Minerals

12 pages, 5960 KiB

Open AccessFeature PaperArticle

Experimental Determination of the Effect of CaO and Al₂O₃ in Slag Systems Related to the Conversion Process of High Copper Matte Grade

by Héctor Henao, Erik Kohnenkamp, Lisa Rojas and Alex Moyano

Minerals 2019, 9(11), 716; https://doi.org/10.3390/min9110716 - 19 Nov 2019

Cited by 2 | Viewed by 2667

Abstract

The slags generated in the conventional copper conversion process are mainly composed of Cu₂O–Fe₂O₃–SiO₂ with CaO, Al₂O₃, and MgO compounds—in concentrations up to 10 wt %. The present work contributes to the [...] Read more.

The slags generated in the conventional copper conversion process are mainly composed of Cu₂O–Fe₂O₃–SiO₂ with CaO, Al₂O₃, and MgO compounds—in concentrations up to 10 wt %. The present work contributes to the knowledge of the conversion process, generating experimental data for the phase diagrams of the Cu₂O–Fe₂O₃–SiO₂–Al₂O₃ and Cu₂O–Fe₂O₃–SiO₂–CaO systems. The experiments were carried out in a tubular furnace at temperatures of 1150 °C and 1200 °C, under a condition of saturation with tridymite and spinel. Once the equilibrium was reached, the samples were immediately quenched in water. The phases in the samples were observed through a scanning electron microscope (SEM) and the elemental composition of the phases were analyzed by means of energy-dispersive X-ray spectroscopy (EDS) detectors. The addition of Al₂O₃ and CaO into the Cu₂O–Fe₂O₃–SiO₂ system resulted in an appreciable displacement of the liquidus lines, corresponding to an expansion of the liquid in the tridymite primary phase field. The addition of CaO and Al₂O₃ combined was evaluated on industrial slags and from samples obtained in a Peirce–Smith furnace, with increasing amounts of CaO in the flux. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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14 pages, 3788 KiB

Open AccessArticle

A Paris-Edinburgh Cell for High-Pressure and High-Temperature Structure Studies on Silicate Liquids Using Monochromatic Synchrotron Radiation

by Tony Yu, Clemens Prescher, Young Jay Ryu, Feng Shi, Eran Greenberg, Vitali Prakapenka, Peter Eng, Joanne Stubbs, Yoshio Kono, Guoyin Shen, Heather Watson, Mark L. Rivers, Stephen R. Sutton and Yanbin Wang

Minerals 2019, 9(11), 715; https://doi.org/10.3390/min9110715 - 19 Nov 2019

Cited by 8 | Viewed by 5942

Abstract

A Paris-Edinburgh press combined with a multi-channel collimator assembly has been commissioned at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS) beamline for monochromatic X-ray scattering, with an emphasis on studying low-Z liquids, especially silicate liquids at high pressure. The Paris-Edinburgh press is [...] Read more.

A Paris-Edinburgh press combined with a multi-channel collimator assembly has been commissioned at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS) beamline for monochromatic X-ray scattering, with an emphasis on studying low-Z liquids, especially silicate liquids at high pressure. The Paris-Edinburgh press is mounted on a general-purpose diffractometer, with a pixel array detector mounted on the detector arm. The incident monochromatic undulator beam with energies up to 60 keV is focused both horizontally and vertically to a beam size about 30 × 30 µm. With this setup, background scattering from the surrounding pressure media is completely removed at 2θ angles above 10° for samples larger than 1.05 mm in diameter. Thirty minutes is typically sufficient to collect robust X-ray scattering signals from a 1.6 mm diameter amorphous silicate sample. Cell assemblies for the standard Paris-Edinburgh anvils have been developed and pressures and temperatures up to 7 GPa and 2300 K, respectively, have been maintained steadily over hours. We have also developed a cupped-toroidal Drickamer anvil to further increase pressure and temperature capabilities. The cupped-toroidal Drickamer anvil combines features of a modified Drickamer anvil and the traditional Paris-Edinburgh anvil. Pressures up to 12 GPa have been generated at temperatures up to 2100 K. Full article

(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)

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21 pages, 4918 KiB

Open AccessEditor’s ChoiceArticle

Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials

by Evangelos Petrakis, Vasiliki Karmali, Georgios Bartzas and Konstantinos Komnitsas

Minerals 2019, 9(11), 714; https://doi.org/10.3390/min9110714 - 19 Nov 2019

Cited by 35 | Viewed by 4791

Abstract

This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the [...] Read more.

This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the compressive strength of the produced alkali activated materials (AAMs). Other parameters affecting alkali activation, i.e., temperature, curing, and ageing time were also examined. Among the different mathematical models used to simulate the particle size distribution, Rosin–Rammler (RR) was found to be the most suitable. When piecewise regression analysis was applied to experimental data it was found that the particle size distribution of the slag products exhibits multifractal character. In addition, grinding of slag exhibits non-first-order behavior and the reduction rate of each size is time dependent. The grinding rate and consequently the grinding efficiency increases when the particle size increases, but drops sharply near zero after prolonged grinding periods. Regarding alkali activation, it is deduced that among the parameters studied, particle size (and the respective specific surface area) of the raw slag product and curing temperature have the most noticeable impact on the compressive strength of the produced AAMs. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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19 pages, 9145 KiB

Open AccessArticle

Origin of the Shangfang Tungsten Deposit in the Fujian Province of Southeast China: Evidence from Scheelite Sm–Nd Geochronology, H–O Isotopes and Fluid Inclusions Studies

by Lü-Yun Zhu, Shao-Yong Jiang, Run-Sheng Chen and Ying Ma

Minerals 2019, 9(11), 713; https://doi.org/10.3390/min9110713 - 19 Nov 2019

Cited by 10 | Viewed by 3738

Abstract

The Shangfang deposit is a recently discovered large-scale tungsten deposit (66,500 t at 0.23% WO₃), which is located near the western boundary of the Southeastern Coastal Metallogenic Belt (i.e., Zhenghe–Dafu fault), and adjacent to the northeast of the Nanling Range Metallogenic [...] Read more.

The Shangfang deposit is a recently discovered large-scale tungsten deposit (66,500 t at 0.23% WO₃), which is located near the western boundary of the Southeastern Coastal Metallogenic Belt (i.e., Zhenghe–Dafu fault), and adjacent to the northeast of the Nanling Range Metallogenic Belt. Unlike many other W–Sn deposits in this region that occur within or near the granites, the orebodies in the Sangfang deposit all occur within the amphibolite of Palaeoproterozoic Dajinshan Formation and have no direct contact to the granite. In this study, we carry out a thermal ionization mass spectrometer (TIMS) Sm-Nd isotope analysis for the scheelites from the orebody, which yields a Sm–Nd isochron age of 157.9 ± 6.7 Ma (MSWD = 0.96). This age is in good agreement with the previously published zircon U–Pb age (158.8 ± 1.6 Ma) for the granite and the molybdenite Re–Os age (158.1 ± 5.4 Ma) in the deposit. Previous studies demonstrated that the W–Sn deposits occurring between Southeastern Nanling Range and Coastal Metallogenic Belt mainly formed in the two periods of 160–150 Ma and 140–135 Ma, respectively. The microthermometry results of fluid inclusions in scheelite and quartz are suggestive of a near-isothermal (possibly poly-baric) mixing between two fluids of differing salinities. The H–O isotope results illustrate that the ore-forming fluids are derived from magma and might be equilibrated with metamorphic rocks at high temperature. The Jurassic granite pluton should play a critical role for the large hydrothermal system producing the Shangfang W deposit. Furthermore, the negative ε_Nd(t) of −14.6 obtained in the Shanfang scheelite suggests for the involvement of the deep crustal materials. In general, subduction of the paleo-Pacific plate caused an extensional tectonic setting with formation of the Shangfang granites and related W mineralization, the geological background of which is similar to other W deposits in the Nanling Range Metallogenic Belt. Full article

