperature of 1280 °C for the reduction time of 35 min, three layers (approximately 42 mm) of carbon-bearing pellets—this was the basis on which the pilot tests in a rotary hearth furnace (RHF) were conducted. The iron products obtained from the pilot tests under such conditions have an iron grade of 90.35% with an iron recovery rate of 89.70%. The mechanism research based on the analysis results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicates that fayalite (2FeO·SiO2) and magnetite (Fe3O4) in the copper slag are reduced into metallic Fe in the direct reduction (DR) process, and the mass and heat transfer become stronger from the bottom to the top layer of the pellets, resulting in a rising iron recovery rate. Full article
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<p>XRD patterns of the received copper slag.</p> Full article ">Figure 2
<p>Effect of reduction coal dosage on the DR process.</p> Full article ">Figure 3
<p>Effect of limestone dosage on the DR process.</p> Full article ">Figure 4
<p>Effect of industrial sodium carbonate dosage on the DR process.</p> Full article ">Figure 5
<p>Effect of reduction temperature on the DR process.</p> Full article ">Figure 6
<p>Effect of reduction time on the DR process.</p> Full article ">Figure 7
<p>Effect of carbon-containing pellets layers on the DR process.</p> Full article ">Figure 8
<p>XRD patterns of copper slag and metallization pellets.</p> Full article ">Figure 9
<p>SEM images and EDS analysis results of the metallization pellets. (<b>a</b>) layer 1; (<b>b</b>) layer 2; (<b>c</b>) layer 3; (<b>d</b>) layer 4.</p> Full article ">Figure 10
<p>XRD patterns (<b>a</b>) and SEM image (<b>b</b>) of the iron powder from the grinding/magnetic separation.</p> Full article ">
6327 KiB  
Article
Coupling Effect of Intruding Water and Inherent Gas on Coal Strength Based on the Improved (Mohr-Coulomb) Failure Criterion
by Yiyu Lu, Zhe Zhou, Zhaolong Ge, Xinwei Zhang and Qian Li
Minerals 2016, 6(4), 118; https://doi.org/10.3390/min6040118 - 2 Nov 2016
Cited by 8 | Viewed by 4625
Abstract
When employing hydraulic processes to increase gas drainage efficiency in underground coal mines, coal seams become a three-phase medium, containing water intruding into the coal pores with the inherent occurrence of gas. This can change the stress state of the coal and cause [...] Read more.
When employing hydraulic processes to increase gas drainage efficiency in underground coal mines, coal seams become a three-phase medium, containing water intruding into the coal pores with the inherent occurrence of gas. This can change the stress state of the coal and cause instability. This work studied the mechanical properties of coal containing water and gas and derived an appropriate failure criterion. Based on mixture theory of unsaturated porous media, the effective stress of coal, considering the interaction of water and gas, was analyzed, and the failure criterion established by combining this with the Mohr–Coulomb criterion. By introducing the stress factor of matrix suction and using fitted curves of experimentally determined matrix suction and moisture content, the relationships between coal strength, gas pressure, and moisture content were determined. To verify the established strength theory, a series of triaxial compression strength tests of coal containing water and gas were carried out on samples taken from the Songzao, Pingdingshan, and Tashan mines in China. The experimental results correlated well with the theoretical predictions. The results showed a linear decrease in the peak strength of coal with increasing gas pressure and an exponential reduction in peak strength with increasing moisture content. The strength theory of coal containing water and gas can become an important part of multiphase medium damage theory. Full article
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<p>Three-phase structure of coal containing water and gas.</p> Full article ">Figure 2
<p>Coal samples from Songzao, Pingdingshan, and Tashan mine.</p> Full article ">Figure 3
<p>(<b>a</b>) Sketch of suction calibration test; (<b>b</b>) Illustration of filter paper test.</p> Full article ">Figure 4
<p>Calibration curve for Whatman No. 42 filter paper (<span class="html-italic">w<sub>f</sub></span> &lt; 20%).</p> Full article ">Figure 5
<p>(<b>a</b>) Moisture contents of filter papers; (<b>b</b>) Fitted relationship curves of matrix suction and moisture content.</p> Full article ">Figure 6
<p>RLW-2000M rock mechanical testing system (Chaoyang Instrument Factory, Changchun, China) and deformeter (Teratech, Burlington, MA, USA).</p> Full article ">Figure 7
<p>Strength criterion shown in ((σ − <span class="html-italic">P</span><sub>g</sub>), τ) coordinates.</p> Full article ">Figure 8
<p>Relationship between (σ<sub>1</sub> − <span class="html-italic">P</span><sub>g</sub>) and (σ<sub>3</sub> − <span class="html-italic">P</span><sub>g</sub>): (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> Full article ">Figure 9
<p>Relationship between internal friction angle and moisture content.</p> Full article ">Figure 10
<p>Relationship between effective cohesion and matrix suction.</p> Full article ">Figure 11
<p>Relationship between peak strength and gas pressure: (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> Full article ">Figure 12
<p>Relationship between peak strength and moisture content: (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> Full article ">Figure 13
<p>(<b>a</b>) Mercury intrusion experiment curves; (<b>b</b>) Distribution curves of pore volume of coal samples.</p> Full article ">
7357 KiB  
Article
In Situ AFM Study of Crystal Growth on a Barite (001) Surface in BaSO4 Solutions at 30 °C
by Yoshihiro Kuwahara, Wen Liu, Masato Makio and Keisuke Otsuka
Minerals 2016, 6(4), 117; https://doi.org/10.3390/min6040117 - 2 Nov 2016
Cited by 10 | Viewed by 6472
Abstract
The growth behavior and kinetics of the barite (001) surface in supersaturated BaSO4 solutions (supersaturation index (SI) = 1.1–4.1) at 30 °C were investigated using in situ atomic force microscopy (AFM). At the lowest supersaturation, the growth behavior was mainly [...] Read more.
The growth behavior and kinetics of the barite (001) surface in supersaturated BaSO4 solutions (supersaturation index (SI) = 1.1–4.1) at 30 °C were investigated using in situ atomic force microscopy (AFM). At the lowest supersaturation, the growth behavior was mainly the advancement of the initial step edges and filling in of the etch pits formed in the water before the BaSO4 solution was injected. For solutions with higher supersaturation, the growth behavior was characterized by the advance of the <uv0> and [010] half-layer steps with two different advance rates and the formation of growth spirals with a rhombic to bow-shaped form and sector-shaped two-dimensional (2D) nuclei. The advance rates of the initial steps and the two steps of 2D nuclei were proportional to the SI. In contrast, the advance rates of the parallel steps with extremely short step spacing on growth spirals were proportional to SI2, indicating that the lateral growth rates of growth spirals were directly proportional to the step separations. This dependence of the advance rate of every step on the growth spirals on the step separations predicts that the growth rates along the [001] direction of the growth spirals were proportional to SI2 for lower supersaturations and to SI for higher supersaturations. The nucleation and growth rates of the 2D nuclei increased sharply for higher supersaturations using exponential functions. Using these kinetic equations, we predicted a critical supersaturation (SI ≈ 4.3) at which the main growth mechanism of the (001) face would change from a spiral growth to a 2D nucleation growth mechanism: therefore, the morphology of bulk crystals would change. Full article
(This article belongs to the Special Issue Nucleation of Minerals: Precursors, Intermediates and Their Use in Materials Chemistry)
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<p>(<b>a</b>–<b>c</b>) CMAFM deflection images of a (001) surface in 20µM, 40 µM, and 100 µM BaSO<sub>4</sub> solutions at 30 °C, respectively. In (<b>b</b>), sector-shaped 2D nuclei formed sporadically, while in (<b>c</b>) these nuclei formed rapidly and coalesced.</p> Full article ">Figure 2
<p>(<b>a</b>), (<b>b</b>), and (<b>d</b>) Sequential CMAFM deflection images of a (001) surface in a 40 µM BaSO<sub>4</sub> solution at 30 °C after 0 min, 14 min, and 51 min, respectively; each one-layer [010] step (step height = 7.2 Å) begins to split into two half-layer steps (step height = 3.6 Å) with different advance rates. Sector-shaped 2D nuclei were randomly formed, independent of the microtopography. In (<b>d</b>), the birth of a growth spirals that formed from a screw dislocation point is shown. (<b>c</b>) A comparison of (<b>a</b>) and (<b>b</b>), which are overlapped. The splitting process and advance rates of the steps are clearly demonstrated.</p> Full article ">Figure 3
<p>(<b>a</b>), (<b>b</b>), and (<b>d</b>) Sequential CMAFM deflection images of a (001) surface in pure water and in a 40 µM BaSO<sub>4</sub> solution at 30 °C after 4 min and 12 min, respectively. The [120] “fast retreat” and “slow retreat” half-layer steps during dissolution showed “fast advance” and “slow advance” behaviors, respectively, during growth. In (<b>d</b>), a new one-layer step was formed because the front of the half-layer step with the fast advance rate caught up with that of the immediately underlying half-layer step with the slow advance rate. (<b>c</b>) A comparison of (<b>a</b>) and (<b>b</b>), which are overlapped. The difference in the advance rate between the two [120] half-layer steps is clearly revealed.</p> Full article ">Figure 4
<p>(<b>a</b>–<b>c</b>) CMAFM deflection images of a (001) surface in 40 µM, 60 µM, and 100 µM BaSO<sub>4</sub> solutions at 30 °C, respectively, showing the growth spirals that formed from screw dislocations. The growth hillocks that likely formed from edge dislocations are also shown in (<b>a</b>). (<b>d</b>) CMAFM deflection image of a (001) surface in an 80 µM BaSO<sub>4</sub> solution at 30 °C showing growth spirals with a one-layer step sequence and regular step spacing.</p> Full article ">Figure 5
<p>(<b>a</b>) and (<b>b</b>) Sequential CMAFM deflection images of a (001) surface in a 40 µM BaSO<sub>4</sub> solution at 30 °C after 21 min and 30 min, respectively; (<b>c</b>) a comparison of (<b>a</b>) and (<b>b</b>), which are overlapped. The lateral spreading process and step advance rates of the 2D nuclei are clearly demonstrated. See <a href="#minerals-06-00117-f006" class="html-fig">Figure 6</a> for the growth of a 2D nucleus that is indicated by the white arrows.</p> Full article ">Figure 6
<p>Changes in the [120] (solid circulars) and curved (open circulars) step advance distances in the 2D nucleus shown in <a href="#minerals-06-00117-f005" class="html-fig">Figure 5</a> as a function of time. We began measuring the step advance distance 21 min (<a href="#minerals-06-00117-f005" class="html-fig">Figure 5</a>a) after the experiment began. The solid and open circular marks at 1803 s indicate the advance distances of the two steps in the 2D nucleus indicated by a white arrow in <a href="#minerals-06-00117-f005" class="html-fig">Figure 5</a>b.</p> Full article ">Figure 7
<p>Schematic diagrams showing the relationships between the advance and retreat behaviors of the half-layer [010] (<b>a</b>) and [120] (<b>b</b>) steps, the reduction and growth of the etch pits, and the growth of sector-shaped 2D islands during growth and dissolution on the barite (001) surface. The uppermost and lowermost half-layers show half-layer 1 (white) and half-layer 4 (black), respectively. The red and blue arrows show the directions and relative rates (slow and fast, respectively) of the advance and retreat of the steps.</p> Full article ">Figure 8
<p>Changes in the step or corner advance rates of the initial steps, 2D nuclei, and growth spirals as a function of the supersaturation index (<span class="html-italic">SI</span>). The initial half-layer fast (“f”) and slow (“s”) steps were indicated by red solid and open squares, respectively. The [120] and curved steps in 2D nuclei were shown as open and solid triangles, respectively. The [010] and [100] corners of the growth spirals were indicated by blue open and solid circles, respectively. The lateral growth rates of the growth spirals were proportional to <span class="html-italic">SI</span><sup>2</sup>, while the advance rates of the initial steps and the two steps in the 2D nuclei were proportional to the <span class="html-italic">SI</span>.</p> Full article ">Figure 9
<p>Changes in the lateral advance rates of parallel steps on the growth spirals as a function of the mean step separations of those that were proportional to <span class="html-italic">SI</span>. (<b>a</b>) Toward the [100] direction; (<b>b</b>) toward the [010] direction.</p> Full article ">Figure 10
<p>Changes in the growth rates toward the [001] direction of the growth spirals (<span class="html-italic">R</span><sub>sp</sub>) (blue solid circles) and 2D nuclei (<span class="html-italic">R</span><sub>nucl</sub>) (solid squares) as a function of the supersaturation index (<span class="html-italic">SI</span>). The growth rates (<span class="html-italic">R</span><sub>sp</sub>) of the growth spirals were likely proportional to <span class="html-italic">SI</span><sup>2</sup> for lower supersaturations (a solid line) and to <span class="html-italic">SI</span> for higher supersaturations (a blue dotted line). In contrast, the growth rates (<span class="html-italic">R</span><sub>nucl</sub>) of the 2D nuclei increased sharply at higher supersaturations (<span class="html-italic">SI</span> ≥ 3.8) and followed an exponential function (see text). It is expected that the main growth mechanism of the (001) face changes from a spiral growth to a 2D nucleation growth mechanism at an <span class="html-italic">SI</span>* of approximately 4.3.</p> Full article ">Figure 11
<p>Changes in the 2D nucleation rates as a function of the supersaturation index (<span class="html-italic">SI</span>). The 2D nucleation rates increased sharply at higher supersaturations (<span class="html-italic">SI</span> ≥ 3.8) and followed an exponential function, similar to the growth rates (<span class="html-italic">R</span><sub>nucl</sub>) of the 2D nuclei.</p> Full article ">
4277 KiB  
Article
Mo and Ni Removal from Drinking Water Using Zeolitic Tuff from Jordan
by Khalil M. Ibrahim, Hani N. Khoury and Randa Tuffaha
Minerals 2016, 6(4), 116; https://doi.org/10.3390/min6040116 - 2 Nov 2016
Cited by 17 | Viewed by 5189
Abstract
Mo and Ni metals could be hazardous in natural waters. The initial Mo and Ni concentration in the sampled domestic drinking water of north Jordan is 550 and 110 μg/L, respectively. The efficiency of using natural faujasite–phillipsite and phillipsite–chabazite tuffs in removing Mo [...] Read more.
