Minerals

10 pages, 2917 KiB

Open AccessArticle

Synthesis of Geopolymers from Mechanically Activated Coal Fly Ash and Improvement of Their Mechanical Properties

by Mitsuaki Matsuoka, Kaho Yokoyama, Kohei Okura, Norihiro Murayama, Masato Ueda and Makio Naito

Minerals 2019, 9(12), 791; https://doi.org/10.3390/min9120791 - 16 Dec 2019

Cited by 12 | Viewed by 2558

Abstract

Coal fly ash is a spherical fine powder by-product discharged from coal-fired power plants. When coal fly ash is used as raw materials for the synthesis of geopolymers, there are practical problems associated with the stable surface of the particles that do not [...] Read more.

Coal fly ash is a spherical fine powder by-product discharged from coal-fired power plants. When coal fly ash is used as raw materials for the synthesis of geopolymers, there are practical problems associated with the stable surface of the particles that do not allow the production of geopolymers with sufficient strength. A long-time is also required for the curing. In this study, we aim to promote the curing reaction of geopolymers by activating the surface of coal fly ash particles. By mechanically activating the surface of coal fly ash particles using an attrition-type mill, the dissolution of Si⁴⁺ and Al³⁺ in coal fly ash is promoted, and the acceleration of the reaction taking place during curing is also anticipated. The surface morphology and crystal phase of coal fly ash particles change with the use of an attrition-type mill. The mechanical activation results in improvement of the compressive strength and the acid resistance under milder curing conditions by the densification of the hardened body. Thus, it is clearly shown that mechanical activation is effective for the production of geopolymers with beneficial mechanical properties under milder curing conditions. Full article

(This article belongs to the Special Issue Mechanochemical Effect in Mineral Processing, Environmental Remediation and Recycling)

► Show Figures

Figure 1

11 pages, 1828 KiB

Open AccessArticle

The High-Pressure Structural Evolution of Olivine along the Forsterite–Fayalite Join

by Martha G. Pamato, Fabrizio Nestola, Davide Novella, Joseph R. Smyth, Daria Pasqual, G. Diego Gatta, Matteo Alvaro and Luciano Secco

Minerals 2019, 9(12), 790; https://doi.org/10.3390/min9120790 - 14 Dec 2019

Cited by 11 | Viewed by 4467

Abstract

Structural refinements from single-crystal X-ray diffraction data are reported for olivine with a composition of Fo₁₀₀ (forsterite Mg₂SiO₄, synthetic), Fo₈₀ and Fo₆₂ (~Mg_1.6Fe_0.4SiO₄ and ~Mg_1.24Fe_0.76SiO₄, [...] Read more.

Structural refinements from single-crystal X-ray diffraction data are reported for olivine with a composition of Fo₁₀₀ (forsterite Mg₂SiO₄, synthetic), Fo₈₀ and Fo₆₂ (~Mg_1.6Fe_0.4SiO₄ and ~Mg_1.24Fe_0.76SiO₄, both natural) at room temperature and high pressure to ~8 GPa. The new results, along with data from the literature on Fo₀ (fayalite Fe₂SiO₄), were used to investigate the previously reported structural mechanisms which caused small variations of olivine bulk modulus with increasing Fe content. For all the investigated compositions, the M2 crystallographic site, with its bonding configuration and its larger polyhedral volume, was observed to control the compression mechanisms in olivine. From Fo₁₀₀ to Fo₀, the compression rates for M2–O and M1–O bond lengths were observed to control the relative polyhedral volumes, resulting in a less-compressible M1O₆ polyhedral volume, likely causing the slight increase in bulk modulus with increasing Fe content. Full article

(This article belongs to the Special Issue Properties of Melt and Minerals at High Pressures and High Temperatures)

► Show Figures

Figure 1

40 pages, 12445 KiB

Open AccessArticle

Lithochemical Stream Sediments of the Dukat Gold–Silver Ore-Forming System (North–East of Russia)

by Artem S. Makshakov, Raisa G. Kravtsova and Vasiliy V. Tatarinov

Minerals 2019, 9(12), 789; https://doi.org/10.3390/min9120789 - 14 Dec 2019

Cited by 2 | Viewed by 3608

Abstract

The composition, structure and formation features of the exogenous anomalous geochemical fields (AGFs) identified by lithochemical stream sediments (LSSs) are considered using the examples of the Dukat gold–silver ore-forming system and the deposit with the same name. The research was carried out in [...] Read more.

The composition, structure and formation features of the exogenous anomalous geochemical fields (AGFs) identified by lithochemical stream sediments (LSSs) are considered using the examples of the Dukat gold–silver ore-forming system and the deposit with the same name. The research was carried out in the Balygychan–Sugoy trough (Magadan region, north–east of Russia). Areal geochemical surveys on the 1:200,000 and 1:50,000 scales were conducted. Exogenous AGFs of basic element indicators of all known mineralization types were studied. It is shown that the surveys on the 1:200,000 scale are characterized by simplicity, relative depth and the possibility to obtain information operatively about the metallogeny of the area as a whole. At the same time, the anomalies were revealed as a result of surveys often making a relatively poor component composition and low contrast compared with ores. The violation of quantitative and sometimes qualitative relationships can be seen between elements, especially those related to gold–silver mineralization. In this situation, the most informative are surveys of LSSs on the 1:50,000 scale. The AGFs were revealed as a result of their performance to have a richer component composition and high contrast, conforming to different ore types. It is shown that, while prospecting for gold–silver mineralization with LSSs in cryolithogenesis zone conditions, the binding forms study of mineralization element indicators is effective. In watercourse heads, where alluvium is practically absent, mosses are proposed for sampling, as they hold the sandy silt material firmly. The obtained results are recommended for use at all stages of prospecting, not only in the north–east of Russia but also in other similar climatic regions. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

► Show Figures

Figure 1

13 pages, 5205 KiB

Open AccessArticle

Application of the Discrete Element Method to Study the Effects of Stream Characteristics on Screening Performance

by Ali Davoodi, Gauti Asbjörnsson, Erik Hulthén and Magnus Evertsson

Minerals 2019, 9(12), 788; https://doi.org/10.3390/min9120788 - 14 Dec 2019

Cited by 13 | Viewed by 3081

Abstract

Screening is a key operation in a crushing plant that ensures adequate product quality of aggregates in mineral processing. The screening process can be divided into the two sub-processes of stratification and passage. The stratification process is affected by the relative difference between [...] Read more.

Screening is a key operation in a crushing plant that ensures adequate product quality of aggregates in mineral processing. The screening process can be divided into the two sub-processes of stratification and passage. The stratification process is affected by the relative difference between various properties, such as particle shape, size distribution, and material density. The discrete element method (DEM) is a suitable method for analyzing the interactions between individual particles and between particles and a screen deck in a controlled environment. The main benefit of using the DEM for simulating the screening process is that this method enables the tracking of individual particles in the material flow, and all of the collisions between particles and between particles and boundaries. This paper presents how different particle densities and flowrates affect material stratification and, in turn, the screening performance. The results of this study show that higher density particles have a higher probability of passage because of their higher stratification rate, which increases the probability that a particle will contact the screen deck during the process. Full article

(This article belongs to the Special Issue Physical Separation and Enrichment)

► Show Figures

Figure 1

10 pages, 2736 KiB

Open AccessArticle

Ultimate Mechanical Properties of Forsterite

by Karine Gouriet, Philippe Carrez and Patrick Cordier

Minerals 2019, 9(12), 787; https://doi.org/10.3390/min9120787 - 14 Dec 2019

Cited by 12 | Viewed by 3509

Abstract

The ultimate mechanical properties, as characterized here by the ideal strengths of Mg₂SiO₄ forsterite, have been calculated using first-principles calculations and generalized gradient approximation under tensile and shear loading. The ideal tensile strengths (ITS) and ideal shear strengths (ISS) are [...] Read more.