(This article belongs to the Special Issue Development of W-Sn and Rare-Metal Metallogenic Systems in an Orogenic Belt)

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17 pages, 2110 KiB

Open AccessArticle

C- and N-Bearing Species in Reduced Fluids in the Simplified C–O–H–N System and in Natural Pelite at Upper Mantle P–T Conditions

by Ivan Sokol, Alexander Sokol, Taras Bul’bak, Andrey Nefyodov, Pavel Zaikin and Anatoly Tomilenko

Minerals 2019, 9(11), 712; https://doi.org/10.3390/min9110712 - 18 Nov 2019

Cited by 1 | Viewed by 2944

Abstract

C- and N-bearing species in reduced fluids weree studied experimentally in C–O–H–N and muscovite–C–O–H–N systems and in natural carbonate-bearing samples at mantle P–T parameters. The experiments reproduced three types of reactions leading to formation of hydrocarbons (HCs) at 3.8–7.8 GPa and 800–1400 °C [...] Read more.

C- and N-bearing species in reduced fluids weree studied experimentally in C–O–H–N and muscovite–C–O–H–N systems and in natural carbonate-bearing samples at mantle P–T parameters. The experiments reproduced three types of reactions leading to formation of hydrocarbons (HCs) at 3.8–7.8 GPa and 800–1400 °C and at hydrogen fugacity (fH₂) buffered by the Fe–FeO (IW) + H₂O or Mo–MoO₂ (MMO) + H₂O equilibria: (i) Thermal destruction of organic matter during its subduction into the mantle (with an example of docosane), (ii) hydrogenation of graphite upon interaction with H₂-enriched fluids, and (iii) hydrogenation of carbonates and products of their reduction in metamorphic clayey rocks. The obtained quenched fluids analyzed after the runs by gas chromatography-mass spectrometry (GC–MS) and electronic ionization mass-spectrometry (HR–MS) contain CH₄ and C₂H₆ as main carbon species. The concentrations of C₂-C₄ alkanes in the fluids increase as the pressure and temperature increase from 3.8 to 7.8 GPa and from 800 to 1400 °C, respectively. The fluid equilibrated with the muscovite–garnet–omphacite–kyanite–rutile ± coesite assemblage consists of 50–80 rel.% H₂O and 15–40 rel.% alkanes (C₁ > C₂ > C₃ > C₄). Main N-bearing species are ammonia (NH₃) in the C–O–H–N and muscovite–C–O–H–N systems or methanimine (CH₃N) in the fluid derived from the samples of natural pelitic rocks. Nitrogen comes either from air or melamine (C₃H₆N₆) in model systems or from NH₄⁺ in the runs with natural samples. The formula CH₃N in the quenched fluid of the C–O–H–N system is confirmed by HR–MS. The impossibility of CH₃N incorporation into K-bearing silicates because of a big CH₃NH⁺ cation may limit the solubility of N in silicates at low fO₂ and hence may substantially influence the mantle cycle of nitrogen. Thus, subduction of slabs containing carbonates, organic matter, and N-bearing minerals into strongly reduced mantle may induce the formation of fluids enriched in H₂O, light alkanes, NH₃, and CH₃N. The presence of these species must be critical for the deep cycles of carbon, nitrogen, and hydrogen. Full article

(This article belongs to the Special Issue Genesis of Hydrocarbons in the Upper Mantle)

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31 pages, 12064 KiB

Open AccessArticle

The Environmental Significance of Sediment Surface Area as a Controlling Factor in the Preservation of Polychlorinated Dibenzo-P-Dioxins and Dibenzofurans (PCDD/PCDF) in Sediments Adjacent to Woodfibre Pulp Mill, Howe Sound, British Columbia

by Gareth Chalmers, Rupert Adams, Amanda Bustin and Marc Bustin

Minerals 2019, 9(11), 711; https://doi.org/10.3390/min9110711 - 18 Nov 2019

Cited by 1 | Viewed by 2681

Abstract

A sediment core was retrieved from an area adjacent to a Pulp and Paper Mill in Howe Sound, British Columbia, in order to examine the accumulation dioxins (PCDDs) and furans (PCDFs). Downcore distribution of TOC in the bulk samples is relatively uniform (0.5–1.7 [...] Read more.

A sediment core was retrieved from an area adjacent to a Pulp and Paper Mill in Howe Sound, British Columbia, in order to examine the accumulation dioxins (PCDDs) and furans (PCDFs). Downcore distribution of TOC in the bulk samples is relatively uniform (0.5–1.7 wt. %). Bulk PCDD/F concentration shows selective enrichment and depletion at specific sediment horizons, and a low to moderate correlation with surface area (r² = 0.23–0.54). TOC in size fractionated sediments ranges from 0.3–11 wt. % and shows a moderate correlation with surface area (r² = 0.51). The relationship between PCDD/Fs and surface area is congener specific, ranging from no significant correlation (TCDD; r² = 0.05), to a good correlation (i.e., OCDF; r² = 0.74). Results indicate that both dioxin and furan concentrations are related to organic matter concentration, molecular chlorination and sediment surface area. Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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15 pages, 3442 KiB

Open AccessFeature PaperArticle

Recycling Lead–Zinc Tailings for Cemented Paste Backfill and Stabilisation of Excessive Metal

by Zhu Su, Qiusong Chen, Qinli Zhang and Deming Zhang

Minerals 2019, 9(11), 710; https://doi.org/10.3390/min9110710 - 17 Nov 2019

Cited by 27 | Viewed by 4749

Abstract

This study demonstrates the feasibility of recycling lead–zinc tailing (LZT) as a cemented paste backfill (CPB) by considering the mechanical properties and environmental effects, thus providing an approach for safe and environmentally friendly treatment of LZT. First, the mechanical properties of CPB samples [...] Read more.

This study demonstrates the feasibility of recycling lead–zinc tailing (LZT) as a cemented paste backfill (CPB) by considering the mechanical properties and environmental effects, thus providing an approach for safe and environmentally friendly treatment of LZT. First, the mechanical properties of CPB samples were tested. When the cement/tailing ratio was 1:6 and the slurry concentration was 70%, the maximum unconfined compressive strength (UCS) of the CPB cured for 28 days reaching 2.05 MPa, which could ensure safe mining. Then, the metals with pollution potential in the backfill slurry were investigated through static leaching. Finally, after adding immobilisation materials to stabilise excessive metals, the environmental stability of the CPB was demonstrated through dynamic leaching and a toxicity characteristic leaching procedure. The results show that the lead leached from the backfill slurry still exceeds the Chinese standard for groundwater quality (GB/T14848-2017 Class III). The addition of 2 mg/L polyaluminium sulfate (PAS) can further improve the strength of the CPB and maintain the environmental friendliness of the CPB. Therefore, the technology of recovering LZT as a CPB proposed in this study is an effective alternative to deal with LZT, which can help lead–zinc mines meet the requirements of cleaner production. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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22 pages, 10979 KiB

Open AccessArticle

Compositional Variations and Genesis of Sandy-Gravel Ferromanganese Deposits from the Yōmei Guyot (Holes 431, 431A DSDP), Emperor Ridge

by Pavel Mikhailik, Alexander Khanchuk, Evgenii Mikhailik, Nataly Zarubina and Maksim Blokhin

Minerals 2019, 9(11), 709; https://doi.org/10.3390/min9110709 - 17 Nov 2019

Cited by 5 | Viewed by 2973

Abstract

This research presents results characterizing the mineral and chemical composition of ferromanganese (Fe-Mn) deposits from Yōmei Guyot (Holes 431 and 431A), recovered during the Deep-Sea Drilling Project (DSDP) Leg 55 R/V “Glomar Challenger”. The Fe-Mn deposits are represented by sandy-gravel clasts. The mineral [...] Read more.