Mo and Ni metals could be hazardous in natural waters. The initial Mo and Ni concentration in the sampled domestic drinking water of north Jordan is 550 and 110 μg/L, respectively. The efficiency of using natural faujasite–phillipsite and phillipsite–chabazite tuffs in removing Mo and Ni from contaminated drinking water was tested. Batch experiments using different weights of the adsorbent were conducted at different contact times to determine the optimum conditions. The maximal uptake capacity of Mo from drinking water was equivalent to 440–420 μg/g adsorbent. The maximum removal efficiency of Mo by faujasite–phillipsite, phillipsite–chabazite, and the modified surfactant phillipsite–chabazite tuffs were 80%, 76%, and 78%, respectively. The proportional relationship between contact time and removal efficiency of Ni from water samples was observed. The maximum removal efficiency of Ni by the zeolitic tuffs is up to 90% compared to the original groundwater sample. Full article
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<p>Location map of Wadi Al Arab Well Field [<a href="#B15-minerals-06-00116" class="html-bibr">15</a>].</p> Full article ">Figure 2
<p>Scanning electron micrographs showing: (<b>A</b>,<b>B</b>) radial aggregates of phillipsite; (<b>C</b>,<b>D</b>) rhombohedral chabazite crystal aggregates with penetration twinning.</p> Full article ">Figure 3
<p>Energy dispersive X-ray spectra: (<b>a</b>) Na-, K-, Ca-phillipsite and (<b>b</b>) Na-, Mg-, K-, Ca-chabazite crystals.</p> Full article ">Figure 4
<p>Eh–pH plot of the water samples in the system Mo-O-H. Mo = 10−10 m mole, 298.15 K, 105 Pa [<a href="#B38-minerals-06-00116" class="html-bibr">38</a>].</p> Full article ">Figure 5
<p>Mo and Ni removal efficiency by the natural faujasite–phillipsite tuff at different contact times.</p> Full article ">Figure 6
<p>Mo removal efficiency by the natural faujasite–phillipsite tuff at different water volumes.</p> Full article ">Figure 7
<p>Mo removal efficiency by the surfactant modified and non-modified phillipsite–chabazite tuff as a function of contact time.</p> Full article ">Figure 8
<p>Ni removal efficiency by the surfactant modified and non-modified phillipsite–chabazite tuff as a function of contact time.</p> Full article ">Figure 9
<p>Mo and Ni removal efficiency by the surfactant modified phillipsite–chabazite tuff at different sample weights.</p> Full article ">
41251 KiB  
Article
Merelaniite, Mo4Pb4VSbS15, a New Molybdenum-Essential Member of the Cylindrite Group, from the Merelani Tanzanite Deposit, Lelatema Mountains, Manyara Region, Tanzania
by John A. Jaszczak, Michael S. Rumsey, Luca Bindi, Stephen A. Hackney, Michael A. Wise, Chris J. Stanley and John Spratt
Minerals 2016, 6(4), 115; https://doi.org/10.3390/min6040115 - 28 Oct 2016
Cited by 20 | Viewed by 22066
Abstract
Merelaniite is a new mineral from the tanzanite gem mines near Merelani, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania. It occurs sporadically as metallic dark gray cylindrical whiskers that are typically tens of micrometers in diameter and up to a millimeter long, although [...] Read more.
Merelaniite is a new mineral from the tanzanite gem mines near Merelani, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania. It occurs sporadically as metallic dark gray cylindrical whiskers that are typically tens of micrometers in diameter and up to a millimeter long, although a few whiskers up to 12 mm long have been observed. The most commonly associated minerals include zoisite (variety tanzanite), prehnite, stilbite, chabazite, tremolite, diopside, quartz, calcite, graphite, alabandite, and wurtzite. In reflected polarized light, polished sections of merelaniite are gray to white in color, show strong bireflectance and strong anisotropism with pale blue and orange-brown rotation tints. Electron microprobe analysis (n = 13), based on 15 anions per formula unit, gives the formula Mo4.33Pb4.00As0.10V0.86Sb0.43Bi0.33Mn0.05 W0.05Cu0.03(S14.70Se0.30)Σ15, ideally Mo4Pb4VSbS15. An arsenic-rich variety has also been documented. X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy show that merelaniite is a member of the cylindrite group, with alternating centered pseudo-tetragonal (Q) and pseudo-hexagonal (H) layers with respective PbS and MoS2 structure types. The Q and H layers are both triclinic with space group C1 or C 1 ¯ . The unit cell parameters for the Q layer are: a = 5.929(8) Å; b = 5.961(5) Å; c = 12.03(1) Å; α = 91.33(9); β = 90.88(5); γ = 91.79(4); V = 425(2) Å3; and Z = 4. For the H layer, a = 5.547(9) Å; b = 3.156(4) Å; c = 11.91(1) Å; α = 89.52(9); β = 92.13(5); γ = 90.18(4); V = 208(2) Å3; and Z = 2. Among naturally occurring minerals of the cylindrite homologous series, merelaniite represents the first Mo-essential member and the first case of triangular-prismatic coordination in the H layers. The strongest X-ray powder diffraction lines [d in Å (I/I0)] are 6.14 (30); 5.94 (60); 2.968 (25); 2.965 (100); 2.272 (40); 1.829 (30). The new mineral has been approved by the IMA CNMNC (2016-042) and is named after the locality of its discovery in honor of the local miners. Full article
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<p>Optical photographs of merelaniite and some associated minerals: (<b>a</b>) 0.73-mm-long “cylindrical” whisker of merelaniite associated with tremolite, prehnite, and chabazite (private collection); (<b>b</b>) Whisker of merelaniite (0.9-mm section), associated with calcite, showing undulating diameters (Simon Harrison collection; sample 3941); (<b>c</b>) 2.5-mm section of a 5-mm-long merelaniite whisker (maximum diameter 0.18 mm) showing naturally unraveled ribbons, some partially enclosed in calcite, and associated with yellow prehnite (Simon Harrison collection; sample 3941).</p> Full article ">Figure 2
<p>Optical photographs of (<b>a</b>) 2.8-cm-tall quartz crystal with inclusions of merelaniite whiskers, also associated with chabazite crystals; (<b>b</b>) close-up of (a) showing merelaniite, graphite and an unidentified fan-shaped phase at the left of the image (~8 mm wide field-of-view). (A. E. Seaman Mineral Museum collection DM 31315; ex. Simon Harrison collection.).</p> Full article ">Figure 3
<p>Optical photograph of whiskers of merelaniite to 2.8 mm long associated with crystals of stilbite and graphite (sample 3665c), found in a small crevice on an 11-cm long alabandite crystal (private collection).</p> Full article ">Figure 4
<p>Scanning electron microscope (SEM) images of samples taken from the holotype specimen. (<b>a</b>) Cluster of merelaniite whiskers with one notably larger cylinder, associated with graphite. (Sample 3666i-190i.); (<b>b</b>) Section of a merelaniite-graphite cluster showing well-formed graphite crystals (Sample 3666i-190h.); (<b>c</b>,<b>d</b>) Merelaniite whiskers showing partially un-wound layers. (Sample 3666-196a.); (<b>e</b>,<b>f</b>) Individual whiskers showing conical ends and undulating diameters (Samples 3666i 190d and 3666 196c). Images taken using a Hitachi S-4700 field-emission SEM (Hitachi, Tokyo, Japan).</p> Full article ">Figure 4 Cont.
