Previous Issue
Volume 9, August

Table of Contents

Minerals, Volume 9, Issue 9 (September 2019)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Open AccessArticle
Use of Sodium Hexametaphosphate and Citric Acid Mixture as Depressant in the Flotation Separation of Scheelite from Calcite
Minerals 2019, 9(9), 560; https://doi.org/10.3390/min9090560 (registering DOI) - 16 Sep 2019
Abstract
The floatability of scheelite and calcite in the presence of single depressant (SHMP or H3Cit) and mixed depressant (SHMP/H3Cit) was studied by microflotation experiments and artificial mixed mineral experiments. Solution chemical calculation, zeta potential tests, thermodynamic analysis and XPS [...] Read more.
The floatability of scheelite and calcite in the presence of single depressant (SHMP or H3Cit) and mixed depressant (SHMP/H3Cit) was studied by microflotation experiments and artificial mixed mineral experiments. Solution chemical calculation, zeta potential tests, thermodynamic analysis and XPS analysis were used to explain the relevant depressive mechanism. Mixed depressant (SHMP/H3Cit) exhibited excellent selective depressive effect on calcite. The optimal molar ratio of SHMP to H3Cit was 1:4. The depressant SHMP and H3Cit can be chemically bonded with Ca2+ to form CaHPO4 and Ca3(Cit)2 at pH 8. The CaHPO4 was more easily formed than Ca3(Cit)2 on the mineral surface, which indicated that the depressive effect of SHMP was stronger than H3Cit. The SHMP and H3Cit of the mixed depressant were co-adsorbed on the calcite surface, while the H3Cit of the mixed depressant was weakly adsorbed on the scheelite surface. The mixed depressant can significantly improve the separation efficiency of scheelite from calcite. Full article
Show Figures

Graphical abstract

Open AccessArticle
Phase Relations in MAFSH System up to 21 GPa: Implications for Water Cycles in Martian Interior
Minerals 2019, 9(9), 559; https://doi.org/10.3390/min9090559 (registering DOI) - 16 Sep 2019
Abstract
To elucidate the water cycles in iron-rich Mars, we investigated the phase relation of a water-undersaturated (2 wt.%) analog of Martian mantle in simplified MgO-Al2O3-FeO-SiO2-H2O (MAFSH) system between 15 and 21 GPa at 900–1500 °C [...] Read more.
To elucidate the water cycles in iron-rich Mars, we investigated the phase relation of a water-undersaturated (2 wt.%) analog of Martian mantle in simplified MgO-Al2O3-FeO-SiO2-H2O (MAFSH) system between 15 and 21 GPa at 900–1500 °C using a multi-anvil apparatus. Results showed that phase E coexisting with wadsleyite or ringwoodite was at least stable at 15–16.5 GPa and below 1050 °C. Phase D coexisted with ringwoodite at pressures higher than 16.5 GPa and temperatures below 1100 °C. The transition pressure of the loop at the wadsleyite-ringwoodite boundary shifted towards lower pressure in an iron-rich system compared with a hydrous pyrolite model of the Earth. Some evidence indicates that water once existed on the Martian surface on ancient Mars. The water present in the hydrous crust might have been brought into the deep interior by the convecting mantle. Therefore, water might have been transported to the deep Martian interior by hydrous minerals, such as phase E and phase D, in cold subduction plates. Moreover, it might have been stored in wadsleyite or ringwoodite after those hydrous materials decomposed when the plates equilibrated thermally with the surrounding Martian mantle. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
Show Figures

Figure 1

Open AccessArticle
The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts
Minerals 2019, 9(9), 558; https://doi.org/10.3390/min9090558 (registering DOI) - 16 Sep 2019
Abstract
Carbonate micro inclusions with abnormally high K2O appear in diamonds worldwide. However, the precise determination of their chemical and phase compositions is complicated due to their sub-micron size. The K2CO3–CaCO3–MgCO3 is the simplest system [...] Read more.
Carbonate micro inclusions with abnormally high K2O appear in diamonds worldwide. However, the precise determination of their chemical and phase compositions is complicated due to their sub-micron size. The K2CO3–CaCO3–MgCO3 is the simplest system that can be used as a basis for the reconstruction of the phase composition and P–T conditions of the origin of the K-rich carbonatitic inclusions in diamonds. In this regard, this paper is concerned with the subsolidus and melting phase relations in the K2CO3–CaCO3–MgCO3 system established in Kawai-type multianvil experiments at 6 GPa and 900–1300 °C. At 900 °C, the system has three intermediate compounds K2Ca3(CO3)4 (Ca# ≥ 97), K2Ca(CO3)2 (Ca# ≥ 58), and K2Mg(CO3)2 (Ca# ≤ 10), where Ca# = 100Ca/(Ca + Mg). Miscibility gap between K2Ca(CO3)2 and K2Mg(CO3)2 suggest that their crystal structures differ at 6 GPa. Mg-bearing K2Ca(CO3)2 (Ca# ≤ 28) disappear above 1000 °C to produce K2Ca3(CO3)4 + K8Ca3(CO3)7 + K2Mg(CO3)2. The system has two eutectics between 1000 and 1100 °C controlled by the following melting reactions: K2Ca3(CO3)4 + K8Ca3(CO3)7 + K2Mg(CO3)2 → [40K2CO3∙60(Ca0.70Mg0.30)CO3] (1st eutectic melt) and K8Ca3(CO3)7 + K2CO3 + K2Mg(CO3)2 → [62K2CO3∙38(Ca0.73Mg0.27)CO3] (2nd eutectic melt). The projection of the K2CO3–CaCO3–MgCO3 liquidus surface is divided into the eight primary crystallization fields for magnesite, aragonite, dolomite, Ca-dolomite, K2Ca3(CO3)4, K8Ca3(CO3)7, K2Mg(CO3)2, and K2CO3. The temperature increase is accompanied by the sequential disappearance of crystalline phases in the following sequence: K8Ca3(CO3)7 (1220 °C) → K2Mg(CO3)2 (1250 °C) → K2Ca3(CO3)4 (1350 °C) → K2CO3 (1425 °C) → dolomite (1450 °C) → CaCO3 (1660 °C) → magnesite (1780 °C). The high Ca# of about 40 of the K2(Mg, Ca)(CO3)2 compound found as inclusions in diamond suggest (1) its formation and entrapment by diamond under the P–T conditions of 6 GPa and 1100 °C; (2) its remelting during transport by hot kimberlite magma, and (3) repeated crystallization in inclusion that retained mantle pressure during kimberlite magma emplacement. The obtained results indicate that the K–Ca–Mg carbonate melts containing 20–40 mol% K2CO3 is stable under P–T conditions of 6 GPa and 1100–1200 °C corresponding to the base of the continental lithospheric mantle. It must be emphasized that the high alkali content in the carbonate melt is a necessary condition for its existence under geothermal conditions of the continental lithosphere, otherwise, it will simply freeze. Full article
Show Figures