This research presents results characterizing the mineral and chemical composition of ferromanganese (Fe-Mn) deposits from Yōmei Guyot (Holes 431 and 431A), recovered during the Deep-Sea Drilling Project (DSDP) Leg 55 R/V “Glomar Challenger”. The Fe-Mn deposits are represented by sandy-gravel clasts. The mineral composition and bulk concentration of major and minor elements, as well as the distribution of rare earth elements and yttrium patterns in mineral fractions of Fe-Mn samples, showed that the deposits are composed of fragments of Fe-Mn hydrogenetic crusts and diagenetic nodules. The morphology of Fe-Mn clasts from Holes 431 and 431A DSDP, as well as a comparison with growth conditions of Fe-Mn deposits from N-W Pacific Guyots, allowed us to establish a Late Pliocene age for the formation of this Fe-Mn placer from Yōmei Guyot. Accumulations of ferromanganese clasts in a sedimentary unit led us to classify this geological body as a new mineral resource of the World Ocean. Full article

(This article belongs to the Special Issue Marine Geology and Minerals)

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19 pages, 3759 KiB

Open AccessArticle

Calcium-Bearing Minerals Transformation during Underground Coal Gasification

by Shuqin Liu and Weiping Ma

Minerals 2019, 9(11), 708; https://doi.org/10.3390/min9110708 - 15 Nov 2019

Cited by 10 | Viewed by 5201

Abstract

Calcium-bearing minerals are one of the main typical minerals in coal and coal ash. In the process of coal thermal conversion, calcium-bearing minerals undergo different morphological transformation in which the reaction temperature, pressure, and atmosphere are important factors affecting their transformation. The reaction [...] Read more.

Calcium-bearing minerals are one of the main typical minerals in coal and coal ash. In the process of coal thermal conversion, calcium-bearing minerals undergo different morphological transformation in which the reaction temperature, pressure, and atmosphere are important factors affecting their transformation. The reaction process of underground coal gasification (UCG) could be clearly divided into pyrolysis, reduction, and oxidation and the typical calcium-bearing minerals are expected to indicate the actual reaction conditions of UCG. A high-calcium coal, Zhundong coal, was used in this research. The products of UCG were prepared and the minerals were identified by X-ray diffraction (XRD) and a scanning electron microscope coupled with an energy-dispersive spectrometer (SEM-EDS). The thermodynamic calculation was used to assist in understanding the transformation behaviors of calcium-bearing minerals. The experimental results show that the calcium-bearing mineral is gradually converted from gypsum (CaSO₄·2H₂O) in the raw coal into anhydrite (CaSO₄) during the pyrolysis process. In the reduction stage, anhydrite reacts with the reducing gas (CO) to produce oldhamite (CaS), and the oldhamite is stably present in the reduction ash. During the oxidation process, oldhamite is first transformed into CaSO₄, and then CaSO₄ is converted into CaO. Finally, CaO reacts with Al₂O₃ and SiO₂ to produce gehlenite (Ca₂Al₂SiO₇) at 1100 °C. As the oxidation temperature rises to 1400 °C, gehlenite is transformed into the thermodynamically stable anorthite (CaAl₂Si₂O₈). With the further progress of the reaction, anorthite will co-melt with iron-bearing minerals above 1500 °C. The ternary phase diagram of SiO₂–Al₂O₃–CaO system proves that anorthite and gehlenite are the typical high-temperature calcium-bearing minerals when the mole fraction of SiO₂ is higher than 0.6. Moreover, the gehlenite is converted to anorthite with the temperature rise, which is consistent with experimental results. This study provides a scientific basis for understanding the UCG reaction conditions. Full article

(This article belongs to the Collection Critical Metals and Minerals in Coal and Coal Combustion Products)

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15 pages, 829 KiB

Open AccessArticle

Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics

by Jingping Qiu, Yingliang Zhao, Hui Long, Zhenbang Guo, Jun Xing and Xiaogang Sun

Minerals 2019, 9(11), 707; https://doi.org/10.3390/min9110707 - 15 Nov 2019

Cited by 23 | Viewed by 3422

Abstract

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions [...] Read more.

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R² values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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15 pages, 5172 KiB

Open AccessArticle

The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C)

by Davide Mombelli, Andrea Gruttadauria, Silvia Barella and Carlo Mapelli

Minerals 2019, 9(11), 706; https://doi.org/10.3390/min9110706 - 14 Nov 2019

Cited by 11 | Viewed by 4782

Abstract

Studies conducted over the past 10 years have demonstrated the technical suitability of the electric arc furnace slag as an alternative to natural stone in several applications. Steel slag can be profitably used as a road surface layer, for foundations and embankments, or [...] Read more.

Studies conducted over the past 10 years have demonstrated the technical suitability of the electric arc furnace slag as an alternative to natural stone in several applications. Steel slag can be profitably used as a road surface layer, for foundations and embankments, or for concrete aggregates. However, a strong limitation to their use is due to the presence of toxic metals (Ba, Cr, V, Mo, etc.) that can be released into the environment in particular conditions, especially for unbound products in which the slag can come into contact with water. Recent studies have investigated the role of chemical composition and microstructure of slag on toxic metal leaching, allowing for the design of suitable stabilization treatments for hindering such leaching. In this work, four batches of electric arc furnace carbon steel slag underwent a stabilization treatment and the obtained results were compared. In two batches, the stabilizer was added directly in the slag pot and the slag was cooled down in the same pot. The other two batches were stabilized during the downfall from slag door to slag pit. Several slag samples were collected before and after the stabilization treatment and were characterized by means of ED-XRF, XRD, and SEM analysis. Leaching tests were carried out in agreement with EN 12457-2 standard on 4 mm granulated slag, and the leachate concentration was compared with the current Italian limits listed in D.M. 3 August 2005 N. 201 and D.M. 5 April 2006 N. 186. The results clearly indicated that the cooling in the slag pot improved the efficiency of the stabilization treatment, leading to a complete transformation of the microstructure by a full development of homogeneous gehlenite matrix and a coarsening of Cr-spinels, assuring better toxic metal retention behavior. On the contrary, stabilization in the slag-pit was rapid and reduced the interaction between slag and stabilizer, leading only to partial transformation of larnite into gehlenite, and also reducing the coarsening of Cr-spinel. In addition, a layering effect was observed, resulting in an inhomogeneous product from top to bottom in terms of chemical composition, microstructure, and leaching behavior. Full article

(This article belongs to the Special Issue Metallurgical Slags)

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16 pages, 3767 KiB

Open AccessArticle

Utilization of Sodium Hexametaphosphate for Separating Scheelite from Calcite and Fluorite Using an Anionic–Nonionic Collector

by Jianhua Kang, Yuehua Hu, Wei Sun, Zhiyong Gao and Runqing Liu

Minerals 2019, 9(11), 705; https://doi.org/10.3390/min9110705 - 14 Nov 2019

Cited by 22 | Viewed by 4625

Abstract

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × [...] Read more.