<p>Scanning electron microscope (SEM) images of samples taken from the holotype specimen. (<b>a</b>) Cluster of merelaniite whiskers with one notably larger cylinder, associated with graphite. (Sample 3666i-190i.); (<b>b</b>) Section of a merelaniite-graphite cluster showing well-formed graphite crystals (Sample 3666i-190h.); (<b>c</b>,<b>d</b>) Merelaniite whiskers showing partially un-wound layers. (Sample 3666-196a.); (<b>e</b>,<b>f</b>) Individual whiskers showing conical ends and undulating diameters (Samples 3666i 190d and 3666 196c). Images taken using a Hitachi S-4700 field-emission SEM (Hitachi, Tokyo, Japan).</p> Full article ">Figure 5
<p>SEM (Hitachi S-4700) images of merelaniite (Smithsonian Institution specimen NMNH 177015, reference 3323). (<b>a</b>) Merelaniite cylinder partially exposed from enclosing calcite; (<b>b</b>) Close-up image of the surface showing visible growth-layer steps; (<b>c</b>,<b>d</b>) The same merelaniite whisker after being broken, showing the curved lamellar (scroll) structure.</p> Full article ">Figure 6
<p>Reflected light microscope images of longitudinal sections of a polished merelaniite whisker (0.06 mm diameter) (Nikon Optiphot-Pol petrographic microscope): (<b>a</b>) Polarizer and analyzer both aligned vertically, parallel to the whisker axis; (<b>b</b>) Polarizer and analyzer both aligned vertically, perpendicular to the whisker axis; (<b>c</b>,<b>d</b>) Analyzer aligned vertically and polarizer slightly plus/minus un-crossed. It is not certain if the core of the whisker reflects more brightly due to a possible chemical difference between the core and outer region or is simply because the layers in the core are parallel to the polished surface. (A. E. Seaman Mineral Museum collection DM 31324, reference 3666ax2).</p> Full article ">Figure 7
<p>Reflected light microscope images of a polished axial section of a merelaniite whisker (0.09 mm diameter) (Nikon Optiphot-Pol petrographic microscope): (<b>a</b>) polarizer and analyzer both aligned horizontally; (<b>b</b>) crossed polarizers; and (<b>c</b>) slightly un-crossed polarizers. (A. E. Seaman Mineral Museum collection DM 31323, reference 3666cr2).</p> Full article ">Figure 8
<p>Representative Raman spectra, independently scaled and vertically shifted for clarity, from the surface of sample 3323, and from polished samples 3666ax2 and 3666cr2 using 633-nm and 785-nm incident radiation. The “3666cr2 middle” spectrum was taken from a region of the cross section shown in <a href="#minerals-06-00115-f007" class="html-fig">Figure 7</a> midway between the center and the surface. Spectra “3666ax2 rim” and “3666ax2 core” were taken from the longitudinal section of the whisker shown in <a href="#minerals-06-00115-f006" class="html-fig">Figure 6</a> from regions between the axis and the surface (rim), and from the brightly reflecting core, respectively.</p> Full article ">Figure 9
<p>Polished axial section of a merelaniite “whisker” used for chemical analysis. The red spots indicate the areas analyzed across the transect. Note the scroll-like form and the clear voids between the individual layers which are attributed to have led to the weight% totals being a little under 100%. Sample BM 2016,100; probe block P19396.</p> Full article ">Figure 10
<p>Reconstructed precession image of the [001] zone of a single merelaniite whisker (sample 3665LB) obtained with single-crystal X-ray diffraction.</p> Full article ">Figure 11
<p>Selected area electron diffraction pattern down (001) of merelaniite. Red and yellow circles refer to the <span class="html-italic">H</span> and <span class="html-italic">Q</span> pseudo-layers, respectively. (Sample 3666qx A grid A2.).</p> Full article ">Figure 12
<p>Selected area electron diffraction pattern down [010] of merelaniite. The <span class="html-italic">c</span>-stacking corresponding to ≈12 Å is shown. (Sample 3666qx A grid A2.).</p> Full article ">Figure 13
<p>High-resolution TEM image showing the modulated stacking along the <span class="html-italic">c</span>-axis of the PbS-type (<span class="html-italic">Q</span>) and MoS<sub>2</sub>-type (<span class="html-italic">H</span>) layers. Sample prepared by mechanical crushing of a whisker. The length of the scale bar is approximate. (Sample 3666qf.)</p> Full article ">Figure 14
<p>High-resolution transmission electron microscopy (TEM) image showing undulations in the PbS-type (<span class="html-italic">Q</span>) and MoS<sub>2</sub>-type (<span class="html-italic">H</span>) layers, which are stacked along the <span class="html-italic">c</span>-axis. Sample (3666qx A grid A2) prepared by ultramicrotome. The length of the scale bar is approximate.</p> Full article ">
1469 KiB  
Article
Selective Flotation of Calcite from Fluorite: A Novel Reagent Schedule
by Zhiyong Gao, Yuesheng Gao, Yiyang Zhu, Yuehua Hu and Wei Sun
Minerals 2016, 6(4), 114; https://doi.org/10.3390/min6040114 - 26 Oct 2016
Cited by 80 | Viewed by 7387
Abstract
Fluorite is an important strategic mineral. In general, fluorite ores will contain a certain amount of calcite gangue mineral. Thus, they need to be separated from each other. For an economic separation, a reverse flotation process is used to float calcite gangue from [...] Read more.
Fluorite is an important strategic mineral. In general, fluorite ores will contain a certain amount of calcite gangue mineral. Thus, they need to be separated from each other. For an economic separation, a reverse flotation process is used to float calcite gangue from fluorite. However, little information on the separation is available. In this study, a novel reagent schedule using citric acid (CA) as the depressant, sodium fluoride (NaF) as the regulator and sulfoleic acid (SOA) as the collector, was developed to separate calcite from fluorite. The results demonstrated a high selectivity for the flotation of calcite from fluorite using this new reagent schedule. The best selective separation for a single mineral and mixed binary minerals was obtained when 200 mg/L of NaF, 50 mg/L of CA, and 6 mg/L of SOA were used at pH 9. In addition, a batch flotation experiment was carried out using a run-of-mine feed material. Selective separation was achieved with 85.18% calcite removal while only 11.2% of fluorite was lost. An attempt was made to understand the effect of the new reagent schedule on the flotation of calcite. The results from both microflotation and bench scale flotation demonstrated a great potential for industrial application using this novel reagent schedule to upgrade fluorite ore. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>XRD spectrums of powder fluorite (<b>a</b>) and calcite (<b>b</b>) for flotation tests.</p> Full article ">Figure 2
<p>XFG flotation machine for a pure mineral flotation test.</p> Full article ">Figure 3
<p>Effect of SOA dosage (<b>a</b>) and pH (<b>b</b>) on flotation recoveries of calcite and fluorite minerals using SOA as the collector.</p> Full article ">Figure 4
<p>Effect of CA dosage (<b>a</b>) and pH (<b>b</b>) on flotation recoveries of calcite and fluorite minerals using SOA as the collector and CA as the depressant.</p> Full article ">Figure 5
<p>Effect of NaF dosage (<b>a</b>) and pH (<b>b</b>) on flotation recoveries of calcite and fluorite minerals using SOA as the collector and NaF as the depressant.</p> Full article ">Figure 6
<p>Effect of NaF dosage and order of addition of NaF and CA on flotation recoveries of calcite and fluorite minerals using SOA as the collector and NaF + CA as the depressant. (NaF + CA denotes the adding order of NaF and then CA; CA + NaF denotes the adding order of CA and then NaF).</p> Full article ">Figure 7
<p>Zeta potentials of fluorite (<b>a</b>) and calcite (<b>b</b>) in the absence and presence of different reagents.</p> Full article ">
11566 KiB  
Article
Analysis of Au-Ag Mineralization in the Caribou Base-Metal VMS Deposit, New Brunswick; Examination of Micro-Scale Inter- and Intra-Sulphide Distribution and Its Relation to Geometallurgy
by Joshua Wright, David R. Lentz, Steven Rossiter and Phil Garland
Minerals 2016, 6(4), 113; https://doi.org/10.3390/min6040113 - 21 Oct 2016
Cited by 8 | Viewed by 7983
Abstract
The Caribou Zn-Pb-Cu-Ag volcanogenic massive sulphide deposit located in northeast New Brunswick represents a significant base-metal resource in the Bathurst Mining Camp. Zinc, Pb and Cu are the primary resources that are being extracted from this deposit; however, Au and Ag are important [...] Read more.
The Caribou Zn-Pb-Cu-Ag volcanogenic massive sulphide deposit located in northeast New Brunswick represents a significant base-metal resource in the Bathurst Mining Camp. Zinc, Pb and Cu are the primary resources that are being extracted from this deposit; however, Au and Ag are important by-products that could help offset costs. This study used mineral liberation analysis supported further by in situ laser ablation inductively-coupled plasma-mass spectrometry methods to document variations in Au and Ag distribution between and within sulphide minerals. The variations in Ag and Au distribution provide critical inputs to the optimization of mineral processing design. The greatest influence on Au recovery at Caribou is the proportion of Au hosted in arsenopyrite and pyrite; consequently, considerable Au will report to the tailings. Silver recovery at Caribou is highly affected by the proportion of Ag hosted in galena and tetrahedrite-tennantite. Proximal to the vent complex, Ag values are primarily hosted in galena, whereas further from the vent complex, Ag values are likely primarily hosted in tetrahedrite-tennantite. Galena Ag values will report mostly to the Pb concentrate, while tetrahedrite-tennantite Ag values will report to the Cu concentrate. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
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Figure 1
<p>Simplified geology map of the Bathurst Mining Camp showing the location of the Caribou deposit and the five major rocks (modified from [<a href="#B1-minerals-06-00113" class="html-bibr">1</a>]). BMC, Bathurst Mining Camp.</p> Full article ">Figure 2
<p>Geology at 150 m below the surface, showing the relative locations of the six lenses and their relationship to the stratigraphic units of the Spruce Lake Formation and Boucher Brook Formation (modified from [<a href="#B7-minerals-06-00113" class="html-bibr">7</a>]).</p> Full article ">Figure 3
<p>Cross-section of the west limb of the Caribou deposit, looking 7° west of north, which shows the massive sulphide lenses relative to the stratigraphic units of the Spruce Lake Formation and Boucher Brook Formation (modified from [<a href="#B4-minerals-06-00113" class="html-bibr">4</a>]).</p> Full article ">Figure 4
<p>Reflected light photomicrograph showing the sulphide phases present in the L4-7-105.7 polished thin section. Ductile sulphides (Gn, Cp, Sp, Td-Tn) are concentrated in the interstices of coarser grained pyrite, whereas arsenopyrite is finely intergrown with the m.g. to c.g. porphyroblastic pyrite.</p> Full article ">Figure 5
<p>Reflected light photomicrograph from the L4-7-105.7 polished thin section. Pyrite textures transition with fine aggregate textures (with interstitial Sp) on the left and coarser aggregate textures progressing to the right in this image. Some Py, Cp, and Sp grains, as seen at the top centre, are isolated in the non-sulphide gangue minerals and are subhedral.</p> Full article ">Figure 6
<p>Reflected light photomicrograph from the L4-7-105.7 polished thin section. Tetrahedrite grains are commonly in contact with Cp, Sp, and Gn at grain boundaries, and occur frequently as veinlets or along grain boundaries within pyrite. Chalcopyrite has the same grain size distribution in gangue-rich areas as Py-rich areas, whereas this is not the same for Sp and Gn.</p> Full article ">Figure 7
<p>Reflected light photomicrograph from the L4-14-132.0 polished thin section. Chalcopyrite grains occur as disseminated grains within Py, Asp, and gangue, but are mostly concentrated in gangue-rich areas. Coarse-grained, inclusion free (relatively) Sp occurs mainly along pyrite-gangue zones.</p> Full article ">Figure 8
<p>Reflected light photomicrograph from L4-14-132.0 polished thin section. Subhedral Asp grains are isolated within Py aggregates, while coarse Asp euhedra are present at the grain boundaries of pyrite-Sp aggregates. Sphalerite is interstitial phase to Py-Asp assemblage.</p> Full article ">Figure 9
<p>Reflected light photomicrograph from the L4-14-132.0 polished thin section. Relatively large subhedral to euhedral Asp grains and finer subhedral Py grains are commonly in contact at grain boundaries with interstitial Sp. Sphalerite, Cp, and Gn occur primarily as interstitial phases between the grains of Asp and Py.</p> Full article ">Figure 10
<p>Silver versus Pb drill core interval assays for Lenses 3 (<span class="html-italic">n</span> = 33) and 4 (<span class="html-italic">n</span> = 23).</p> Full article ">
12097 KiB  
Article
Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts
by Cristiana L. Ciobanu, Nigel J. Cook, Christian Maunders, Benjamin P. Wade and Kathy Ehrig
Minerals 2016, 6(4), 112; https://doi.org/10.3390/min6040112 - 20 Oct 2016
Cited by 32 | Viewed by 7009
Abstract
This paper comprises a review of the rapidly expanding application of nanoscale mineral characterization methodology to the study of ore deposits. Utilising bismuth sulphosalt minerals from a reaction front in a skarn assemblage as an example, we illustrate how a complex problem in [...] Read more.
