Minerals

22 pages, 6934 KiB

Open AccessArticle

Multi-Scale Measurements of Neolithic Ceramics—A Methodological Comparison of Portable Energy-Dispersive XRF, Wavelength-Dispersive XRF, and Microcomputer Tomography

by Julia Menne, Astrid Holzheid and Christopher Heilmann

Minerals 2020, 10(10), 931; https://doi.org/10.3390/min10100931 - 21 Oct 2020

Cited by 7 | Viewed by 2507

Abstract

Archaeometric investigation of ancient pottery with regard to their material composites allows insights into the material structures, production techniques and manufacturing processes. The applied methods depend on the classification of the pottery: some finds should remain unchanged for conservation reasons, other finds are [...] Read more.

Archaeometric investigation of ancient pottery with regard to their material composites allows insights into the material structures, production techniques and manufacturing processes. The applied methods depend on the classification of the pottery: some finds should remain unchanged for conservation reasons, other finds are less valuable or more common. While the first group cannot be destroyed for material analyses and the choice of analytical methods is limited, the latter can be investigated using destructive methods and thus can widen the spectrum of possible devices. Multi-element analyses of portable energy-dispersive X-ray fluorescence spectrometry (portable XRF) have become important for archaeological research, as portable XRF provides a quick overview about the chemical composition of potteries and can be used in non-destructive as well as destructive ways in addition to conventional microscopic examination and petrographic thin sections. While most portable XRF analyses of solely fracture surfaces do not provide satisfying results, portable XRF analyses on pulverized samples are a cost-efficient and fast alternative to wavelength-dispersive XRF (WD-XRF). In comparison to WD-XRF, portable XRF on pulverized samples provides reliable concentration data (K, Fe, Rb, Ti, V, Y, Zn, Zr), but other elements need to be corrected. X-ray microtomography (µCT) has proven to be a non-destructive technique to derive not only the porosity of ancient pottery but also to characterize temper components and non-plastic inclusions. Hence, the µCT technique has the potential to extract valuable information needed by archaeologists, for example, to deduce details about manufacturing. Full article

(This article belongs to the Special Issue Geochemical, Mineralogical, and Petrographical Applications to Environment and Cultural Heritage)

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12 pages, 6025 KiB

Open AccessArticle

The Influence of Fly Ash on Mechanical Properties of Clay-Based Ceramics

by Tomáš Húlan, Igor Štubňa, Ján Ondruška and Anton Trník

Minerals 2020, 10(10), 930; https://doi.org/10.3390/min10100930 - 21 Oct 2020

Cited by 13 | Viewed by 2952

Abstract

Elastic properties of mixtures of illitic clay, thermal power plant fly ash (fluidized fly ash—FFA and pulverized fly ash—PFA), and grog were investigated during the heating and cooling stages of the firing. The grog part in the mixtures was replaced with 10, 20, [...] Read more.

Elastic properties of mixtures of illitic clay, thermal power plant fly ash (fluidized fly ash—FFA and pulverized fly ash—PFA), and grog were investigated during the heating and cooling stages of the firing. The grog part in the mixtures was replaced with 10, 20, 30, and 40 mass% of the fly ash, respectively. The temperature dependence of Young’s modulus was derived using the dynamical thermomechanical analysis, in which dimensions and mass determined from thermogravimeric and thermodilatometric results were used. Flexural strength was measured at the room temperature using the three-point bending test. The following results were obtained: (1) Bulk density showed a decreasing trend up to 900 °C and a steep increase above 900 °C. During cooling, the bulk density slightly increased down to the room temperature. (2) Young’s modulus increased significantly during heating up to ~300 °C. Dehydroxylation was almost not reflected in Young’s modulus. At temperatures higher than 800 °C, Young’s modulus began to increase due to sintering. (3) During cooling, down to the glass transformation, Young’s modulus slightly increased and then began to slightly decrease due to microcracking between phases with different thermal expansion coefficients. (4) Around the β→α quartz transition, radial stresses on the quartz grain altered from compressive to tensile, creating microcracks. Below 560 °C, the radial stress remained tensile, and consequently, the microcracking around the quartz grains and a decreasing Young’s modulus continued. (5) With a lower amount of PFA and FFA, a higher Young’s modulus was reached after sintering. The final values of Young’s modulus, measured after firing, show a decreasing trend and depend linearly on the part of fly ash. (6) The flexural strength measured after firing decreased linearly with the amount of the fly ash for both mixtures. Full article

(This article belongs to the Special Issue Clay Minerals and Waste Fly Ash Ceramics)

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31 pages, 14948 KiB

Open AccessArticle

Sedimentology, Provenance and Radiometric Dating of the Silante Formation: Implications for the Cenozoic Evolution of the Western Andes of Ecuador

by Cristian Vallejo, Santiago Almagor, Christian Romero, Jose L. Herrera, Vanessa Escobar, Richard A. Spikings, Wilfried Winkler and Pieter Vermeesch

Minerals 2020, 10(10), 929; https://doi.org/10.3390/min10100929 - 21 Oct 2020

Cited by 8 | Viewed by 5843

Abstract

The Silante Formation is a thick series of continental deposits, exposed along a trench-parallel distance of approximately 300 km within the Western Cordillera of Ecuador. The origin, tectonic setting, age and stratigraphic relationships are poorly known, although these are key to understand the [...] Read more.

The Silante Formation is a thick series of continental deposits, exposed along a trench-parallel distance of approximately 300 km within the Western Cordillera of Ecuador. The origin, tectonic setting, age and stratigraphic relationships are poorly known, although these are key to understand the Cenozoic evolution of the Ecuadorian Andes. We present new sedimentological, stratigraphic, petrographic, radiometric and provenance data from the Silante Formation and underlying rocks. The detailed stratigraphic analysis shows that the Silante Formation unconformably overlies Paleocene submarine fan deposits of the Pilalo Formation, which was coeval with submarine tholeiitic volcanism. The lithofacies of the Silante Formation suggest that the sediments were deposited in a debris flow dominated alluvial fan. Provenance analysis including heavy mineral assemblages and detrital zircon U-Pb ages indicate that sediments of the Silante Formation were derived from the erosion of a continental, calc-alkaline volcanic arc, pointing to the Oligocene to Miocene San Juan de Lachas volcanic arc. Thermochronological data and regional correlations suggest that deposition of the Silante Formation was coeval with regional rock and surface uplift of the Andean margin that deposited alluvial fans in intermontane and back-arc domains. Full article

(This article belongs to the Special Issue Detrital Mineral U/Pb Age Dating and Geochemistry of Magmatic Products in Basin Sequences: State of the Art and Progress)

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24 pages, 3341 KiB

Open AccessArticle

Chromium Isotope Systematics in Modern and Ancient Microbialites

by Sylvie Bruggmann, Alexandra S. Rodler, Robert M. Klaebe, Steven Goderis and Robert Frei

Minerals 2020, 10(10), 928; https://doi.org/10.3390/min10100928 - 20 Oct 2020

Cited by 5 | Viewed by 3275

Abstract

Changes in stable chromium isotopes (denoted as δ⁵³Cr) in ancient carbonate sediments are increasingly used to reconstruct the oxygenation history in Earth’s atmosphere and oceans through time. As a significant proportion of marine carbonate older than the Cambrian is microbially-mediated, the [...] Read more.