The ultimate mechanical properties, as characterized here by the ideal strengths of Mg₂SiO₄ forsterite, have been calculated using first-principles calculations and generalized gradient approximation under tensile and shear loading. The ideal tensile strengths (ITS) and ideal shear strengths (ISS) are computed by applying homogeneous strain increments along high-symmetry directions ([100], [010], and [001]) and low index shear plane ((100), (010), and (001)) of the orthorhombic lattice. We show that the ultimate mechanical properties of forsterite are highly anisotropic, with ITS ranging from 12.1 GPa along [010] to 29.3 GPa along [100], and ISS ranging from 5.6 GPa for simple shear deformation along (100) to 11.5 GPa for shear along (010). Full article

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

► Show Figures

Figure 1

14 pages, 8815 KiB

Open AccessArticle

Mustard Gold in the Oleninskoe Gold Deposit, Kolmozero–Voronya Greenstone Belt, Kola Peninsula, Russia

by Arkadii A. Kalinin, Yevgeny E. Savchenko and Ekaterina A. Selivanova

Minerals 2019, 9(12), 786; https://doi.org/10.3390/min9120786 - 13 Dec 2019

Cited by 8 | Viewed by 3656

Abstract

The Oleninskoe intrusion-related gold–silver deposit is the first deposit in the Precambrian of the Fennoscandian Shield, where mustard gold has been identified. The mustard gold replaces küstelite with impurities of Sb and, probably, gold-bearing dyscrasite and aurostibite. The mosaic structure of the mustard [...] Read more.

The Oleninskoe intrusion-related gold–silver deposit is the first deposit in the Precambrian of the Fennoscandian Shield, where mustard gold has been identified. The mustard gold replaces küstelite with impurities of Sb and, probably, gold-bearing dyscrasite and aurostibite. The mosaic structure of the mustard gold grains is due to different orientations and sizes of pores in the matrix of noble metals. Zonation in the mustard gold grains is connected with mobilization and partial removal of silver from küstelite, corresponding enrichment of the residual matter in gold, and also with the change in the composition of the substance filling the pores. Micropores in the mustard gold are filled with iron, antimony or thallium oxides, silver chlorides, bromides, and sulfides. The formation of mustard gold with chlorides and bromides shows that halogens played an important role in the remobilization of noble metals at the stage of hypergene transformation of the Oleninskoe deposit. Full article

(This article belongs to the Special Issue Mineralogy of Noble Metals and “Invisible” Speciations of These Elements in Natural Systems)

► Show Figures

Figure 1

18 pages, 9255 KiB

Open AccessArticle

Dewatering of Mine Tailings Slurries Using Superabsorbent Polymers (SAPs) Reclaimed from Industrial Reject of Baby Diapers: A Preliminary Study

by Amal Sahi, Khadija El Mahboub, Tikou Belem, Abdelkabir Maqsoud and Mamert Mbonimpa

Minerals 2019, 9(12), 785; https://doi.org/10.3390/min9120785 - 13 Dec 2019

Cited by 11 | Viewed by 5485

Abstract

Traditional deposition of tailings slurry in a tailings storage facility (TSF) can create risks of dike failure. In order to minimize these risks and slurry spillage, the surface deposition technique of densified tailings (DT) through dewatering of the slurry has emerged. The DT [...] Read more.

Traditional deposition of tailings slurry in a tailings storage facility (TSF) can create risks of dike failure. In order to minimize these risks and slurry spillage, the surface deposition technique of densified tailings (DT) through dewatering of the slurry has emerged. The DT technique has the potential to maximize water reuse, improve the shear strength of surface tailings, and reduce the ecological footprint of TSF. The consistency of DT covers a continuum ranging from thickened state, to paste state, to dry state. Despite its efficiency and economic feasibility, DT densification using thickeners sometimes proves unable to achieve the design target solids mass concentration (C_w%). Hence, the use of superabsorbent polymers (SAPs) seems to represent a promising alternative, owing to their higher water absorbent capacity. In this paper, superabsorbent polymers (SAPs) reclaimed from industrial reject of baby diapers (Na-polyacrylates) are explored as a promising alternative to mine tailings slurries dewatering. To this end, laboratory-scale dewatering tests have been performed using two grades of Na-polyacrylate SAPs (grade 1 SAP = SAG-A06P coarse-grained, and grade 2 = SAG-M01P-100 medium-grained) for the tailings slurries densification. A higher water absorbency (or swelling capacity) was observed using the coarser SAPs (SAG-A06P) compared to the finer SAPs (SAG-M01P-100). The preliminary results showed that a SAP volume dosage in the range 10–13 kg of SAP/m³ of slurry allowed achieving a final solids mass concentration (C_{w%_final}) ≥ 70%, despite the occurrence of gel-blocking phenomenon. Full article

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

► Show Figures

Figure 1

18 pages, 6596 KiB

Open AccessArticle

Effects of Ultrasound on Desliming Prior to Feldspar Flotation

by Ufuk Malayoglu and Safak Gokhan Ozkan

Minerals 2019, 9(12), 784; https://doi.org/10.3390/min9120784 - 13 Dec 2019

Cited by 11 | Viewed by 3860

Abstract

In this study, the effects of ultrasound on removal of impurities from raw feldspar were investigated by testing with a newly developed flotation cell with various frequency and power intensities prior to multistage feldspar flotation. Particularly, the quality of feldspar concentrates, the volume [...] Read more.

In this study, the effects of ultrasound on removal of impurities from raw feldspar were investigated by testing with a newly developed flotation cell with various frequency and power intensities prior to multistage feldspar flotation. Particularly, the quality of feldspar concentrates, the volume of removed slimes and the content of impurities were taken into account to reveal the impacts. Two representative feldspar ore samples taken from the Milas-Mugla region in Turkey were separately tested for desliming and flotation by conventional and ultrasonic methods under similar conditions and the results were compared to each other in terms of the quantity and the quality of the removed slimes and the final feldspar flotation concentrate. As a result, during desliming stage by using ultrasound, the volume of removed slimes was reduced by approximately 45% when compared to the conventional slime removal methods. Moreover, the impurity contents were doubled inside slimes when ultrasound was used. These outcomes lead to significant success in terms of reducing losses during the desliming stage and production of high quality feldspar concentrates by froth flotation assisted by ultrasound. Full article

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

► Show Figures

Figure 1

22 pages, 2885 KiB

Open AccessArticle

Risk Assessment of Contamination by Potentially Toxic Metals: A Case Study in the Vicinity of an Abandoned Pyrite Mine

by Tingting Ma, Wei Zhou, Xiao Yang, Peter Christie and Yongming Luo

Minerals 2019, 9(12), 783; https://doi.org/10.3390/min9120783 - 13 Dec 2019

Cited by 5 | Viewed by 2488

Abstract

Abandoned mining areas can display soil and water pollution and also a high incidence of endemic diseases. Here, based on preliminary results on mental retardation and high incidence rates of cancers, we investigate the contamination status and potential ecological risk at an abandoned [...] Read more.