This paper comprises a review of the rapidly expanding application of nanoscale mineral characterization methodology to the study of ore deposits. Utilising bismuth sulphosalt minerals from a reaction front in a skarn assemblage as an example, we illustrate how a complex problem in ore petrology, can be approached at scales down to that of single atoms. We demonstrate the interpretive opportunities that can be realised by doing this for other minerals within their petrogenetic contexts. From an area defined as Au-rich within a sulphosalt-sulphide assemblage, and using samples prepared on a Focused Ion Beam–Scanning Electron Microscopy (SEM) platform, we identify mineral species and trace the evolution of their intergrowths down to the atomic scale. Our approach progresses from a petrographic and trace element study of a larger polished block, to high-resolution Transmission Electron Microscopy (TEM) and High Angle Annular Dark Field (HAADF) Scanning-TEM (STEM) studies. Lattice-scale heterogeneity imaged in HAADF STEM mode is expressed by changes in composition of unit cell slabs followed by nanoparticle formation and their growth into “veins”. We report a progressive transition from sulphosalt species which host lattice-bound Au (neyite, lillianite homologues; Pb-Bi-sulphosalts), to those that cannot accept Au (aikinite). This transition acts as a crystal structural barrier for Au. Fine particles of native gold track this progression over the scale of several hundred microns, leading to Au enrichment at the reaction front defined by an increase in the Cu gradient (several wt %), and abrupt changes in sulphosalt speciation from Pb-Bi-sulphosalts to aikinite. Atom-scale resolution imaging in HAADF STEM mode allows for the direct visualisation of the three component slabs in the neyite crystal structure, one of the largest and complex sulphosalts of boxwork-type. We show for the first time the presence of aikinite nanoparticles a few nanometres in size, occurring on distinct (111)PbS slabs in the neyite. This directly explains the non-stoichiometry of this phase, particularly with respect to Cu. Such non-stoichiometry is discussed elsewhere as defining distinct mineral species. The interplay between modular crystal structures and trace element behaviour, as discussed here for Au and Cu, has applications for other mineral systems. These include the incorporation and release of critical metals in sulphides, heavy elements (U, Pb, W) in iron oxides, the distribution of rare earth elements (REE), Y, and chalcophile elements (Mo, As) in calcic garnets, and the identification of nanometre-sized particles containing daughter products of radioactive decay in ores, concentrates, and tailings. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
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<p>(<b>a</b>) Ternary (Cu, Ag)-Bi-Pb plot showing bismuth sulphosalts of interest in this study. Known species in the bismuthinite derivative series (<b>left</b>) and lillianite homologous series (<b>right</b>) are located on the plot; (<b>b</b>–<b>e</b>) Projection (as marked) of crystal structures for selected sulphosalts illustrating the main building blocks. Atoms are shown as balls: dark grey (smaller)—Bi; light grey (larger)—Pb; red—Cu; green—Ag; yellow—S. Coordination polyhedra are shown using the same colour code for each atom type; (<b>b</b>) Aikinite crystal structure [<a href="#B66-minerals-06-00112" class="html-bibr">66</a>] is built by Pb<sub>2</sub>S<sub>6</sub> ribbons (dark grey) with 4 Cu atoms filling adjacent tetrahedral voids and BiS<sub>2+3</sub> in monocapped prismatic polyhedra (light grey); (<b>c</b>) Ag-Bi-substituted heyrovskyite [<a href="#B74-minerals-06-00112" class="html-bibr">74</a>]. The bicapped trigonal prismatic PbS<sub>6+2</sub> position is along the mirror planes (dark grey), the other cations (Ag, Pb, and Bi) are present in the octahedral MeS<sub>6</sub> sites (light grey). The homologue number (N = 7 for heyrovskyite) represents the average of the BiS<sub>6</sub> octahedra along (311)<sub>PbS</sub> directions counted on each side of the mirror planes (N = N1 + N2); (<b>d</b>) Neyite [<a href="#B75-minerals-06-00112" class="html-bibr">75</a>], showing the main building blocks as marked; (<b>e</b>) Cuproneyite [<a href="#B76-minerals-06-00112" class="html-bibr">76</a>], differing from neyite in that three types of Cu sites are present (linear, triangular, and asymmetrically tetrahedral), and the Ag position is occupied by Cu atoms.</p> Full article ">Figure 2
<p>Back Scatter Electron (BSE) images showing aspects of the Au-rich boundary along the reaction front, in which there is a sharp change from aikinite to Cu-Ag-bearing Pb-Bi-sulphosalts. Galena (Gn) is present in the matrix. (<b>a</b>) Gold concentrations (yellow) along the front from laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data [<a href="#B90-minerals-06-00112" class="html-bibr">90</a>]; (<b>b</b>) Detail showing inclusions of native gold along the reaction front correlating with Cu-enrichment (darker shades) in the Pb-Bi-sulphosalts.</p> Full article ">Figure 3
<p>BSE images (<b>a</b>–<b>c</b>) showing typical symplectitic and lamellar intergrowths between Bi-ss and galena; (<b>d</b>) (Cu, Ag)-(Bi, Sb)-Pb ternary diagram, showing the composition of sulphosalts and sulphides throughout the entire sample (polished block). Star symbols represent ideal phases. Square: aikinite; circles: heyrovskyite; triangles: Pb-Bi-sulphosalts as marked. Abbreviations: Ai—aikinite; B—Pb-Bi sulphosalt (bright); D—Pb-Bi sulphosalt (dark); both B and D are Cu-Ag-bearing; E—eskimoite; Gn—galena; Hey—heyrovskyite; Nuf—nuffieldite; O—ourayite; V—vikingite; T—treasurite; (1)—Ag-Bi-substituted heyrovskyite [<a href="#B74-minerals-06-00112" class="html-bibr">74</a>]; (2)—Ag-Bi-substituted N = 8 synthetic lillianite homologues [<a href="#B81-minerals-06-00112" class="html-bibr">81</a>].</p> Full article ">Figure 4
<p>Secondary Electron (SE) image showing the mapped areas (<b>top left</b>). Circle: area of FIB cuts (see <a href="#minerals-06-00112-f005" class="html-fig">Figure 5</a>b) and LA-ICP-MS element maps for an area along the ‘reaction front’ marked on <a href="#minerals-06-00112-f002" class="html-fig">Figure 2</a>a. See text for more explanations. Ai–aikinite; B–bright Pb-Bi-sulphosalt; D–dark Pb-Bi-sulphosalt; Cp–chalcopyrite; Gn–galena; Witt–wittichenite.</p> Full article ">Figure 5
<p>(<b>a</b>) Reduced areas of LA-ICP-MS maps (from <a href="#minerals-06-00112-f004" class="html-fig">Figure 4</a>) for elements of interest, showing the reaction zone used for the FIB-SEM study; (<b>b</b>) Secondary electron image showing the areas where FIB-cross sectioning and imaging were carried out, and from where the TEM samples were extracted. White lines show the locations of FIB-cuts and their number (foils 1–5); (<b>c</b>) Compositional plot showing sulphosalts from the area with the FIB-cuts in (<b>b</b>). Stars-ideal compositions; squares - aikinite; triangles–Pb-Bi-sulphosalts. Stars labelled (1) and (2) represent phases as given in <a href="#minerals-06-00112-f001" class="html-fig">Figure 1</a>a and <a href="#minerals-06-00112-f003" class="html-fig">Figure 3</a>d. Abbreviations: Ai—aikinite; Cp—chalcopyrite; CNe—cuproneyite; Cu-CNE—Cu-enriched cuproneyite; Cos—cosalite; Gb—galenobismuthite; Hey—heyrovskyite; Gus—gustavite; Kr—krupkaite; Lil—lillianite.</p> Full article ">Figure 6
<p>Secondary Electron images showing details of the FIB-cuts lifted and placed on Cu grids (<b>a</b>–<b>f</b>); and TEM images of foils 1 and 2 (<b>g</b>–<b>h</b>); Note the association between alabandite (Abn) and native gold (Au) along fractures (<b>a</b>–<b>b</b>) and trails (<b>c</b>); Abundant, finest grains of native gold in aikinite (<b>d</b>); Note their distribution at the contact between aikinite and dark Bi-ss; (<b>e</b>,<b>f</b>) Details of fine particles of native gold at the contact between galena and alabandite. See the text for additional explanation. Letters A, B in (<b>g</b>) and (i), (ii) in (<b>h</b>) define areas of interest discussed in the text.</p> Full article ">Figure 7
<p>Bright Field (BF) HR-TEM images and SAEDs (on zone axes as marked) showing associations between aikinite (Ai; <b>a</b>–<b>c</b>) and the bright Pb-Bi-sulphosalt (phase B) identified as N = 8 lillianite homologue (<sup>8</sup>L; <b>d</b>–<b>f</b>). Note the fine-grained aggregate of B at the boundary to aikinite (<b>a</b>,<b>b</b>), and the high contrast between different slabs typical of twinning in lillianite homologues. Note the presence of streaks along <span class="html-italic">c*</span> and equivalent directions indicating disorder in <sup>8</sup>L. See text for additional explanation.</p> Full article ">Figure 8
<p>BF HR-TEM images and SAEDs (on zone axes as marked) showing details of Pb-Bi sulphosalt (D) (<b>a</b>,<b>b</b>) indexed as neyite (Ney); and relationships with Pb-Bi-sulphosalt (B) identified as <sup>8</sup>L (<b>c</b>,<b>d</b>); Note the step-wise offsets at the contact between the two sulphosalts (<b>c</b>).</p> Full article ">Figure 9
<p>BF HR-TEM images showing replacement relationships between aikinite (Ai) and the two Pb-Bi-sulphosalts (D and B) (<b>a</b>,<b>b</b>,<b>d</b>); defects along phase boundaries (<b>c</b>) and inclusions of native gold (<b>e</b>) and hessite Hs; (<b>f</b>) at grain boundaries. See the text for additional explanation.</p> Full article ">Figure 10
<p>HAADF STEM images showing patterns realised by building blocks in the crystal structure of neyite down to the [010] zone axis (dark Pb-Bi-sulphosalt (phase D) in area (i) of foil 2; <a href="#minerals-06-00112-f006" class="html-fig">Figure 6</a>h). Note the “zig-zag” pattern expressed as contrast variation in the ‘rhombic’ motifs forming parallel strips in (<b>a</b>); In (<b>b</b>) the structural motifs are shown by different orientations of the heavy atoms (bright dots; Bi, Pb), and dark contrast for units formed by lighter elements (Ag and Cu). Note the transitional, variable contrast for the rhombic motifs but the preservation of the geometrical outline. See the text for additional explanation.</p> Full article ">Figure 11
<p>(<b>a</b>) EDS profile across one of the dark ‘rhombic’ motifs showing that it is richer in Cu; (<b>b</b>) EDS spectra for points along the profile in (<b>a</b>), showing the relative variation in concentrations of the main elements for spots outside and inside the motif. The high Cu peak is due to interference with the Cu grid. Note that the Ag peak is barely visible for neyite (concentration threshold for the detector?); (<b>c</b>) EDS elemental maps for one of rhombic motifs (rectangle on HAADF STEM image corner left), showing that it is Cu-rich, and Bi-Pb-poor relative to the enclosing matrix.</p> Full article ">Figure 12
<p>Crystal structural slabs in the dark Pb-Bi-sulphosalt (D), identified from the HAADF STEM image in (<b>a</b>) and, in (<b>b</b>); an enlargement of the white rectangle area in (<b>a</b>); matching the neyite structure [<a href="#B75-minerals-06-00112" class="html-bibr">75</a>]; (<b>c</b>) down to the [010] zone axis. The slabs are outlined by: (111)<sub>PbS</sub>—dark blue and grey shading; (100)<sub>PbS</sub>—light blue and grey shading. Note the excellent correlation between the number of heavy atoms (Pb, Bi as white dots on the HAADF STEM images and small and larger grey balls on the sketch in (<b>c</b>)). The small rhombs in red correspond to Cu whereas the green rectangles show Ag positions. The purple shading in (<b>b</b>), and outlines in (<b>c</b>), show two small sheared blocks alternating with the Ag-bearing slabs (green outline on (<b>c</b>)). Note that these are dark on the HAADF STEM images (<b>a</b>,<b>b</b>), suggesting that they host atoms lighter than Bi and Pb considered in the structural model. See the text for additional explanation.</p> Full article ">Figure 13
<p>HAADF STEM images (<b>a</b>,<b>b</b>) and EDS spectra (<b>c</b>) showing the replacement of neyite (Pb-Bi-sulphosalt B) by aikinite in area (ii) of foil 2 (<a href="#minerals-06-00112-f006" class="html-fig">Figure 6</a>h). Neyite is tilted down to the [010] zone axis; aikinite shows lattice fringes down to [11-1] zone axis—see <a href="#minerals-06-00112-f014" class="html-fig">Figure 14</a>b. (<b>a</b>) Nanometre-sized vein of aikinite with a kink-like trajectory. Note the darker margins, as well as the protrusions within neyite; (<b>b</b>) Nanoparticles of aikinite (NPs) with typical 1–3 nm size, centred on the (111)<sub>PbS</sub> slabs in the neyite structure. Note that they have round shapes; (<b>c</b>) EDS spectra representing the matrix neyite and vein aikinite, showing the relative differences for the peaks of the main elements (Bi and Pb). The high Cu peak is due to interference from the Cu grid. Note that the Ag peak is not visible for neyite (concentration threshold for the detector?).</p> Full article ">Figure 14
<p>HAADF STEM images (<b>a</b>,<b>b</b>) and EDS spectra (<b>c</b>,<b>d</b>) of N = 8 lillianite homologue and aikinite in foil 1, area A (<a href="#minerals-06-00112-f006" class="html-fig">Figure 6</a>). Fast Fourier Transform (FFT) in the inset of (<b>b</b>) indicates aikinite on the [11-1] zone axis. Lillianite shows dark contrast lamellae in (<b>a</b>). Note the presence of a distinct Ag peak for the lillianite homologue in (<b>c</b>) and the absence of such a peak in (<b>d</b>). The high Cu peak is due to interference from the Cu grid.</p> Full article ">
15671 KiB  
Review
Trace Element Analysis of Minerals in Magmatic-Hydrothermal Ores by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry: Approaches and Opportunities
by Nigel Cook, Cristiana L. Ciobanu, Luke George, Zhi-Yong Zhu, Benjamin Wade and Kathy Ehrig
Minerals 2016, 6(4), 111; https://doi.org/10.3390/min6040111 - 20 Oct 2016
Cited by 139 | Viewed by 17186
Abstract
Laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) has rapidly established itself as the method of choice for generation of multi-element datasets for specific minerals, with broad applications in Earth science. Variation in absolute concentrations of different trace elements within common, widely distributed phases, [...] Read more.
Laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) has rapidly established itself as the method of choice for generation of multi-element datasets for specific minerals, with broad applications in Earth science. Variation in absolute concentrations of different trace elements within common, widely distributed phases, such as pyrite, iron-oxides (magnetite and hematite), and key accessory minerals, such as apatite and titanite, can be particularly valuable for understanding processes of ore formation, and when trace element distributions vary systematically within a mineral system, for a vector approach in mineral exploration. LA-ICP-MS trace element data can assist in element deportment and geometallurgical studies, providing proof of which minerals host key elements of economic relevance, or elements that are deleterious to various metallurgical processes. This contribution reviews recent advances in LA-ICP-MS methodology, reference standards, the application of the method to new mineral matrices, outstanding analytical uncertainties that impact on the quality and usefulness of trace element data, and future applications of the technique. We illustrate how data interpretation is highly dependent on an adequate understanding of prevailing mineral textures, geological history, and in some cases, crystal structure. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
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<p>LA-ICP-MS maps of mm-sized pyrite grains displaying micron-scale oscillatory zoning. Note that, whereas As, Co and Ni occur in solid solution, within the pyrite grains and display concentric zoning, the map for Ga shows that element associated with microscopic silicate inclusions in the pyrite cores, and the maps for Ag, Bi and W show these elements are distributed not within the zones but in crosscutting microfractures. The mapped area is shown as a backscatter electron image at upper left. Scales in counts-per-second. Measured isotopes: <sup>56</sup>Fe, <sup>69</sup>Ga, <sup>75</sup>As, <sup>59</sup>Co, <sup>60</sup>Ni, <sup>109</sup>Ag, <sup>2095</sup>Bi, <sup>182</sup>W.</p> Full article ">Figure 2
<p>(<b>a</b>) Secondary electron (SE) image of fine-grained rusty hematite (Olympic Dam; OD). Note size of laser spot relative to grain size; (<b>b</b>) time-resolved depth profile showing ‘flat’ signals for most elements interpreted to he hosted in the hematite lattice; (<b>c</b>) chondrite-normalized REY fractionation trends for this type of hematite; note coherent, readily interpretable trends; (<b>d</b>) SE image of coarser hematite aggregate containing inclusions of monazite (see <a href="#minerals-06-00111-f003" class="html-fig">Figure 3</a>a–d; OD); (<b>e</b>) time-resolved depth profile for spot in (d) showing rough signals indicative of inclusions during ablation. This hematite is not zoned with respect to trace elements; (<b>f</b>) chondrite-normalized REY fractionation trends for the hematite in the same sample shown in (d,e) separated by grain size. There is an increase in ΣREY with the fine-grained hematite in the matrix, which shows similar REY profiles with the rusty hematite. Note however their wider range relatively to the finest, rusty hematite in (c).</p> Full article ">Figure 3
<p>Mineral inclusions and porosity present in hematite from samples shown in <a href="#minerals-06-00111-f002" class="html-fig">Figure 2</a>a,b SE images showing location of FIB-cut next to LA-ICP-MS spot in rusty hematite (<b>a</b>); and the presence of pores and inclusions within the sub-µm size lamellae (<b>b</b>); (<b>c</b>) FIB-Scanning Transmission Electron Image in Bright Field mode showing trails of sub-µm inclusions of monazite (Mnz) close to the grain boundary; (<b>d</b>) FIB-EDS maps of monazite grains in (c); (<b>e</b>,<b>f</b>) SE images showing distribution of pores and their morphology in hematite from (c) obtained after FIB-cross sectioning through the polished block; (<b>g</b>) Sub-µm-sized inclusion of hematite (Hm) in florencite (Flor) from a high-grade bornite (Bn)-bearing sample at OD. Ser—sericite.</p> Full article ">Figure 4
<p>Comparison between quantitative LA-ICP-MS trace element maps (Ag, Sb and Cd, ppm scales) of a galena (light grey)–sphalerite (dark grey)–chalcopyrite (yellow) assemblage with spot analyses (in ppm) immediately adjacent to the mapped area. An average value for sulfur was used as the internal standard to accommodate the three distinct minerals.</p> Full article ">Figure 4 Cont.
<p>Comparison between quantitative LA-ICP-MS trace element maps (Ag, Sb and Cd, ppm scales) of a galena (light grey)–sphalerite (dark grey)–chalcopyrite (yellow) assemblage with spot analyses (in ppm) immediately adjacent to the mapped area. An average value for sulfur was used as the internal standard to accommodate the three distinct minerals.</p> Full article ">Figure 5
<p>BSE images (<b>a</b>)–(<b>c</b>) showing textural details of a radial aggregate of hematite hosted in bornite (white in (a,b)) from Olympic Dam. Note the zoning and porosity within individual lamellae depicted on the BSE images in (b) and (c), respectively. (<b>d</b>) LA-ICP-MS element maps of the hematite aggregate shown in (a); note good correspondence between textures on BSE images and specific groups of elements, i.e., zoning with respect of U, Pb, Mo and W (middle parts of lamellae), and enrichment in HFSE in the porous, marginal parts of the same lamellae. Scales in counts-per-second (×10<sup>3</sup> except for Ce and Nb). Measured isotopes: <sup>238</sup>U, <sup>206</sup>Pb, <sup>95</sup>Mo, <sup>182</sup>W, <sup>140</sup>Ce, <sup>93</sup>Nb, <sup>51</sup>V, <sup>47</sup>Ti.</p> Full article ">Figure 6
<p>BSE images (<b>a</b>–<b>d</b>) showing the textures of coarser, sub-rounded grain of hematite from the same sample as in <a href="#minerals-06-00111-f005" class="html-fig">Figure 5</a> (aggregate of acicular lamellae). Note the presence of µm to sub-µm size REE-mineral inclusions (<b>a</b>,<b>b</b>), as well as the abundance of pores throughout most of the grain (<b>c</b>); (<b>d</b>) channel-like sub-texture shows a correlation between high concentrations of Al with low concentrations of W and V; (<b>e</b>) LA-ICP-MS element maps of reworked, hematite resulting in a depletion of granitophile and HFSE trace elements. Note the correlation between the maps for U, Y and Er, showing the presence of REE inclusions in (<b>a</b>,<b>b</b>), as well as the channel-like patterns on the Al, W, V maps correlating with the texture in (<b>d</b>) containing micron-scale inclusions of U- and REE-minerals, extensive porosity and chemically-defined channel textures. Concentration scales in counts-per-second (×10<sup>3</sup>). Measured isotopes: <sup>238</sup>U, <sup>89</sup>Y, <sup>166</sup>Er, <sup>27</sup>Al, <sup>182</sup>W, <sup>51</sup>V.</p> Full article ">Figure 7
<p>LA-ICP-MS element maps of zoned skarn garnet illustrating the abundance and diversity of trace elements present within the garnet structure. Scales in counts per second (×10<sup>3</sup>). Measured isotopes: <sup>118</sup>Sn, <sup>182</sup>W, <sup>27</sup>Al, <sup>89</sup>Y, <sup>75</sup>As, <sup>56</sup>Fe, <sup>238</sup>U, <sup>47</sup>Ti, <sup>9</sup><sup>0</sup>Zr, <sup>45</sup>Sc, <sup>51</sup>V, <sup>14</sup><sup>0</sup>Ce, <sup>146</sup>Nd, <sup>93</sup>Nb, <sup>165</sup>Ho, <sup>175</sup>Lu, <sup>178</sup>Hf.</p> Full article ">
8556 KiB  
Article
Mapping of Sulfur Isotopes and Trace Elements in Sulfides by LA-(MC)-ICP-MS: Potential Analytical Problems, Improvements and Implications
by Zhi-Yong Zhu, Nigel J. Cook, Tao Yang, Cristiana L. Ciobanu, Kui-Dong Zhao and Shao-Yong Jiang
Minerals 2016, 6(4), 110; https://doi.org/10.3390/min6040110 - 20 Oct 2016
Cited by 93 | Viewed by 10277
Abstract
Constraints on accurate quantitative trace element and sulfur (S) isotope analysis of sulfide minerals, especially pyrite, by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remain imperfectly understood at the present time. Mapping of S isotope distributions within a complex sample containing several minerals [...] Read more.
Constraints on accurate quantitative trace element and sulfur (S) isotope analysis of sulfide minerals, especially pyrite, by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remain imperfectly understood at the present time. Mapping of S isotope distributions within a complex sample containing several minerals requires an evaluation of the matrix effects and accuracy. Here, we apply LA-Q(quadrupole)-ICP-MS and LA-MC(multiple collector)-ICP-MS methods to analyze trace elements and S isotopes in sulfides. Spot analysis of S isotopes was conducted to evaluate the influence of matrix effects. The matrix effects from siderite and magnetite are deemed to be negligible in mapping analysis at the precision of this study. Both Fe and S were used as internal standard elements to normalize trace element concentrations in pyrite. Fe proved to be the better choice because the normalized counts per second ratio of trace elements with Fe is much more stable than if using S. A case study of a sulfide sample from the Chengmenshan Cu deposit, Jiangxi Province, South China, demonstrates the potential of combined S isotope and trace element mapping by LA-(MC)-ICP-MS. The results suggest that this deposit underwent multi-stage ore formation. Elements, including Au and Ag, were hosted in early-stage pyrite but were re-concentrated into multi-component sulfide assemblages during a late-stage hydrothermal event, which also led to crosscutting veins containing pyrite largely devoid of trace elements, except Se. Combining in situ S isotope and trace element analysis on the same sample represents a powerful tool for understanding ore-forming processes. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
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<p>Photomicrographs in reflected light showing petrographic aspects of the studied sample. (<b>a</b>) Overview of the hand specimen, the early stage pyrite (Py-e) is associated with siderite-magnetite-dominant matrix that was crosscut by late-stage pyrite veins (Py-l); (<b>b</b>) the main-ore stage with multi-component sulfide assemblage including chalcopyrite (Ccp), sphalerite (Sph), Bornite (Bn) and pyrite (Py-a); (<b>c</b>) early pyrite (Py-e) hosted interstitially within the siderite (Sd)-magnetite (Mag) matrix and has possibly replaced marcasite (Mrc); relict marcasite can be seen within Py-e; (<b>d</b>) replacements of siderite by magnetite within the sample matrix.</p> Full article ">Figure 2
<p>Plot showing variation in normalized CPS for Co, Ni, Ge and Se, using Fe and S as the internal standard, respectively. The analysis shown was conducted on a single crystal pyrite in spot mode. Carrier gas flow was changed to control the amount of ablated particles into the ICP-MS.</p> Full article ">Figure 3
<p><span class="html-italic">R<sub>x</sub></span> and <span class="html-italic">R<sub>y</sub></span> are horizontal and vertical spatial resolutions respectively. Each square represents a laser pulse. To make the laser cover the entire surface of the mapped area, raster velocity (<span class="html-italic">V</span>) should not larger than the product of laser repetition rate (<span class="html-italic">f</span>) and spot size (<span class="html-italic">d</span>).</p> Full article ">Figure 4
<p>LA-Q-ICP-MS element maps. The elements are arranged in alphabetical orders. Se, Co, Ni and Co/Ni ratios are inhomogeneous in Py-l. Ag, As, Au, Bi, Cd, Co, Cu, Mo, Ni, Pb, Re, Se, Si, Te and Zn are hosted within the sulfide assemblages, which are always distributed around Py-l, or in the fracture. Py-l is barren of these metals, but is relatively enriched in Pt and Se. The resolution of these images is not high enough to distinguish Py-e from siderite and magnetite. Spot results are shown in <a href="#minerals-06-00110-f005" class="html-fig">Figure 5</a>. The area mapped is approximately the same as that indicated by the red square in <a href="#minerals-06-00110-f001" class="html-fig">Figure 1</a>a. Sulfur isotopes are also mapped in this same area. The sample block was carefully polished after S isotope analysis in preparation for trace element mapping.</p> Full article ">Figure 5
<p>Concentrations of 16 selected elements in the three generations of pyrite using spot analysis mode. Precious metals are more enriched in the sulfide assemblages than Py-e, Py-l is barren of precious metals, but enriched in Se relative to Py-e. We excluded two spots (see diagram for Au) after checking the time-resolved spectra data, where the extremely abnormal peaks in the <sup>197</sup>Au signal are very likely caused by the presence of included native gold.</p> Full article ">Figure 6
<p>(<b>a</b>) Reflected-light image of mapped area and (<b>b</b>) LA-MC-ICP-MS S isotope map. The vein appearing bright on both the image and the map is Py-l, whereas the darker areas are the matrix dominated by siderite and magnetite but also containing interstitial Py-e and Py-a. Note that the S-isotope map shows that the S isotope signature of Py-l is about 4‰ heavier than Py-e and Py-a.</p> Full article ">Figure 7
<p>Comparison of S-isotope data from mapping and spot analysis. (<b>a</b>) Statistic results of mapping analysis in the <a href="#minerals-06-00110-f006" class="html-fig">Figure 6</a>b; (<b>b</b>) Spot analysis results. There is no systematic drift between the statistical results from the two methods. Published data (obtained via traditional bulk analysis methods [<a href="#B40-minerals-06-00110" class="html-bibr">40</a>]) are also marked. These cover only the coarser Py-l. The fine-grained Py-e in the matrix had been observed but was not analyzed previously.</p> Full article ">
8077 KiB  
Article
Recovering Y and Eu from Waste Phosphors Using Chlorination Roasting—Water Leaching Process
by Mingming Yu, Shuya Pang, Guangjun Mei and Xiaodong Chen
Minerals 2016, 6(4), 109; https://doi.org/10.3390/min6040109 - 19 Oct 2016
Cited by 14 | Viewed by 4005
Abstract
Recovering Y and Eu from waste phosphors using chlorination roasting followed by a water leaching process was investigated in this study. Firstly, by chlorination roasting and water leaching, Y and Eu elements present in waste phosphors were efficiently extracted into a leach solution. [...] Read more.
Recovering Y and Eu from waste phosphors using chlorination roasting followed by a water leaching process was investigated in this study. Firstly, by chlorination roasting and water leaching, Y and Eu elements present in waste phosphors were efficiently extracted into a leach solution. Secondly, the majority of the impurities in the solution can be removed by adjusting the pH to 4.5 using a Na2S and NH3·H2O solution. Thirdly, the rare earths can be precipitated afterwards by adding a H2C2O4 solution and adjusting the pH to 2.0. Then rare earth oxides (REOs) can be obtained after calcining at 800 °C for 1 h. The characterization study of the waste phosphors and the rare earth oxide products was performed by XRD, XRF, and SEM-EDS analysis to determine the phase and morphological features. Influences of the factors, such as roasting temperatures and time, the addition of ammonium chloride on the roasting of waste phosphors, as well as the pH and the amount of oxalates on the precipitation of Y and Eu, were investigated. The maximum grade (99.84%) of mixed rare earth oxides and recovery rate (87.35%) of Y and Eu were obtained at the optimized conditions. Full article
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<p>XRD analysis of waste phosphor.</p> Full article ">Figure 2
<p>SEM-EDS analysis of waste phosphors.</p> Full article ">Figure 3
<p>TG–DSC curves of waste phosphors mixed with NH<sub>4</sub>Cl (<span class="html-italic">m</span>(ore):<span class="html-italic">m</span>(NH<sub>4</sub>Cl) = 1:4).</p> Full article ">Figure 4
<p>Effect of roasting temperature on the leaching rate of the rare earths.</p> Full article ">Figure 5
<p>Effect of roasting time on the leaching rate of the rare earths.</p> Full article ">Figure 6
<p>Effect of NH<sub>4</sub>Cl addition on the leaching rate of Y and Eu.</p> Full article ">Figure 7
<p>SEM-EDS analysis of the leach residue.</p> Full article ">Figure 8
<p>XRD analysis of waste phosphor after roasting (<b>a</b>); and water leaching (<b>b</b>).</p> Full article ">Figure 9
<p>Effect of pH on the concentration of Al, Fe, Pb, and Fe in the leach solution.</p> Full article ">Figure 10
<p>Effect of pH on the concentration of Y and Eu in the leach solution.</p> Full article ">Figure 11
<p>Effect of oxalate addition on the precipitation rate of RE elements.</p> Full article ">Figure 12
<p>Effect of pH value on the precipitation ratios of RE elements.</p> Full article ">Figure 13
<p>SEM photograph of REOs.</p> Full article ">Figure 14
<p>The XRD analysis of REOs.</p> Full article ">
6280 KiB  
Article
Platinum-Group Minerals and Other Accessory Phases in Chromite Deposits of the Alapaevsk Ophiolite, Central Urals, Russia
by Federica Zaccarini, Evgeny Pushkarev, Giorgio Garuti and Igor Kazakov
Minerals 2016, 6(4), 108; https://doi.org/10.3390/min6040108 - 19 Oct 2016
Cited by 21 | Viewed by 6989
Abstract
An electron microprobe study has been carried out on platinum-group minerals, accessory phases, and chromite in several chromite deposits of the Alapaevsk ophiolite (Central Urals, Russia) namely the Bakanov Kluch, Kurmanovskoe, Lesnoe, 3-d Podyony Rudnik, Bol’shaya Kruglyshka, and Krest deposits. These deposits occur [...] Read more.
An electron microprobe study has been carried out on platinum-group minerals, accessory phases, and chromite in several chromite deposits of the Alapaevsk ophiolite (Central Urals, Russia) namely the Bakanov Kluch, Kurmanovskoe, Lesnoe, 3-d Podyony Rudnik, Bol’shaya Kruglyshka, and Krest deposits. These deposits occur in partially to totally serpentinized peridotites. The microprobe data shows that the chromite composition varies from Cr-rich to Al-rich. Tiny platinum-group minerals (PGM), 1–10 µm in size, have been found in the chromitites. The most abundant PGM is laurite, accompanied by minor cuproiridsite and alloys in the system Os–Ir–Ru. A small grain (about 20 μm) was found in the interstitial serpentine of the Bakanov Kluch chromitite, and its calculated stoichiometry corresponds to (Ni,Fe)5P. Olivine, occurring in the silicate matrix or included in fresh chromite, has a mantle-compatible composition in terms of major and minor elements. Several inclusions of amphibole, Na-rich phlogopite, and clinopyroxene have been identified. The bimodal Cr–Al composition of chromite probably corresponds to a vertical distribution in the ophiolite sequence, implying formation of Cr-rich chromitites in the deep mantle, and Al-rich chromitites close to the Moho-transition zone, in a supra-subduction setting. The presence of abundant hydrous silicate inclusions, such as amphibole and phlogopite, suggests that the Alapaevsk chromitites crystallized as a result of the interaction between a melt enriched in fluids and peridotites. Laurite and cuproiridsite are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at high temperatures. The sulfur fugacity was relatively high to allow the precipitation of Ir-bearing sulfides, but below the Os–OsS2 buffer. The alloys in the system Os–Ir–Ru are classified as secondary PGM, i.e., formed at low temperature during the serpentinization process. The (Ni,Fe)5P phase is the first occurrence of a Ni-phosphide in terrestrial samples. Its composition indicates that it may be a new mineral. However, the small size has, so far, prevented a crystallographic study to support this conclusion. Full article
(This article belongs to the Special Issue Mineral Deposit Genesis and Exploration)