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10⁻⁶ mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP. Full article

(This article belongs to the Special Issue Surface Chemistry in Mineral Processing and Extractive Metallurgy)

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20 pages, 4107 KiB

Open AccessArticle

Natural and Chemically Modified Post-Mining Clays—Structural and Surface Properties and Preliminary Tests on Copper Sorption

by Beata Jabłońska, Mark Busch, Andriy V. Kityk and Patrick Huber

Minerals 2019, 9(11), 704; https://doi.org/10.3390/min9110704 - 14 Nov 2019

Cited by 11 | Viewed by 3345

Abstract

The structural and surface properties of natural and modified Pliocene clays from lignite mining are investigated in the paper. Chemical modifications are made using hydrofluoric acid (HF), sulfuric acid (H₂SO₄), hydrochloric acid (HCl), nitric acid (HNO₃), sodium [...] Read more.

The structural and surface properties of natural and modified Pliocene clays from lignite mining are investigated in the paper. Chemical modifications are made using hydrofluoric acid (HF), sulfuric acid (H₂SO₄), hydrochloric acid (HCl), nitric acid (HNO₃), sodium hydroxide (NaOH), and hydrogen peroxide (H₂O₂), at a concentration of 1 mol/dm³. Scanning electron microscopy is used to detect the morphology of the samples. Nitrogen adsorption isotherms were recorded to determine the specific surface area (SSA), mesoporosity, microporosity, and fractal dimensions. The raw clay has an SSA of 66 m²/g. The most promising changes in the structural properties are caused by modifications with HF or H₂SO₄ (e.g., the SSA increased by about 60%). In addition, the raw and modified clays are used in preliminary tests with Cu(II) sorption, which were performed in batch static method at initial Cu(II) concentrations of 25, 50, 80, 100, 200, 300, and 500 mg/dm³ in 1% aqueous suspensions of the clayey material. The maximum sorption of Cu(II) on the raw material was 15 mg/g. The structural changes after the modifications roughly reflect the capabilities of the adsorbents for Cu(II) adsorption. The modifications with HF and H₂SO₄ bring a similar improvement in Cu(II) adsorption, which is around 20–25% greater than for the raw material. The structural properties of investigated clays and their adsorptive capabilities indicate they could be used as low-cost adsorbents (e.g., for industrial water pretreatment). Full article

(This article belongs to the Special Issue Mineral Sorbents)

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13 pages, 4435 KiB

Open AccessArticle

Novel Selective Depressant of Titanaugite and Implication for Ilmenite Flotation

by Nengyun Liu, Zhen Wang, Junhui Xiao, Hongbin Wang, Bing Deng, Yushu Zhang and Chao Chen

Minerals 2019, 9(11), 703; https://doi.org/10.3390/min9110703 - 13 Nov 2019

Cited by 12 | Viewed by 3110

Abstract

This paper studies the effects of sodium polystyrene sulfonate (PSSNa) used as a depressant upon the separation of ilmenite from titanaugite through flotation when sodium oleate (NaOl) is used as a collector by performing single mineral flotation experiments. The depression mechanism of PSSNa [...] Read more.

This paper studies the effects of sodium polystyrene sulfonate (PSSNa) used as a depressant upon the separation of ilmenite from titanaugite through flotation when sodium oleate (NaOl) is used as a collector by performing single mineral flotation experiments. The depression mechanism of PSSNa on titanaugite flotation was studied by electrokinetic potential and adsorbed amount measurements together with FTIR and XPS detection. Single mineral flotation experiments show that PSSNa is a selective depressant for the separation of ilmenite and titanaugite via flotation with NaOl as the collector. The results of the adsorbed amount tests show that the biggest distinction is in terms of the amount of NaOl adsorbed on the surfaces of ilmenite and titanaugite; the amount is expanded from 2.28 × 10⁻⁷ to 9.34 × 10⁻⁷ mol/m² when the dosage of PSSNa is 1 mg/L, as compared with no PSSNa, suggesting that PSSNa is a selective depressant when separating ilmenite and titanaugite through flotation. FTIR testing shows that chemisorption has occurred between the –SO₃⁻ groups of the molecular PSSNa and titanaugite surfaces. The results of further XPS testing reveal that PSSNa chemically interacts with Ca/Mg/Al/Fe on the titanaugite surface. The test results of FTIR in combination with XPS confirm that PSSNa stops NaOl from interacting with Mg, Fe, Al, and Ca on the titanaugite surface, and this outcome is the main reason for the widening of the adsorption quantity gap of NaOl on titanaugite and ilmenite surfaces, and titanaugite flotation is suppressed. The results of the comparison flotation testing on actual Panzhihua titanic iron ore (TiO₂ grade: 15.63%) with titanaugite as the main gangue show that a better effect is obtained by replacing sodium silicate (SS) with PSSNa, and the recovery of TiO₂ using PSSNa is higher than that when using sodium silicate. In a closed circuit flotation test, ilmenite concentrate is obtained with a TiO₂ grade of 45.97% and a recovery of 76.32% by using PSSNa as a titanaugite depressant. Full article

(This article belongs to the Special Issue Interface Science in Mineral (Bio)Processing)

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13 pages, 2383 KiB

Open AccessArticle

Crystal Chemistry of Sulfates from the Apuan Alps (Tuscany, Italy). V. Scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁: A New Metavoltine-Related Mineral

by Cristian Biagioni, Luca Bindi, Daniela Mauro and Ulf Hålenius

Minerals 2019, 9(11), 702; https://doi.org/10.3390/min9110702 - 13 Nov 2019

Cited by 10 | Viewed by 4932

Abstract

The new mineral species scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs [...] Read more.

The new mineral species scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as pseudo-hexagonal tabular crystals, yellowish to brownish in color, up to 0.5 mm in size. Cleavage is perfect on {0001}. It is associated with giacovazzoite, krausite, gypsum, jarosite, alum-(K), and magnanelliite. Electron microprobe analyses give (wt %): SO₃ 47.31, Al₂O₃ 0.66, Fe₂O₃ 24.68, FeO 0.69, Na₂O 0.52, K₂O 17.36, H₂O_calc 15.06, total 106.28. The partitioning of Fe between Fe²⁺ and Fe³⁺ was based on Mössbauer spectroscopy. On the basis of 67 O atoms per formula unit, the empirical chemical formula is (K_7.50Na_0.34)_Σ7.84(Fe³⁺_6.29Al_0.26Fe²⁺_0.20)_Σ6.75S_12.02O₅₀·17H₂O. The ideal end-member formula can be written as K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁. Scordariite is trigonal, space group R-3, with (hexagonal setting) a = 9.7583(12), c = 53.687(7) Å, V = 4427.4(12) Å³, Z = 3. The main diffraction lines of the observed X-ray powder pattern are [d(in Å), estimated visual intensity]: 8.3, strong; 6.6, medium; 3.777, medium; 3.299, medium; 3.189, medium; 2.884, strong. The crystal structure of scordariite has been refined using X-ray single-crystal data to a final R₁ = 0.057 on the basis of 1980 reflections with F_o > 4σ(F_o) and 165 refined parameters. It can be described as a layered structure formed by three kinds of layers. As with other metavoltine-related minerals, scordariite is characterized by the occurrence of the [Fe³⁺₃O(SO₄)₆(H₂O)₃]⁵⁻ heteropolyhedral cluster. Full article

(This article belongs to the Collection New Minerals)

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16 pages, 9653 KiB

Open AccessArticle

Sulfides in Metamorphic Rocks of the Fore Range Zone (Greater Caucasus). A New Type of Mineral Container for Peak Metamorphism Mineral Assemblages

by Vladimir A. Kamzolkin, Aleksandr N. Konilov, Ekaterina P. Kulakova, Anton V. Latyshev, Anna I. Smulskaya and Stanislav D. Ivanov

Minerals 2019, 9(11), 701; https://doi.org/10.3390/min9110701 - 13 Nov 2019

Cited by 2 | Viewed by 3783

Abstract

The rocks of the Armovka Formation (the Fore Range zone, Greater Caucasus) have undergone low-grade metamorphism that partially erased information about initial rock formation conditions. We discovered high-pressure mineral inclusions such as omphacite, phengite, garnet, and paragonite enclosed by pyrite and chalcopyrite. Mineral [...] Read more.