Graphical abstract

Open AccessArticle
CIL Gold Loss Characterization within Oxidized Leach Tails: Creating a Synergistic Approach between Mineralogical Characterization, Diagnostic Leach Tests, and Preg-Robbing Tests
Minerals 2019, 9(9), 557; https://doi.org/10.3390/min9090557 - 16 Sep 2019
Abstract
A double refractory gold ore contains gold particles locked in sulphides, solid-solution in arsenopyrite, and preg-robbing material such as carbonaceous matter, and so on. The diagnostic leach test (DLT) and preg-robbing (PR) approaches are widely used to investigate the occurrence and the distribution [...] Read more.
A double refractory gold ore contains gold particles locked in sulphides, solid-solution in arsenopyrite, and preg-robbing material such as carbonaceous matter, and so on. The diagnostic leach test (DLT) and preg-robbing (PR) approaches are widely used to investigate the occurrence and the distribution of refractory gold. DLT serves to qualitatively evaluate the gold occurrences within the ore. Preg-robbing, or the ore’s capacity to fix dissolved gold, is evaluated to determine physical surface interactions (preg-borrowing) and chemical interactions (preg-robbing). The objective of this project is to characterize the refractory gold in Agnico Eagle Mine’s Kittilä ore using the DLT and PRT approaches coupled with mineralogical analyses to confirm testing. The studied material was sampled from the metallurgical circuit following carbon in leach (CIL) treatment at the outlet of the autoclave in order to investigate the effect of the autoclave treatment on the occurrence and distribution of gold. Different reagents were used in the DLT procedure: sodium carbonate (Na2CO3), sodium hydroxide (NaOH), hydrochloric acid (HCl), and nitric acid (HNO3). The final residue was roasted at a temperature of around 900 °C. These reagents were selected based on the mineralogical composition of the studied samples. After each leaching test/roasting, cyanide leaching with activated carbon was required to recover gold cyanide. The results show that gold is present in two forms (native and/or refractory): to a small extent in its native form and in its refractory form as association with sulfide minerals (i.e., arsenopyrite and pyrite) and autoclave secondary minerals that have been produced during the oxidation and neutralization processes such as iron oxides, iron sulfates, and calcium sulfate (i.e., hematite and jarosite), along with carbonaceous matter. The results of DLT indicate that 25–35% of the gold in the tails is nonrecoverable, as it is locked in silicates, and 20–40% is autoclave products. A regrind can help to mitigate the gold losses by liberating the Au-bearing sulphide minerals encapsulated within silicates. Full article
(This article belongs to the Section Mineral Processing and Metallurgy)
Show Figures

Figure 1

Open AccessArticle
Application of a Maximum Entropy Model for Mineral Prospectivity Maps
Minerals 2019, 9(9), 556; https://doi.org/10.3390/min9090556 - 15 Sep 2019
Viewed by 147
Abstract
The effective integration of geochemical data with multisource geoscience data is a necessary condition for mapping mineral prospects. In the present study, based on the maximum entropy principle, a maximum entropy model (MaxEnt model) was established to predict the potential distribution of copper [...] Read more.
The effective integration of geochemical data with multisource geoscience data is a necessary condition for mapping mineral prospects. In the present study, based on the maximum entropy principle, a maximum entropy model (MaxEnt model) was established to predict the potential distribution of copper deposits by integrating 43 ore-controlling factors from geological, geochemical and geophysical data. The MaxEnt model was used to screen the ore-controlling factors, and eight ore-controlling factors (i.e., stratigraphic combination entropy, structural iso-density, Cu, Hg, Li, La, U, Na2O) were selected to establish the MaxEnt model to determine the highest potential zone of copper deposits. The spatial correlation between each ore-controlling factor and the occurrence of a copper mine was studied using a response curve, and the relative importance of each ore-controlling factor was determined by jackknife analysis in the MaxEnt model. The results show that the occurrence of copper ore is positively correlated with the content of Cu, Hg, La, structural iso-density and stratigraphic combination entropy, and negatively correlated with the content of Na2O, Li and U. The model’s performance was evaluated by the area under the receiver operating characteristic curve (AUC), Cohen’s maximized Kappa and true skill statistic (TSS) (training AUC = 0.84, test AUC = 0.8, maximum Kappa = 0.5 and maximum TSS = 0.6). The results indicate that the model can effectively integrate multi-source geospatial data to map mineral prospectivity. Full article
(This article belongs to the Special Issue Geological Modelling, Volume II)
Show Figures

Figure 1

Open AccessArticle
Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature
Minerals 2019, 9(9), 555; https://doi.org/10.3390/min9090555 - 15 Sep 2019
Viewed by 149
Abstract
In this paper, the adsorption process of methylene blue has been investigated on microcline particles as a function of particle size and temperature. The characterization of microcline in the particle size ranges of 1−71 μm and 71−315 μm gained by sieving was proved [...] Read more.
In this paper, the adsorption process of methylene blue has been investigated on microcline particles as a function of particle size and temperature. The characterization of microcline in the particle size ranges of 1−71 μm and 71−315 μm gained by sieving was proved using X-ray diffraction (XRD) and scanning electron microscopy combined with energy-dispersive detector (SEM-EDS) in powder form, over laser diffraction measurements in aqueous suspension. The optimum dosage of adsorbent was 13.5 g/L in dye adsorption and the adsorption isotherms on both microcline size fractions were determined at this adsorbent concentration. The maximum adsorption capacities were in the range of 1.5–3.1 mg g−1 on microcline particles with supplementing evaluation of isotherms using the Langmuir model. Considering the problems of linearization of equations, the non-linear least-squares estimation can be strongly recommended for modeling adsorption-equilibrium. The adsorption isotherm determined at elevated temperature of 60−65 °C represents a breakpoint at around 20 mg L−1 of equilibrated dye concentration due to performing of a potential process of dye self-association. According to our experiments, the increase in temperature has an adverse effect on adsorption. Full article
(This article belongs to the Special Issue Mineral Sorbents)
Show Figures

Figure 1

Open AccessArticle
The Kilmar Magnesite Deposits: Evaporitic Metasediments in the Grenville Supergroup, Morin Terrane, Quebec
Minerals 2019, 9(9), 554; https://doi.org/10.3390/min9090554 - 14 Sep 2019
Viewed by 168
Abstract
Mesoproterozoic magnesite deposits are found associated with dolomitic marble and intercalated with metasedimentary rocks of the Grenville Supergroup in the granulite facies Morin terrane (Grenville Province, Quebec). This study examines one of the remaining ore deposits exposed on the surface (at the Dobbie [...] Read more.
Mesoproterozoic magnesite deposits are found associated with dolomitic marble and intercalated with metasedimentary rocks of the Grenville Supergroup in the granulite facies Morin terrane (Grenville Province, Quebec). This study examines one of the remaining ore deposits exposed on the surface (at the Dobbie mine), and presents stable isotope and mineralogical data for a marine evaporitic origin. The magnesite ore zone has δ18O(Mag) = 25.5 ± 0.4‰ (VSMOW) and δ13C(Mag) = 1.7 ± 0.2‰ (VPDB; n = 7), while surrounding dolomitic marble has δ18O(Dol) = 24.2 ± 0.6‰ and δ13C(Dol) = −0.2 ± 0.7‰ (n = 11). These values are at the high end of the range for other Morin terrane marbles, and this and sharp transitions in stable isotope ratios between lithologies argue for preservation of evaporitic enrichment in δ18O and δ13C. Boron isotope ratios (δ11B = 15.5‰ to 22.7‰) are also consistent with a marine evaporite origin. Identifying evaporitic protoliths in metasedimentary rocks is important for determining pre-metamorphic depositional environments, and in this case links the sedimentary setting of the Morin terrane to the Adirondack Lowlands (New York, NY, USA). The identification of the Kilmar magnesite deposits as evaporitic also has implications for the formation of sedimentary exhalative base metal deposits in the Grenville Supergroup. Full article
(This article belongs to the Special Issue Minerals of the Southern Grenville Province)
Show Figures

Figure 1

Open AccessArticle
Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments
Minerals 2019, 9(9), 553; https://doi.org/10.3390/min9090553 - 14 Sep 2019
Viewed by 115
Abstract
In deep geoengineering, including geothermal development, deep mining, and nuclear waste geological disposal, high temperature significantly affects the mineral properties of rocks, thereby changing their porous and mechanical characteristics. This paper experimentally studied the changes in mineral composition, pore structure, and mechanical characteristics [...] Read more.
In deep geoengineering, including geothermal development, deep mining, and nuclear waste geological disposal, high temperature significantly affects the mineral properties of rocks, thereby changing their porous and mechanical characteristics. This paper experimentally studied the changes in mineral composition, pore structure, and mechanical characteristics of pyroxene granite heated to high temperature (from 25 °C to 1200 °C). The results concluded that (1) the high-temperature effect can be roughly identified as three stages: 25–500 °C, 500–800 °C, 800–1200 °C. (2) Below 500 °C, the maximum diffracted intensities of the essential minerals are comparatively stable and the porous and mechanical characteristics of granite samples change slightly, mainly due to mineral dehydration and uncoordinated thermal expansion; additionally, the failure mechanism of granite is brittle. (3) In 500–800 °C, the diffraction angles of the minerals become wider, pyroxene and quartz undergo phase transitions, and the difference in thermal expansion among minerals reaches a peak; the rock porosity increases rapidly by 1.95 times, and the newly created pores caused by high heat treatment are mainly medium ones with radii between 1 μm and 10 μm; the P-wave velocity and the elastic modulus decrease by 62.5% and 34.6%, respectively, and the peak strain increases greatly by 105.7%, indicating the failure mode changes from brittle to quasi-brittle. (4) In 800–1200 °C, illite and quartz react chemically to produce mullite and the crystal state of the minerals deteriorate dramatically; the porous and mechanical parameters of granite samples all change significantly and the P-wave, the uniaxial compressive strength (UCS), and the elastic modulus decrease by 81.30%, 81.20%, and 92.52%, while the rock porosity and the shear-slip strain increase by 4.10 times and 11.37 times, respectively; the failure mechanism of granite samples transforms from quasi-brittle to plastic, which also was confirmed with scanning electron microscopy (SEM). Full article
Open AccessArticle
Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China
Minerals 2019, 9(9), 552; https://doi.org/10.3390/min9090552 - 13 Sep 2019
Viewed by 158
Abstract
The biotite pegmatites in the Shangdan domain of the North Qinling orogenic belt contain economic concentrations of U, constituting a low-grade, large-tonnage pegmatite-hosted uraniferous province. Uraninite is predominant and ubiquitous ore mineral and coffinite is common alteration mineral after initial deposit formation. A [...] Read more.
The biotite pegmatites in the Shangdan domain of the North Qinling orogenic belt contain economic concentrations of U, constituting a low-grade, large-tonnage pegmatite-hosted uraniferous province. Uraninite is predominant and ubiquitous ore mineral and coffinite is common alteration mineral after initial deposit formation. A comprehensive survey of the uraninite and coffinite assemblage of the Chenjiazhuang, Xiaohuacha, and Guangshigou biotite pegmatites in this uraniferous province reveal the primary magmatic U mineralization and its response during subsequent hydrothermal events. Integrating the ID-TIMS (Isotope Dilution Thermal Ionization Mass Spectrometry) 206Pb/238U ages and U-Th-Pb chemical ages for the uraninites with those reported from previous studies suggests that the timing of U mineralization in the uraniferous province was constrained at 407–415 Ma, confirming an Early Devonian magmatic ore-forming event. Based on microtextural relationships and compositional variation, three generations of uranium minerals can be identified: uaninite-A (high Th-low U-variable Y group), uranite-B (low Th-high U, Y group), and coffinite (high Si, Ca-low U, Pb group). Petrographic and microanalytical observations support a three-stage evolution model of uranium minerals from primary to subsequent generations as follows: (1) during the Early Devonian (stage 1), U derived from the hydrous silicate melt was mainly concentrated in primary magmatic uaninite-A by high-T (450–607 °C) precipitation; (2) during the Late Devonian (stage 2), U was mobilized and dissolved from pre-existing uraninite-A by U-bearing fluids and in situ reprecipitated as uraninite-B under reduced conditions. The in situ transformation of primary uraninite-A to second uraninite-B represent a local medium-T (250–450 °C) hydrothermal U-event; and (3) during the later low-T (100–140 °C) hydrothermal alteration (stage 3), U was remobilized and derived from the dissolution of pre-existing uraninite by CO2- and SiO2-rich fluids and interacted with reducing agent (e.g., pyrite) leading to reprecipitation of coffinite. This process represents a regional and extensive low-T hydrothermal U-event. In view of this, U minerals evolved from magmatic uraninite-A though fluid-induced recrystallized uraninite-B to coffinite, revealing three episodes of U circulation in the magmatic-hydrothermal system. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Properties of Inorganic Polymers Produced from Brick Waste and Metallurgical Slag
Minerals 2019, 9(9), 551; https://doi.org/10.3390/min9090551 - 12 Sep 2019
Viewed by 129
Abstract
This paper explores the alkali activation potential of brick wastes and metallurgical slags. Inorganic polymers (IPs) were produced using an alkaline medium consisting of sodium hydroxide and sodium silicate solutions and the optimum synthesis conditions were determined. In this context, the variable parameters, [...] Read more.
This paper explores the alkali activation potential of brick wastes and metallurgical slags. Inorganic polymers (IPs) were produced using an alkaline medium consisting of sodium hydroxide and sodium silicate solutions and the optimum synthesis conditions were determined. In this context, the variable parameters, such as solid to liquid (S/L) ratio, curing temperature (60, 80 and 90 °C) and ageing time (7 and 28 days) on the compressive strength and the morphology of the produced IPs were investigated. Specimens produced under the optimum synthesis conditions were subjected to high temperature firing and immersed in distilled water and acidic solutions for various periods of time, in order to assess their durability and structural integrity. The results showed that the IPs produced using a mix ratio of 50 wt % metallurgical slag and 50 wt % brick wastes, cured at 90 °C and aged for 7 days obtained the highest compressive strength (48.9 MPa). X-ray fluorescence analysis (XRF), particle size analysis, Fourier transform infrared spectroscopy (FTIR), mineralogical analysis (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis also confirmed the optimum microstructural characteristics and the chemical reactions that took place during synthesis. The overall results of this study indicate that the co-valorization of different waste streams, which are produced in large quantities and cause environmental problems if not properly managed, is a viable alternative for the production of binders or secondary construction materials with higher added value. Full article
(This article belongs to the Special Issue Metallurgical Slags)
Show Figures

Graphical abstract

Open AccessArticle
Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile
Minerals 2019, 9(9), 550; https://doi.org/10.3390/min9090550 - 12 Sep 2019
Viewed by 102
Abstract
We have determined the Hf isotopic compositions of 12 samples associated with the giant El Teniente Cu-Mo megabreccia deposit, central Chile. The samples range in age from ≥8.9 to 2.3 Ma and provide information about the temporal evolution of their magmatic sources from [...] Read more.
We have determined the Hf isotopic compositions of 12 samples associated with the giant El Teniente Cu-Mo megabreccia deposit, central Chile. The samples range in age from ≥8.9 to 2.3 Ma and provide information about the temporal evolution of their magmatic sources from the Late Miocene to Pliocene. Together with previously published data, the new analysis indicates a temporal decrease of 10 εHf(t) units, from +11.6 down to +1.6, in the 12.7 m.y. from 15 to 2.3 Ma. These variations imply increasing incorporation of continental crust through time in the magmas that formed these rocks. The fact that the samples include mantle-derived olivine basalts and olivine lamprophyres suggests that these continental components were incorporated into their mantle source, and not by intra-crustal contamination (MASH). We attribute the increase, between the Middle Miocene and Pliocene, of crustal components in the subarc mantle source below El Teniente to be due to increased rates of subduction erosion and transport of crust into the mantle. The deposit formed above a large, long-lived, vertically zoned magma chamber that developed due to compressive deformation and persisted between ~7 to 4.6 Ma. Progressively more hydrous mantle-derived mafic magmas feed this chamber from below, providing heat, H2O, S and metals, but no unique “fertile” Cu-rich magma was involved in the formation of the deposit. As the volume of these mantle-derived magmas decreased from the Late Miocene into the Pliocene, the chamber crystallized and solidified, producing felsic plutons and large metal-rich magmatic-hydrothermal breccias that emplaced Cu and S into the older (≥8.9 Ma) mafic host rocks of this megabreccia deposit. Full article
(This article belongs to the Special Issue Role of Magmatic Activity in Generation of Ore Deposits)
Open AccessArticle
Selective Flotation of Pyrite from Galena Using Chitosan with Different Molecular Weights
Minerals 2019, 9(9), 549; https://doi.org/10.3390/min9090549 - 12 Sep 2019
Viewed by 138
Abstract
Pyrite is a major gangue mineral associated with galena and other valuable minerals, and it is necessary to selectively remove pyrite to upgrade the lead concentrate by froth flotation. In this study, the flotation experiments of a single mineral and mixed minerals were [...] Read more.
Pyrite is a major gangue mineral associated with galena and other valuable minerals, and it is necessary to selectively remove pyrite to upgrade the lead concentrate by froth flotation. In this study, the flotation experiments of a single mineral and mixed minerals were performed using chitosan with different molecular weights (MW = 2−3, 3−6, 10 and 100 kDa) as a depressant, ethyl xanthate as a collector, and terpineol as a frother, in a bid to testify the separation of pyrite from galena. Flotation results showed that the selective flotation of pyrite from galena can be achieved under the preferred reagent scheme, i.e., 400 g/t chitosan (10 kDa), 1600 g/t ethyl xanthate, and 100 g/t terpineol, while chitosan with other molecular weights cannot. Furthermore, the results of the zeta potential and contact angle measurements revealed that chitosan (10 kDa) has a strong adsorption on galena yet a very weak adsorption on pyrite at the dosage of 400 g/t. This study showed that chitosan (10 kDa) has great potential in the industrial flotation separation of pyrite from lead concentrates. Full article
(This article belongs to the Section Mineral Processing and Metallurgy)
Show Figures

Graphical abstract

Open AccessArticle
Micropore Structural Heterogeneity of Siliceous Shale Reservoir of the Longmaxi Formation in the Southern Sichuan Basin, China
Minerals 2019, 9(9), 548; https://doi.org/10.3390/min9090548 - 11 Sep 2019
Viewed by 193
Abstract
In recent years, the shale gas in the southern Sichuan Basin has achieved great commercial development, and the Silurian Longmaxi Formation is the main development stratum. In order to solve the problems of great difference production and inaccurate gas content of the Longmaxi [...] Read more.
In recent years, the shale gas in the southern Sichuan Basin has achieved great commercial development, and the Silurian Longmaxi Formation is the main development stratum. In order to solve the problems of great difference production and inaccurate gas content of the Longmaxi Formation shale gas field in the southern Sichuan Basin, based on thin section identification, argon ion polishing-field emission scanning electron microscopy, high pressure mercury injection, low temperature nitrogen adsorption and the fractal method, the micropore structural heterogeneity of the siliceous shale reservoir of the Longmaxi Formation has been studied. The results show the following: The pores of siliceous shale are mainly intergranular pores and organic pores. Image analysis shows that there are obvious differences in size and distribution of shale pores among different types. The micropore structural heterogeneity is as follows: intragranular pore > intergranular pore > organic pore. In the paper, the combination of low temperature nitrogen adsorption method and high-pressure mercury injection method is proposed to characterize the micropore size distribution and fractal dimension, which ensures the credibility of pore heterogeneity. The shale pores are mainly composed of mesopores (2–20 nm), followed by macropores (100–300 nm). For different pore sizes, the fractal dimension from large to small is mesopore, micropore and macropore. Shale pore structure and fractal dimension are correlated with mineral composition and total organic carbon (TOC) content, but the correlation is significantly different in different areas, being mainly controlled by the sedimentary environment and diagenesis. Full article
Open AccessArticle
Fluid Inclusions and S–Pb Isotopes of the Reshui Porphyry Mo Deposit in East Kunlun, Qinghai Province, China
Minerals 2019, 9(9), 547; https://doi.org/10.3390/min9090547 - 11 Sep 2019
Viewed by 131
Abstract
The Reshui porphyry Mo deposit is located in the East Kunlun orogenic belt (EKOB). Molybdenum mineralization is distributed in monzogranite and porphyritic monzogranite rocks, mainly presenting as various types of hydrothermal veinlets in altered wall rocks, and the orebodies are controlled by three [...] Read more.
The Reshui porphyry Mo deposit is located in the East Kunlun orogenic belt (EKOB). Molybdenum mineralization is distributed in monzogranite and porphyritic monzogranite rocks, mainly presenting as various types of hydrothermal veinlets in altered wall rocks, and the orebodies are controlled by three groups of fractures. In this paper, we present the results of fluid-inclusion and isotopic (S and Pb) investigations of the Reshui Mo deposit. The ore-forming process of the deposit can be divided into three stages: an early disseminated molybdenite stage (stage 1), a middle quartz–molybdenite stage (stage 2) and a late quartz–polymetallic sulfide stage (stage 3). The alteration was mainly potassic and silicic in stage 1, silicic in stage 2, and sericitic and silicic in stage 3. Five types of fluid inclusions (FIs) can be distinguished in quartz phenocrysts and quartz veins, namely W, PL (pure liquid inclusions), PV (pure gas inclusions), C (CO2 three-phase inclusions), and S (daughter mineral-bearing inclusions). The homogenization temperatures of fluid inclusions belonging to stages 1 to 3 are 282.3–378 °C, 238.7–312.6 °C and 198.3–228 °C, respectively. The fluid salinities at stages 1 to 3 are 4.65–8.14% NaCl eq., 4.34–42.64% NaCl eq., and 3.55–4.65% NaCl eq., respectively. The fluids of this deposit were generally moderate–high temperature and moderate–low salinity and belong to the H2O–NaCl–CO2 ± CH4 system. The temperature and pressure changed considerably between stage 2 (high–medium-temperature) and stage 3 (low-temperature). The evidence for ore-forming fluids containing different types of coexisting inclusions in stage 2 and a decrease in the fluid temperature from stage 2 to stage 3 indicate that fluid boiling and fluid mixing were the main mechanisms of ore precipitation. The sulfide 34SV-CDT values range from 4.90‰ to 5.80‰, which is characteristic of magmatic sulfur. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the ore minerals are 18.210–18.786, 15.589–15.723, and 38.298–39.126, respectively. These lead isotopic compositions suggest that the ores were mainly sourced from crustally derived magmas, with minor input from the mantle. The fluid inclusions and S–Pb isotopes provide important information on the genesis of the Reshui porphyry Mo deposit and indicate that the Triassic has high metallogenic porphyry potential in the EKOB. Full article
(This article belongs to the Section Mineral Deposits)
Show Figures

Graphical abstract

Open AccessArticle
Evidence for a Carbonatite-Influenced Source Assemblage for Intraplate Basalts from the Buckland Volcanic Province, Queensland, Australia
Minerals 2019, 9(9), 546; https://doi.org/10.3390/min9090546 - 10 Sep 2019
Viewed by 195
Abstract
Eastern Australia contains a widespread suite of primitive (MgO ≥ 7.5 wt.%) intraplate basaltic provinces, including those sited along the longest continental hotspot track on Earth (≈2000 km), the Cosgrove track. The Buckland volcanic province is the most southerly basaltic province on the [...] Read more.
Eastern Australia contains a widespread suite of primitive (MgO ≥ 7.5 wt.%) intraplate basaltic provinces, including those sited along the longest continental hotspot track on Earth (≈2000 km), the Cosgrove track. The Buckland volcanic province is the most southerly basaltic province on the Cosgrove track before a >1600 km stretch that contains only sparse leucitite volcanism. Buckland is also situated just northeast of the edge of thick cratonic lithosphere where it transitions to a thinner continental lithosphere (<110 km) to the east, which may influence the production of plume-derived melts. Here, analysis of minor and trace elements in olivines in alkali basalts and basanites from the Buckland Province are combined with whole-rock compositions to elucidate the mantle source assemblages, and to calibrate minor and trace element indicators in olivine for application to source mineralogy. Olivine xenocrysts show element concentration ranges typical for peridotites; Mn and Al concentrations indicate that the ambient mantle is spinel, rather than garnet, peridotite. High modal pyroxene content is indicated by high Ni, Zn/Fe, and Fe/Mn in olivines, while high Ti/Sc is consistent with amphibole in the source. Residual phlogopite in the source of the basanites is indicated by low K/Nb in whole rocks, while apatite contains high P2O5 and low Rb/Sr (≥0.015) and Sr/La (≥13). The basanite source assemblage probably contains apatite, phlogopite, olivine, clinopyroxene and orthopyroxene, whereas the alkali basalt source assemblage is probably amphibole, olivine, orthopyroxene and clinopyroxene ± phlogopite ± apatite. Both source assemblages correspond broadly to olivine websterite, with the basanite source lying deeper than that for alkali basalt, explaining the occurrence of phlogopite in the source. This mineralogy, along with whole-rock Ti/Eu, Zr/Hf and P2O5/TiO2 values approaching those of natural carbonatites, provide evidence showing that the Buckland source consists of a peridotite that has interacted with a carbonate-rich melt whose origin may be in the deep lithosphere or asthenosphere beneath the craton. Similar enrichment processes are probably common throughout eastern Australia, controlling trace element characteristics in basaltic provinces. The topography of the underside of the lithosphere may play a significant role in determining mantle source assemblages by diverting and concentrating melt flow, and thus influence the location of basaltic provinces. Full article
Show Figures

Figure 1

Open AccessArticle
Distribution, Enrichment and Transport of Trace Metals in Sediments from the Dagu River Estuary in the Jiaozhou Bay, Qingdao, China
Minerals 2019, 9(9), 545; https://doi.org/10.3390/min9090545 - 10 Sep 2019
Viewed by 180
Abstract
26 river bank sediments and 15 estuary seafloor sediments were sampled from the Dagu River and the estuary of Northwestern Jiaozhou Bay to determine contaminations of heavy metals and metalloids (Cu, Pb, Zn, Cr, Cd, Hg and As). The trace metal contents in [...] Read more.
26 river bank sediments and 15 estuary seafloor sediments were sampled from the Dagu River and the estuary of Northwestern Jiaozhou Bay to determine contaminations of heavy metals and metalloids (Cu, Pb, Zn, Cr, Cd, Hg and As). The trace metal contents in sediment from the estuary area were much higher than those of the river. Correlation analysis showed that except for Pb, the metals were mainly controlled by the grain size, and enriched by adsorption of aluminosilicate minerals, Fe/Mn oxides and organic matter in river and estuary sediments. In addition to Cu in some stations, the metals met the requirements of the marine organism and humans for the quality of the marine environment. The concentrations of Cu, Pb, Cr, Hg and As were between the threshold effect level (TEL) and probable effect level (PEL), indicating those metals might have occasional adverse effects. Results of Enrichment Factor values revealed that the entire study area was enriched in Pb and Hg, at moderate environmental risk, but the estuary was more significant. Pb and Hg contaminations in this area were mainly from coal combustion and automobile emissions. River runoff and atmospheric deposition dominated the metals distribution and enrichment in the study area. Contaminants in sediments entering the estuary were further transported to the south and east under the river runoff and reciprocating current in the Jiaozhou Bay. Full article
(This article belongs to the Special Issue Metallic Elements in Sediments)
Show Figures

Figure 1

Open AccessArticle
Mineralogical Imaging for Characterization of the Per Geijer Apatite Iron Ores in the Kiruna District, Northern Sweden: A Comparative Study of Mineral Liberation Analysis and Raman Imaging
Minerals 2019, 9(9), 544; https://doi.org/10.3390/min9090544 - 10 Sep 2019
Viewed by 227
Abstract
The Per Geijer iron oxide apatite deposits are important potential future resources for Luossavaara-Kiirunavaara Aktiebolag (LKAB) which has been continuously mining magnetite/hematite ores in northern Sweden for over 125 years. Reliable and quantitative characterization of the mineralization is required as these ores inherit [...] Read more.
The Per Geijer iron oxide apatite deposits are important potential future resources for Luossavaara-Kiirunavaara Aktiebolag (LKAB) which has been continuously mining magnetite/hematite ores in northern Sweden for over 125 years. Reliable and quantitative characterization of the mineralization is required as these ores inherit complex mineralogical and textural features. Scanning electron microscopy-based analyses software, such as mineral liberation analyzer (MLA) provide significant, time-efficient analyses. Similar elemental compositions of Fe-oxides and, therefore, almost identical backscattered electron (BSE) intensities complicate their discrimination. In this study, MLA and Raman imaging are compared to acquire mineralogical data for better characterization of magnetite and hematite-bearing ores. The different approaches demonstrate advantages and disadvantages in classification, imaging, discrimination of iron oxides, and time consumption of measurement and processing. The obtained precise mineralogical information improves the characterization of ore types and will benefit future processing strategies for this complex mineralization. Full article
Show Figures

Figure 1

Open AccessArticle
Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry
Minerals 2019, 9(9), 543; https://doi.org/10.3390/min9090543 - 09 Sep 2019
Viewed by 176
Abstract
Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion porosimetry (HMIP), and low-pressure N2/CO2 adsorption [...] Read more.
Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion porosimetry (HMIP), and low-pressure N2/CO2 adsorption were used to qualitatively and quantitatively characterize full-scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro-, meso- and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D1 and D2 which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N2 desorption data. The value of D1 is in the range of 2.6480–2.7334 (average of 2.6857), D2 is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D1 and D2. The fractal dimension D1 decreases with increasing average pore diameter, while D2 is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D1, and positive influence D2, while brittle minerals show an opposite effect compared with clay minerals. Full article
(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)
Show Figures

Figure 1

Open AccessArticle
Prospective (Bio)leaching of Historical Copper Slags as an Alternative to Their Disposal
Minerals 2019, 9(9), 542; https://doi.org/10.3390/min9090542 - 09 Sep 2019
Viewed by 214
Abstract
The aim of this study was to evaluate the feasibility of (bio)hydrometallurgical methods for metal extraction from historical copper slags. Two types of slags (amorphous slag—AS, and crystalline slag—CS) were subjected to 24 to 48 h of leaching with: (i) Sulfuric acid at [...] Read more.
The aim of this study was to evaluate the feasibility of (bio)hydrometallurgical methods for metal extraction from historical copper slags. Two types of slags (amorphous slag—AS, and crystalline slag—CS) were subjected to 24 to 48 h of leaching with: (i) Sulfuric acid at 0.1, 0.5, and 1 M concentrations at 1%, 5%, and 10% pulp densities (PDs); and (ii) normality equivalent (2 N) acids (sulfuric, hydrochloric, nitric, citric, and oxalic) at pulp densities ranging from 1% to 2%. Bioleaching experiments were performed within 21 days with Acidithiobacillus thiooxidans accompanied by an abiotic control (sterile growth medium). The results demonstrated that the most efficient treatment for amorphous and crystalline slag was bioleaching at 1% PD over 21 days, which led to extraction of Cu at rates of 98.7% and 52.1% for AS and CS, respectively. Among the chemical agents, hydrochloric acid was the most efficient and enabled 30.5% of Cu to be extracted from CS (1% PD, 48 h) and 98.8% of Cu to be extracted from AS (1% PD, 24 h). Slag residues after leaching were characterized by strong alteration features demonstrated by the complete dissolution of fayalite in the case of CS and the transformation of AS to amorphous silica and secondary gypsum. Based on this study, we conclude that amorphous slag is a more suitable candidate for potential metal recovery because of its generally high susceptibility to leaching and due to the generation of residue significantly depleted in metals as the end product. The inventory of economically relevant metals showed that 1 ton of historical copper slag contains metals valued at $47 and $135 for crystalline and amorphous slag, respectively, suggesting that secondary processing of such materials can potentially be both economically and environmentally viable. Full article
(This article belongs to the Special Issue Metallurgical Slags)
Show Figures

Figure 1

Open AccessArticle
Joint Inversion of 2D Gravity Gradiometry and Magnetotelluric Data in Mineral Exploration
Minerals 2019, 9(9), 541; https://doi.org/10.3390/min9090541 - 07 Sep 2019
Viewed by 228
Abstract
We have developed a mineral exploration method for the joint inversion of 2D gravity gradiometry and magnetotelluric (MT) data based on data-space and normalized cross-gradient constraints. To accurately explore the underground structure of complex mineral deposits and solve the problems such as the [...] Read more.
We have developed a mineral exploration method for the joint inversion of 2D gravity gradiometry and magnetotelluric (MT) data based on data-space and normalized cross-gradient constraints. To accurately explore the underground structure of complex mineral deposits and solve the problems such as the non-uniqueness and inconsistency of the single parameter inversion model, it is now common practice to perform collocated MT and gravity surveys that complement each other in the search. Although conventional joint inversion of MT and gravity using model-space can be diagnostic, we posit that better results can be derived from the joint inversion of the MT and gravity gradiometry data using data-space. Gravity gradiometry data contains more abundant component information than traditional gravity data and can be used to classify the spatial structure and location of underground structures and field sources more accurately and finely, and the data-space method consumes less memory and has a shorter computation time for our particular inversion iteration algorithm. We verify our proposed method with synthetic models. The experimental results prove that our proposed method leads to models with remarkable structural resemblance and improved estimates of electrical resistivity and density and requires shorter computation time and less memory. We also apply the method to field data to test its potential use for subsurface lithofacies discrimination or structural classification. Our results suggest that the imaging method leads to improved characterization of geological targets, which is more conducive to geological interpretation and the exploration of mineral resources. Full article
(This article belongs to the Special Issue Novel Methods and Applications for Mineral Exploration)
Show Figures

Figure 1

Open AccessFeature PaperArticle
Original Calibration of a Garnet Geobarometer in Metapelite
Minerals 2019, 9(9), 540; https://doi.org/10.3390/min9090540 - 06 Sep 2019
Viewed by 199
Abstract
In many metapelitic assemblages, plagioclase is either CaO-deficient or even absent. In such cases, all the widely applied, well-calibrated plagioclase-related geobarometers lose their usage. Fortunately, it has been found that a net-transfer reaction including intracrystalline Fe2+–Ca2+ exchange in garnet is [...] Read more.
In many metapelitic assemblages, plagioclase is either CaO-deficient or even absent. In such cases, all the widely applied, well-calibrated plagioclase-related geobarometers lose their usage. Fortunately, it has been found that a net-transfer reaction including intracrystalline Fe2+–Ca2+ exchange in garnet is pressure-sensitive, therefore, a garnet geobarometer can be empirically calibrated under pressure–temperature (P–T) conditions of 430~895 °C and 1~15 kbar. The chemical composition range of the calibrant garnet is XCa = 0.02~0.29 and XFe = 0.42~0.91, and covers the majority of garnet in metapelite. The total error of this geobarometer was estimated to be within ±1.3 kbar. The application of this garnet geobarometer to metamorphic terranes certifies its applicability, and this geobarometer can play a unique role, especially when plagioclase is absent or CaO-deficient. Metamorphic P–T conditions can be simultaneously determined by the garnet–biotite pair through the application of the present garnet geobarometer in combination with a well-calibrated garnet-biotite geothermometer. Full article
(This article belongs to the Special Issue High- and Ultrahigh-Pressure Rocks)
Show Figures

Figure 1

Open AccessArticle
The Concentration of Asbestos Fibers in Bulk Samples and Its Variation with Grain Size
Minerals 2019, 9(9), 539; https://doi.org/10.3390/min9090539 - 06 Sep 2019
Viewed by 173
Abstract
The aim of this work was to establish whether asbestos fibers homogeneously occur in the different fractions ground from naturally occurring asbestos lithotypes, and to calculate the contribution of fibers from each fraction to the overall concentration in the sample. Serpentinite, metabasalt, calc-schist, [...] Read more.
The aim of this work was to establish whether asbestos fibers homogeneously occur in the different fractions ground from naturally occurring asbestos lithotypes, and to calculate the contribution of fibers from each fraction to the overall concentration in the sample. Serpentinite, metabasalt, calc-schist, clay, debris material, and soil, were addressed. Grain size fractions below 20 mm were sieved at 2 mm and 0.106 mm; they were then were mechanically milled to obtain powders below 0.106 mm. The three powdered fractions were characterized using a scanning electron microscope coupled with energy dispersive spectroscopy following M.D. 06/09/94. The still in use (in some cases), Italian normative M.D. 161/2012 specifies that analyses must be performed on the <2 mm fraction and the concentration (mg/kg) correlated with the weight of the whole sample <20 mm. However, the fiber counts yielded asbestos concentrations 50–60% lower compared with total asbestos analyses according to the new R.P.D. 120/2017. Consequently, there is a need to standardize the normative worldwide regulations for the management of asbestos-containing materials, by re-evaluation of sample preparation and quantification of asbestos. Full article
Show Figures

Figure 1

Open AccessArticle
Geochemistry, Zircon U-Pb Geochronology and Hf-O Isotopes of the Banzhusi Granite Porphyry from the Xiong’ershan Area, East Qinling Orogen, China: Implications for Petrogenesis and Geodynamics
Minerals 2019, 9(9), 538; https://doi.org/10.3390/min9090538 - 05 Sep 2019
Viewed by 208
Abstract
The Banzhusi granite porphyry is located in the Xiong’ershan area, East Qinling orogenic belt (EQOB). This study presents an integrated whole-rock geochemistry and zircon U-Pb-Hf-O isotope analysis of the Banzhusi granite porphyry. These rocks have metaluminous, high-K alkali-calcic and shoshonitic features and show [...] Read more.
The Banzhusi granite porphyry is located in the Xiong’ershan area, East Qinling orogenic belt (EQOB). This study presents an integrated whole-rock geochemistry and zircon U-Pb-Hf-O isotope analysis of the Banzhusi granite porphyry. These rocks have metaluminous, high-K alkali-calcic and shoshonitic features and show significant enrichment in light rare earth elements (LREEs) over heavy rare earth elements (HREEs) with negative Eu anomalies. These samples are also greatly enriched in Rb, Ba, K, Pb, Th and U and depleted in Nb, Ta, P and Ti, and they mostly overlap the ranges of the Taihua Group tonalite–trondhjemite–granodiorite (TTG) gneiss. Magmatic zircons from three samples of the Banzhusi granite porphyry yield U-Pb ages of 125.1 ± 0.97 Ma, 128.1 ± 1.2 Ma and 128.2 ± 1.3 Ma. The Hf-O isotope features of zircons from the three samples are very similar (δ18Ozircon = 4.84‰ to 6.51‰, εHf(t) = −26.9 to −14.4). The co-variations of geochemical and isotopic data in these granite porphyries imply that the Banzhusi granite porphyry resulted from the mixing of the partially melted Taihua Group and mantle-derived material in a post-collisional setting from 128–125 Ma. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
Show Figures

Figure 1

Open AccessArticle
Multivariate Analysis Based on Geochemical, Isotopic, and Mineralogical Compositions of Uranium-Rich Samples
Minerals 2019, 9(9), 537; https://doi.org/10.3390/min9090537 - 05 Sep 2019
Viewed by 211
Abstract
The chemical and isotopic (U, Pb, Sr) signatures for a suite (n = 23) of pristine (>80 wt. % UO2) and altered uraninite samples (>70–80 wt. % UO2) from various locations worldwide have been determined for the purpose of [...] Read more.
The chemical and isotopic (U, Pb, Sr) signatures for a suite (n = 23) of pristine (>80 wt. % UO2) and altered uraninite samples (>70–80 wt. % UO2) from various locations worldwide have been determined for the purpose of identifying potential fingerprints for nuclear forensic analysis. The characterization of the uraninite samples included determination of major, minor and trace element contents, Sr, Pb, and U isotopic compositions, and secondary mineral assemblages. Due to the multivariate approach adopted in this study, principal component analysis (PCA) has been employed to allow the direct comparison of multiple variable types. The PCA results indicate that the geological origin (sandstone, metamorphite, intrusive, granite and unconformity) of pristine uraninite can be readily identified utilizing various combinations of major and/or trace element concentrations with isotopic compositions. Full article
(This article belongs to the Special Issue Nuclear Forensic Applications in Geoscience and Radiochemistry)
Show Figures

Figure 1

Open AccessArticle
Modeling the Liberation of Comminuted Scheelite Using Mineralogical Properties
Minerals 2019, 9(9), 536; https://doi.org/10.3390/min9090536 - 03 Sep 2019
Viewed by 212
Abstract
In this paper, the modeling of the liberation of scheelite is presented. A pattern of concentration experiments was performed to investigate the scheelite liberation and distribution density calculation procedure. In this work, one sample from a Mittersill tungsten ore was studied. This work [...] Read more.
In this paper, the modeling of the liberation of scheelite is presented. A pattern of concentration experiments was performed to investigate the scheelite liberation and distribution density calculation procedure. In this work, one sample from a Mittersill tungsten ore was studied. This work describes a method for determining the downstream milling energy requirements for rod mill products based on a Bond mill test performance. The grade distribution of particles at a given size fraction was calculated using a predictive liberation model. The concentration behavior of these particles in size fractions was evaluated using batch concentrate tests. The recovery of particles in size/grade classes, image analysis using mineral liberation analysis (MLA), and function calculations were implemented for the modeling of the liberation. By describing the size, grade, and recovery data of particles in size/grade classes, a technique for the measurement of distribution functions was developed that relates beta distribution, a model for the function based on the incomplete beta function, and a solution to produce liberation modeling. It was shown that the predicted results agreed well with the observed results. With a procedure for measuring the liberation, it was possible to carry out the first experimental measurement of the beta distribution. This liberation/concentrate model has wide potential applications for metallurgy and plant design, where the liberation modeling is to be determined with the distribution density solution to the predictive mineral liberation function equation, which includes the liberation of ore samples and their liberation characteristics. Full article
(This article belongs to the Special Issue Mineral Liberation)
Show Figures

Figure 1

Open AccessReview
Occurrence Forms, Composition, Distribution, Origin and Potential Hazard of Natural Hydrogen–Hydrocarbon Gases in Ore Deposits of the Khibiny and Lovozero Massifs: A Review
Minerals 2019, 9(9), 535; https://doi.org/10.3390/min9090535 - 03 Sep 2019
Viewed by 166
Abstract
The Khibiny and Lovozero massifs—the world’s largest alkaline massifs—contain deposits with unique reserves of phosphorus and rare metals, respectively. The reduced gas content in the rocks and, especially, the ore deposits of these massifs is unusually high for igneous complexes, thus representing both [...] Read more.
The Khibiny and Lovozero massifs—the world’s largest alkaline massifs—contain deposits with unique reserves of phosphorus and rare metals, respectively. The reduced gas content in the rocks and, especially, the ore deposits of these massifs is unusually high for igneous complexes, thus representing both geochemical and practical interests. There are three morphological types (or occurrence forms) of the gas phase in these deposits: occluded (predominantly in vacuoles of micro-inclusions in minerals), diffusely dispersed, and free. All three morphological types have the same qualitative chemical gas composition. Methane is the main component, and molecular hydrogen (which sometimes dominates) and ethane are the subordinate constituents. Heavier methane homologs (up to and including pentanes), alkenes, helium, and rarely carbon oxide and dioxide are present in minor or trace amounts. All three morphological types of gases are irregularly distributed in space to various degrees. Free gases also show a release intensity that varies in time. The majority of researchers recognize that the origin of these gases is abiogenic and mostly related to the formation of the massifs and deposits. However, the relative time and mechanism of their generation are still debated. Emissions of combustible and explosive hydrogen–hydrocarbon gases pose hazards during the underground mining of ore deposits. Therefore, the distinctive features of gas-bearing capacity are an essential part of the mining and geological characterization of such deposits because they provide a basis for establishing and implementing special measures of the gas regime during mining operations. Full article
Show Figures

Figure 1

Open AccessArticle
Re-Os Geochronology and Sulfur Isotopes of the Lyangar W-Mo Deposit: Implications for Permian Tectonic Setting in South Tianshan Orogen, Uzbekistan
Minerals 2019, 9(9), 534; https://doi.org/10.3390/min9090534 - 01 Sep 2019
Viewed by 259
Abstract
The Lyangar W-Mo skarn deposit is located in the Nuratau area (western Uzbekistan), South Tianshan Orogen. The skarn system is distributed along the contact zone between the Aktau granitoid and the upper Paleozoic sedimentary rocks. Six molybdenite samples from the Lyangar deposit yielded [...] Read more.
The Lyangar W-Mo skarn deposit is located in the Nuratau area (western Uzbekistan), South Tianshan Orogen. The skarn system is distributed along the contact zone between the Aktau granitoid and the upper Paleozoic sedimentary rocks. Six molybdenite samples from the Lyangar deposit yielded a Middle Permian Re-Os isochron age of 268.0 ± 12.0 Ma (MSWD = 0.43) and a weighted mean age of 263.8 ± 1.5 Ma (MSWD = 0.22). Molybdenites have low Re contents (12.49 to 16.65 ppm), indicative of a continental crust-dominated source. The molybdenite δ34S values fall inside a narrow range (1.0 to 3.8‰; average 2.3‰), implying that the ore metals were likely derived from the granite intrusion. We concluded that the Lyangar W-Mo deposit was formed in a post-collisional setting caused by continental collision between the Tarim and Kazakhstan cratons. Full article
Show Figures

Graphical abstract

Open AccessArticle
Extraction of Boron from Ludwigite Ore: Mechanism of Soda-Ash Roasting of Lizardite and Szaibelyite
Minerals 2019, 9(9), 533; https://doi.org/10.3390/min9090533 - 31 Aug 2019
Viewed by 344
Abstract
Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, [...] Read more.
Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, lizardite and szaibelyite were prepared and their soda-ash roasting behaviors were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) analyses, in order to shed light on the soda-ash activation of boron within ludwigite ore. Thermodynamics of Na2CO3-MgSiO3-Mg2SiO4-Mg2B2O5 via FactSage show that the formation of Na2MgSiO4 was preferential for the reaction between Na2CO3 and MgSiO3/Mg2SiO4. While, regarding the reaction between Na2CO3 and Mg2B2O5, the formation of NaBO2 was foremost. Raising temperature was beneficial for the soda-ash roasting of lizardite and szaibelyite. At a temperature lower than the melting of sodium carbonate (851 °C), the soda-ash roasting of szaibelyite was faster than that of lizardite. Moreover, the melting of sodium carbonate accelerated the reaction between lizardite with sodium carbonate. Full article
(This article belongs to the Special Issue Cleaner Production in Mineral Processing)
Show Figures

Figure 1

Open AccessArticle
Multi-Seam Coal Deposit Modeling via Principal Component Analysis & GIS
Minerals 2019, 9(9), 532; https://doi.org/10.3390/min9090532 - 31 Aug 2019
Viewed by 473
Abstract
Spatial modeling and evaluation is a critical step for planning the exploitation of mineral deposits. In this work, a methodology for the investigation of a multi-seam coal deposit spatial variability is proposed. The study area includes the Klidi (Florina, Greece) multi-seam lignite deposit [...] Read more.
Spatial modeling and evaluation is a critical step for planning the exploitation of mineral deposits. In this work, a methodology for the investigation of a multi-seam coal deposit spatial variability is proposed. The study area includes the Klidi (Florina, Greece) multi-seam lignite deposit which is suitable for surface mining. The analysis is based on the original data of 76 exploratory drill-holes in an area of 10 km2, in conjunction with the geological and geomorphological data of the deposit. The analytical methods include drill-hole data analysis and evaluation based on an appropriate algorithm, principal component analysis and geographic information techniques. The results proved to be very satisfactory for the explanation of the maximum variance of the initial data values as well as the identification of the deposit structure and the optimum planning of mine development. The proposed analysis can be also helpful for minimizing cost and optimizing efficiency of surface mining operations. Furthermore, the provided methods could be applied in other areas of geosciences, indicating the theoretical value as well as the important practical implications of the analysis. Full article
(This article belongs to the Section Mineral Deposits)
Show Figures

Figure 1

Open AccessArticle
Experimental Modeling of Noble and Chalcophile Elements Fractionation during Solidification of Cu-Fe-Ni-S Melt
Minerals 2019, 9(9), 531; https://doi.org/10.3390/min9090531 - 31 Aug 2019
Viewed by 327
Abstract
We carried out a directed crystallization of a melt of the following composition (in mol. %): Fe 31.79, Cu 15.94, Ni 1.70, S 50.20, Sn 0.05, As 0.04, Pt, Pd, Rh, Ru, Ag, Au, Se, Te, Bi, and Sb by 0.03. The obtained [...] Read more.
We carried out a directed crystallization of a melt of the following composition (in mol. %): Fe 31.79, Cu 15.94, Ni 1.70, S 50.20, Sn 0.05, As 0.04, Pt, Pd, Rh, Ru, Ag, Au, Se, Te, Bi, and Sb by 0.03. The obtained cylindrical sample consisted of monosulfide solid solution (mss), nonstoichometric isocubanite (icb*), and three modifications of intermediate solid solution (iss1, iss2, iss3) crystallized from the melt. The simultaneous formation of two types of liquids separated during cooling of the parent sulfide melt was revealed. In the first, concentrations of noble metals associated with Bi, Sb, and Te were found. The second is related to Cu and was found to contain a large amount of S in addition to Bi and Sb. We established the main types of inclusions formed during fractional crystallization of Pt-bearing sulfide melt. It was shown that noble metals are concentrated in inclusions in the form of RuS2, PdTe2, (Pt,Pd)Te2, PtRhAsS, and Ag2Se, doped with Ag, Cu, and Pd, in mss and in the form of PtAs2; Au-doped with Ag, Cu, and Pd; Ag2Te; and Pd(Bi,Sb)xTe1−x in icb* and iss. As solid solutions in the base metal sulfides, Rh is present in mss, Sn in iss. Full article
Show Figures

Graphical abstract

Previous Issue
Back to TopTop