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<p>The distribution of mafic–ultramafic complexes in the Urals (excluding Circumpolar and Polar sectors of the Urals) (simplified after [<a href="#B2-minerals-06-00108" class="html-bibr">2</a>]). I—dunite-clinopyroxenite-gabbro massifs of the Ural Platinum Belt; II—ophiolite complexes. Eastern ophiolite belt: 1—Alapaevsk massif; 2—Ostaninsky massif; 3—Rezhevskoy massif; 4—Bazhenovsky massif; 5—Kluchevskoy massif. Rectangle shows the northern end of the Eastern ophiolite belt where the Alapaevsk massif is located.</p> Full article ">Figure 2
<p>Simplified geological map of the Alapaevsk ophiolite massif showing the location of the chromite deposits, redrawn after [<a href="#B10-minerals-06-00108" class="html-bibr">10</a>].</p> Full article ">Figure 3
<p>Overview of the chromite deposits of the Alapaevsk massif, Central Urals. Kurmanovskoe chromite deposit: (<b>A</b>) general view of open pit and (<b>B</b>) the location of the studied sample; Krest chromite deposit: (<b>C</b>) the exploration trench and (<b>D</b>) vertical ore body of massif chromite in dunite; (<b>E</b>) open pit of the Bol’shaya Kruglyshka chromite deposit; (<b>F</b>) open pit of the 3-d Podyony Rudnik chromite deposit; (<b>G</b>) open pit of the Lesnoe chromite deposit. Arrows indicate sample locations.</p> Full article ">Figure 4
<p>Different textural types of the chromite ores from the Alapaevsk massif, Central Urals. Chromite ore of the Kurmanovskoe deposit (number IV on map) (<b>A</b>–<b>C</b>). (<b>A</b>) Banded (sample PE1852) and massive (samples PE1855-1 and PE1856); (<b>B</b>) ores disseminated ore; (<b>C</b>) small schlieren of massive chromitite; (<b>D</b>) schlieren type of chromitite from the Bakanov Kluch chromite deposit (sample PE1870) (Ion map).</p> Full article ">Figure 5
<p>Back-scattered electron images of polished sections from the Alapaevsk chromitites (light grey = chromite, dark grey = altered silicates). (<b>A</b>) Massive and partially brecciated chromite from Bol’shaya Kruglyshka; (<b>B</b>) massive chromite from Krest; (<b>C</b>) massive chromite from 3-d Podyony Rudnik showing ferrian chromite alteration (lighter gray) developed along cracks and fissures; (<b>D</b>) massive chromite with ferrian chromite alteration (lighter gray) from Bakanov Kluch; (<b>E</b>) massive chromite with about 40% of altered silicates from Kurmanovskoe; (<b>F</b>) massive chromite with about 40% of altered silicates showing pull-apart texture from Bakanov Kluch.</p> Full article ">Figure 6
<p>Composition of unaltered chromite from the Alapaevsk chromitite. (<b>A</b>) Variation of the chromium number, Cr# = Cr/(Cr + Al), and bivalent iron number, Fe<sup>2+</sup># = Fe<sup>2+</sup>/(Fe<sup>2+</sup> + Mg); (<b>B</b>) negative correlation of Al<sub>2</sub>O<sub>3</sub> versus Cr<sub>2</sub>O<sub>3</sub>; (<b>C</b>) variation of Cr<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub>. P = field of podiform chromitites; S = field of stratiform chromitites; UM = field of the Uralian chromitites hosted in the ophiolitic mantle; USM = field of the Uralian chromitites hosted in the supra-Moho cumulates [<a href="#B6-minerals-06-00108" class="html-bibr">6</a>,<a href="#B18-minerals-06-00108" class="html-bibr">18</a>,<a href="#B19-minerals-06-00108" class="html-bibr">19</a>,<a href="#B20-minerals-06-00108" class="html-bibr">20</a>]. Red square = literature data from [<a href="#B21-minerals-06-00108" class="html-bibr">21</a>].</p> Full article ">Figure 7
<p>Back-scattered electron (BSE) images of magmatic PGM associated with the chromitites of Kurmanovskoe, from Alapaevsk ophiolite. (<b>A,B</b>) Crystals composed of laurite and cuproiridsite included in fresh chromite; (<b>C</b>) laurite associated with a Cu-sulfide, included in fresh chromite; (<b>D</b>) single phase laurite in crack. Abbreviations: Chr = chromite; Lrt = laurite; Cpr = cuproiridsite, Sil = silicates; CuS = Cu-sulfide.</p> Full article ">Figure 8
<p>Back-scattered electron (BSE) images of secondary PGM associated with the chromitites from Alapaevsky. (<b>A</b>) Irregular alloy of Ir, Ru, Os, Ni-sulfide and Cu-sulfide in contact with ferrian chromite, from the chromitite of Kurmanovskoe; (<b>B</b>) complex grain composed pentlandite, awaruite, Fe-oxide or hydroxide in contact with ferrian-chromite and chlorite (Krest); (<b>C</b>) enlargement of (<b>B</b>) showing an alloy composed of Os and Ru. Abbreviations: Ir–Ru–Os = iridium alloy; Aw = awaruite; Pn = pentlandite; Fe–O = Fe-oxide or hydroxide; Chl = chlorite; Os–Ru = osmium alloy; other abbreviations = see <a href="#minerals-06-00108-f007" class="html-fig">Figure 7</a>.</p> Full article ">Figure 9
<p>Plots (at.%) of the compositions of laurite from chromitites of Alapaevsk (present study) compared with those analyzed in selected ophiolitic chromitites of the Urals (data from [<a href="#B9-minerals-06-00108" class="html-bibr">9</a>,<a href="#B20-minerals-06-00108" class="html-bibr">20</a>,<a href="#B21-minerals-06-00108" class="html-bibr">21</a>,<a href="#B22-minerals-06-00108" class="html-bibr">22</a>]).</p> Full article ">Figure 10
<p>Back-scattered electron (BSE) image of a Ni–Fe phosphide found in the interstitial serpentine of the Bakanov Kluch chromitite.</p> Full article ">Figure 11
<p>Binary diagram of P versus Ni + (Fe), apfu (atoms per formula unit), showing the composition of the Ni-phosphide found in the Bakanov Kluch chromitite (black square), compared with those of the minerals with Ni &gt; Fe described in the system Ni–Fe–P (open squares). Literature data from [<a href="#B25-minerals-06-00108" class="html-bibr">25</a>,<a href="#B26-minerals-06-00108" class="html-bibr">26</a>,<a href="#B27-minerals-06-00108" class="html-bibr">27</a>,<a href="#B28-minerals-06-00108" class="html-bibr">28</a>].</p> Full article ">Figure 12
<p>Back-scattered electron (BSE) images of silicates included in the Alapaevsk chromitites. Polygonal olivine in the chromitite from Kurmanovskoe (<b>A</b>,<b>B</b>); grains of clinopyroxene in the chromitite from Bakanov Kluch (<b>C</b>); inclusion composed of amphibole and chlorite found in the chromitite form 3-d Podyony Rudnik (<b>D</b>). Abbreviations: Ol = olivine; Cpx = clinopyroxene; Amph = amphibole; other abbreviations = see <a href="#minerals-06-00108-f007" class="html-fig">Figure 7</a> and <a href="#minerals-06-00108-f008" class="html-fig">Figure 8</a>.</p> Full article ">Figure 13
<p>Variation of NiO (<b>A</b>), MnO (<b>B</b>) and CaO (<b>C</b>) as a function of forsterite mol % in the olivine in the Cr-rich chromitites from Kurmanovskoe.</p> Full article ">Figure 14
<p>Compositional variations of silicates included in chromite from the Alapaevskychromitites. Binary diagram for the classification of the amphibole (<b>A</b>); ternary diagram for the classification of the pyroxenes (<b>B</b>). Simplified after [<a href="#B29-minerals-06-00108" class="html-bibr">29</a>].</p> Full article ">Figure 15
<p>TiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub> relationships in chromitites of Alapaevsk. (<b>A</b>) Composition of the chromitites, compared to the field of spinels from the supra-subduction zone (SSZ) and mid-ocean ridge (MOR) mantle peridotites (compositional fields from [<a href="#B34-minerals-06-00108" class="html-bibr">34</a>]); (<b>B</b>) the fields for IAB (island arc basalt), OIB (oceanic island basalt), MORB (mid-ocean ridge basalt), LIP (large igneous province) basalt, and supra-Moho (SUPRA-MOHO) chromitite from the Urals are from [<a href="#B6-minerals-06-00108" class="html-bibr">6</a>,<a href="#B36-minerals-06-00108" class="html-bibr">36</a>]. The horizontal dashed line at TiO<sub>2</sub> = 0.30 wt % separates the high-Ti IAB (high-K calc-alkaline suite) from the low-Ti IAB (boninitic, tholeiitic).</p> Full article ">Figure 16
<p>Metal-sulfide equilibrium curves for Ru, Os, Ir, and Ni as function of sulfur fugacity, expressed as log fS<sub>2</sub> and temperature. Yellow and blue fields show the conditions prevailing in mantle-hosted chromitites from ophiolites of the Urals. Yellow field = present work, blue field = [<a href="#B9-minerals-06-00108" class="html-bibr">9</a>,<a href="#B22-minerals-06-00108" class="html-bibr">22</a>,<a href="#B23-minerals-06-00108" class="html-bibr">23</a>,<a href="#B24-minerals-06-00108" class="html-bibr">24</a>].</p> Full article ">
1819 KiB  
Article
Tungsten Recovery from Spent SCR Catalyst Using Alkaline Leaching and Ion Exchange
by Wen-Cheng Wu, Tang-Yi Tsai and Yun-Hwei Shen
Minerals 2016, 6(4), 107; https://doi.org/10.3390/min6040107 - 17 Oct 2016
Cited by 47 | Viewed by 6944
Abstract
The recovery of tungsten (W) from a honeycomb-type spent selective catalytic reduction (SCR) catalyst using an alkaline leaching–ion exchange method was investigated. Spent SCR catalyst mainly consists of TiO2 and other oxides (6.37% W, 1.57% vanadium (V), and 2.81% silicon (Si), etc.). [...] Read more.
The recovery of tungsten (W) from a honeycomb-type spent selective catalytic reduction (SCR) catalyst using an alkaline leaching–ion exchange method was investigated. Spent SCR catalyst mainly consists of TiO2 and other oxides (6.37% W, 1.57% vanadium (V), and 2.81% silicon (Si), etc.). The ground catalyst was leached at the optimal conditions, as follows: NaOH concentration of 0.3 kg/kg of catalyst, pulp density of 3%, leaching temperature of 70 °C, particle size of −74 μm, and leaching time of 30 min. In this study, the leaching rate values of V and W under the above conditions were 87 wt %, and 91 wt %, respectively. The pregnant solution was then passed through a strong base anion exchange resin (Amberlite IRA900). At high pH conditions, the use of strong base anion exchange resin led to selective loading of divalent WO42− from the solution, because the fraction of two adjacent positively-charged sites on the IRA900 resin was higher and separate from the coexisting VO43−. The adsorbed W could then be eluted with 1 M NaCl + 0.5 M NaOH. The final concentrated W solution had 8.4 g/L of W with 98% purity. The application of this process in industry is expected to have an important impact on the recovery of W from secondary sources of these metals. Full article
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<p>Effects of NaOH addition on the extraction efficiencies of W and V.</p> Full article ">Figure 2
<p>Effects of pulp density on the extraction efficiencies of W and V.</p> Full article ">Figure 3
<p>Effect of leaching temperature on the extraction efficiencies of W and V.</p> Full article ">Figure 4
<p>Effect of particle size on the extraction efficiencies of W and V.</p> Full article ">Figure 5
<p>Effect of leaching time on the extraction efficiencies of W and V.</p> Full article ">Figure 6
<p>Normalized breakthrough curves (C/C<sub>0</sub> vs. BV) for V, W, and Si on IRA900 resin.</p> Full article ">Figure 7
<p>The elution curves for W elution from the loaded column.</p> Full article ">Figure 8
<p>Proposed flow chart for the recovery of W from spent selective catalytic reduction (SCR) catalyst.</p> Full article ">
5597 KiB  
Article
Study on Selective Removal of Impurity Iron from Leached Copper-Bearing Solution Using a Chelating Resin
by Yubiao Li, Xinyu Wang, Qing Xiao and Xu Zhang
Minerals 2016, 6(4), 106; https://doi.org/10.3390/min6040106 - 15 Oct 2016
Cited by 11 | Viewed by 4422
Abstract
In order to selectively remove iron from copper laden solution after leaching but prior to electrowinning, equilibrium, kinetic, and thermodynamic studies have been conducted on an a chelating resin of Rexp-501 at pH 1.0 and at various temperatures. Both Langmuir and Freundlich models [...] Read more.