Changes in stable chromium isotopes (denoted as δ⁵³Cr) in ancient carbonate sediments are increasingly used to reconstruct the oxygenation history in Earth’s atmosphere and oceans through time. As a significant proportion of marine carbonate older than the Cambrian is microbially-mediated, the utility of δ⁵³Cr values in ancient carbonates hinges on whether these sediments accurately capture the isotope composition of their environment. We report Cr concentrations (Cr) and δ⁵³Cr values of modern marginal marine and non-marine microbial carbonates. These data are supported by stable C and O isotope compositions, as well as rare earth elements and yttrium (REY) concentrations. In addition, we present data on ancient analogs from Precambrian strata. Microbial carbonates from Marion Lake (Australia, δ⁵³Cr ≈ 0.99‰) and Mono Lake (USA, ≈0.78‰) display significantly higher δ⁵³Cr values compared with ancient microbialites from the Andrée Land Group in Greenland (720 Ma, ≈0.36‰) and the Bitter Springs Formation in Australia (800 Ma, ≈−0.12‰). The δ⁵³Cr values are homogenous within microbialite specimens and within individual study sites. This indicates that biological parameters, such as vital effects, causing highly variable δ⁵³Cr values in skeletal carbonates, do not induce variability in δ⁵³Cr values in microbialites. Together with stable C and O isotope compositions and REY patterns, δ⁵³Cr values in microbialites seem to be driven by environmental parameters such as background lithology and salinity. In support, our Cr and δ⁵³Cr results of ancient microbial carbonates agree well with data of abiotically precipitated carbonates of the Proterozoic. If detrital contamination is carefully assessed, microbialites have the potential to record the δ⁵³Cr values of the waters from which they precipitated. However, it remains unclear if these δ⁵³Cr values record (paleo-) redox conditions or rather result from other physico-chemical parameters. Full article

(This article belongs to the Special Issue Copper and Other Metallic Isotope Systems)

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22 pages, 6431 KiB

Open AccessArticle

SHRIMP U–Pb Zircon Ages, Geochemistry and Sr–Nd–Hf Isotope Systematics of the Zalute Intrusive Suite in the Southern Great Xing’an Range, NE China: Petrogenesis and Geodynamical Implications

by Huanan Liu, Feng Yuan, Shengjin Zhao, Mingjing Fan and Xiangguo Guo

Minerals 2020, 10(10), 927; https://doi.org/10.3390/min10100927 - 20 Oct 2020

Cited by 5 | Viewed by 2940

Abstract

An integrated zircon geochronological, elemental geochemical, and Sr–Nd–Hf isotopic investigation was carried out on a suite of dioritic–granitic rocks at Zalute in the southern Great Xing’an Range (SGXR), NE China, in order to probe the source and petrogenesis of these granitoid rocks and [...] Read more.

An integrated zircon geochronological, elemental geochemical, and Sr–Nd–Hf isotopic investigation was carried out on a suite of dioritic–granitic rocks at Zalute in the southern Great Xing’an Range (SGXR), NE China, in order to probe the source and petrogenesis of these granitoid rocks and further constrain the geodynamical setting of early Early Cretaceous magmatism. The results of Sensitive High-Resolution Ion Micro Probe (SHRIMP) zircon U–Pb dating reveal that the Zalute dioritic–granitic rocks have a consistent crystallization age of ca. 137–136 Ma, consisting of quartz diorite (136 ± 1.4 Ma), monzogranite (136 ± 0.8 Ma), and granite porphyry (137 ± 1.3 Ma), which record an early Early Cretaceous magmatic intrusion. Geochemically, the quartz diorites, monzogranites, and granite porphyries are mostly high-K calc-alkaline and show features of typical I-type affinity. They possess uniform and depleted Sr–Nd–Hf isotopic compositions (e.g., initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7035 to 0.7049, ε_Nd(t) of −0.02 to +2.61, and ε_Hf(t) of +6.8 to +9.6), reflecting a common source, whose parental magma is best explained as resulting from the partial melting of juvenile source rocks in the lower crust produced by underplating of mantle-derived mafic magma, with minor involvement of ancient crustal components. Evidence from their close spatio–temporal relationship, common source, and the compositional trend is consistent with a magmatic differentiation model of the intermediate-felsic intrusive suite, with continued fractional crystallization from quartz diorites, towards monzogranites, then to granite porphyries. Combined with previously published data in the SGXR, our new results indicate that the Zalute intermediate-felsic intrusive suite was formed during the post-collisional extension related to the closure of the Mongol–Okhotsk Ocean and subsequent slab break-off. Full article

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

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15 pages, 2022 KiB

Open AccessArticle

Data Evaluation for Cassiterite and Coltan Fingerprinting

by Hans-Eike Gäbler, Wilhelm Schink and Timo Gawronski

Minerals 2020, 10(10), 926; https://doi.org/10.3390/min10100926 - 19 Oct 2020

Cited by 3 | Viewed by 3610

Abstract

Within due diligence concepts for raw material supply chains, the traceability of a shipment is a major aspect that has to be taken into account. Cassiterite and coltan are two so-called conflict minerals for which traceability systems have been established. To provide additional [...] Read more.

Within due diligence concepts for raw material supply chains, the traceability of a shipment is a major aspect that has to be taken into account. Cassiterite and coltan are two so-called conflict minerals for which traceability systems have been established. To provide additional credibility to document-based traceability systems the German Federal Institute for Geosciences and Natural Resources (BGR) has developed the analytical fingerprint (AFP) for the minerals coltan, cassiterite, and wolframite. AFP is based on the analysis of a sample from a shipment with a declared origin and evaluates whether the declared origin is plausible or not. This is done by comparison to reference samples previously taken at the declared mine site. In addition to the generation of the analytical data, the data evaluation step, with the aim to state whether the declared origin is plausible or not, is of special importance. Two data evaluation approaches named “Kolmogorov–Smirnov distance (KS-D) approach” and “areas ratio approach” are applied to coltan and cassiterite and result in very low rates of false negative results, which is desired for AFP. The areas ratio approach based on hypothesis testing and a more sophisticated evaluation of the multivariate data structure has some advantages in terms of producing lower rates of false positive results compared to the KS-D approach. Full article

(This article belongs to the Special Issue Analytical Tools to Constrain the Origin of Minerals)

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18 pages, 2481 KiB

Open AccessReview

Prospects of Applying MWD Technology for Quality Management of Drilling and Blasting Operations at Mining Enterprises

by Valentin Isheyskiy and José A. Sanchidrián

Minerals 2020, 10(10), 925; https://doi.org/10.3390/min10100925 - 19 Oct 2020

Cited by 29 | Viewed by 5865

Abstract

This paper presents a review of measurement while drilling (MWD) technology as applied to the mining industry, describes its development path, provides a global review of literature on this topic, and outlines further trends of development for research on MWD application in drilling [...] Read more.

This paper presents a review of measurement while drilling (MWD) technology as applied to the mining industry, describes its development path, provides a global review of literature on this topic, and outlines further trends of development for research on MWD application in drilling and blasting (D&B) operations at mining enterprises. The current review serves as a starting point for anyone interested in the research or application of MWD technology in Mining and Construction. In the paper, the authors examine major works of researchers in this area, describe current state of the art, and propose a way to improve MWD for drilling equipments. The paper contains examples of technology application in various processes, associated with drilling and mining operations, describes approaches and problems of MWD system utilization, revealed in the course of data collection and analysis of drilling processes. The study also presents a summary of existing approaches in the area of data validation and verification, applied up to the present day to cope with the problems of global MWD use in Mining and Construction. The authors outline future areas of study which are of interest and deserve the attention of the scientific community and researchers working on the development of MWD technology. Full article

(This article belongs to the Section Mineral Deposits)

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18 pages, 2378 KiB

Open AccessArticle

Structural Modifications of Single-Crystal Aragonite CaCO₃ Beginning at ~15 GPa: In Situ Vibrational Spectroscopy and X-Ray Diffraction Evidence

by Jing Gao, Yungui Liu, Xiang Wu, Xueyin Yuan, Yingxin Liu and Wen Su

Minerals 2020, 10(10), 924; https://doi.org/10.3390/min10100924 - 19 Oct 2020

Cited by 9 | Viewed by 4193

Abstract

The structural chemistry of carbonates under mantle conditions facilitates our understanding of carbon recycling pathways in the earth’s interior. It also has impacts on the dynamics of mantle–slab interactions. Aragonite is a common calcium carbonate mineral in pelagic marine sediments. The structural chemistry [...] Read more.