Abandoned mining areas can display soil and water pollution and also a high incidence of endemic diseases. Here, based on preliminary results on mental retardation and high incidence rates of cancers, we investigate the contamination status and potential ecological risk at an abandoned pyrite mine located in Xianju village, Hubei province, central China. The study focused on the three potentially toxic metals As, Pb, and Zn and four other common elements, including Ca, Fe, S, and Se. Soil samples were collected from 12 sites and leachate seeping from five sites. Leachates were strongly acidic compared to the soil, with pH values <3.22. Soil As and Se concentrations exceeded the Chinese Grade II standards for soil environmental quality (GB 15618-2009) (30 and 3 mg·kg⁻¹, respectively), ranging from 33.6 ± 0.7 to 78.2 ± 1.0 mg As·kg⁻¹ dry matter (DM) and 5.3 ± 0.8 to 17.1 ± 1.4 mg Se·kg⁻¹ DM. Arsenic, Fe, Se, and S in leachates all exceeded the Chinese Grade III standard for surface water environmental quality (GB 3838-2002) (0.1, 0.3, 0.03, and 1.0 mg·L⁻¹). The potential ecological risks from Pb and Zn in soils were low, but As in soils and leachates represented a moderate or strong risk to children according to the Nemerow index and hazard quotient. Soil replacement combined with further remediation measures is required to remediate the contaminated area. Full article

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

► Show Figures

Figure 1

15 pages, 2236 KiB

Open AccessFeature PaperArticle

Surface Properties and Floatability Comparison of Aegirite and Specularite by Density Functional Theory Study and Experiment

by Mingyang Li, Jun Liu, Xiangpeng Gao, Yiming Hu, Xiong Tong, Fugang Zhao and Qidong Yuan

Minerals 2019, 9(12), 782; https://doi.org/10.3390/min9120782 - 13 Dec 2019

Cited by 14 | Viewed by 2413

Abstract

Understanding the differences in surface properties between aegirite and specularite is of great significance to study their separation. In this work, the surface properties of aegirite and specularite, as well as their relationships to floatability, have been explored by first principle calculation, flotation, [...] Read more.

Understanding the differences in surface properties between aegirite and specularite is of great significance to study their separation. In this work, the surface properties of aegirite and specularite, as well as their relationships to floatability, have been explored by first principle calculation, flotation, and Zeta potential measurement. The surface relaxation indicated that the specularite (001) surface appeared to show more surface reconstruction. The unsatisfied bond properties, Mulliken bond population, and surface charge showed that the floatability of specularite was superior to that of aegirite. The flotation results showed that the hydrophobicity of specularite was higher than that of aegirite with dodecylamine (DDA) as the collector. It is infeasible to separate specularite from aegirite by flotation using starch as the depressant, and research of effective reagents with high affinity to the element Si is the subclinical breakthrough point of specularite/aegirite separation. Full article

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

► Show Figures

Figure 1

10 pages, 4453 KiB

Open AccessArticle

(K,Na)₂[AsB₆O₁₂]₂[B₃O₃(OH)₃], a New Microporous Material, and Its Comparison to Teruggite

by Yulia A. Pankova and Sergey V. Krivovichev

Minerals 2019, 9(12), 781; https://doi.org/10.3390/min9120781 - 13 Dec 2019

Viewed by 2128

Abstract

Single crystals of the novel boroarsenate (K,Na)₂[As₂B₁₂O₂₄][B₃O₃(OH)₃] (I) were obtained using the borax flux method. The crystal structure of I was found to be triclinic, P-1, [...] Read more.

Single crystals of the novel boroarsenate (K,Na)₂[As₂B₁₂O₂₄][B₃O₃(OH)₃] (I) were obtained using the borax flux method. The crystal structure of I was found to be triclinic, P-1, a = 8.414(5), b = 10.173(6), c = 15.90(1) Å, α = 79.56(1), β = 78.68(1), γ = 70.91(1), V = 1251(1) Å³, Z = 2. The crystal structure of I is based upon the novel [AsB₆O₁₂]⁻ microporous boroarsenate framework formed by B and As coordination polyhedra. This framework can be subdivided into borate units that are interlinked by AsO₄ tetrahedra. In the case of I, the borate substructure is a chain consisting of triborate rings, ☐2Δ, formed by two (BO₃) triangles and one (BO₄) tetrahedron connected through shared common oxygen atoms. The chains are extended along [0

\bar{1}

1] and are interlinked by (AsO₄) tetrahedra in the [011] direction. As a result, the framework has large channels parallel to [100], having an effective diameter of 4.2 × 5.6 Å². The channels contain occluded electroneutral ring triborate complexes, [B₃O₃(OH)₃]⁰, formed by three (BO₂(OH⁻))⁻ triangles sharing common O atoms, as well as K⁺ and Na⁺ cations. The triborate [B₃O₃(OH)₃]⁰ units correspond to similar clusters found in the crystal structure of the α-form of metaboric acid, HBO₂. According to information-based complexity calculations, the crystal structure of I should be described as complex, with I_G = 5.781 bits/atom and I_G,total = 625.950 bits/cell. Teruggite, Ca₄Mg[B₆As(OH)₆O₁₁]₂(H₂O)₁₄, the only known boroarsenate of natural origin, has almost twice as much information per unit cell, with I_G,total = 1201.992 bits/cell. The observed difference in structural complexity between I and teruggite is the consequence of their chemistry (hydration state) and different formation conditions. Full article

(This article belongs to the Special Issue Selected Papers from the XIX International Meeting on Crystal Chemistry, X-ray Diffraction and Spectroscopy of Minerals)

► Show Figures

Figure 1

20 pages, 17658 KiB

Open AccessArticle

Metamorphic Age Comparison and Its Implications between the Zuoquan and Zanhuang Complexes in the Central North China Craton, Based on LA-ICP-MS Zircon U–Pb Dating

by Ling-Ling Xiao and Min-Hua Chen

Minerals 2019, 9(12), 780; https://doi.org/10.3390/min9120780 - 13 Dec 2019

Cited by 9 | Viewed by 2981

Abstract

The Trans-North China Orogen (TNCO) is well-known as an early Precambrian orogenic belt in the North China Craton (NCC). Three meaningful groups of metamorphic ages have been reported in the metamorphic complexes throughout the TNCO, including c. 1.85 Ga, c. 1.95 Ga, and [...] Read more.

The Trans-North China Orogen (TNCO) is well-known as an early Precambrian orogenic belt in the North China Craton (NCC). Three meaningful groups of metamorphic ages have been reported in the metamorphic complexes throughout the TNCO, including c. 1.85 Ga, c. 1.95 Ga, and c. 2.5 Ga. The spatial distributions and relationships of these ages provide notable insight into the formation timing and tectonic evolution of the NCC basement. The Zuoquan and Zanhuang complexes are exposed in the south–central TNCO and are adjacent to the Eastern Block. In order to place new constraints on the timing of two phases of metamorphism that occurred in the complexes, combined U–Pb and rare earth element analyses were performed on zircons from different types of metamorphic rocks. Uranium–Pb zircon dating in this study shows that two groups of metamorphic ages of 1.88–1.85 Ga and 2.48–2.46 Ga were commonly recorded by metamorphic rocks in the Zanhuang and Zuoquan complexes, respectively. Our previous geochronological studies showed that metamorphic ages of c. 2.51 Ga and c. 1.90 Ga were locally recorded in the Zanhuang and Zuoquan complexes, respectively. These data indicate that metamorphic rocks in the two complexes underwent at least two phases of metamorphism, i.e., 2.51–2.46 Ga (Phase I) and 1.90–1.85 Ga (Phase II). In combination with previous studies regarding reaction microstructures, metamorphic pressure–temperature paths, and geochronology, the Phase II metamorphic ages are interpreted to be linked to the collision between the Western and Eastern Blocks along the TNCO between 1.97 Ga and 1.80 Ga, whereas the Phase I metamorphic ages, as a result of an earlier and extensive tectono-thermal event that occurred in the Eastern and Western Blocks of the NCC, were related to underplating of mantle-derived magma. It is inferred that the rocks with c. 2.51–2.46 Ga metamorphic ages in the two complexes formed in the Eastern Block and underwent regional metamorphism during that period, and then were tectonically involved in the TNCO and experienced c. 1.90–1.85 Ga metamorphism. Metamorphic peaks occurred at different crustal levels in the orogen, resulting in distinct metamorphic ages and peak conditions preserved by metamorphic rocks in the two complexes. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

► Show Figures

Figure 1

11 pages, 5242 KiB

Open AccessArticle

Crystal-Chemistry of Sulfates from the Apuan Alps (Tuscany, Italy). VII. Magnanelliite, K₃Fe³⁺₂(SO₄)₄ (OH)(H₂O)₂, a New Sulfate from the Monte Arsiccio Mine

by Cristian Biagioni, Luca Bindi and Anthony R. Kampf

Minerals 2019, 9(12), 779; https://doi.org/10.3390/min9120779 - 12 Dec 2019

Cited by 8 | Viewed by 3739

Abstract

The new mineral species magnanelliite, K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as steeply terminated prisms, up to 0.5 mm in length, yellow [...] Read more.