The rocks of the Armovka Formation (the Fore Range zone, Greater Caucasus) have undergone low-grade metamorphism that partially erased information about initial rock formation conditions. We discovered high-pressure mineral inclusions such as omphacite, phengite, garnet, and paragonite enclosed by pyrite and chalcopyrite. Mineral inclusions in sulfides may provide important information about metamorphic pressure−temperature conditions because they are shielded by the host minerals and isolated from significant low-grade overprinting. Calculations performed on phengite inclusions using the phengite Si-content barometry indicate a pressure ranging from 1.7 ± 0.2 to 1.9 ± 0.2 GPa for temperature of 600 ± 40 °C. These data are consistent with estimations obtained for eclogite bodies embedded in rocks of the Armovka Formation. Geothermobarometry of the latest yielded conditions of 680 ± 40 °C and a minimum pressure of 1.6 ± 0.2 GPa to upper pressure boundary at 2.1 GPa. This fact allows us to assume that the metamorphic rocks of the Armovka Formation were immersed in the subduction zone to the conditions of the eclogite facies of metamorphism, forming a coherent subduction complex together with eclogites. Full article

(This article belongs to the Special Issue From Diagenesis to Low-Grade Metamorphism)

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26 pages, 6680 KiB

Open AccessArticle

Nataliakulikite, Ca₄Ti₂(Fe³⁺,Fe²⁺)(Si,Fe³⁺,Al)O₁₁, a New Perovskite-Supergroup Mineral from Hatrurim Basin, Negev Desert, Israel

by Victor V. Sharygin, Grigory A. Yakovlev, Richard Wirth, Yurii V. Seryotkin, Ellina V. Sokol, Elena N. Nigmatulina, Nikolai S. Karmanov and Leonid A. Pautov

Minerals 2019, 9(11), 700; https://doi.org/10.3390/min9110700 - 13 Nov 2019

Cited by 6 | Viewed by 4075

Abstract

Nataliakulikite, Ca₄Ti₂(Fe³⁺,Fe²⁺)(Si,Fe³⁺,Al)O₁₁, is a mineral intermediate between perovskite CaTiO₃ and brownmillerite Ca₂(Fe,Al)₂O₅. It was discovered as a minor mineral in a high-temperature pyrometamorphic larnite-gehlenite [...] Read more.

Nataliakulikite, Ca₄Ti₂(Fe³⁺,Fe²⁺)(Si,Fe³⁺,Al)O₁₁, is a mineral intermediate between perovskite CaTiO₃ and brownmillerite Ca₂(Fe,Al)₂O₅. It was discovered as a minor mineral in a high-temperature pyrometamorphic larnite-gehlenite rock at the Nahal Morag Canyon of the Hatrurim Basin, Israel. Nataliakulikite is associated with larnite, flamite, gehlenite, magnesioferrite, Fe³⁺-rich perovskite, fluorapatite, barite, Hashemite, and retrograde phases (afwillite, hillebrandite, portlandite, calcite, ettringite, hydrogarnet, and other hydrated Ca-silicates). The mineral forms brown subhedral or prismatic grains (up to 20 µm) and their intergrowths (up to 50 μm). Its empirical formula (n = 47) is (Ca_3.992Sr_0.014U_0.004)(Ti_1.933Zr_0.030Nb_0.002) (Fe³⁺_0.610Fe²⁺_0.405Cr_0.005Mn_0.005)(Si_0.447Fe³⁺_0.337Al_0.216)O₁₁ and shows Si predominance in tetrahedral site. The unit-cell parameters (HRTEM data) and space group are: a = 5.254, b = 30.302, c = 5.488 Å, V = 873.7 Å³, Pnma, Z = 4. These dimensions and Electron backscatter diffraction (EBSD) data strongly support the structural identity between nataliakulikite and synthetic Ca₄Ti₂Fe³⁺₂O₁₁ (2CaTiO₃∙Ca₂Fe³⁺₂O₅), an intermediate compound in the system CaTiO₃-Ca₂Fe³⁺₂O₅. In general, this mineral is a Si-Fe²⁺-rich natural analog of synthetic Ca₄Ti₂Fe³⁺₂O₁₁. The X-ray powder diffraction data (CuKα -radiation), calculated from unit-cell dimensions, show the strongest lines {d [Å], (I_calc)} at: 2.681(100), 1.898(30), 2.627(26), 2.744(23), 1.894(22), 15.151(19), 1.572(14), 3.795(8). The calculated density is 4.006 g/cm³. The crystal structure of nataliakulikite has not been refined because of small sizes of grains. The Raman spectrum shows strong bands at 128, 223, 274, 562, and 790 cm⁻¹. Nataliakulikite from the Hatrurim Basin crystallized under the conditions of combustion metamorphism at high temperatures (1160–1200 °C) and low pressures (HT-region of the spurrite-merwinite facies). Full article

(This article belongs to the Special Issue Mineral Formation in Pyrometamorphic Process)

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16 pages, 5417 KiB

Open AccessArticle

The Contribution of Long-Terms Static Interactions Between Minerals and Flotation Reagents for the Separation of Fluorite and Calcite

by Leiming Huang, Qiang Zeng, Liang Hu, Yuehua Hu, Hui Zhong and Zhiguo He

Minerals 2019, 9(11), 699; https://doi.org/10.3390/min9110699 - 12 Nov 2019

Cited by 11 | Viewed by 2774

Abstract

The influences of long-term static interaction between flotation reagents and minerals on mineral surface properties and their flotation behaviors were investigated in this work. Single mineral results showed that when the static interaction time between flotation reagents and minerals increased from 0 to [...] Read more.

The influences of long-term static interaction between flotation reagents and minerals on mineral surface properties and their flotation behaviors were investigated in this work. Single mineral results showed that when the static interaction time between flotation reagents and minerals increased from 0 to 8 days, there were no significant differences in the recovery of fluorite (ranging from 77.50% to 74.50%), while the recovery of calcite dramatically decreased from 97.17% to 41.13%. The collector adsorption results indicated that after the long-term static interaction between the collector and minerals, adsorption and desorption of collector on the minerals occurred, and the adsorption amount of collector on fluorite and calcite varied from 0.396 mg/g to 0.421 mg/g, and from 0.444 mg/g to 0.404 mg/g, respectively. The contact angles of fluorite and calcite decreased from 134.3° and 105.0° for 0 days to 109.7° and 52.5° for 8 days, respectively, which demonstrated that the fluorite had a higher hydrophobicity than that of calcite after 8 days of static interaction between the minerals and collector. The Fourier transform infrared spectroscopy (FTIR) analysis showed that there were chemisorptions between the collector and the surfaces of the fluorite and calcite. Meanwhile, the X-ray photoelectron spectroscopy (XPS) results further elucidated that the amount of C=O from the oleic acid (OA) molecule for calcite treated for 8 days was less than for that treated for 0 days. In addition, the flotation results of the tailings from Jiangxi containing fluorite and calcite, indicated that the grade and recovery of fluorite increased from 87.18% and 40.99% for 0 days to 93.00% and 46.01% for 8 days, respectively, indicating that the separation of fluorite from calcite could be achieved via increasing the long-term static interaction between the flotation reagents and minerals. Full article

(This article belongs to the Special Issue Surface Chemistry in Mineral Processing and Extractive Metallurgy)

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10 pages, 6807 KiB

Open AccessArticle

The Occurrence States of Rare Earth Elements Bearing Phosphorite Ores and Rare Earth Enrichment Through the Selective Reverse Flotation

by Wenxiang Chen, Feng Zhou, Hongquan Wang, Sen Zhou and Chunjie Yan

Minerals 2019, 9(11), 698; https://doi.org/10.3390/min9110698 - 12 Nov 2019

Cited by 10 | Viewed by 4147

Abstract

The reserve of rare-earth element-bearing phosphorite ores in Guizhou province in western China is huge. Increased demand for the different products manufactured from rare-earth elements has resulted in an extreme need for reasonable and comprehensive extraction of rare-earth elements. An improved understanding of [...] Read more.