The structural chemistry of carbonates under mantle conditions facilitates our understanding of carbon recycling pathways in the earth’s interior. It also has impacts on the dynamics of mantle–slab interactions. Aragonite is a common calcium carbonate mineral in pelagic marine sediments. The structural chemistry of single-crystal aragonite during successive compression and the behavior of a structural H⁺ have been investigated by micro-vibrational spectroscopy and synchrotron X-ray diffraction techniques in diamond anvil cells. We describe a reduction of the b-axial compressibility beginning at ~15 GPa, and the related discontinuities in the first-order derivatives of the vibrational modes. The structural modifications of aragonite are manifested by mutations occurring in the pressure relations of the wavenumbers of the O-C-O bending modes, and of the bandwidth and band intensities of the measured internal and external modes. These anomalies are indicative of changes occurring in the force constant of the C-O bonds, and possibly a second-order phase transition. Besides, the [CaO₉] polyhedra begin to deform, possibly with some Ca-O bonds becoming elongated and the others shortening. An increase in the co-ordination number for the Ca²⁺ sites could be expected under higher pressures. Additionally, the weakening of the OH modes may imply H⁺-loss from the aragonite lattice above 11.5 GPa. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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Graphical abstract

20 pages, 2221 KiB

Open AccessArticle

Improved Geotechnical Behavior of an Expansive Soil Amended with Tire-Derived Aggregates Having Different Gradations

by Amin Soltani, Abbas Taheri, An Deng and Brendan C. O’Kelly

Minerals 2020, 10(10), 923; https://doi.org/10.3390/min10100923 - 19 Oct 2020

Cited by 31 | Viewed by 4474

Abstract

This experimental laboratory study examines the potential use of tire-derived aggregate (TDA) products as an additive to alleviate the inferior geotechnical properties of a subgrade deposit of clay soil with high expansivity. A total of ten mix designs—the unamended soil and nine soil–TDA [...] Read more.

This experimental laboratory study examines the potential use of tire-derived aggregate (TDA) products as an additive to alleviate the inferior geotechnical properties of a subgrade deposit of clay soil with high expansivity. A total of ten mix designs—the unamended soil and nine soil–TDA blends prepared at 5%, 10% and 20% TDA contents (by dry mass) using three different TDA gradations/sizes—were examined. The experiments included standard Proctor compaction, oedometer swell and unconfined compression tests. The TDA materials’ lower specific gravity, hydrophobic character and higher energy absorption capacity compared with the soil solids led to notable reductions in the soil compaction characteristics. The amendment of the soil with TDA resulted in notable decreases in the rate and magnitude of swelling—the observed reductions were in favor of higher TDA contents, with larger TDA particle size being a secondary factor. Further, for any given TDA size, the variations of strength and toughness with respect to TDA content exhibited rise–fall relationships, peaking at 5% TDA and then decreasing for higher TDA contents. The stiffness and ductility parameters, however, were found to monotonically decrease and increase with the TDA content, respectively. Finally, TDA contents of up to 10%, with gradations equivalent to those of medium and coarse sands, were found to reduce the soil’s swelling potential from high to moderate expansivity, while simultaneously improving its strength-related features, and thus can be deemed as optimum mix design choices from a geotechnical perspective. Full article

(This article belongs to the Special Issue Stabilisation and Reinforcement of Clays with Environmentally Friendly Materials)

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14 pages, 3062 KiB

Open AccessArticle

Influence of Solid Content, Cement/Tailings Ratio, and Curing Time on Rheology and Strength of Cemented Tailings Backfill

by Jiajian Li, Erol Yilmaz and Shuai Cao

Minerals 2020, 10(10), 922; https://doi.org/10.3390/min10100922 - 19 Oct 2020

Cited by 82 | Viewed by 4201

Abstract

Understanding the flow process of cemented tailings backfill (CTB) is important for successful pumping into underground stopes. This study examines the effects of solid content (SC), cement/tailings (c/t) ratio, and curing time (CT) on rheological and mechanical properties of CTB mixes. The slurry [...] Read more.

Understanding the flow process of cemented tailings backfill (CTB) is important for successful pumping into underground stopes. This study examines the effects of solid content (SC), cement/tailings (c/t) ratio, and curing time (CT) on rheological and mechanical properties of CTB mixes. The slurry concentration of the mixes was 65, 67, and 69 wt. %, with c/t ratios ranging from 1:4 to 1:20. Unconfined compressive strength (UCS) tests were performed on hardened CTB mixes after curing 3, 7, and 28 days. The rheological properties of CTB slurries are mainly related to SC. The yield stress and viscosity of fresh mixes increase with increasing SC, but the pipeline resistance loss (PRL) also increases with increasing SC. According to the analysis of variance, the SC and flow rate are the most significant parameters which greatly affect the PRL performance. The c/t and CT parameters are the most significant parameters for affecting the shrinkage rate. The findings offer a reference for theoretical optimization for mine filling systems of similar type. Full article

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

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17 pages, 2300 KiB

Open AccessArticle

Dissolution, Stability and Solubility of Tooeleite [Fe₆(AsO₃)₄(SO₄)(OH)₄·4H₂O] at 25–45 °C and pH 2–12

by Zongqiang Zhu, Jun Zhang, Yinian Zhu, Jie Liu, Shen Tang, Lihao Zhang and Yaru Wang

Minerals 2020, 10(10), 921; https://doi.org/10.3390/min10100921 - 19 Oct 2020

Cited by 7 | Viewed by 3514

Abstract

Tooeleite [Fe₆(AsO₃)₄(SO₄)(OH)₄·4H₂O] was synthesized and characterized to investigate its possible immobilization for arsenic in acidic and alkali environments by a long-term dissolution of 330 d. The synthetic tooeleite was platy crystallites [...] Read more.

Tooeleite [Fe₆(AsO₃)₄(SO₄)(OH)₄·4H₂O] was synthesized and characterized to investigate its possible immobilization for arsenic in acidic and alkali environments by a long-term dissolution of 330 d. The synthetic tooeleite was platy crystallites of ~1μm across, giving the lattice parameters of a = 6.4758 Å, b = 19.3737 Å and c = 8.9170 Å. For the tooeleite dissolution, the dissolved arsenic concentration showed the lowest value of 427.3~435.8 mg/L As at initial pH 12 (final pH 5.54). The constituents were dissolved preferentially in the sequence of SO₄²⁻ > AsO₃³⁻ > Fe³⁺ in the aqueous medium at initial pH 2–12. The dissolved iron, arsenite and sulfate existed mainly as FeSO₄⁺/Fe³⁺, H₃AsO₃⁰ and SO₄²⁻ at initial pH 2, and in the form of Fe(OH)₃⁰/Fe(OH)₂⁺, H₃AsO₃⁰ and SO₄²⁻ at initial pH 12, respectively. The tooeleite dissolution was characterized by the preferential releases of SO₄²⁻ anions from solid surface into aqueous medium, which was fundamentally controlled by the Fe-O/OH bond breakages and the outer OH⁻ group layers. From the data of the dissolution at 25 °C and initial pH 2 for 270–330 d, the ion-activity product [logˍIAP], which equaled the solubility product [K_sp] at the dissolution equilibrium, and the Gibbs free energy of formation [ΔG_f^o] were estimated as −200.28 ± 0.01 and −5180.54 ± 0.07 kJ/mol for the synthetic tooeleite, respectively. Full article

(This article belongs to the Special Issue Elemental and Isotopic Approaches to Characterize Sources and Processes Controlling the Budgets of Toxic Metals in the Environment)

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20 pages, 3403 KiB

Open AccessArticle

Predictive Model of Setting Times and Compressive Strengths for Low-Alkali, Ambient-Cured, Fly Ash/Slag-Based Geopolymers

by Supphatuch Ukritnukun, Pramod Koshy, Aditya Rawal, Arnaud Castel and Charles Christopher Sorrell

Minerals 2020, 10(10), 920; https://doi.org/10.3390/min10100920 - 17 Oct 2020

Cited by 30 | Viewed by 3492

Abstract

The effects of curing temperature, blast furnace slag content, and Ms on the initial and final setting times, and compressive strengths of geopolymer paste and mortars are examined. The present work demonstrates that ambient-cured geopolymer pastes and mortars can be fabricated without requiring [...] Read more.