The new mineral species magnanelliite, K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as steeply terminated prisms, up to 0.5 mm in length, yellow to orange-yellow in color, with a vitreous luster. Streak is pale yellow, Mohs hardness is ca. 3, and cleavage is good on {010}, fair on {100}. The measured density is 2.82(3) g/cm³. Magnanelliite is optically biaxial (+), with α = 1.628(2), β = 1.637(2), γ = 1.665(2) (white light), 2V_meas = 60(2)°, and 2V_calc = 59.9°. It exhibits a strong dispersion, r > v. The optical orientation is Y = b, X ^ c ~ 25° in the obtuse angle β. It is pleochroic, with X = orange yellow, Y and Z = yellow. Magnanelliite is associated with alum-(K), giacovazzoite, gypsum, jarosite, krausite, melanterite, and scordariite. Electron microprobe analyses give (wt.%): SO₃ 47.82, TiO₂ 0.05, Al₂O₃ 0.40, Fe₂O₃ 25.21, MgO 0.07, Na₂O 0.20, K₂O 21.35, H₂O_calc 6.85, total 101.95. On the basis of 19 anions per formula unit, assuming the occurrence of one (OH)⁻ and two H₂O groups, the empirical chemical formula of magnanelliite is (K_2.98Na_0.04)_Σ3.02(Fe³⁺_2.08Al_0.05Mg_0.01)_Σ2.14S_3.93O₁₆(OH)(H₂O)₂. The ideal end-member formula can be written as K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂. Magnanelliite is monoclinic, space group C2/c, with a = 7.5491(3), b = 16.8652(6), c = 12.1574(4) Å, β = 94.064(1)°, V = 1543.95(10) Å³, Z = 4. Strongest diffraction lines of the observed X-ray powder pattern are [d(in Å), estimated visual intensity, hkl]: 6.9, medium, 021 and 110; 4.91, medium-weak, 022; 3.612, medium-weak,

\bar{1}

32, 023, and

\bar{1}

13; 3.085, strong, 202, 150, and

\bar{1}

33; 3.006, medium, 004,

\bar{1}

51, and 151; 2.704, medium, 152 and

\bar{2}

23; 2.597, medium-weak,

\bar{2}

42; 2.410, medium-weak, 153. The crystal structure of magnanelliite has been refined using X-ray single-crystal data to a final R₁ = 0.025, on the basis of 2411 reflections with F_o > 4σ(F_o) and 144 refined parameters. The crystal structure is isotypic with that of alcaparrosaite, K₃Ti⁴⁺Fe³⁺(SO)₄O(H₂O)₂. Full article

(This article belongs to the Collection New Minerals)

► Show Figures

Figure 1

5 pages, 208 KiB

Open AccessEditorial

Editorial for Special Issue “Mineralogy and Geochemistry of Gems”

by Panagiotis Voudouris, Stefanos Karampelas, Vasilios Melfos and Ian Graham

Minerals 2019, 9(12), 778; https://doi.org/10.3390/min9120778 - 12 Dec 2019

Cited by 1 | Viewed by 2516

Abstract

Gems are materials used for adornment or decoration that must satisfy several criteria where they must be aesthetic and visually appealing; relatively rare; hard and tough enough to resist “normal” wear; and able to withstand corrosion by skin contact and cosmetics [...] Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)

29 pages, 6299 KiB

Open AccessArticle

Major and Trace Element Geochemistry of Dayakou Vanadium-Dominant Emerald from Malipo (Yunnan, China): Genetic Model and Geographic Origin Determination

by Yuyu Zheng, Xiaoyan Yu and Hongshu Guo

Minerals 2019, 9(12), 777; https://doi.org/10.3390/min9120777 - 12 Dec 2019

Cited by 15 | Viewed by 3957

Abstract

Emerald from the deposit at Dayakou is classified as a vanadium-dominant emerald together with Lened, Muzo, Mohmand, and Eidsvoll emeralds. Although previous studies defined these V-dominant emeralds and traced the genesis of the Dayakou deposit, there has not been any systematic comparison or [...] Read more.

Emerald from the deposit at Dayakou is classified as a vanadium-dominant emerald together with Lened, Muzo, Mohmand, and Eidsvoll emeralds. Although previous studies defined these V-dominant emeralds and traced the genesis of the Dayakou deposit, there has not been any systematic comparison or discrimination on V-dominant emeralds from these deposits. The origin of the parental fluid and the crystallization process of the Dayakou emerald remain controversial. In this study, both major and trace element signatures of 34 V-dominant samples from Dayakou are analyzed through electron microprobe analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Dayakou emeralds are characterized by high ratios of V/Cr and the enrichment of Li, Cs, W, Sn, and As. These geochemical fingerprints indicate a parental fluid of an Early Cretaceous early-stage granitic fluid associated with Laojunshan granite. The considerable concentration variation of Rb, Cs, Ga and the presence of V-rich oxy-schorl-dravite inclusions in a color zoned sample suggest two generations of emerald precipitation. Thus, a more detailed idealized mineralization model for the Dayakou deposit is proposed. A series of plots, such as Rb vs. Cs, V vs. V/Cr, LILE vs. CTE, and Li vs. Sc, are constructed to discriminate the provenance of V-dominant emeralds. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

► Show Figures

Graphical abstract

17 pages, 1195 KiB

Open AccessArticle

Implications of Sulfur Speciation on the Assessment of Acid Rock Drainage Generating Potential: A Study of South African Coal Processing Wastes

by Annah Moyo, Juarez R. do Amaral Filho, Susan T.L. Harrison and Jennifer L. Broadhurst

Minerals 2019, 9(12), 776; https://doi.org/10.3390/min9120776 - 12 Dec 2019

Cited by 11 | Viewed by 3847

Abstract

The presence of sulfur in coal processing wastes can lead to environmental impacts, such as acid rock drainage (ARD). However, not all sulfur species are acid-forming, and the implications of sulfur speciation when assessing acid rock drainage potential by means of static chemical [...] Read more.

The presence of sulfur in coal processing wastes can lead to environmental impacts, such as acid rock drainage (ARD). However, not all sulfur species are acid-forming, and the implications of sulfur speciation when assessing acid rock drainage potential by means of static chemical tests are not well understood. This study set out to evaluate the implications of different sulfur forms on the assessment of acid rock drainage potential using static laboratory-scale tests and to investigate the reliability of methods for the analysis of such forms for the case of three South African coal processing wastes. Both the International Organization for Standardization (ISO) 157:1996 and Australian Coal Association Research Program (ACARP) C15034 protocols were found to be suitable tools for analyzing the different forms of sulfur. Acid-generating sulfur forms constituted between 53% and 64% of the total sulfur in the wastes evaluated, with the maximum potential acidity (MPA) and net acid-producing potential (NAPP) values calculated on the basis of acid-forming sulfur being significantly lower than those calculated on the basis of total sulfur content. Results also showed that the partial conversion of sulfur species under the relatively aggressive conditions of the acid-neutralizing capacity (ANC) and net acid generation (NAG) tests may overestimate the potential acid generating potential in the case of coal. These findings highlight the uncertainties associated with standard ARD static tests and the importance of taking sulfur speciation into account when calculating the MPA for coal processing wastes. Full article

(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)

► Show Figures

Graphical abstract

22 pages, 14392 KiB

Open AccessArticle

New Insight into the Genetic Mechanism of Shear Zone Type Gold Deposits from Muping-Rushan Metallogenic Belt (Jiaodong Peninsula of Eastern China)

by Nannan Cheng, Quanlin Hou, Mengyan Shi, Miao He, Qing Liu, Fangchao Yan and Hongwei Liu

Minerals 2019, 9(12), 775; https://doi.org/10.3390/min9120775 - 12 Dec 2019

Cited by 8 | Viewed by 6920

Abstract

Most gold deposits are genetically controlled by shear zones, which are called shear zone type gold deposits (SZTGD). A better understanding of kinematics of shear zones and its constraint on the ore-forming process is critical to reveal the genetic mechanism of the SZTGD [...] Read more.