In order to selectively remove iron from copper laden solution after leaching but prior to electrowinning, equilibrium, kinetic, and thermodynamic studies have been conducted on an a chelating resin of Rexp-501 at pH 1.0 and at various temperatures. Both Langmuir and Freundlich models were investigated, with the Langmuir model proving to be more suitable for fitting iron removal performance, with little influence from copper concentration. Compared with the pseudo first order kinetic model, the pseudo second order kinetic model fitted the dynamic adsorption process better, indicating a chemisorption mechanism. Fourier transform infrared spectroscopy (FT-IR) results indicated that C=O from carbonyl group played a key role in combining with iron and can be regenerated and reused. However, the C=O of the acylamino group combining with iron was not able to be released after oxalic acid was applied. Full article
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<p>Iron and copper adsorption by Rexp-501 at various concentrations, 298 K.</p> Full article ">Figure 2
<p>Separation efficiency (iron-to-copper ratio) by Rexp-501 at various concentrations, 298 K. Copper and iron in the same concentrations.</p> Full article ">Figure 3
<p>Iron adsorption by resin Rexp-501 at pH 1.0, 298 K and 150 rpm for 90 min.</p> Full article ">Figure 4
<p>Iron adsorption capacity of resin Rexp-501 at various iron concentrations, 298 K.</p> Full article ">Figure 5
<p>(<b>a</b>) Langmuir and (<b>b</b>) Freundlich isotherms of iron adsorption by Rexp-501 at 298 K.</p> Full article ">Figure 6
<p>Iron adsorption by resin Rexp-501 at iron concentrations of 5000 mg·L<sup>−1</sup>.</p> Full article ">Figure 7
<p>Fittings of iron adsorption by Rexp-501. (<b>a</b>) Lagergren pseudo first order model; (<b>b</b>) Lagergren pseudo second order model.</p> Full article ">Figure 8
<p>Arrhenius plot for iron adsorption by Rexp-501.</p> Full article ">Figure 9
<p>The effects of acid type on iron removal from saturated Rexp-501, 298 K.</p> Full article ">Figure 10
<p>Iron desorption kinetics by oxalic acid.</p> Full article ">Figure 11
<p>FT-IR spectra of fresh and adsorbed resins. (<b>a</b>) Fresh; (<b>b</b>) adsorbed at 298 K; (<b>c</b>) adsorbed at 328 K; (<b>d</b>) desorbed using oxalic acid at 298 K.</p> Full article ">
1294 KiB  
Article
Flotation of Chalcopyrite and Molybdenite in the Presence of Organics in Water
by Maria Sinche-Gonzalez, Daniel Fornasiero and Massimiliano Zanin
Minerals 2016, 6(4), 105; https://doi.org/10.3390/min6040105 - 14 Oct 2016
Cited by 18 | Viewed by 5863
Abstract
One of the water constituents that has not been investigated in great detail for potential detrimental effect on mineral flotation is organic matter. This study investigates the effect of natural organic materials contained in water, such as humic, fulvic and tannic acids, on [...] Read more.
One of the water constituents that has not been investigated in great detail for potential detrimental effect on mineral flotation is organic matter. This study investigates the effect of natural organic materials contained in water, such as humic, fulvic and tannic acids, on the flotation of copper and molybdenum sulphides in alkaline conditions and in concentrations similar to those found in natural waters. Results show that copper and molybdenum grades decreased with the addition of humic, tannic and fulvic acid in that order, with a larger depression of molybdenite grade and recovery. Adsorption studies using ultraviolet (UV)-visible spectroscopy and X-ray photoelectron spectrometer (XPS) surface analysis confirmed that these organic materials were adsorbed on the minerals surface. Complimentary analyses of froth characteristics, particle size distribution and fine particles entrainment were also conducted to explain the cause of the negative effect of these organic materials on flotation. The flotation results were explained in terms of the decrease in the hydrophobicity of the mineral surfaces due to the adsorption of hydrophilic groups in these organic materials which then prevent bubble-particle adhesion. The larger detrimental effect of humic acid is due to its higher adsorption on the minerals, high molecular weight and carbon content compared with the other organic acids used. Full article
(This article belongs to the Special Issue Flotation in Mineral Processing)
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<p>Absorbance versus concentration of humic acid (HA), tannic acid (TA) and fulvic acid (FA) (NaCl 10<sup>−2</sup> M; pH 9.3).</p> Full article ">Figure 2
<p>Cumulative recoveries as a function of flotation time and organic matter concentration (mg/L) for chalcopyrite with HA (<b>a</b>); TA (<b>c</b>); and FA (<b>e</b>) and for molybdenite with HA (<b>b</b>); TA (<b>d</b>) and FA (<b>f</b>) (pH = 9.3).</p> Full article ">Figure 3
<p>Grades versus recoveries of Cu (<b>a</b>); Mo (<b>b</b>); and Fe (<b>c</b>) in the bulk Cu–Mo flotation concentrate without (N/O) and with the addition of 20 mg/L of organic matter at pH 10.5.</p> Full article ">Figure 4
<p>XRD analysis of species present in the bulk Cu–Mo concentrates without (N/O) and with 20 mg/L of humic acid (HA) or fulvic acid (FA).</p> Full article ">Figure 5
<p>Concentration of OM adsorbed on (<b>top</b>) chalcopyrite; and (<b>bottom</b>) molybdenite (NaCl 10<sup>−2</sup> M, pH 9.3).</p> Full article ">
16650 KiB  
Article
Nano-Tomography of Porous Geological Materials Using Focused Ion Beam-Scanning Electron Microscopy
by Yang Liu, Helen E. King, Marijn A. Van Huis, Martyn R. Drury and Oliver Plümper
Minerals 2016, 6(4), 104; https://doi.org/10.3390/min6040104 - 10 Oct 2016
Cited by 36 | Viewed by 11606
Abstract
Tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM) provides three-dimensional information about solid materials with a resolution of a few nanometres and thus bridges the gap between X-ray and transmission electron microscopic tomography techniques. This contribution serves as an introduction and overview [...] Read more.
Tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM) provides three-dimensional information about solid materials with a resolution of a few nanometres and thus bridges the gap between X-ray and transmission electron microscopic tomography techniques. This contribution serves as an introduction and overview of FIB-SEM tomography applied to porous materials. Using two different porous Earth materials, a diatomite specimen, and an experimentally produced amorphous silica layer on olivine, we discuss the experimental setup of FIB-SEM tomography. We then focus on image processing procedures, including image alignment, correction, and segmentation to finally result in a three-dimensional, quantified pore network representation of the two example materials. To each image processing step we consider potential issues, such as imaging the back of pore walls, and the generation of image artefacts through the application of processing algorithms. We conclude that there is no single image processing recipe; processing steps need to be decided on a case-by-case study. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
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Figure 1
<p>(<b>a</b>) SEM image revealing the surface of the diatomite sample; (<b>b</b>) BSE (backscattered electrons) image of cross section from serial sectioning process, scale bar is 5 µm. The saturated contrast concerns the in situ Pt deposition in BSE imaging.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) reacted dunite (olivine-dominated rock) showing the produced amorphous (am) silica rim and (<b>b</b>) the interfacial region between olivine and amorphous silica.</p> Full article ">Figure 3
<p>(<b>a</b>) FIB-SEM of FEI Nova NanoLab 600 (FEI Company, Hillsboro, OR, USA) at Utrecht University; (<b>b</b>) its sample stage (marked by red rectangle) and (<b>c</b>) its inner chamber; (<b>d</b>) the FEI Helios NanoLab G3 UC (FEI Company) at Utrecht University.</p> Full article ">Figure 4
<p>(<b>a</b>) A flow chart showing the serial sectioning procedure of FIB nano-tomography; (<b>b</b>) a schematic indication of one prepared region of interest for tomography technique in a FIB-SEM.</p> Full article ">Figure 5
<p>(<b>a</b>) SE imaging and (<b>b</b>) BSE imaging at 2 kV of the same section in the reacted olivine sample. In the rectangle is a region with curtaining effects; arrows indicate charging effect.</p> Full article ">Figure 6
<p>Trajectories of electrons into a silica-based material, diatomite, simulated by the Monte Carlo method in the Casino software (<a href="http://www.gel.usherbrooke.ca/casino/index.html" target="_blank">http://www.gel.usherbrooke.ca/casino/index.html</a>) [<a href="#B66-minerals-06-00104" class="html-bibr">66</a>]. Acceleration voltage of the electron beam is 2 kV, incident angle is 38°, and dose is 10<sup>5</sup>. Blue tracks represent incident electrons, whereas red tracks represent backscattered electrons.</p> Full article ">Figure 7
<p>General steps of image processing on tomographic data from serial sectioning procedure.</p> Full article ">Figure 8
<p>(<b>a</b>) Single slice image extracted from the corrected stack generated from the olivine sample; (<b>b</b>) pores are delimited at red outline; (<b>c</b>) result from segmentation of the single slice. The surface area of this slice is about 437 µm<sup>2</sup>.</p> Full article ">Figure 9
<p>(<b>a</b>) A small region cropped from one slice image showing a big diatom with large pore space that extends in depth (along the <span class="html-italic">Z</span> direction); (<b>b</b>) the watershed segmentation result of this small slice image; (<b>c</b>) a thresholding plus manual correction result of the same region. Two different strategies for segmenting the pore space in the diatomite sample using Avizo: (<b>d</b>) watershed segmentation; (<b>e</b>) thresholding plus manual correction.</p> Full article ">Figure 9 Cont.
<p>(<b>a</b>) A small region cropped from one slice image showing a big diatom with large pore space that extends in depth (along the <span class="html-italic">Z</span> direction); (<b>b</b>) the watershed segmentation result of this small slice image; (<b>c</b>) a thresholding plus manual correction result of the same region. Two different strategies for segmenting the pore space in the diatomite sample using Avizo: (<b>d</b>) watershed segmentation; (<b>e</b>) thresholding plus manual correction.</p> Full article ">Figure 10
<p>3D rendering of the pores in the explored volume of 23 × 19 × 15 µm<sup>3</sup> from the reacted olivine sample, shown in four different orientations. The scale bar is 5 µm.</p> Full article ">Figure 11
<p>Pore size distribution in the obtained volume from the olivine sample. (<b>a</b>) Labelled pores painted in different colours; (<b>b</b>) probability density function of labelled pores size distribution.</p> Full article ">
1261 KiB  
Article
The Development of Fine Microgram Powder Electrode System and Its Application in the Analysis of Chalcopyrite Leaching Behavior
by Hajime Miki, Tsuyoshi Hirajima, Kazunori Oka and Keiko Sasaki
Minerals 2016, 6(4), 103; https://doi.org/10.3390/min6040103 - 9 Oct 2016
Cited by 3 | Viewed by 3882
Abstract
An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and [...] Read more.
An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and is sensitive compared with conventional electrode systems for various sulfide minerals such as pyrite, chalcopyrite, chalcocite, enargite, and tennantite. The leaching behavior of chalcopyrite was re-examined in a test of the application of this electrode system. Chalcopyrite dissolution is enhanced in specific potential regions because it is believed to be reduced to leachable chalcocite, but this result is inconclusive because it is difficult to detect the intermediate chalcocite. Powder chalcopyrite in the new powder electrode system was held at 0.45 V in the presence of copper ion and sulfuric acid media followed by an application of potential in the anodic direction. Besides the chalcopyrite oxidation peak, a small peak resulted at ∼0.55 V; this peak corresponds to reduced chalcocite, because it occurs at the same potential as the chalcocite oxidation peak. Full article
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<p>Potential polarization with 5 µg of pyrite that is attached to the platinum plate surface. Experiments were repeated (runs 1 and 2) to determine the reproducibility.</p> Full article ">Figure 2
<p>Effect of the attached amount of pyrite on the voltammogram. Potential polarization with 5–15 µg of pyrite that is attached to the platinum plate surface.</p> Full article ">Figure 3
<p>Pyrite voltammogram and the result of peak fitting with a Gaussian function. The pyrite voltammogram is the result of potential polarization with 5 µg of pyrite that is attached to the platinum plate surface.</p> Full article ">Figure 4
<p>Relationships between the attached amount of pyrite on the platinum plate surface and the calculated amount of pyrite from the peak area of Gaussian fitted peak with the voltammogram.</p> Full article ">Figure 5
<p>Comparison between voltammograms on various sulfide mineral: result of potential polarization with 10 µg of chalcopyrite (<b>A</b>) and chalcocite (<b>B</b>); result of potential polarization with 10 µg of enargite (<b>C</b>) and tennantite (<b>D</b>).</p> Full article ">Figure 6
<p>Voltammogram with or without 10 µg of chalcopyrite that is attached to the platinum plate surface and was held at 0.45 V for 300 s before the potential was polarized in the anodic direction at a 1 mV·s<sup>−1</sup> scan rate under ambient conditions. The electrolyte is 0.1-M H<sub>2</sub>SO<sub>4</sub> with or without 0.01-M Cu<sup>2+</sup>. The chalcocite potential polarization results that are shown in <a href="#minerals-06-00103-f005" class="html-fig">Figure 5</a>B are added to this graph for comparison.</p> Full article ">
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