The effects of curing temperature, blast furnace slag content, and Ms on the initial and final setting times, and compressive strengths of geopolymer paste and mortars are examined. The present work demonstrates that ambient-cured geopolymer pastes and mortars can be fabricated without requiring high alkalinity activators or thermal curing, provided that the ratios of Class F fly ash (40–90 wt%), blast furnace slag (10–60 wt%), and low alkalinity sodium silicate (Ms = 1.5, 1.7, 2.0) are appropriately balanced. Eighteen mix designs were assessed against the criteria for setting time and compressive strength according to ASTM C150 and AS 3972. Using these data, flexible and reproducible mix designs in terms of the fly ash/slag ratio and Ms were mapped and categorised. The optimal mix designs are 30–40 wt% slag with silicate modulus (Ms) = 1.5–1.7. These data were used to generate predictive models for initial and final setting times and for ultimate curing times and ultimate compressive strengths. These projected data indicate that compressive strengths >100 MPa can be achieved after ambient curing for >56 days of mixes of ≥40 wt% slag. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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17 pages, 3247 KiB

Open AccessEditor’s ChoiceReview

Clay Minerals in Hydrothermal Systems

by Paolo Fulignati

Minerals 2020, 10(10), 919; https://doi.org/10.3390/min10100919 - 16 Oct 2020

Cited by 53 | Viewed by 10579

Abstract

The study of active and fossil hydrothermal systems shows clay minerals to be a fundamental tool for the identification and characterization of hydrothermal alteration facies. The occurrence and composition of hydrothermal alteration facies could provide useful information on the physicochemical conditions of the [...] Read more.

The study of active and fossil hydrothermal systems shows clay minerals to be a fundamental tool for the identification and characterization of hydrothermal alteration facies. The occurrence and composition of hydrothermal alteration facies could provide useful information on the physicochemical conditions of the hydrothermal activity affecting a rock volume. In particular, clay minerals (i.e., smectite group, chlorite, illite, kaoline group, pyrophyllite, biotite) are pivotal for extrapolating important parameters that strongly affect the development of water/rock interaction processes such as the temperature and pH of the hydrothermal environment. This work aims to give a general reference scheme concerning the occurrence of clay minerals in hydrothermal alteration paragenesis, their significance, and the information that can be deduced by their presence and chemical composition, with some examples from active and fossil hydrothermal systems around the world. The main mineralogical geothermometers based on chlorite and illite composition are presented, together with the use of hydrogen and oxygen isotope investigation of clay minerals in hydrothermal systems. These techniques provide a useful tool for the reconstruction of the origin and evolution of fluids involved in hydrothermal alteration. Finally, a list of oxygen and hydrogen fractionation factor equations between the main clay minerals and water is also provided. Full article

(This article belongs to the Special Issue Clays, Clay Minerals and Geology)

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19 pages, 5069 KiB

Open AccessArticle

Emergences of New Technology for Ultrafast Automated Mineral Phase Identification and Quantitative Analysis Using the CORIOSITY Laser-Induced Breakdown Spectroscopy (LIBS) System

by Kheireddine Rifai, Marie-Chloé Michaud Paradis, Zofia Swierczek, François Doucet, Lütfü Özcan, Alejandro Fayad, Jing Li and François Vidal

Minerals 2020, 10(10), 918; https://doi.org/10.3390/min10100918 - 16 Oct 2020

Cited by 19 | Viewed by 6251

Abstract

Geochemical and mineralogical characterization studies play an important role in the definition of mineral deposits. Each mineral system has a unique set of minerals with different chemical makeup and physical properties. Platinum-group elements (PGEs), for example, are scarce resources with many applications. The [...] Read more.

Geochemical and mineralogical characterization studies play an important role in the definition of mineral deposits. Each mineral system has a unique set of minerals with different chemical makeup and physical properties. Platinum-group elements (PGEs), for example, are scarce resources with many applications. The optimization of extraction process efficiency is therefore crucial to prevent resource shortage and increased bulk prices. To improve the mineral liberation process, high throughput sensors must be added alongside the production line as part of fast process analysis implementation. Current analytical methods are either ineffective to assess PGE content, or unusable in the conditions of the processing facilities. This article shows how Laser-induced breakdown spectroscopy (LIBS) technology, developed by ELEMISSION Inc, can circumvent these drawbacks by enabling automated, ultra-fast, and precise quantitative mineral analyses in any working environment. The drill core samples that were used in this study were collected at the Stillwater platinum group element mine in the United States. The data used for the mineralogical database was validated using the TESCAN Integrated Mineral Analyzer (TIMA) instrument. Full article

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

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28 pages, 7124 KiB

Open AccessArticle

Tourmalines as a Tool in Provenance Studies of Terrigenous Material in Extra-Carpathian Albian (Uppermost Lower Cretaceous) Sands of Miechów Synclinorium, Southern Poland

by Jakub Kotowski, Krzysztof Nejbert and Danuta Olszewska-Nejbert

Minerals 2020, 10(10), 917; https://doi.org/10.3390/min10100917 - 16 Oct 2020

Cited by 8 | Viewed by 3194

Abstract

The mature transgressive Albian quartz sands in the Miechów Synclinorium contain a poor (<1%) heavy mineral suite consisting of tourmaline, rutile, garnet, staurolite, ilmenite, zircon, monazite, kyanite, and gahnite. The other minerals, especially those containing Fe and Ti (e.g., biotite), are subordinate. Over [...] Read more.

The mature transgressive Albian quartz sands in the Miechów Synclinorium contain a poor (<1%) heavy mineral suite consisting of tourmaline, rutile, garnet, staurolite, ilmenite, zircon, monazite, kyanite, and gahnite. The other minerals, especially those containing Fe and Ti (e.g., biotite), are subordinate. Over 512 tourmaline grains from seven outcrops in the Miechów Segment were analysed using electron probe microanalysis (EPMA). The majority of grains belong to the alkali tourmaline group in which the X-site is dominated by Na (0.4 to 0.9 apfu). Detrital tourmalines are mainly dravite with a prevalent schorl end-member with average X_Mg values over 0.6. Apart from Mg and Fe, the other Y-site cations rarely exceed 0.1 apfu. Fluorine content is usually below the detection limit. Their chemical composition suggests that most tourmaline grains were sourced from Al-rich and Al-poor metapelites/metapsammites. The main source rocks for the Albian sands were rocks from low- to medium-grade metamorphism, probably from Al-rich quartz-muscovite schist and/or muscovite rich gneisses. Additional minor source rocks were granites and pegmatites coexisting with them. A comparison of the examined tourmaline to tourmaline from possible source areas indicates that these areas were located in the eastern part of the Bohemian Massif and/or eastern Sudetes. Full article

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

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12 pages, 2695 KiB

Open AccessEditor’s ChoiceArticle

Diamonds Certify Themselves: Multivariate Statistical Provenance Analysis

by Catherine E. McManus, Nancy J. McMillan, James Dowe and Julie Bell

Minerals 2020, 10(10), 916; https://doi.org/10.3390/min10100916 - 16 Oct 2020

Cited by 14 | Viewed by 3857

Abstract

The country or mine of origin is an important economic and societal issue inherent in the diamond industry. Consumers increasingly want to know the provenance of their diamonds to ensure their purchase does not support inhumane working conditions. Governments around the world reduce [...] Read more.