The reserve of rare-earth element-bearing phosphorite ores in Guizhou province in western China is huge. Increased demand for the different products manufactured from rare-earth elements has resulted in an extreme need for reasonable and comprehensive extraction of rare-earth elements. An improved understanding of rare-earth element occurrence states in single minerals of ores is important for their further processing. In this paper, rare-earth element contents were analyzed by inductively coupled plasma (ICP), and the occurrence states in single minerals were further investigated through SEM-EDS and focused ion beam-scanning electron microscope (FIB-SEM) methods. The results indicate that rare-earth element contents of apatite are far more than that of dolomite. No independent mineral of rare-earth elements exists for the studied sample. Rare-earth elements are present in the form of ions in the lattices of apatite. Based on the analysis of occurrence states and properties in single minerals, the distribution of rare-earth elements in the flotation process was investigated by reverse flotation technology. It shows that rare-earth elements are mainly concentrated in apatite concentrate. Under the optimized conditions, the P₂O₅ grade increases from 11.36% in the raw ore to 26.04% in the concentrate, and the recovery is 81.92%, while the total rare-earth oxide grade increases from 0.09% to 0.21% with the recovery of 80.01%, which is similar to P₂O₅ recovery. This study presents the feasibility of extracting rare-earth elements from rare-earth element-bearing phosphorite ores through the flotation of apatite. Full article

(This article belongs to the Special Issue Interface Science in Mineral (Bio)Processing)

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14 pages, 1895 KiB

Open AccessArticle

Selective Parameters and Bioleaching Kinetics for Leaching Vanadium from Red Mud Using Aspergillus niger and Penicillium tricolor

by Yang Qu, Hui Li, Xiaoqing Wang, Wenjie Tian, Ben Shi, Minjie Yao, Lina Cao and Lingfan Yue

Minerals 2019, 9(11), 697; https://doi.org/10.3390/min9110697 - 11 Nov 2019

Cited by 15 | Viewed by 3136

Abstract

In the present study, using Aspergillus niger and Penicillium tricolor, the influence of the selected parameters, including sucrose concentration, inoculation size of spores, pulp density, and pre-culture time, on the bioleaching efficiency (biomass, organic acids production, and vanadium extraction, respectively) of red [...] Read more.

In the present study, using Aspergillus niger and Penicillium tricolor, the influence of the selected parameters, including sucrose concentration, inoculation size of spores, pulp density, and pre-culture time, on the bioleaching efficiency (biomass, organic acids production, and vanadium extraction, respectively) of red mud were studied. The bioleaching kinetics under optimal conditions were also explored. Sucrose concentration showed a positive linear effect on bioleaching efficiency below 143.44 and 141.82 g/L using A. niger and P. tricolor, respectively. However, a higher concentration was unfavorable for vanadium extraction. The inoculation size of spores showed an insignificant effect on both biomass and vanadium extraction if it exceeded the lowest coded levels (0.5 × 10⁷/mL). Red mud pulp density showed a negative effect on the bioleaching efficiency of A. niger but a positive effect on organic acids production and vanadium extraction of P. tricolor. A pre-culture was indispensable for A. niger but not for P. tricolor due to the fact of its isolation from the red mud examined in this study. The kinetics analysis showed that the leaching rate of vanadium followed a two-domain behavior: initially, a rapid leaching period of approximately 10–15 days and, subsequently, a slow leaching period. Considering the change of the particles’ appearance as well as in the elemental composition of the bioleached red mud, it is speculated that the rate of leaching agents through the silicon minerals was the rate-limiting step of dissolution kinetics under the fungal bioleaching process. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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31 pages, 5465 KiB

Open AccessEditor’s ChoiceReview

Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry

by Emilia García-Romero, Eva María Manchado, Mercedes Suárez and Javier García-Rivas

Minerals 2019, 9(11), 696; https://doi.org/10.3390/min9110696 - 11 Nov 2019

Cited by 25 | Viewed by 6082

Abstract

A review and a synthesis of the geological, mineralogical, and crystal chemical data available in the literature on active Spanish bentonitic exploitations were done, and at the same time, new data are provided from a set of representative samples from these deposits. They [...] Read more.

A review and a synthesis of the geological, mineralogical, and crystal chemical data available in the literature on active Spanish bentonitic exploitations were done, and at the same time, new data are provided from a set of representative samples from these deposits. They were located in three different areas with different geological origins: (1) Miocene sedimentary deposits from the Tajo Basin (Madrid–Toledo provinces) in the center of the Iberian Peninsula, where bentonites appear in two different units named for their colors (Green Clays and Pink Clays); (2) samples from Tamame de Sayago (Zamora province) originating from the hydrothermal alteration of granitic Variscan rocks; and 3) Miocene deposits originating from the hydrothermal alteration of volcanic or subvolcanic rocks from the Cabo de Gata volcanic area (Almería Province) in the southern part of Spain, where the three main deposits (Cortijo de Archidona, Los Trancos, and Morrón de Mateo) were studied. The bentonites from the Tajo Basin were formed mainly by trioctahedral smectites, and there were significant mineralogical differences between the Green and Pink Clays, both in terms of the contents of impurities and in terms of smectite crystallochemistry and crystallinity. The smectites from Tamame de Sayago were dioctahedral (montmorillonite–beidellite series), and they appeared with kaolinite, quartz, and mica in all possible proportions, from almost pure bentonite to kaolin. Finally, the compositions of the bentonites from the three studied deposits in Cabo de Gata were quite similar, and zeolites and plagioclases were the main impurities. The structural formulae of the smectites from Cortijo de Archidona and Los Trancos showed a continuous compositional variation in beidellite–montmorillonite, while in Morrón de Mateo, the smectites were mainly montmorillonite, although there was continuous compositional variation from Al montmorillonites to Fe–Mg-rich saponites. The variation in the smectite composition is due to the intrusion of a volcanic dome, which brings new fluids that alter the initial composition of the smectites. Full article

(This article belongs to the Special Issue Special Clays and Their Applications)

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22 pages, 11077 KiB

Open AccessArticle

Apatite from NWA 10153 and NWA 10645—The Key to Deciphering Magmatic and Fluid Evolution History in Nakhlites

by Łukasz Birski, Ewa Słaby, Elias Chatzitheodoridis, Richard Wirth, Katarzyna Majzner, Gabriela A. Kozub-Budzyń, Jiří Sláma, Katarzyna Liszewska, Izabela Kocjan and Anna Zagórska

Minerals 2019, 9(11), 695; https://doi.org/10.3390/min9110695 - 10 Nov 2019

Cited by 8 | Viewed by 4347

Abstract

Apatites from Martian nakhlites NWA 10153 and NWA 10645 were used to obtain insight into their crystallization environment and the subsequent postcrystallization evolution path. The research results acquired using multi-tool analyses show distinctive transformation processes that were not fully completed. The crystallization history [...] Read more.