Most gold deposits are genetically controlled by shear zones, which are called shear zone type gold deposits (SZTGD). A better understanding of kinematics of shear zones and its constraint on the ore-forming process is critical to reveal the genetic mechanism of the SZTGD and favorable to mineral exploration. By conducting detailed structural analysis including field and microscopic observations and electron backscatter diffraction (EBSD) and fractal dimension analysis in the Muping-Rushan shear zone (MR) as well as several gold deposits, the kinematic characteristics of the MR are well recognized and the metallogenic process of the SZTGD are discussed. The main conclusions are as follows: (1) petrology, geometry, kinematics, macro- and micro-structures imply that the MR has experienced a progressive shearing history exhumed via middle crust to subsurface level under the NW-SE extensional regime from late Jurassic to early Cretaceous; (2) in the MR, gold may precipitate both in the brittle fractures at middle crust level and brittle deformation part at shallow crust level during the stress-chemical process and (3) comparison of gold deposits between the MR and other areas show that the SZTGD has a uniform metallogenic mechanism, which is from (multi-stage) pluton emplacement, hydrothermal fluid action, shearing action, brittle fracturing, sudden reduction of fluid pressure, flash vaporization to (gold) mineralization. Full article

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

► Show Figures

Graphical abstract

16 pages, 3123 KiB

Open AccessArticle

Further Characterization of the BB Zircon via SIMS and MC-ICP-MS for Li, O, and Hf Isotopic Compositions

by Chao Huang, Hao Wang, Jin-Hui Yang, Lie-Wen Xie, Yue-Heng Yang and Shi-Tou Wu

Minerals 2019, 9(12), 774; https://doi.org/10.3390/min9120774 - 11 Dec 2019

Cited by 2 | Viewed by 2677

Abstract

In this contribution, we report the results for the characterization of the BB zircon, a newly developed zircon reference material from Sri Lanka, via secondary ion mass spectrometry (SIMS) and multiple-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The focus of this work was to [...] Read more.

In this contribution, we report the results for the characterization of the BB zircon, a newly developed zircon reference material from Sri Lanka, via secondary ion mass spectrometry (SIMS) and multiple-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The focus of this work was to further investigate the applicability of the BB zircon as a reference material for micro-beam analysis, including Li, O, and Hf isotopes. The SIMS analyses reveal that BB zircon is characterized by significant localized variations in Li concentration and isotopic ratio, which makes it unsuitable as a lithium isotope reference material. The SIMS-determined δ¹⁸O values are 13.81‰ ± 0.39‰ (2SD, BB16) and 13.61‰ ± 0.40‰ (2SD, BB40), which, combined with previous studies, indicates that there is no evidence of conspicuous O isotope heterogeneity within individual BB zircon megacrysts. The mean ¹⁷⁶Hf/¹⁷⁷Hf ratio of BB16 determined by solution MC-ICP-MS is 0.281669 ± 0.000012 (2SD, n = 29) indistinguishable from results achieved by laser ablation (LA)-MC-ICP-MS. Based on the SIMS and MC-ICP-MS data, BB zircon is proposed as a reference material for the O isotope and Hf isotope determination. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

► Show Figures

Figure 1

16 pages, 4535 KiB

Open AccessArticle

Geology and Geochronology of the Maozaishan Sn Deposit, Hunan Province: Constraints from Zircon U–Pb and Muscovite Ar–Ar Dating

by Jian Guo, Youyue Lu, Jianming Fu, Zhengwei Qin, Yongyun Ning and Zunzun Zhang

Minerals 2019, 9(12), 773; https://doi.org/10.3390/min9120773 - 11 Dec 2019

Cited by 7 | Viewed by 2833

Abstract

The Maozaishan Sn deposit, located south of the Dayishan ore field in the Nanling Range, is a newly explored greisen-type Sn deposit. Two muscovite samples from tin-bearing ores yielded ⁴⁰Ar/³⁹Ar plateau ages of 154.7 ± 1.1 Ma (Mean standard weighted [...] Read more.

The Maozaishan Sn deposit, located south of the Dayishan ore field in the Nanling Range, is a newly explored greisen-type Sn deposit. Two muscovite samples from tin-bearing ores yielded ⁴⁰Ar/³⁹Ar plateau ages of 154.7 ± 1.1 Ma (Mean standard weighted deviation (MSWD) = 0.48) and 152.6 ± 0.7 Ma (MSWD = 0.25), respectively. Zircon U–Pb dating result of fine-grained biotite monzogranite in the Maozaishan mining area shows that these zircon grains can be subdivided into two populations, with ages of 154.2 ± 2.0 Ma (MSWD = 0.51) and 159.6 ± 1.9 Ma (MSWD = 0.09), respectively, indicating that the monzogranite is formed by a multi-stage magmatic event. It is indicated that formation of the Maozaishan Sn deposit is closely related to the Middle Jurassic granitic magmatism. Based on the trace element compositions of zircon grains, the calculated magma temperatures and oxygen fugacity (log(fO₂)) values range from 638 °C to 754 °C (mean = 704 °C) and from −18.9 to −15.8 (mean = −17.1), respectively. In addition, these intrusive rocks in the Dayishan ore field belong to highly fractionated granites and are characterized by low oxygen fugacity and crust–mantle origin, which are consistent to these tin-bearing granites in the Nanling Range and in favor of the Sn mineralization. Full article

(This article belongs to the Special Issue Integrated Chronology Studies of Ore Deposits)

► Show Figures

Figure 1

15 pages, 5357 KiB

Open AccessArticle

Geochemical Study of Weathered Coal, a Co-Substrate for Bioremediation of South African Coal Discard Dumps

by Yvonne van Breugel, Ashton Keith Cowan and Harilaos Tsikos

Minerals 2019, 9(12), 772; https://doi.org/10.3390/min9120772 - 11 Dec 2019

Cited by 2 | Viewed by 5392

Abstract

Coal mining creates large volumes of waste in the form of discard coal that is stockpiled. In South Africa, rehabilitation of coal discard dumps remains a challenge due to reliance on topsoil for establishment of vegetation. Exploitation of fungal bio liquefaction/degradation of coal [...] Read more.