The country or mine of origin is an important economic and societal issue inherent in the diamond industry. Consumers increasingly want to know the provenance of their diamonds to ensure their purchase does not support inhumane working conditions. Governments around the world reduce the flow of conflict diamonds via paper certificates through the Kimberley Process, a United Nations mandate. However, certificates can be subject to fraud and do not provide a failsafe solution to stopping the flow of illicit diamonds. A solution tied to the diamonds themselves that can withstand the cutting and manufacturing process is required. Here, we show that multivariate analysis of LIBS (laser-induced breakdown spectroscopy) diamond spectra predicts the mine of origin at greater than 95% accuracy, distinguishes between natural and synthetic stones, and distinguishes between synthetic stones manufactured in different laboratories by different methods. Two types of spectral features, elemental emission peaks and emission clusters from C-N and C-C molecules, are significant in the analysis, indicating that the provenance signal is contained in the carbon structure itself rather than in inclusions. Full article

(This article belongs to the Special Issue Analytical Tools to Constrain the Origin of Minerals)

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34 pages, 8444 KiB

Open AccessFeature PaperArticle

Impact of Paleosalinity, Paleoredox, Paleoproductivity/Preservation on the Organic Matter Enrichment in Black Shales from Triassic Turbidites of Semanggol Basin, Peninsular Malaysia

by Zulqarnain Sajid, Mohd S. Ismail, Muhammad Noor Amin Zakariah, Haylay Tsegab, José Antonio Gámez Vintaned, Tanzila Hanif and Nisar Ahmed

Minerals 2020, 10(10), 915; https://doi.org/10.3390/min10100915 - 16 Oct 2020

Cited by 17 | Viewed by 5493

Abstract

Turbidite-associated black shale of the Semanggol Formation is extensively distributed in the northwestern part of the Western Belt, Peninsular Malaysia. The black shale occurs as a dark grey to black and thick to medium-bedded deposit. It represents the distal part of submarine fan [...] Read more.

Turbidite-associated black shale of the Semanggol Formation is extensively distributed in the northwestern part of the Western Belt, Peninsular Malaysia. The black shale occurs as a dark grey to black and thick to medium-bedded deposit. It represents the distal part of submarine fan system (outer-fan) overlying interbedded sandstone to shale facies of the mid-fan and conglomeratic pebbly sandstone facies of the inner-fan. Field observations and its widespread occurrence have resulted in the black shale being considered as a potential analog for a source rock in offshore Peninsular Malaysia. The present study includes detailed mineralogical (XRD, SEM, and EDX analysis), inorganic geochemical (major oxides, trace elements TEs, and rare earth elements REEs), and Rock-Eval pyrolysis analyses of the black shale samples, collected from the Gunung Semanggol, Bukit Merah, and Nami areas in northwestern Peninsular Malaysia. The primary focus of this study is to investigate the provenance, paleoredox conditions, paleoclimate, sedimentary rate, paleoproductivity, and upwelling system that would be helpful to understanding the role of these parameters in the enrichment of organic matter (OM) in the black shale. The Rock-Eval analysis shows that the black shale of the Semanggol Formation comprises type-III kerogens, which suggests organic input from a terrestrial source. The black shale also contains mature to postmature organic matter. Based on the mineralogical analysis, the mineral composition of the black shale comprises illite and kaolinite, with abundant traces of quartz and feldspar as well as few traces of titanium and zircon. Inorganic geochemical data designate black shale deposition in a passive margin setting that has experienced moderate to strong weathering, semi-arid to hot arid climate, and moderate sedimentation rate. Ratios of Ni/Co, U/Th, and V/(V+Ni) along with slightly negative to positive Ce* anomalies and U_EF-Mo_EF cross-plot unanimously indicate anoxic/dysoxic water conditions that are suitable for organic matter preservation. Geochemical proxies related to modern upwelling settings (i.e., Cd/Mo, Co vs. Mn) show that the deep marine black shale was strongly influenced by persistent upwelling, a first-order controlling factor for organic matter enrichment in the distal part (outer fan of the submarine fan system) of the Semanggol Basin. However, productivity-controlled upwelling and a high sedimentary rate, as well as high-productivity in oxygen-depleted settings without strong anoxic conditions, has played an essential role in the accumulation of organic matter. Full article

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

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35 pages, 13838 KiB

Open AccessArticle

A Defect Study and Classification of Brown Diamonds with Non-Deformation-Related Color

by Thomas Hainschwang, Franck Notari and Gianna Pamies

Minerals 2020, 10(10), 914; https://doi.org/10.3390/min10100914 - 15 Oct 2020

Cited by 25 | Viewed by 7127

Abstract

While the first part of this study took a detailed look at the properties, defects and classification of brown diamonds with deformation-related (DR) brown color and compared them to pink to purple to red diamonds, this second part covers diamonds with non-deformation-related (referred [...] Read more.

While the first part of this study took a detailed look at the properties, defects and classification of brown diamonds with deformation-related (DR) brown color and compared them to pink to purple to red diamonds, this second part covers diamonds with non-deformation-related (referred to as NDR in this study) brown color, including diamonds with treatment-induced brown color and synthetic brown diamonds. It was found that the natural NDR brown diamonds include CO₂ and Pseudo CO₂ diamonds as well as certain hydrogen-rich diamonds. Based on these, the new classification of NDR brown diamonds has been elaborated, resulting in 5 different classes. The detailed defect study performed has shown and confirmed the complexity of the CO₂ and Pseudo CO₂ diamonds; the probable link between structurally bound oxygen and some of the spectroscopic features such as the 480 nm absorption band is apparent in these diamonds. One of the most interesting findings was made through the low temperature NIR spectroscopy of some usually hydrogen-rich diamonds, which has defined a defect of great interest, the 1330 nm center; we suggest that this defect, together with the many lines in the 970 to 1000 nm range—referred to as the 990 nm series in this study—are responsible for the complex UV-Vis-NIR spectra seen of these diamonds. The results indicate that both features are nickel-nitrogen-related defects, the 1330 nm defect without involvement of hydrogen and the 990 nm series likely with hydrogen involved. Another surprising result was that during various treatment experiments performed we created dark orangish brown color in originally pale yellow “cape” diamonds by HPHT treatment at 2500 °C. It is suggested that the creation of this brown hue is related to the destruction or transformation of the N3 center at such extreme conditions. Full article

(This article belongs to the Special Issue Gemstone Analysis by Spectroscopy and Microscopy)

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17 pages, 10612 KiB

Open AccessArticle

Representation of Kinetics Models in Batch Flotation as Distributed First-Order Reactions

by Luis Vinnett and Kristian E. Waters

Minerals 2020, 10(10), 913; https://doi.org/10.3390/min10100913 - 15 Oct 2020

Cited by 18 | Viewed by 5243

Abstract

Four kinetic models are studied as first-order reactions with flotation rate distribution f(k): (i) deterministic nth-order reaction, (ii) second-order with Rectangular f(k), (iii) Rosin–Rammler, and (iv) Fractional kinetics. These models are studied because they are considered as [...] Read more.

Four kinetic models are studied as first-order reactions with flotation rate distribution f(k): (i) deterministic nth-order reaction, (ii) second-order with Rectangular f(k), (iii) Rosin–Rammler, and (iv) Fractional kinetics. These models are studied because they are considered as alternatives to the first-order reactions. The first-order representation leads to the same recovery R(t) as in the original domain. The first-order R_∞-f(k) are obtained by inspection of the R(t) formulae or by inverse Laplace Transforms. The reaction orders of model (i) are related to the shape parameters of first-order Gamma f(k)s. Higher reaction orders imply rate concentrations at k ≈ 0 in the first-order domain. Model (ii) shows reverse J-shaped first-order f(k)s. Model (iii) under stretched exponentials presents mounded first-order f(k)s, whereas model (iv) with derivative orders lower than 1 shows from reverse J-shaped to mounded first-order f(k)s. Kinetic descriptions that lead to the same R(t) cannot be differentiated between each other. However, the first-order f(k)s can be studied in a comparable domain. Full article

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

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21 pages, 9014 KiB

Open AccessArticle

Geochemistry of Groundwater and Naturally Occurring Biogenic Pyrite in the Holocene Fluvial Aquifers in Uphapee Watershed, Macon County, Alabama

by Md Mahfujur Rahman, Ming-Kuo Lee and Ashraf Uddin

Minerals 2020, 10(10), 912; https://doi.org/10.3390/min10100912 - 15 Oct 2020

Cited by 2 | Viewed by 3359

Abstract

Naturally occurring biogenic pyrite has been found in Holocene fluvial aquifers in the Uphapee watershed, Macon County, Alabama. The electron microprobe (EMP) analysis showed that the pyrite grains contain 0.20–0.92 weight% of arsenic (As). The scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) [...] Read more.

Naturally occurring biogenic pyrite has been found in Holocene fluvial aquifers in the Uphapee watershed, Macon County, Alabama. The electron microprobe (EMP) analysis showed that the pyrite grains contain 0.20–0.92 weight% of arsenic (As). The scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) analysis confirmed a similar concentration of As in the pyrite that was consistent with the EMP analysis. The SEM analysis also confirmed the presence of additional trace elements such as cobalt (0.19 wt.%), and nickel (0.15 wt.%), indicative of pyrite’s capacity to sequester As and other trace elements. Pyrite grains were naturally formed and developed as large (20–200 μm) euhedral (i.e., cube, octahedron) crystals and non-framboid aggregates. However, the inductively coupled plasma mass spectrometry (ICP-MS) analysis showed that the As concentration in the groundwater was not high, and it was within the EPA drinking water standard for As (10 µg/L). These results indicate that dissolved As is sequestered in naturally formed pyrite found in the fluvial sediments. The groundwater was moderately reducing to slightly oxidizing (Eh = 46 to173 mV), and nearly neutral to slightly acidic (pH = 5.53 to 6.51). Groundwater geochemistry data indicated a redox sequence of oxidation, denitrification, Mn(IV) reduction, Fe(III) reduction, and sulfate reduction along the flow path in the fluvial aquifer. The downgradient increases in dissolved Mn and then Fe concentrations reflect increased Mn(II) and Fe(II) production via microbial competition as the aquifer becomes progressively more reduced. Bacterial sulfate reduction seems to dominate near the end of the groundwater flow path, as the availability of Mn- and Fe-oxyhydroxides becomes limited in sediments rich in lignitic wood where increasing sulfate reduction leads to the formation of biogenic pyrite. The groundwater is a Ca-SO₄ type and is not SO₄ limited; thus, sulfate may serve as an electron acceptor for the bacterial sulfate-reducing reactions that sequester As into pyrite, which in turn results in very low groundwater As concentration (<2 µg/L). Full article

(This article belongs to the Special Issue Redox Reactivity of Iron Minerals in the Geosphere)

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19 pages, 6394 KiB

Open AccessArticle

Study on the Liberation of Organic Macerals in Coal by Liquid Nitrogen Quenching Pretreatment

by Jinwen Fan, Meili Du and Lei Liu

Minerals 2020, 10(10), 911; https://doi.org/10.3390/min10100911 - 15 Oct 2020

Cited by 4 | Viewed by 2457

Abstract

In order to study the liberation characteristics of different macerals in coal, one must improve the liberation degree of macerals in coal and promote the utilization of macerals based on their properties. Based on the idea of quick cooling to change the brittleness [...] Read more.

In order to study the liberation characteristics of different macerals in coal, one must improve the liberation degree of macerals in coal and promote the utilization of macerals based on their properties. Based on the idea of quick cooling to change the brittleness and toughness of different macerals, the characteristics of macerals in coal are studied here by liquid nitrogen quenching pretreatment. In particular, coarse-grained samples (with a particle size of 1–3 mm) were. For this study, coal samples were sourced from the Yan’an Formation (J₂y), a middle Jurassic coal formation in the Huangling no. 1 coal mine, located in northern Shaanxi Province, China. Firstly, we analyzed the coal properties and coal petrographic characteristics by the Chinese national standard method. Secondly, the distribution characteristics of macerals in different particle sizes (>0.9, 0.5–0.9, 0.1–0.5, and <0.1) were studied. Then, the samples with different particle sizes were quenched with or without liquid nitrogen to obtain the experimental group and blank group products. Finally, the differences in the liberation characteristics between the experimental group and the blank group products were studied via analyzing the micromorphology, specific surface area, pore volume, pore size and liberation degree. Our results for the particles size and liberation degree analysis indicate that inertinite and vitrinite were enriched in the coarse particles (>0.5 mm) and fine particles (<0.1 mm) here, respectively. Moreover, quenching pretreatment could contribute to the liberation of different macerals from coal, mainly because of the different effects of stress on the different components when they suddenly encounter cold, and this kind of liberation is mainly arc-shaped liberation between different macerals. In addition, along with the above results, this paper presents an optimized model for the liberation of macerals based on a combination of screening, liquid nitrogen quenching pretreatment and re-crushing. Full article

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16 pages, 4281 KiB

Open AccessArticle

Effect of the Cooling Regime on the Mineralogy and Reactivity of Belite-Sulfoaluminate Clinkers

by Sabina Dolenec, Katarina Šter, Maruša Borštnar, Klara Nagode, Andrej Ipavec and Lea Žibret

Minerals 2020, 10(10), 910; https://doi.org/10.3390/min10100910 - 15 Oct 2020

Cited by 16 | Viewed by 4101

Abstract

This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined [...] Read more.

This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days. Full article

(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)

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13 pages, 2350 KiB

Open AccessArticle

Selective Removal of As(V) Ions from Acid Mine Drainage Using Polymer Inclusion Membranes

by Iwona Zawierucha, Anna Nowik-Zajac and Grzegorz Malina

Minerals 2020, 10(10), 909; https://doi.org/10.3390/min10100909 - 14 Oct 2020

Cited by 16 | Viewed by 2792

Abstract

Acid mine drainage (AMD) is globally recognized as one of the environmental pollutants of the priority concern due to high concentrations of toxic metals and sulfates. More rigorous environmental legislation requires exploitation of effective technologies to remove toxic metals from contaminated streams. In [...] Read more.

Acid mine drainage (AMD) is globally recognized as one of the environmental pollutants of the priority concern due to high concentrations of toxic metals and sulfates. More rigorous environmental legislation requires exploitation of effective technologies to remove toxic metals from contaminated streams. In view of high selectivity, effectiveness, durability, and low energy demands, the separation of toxic metal ions using immobilized membranes with admixed extractants could ameliorate water quality. Cellulose triacetate based polymer inclusion membranes (PIMs), with extractant and plasticizer, were studied for their ability to transport of As(V) ions from synthetic aqueous leachates. The effects of the type and concentration of extractant, plasticizer content, and sulfuric acid concentration in source phase on the arsenic removal efficiency have been assessed. Under the best of applied conditions, PIM with Cyanex 921 as extractant and o-nitrophenyl octyl ether (o-NPOE) as plasticizer showed high repeatability and excellent transport activity for selective removal of As(V) from AMD. Full article

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

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32 pages, 15522 KiB

Open AccessFeature PaperArticle

Timing and Metamorphic Evolution of the Ross Orogeny in and around the Mountaineer Range, Northern Victoria Land, Antarctica

by Sang-Bong Yi, Mi Jung Lee, Jong Ik Lee and Hwayoung Kim

Minerals 2020, 10(10), 908; https://doi.org/10.3390/min10100908 - 13 Oct 2020

Cited by 3 | Viewed by 4259

Abstract

The Ross(–Delamerian) Orogeny significantly impacted the formation of the tectonic structure of the Pacific Gondwana margin during the early Paleozoic era. Northern Victoria Land (NVL) in Antarctica preserves the aspect of the Ross Orogeny that led to the union of the Wilson (WT)–Bowers [...] Read more.

The Ross(–Delamerian) Orogeny significantly impacted the formation of the tectonic structure of the Pacific Gondwana margin during the early Paleozoic era. Northern Victoria Land (NVL) in Antarctica preserves the aspect of the Ross Orogeny that led to the union of the Wilson (WT)–Bowers (BT)–Robertson Bay Terrane. The aspect of the Ross Orogeny in the NVL is characterized by subduction of oceanic domains toward the continental margin (continental arc) and the accretion of the associated marine–continental substances from 530–480 Ma. In the Mountaineer Range in NVL, the Ross Orogeny strain zone is identified at the WT/BT boundary regions. In these areas, fold and thrust shear zones are observed and aspects of them can be seen at Mt. Murchison, the Descent Unit and the Black Spider Greenschist zone. The Dessent Unit corresponds to a tectonic slice sheared between the WT and BT. The metamorphic evolution phase of the Dessent Unit is summarized in the peak pressure (M₁), peak temperature (M₂) and retrograde (M₃). The sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb ages of 514.6 ± 2.0 Ma and 499.2 ± 3.4 Ma obtained from the Dessent Unit amphibolite are comparable to the M₁ and M₂ stages, respectively. The Dessent Unit underwent intermediate pressure (P)/temperature (T)-type metamorphism characterized by 10.0–10.5 kbar/~600 °C (M₁) and ~7 kbar/~700 °C (M₂) followed by 4.0–4.5 kbar/~450 °C (M₃). Mafic to intermediate magmatism (497–501 Ma) within the WT/BT boundary region may have given rise to the M₂ stage of the Dessent Unit, and this magmatism is synchronous with the migmatization period of Mt. Murchison (498.3 ± 3.4 Ma). This indicates that a continuous process of fold-shearing–magmatic intrusion–partial melting, which is typically associated with a continental arc orogeny, occurred before and after c. 500 Ma in the Mountaineer Range. During the Ross Orogeny, the Dessent unit was initially subducted underneath the WT at depth (10.0–10.5 kbar, ~35 km) and then thrust into the shallow (~7 kbar, ~23 km), hot (≥700 °C) magmatic arc docking with the Mt. Murchison terrain, where migmatization prevailed. Full article

(This article belongs to the Special Issue U-Pb Dating and Chemistry of Zircon in Metamorphic, Magmatic and Sedimentary Rocks)

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14 pages, 2775 KiB

Open AccessArticle

Assessment of Heating and Cooling of a Spontaneous Fire Source in Coal Deposits—Effect of Coal Grain Size

by Marek Więckowski, Natalia Howaniec and Adam Smoliński

Minerals 2020, 10(10), 907; https://doi.org/10.3390/min10100907 - 13 Oct 2020

Viewed by 1867

Abstract

Fire hazard assessment in coal mines is performed on the basis of concentrations of particular gases emitted from the heating coal deposit, but more precise criteria and indicators are needed to assess fire hazard properly—both during the temperature rise phase and in the [...] Read more.

Fire hazard assessment in coal mines is performed on the basis of concentrations of particular gases emitted from the heating coal deposit, but more precise criteria and indicators are needed to assess fire hazard properly—both during the temperature rise phase and in the coal bed cooling phase. In the paper the impact of coal grinding on hazard assessment of spontaneous fire development in the coal deposit during heating and cooling the fire source was analyzed. The intensity of desorption of ethane, ethylene, propane, propylene, acetylene, carbon monoxide and hydrogen is the resultant of temperature and grinding of coal samples. The results proved that the ratio of concentrations emitted by standard versus coarsely crushed coal for each of the gases, changed both in the growth phase as well as in the temperature drop phase. It was found that as the temperature rose, the effect of coal grinding on the release of ethane, ethylene, propane, propylene and carbon monoxide decreased. The greatest effect of coal grinding was observed in the case of ethane and propane, while the lowest in the case of hydrogen and carbon monoxide. Full article

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15 pages, 4621 KiB

Open AccessArticle

Up-Concentration of Chromium in Stainless Steel Slag and Ferrochromium Slags by Magnetic and Gravity Separation

by Frantisek Kukurugya, Peter Nielsen and Liesbeth Horckmans

Minerals 2020, 10(10), 906; https://doi.org/10.3390/min10100906 - 12 Oct 2020

Cited by 4 | Viewed by 3321

Abstract

Slags coming from stainless steel (SS) and ferrochromium (FeCr) production generally contain between 1 and 10% Cr, mostly present in entrapped metallic particles (Fe–Cr alloys) and in spinel structures. To recover Cr from these slags, magnetic and gravity separation techniques were tested for [...] Read more.

Slags coming from stainless steel (SS) and ferrochromium (FeCr) production generally contain between 1 and 10% Cr, mostly present in entrapped metallic particles (Fe–Cr alloys) and in spinel structures. To recover Cr from these slags, magnetic and gravity separation techniques were tested for up-concentrating Cr in a fraction for further processing. In case of SS slag and low carbon (LC) FeCr slag a wet high intensity magnetic separation can up-concentrate Cr in the SS slag (fraction <150 µm) from 2.3 wt.% to almost 9 wt.% with a yield of 7 wt.%, and in the LC FeCr slag from 3.1 wt.% to 11 wt.% with a yield of 3 wt.%. Different behavior of Cr-containing spinel’s in the two slag types observed during magnetic separation can be explained by the presence or absence of Fe in the lattice of the Cr-containing spinel’s, which affects their magnetic susceptibility. The Cr content of the concentrates is low compared to chromium ores, indicating that additional processing steps are necessary for a recovery process. In the case of high carbon (HC) FeCr slag, a Cr up-concentration by a factor of more than three (from 9 wt.% to 28 wt.%) can be achieved on the as received slag, after a single dry low intensity magnetic separation step, due to the well-liberated Cr-rich compounds present in this slag. After gravity separation of the HC FeCr slag, a fraction with a Cr content close to high grade Cr ores (≥50% Cr₂O₃) can be obtained. This fraction represents 12 wt.% of the HC FeCr slag, and can probably be used directly in traditional smelting processes. Full article

(This article belongs to the Special Issue Ferroalloy Minerals Processing and Technology)

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17 pages, 4893 KiB

Open AccessArticle

Adsorption Behavior and Wettability of Rhodochrosite Surface: Effect of C₁₈ Fatty Acid Unsaturation

by Zhihui Shen, Qin Zhang, Xianbo Li and Qianlin Chen

Minerals 2020, 10(10), 905; https://doi.org/10.3390/min10100905 - 12 Oct 2020

Cited by 13 | Viewed by 2941

Abstract

Mineral surface wettability and its regulation by the adsorption of collectors have an important influence on the flotation performance. The adsorption behavior of C₁₈ fatty acid with different unsaturation and its effect on rhodochrosite wettability was investigated with surface tension, contact angle, [...] Read more.

Mineral surface wettability and its regulation by the adsorption of collectors have an important influence on the flotation performance. The adsorption behavior of C₁₈ fatty acid with different unsaturation and its effect on rhodochrosite wettability was investigated with surface tension, contact angle, and atomic force microscopy (AFM) measurements. The results indicated that rhodochrosite hydrophobicity increased with the increasing concentration of fatty acid, along with the maximum contact angle (θ_max) between hemimicelle concentration (HMC) and critical micelle concentration (CMC). Oleic acid (OA), linoleic acid (LA), and α-linolenic acid (ALA) had a higher θ_max than stearic acid (SA), but the value decreased with the increase of C=C bond number. Besides, preferential adsorption of unsaturated fatty acids on the liquid-air interface can be attributed to the molecule’s steric hindrance resulting from C=C double bond, and the θ kept almost invariant with a higher value of Γ_LG than Γ_SL until HMC. The oriented monolayer and bilayer structure of fatty acids formed gradually on rhodochrosite surface with increasing concentration. However, the θ_max may not necessarily correspond to the beginning of bilayer formation. Cylindrical monolayer and bilayer micelles of SA molecules were observed on rhodochrosite surface at HMC and CMC, respectively. While bilayer structures of unsaturated fatty acids formed before complete coverage of monolayer on rhodochrosite surface because of surface heterogeneity. This work provided a good understanding on the adsorption mechanism of fatty acid on rhodochrosite for flotation. Full article

(This article belongs to the Special Issue Flotation Chemistry, Volume II)

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25 pages, 13037 KiB

Open AccessArticle

Significance and Distribution of Apatite in the Triassic Doig Phosphate Zone, Western Canada Sedimentary Basin

by Pablo Lacerda Silva and R. Marc Bustin

Minerals 2020, 10(10), 904; https://doi.org/10.3390/min10100904 - 12 Oct 2020

Cited by 5 | Viewed by 3239

Abstract

The Doig Phosphate Zone (DPZ) is a phosphate-bearing marine unit located at the base of the Doig Formation, in the Triassic section of the Western Canada Sedimentary Basin. The DPZ has a maximum thickness of 90 m and extends across northeastern British Columbia [...] Read more.

The Doig Phosphate Zone (DPZ) is a phosphate-bearing marine unit located at the base of the Doig Formation, in the Triassic section of the Western Canada Sedimentary Basin. The DPZ has a maximum thickness of 90 m and extends across northeastern British Columbia and west-central Alberta. In this study, we characterize the significance and interpret the origin of apatite in the DPZ through mineralogical and geochemical analyses, thin section study, and field emission scanning electron microscopy. The occurrence of apatite in the DPZ is not evenly distributed but restricted to discrete 10 to 20 cm thick beds, located near the base of the DPZ. Phosphorites are of two types: grainstones composed primarily of unconformity-bounded coated grains, and intraclastic phosphorites composed of detrital silt-sized grains and apatite coated grains in a cryptocrystalline phosphatic matrix. The phosphorite beds are records of stratigraphic condensation due to low detrital input during transgression. The erosionally truncated phosphatic coated grains and intraclasts are interpreted to be a result of various phases of phosphatization, exhumation, erosion, reworking, winnowing, and redeposition in alternating quiescence and storms or bottom currents. The abundance of pyrite and chalcophile trace elements, as well as the low concentration of proxy elements for organic matter productivity and preservation, are further evidence of stratigraphic condensation, with sulfidic pore water development and extensive organic recycling promoted by biological activity during the long exposure times. The phosphorites were formed under oxygenated water conditions, as suggested by the depletion in Ce and the presence of a diverse benthic fauna. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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38 pages, 14675 KiB

Open AccessFeature PaperArticle

A Defect Study and Classification of Brown Diamonds with Deformation-Related Color

by Thomas Hainschwang, Franck Notari and Gianna Pamies

Minerals 2020, 10(10), 903; https://doi.org/10.3390/min10100903 - 12 Oct 2020

Cited by 21 | Viewed by 9033

Abstract

For this study, the properties of a large sample of various types of brown diamonds with a deformation-related (referred to as “DR” in this work) color were studied to properly characterize and classify such diamonds, and to compare them to pink to purple [...] Read more.

For this study, the properties of a large sample of various types of brown diamonds with a deformation-related (referred to as “DR” in this work) color were studied to properly characterize and classify such diamonds, and to compare them to pink to purple to red diamonds. The acquisition of low temperature NIR spectra for a large range of brown diamonds and photoexcitation studies combined with various treatment experiments have opened new windows into certain defect characteristics of brown diamonds, such as the amber centers and naturally occurring H1b and H1c centers. It was determined that the amber centers (referred to as “AC” in this work) exhibit rather variable behaviors to annealing and photoexcitation; the annealing temperature of these defects were determined to range from 1150 to >1850 °C and it was found that the 4063 cm⁻¹ AC was the precursor defect of many other ACs. It is suggested that the amber centers in diamonds that contain at least some C centers are essentially identical to the ones seen in diamonds without C centers, but that they likely have a negative charge. The study of the naturally occurring H1b and H1c link them to the amber centers, specifically to the one at 4063 cm⁻¹. Annealing experiments have shown that the H1b and H1c defects and the 4063 cm⁻¹ AC were in line with each other. The obvious links between these defects points towards our suggestion that the H1b and H1c defects are standalone defects that consist of multiple vacancies and nitrogen and that they are—in the case of brown diamonds—a side product of the AC formation. A new classification of DR brown diamonds was elaborated that separates the diamonds in six different classes, depending on type and AC. This classification had been completed recently with the classification of brown diamonds with a non-deformation-related color (referred to as “NDR”), giving a total of 11 classes of brown diamonds. Full article

(This article belongs to the Special Issue Gemstone Analysis by Spectroscopy and Microscopy)

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22 pages, 6389 KiB

Open AccessArticle

Reflectance Spectroscopy of Ammonium Salts: Implications for Planetary Surface Composition

by Maximiliano Fastelli, Paola Comodi, Alessandro Maturilli and Azzurra Zucchini

Minerals 2020, 10(10), 902; https://doi.org/10.3390/min10100902 - 11 Oct 2020

Cited by 13 | Viewed by 4253

Abstract

Recent discoveries have demonstrated that the surfaces of Mars, Ceres and other celestial bodies, as well as asteroids and comets, are characterized by the presence of ammonium-bearing minerals. A careful study of remote data compared with the analyses of more accurate laboratory data [...] Read more.

Recent discoveries have demonstrated that the surfaces of Mars, Ceres and other celestial bodies, as well as asteroids and comets, are characterized by the presence of ammonium-bearing minerals. A careful study of remote data compared with the analyses of more accurate laboratory data might allow a better remote characterization of planetary bodies. In this paper, the reflectance spectra of some ammoniated hydrous and anhydrous salts, namely sal-ammoniac NH₄Cl, larderellite (NH₄)B₅O₇(OH)₂·H₂O, mascagnite (NH₄)SO₄, struvite (NH₄)MgPO₄·6H₂O and tschermigite (NH₄)Al(SO₄)₂·12H₂O, were collected at 293 and at 193 K. The aim is to detect how the NH₄ vibrational features are affected by the chemical and structural environment. All samples were recovered after cooling cycles and were characterized by X-ray powder diffraction. Reflectance spectra of the studied minerals show absorption features around 1.3, 1.6, 2.06, 2.14, 3.23, 5.8 and 7.27 μm, related to the ammonium group. Between them, the 2ν₃ at ~1.56 μm and the ν₃ + ν₄ at ~2.13 μm are the most affected modes by crystal structure type, with their position being strictly related to both anionic group and the strength of the hydrogen bonds. The reflectance spectra of water-rich samples [struvite (NH₄)MgPO₄·6(H₂O) and tschermigite (NH₄)Al(SO₄)₂·12(H₂O)] show only H₂O fundamental absorption features in the area from 2 to 2.8 μm and a band from hygroscopic water at 3 μm. Thermal analyses (TA), thermal gravimetry (TG) and differential scanning calorimetry (DSC) allowed to evaluate the dehydration temperatures and the occurring phase transitions and decompositions in the analyzed samples. In almost all samples, endothermic peaks at distinct temperatures were registered associated to loss of water molecules, differently linked to the structures. Moreover, an endothermic peak at 465 K in sal-ammoniac was associated to the phase transition from CsCl to NaCl structure type. Full article

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

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Minerals, Volume 10, Issue 10 (October 2020) – 95 articles

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