Apatites from Martian nakhlites NWA 10153 and NWA 10645 were used to obtain insight into their crystallization environment and the subsequent postcrystallization evolution path. The research results acquired using multi-tool analyses show distinctive transformation processes that were not fully completed. The crystallization history of three apatite generations (OH-bearing, Cl-rich fluorapatite as well as OH-poor, F-rich chlorapatite and fluorapatite) were reconstructed using transmission electron microscopy and geochemical analyses. Magmatic OH-bearing, Cl-rich fluorapatite changed its primary composition and evolved toward OH-poor, F-rich chlorapatite because of its interaction with fluids. Degassing of restitic magma causes fluorapatite crystallization, which shows a strong structural affinity for the last episode of system evolution. In addition to the three apatite generations, a fourth amorphous phase of calcium phosphate has been identified with Raman spectroscopy. This amorphous phase may be considered a transition phase between magmatic and hydrothermal phases. It may give insight into the dissolution process of magmatic phosphates, help in processing reconstruction, and allow to decipher mineral interactions with hydrothermal fluids. Full article

(This article belongs to the Special Issue Mineralogy of Meteorites)

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23 pages, 12557 KiB

Open AccessArticle

Obtaining Hyperspectral Signatures for Seafloor Massive Sulphide Exploration

by Øystein Sture, Ben Snook and Martin Ludvigsen

Minerals 2019, 9(11), 694; https://doi.org/10.3390/min9110694 - 10 Nov 2019

Cited by 10 | Viewed by 3539

Abstract

Seafloor massive sulphide (SMS) deposits are hosts to a wide range of economic minerals, and may become an important resource in the future. The exploitation of these resources is associated with considerable expenses, and a return on investment may depend on the availability [...] Read more.

Seafloor massive sulphide (SMS) deposits are hosts to a wide range of economic minerals, and may become an important resource in the future. The exploitation of these resources is associated with considerable expenses, and a return on investment may depend on the availability of multiple deposits. Therefore, efficient exploration methodologies for base metal deposits are important for future deep sea mining endeavours. Underwater hyperspectral imaging (UHI) has been demonstrated to be able to differentiate between different types of materials on the seafloor. The identification of possible end-members from field data requires prior information in the form of representative signatures for distinct materials. This work presents hyperspectral imaging applied to a selection of materials from the Loki’s Castle active hydrothermal vent site in a laboratory setting. A methodology for compensating for systematic effects and producing the reflectance spectra is detailed, and applied to recover the spectral signatures from the samples. The materials investigated were found to be distinguishable using unsupervised dimensionality reduction methods, and may be used as a reference for future field application. Full article

(This article belongs to the Special Issue Hyperspectral Imaging for Mineral Mapping)

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9 pages, 8784 KiB

Open AccessArticle

Cracked, Porous Rocks and Fluids: Moon and Earth Paradox

by Jan V.M. Borgomano, Jérôme Fortin and Yves Guéguen

Minerals 2019, 9(11), 693; https://doi.org/10.3390/min9110693 - 9 Nov 2019

Cited by 1 | Viewed by 2841

Abstract

Elastic wave velocities are key parameters in geosciences. In seismology at a large scale, or in seismic exploration at a more local and shallower scale, they were the main source of information for a long time. At the time of the Apollo mission, [...] Read more.

Elastic wave velocities are key parameters in geosciences. In seismology at a large scale, or in seismic exploration at a more local and shallower scale, they were the main source of information for a long time. At the time of the Apollo mission, Anderson explained the unexpected result of very low velocities in Moon surface rocks by an intense cracking resulting from meteoritic impacts. Yet, it was also known that the Q factor was high. This could appear as a paradox. In the shallow layers of the Earth, rocks are porous. These shallow layers are of major importance in the Earth since they contain fluids. This is why velocities are higher and Q values lower in the Earth’s shallow layers than in the Moon’s shallow layers. Cracks have a determining effect on elastic properties because they are very compliant. Fluids also play a key role. Combining poroelasticity and effective elasticity, two independent theories much developed since the time of the Apollo mission, makes it possible to revisit the contrasting results observed in the Moon case and in the Earth case. Experimental results obtained on cracked synthetic glass show that dry cracks result in a strong decrease in velocity. On the other hand, saturated porous limestones exhibit a strong frequency-dependent attenuation when thermally cracked. The presence of fluid is the key factor. Full article

(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)

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7 pages, 200 KiB

Open AccessEditorial

Editorial for Special Issue “Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes”

by Cristiana L. Ciobanu, Satoshi Utsunomiya, Martin Reich, Oliver Plümper and Nigel J. Cook

Minerals 2019, 9(11), 692; https://doi.org/10.3390/min9110692 - 9 Nov 2019

Cited by 3 | Viewed by 2374

Abstract

Minerals form in all types of chemical and physical environments [...] Full article

(This article belongs to the Special Issue Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes)

17 pages, 4695 KiB

Open AccessArticle

The Study of Crystal Structure on Grossular–Andradite Solid Solution

by Yichuan Wang, Qiang Sun, Dengfei Duan, Xinjian Bao and Xi Liu

Minerals 2019, 9(11), 691; https://doi.org/10.3390/min9110691 - 8 Nov 2019

Cited by 10 | Viewed by 4345

Abstract

The effects of Al³⁺–Fe³⁺ substitution on 10 synthesized garnet samples along the grossular–andradite binary solid solution were investigated using both powder and single-crystal X-ray diffraction. Results showed that cell volume increased with andradite content. Small negative excess volume was observed [...] Read more.

The effects of Al³⁺–Fe³⁺ substitution on 10 synthesized garnet samples along the grossular–andradite binary solid solution were investigated using both powder and single-crystal X-ray diffraction. Results showed that cell volume increased with andradite content. Small negative excess volume was observed in the Al-rich samples. By measuring the bond length, polyhedral volume, octahedral distortion parameter (σ), and tetrahedral rotation angle (α), we determined that the distortion occurred on the dodecahedral site. The width of the diffraction peaks was obviously related to the composition of the solid solution. Full width at half maximum of diffraction peaks was used to calculate the microstrain, which may have a relationship with enthalpy of mixing. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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9 pages, 1192 KiB

Open AccessArticle

Hydrogen Effect on the Sound Velocities of Upper Mantle Omphacite

by Wade Mans, Jin S. Zhang, Ming Hao, Joseph R. Smyth, Dongzhou Zhang, Gregory J. Finkelstein and Przemyslaw Dera

Minerals 2019, 9(11), 690; https://doi.org/10.3390/min9110690 - 8 Nov 2019

Cited by 2 | Viewed by 3061

Abstract

Clinopyroxene (Cpx) is commonly believed to be the best structural water (hydrogen) carrier among all major upper mantle nominally anhydrous minerals (NAMs). In this study, we have measured the single-crystal elastic properties of a Cpx, a natural omphacite with ~710 ppm water at [...] Read more.