Coal mining creates large volumes of waste in the form of discard coal that is stockpiled. In South Africa, rehabilitation of coal discard dumps remains a challenge due to reliance on topsoil for establishment of vegetation. Exploitation of fungal bio liquefaction/degradation of coal resulted in the emergence of Fungcoal as a bioprocess for the rehabilitation of coal discard dumps and opencast spoils. In this process, a suite of fungi is used to bio liquefy/degrade recalcitrant waste coal to form a soil-like material which promotes reinvigoration of the microbial component, grass growth, and re-vegetation. Here, the role of outcrop weathered coal as a mineral/carbon source to ensure biologically induced humic acid-like substance enrichment of discard and spoil to increase efficacy of fungi-plant mutualism and stimulate revegetation without the need for topsoil was investigated. Mineralogical, elemental, and pyrolysis gas chromatography-mass spectroscopic analyses show that outcrop weathered coal has decreased volatile material and increased humics, ash, and mineral bound water in comparison to bituminous coal. These changes occur coincidently with decreased C, N, and H contents, and a substantial increase in O concentration. No apparent stoichiometric relationship between sulphur and iron oxide content of weathered coal could be discerned suggesting little residual pyrite in this material and a dominance of oxy-hydroxides of Fe. Organic analysis showed weathered coal to be enriched in C-16 and C-18 fatty acids and the presence of the indicator, 17α(H),21β(H)-homohopane but not the β,β-stereoisomer, was interpreted to indicate that bacteria may only have been active prior to transformation of hard coal into weathered coal. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

► Show Figures

Figure 1

19 pages, 5666 KiB

Open AccessArticle

Early Jurassic Mafic Intrusions in the Southern Youjiang Basin, SW China: Petrogenesis, Tectonic and Metallogenic Implications

by Wen Jiang, Quanren Yan, Li Deng, Bin Zhou, Zhongjin Xiang and Wenjing Xia

Minerals 2019, 9(12), 771; https://doi.org/10.3390/min9120771 - 11 Dec 2019

Cited by 5 | Viewed by 4669

Abstract

A suite of mafic intrusions, composed of diabase and micro-gabbro outcrops in the Jingxi area of southern Youjiang Basin, SW China. This study conducts geochronological, geochemical, and Sr–Nd isotopic analyses on the mafic intrusions in Jingxi with the aim of determining their petrogenesis, [...] Read more.

A suite of mafic intrusions, composed of diabase and micro-gabbro outcrops in the Jingxi area of southern Youjiang Basin, SW China. This study conducts geochronological, geochemical, and Sr–Nd isotopic analyses on the mafic intrusions in Jingxi with the aim of determining their petrogenesis, tectonic setting, and metallogenic implications. Zircon U–Pb dating for the mafic intrusions yielded an age of 183 ± 3 Ma (MSWD = 2.3), which is coeval with the Carlin-like gold mineralization in the Youjiang Basin. The mafic intrusions are alkaline in composition and characterized by low TiO₂ (1.25–1.87 wt %) contents and low Ti/Y ratios (410–550). They exhibit OIB-like patterns of trace element distribution and they have low (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.704341 to 0.705677, slightly negative ε_Nd(t) values of −0.30 to −2.16, low La/Ta (11.57–15.66) and La/Nb (0.77–1.06) ratios, with [La/Yb]_N = 6.52–10.63. The geochemical characteristics, combined with regional considerations, suggest that the mafic intrusions originated from partial melting of upwelling asthenosphere within the garnet-spinel transition zone, as a result of intracontinental back-arc extension triggered by the steep subduction of the Paleo-Pacific plate beneath the South China Block. Moreover, the new data not only suggest Early Jurassic magma was a possible heat source, but also support a magmatism-related model for the Carlin-like gold mineralization in the Youjiang Basin. Full article

(This article belongs to the Special Issue Role of Magmatic Activity in Generation of Ore Deposits)

► Show Figures

Graphical abstract

17 pages, 4035 KiB

Open AccessFeature PaperArticle

A New Mineral Ferrisanidine, K[Fe³⁺Si₃O₈], the First Natural Feldspar with Species-Defining Iron

by Nadezhda V. Shchipalkina, Igor V. Pekov, Sergey N. Britvin, Natalia N. Koshlyakova, Marina F. Vigasina and Evgeny G. Sidorov

Minerals 2019, 9(12), 770; https://doi.org/10.3390/min9120770 - 11 Dec 2019

Cited by 8 | Viewed by 5258

Abstract

Ferrisanidine, K[Fe³⁺Si₃O₈], the first natural feldspar with species-defining iron, is an analogue of sanidine bearing Fe³⁺ instead of Al. It was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the [...] Read more.

Ferrisanidine, K[Fe³⁺Si₃O₈], the first natural feldspar with species-defining iron, is an analogue of sanidine bearing Fe³⁺ instead of Al. It was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Fissure Tolbachik Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. The associated minerals are aegirine, cassiterite, hematite, sylvite, halite, johillerite, arsmirandite, axelite, aphthitalite. Ferrisanidine forms porous crusts composed by cavernous short prismatic crystals or irregular grains up to 10 μm × 20 μm. Ferrisanidine is transparent, colorless to white, the lustre is vitreous. D_calc is 2.722 g·cm⁻³. The chemical composition of ferrisanidine (wt. %, electron microprobe) is: Na₂O 0.25, K₂O 15.15, Al₂O₃ 0.27, Fe₂O₃ 24.92, SiO₂ 60.50, in total 101.09. The empirical formula calculated based on 8 O apfu is (K_0.97Na_0.03)_Ʃ1.00(Si_3.03Fe³⁺_0.94Al_0.02)_Ʃ3.99O₈. The crystal structure of ferrisanidine was studied using the Rietveld method, the final R indices are: R_p = 0.0053, R_wp = 0.0075, R₁ = 0.0536. Parameters of the monoclinic unit cell are: a = 8.678(4), b = 13.144(8), c = 7.337(5) Å, β = 116.39(8)°, V = 749.6(9) Å³. Space group is C2/m. The crystal structure of ferrisanidine is based on the sanidine-type “ferrisilicate” framework formed by disordered [SiO₄] and [Fe³⁺O₄] tetrahedra. Full article

(This article belongs to the Collection New Minerals)

► Show Figures

Figure 1

29 pages, 7707 KiB

Open AccessArticle

The Chemical Evolution from Older (323–318 Ma) towards Younger Highly Evolved Tin Granites (315–314 Ma)—Sources and Metal Enrichment in Variscan Granites of the Western Erzgebirge (Central European Variscides, Germany)

by Marion Tichomirowa, Axel Gerdes, Manuel Lapp, Dietmar Leonhardt and Martin Whitehouse

Minerals 2019, 9(12), 769; https://doi.org/10.3390/min9120769 - 11 Dec 2019

Cited by 12 | Viewed by 3059

Abstract

The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk [...] Read more.

The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk rocks and autocrystic zircons and relate this information to their intrusion ages. The source rocks of the Variscan granites were identified as high-grade metamorphic rocks based on the comparison of Hf-O isotope data on zircons, the abundance of xenocrystic zircon ages as well as Nd and Hf model ages. Among these rocks, restite is the most likely candidate for later Variscan melts. Based on the evolution with time, we could reconstruct enrichment factors for tin and tungsten starting from the protoliths (575 Ma) that were later converted to high-grade metamorphic rocks (340 Ma) and served as sources for the older biotite granites (323–318 Ma) and the tin granites (315–314 Ma). This evolution involved a continuous enrichment of both tin and tungsten with an enrichment factor of ~15 for tin and ~7 for tungsten compared to the upper continental crust (UCC). Ore level concentrations (>10–100 times enrichment) were achieved only in the greisen bodies and dykes by subsequent hydrothermal processes. Full article

(This article belongs to the Special Issue Feature Papers in Mineral Geochemistry and Geochronology 2019)

► Show Figures

Figure 1

21 pages, 6659 KiB

Open AccessArticle

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

by Edgar Berrezueta, José Cuervas-Mons, Ángel Rodríguez-Rey and Berta Ordóñez-Casado

Minerals 2019, 9(12), 768; https://doi.org/10.3390/min9120768 - 11 Dec 2019

Cited by 35 | Viewed by 4613

Abstract

This paper introduces an assessment of the representation of shape parameter measurements on theoretical particles. The aim of the study was to establish a numerical method for estimating sphericity, roundness, and roughness on artificially designed particles and to evaluate their interdependence. The parameters [...] Read more.