Clinopyroxene (Cpx) is commonly believed to be the best structural water (hydrogen) carrier among all major upper mantle nominally anhydrous minerals (NAMs). In this study, we have measured the single-crystal elastic properties of a Cpx, a natural omphacite with ~710 ppm water at ambient pressure (P) and temperature (T) conditions. Utilizing the single-crystal X-ray diffraction (XRD) and electron microprobe data, the unit cell parameters and density were determined as a = 9.603(9) Å, b = 8.774(3) Å, c = 5.250(2) Å, β = 106.76(5)^o, V = 255.1(4) Å³, and ρ = 3.340(6) g/cm³. We performed Brillouin spectroscopy experiments on four single crystals along a total of 52 different crystallographic directions. The best-fit single-crystal elastic moduli (C_ijs), bulk and shear moduli were determined as: C₁₁ = 245(1) GPa, C₂₂ = 210(2) GPa, C₃₃ = 249.6(9) GPa, C₄₄ = 75.7(9) GPa, C₅₅ = 71.2(5) GPa, C₆₆ = 76(1) GPa, C₁₂ = 85(2) GPa, C₁₃ = 70(1) GPa, C₂₃ = 66(2) GPa, C₁₅ = 8.0(6) GPa, C₂₅ = 6(1) GPa, C₃₅ = 34.7(6) GPa, and C₄₆ = 8.7(7) GPa, K_S0 = 125(3) GPa, and G₀ = 75(2) GPa, respectively. Compared with the anticipated elastic properties of an anhydrous omphacite with the same chemical composition, our results indicate that the incorporation of ~710 ppm structural water has no resolvable effect on the aggregate elastic properties of omphacite, although small differences (up to ~9 GPa) were observed in C₁₃, C₂₅, C₄₄, and C₆₆. Full article

(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)

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22 pages, 12013 KiB

Open AccessArticle

Geochronology and Geochemistry of Archean TTG and Tremolite Schist Xenoliths in Yemadong Complex: Evidence for ≥3.0 Ga Archean Continental Crust in Kongling High-Grade Metamorphic Terrane, Yangtze Craton, China

by Yunxu Wei, Wenxiao Zhou, Zhengxiang Hu, Haiquan Li, Xianxiao Huang, Xiaoming Zhao and Daliang Xu

Minerals 2019, 9(11), 689; https://doi.org/10.3390/min9110689 - 8 Nov 2019

Cited by 15 | Viewed by 4782

Abstract

The origin and significance of the tonalite–trondhjemite–granodiorite (TTG) units and the familiar metabasite xenoliths they host in the Yangtze Craton, China, remain controversial, and resolving these issues is important if we are to understand the evolution of the early Yangtze Craton. We focused [...] Read more.

The origin and significance of the tonalite–trondhjemite–granodiorite (TTG) units and the familiar metabasite xenoliths they host in the Yangtze Craton, China, remain controversial, and resolving these issues is important if we are to understand the evolution of the early Yangtze Craton. We focused on biotite–tremolite schist xenoliths in the Archean TTG units of the Kongling high-grade metamorphic terrane, and U–Pb dating of their zircons yielded ²⁰⁷Pb/²⁰⁶Pb ages of ca. 3.00 Ga, which provides a minimum age for the formation of the pre-metamorphic basic igneous rock. The host TTGs and late intrusive granitic dikes yield three groups of upper intercept ages at 2.87–2.88, 2.91–2.94, and 3.07 Ga, and a concordant age at 2.94 Ga, which suggest that the Yangtze continental nucleus underwent three important metamorphic–magmatic events in the Mesoarchean at ca. 3.00, 2.94, and 2.87 Ga. The biotite–tremolite schists have high ratios of K₂O/Na₂O and high contents of CaO, Cr, and Ni, thus showing the characteristics of high-K calc-alkaline island-arc volcanic rocks (basalt–andesite) that form by the partial melting of subducted oceanic crust. The data also provide further proof that a Mesoarchean metamorphic basement exists in the Yangtze Plate. Derivation of the magmatic protoliths of the biotite–tremolite schist enclaves from an oceanic crust during slab subduction, and the presence of these xenoliths within the TTG suite, indicate the existence of the initiation of plate tectonics during the Mesoarchean (≤2.94 Ga). Full article

(This article belongs to the Special Issue Geochemistry of Granites and Granitic Pegmatites)

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20 pages, 2954 KiB

Open AccessArticle

Geochemical Footprint of Megacities on River Sediments: A Case Study of the Fourth Most Populous Area in India, Chennai

by Sukkampatti Palanisamy Saravanan, Marc Desmet, Ambujam Neelakanta Pillai Kanniperumal, Saravanan Ramasamy, Nikita Shumskikh and Cécile Grosbois

Minerals 2019, 9(11), 688; https://doi.org/10.3390/min9110688 - 7 Nov 2019

Cited by 9 | Viewed by 4398

Abstract

An intensive surface sediment survey was carried out over 24 locations from the upstream to downstream sections of two large rivers (Adyar and Cooum) in Chennai (India) during the February dry season of 2015. Trace element concentrations were assessed on a <63 µm [...] Read more.

An intensive surface sediment survey was carried out over 24 locations from the upstream to downstream sections of two large rivers (Adyar and Cooum) in Chennai (India) during the February dry season of 2015. Trace element concentrations were assessed on a <63 µm fraction using the Geoaccumulation Index (I_geo) and the newly proposed Geochemical Urban Footprint Index (GUFI), which can be performed to determine the pollution status of any megacity river influenced by urban development. The sediment quality of Chennai’s rivers was also compared to worldwide megacity pollution using sediment quality guidelines (SQGs), and a new megacity pollution ranking was determined. The I_geo results indicate that the Chennai rivers studied are strongly to extremely polluted regarding trace element content of sediment. Silver (Ag), Cadmium (Cd) and Mercury (Hg) are the most significant tracers of urban contamination. Chromium (Cr) concentrations show an industrial contamination gradient in relation to levels of other trace elements (As, Cu, Ni, Pb, and Zn) at the Chennai megacity scale. The GUFI ranges from moderate to extreme contamination, particularly in the downstream stretches of the two rivers. This spatial trend is related to various point sources and identified at specific sampling stations, with a lack of identifiable buffer zones. According to the worldwide comparison of megacity pollution, Chennai is ranked in fifth position. The present position can be attributed to a number of explanations: a population explosion associated with the unplanned growth of the city and non-controlled point sources of pollution in Chennai’s waterways. Full article

(This article belongs to the Special Issue Metallic Elements in Sediments)

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13 pages, 6636 KiB

Open AccessArticle

Effect of a Small Amount of Iron Impurity in Sphalerite on Xanthate Adsorption and Flotation Behavior

by Jiang Yu, Xiqun Wu, Zhiqiang Zhao, Yangge Zhu and Sigang Luo

Minerals 2019, 9(11), 687; https://doi.org/10.3390/min9110687 - 6 Nov 2019

Cited by 7 | Viewed by 2895

Abstract

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study [...] Read more.

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study the influence of small amounts of iron impurity in the sphalerite on xanthate adsorption and flotation behavior. The flotation experiments showed that the flotation recovery increased with the increase in iron impurity content. Fourier Transform infrared spectroscopy (FTIR) and Ultraviolet–visible (UV-VIS) spectra showed that the adsorbed products of xanthate on the surface of three kinds of sphalerite were metal xanthate. The adsorption capacity measurements showed that the saturation absorption of xanthate on sphalerite increased with the increase in iron impurity content. The cyclic voltammetry curve and Tafel curve showed that with the increase in iron impurity content, sphalerite was more easily oxidized and the adsorption rate of xanthate on the surface of sphalerite increased obviously. To summarize, a small amount of iron impurity was beneficial to the recovery of sphalerite. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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Minerals, Volume 9, Issue 11 (November 2019) – 69 articles

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