This paper introduces an assessment of the representation of shape parameter measurements on theoretical particles. The aim of the study was to establish a numerical method for estimating sphericity, roundness, and roughness on artificially designed particles and to evaluate their interdependence. The parameters studied included a fractal dimension (FD), solidity (So), Wadell’s roundness (Rw), a perimeter-area normalized ratio (¥), and sphericity (S). The methods of the work included: (a) the design of theoretical particles with different shapes, (b) the definition of optimal analysis conditions for automated measurements, (c) the quantification of particle parameters by computer vision-based image processing, and (d) the evaluation of interdependence between the parameters. The study established the minimum sizes required for analysis of the particle shape. These varied depending on the method used (150 pixels or 50 pixels). Evaluating the relationships between the parameters showed that FD and So are independent of S. Nevertheless, Rw and ¥ are clearly dependent on S and, thus, must be numerically corrected to Rwc and ¥c. FD, So, Rwc, and ¥c were used to establish, mathematically, a new regularity parameter (RBC) that reflects the degree of roundness of a particle. The process was applied to a case study and the evaluation of all parameters corroborated previous petrographic characterizations. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

► Show Figures

Graphical abstract

20 pages, 6350 KiB

Open AccessArticle

Geochemical Features and Geological Processes Timescale of the Achaean TTG Complexes of the Ingozero Massif and the Pechenga Frame (NE Baltic Shield)

by Elena Nitkina, Nikolay Kozlov, Natalia Kozlova and Tatiana Kaulina

Minerals 2019, 9(12), 767; https://doi.org/10.3390/min9120767 - 10 Dec 2019

Cited by 1 | Viewed by 2281

Abstract

This article provides a geological review and results of the structural, metamorphic, and geochronological studies of the Pechenga frame outcrops located in the NW part of the Central-Kola terrain and the Ingozero massif outcrops situated in the northeastern part of the Belomorian mobile [...] Read more.

This article provides a geological review and results of the structural, metamorphic, and geochronological studies of the Pechenga frame outcrops located in the NW part of the Central-Kola terrain and the Ingozero massif outcrops situated in the northeastern part of the Belomorian mobile belt of the Kola Region (NW Baltic Shield). As a result of the work, the deformation scales and ages of the geological processes at the Neo-Archaean–Paleoproterozoic stage of the area’s development were compiled, and the reference rocks were dated. The petrochemical and geochemical characteristics of the Ingozero rocks are similar to those of tonalite–trondhjemite–granodiorite (TTG) complexes established on other Archaean shields. The isotope U–Pb dating of individual zircon grains from the biotite gneisses provided the oldest age for magmatic protolith of the Ingozero gneisses, which is 3149 ± 46 Ma. Sm–Nd model ages showed that the gneisses protolite initial melt formed at 3.1–2.8 Ga. Ages of metamorphic processes were determined by using isotope U–Pb dating ID TIMS (isotope dilution thermal ionization mass spectrometry): Biotite gneisses—2697 ± 9 Ma; amphibole–biotite gneisses—2725 ± 2 Ma and 2667 ± 7 Ma; and biotite–amphibole gneisses 2727 ± 5 Ma. Ages of granitoids, which cut the deformed gneisses, are 2615 ± 8 Ma and 2549 ± 31 Ma for plagiogranites and pegmatoid veins in gneisses, respectively. The following age sequence of geological processes was established by using U–Pb zircon dating: 2.8 Ga—The time of the garnet–biotite gneiss metamorphism; 2722 ± 9 Ma—The granodiorite crystallization time; 2636 ± 41 Ma—The aplite emplacement age and 2620 ± 16 Ma—The age of pegmatites origin, which marked final stages of the Archaean evolution; 2587 ± 5 Ma—The age of gabbros emplacement and 2507 ± 7 Ma—The age of gabbros metamorphism; 2522–2503 Ma—The origin time of the iron quartzite interpreted as the age of gabbros and biotite gneiss metamorphism. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

► Show Figures

Figure 1

21 pages, 5795 KiB

Open AccessArticle

Lithium Occurrences in Brines from Two German Salt Deposits (Upper Permian) and First Results of Leaching Experiments

by Michael Mertineit and Michael Schramm

Minerals 2019, 9(12), 766; https://doi.org/10.3390/min9120766 - 10 Dec 2019

Cited by 6 | Viewed by 7094

Abstract

Lithium occurrences were detected in Upper Permian (Zechstein) salt rocks and saline solutions of the Gorleben and Morsleben salt structures, northern Germany. The brine occurrences were mainly connected to anhydrite rock-bearing formations and to lithological boundaries. Most of these brines display a high [...] Read more.

Lithium occurrences were detected in Upper Permian (Zechstein) salt rocks and saline solutions of the Gorleben and Morsleben salt structures, northern Germany. The brine occurrences were mainly connected to anhydrite rock-bearing formations and to lithological boundaries. Most of these brines display a high Mg content and were accordingly interpreted as intrasalinar solutions, which developed during sedimentation, diagenesis, and the subsequent rock–fluid interaction. These Mg-rich brines frequently show high Li concentrations. One of the assumptions made, is that Li was leached from phyllosilicates, since no natural Li-bearing salt minerals are known to date. To improve the understanding of the origin of Li in the brines, leaching experiments were performed on the Li-bearing phyllosilicate Lepidolite. Lepidolite with a Li content of 2.42 wt. % served as an analogue material, which was exposed to 18 saline solutions of different composition for a period of three years. The most pronounced leaching effect (53.36 µg Li/g in the brine) was observed during the interaction with a 0.03 mol/kg H₂O MgCl₂ solution, the second most pronounced by modern seawater interaction. The experiments show that the amount of Li leached from the lepidolite is dependent on brine composition. Full article

(This article belongs to the Special Issue Evolution of Li-rich Brines)

► Show Figures

Figure 1

22 pages, 5784 KiB

Open AccessCommunication

Recognition of Late Triassic Cu-Mo Mineralization in the Northern Yidun Arc (S.E. Tibetan Plateau): Implications for Regional Exploration

by Zhen-Dong Tian, Cheng-Biao Leng, Xing-Chun Zhang, Li-Min Zhou and Yan-Wen Tang

Minerals 2019, 9(12), 765; https://doi.org/10.3390/min9120765 - 10 Dec 2019

Cited by 6 | Viewed by 2542

Abstract

The Yidun arc, located in the southeastern Tibetan Plateau, was formed by the westward subduction of the Ganze-Litang Paleo-Tethys ocean in Late Triassic. It is well-known for the formation of numerous Mesozoic porphyry-skarn Cu-Mo-(Au) deposits in the arc. To date, more than 20 [...] Read more.

The Yidun arc, located in the southeastern Tibetan Plateau, was formed by the westward subduction of the Ganze-Litang Paleo-Tethys ocean in Late Triassic. It is well-known for the formation of numerous Mesozoic porphyry-skarn Cu-Mo-(Au) deposits in the arc. To date, more than 20 Cu-Mo-(Au) deposits (>10 million tonnes Cu resources) have been discovered in the southern Eastern Yidun arc. However, few Cu-Mo deposits have been discovered in the northern Eastern Yidun arc. In recent years, some Cu-Mo deposits or occurrence are successively discovered in the northern Eastern Yidun arc, but their ore-forming ages are not well constrained. It remains unclear whether such Cu-Mo mineralization formed by similar metallogenic event and geodynamic setting as the Cu-Mo-(Au) mineralization in the south. In order to determine the metallogenic age and shed light on potential links between Cu-Mo mineralization and regional magmatic events, we present molybdenite Re-Os and zircon U-Pb ages to constrain the timing of two types of Cu-Mo mineralization in the northern Eastern Yidun arc (type I and type II). Molybdenite ICP-MS Re-Os dating results show that type I mineralization was formed at 217.7 ± 3.6 Ma, which is highly consistent with the formation ages of the host granite (218.1 ± 1.5 Ma, 2σ, n = 15, MSWD = 0.92) and aplite dyke (217.3 ± 1.3 Ma, 2σ, n = 16, MSWD = 0.50) within error. While the type II mineralization has a relatively younger formation age of 211.8 ± 4.7 Ma than the host granite (217.1 ± 1.5 Ma, 2σ, n = 14, MSWD = 0.96) and type I Cu-Mo mineralization. These data indicate that the Cu-Mo mineralization in the northern Eastern Yidun arc was temporally and spatially related to the Late Triassic magmatism in the region. Rhenium (Re) concentrations in the molybdenite from type I mineralization, ranging from 12.77 to 111.1 ppm (typically > 100 ppm), indicate that the ore-forming metals were derived mainly from a mantle source. However, Re contents in molybdenite from the type II mineralization, ranging from 7.983 to 10.40 ppm, indicate that the ore-forming metals were derived from a mixed mantle and crustal source with a predominantly crustal component. This study confirms that the northern Eastern Yidun arc exists Late Triassic Cu-Mo metallogenesis, and thus much attention should be paid on this region to find more Late Triassic Cu-Mo resources. Full article

(This article belongs to the Special Issue Integrated Chronology Studies of Ore Deposits)

► Show Figures

Graphical abstract

23 pages, 4647 KiB

Open AccessReview

Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia

by Nikolay Yu. Groshev, Tatyana V. Rundkvist, Bartosz T. Karykowski, Wolfgang D. Maier, Aleksey U. Korchagin, Anton N. Ivanov and Malte Junge

Minerals 2019, 9(12), 764; https://doi.org/10.3390/min9120764 - 10 Dec 2019

Cited by 13 | Viewed by 5873

Abstract

Several deposits of low-sulfide Pt–Pd ores have been discovered in recent decades in the Paleoproterozoic Fedorova–Pana Layered Complex located in the Kola Region (Murmansk Oblast) of Russia. The deposits are divided into two types: reef-style, associated with the layered central portions of intrusions, [...] Read more.

Several deposits of low-sulfide Pt–Pd ores have been discovered in recent decades in the Paleoproterozoic Fedorova–Pana Layered Complex located in the Kola Region (Murmansk Oblast) of Russia. The deposits are divided into two types: reef-style, associated with the layered central portions of intrusions, and contact-style, localized in the lower parts of intrusions near the contact with the Archean basement. The Kievey and the North Kamennik deposits represent the first ore type and are confined to the North PGE Reef located 600–800 m above the base of the West Pana Intrusion. The reef is associated with a horizon of cyclically interlayered orthopyroxenite, gabbronorite and anorthosite. The average contents of Au, Pt and Pd in the Kievey ore are 0.15, 0.53 and 3.32 ppm, respectively. The North Kamennik deposit has similar contents of noble metals. The Fedorova Tundra deposit belongs to the second ore type and has been explored in two sites in the lower part of the Fedorova intrusion. Mineralization is mainly associated mainly with taxitic or varied-textured gabbronorites, forming a matrix of intrusive breccia with fragments of barren orthopyroxenite. The ores contain an average of 0.08 ppm Au, 0.29 ppm Pt and 1.20 ppm Pd. In terms of PGE resources, the Fedorova Tundra is the largest deposit in Europe, hosting more than 300 tons of noble metals. Full article

(This article belongs to the Special Issue Mineral Deposits Related to Mantle Rocks)

► Show Figures

Figure 1

19 pages, 10842 KiB

Open AccessFeature PaperArticle

Mg-Rich Authigenic Carbonates in Coastal Facies of the Vtoroe Zasechnoe Lake (Southwest Siberia): First Assessment and Possible Mechanisms of Formation

by Andrey A. Novoselov, Alexandr O. Konstantinov, Artem G. Lim, Katja E. Goetschl, Sergey V. Loiko, Vasileios Mavromatis and Oleg S. Pokrovsky

Minerals 2019, 9(12), 763; https://doi.org/10.3390/min9120763 - 09 Dec 2019

Cited by 3 | Viewed by 3137

Abstract

The formation of Mg-rich carbonates in continental lakes throughout the world is highly relevant to irreversible CO₂ sequestration and the reconstruction of paleo-sedimentary environments. Here, preliminary results on Mg-rich carbonate formation at the coastal zone of Lake Vtoroe Zasechnoe, representing the Setovskiye [...] Read more.

The formation of Mg-rich carbonates in continental lakes throughout the world is highly relevant to irreversible CO₂ sequestration and the reconstruction of paleo-sedimentary environments. Here, preliminary results on Mg-rich carbonate formation at the coastal zone of Lake Vtoroe Zasechnoe, representing the Setovskiye group of water bodies located in the forest-steppe zone of Southwest Western Siberia, are reported. The Setovskiye lakes are Cl⁻–Na⁺–(SO₄²⁻) type, alkaline, and medium or highly saline. The results of microscopic and mineralogical studies of microbialites from shallow coastal waters of Lake Vtoroe Zasechnoe demonstrated that Mg in the studied lake was precipitated in the form of hydrous Mg carbonates, which occur as radially divergent crystals that form clusters in a dumbbell or star shape. It is possible that hydrous Mg carbonate forms due to the mineralization of exopolymeric substances (EPS) around bacterial cells within the algal mats. Therefore, the Vtoroe Zasechnoe Lake represents a rare case of Mg-carbonates formation under contemporary lacustrine conditions. Further research on this, as well as other lakes of Setovskiye group, is needed for a better understanding of the possible role of biomineralization and abiotic mechanisms, such as winter freezing and solute concentration, in the formation of authigenic Mg carbonate in modern aquatic environments. Full article

(This article belongs to the Special Issue Microorganisms–Minerals Interactions in Aquatic Environments)

► Show Figures

Figure 1

12 pages, 842 KiB

Open AccessArticle

Evaluating the Role of Iron-Rich (Mg,Fe)O in Ultralow Velocity Zones

by Vasilije V. Dobrosavljevic, Wolfgang Sturhahn and Jennifer M. Jackson

Minerals 2019, 9(12), 762; https://doi.org/10.3390/min9120762 - 08 Dec 2019

Cited by 9 | Viewed by 2695

Abstract

The composition of ultralow velocity zones (ULVZs) remains an open question, despite advances in both seismology and experimental work. We investigate the hypothesis of iron-rich (Mg,Fe)O (magnesiowüstite) as a cause of ULVZ seismic signatures. We report new quasi-hydrostatic X-ray diffraction measurements to constrain [...] Read more.

The composition of ultralow velocity zones (ULVZs) remains an open question, despite advances in both seismology and experimental work. We investigate the hypothesis of iron-rich (Mg,Fe)O (magnesiowüstite) as a cause of ULVZ seismic signatures. We report new quasi-hydrostatic X-ray diffraction measurements to constrain the equation of state of (Mg_0.06Fe_0.94)O with fit parameters V₀ = 9.860 ± 0.007 Å³, K_0T = 155.3 ± 2.2 GPa, K’_0T = 3.79 ± 0.11, as well as synchrotron Mössbauer spectroscopy measurements to characterize the high-pressure magnetic and spin state of magnesiowüstite. We combine these results with information from previous studies to calculate the elastic behavior at core–mantle boundary conditions of magnesiowüstite, as well as coexisting bridgmanite and calcium silicate perovskite. Forward models of aggregate elastic properties are computed, and from these, we construct an inverse model to determine the proportions of magnesiowüstite that best reproduce ULVZ observations within estimated mutual uncertainties. We find that the presence of magnesiowüstite can explain ULVZ observations exhibiting 1:2 V_P:V_S reduction ratios relative to the Preliminary Reference Earth Model (PREM), as well as certain 1:3 V_P:V_S reductions within estimated uncertainty bounds. Our work quantifies the viability of compositionally distinct ULVZs containing magnesiowüstite and contributes to developing a framework for a methodical approach to evaluating ULVZ hypotheses. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Minerals, Volume 9, Issue 12 (December 2019) – 75 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI