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Minerals, Volume 10, Issue 1 (January 2020) – 85 articles

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Cover Story (view full-size image) The paper presents new data on the internal structure of super-deep diamonds originating from [...] Read more.
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Open AccessArticle
Metasomatic Reactions between Archean Dunite and Trondhjemite at the Seqi Olivine Mine in Greenland
Minerals 2020, 10(1), 85; https://doi.org/10.3390/min10010085 - 20 Jan 2020
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Abstract
A metasomatic zone formed between the contact of a 2940 ± 5 Ma intrusive trondhjemite sheet in the Archean dunite of the Seqi Ultramafic Complex, SW Greenland, consists of three distinct mineral zones dominated by (1) talc, (2) anthophyllite, and (3) phlogopite. These [...] Read more.
A metasomatic zone formed between the contact of a 2940 ± 5 Ma intrusive trondhjemite sheet in the Archean dunite of the Seqi Ultramafic Complex, SW Greenland, consists of three distinct mineral zones dominated by (1) talc, (2) anthophyllite, and (3) phlogopite. These zones supposedly resulted from a process of dissolution of olivine by silica rich fluid residual from the trondhjemite magma, with crystallization of secondary minerals along a compositional gradient in the fluid phase. A zircon crystal inclusion in a large (4 cm) olivine porphyroblast was dated in situ via LA-ICP-MS U–Pb isotope analysis, yielding a weighted mean 207Pb/206Pb age of 2963 ± 1 Ma, which coincides with granulite facies metamorphism and potential dehydration. Considering phase relations appropriate for the dunite composition, we deduced the talc forming conditions to be at temperatures of 600–650 °C and at a pressure below 1 GPa. This is supported by oxygen isotope data for talc, anthophyllite and phlogopite in the metasomatic zone, which suggests formation in the temperature range of 600–700 °C from fluids that had a δ18O of ~8‰ and a Δ’17O0.528 of about −40 ppm, i.e., from fluids that could have been derived from the late stage trondhjemite sheet. Full article
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Open AccessArticle
X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa
Minerals 2020, 10(1), 84; https://doi.org/10.3390/min10010084 - 20 Jan 2020
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Abstract
The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature [...] Read more.
The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
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Open AccessArticle
The In-Situ Quantification of Structural Radiation Damage in Zircon Using Laser-Induced Confocal Photoluminescence Spectroscopy
Minerals 2020, 10(1), 83; https://doi.org/10.3390/min10010083 - 20 Jan 2020
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Abstract
We present a new methodology for laser-induced steady-state photoluminescence (PL) spectroscopy of Dy3+ that aims at a direct quantification of the amorphous fraction fa present in zircon (ZrSiO4), which undergoes a transition from a crystalline to a metamict state [...] Read more.
We present a new methodology for laser-induced steady-state photoluminescence (PL) spectroscopy of Dy3+ that aims at a direct quantification of the amorphous fraction fa present in zircon (ZrSiO4), which undergoes a transition from a crystalline to a metamict state due to cumulative self-irradiation damage caused by the radioactive decay of substituted U and Th. Using state-of-the-art confocal spectrometers attached to optical microscopes, measurements may be performed non-destructively on the micrometre length-scale with the option to visualize radiation-damage patterns as revealed by hyperspectral PL maps. Zircon from the Ratnapura district (Sri Lanka, ~520 Ma), was used as reference material to substantiate the applicability of the proposed method. The accumulation of radiation damage in this material was investigated in detail and obtained fa values correlate with calculated α-doses in accordance to the direct impact model reported variously in the literature. The impact of chemically-induced, heterogeneous broadening of Raman and Dy3+ emission spectral bands is discussed on two examples from Mt. Malosa district, Malawi. A mean weighted U-Pb isotope age of 111 ± 1 Ma (pegmatitic-type) and a discordia age of 112 ± 1.6 Ma (hydrothermal-type) as obtained by LA-ICP-MS confirm their close genetic and temporal relationship. Studied zircon examples demonstrate that the amount of radiation damage present may have a substantial effect on the precision of LA-ICP-MS ages, but cannot be considered an exclusive cause for bias of obtained isotope ages. Full article
(This article belongs to the Special Issue Modern Luminescence Spectroscopy of Minerals)
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Open AccessArticle
Surface Subsidence Prognosis above an Underground Longwall Excavation and Based on 3D Point Cloud Analysis
Minerals 2020, 10(1), 82; https://doi.org/10.3390/min10010082 - 20 Jan 2020
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Abstract
Impacts of underground mining have been reduced by continuous environmental endeavors, scientific, and engineering research activities, whose main object is the behavior and control of the undermined rock mass and the subsequent surface subsidence. In the presented Velenje case of underground sublevel longwall [...] Read more.
Impacts of underground mining have been reduced by continuous environmental endeavors, scientific, and engineering research activities, whose main object is the behavior and control of the undermined rock mass and the subsequent surface subsidence. In the presented Velenje case of underground sublevel longwall mining where coal is being exploited both horizontal and vertical, backfilling processes and accompanying fracturing in the coal layer, and rock mass are causing uncontrolled subsidence of the surface above. 3D point clouds of the study were acquired in ten epochs and at excavation heights on the front were measured at the same epochs. By establishing a sectors layout in the observational area, smaller point clouds were obtained, to which planes were fitted and centroids of these planes then calculated. Centroid heights were analyzed with the FNSE model to estimate the time of consolidation and modified according to excavation parameters to determine total subsidence after a certain period. Proposed prognosis approaches for estimating consolidation of active subsidence and long term surface environmental protection measures have been proposed and presented. The C2C analysis of distances between acquired 3D point clouds was used for identification of surface subsidence, reclamation areas and sink holes, and for validation of feasibility and effectiveness of the proposed prognosis. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Minerals in 2019
Minerals 2020, 10(1), 81; https://doi.org/10.3390/min10010081 - 20 Jan 2020
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Abstract
The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...] Full article
Open AccessArticle
Geochemical and Sr-Nd-Pb-Hf Isotopic Characteristics of Muchen Pluton in Southeast China, Constrain the Petrogenesis of Alkaline A-Type Magma
Minerals 2020, 10(1), 80; https://doi.org/10.3390/min10010080 - 19 Jan 2020
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Abstract
We present comprehensive petrological, major-trace element, in situ zircon U-Pb dating and Sr-Nd-Pb isotopic data for Muchen granitoid (western Zhejiang Province, Southeast China), to constrain the petrogenesis of alkaline A-type granites and the geodynamic setting of Southeast China in the Early Cretaceous. The [...] Read more.
We present comprehensive petrological, major-trace element, in situ zircon U-Pb dating and Sr-Nd-Pb isotopic data for Muchen granitoid (western Zhejiang Province, Southeast China), to constrain the petrogenesis of alkaline A-type granites and the geodynamic setting of Southeast China in the Early Cretaceous. The Early Cretaceous Muchen quartz monzonite yielded zircon U-Pb crystallization ages of 111.3 ± 0.7 Ma and is metaluminous to weakly peraluminous with SiO2 contents ranging from 59 to 69 wt.%, and can be classified as alkaline A-type granitoid. The quartz monzonites have low (87Sr/86Sr)i values (0.7052 to 0.7061) and high εNd(t) values (−2.6 to −2.0), similar to nearby coeval mafic rocks that have been proposed to be derived from the enriched lithospheric mantle. The high Nb/Ta ratios (16.7 to 30.1, average 21.8) and low Nb/U ratios (as low as 3.5) indicate the involvement of slab-derived melt and fluids in this mantle. These geochemical properties of the Muchen quartz monzonites indicated that they might be from a phlogopite-bearing and rutile-rich subduction-modified subcontinental lithospheric mantle, and underwent strong fractional crystallization of olivine + orthopyroxene + plagioclase during magma ascent. The low Mg# values of these alkaline rocks (<30 mostly) may indicate a low-pressure source in a back-arc setting. The early Cretaceous alkaline granitoids in Southeast China are related to the continental back-arc setting caused by deep angle subduction of the paleo-Pacific plate. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Open AccessFeature PaperArticle
Effect of Graphite on Copper Bioleaching from Waste Printed Circuit Boards
Minerals 2020, 10(1), 79; https://doi.org/10.3390/min10010079 - 19 Jan 2020
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Abstract
The efficient extraction of copper as a valuable metal from waste printed circuit boards (WPCBs) is currently attracting growing interest. Here, we systematically investigated the impact of bacteria on the efficiency of copper leaching from WPCBs, and evaluated the effect of graphite on [...] Read more.
The efficient extraction of copper as a valuable metal from waste printed circuit boards (WPCBs) is currently attracting growing interest. Here, we systematically investigated the impact of bacteria on the efficiency of copper leaching from WPCBs, and evaluated the effect of graphite on bioleaching performance. The HQ0211 bacteria culture containing Acidithiobacillus ferrooxidans, Ferroplasma acidiphilum, and Leptospirillum ferriphilum enhanced Cu-leaching performance in either ferric sulfate and sulfuric acid leaching, so a final leaching of up to 76.2% was recorded after 5 days. With the addition of graphite, the percentage of copper leaching could be increased to 80.5%. Single-factor experiments confirmed the compatibility of graphite with the HQ0211 culture, and identified the optimal pulp density of WPCBs, the initial pH, and the graphite content to be 2% (w/v), 1.6, and 2.5 g/L, respectively. Full article
(This article belongs to the Special Issue The Processing of Alternative and Urban Ores)
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Open AccessArticle
Riesite, a New High Pressure Polymorph of TiO2 from the Ries Impact Structure
Minerals 2020, 10(1), 78; https://doi.org/10.3390/min10010078 - 18 Jan 2020
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Abstract
This paper describes riesite, a new high-pressure polymorph of TiO2 from the Ries impact structure, Germany. Riesite occurs in shock-induced melt veins within xenoliths of bedrock in suevite. It is structurally closely related to srilankite from which it differs by having two [...] Read more.
This paper describes riesite, a new high-pressure polymorph of TiO2 from the Ries impact structure, Germany. Riesite occurs in shock-induced melt veins within xenoliths of bedrock in suevite. It is structurally closely related to srilankite from which it differs by having two distinct cation sites rather than one and through its monoclinic symmetry. It is indicative that riesite forms only upon release from the shock state upon back transformation from akaogiite. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
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Open AccessArticle
Synchysite-(Ce) from Cinquevalli (Trento, Italy): Stacking Disorder and the Polytypism of (Ca,REE)-Fluorcarbonates
Minerals 2020, 10(1), 77; https://doi.org/10.3390/min10010077 - 18 Jan 2020
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Abstract
Synchysite-(Ce) at Cinquevalli occurs as fine needles intergrown with quartz in quartz-dikes and in association with altered K-feldspar and oxidized chalcopyrite as major constituents. Synchysite-(Ce) [Ca1.00(Ce0.43La0.26Nd0.17Y0.07Pr0.04Sm0.02Gd0.01)Σ=1.00 [...] Read more.
Synchysite-(Ce) at Cinquevalli occurs as fine needles intergrown with quartz in quartz-dikes and in association with altered K-feldspar and oxidized chalcopyrite as major constituents. Synchysite-(Ce) [Ca1.00(Ce0.43La0.26Nd0.17Y0.07Pr0.04Sm0.02Gd0.01)Σ=1.00(CO3)2(F0.58(OH)0.42)], shows an overgrowth rim of bastnäsite-(Ce) [(Ce0.34La0.25Nd0.17Pb0.07C a0.06Y0.06Pr0.04S m0.02Gd0.01)Σ=1.00C O3(F0.75(OH)0.25)]. Unit cell refinement of synchysite (C2/c) and bastnäsite (P62c) led to a = 12.272(4), b = 7.100(2), c = 18.640(5) Å, β = 102.71(5)°, and a = 7.085(1), c = 9.746(2) Å, respectively. Polysomatic faults are sporadic, but polytypic disorder is widespread. High resolution transmission electron microscopy images taken along [100] or ⟨130⟩ show an apparent order and the related diffraction patterns are streak-free. Conversely, along [010] or ⟨110⟩, a high density of stacking faults is observed and the related diffraction patterns show hhl rows with h ≠ 3n affected by streaks. No ordered domain larger than a few unit cells was detected. The stacking sequence of (Ca,REE)-fluorcarbonates can be compared with subfamily-B mica polytypes (2M2, 2O and 6H), which are characterized by n·60° (n = odd) rotations. Subfamily-A polytypes (1M, 2M1 and 3T), characterized by n·60° (n = even) rotations, should not be possible. Synchysite, characterized by ±60° rotations, can be likened to the 2M2 polytype. Full article
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Open AccessArticle
Zircon U–Pb Geochronology, Whole-Rock Geochemistry and Petrogenesis of Biotite Granites in the Gaudeanmus Area, Namibia
Minerals 2020, 10(1), 76; https://doi.org/10.3390/min10010076 - 17 Jan 2020
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Abstract
The Gaudeanmus area is located at the southern Central Zone of the Damara orogenic belt in south-western Africa. In this paper, we investigate the whole rock major and trace element compositions and Sr–Nd–Pb isotopic compositions of the biotite granite, and determine the age [...] Read more.
The Gaudeanmus area is located at the southern Central Zone of the Damara orogenic belt in south-western Africa. In this paper, we investigate the whole rock major and trace element compositions and Sr–Nd–Pb isotopic compositions of the biotite granite, and determine the age of the samples utilising U–Pb zircon dating methods. Our results provide an LA–collector inductively plasma mass spectrometer (ICP–MS) zircon U–Pb age for the biotite granite of 540 ± 4 Ma (i.e., earliest Cambrian). The biotite granites show the characteristics of metaluminous compositions belonging to high-K calc–alkaline to shoshonite series. The granites contain high alkali and rare earth elements (REE), are enriched in large-ion lithophile elements (Rb, K, Pb), and depleted in high field-strength elements (Nb, Ta, Ti). The REE patterns are characterised by enrichment of LREEs relative to HREEs and medium negative Eu anomalies in the chondrite-normalised REE diagram. These rocks have high initial 87Sr/86Sr ratios (0.71400–0.71768); low εNd(t) value (−12.0 to −7.1); Sm–Nd isotope crust model ages ranging from 1711 to 2235 Ma; and large variations in 206Pb/204Pb (18.0851–19.2757), 207Pb/204Pb (15.6258–15.7269), and 208Pb/204Pb ratios (38.7437–40.5607). Such geochemical signatures indicate that the biotite granite rocks derive mainly from partial melting of ancient crustal rocks resembling the local basement meta-sedimentary rocks. However, minor mantle-derived materials may have also been involved in the formation of these rocks. Combining with regional tectonic evolution, we consider that the biotite granite intrusions in the Gaudeanmus area formed in a transitional tectonic regime that went from compressional to extensional tectonics. Full article
(This article belongs to the Section Mineral Deposits)
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Open AccessArticle
Trace Element Distributions in the Zn-Pb (Mississippi Valley-Type) and Cu-Ag (Kupferschiefer) Sediment-Hosted Deposits in Poland
Minerals 2020, 10(1), 75; https://doi.org/10.3390/min10010075 - 17 Jan 2020
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Abstract
We applied geochemical (ICP-MS, WD-XRF, GFAAS, and AMA 254) and mineralogical (EPMA) studies of 137 samples to ore mineralization from Middle-Triassic sediment-hosted Zn-Pb (Mississippi Valley-type MVT) and Lower Zechstein sediment-hosted stratiform (SSC) Cu-Ag (Kupferschiefer-type) deposits in Poland. They contain a number of trace [...] Read more.
We applied geochemical (ICP-MS, WD-XRF, GFAAS, and AMA 254) and mineralogical (EPMA) studies of 137 samples to ore mineralization from Middle-Triassic sediment-hosted Zn-Pb (Mississippi Valley-type MVT) and Lower Zechstein sediment-hosted stratiform (SSC) Cu-Ag (Kupferschiefer-type) deposits in Poland. They contain a number of trace elements which are not recovered during the ore processing. Only Cu, Ag, Pb, Ni, Re, Se, Au, and PGE are extracted from Cu-Ag deposits while Zn and Pb are the only elements produced from Zn-Pb deposits. Zn-Pb deposits contain Cd, Ag, Ga, and Ba in slightly elevated concentrations and have potential to be mineral resources. This applies to a lesser extent to other trace elements (Bi, As, Hf, Tl, Sb, Se, and Re). However, only Cd and Ag show high enrichment factors indicative of potential for recovery. The bulk-rock analyses reveal strong correlations between Zn and Cd and Se, As and Mo, and weaker correlations between Ag and Cd, as well as Ga and Zn. Electron microprobe analyses of sphalerite revealed high concentrations of Cd (≤2.6 wt%) and Ag (≤3300 ppm). Zn-Pb deposits have fairly significant estimated resources of Ga and Sc (>1000 tons) and Cd (>10,000 tons). The Cu-Ag deposits have element signatures characterized by high values of Co, V, Ni, and Mo and much lower of Bi, As, Cd, Hg, Mo, Sb, and Tl. Bulk-rock analyses show strong correlations between Se and V; As and Co; Bi and Re; and weaker correlations between, for example, Cu and Mo; V, Ni, Ag and Mo; and Ni, V, and Co and Ni. The EPMA determinations reveal strong enrichments of Ag in Cu sulfides (geerite ≤ 10.1 wt %, chalcocite ≤ 6.28 wt %, bornite ≤ 3.29 wt %, djurleite ≤ 9080 ppm, yarrowite ≤ 6614 ppm, and digenite ≤ 3545 ppm). Silver minerals and alloys, as well as the native Ag and Au, were recorded in the Cu-Ag ores. Large resources of Co, V, and Ni (>100,000 tons) and Sc and Mo (>10,000 tons) are notable in Cu-Ag deposits. A number of trace elements, classified as critical for the economy of the European Union, including Ga and Ba (to a lesser extent Hf, Nb, and Sc) in Zn-Pb deposits, and Co and V in the Cu-Ag deposits, may eventually be recovered in the future from the studied deposits if proper ore-processing circuits and increasing demand are favorable. Full article
(This article belongs to the Special Issue Mineral Deposits of Central Europe)
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Open AccessArticle
Distribution Characteristics and Influencing Factors of Uranium Isotopes in Saline Lake Waters in the Northeast of Qaidam Basin
Minerals 2020, 10(1), 74; https://doi.org/10.3390/min10010074 - 17 Jan 2020
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Abstract
Four saline lakes in the northeast of Qaidam Basin were selected to explore the distribution characteristics and influencing factors of uranium isotopes in lake waters with high evaporation background. The 238U concentration and the activity ratios of 234U/238U ([ [...] Read more.
Four saline lakes in the northeast of Qaidam Basin were selected to explore the distribution characteristics and influencing factors of uranium isotopes in lake waters with high evaporation background. The 238U concentration and the activity ratios of 234U/238U ([234U/238U]AR) showed that there was no significant change in the same lake, but there was a certain degree of difference in the distribution between different lakes. We found that aqueous 238U concentration within a certain range increased with an increase in TDS (total dissolved solid) and salinity, as was also the case with pH. As in natural waters, the pH affects the speciation of 238U, but TDS and salinity affect the adsorption process of aqueous 238U. Further, the replenishment of water will also affect the uranium isotope concentration for lakes, but it is not the main influencing factor for saline lakes. Therefore, we suggest that pH is the dominant factor affecting changes in aqueous 238U concentration of the sampled saline lakes. The [234U/238U]AR in these saline lakes are closely related to the input water and the associated water–rock interactions involving sediments, atmosphere dust, and organic material, etc. during the evolution stage, metamorphous degree, and hydrochemistry of the saline lakes. Lake water samples collected in the maximum and minimum discharge water period, were used to evaluate the seasonal distribution characteristics of aqueous 238U, and we found that 238U concentration did not show an evident change with the seasons in these saline lakes. If the 238U concentration and [234U/238U]AR can remain consistent during a period of time, then the sediment ages and/or sedimentation rates could be determined by lake sediment and/or biogenic carbonate in future, thus allowing for the accurate reconstruction of the paleoclimate and paleoenvironment. Full article
(This article belongs to the Special Issue Mineral and Geochemical Composition of Lake Sediments)
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Open AccessArticle
The Petyayan-Vara Carbonatite-Hosted Rare Earth Deposit (Vuoriyarvi, NW Russia): Mineralogy and Geochemistry
Minerals 2020, 10(1), 73; https://doi.org/10.3390/min10010073 - 17 Jan 2020
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Abstract
The Vuoriyarvi Devonian carbonatite–ijolite–pyroxenite–olivinite complex comprises several carbonatite fields: Neske Vara, Tukhta-Vara, and Petyayan-Vara. The most common carbonatites in the Tukhta-Vara and Neske-Vara fields are calciocarbonatites, which host several P, Fe, Nb, and Ta deposits. This paper focuses on the Petyayan-Vara field, in [...] Read more.
The Vuoriyarvi Devonian carbonatite–ijolite–pyroxenite–olivinite complex comprises several carbonatite fields: Neske Vara, Tukhta-Vara, and Petyayan-Vara. The most common carbonatites in the Tukhta-Vara and Neske-Vara fields are calciocarbonatites, which host several P, Fe, Nb, and Ta deposits. This paper focuses on the Petyayan-Vara field, in which the primary magmatic carbonatites are magnesian. The least altered magnesiocarbonatites are composed of dolomite with burbankite and are rich in REE (up to 2.0 wt. %), Sr (up to 1.2 wt. %), and Ba (up to 0.8 wt. %). These carbonatites underwent several stages of metasomatism. Each metasomatic event produced a new rock type with specific mineralization. The introduction of K, Si, Al, Fe, Ti, and Nb by a F-rich fluid (or fluid-saturated melt) resulted in the formation of high-Ti magnesiocarbonatites and silicocarbonatites, composed of dolomite, microcline, Ti-rich phlogopite, and Fe–Ti oxides. Alteration by a phosphate–fluoride fluid caused the crystallization of apatite in the carbonatites. A sulfate-rich Ba–Sr–rare-earth elements (REE) fluid (probably brine-melt) promoted the massive precipitation of ancylite and baryte and, to a lesser extent, strontianite, bastnäsite, and synchysite. Varieties of carbonatite that contain the highest concentrations of REE are ancylite-dominant. The influence of sulfate-rich Ba-Sr-REE fluid on the apatite-bearing rocks resulted in the dissolution and reprecipitation of apatite in situ. The newly formed apatite generation is rich in HREE, Sr, and S. During late-stage transformations, breccias of magnesiocarbonatites with quartz-bastnäsite matrixes were formed. Simultaneously, strontianite, quartz, calcite, monazite, HREE-rich thorite, and Fe-hydroxides were deposited. Breccias with quartz-bastnäsite matrix are poorer in REE (up to 4.5 wt. % total REE) than the ancylite-dominant rocks (up to 11 wt. % total REE). Full article
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Open AccessArticle
Pore Structure and Fractal Characteristics of Different Shale Lithofacies in the Dalong Formation in the Western Area of the Lower Yangtze Platform
Minerals 2020, 10(1), 72; https://doi.org/10.3390/min10010072 - 16 Jan 2020
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Abstract
The purpose of this article was to quantitatively investigate the pore structure and fractal characteristics of different lithofacies in the upper Permian Dalong Formation marine shale. Shale samples in this study were collected from well GD1 in the Lower Yangtze region for mineral [...] Read more.
The purpose of this article was to quantitatively investigate the pore structure and fractal characteristics of different lithofacies in the upper Permian Dalong Formation marine shale. Shale samples in this study were collected from well GD1 in the Lower Yangtze region for mineral composition, X-ray diffraction (XRD), and nitrogen adsorption–desorption analysis, as well as broad-ion beam scanning electron microscopy (BIB-SEM) observation. Experimental results showed that the TOC (total organic carbon) content and vitrinite reflectance (Ro) of the investigated shale samples were in the ranges 1.18–6.45% and 1.15–1.29%, respectively, showing that the Dalong Formation shale was in the mature stage. XRD results showed that the Dalong Formation shale was dominated by quartz ranging from 38.4% to 54.3%, followed by clay minerals in the range 31.7–37.5%, along with carbonate minerals (calcite and dolomite), with an average value of 9.6%. Based on the mineral compositions of the studied samples, the Dalong Formation shale can be divided into two types of lithofacies, namely siliceous shale facies and clay–siliceous mixed shale facies. In siliceous shale facies, which were mainly composed of organic pores, the surface area (SA) and pore volume (PV) were in the range of 5.20–10.91 m2/g and 0.035–0.046 cm3/g, respectively. Meanwhile, the pore size distribution (PSD) and fractal dimensions were in the range 14.2–26.1 nm and 2.511–2.609, respectively. I/S (illite-smectite mixed clay) was positively correlated with SA, PV, and fractal dimensions, while illite had a negative relationship with SA, PV, and fractal dimensions. I/S had a strong catalytic effect on organic matter for hydrocarbon generation, which was beneficial to the development of organic micropores, so I/S was conducive to pore structure complexity and the increase in SA and PV, while illite easily filled organic pores, which was not beneficial to the improvement of pore space. In clay–siliceous mixed shale facies, which mainly develop inorganic pores such as intergranular pores, SA and PV were in the range of 6.71–11.38 m2/g and 0.030–0.041 cm3/g, respectively. Meanwhile, PSD and fractal dimensions were in the range of 14.3–18.9 nm and 2.563–2.619, respectively. Quartz and I/S showed weak positive correlations with SA, PV, and fractal dimensions. The various compact modes between quartz particles and the disorder of I/S were conducive to the complexity of pore structure and the improvement of SA and PV. The research findings can provide a reference for the optimization and evaluation of shale gas favorable area of the Lower Yangtze Platform. Full article
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Open AccessArticle
Compressional Behavior of Hydrous Orthoenstatite: Insight into the Nature of LVZ under Continental Plate
Minerals 2020, 10(1), 71; https://doi.org/10.3390/min10010071 - 16 Jan 2020
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Abstract
A suite of hydrous orthoenstatite crystals were synthesized at 5–7 GPa and 1100–1300 °C, corresponding to the mid upper mantle conditions in continental regions. The synthetic crystals presented a clear, inclusion-free, and euhedral form with a size range from 100 to a few [...] Read more.
A suite of hydrous orthoenstatite crystals were synthesized at 5–7 GPa and 1100–1300 °C, corresponding to the mid upper mantle conditions in continental regions. The synthetic crystals presented a clear, inclusion-free, and euhedral form with a size range from 100 to a few hundred microns. The Al- and water content of crystals were less than 2 wt. % and ranging from ~500 ppm to 1000 ppm, respectively, characterized by Raman and IR spectroscopy, electron microscopy, and SIMS. The analysis shows that the capability of water incorporation for this suite of hydrous orthoenstatite is correlated to the Al-content in the crystal structure. To understand how the detailed crystal structure reflects the influence of water and Al, single crystal X ray diffraction analysis was performed for this suite of hydrous orthoenstatite. By comparing the results obtained at ambient conditions, we find that for low-level of Al-content, <2 wt. %, the Al3+ cation tends to occupy one of tetrahedral sites (TB) only. Analysis of the X ray diffraction results under high pressure indicates that the elasticity of orthoenstatites is insensitive to the presence of low-level water and Al. We use this finding to evaluate the velocity profile at the mid upper mantle of continental regions to compare with seismic observation. The comparison indicates that the cause of the low velocity zone in continental regions originates from the geotherm profile rather than the effect of water on the elasticity of mantle phases. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
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Open AccessArticle
Algal Lipids as Biocollector for Recovery of Coal from Fine Coal Waste by Froth Flotation
Minerals 2020, 10(1), 70; https://doi.org/10.3390/min10010070 - 16 Jan 2020
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Abstract
Raw algal lipids (RALs) and their derivatives (fatty acid methyl esters; FAMEs) were investigated as biocollectors for the recovery of coal from ash-rich fine coal waste by froth flotation. Testing was done on fine coal discards from two South African sites—a high ash [...] Read more.
Raw algal lipids (RALs) and their derivatives (fatty acid methyl esters; FAMEs) were investigated as biocollectors for the recovery of coal from ash-rich fine coal waste by froth flotation. Testing was done on fine coal discards from two South African sites—a high ash (50%), high sulphur (5.7%) sample and a lower ash (26%), low sulphur (0.91%) sample. The yield and recovery of combustibles on using biocollectors was similar to, or better than, with oleic acid, a polar collector demonstrated as a good collector in previous research. The RALs and FAMEs reduced the ash and sulphur content of the combustible fraction of the high ash-high sulphur sample to between 23–28% and 1.9–3.3%, respectively. The chemical modification of RALs to FAMEs provided potential for improving the selectivity of the recovery of combustibles. It also resulted in a change of the optimum operating pH, with RALs yielding better results at the natural pH of the sample (pH 2.7), while FAMEs performed best at pH 7. Full article
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Open AccessArticle
Mineralogical and Geochemical Characteristics of Triassic Lithium-Rich K-Bentonite Deposits in Xiejiacao Section, South China
Minerals 2020, 10(1), 69; https://doi.org/10.3390/min10010069 - 16 Jan 2020
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Abstract
Widespread alteration in the Early–Middle Triassic volcanic ash of the Xiejiacao section, south China, has resulted in significant occurrences of lithium-rich K-bentonite deposits with economic potential. Detailed mineralogical and geochemical investigations of Li-rich K-bentonite deposits from the Xiejiacao section of Guangan city, South [...] Read more.
Widespread alteration in the Early–Middle Triassic volcanic ash of the Xiejiacao section, south China, has resulted in significant occurrences of lithium-rich K-bentonite deposits with economic potential. Detailed mineralogical and geochemical investigations of Li-rich K-bentonite deposits from the Xiejiacao section of Guangan city, South China, are presented here. The X-ray diffraction (XRD) data and major element chemistry indicates that the Li-rich K-bentonite deposits contain quartz, clay minerals, feldspar, calcite and dolomite, and the clay minerals are dominated by illite and ordered (R3) illite/smectite (I/S). The concentrations of major and trace elements in Li-rich K-bentonite deposits altered from volcanic ashes are most likely derived from felsic magmas, associated with intense volcanic arc activity. The composition of the clay components suggests that the Li-rich K-bentonite deposits are probably altered from the smectite during diagenesis, whereas smectite is mainly formed by submarine alterations of volcanic materials and subsequently the I/S derived from the volcanogenic smectite illitization. Moreover, accurate determination of the structure in I/S reveals that the temperatures reached by the sedimentary series are around 180 °C with a burial depth of ~6000 m. The widely distributed lithium-rich clay deposits strongly indicate widespread eruptions of volcanic ashes in the Early–Middle Triassic, which released huge amounts of volcanic ash. Lithium fixed in the illite and I/S is considered to have leached from the volcanogenic products by a mixed fluid source (i.e., meteoric, porewater and hydrothermal fluids). These Li-rich clay minerals in the marine basin contain economically extractable levels of metal and are a promising new target for lithium exploration. Full article
(This article belongs to the Special Issue Evolution of Li-rich Brines)
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Open AccessArticle
Lithium-Rich Claystone in the McDermitt Caldera, Nevada, USA: Geologic, Mineralogical, and Geochemical Characteristics and Possible Origin
Minerals 2020, 10(1), 68; https://doi.org/10.3390/min10010068 - 15 Jan 2020
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Abstract
Lithium deposits in tuffaceous sediments of the McDermitt caldera constitute possibly the world’s largest Li clay resource, yet their characteristics and origin are not established. The 40 × 25 km McDermitt caldera collapsed during the eruption of ~1000 km3 of a 16.4 [...] Read more.
Lithium deposits in tuffaceous sediments of the McDermitt caldera constitute possibly the world’s largest Li clay resource, yet their characteristics and origin are not established. The 40 × 25 km McDermitt caldera collapsed during the eruption of ~1000 km3 of a 16.4 Ma, zoned peralkaline to metaluminous tuff; minor caldera magmatism ceased by 16.1 Ma. About 200 m of sediments mostly composed of glass from regional pyroclastic eruptions accumulated in the caldera until about 15.7 Ma. Closed hydrologic system diagenesis (CHSD) altered the tuffaceous sediments to a consistent vertical mineral zonation of clay, analcime, K-feldspar, and albite. Entire sedimentary sections in the southern and western parts of the caldera basin have ≥1500 ppm Li. Lithium-rich intervals are dominantly claystone. The most thoroughly studied deposit is a laterally continuous, ~3000 ppm Li zone in the lower sedimentary section that also has high K, Rb, Mo, As, and Sb (and partly Mg and F). Lithium occurs as an illitic clay (tainiolite?). The overlying, upper sedimentary section averages <2000 ppm Li which resides in smectite (hectorite). A transitional zone has variably mixed smectite–illite clay and averages ~2000 ppm Li. An 40Ar/39Ar age of ~14.9 Ma on authigenic K-feldspar in the illite zone is ~1.2 Ma younger than the 16.1 Ma end of magmatism in the caldera, which mitigates against a simple hydrothermal origin. Closed hydrologic system diagenesis was essential to Li mineralization, but Li budget calculations suggest a source of Li in addition to the tuffaceous sediments is required. This additional source could be Li originally in highly enriched magma that entered the diagenetic system through either (1) Li in magma exsolved into a hydrous volatile phase during eruption. The Li-rich volatile phase coated glass shards or was trapped in pumice and was quickly leached by surface or groundwater upon deposition in the caldera. (2) Residual magma immediately following ash-flow eruption and caldera collapse generated Li-rich hydrothermal fluids that mixed with meteoric water in the closed caldera basin, generating a hybrid diagenetic fluid. The hydrothermal fluid and hybrid diagenetic fluids would have existed only during initial basin sedimentation between about 16.4 and 16.1 Ma. Full article
(This article belongs to the Special Issue Evolution of Li-rich Brines)
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Open AccessArticle
The Bridgmanite–Akimotoite–Majorite Triple Point Determined in Large Volume Press and Laser-Heated Diamond Anvil Cell
Minerals 2020, 10(1), 67; https://doi.org/10.3390/min10010067 - 15 Jan 2020
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Abstract
The bridgmanite–akimotoite–majorite (Bm–Ak–Mj or BAM) triple point in MgSiO3 has been measured in large-volume press (LVP; COMPRES 8/3 assembly) and laser-heated diamond anvil cell (LHDAC). For the LVP data, we calculated pressures from the calibration provided for the assembly. For the LHDAC [...] Read more.
The bridgmanite–akimotoite–majorite (Bm–Ak–Mj or BAM) triple point in MgSiO3 has been measured in large-volume press (LVP; COMPRES 8/3 assembly) and laser-heated diamond anvil cell (LHDAC). For the LVP data, we calculated pressures from the calibration provided for the assembly. For the LHDAC data, we conducted in situ determination of pressure at high temperature using the Pt scale at synchrotron. The measured temperatures of the triple point are in good agreement between LVP and LHDAC at 1990–2000 K. However, the pressure for the triple point determined from the LVP is 3.9 ± 0.6 GPa lower than that from the LHDAC dataset. The BAM triple point determined through these experiments will provide an important reference point in the pressure–temperature space for future high-pressure experiments and will allow mineral physicists to compare the pressure–temperature conditions measured in these two different experimental methods. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
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Open AccessArticle
Novel Application of Mineral By-Products Obtained from the Combustion of Bituminous Coal–Fly Ash in Chemical Engineering
Minerals 2020, 10(1), 66; https://doi.org/10.3390/min10010066 - 15 Jan 2020
Viewed by 135
Abstract
The aim of this work was the chemical modification of mineral by-products obtained from the combustion of bituminous coal (FA) treated with hydrogen peroxide (30%), used as an adsorbent for the removal of Cr(III) and Cd(II) ions and crystal violet (CV) from a [...] Read more.
The aim of this work was the chemical modification of mineral by-products obtained from the combustion of bituminous coal (FA) treated with hydrogen peroxide (30%), used as an adsorbent for the removal of Cr(III) and Cd(II) ions and crystal violet (CV) from a mixture of heavy metal and organic dye in a solution containing either Cr(III)–CV or Cd(II)–CV. Fourier transform infrared (FT-IR), thermogravimetric analysis (TG), scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analyses suggested that the mechanism of Cr(III)–CV or Cd(II)–CV sorption onto FA–H2O2 includes ion-exchange and surface adsorption processes. The effect of pH on the adsorption equilibrium was studied. The maximum adsorption was found for pH values of 9. The values of the reduced chi-square test (χ2/degree of freedom (DoF)) and the determination coefficient R2 obtained for the sorbate of the considered isotherms were compared. Studies of equilibrium in a bi-component system by means of the extended Langmuir (EL), extended Langmuir–Freundlich (ELF), and Jain–Snoeyink (JS) models were conducted. The estimation of parameters of sorption isotherms in a bi-component system, either Cr(III)–CV or Cd(II)–CV, showed that the best-fitting calculated values of experimental data for both sorbates were obtained with the JS model (Cr(III) or CV) and the EL model (Cd(II) or CV). The maximum monolayer adsorption capacities of FA–H2O2 were found to be 775, 570 and 433 mg·g−1 for Cr, Cd and CV, respectively. Purification water containing direct Cr(III) or Cd(II) ions and CV was made with 90%, 98% and 80% efficiency, respectively, after 1.5 h. It was found that the chemical enhancement of FA from coal combustion by H2O2 treatment yields an effective and economically feasible material in chemical engineering for the treatment of effluents containing basic dyes and Cr(III) and Cd(II) ions. Full article
(This article belongs to the Special Issue Application of Mineral-Based Amendments)
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Open AccessArticle
Bio-Precipitation of Carbonate and Phosphate Minerals Induced by the Bacterium Citrobacter freundii ZW123 in an Anaerobic Environment
Minerals 2020, 10(1), 65; https://doi.org/10.3390/min10010065 - 13 Jan 2020
Viewed by 219
Abstract
In this study, a facultative anaerobic strain isolated from marine sediments and identified as Citrobacter freundii, was used to induce the precipitation of carbonate and phosphate minerals in the laboratory under anaerobic conditions. This is the first time that the ability of C. [...] Read more.
In this study, a facultative anaerobic strain isolated from marine sediments and identified as Citrobacter freundii, was used to induce the precipitation of carbonate and phosphate minerals in the laboratory under anaerobic conditions. This is the first time that the ability of C. freundii ZW123 to precipitate carbonate and phosphate minerals has been demonstrated. During the experiments, carbonic anhydrase, alkaline phosphatase and ammonium released by the bacteria not only promoted an increase in pH, but also drove the supersaturation and precipitation of carbonate and phosphate minerals. The predominant bio-mediated minerals precipitated at various Mg/Ca molar ratios were calcite, vaterite, Mg-rich calcite, monohydrocalcite and struvite. A preferred orientation towards struvite was observed. Scanning transmission electron microscopy (STEM) and elemental mapping showed the distribution of magnesium and calcium elements within Mg-rich calcite. Many organic functional groups, including C=O, C–O–C and C–O, were detected within the biominerals, and these functional groups were also identified in the associated extracellular polymeric substances (EPS). Fifteen kinds of amino acid were detected in the biotic minerals, almost identical to those of the EPS, indicating a close relationship between EPS and biominerals. Most amino acids are negatively charged and able to adsorb cations, providing an oversaturated microenvironment to facilitate mineral nucleation. The X-ray photoelectron spectroscopy (XPS) spectrum of struvite shows the presence of organic functional groups on the mineral surface, suggesting a role of the microorganism in struvite precipitation. The ZW123 bacteria provided carbon and nitrogen for the formation of the biotic minerals through their metabolism, which further emphasizes the close relationship between biominerals and the microorganisms. Thermal studies showed the enhanced thermal stability of biotic minerals, perhaps due to the participation of the bacteria ZW123. The presence of amino acids such as Asp and Glu may explain the high magnesium content of some calcites. Molecular dynamics simulations demonstrated that the morphological change and preferred orientation were likely caused by selective adsorption of EPS onto the various struvite crystal surfaces. Thus, this study shows the significant role played by C. freundii ZW123 in the bioprecipitation of carbonate and phosphate minerals and provides some insights into the processes involved. Full article
(This article belongs to the Special Issue Bio-Transformation and Mineralization Induced by Microorganisms)
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Open AccessArticle
Fluid Inclusion Characteristics of the Kışladağ Porphyry Au Deposit, Western Turkey
Minerals 2020, 10(1), 64; https://doi.org/10.3390/min10010064 - 13 Jan 2020
Viewed by 177
Abstract
The deposit occurs in a mid-Miocene monzonite magmatic complex represented by three different intrusions, namely Intrusion 1 (INT#1), Intrusion 2 (INT#2, INT #2A), and Intrusion 3 (INT#3). Gold mineralization is hosted in all intrusions, but INT#1 is the best mineralized body followed by [...] Read more.
The deposit occurs in a mid-Miocene monzonite magmatic complex represented by three different intrusions, namely Intrusion 1 (INT#1), Intrusion 2 (INT#2, INT #2A), and Intrusion 3 (INT#3). Gold mineralization is hosted in all intrusions, but INT#1 is the best mineralized body followed by INT#2. SEM-CL imaging has identified two different veins (V1 and V2) and four distinct generations of quartz formation in the different intrusions. These are: (i) CL-light gray, mosaic-equigranular quartz (Q1), (ii) CL-gray or CL-bright quartz (Q2) that dissolved and was overgrown on Q1, (iii) CL-dark and CL-gray growth zoned quartz (Q3), and (iv) CL-dark or CL-gray micro-fracture quartz fillings (Q4). Fluid inclusion studies show that the gold-hosted early phase Q1 quartz of V1 and V2 veins in INT#1 and INT#2 was precipitated at high temperatures (between 424 and 594 °C). The coexisting and similar ranges of Th values of vapor-rich (low salinity, from 1% to 7% NaCl equiv.) and halite-bearing (high salinity: >30% NaCl) fluid inclusions in Q1 indicates that the magmatic fluid had separated into vapor and high salinity liquid along the appropriate isotherm. Fluid inclusions in Q2 quartz in INT#1 and INT#2 were trapped at lower temperatures between 303 and 380 °C and had lower salinities between 3% and 20% NaCl equiv. The zoned Q3 quartz accompanied by pyrite in V2 veins of both INT#2 and INT#3 precipitated at temperatures between 310 and 373 °C with a salinity range from 5.4% to 10% NaCl eq. The latest generation of fracture filling Q4 quartz, cuts the earlier generations with fluid inclusion Th temperature range from 257 to 333 °C and salinity range from 3% to 12.5% NaCl equiv. The low salinity and low formation temperature of Q4 may be due to the mixing of meteoric water with the hydrothermal system, or late-stage epithermal overprinting. The separation of the magmatic fluid into vapor and aqueous saline pairs in the Q1 quartz of the V1 vein of the INT#1 and INT#2 and CO2-poor fluids indicates the shallow formation of the Kışladağ porphyry gold deposit. Full article
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Open AccessArticle
Using Microstructures and Composition to Decipher the Alterations of Rodent Teeth in Modern Regurgitation Pellets—A Good News-Bad News Story
Minerals 2020, 10(1), 63; https://doi.org/10.3390/min10010063 - 12 Jan 2020
Viewed by 212
Abstract
Rodent accumulations are widely used for palaeoenvironmental reconstructions. But these accumulations are created through the activity of predators (carnivorous mammals, birds of prey), the predation and digestion of which modify the preservation of bones and teeth. The microstructures of dentine and enamel, as [...] Read more.
Rodent accumulations are widely used for palaeoenvironmental reconstructions. But these accumulations are created through the activity of predators (carnivorous mammals, birds of prey), the predation and digestion of which modify the preservation of bones and teeth. The microstructures of dentine and enamel, as well as the mineralogy and composition of non-digested and digested Rodent teeth extracted from modern regurgitation pellets collected at Olduvai (Tanzania) from a bird of prey (Bubo sp.) are compared. Scanning electron microscopy (SEM), Electron Probe Micro Analysis (EPMA) and Raman spectrometry were used. The modifications induced by the digestion process are variable and depend on the tissue (enamel, dentine), tooth (incisor, molar) and the predator. For a given tissue of a tooth, the estimation of the intensity of the alteration varies according to the selected criteria. To classify the digested teeth in categories based on a single parameter to reconstruct environment is still subjective, even for modern accumulations. Moreover, to identify the interplay of diverse parameters to avoid biases in reconstructions is difficult. Full article
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Open AccessArticle
An Automated Method to Generate and Evaluate Geochemical Tectonic Discrimination Diagrams Based on Topological Theory
Minerals 2020, 10(1), 62; https://doi.org/10.3390/min10010062 - 10 Jan 2020
Viewed by 195
Abstract
Discrimination diagrams can be used to distinguish different tectonic settings of igneous rocks. To improve the quality and efficiency of the design of discrimination diagrams, an automatic design and assessment method for discrimination diagrams is proposed based on topology theory. The method is [...] Read more.
Discrimination diagrams can be used to distinguish different tectonic settings of igneous rocks. To improve the quality and efficiency of the design of discrimination diagrams, an automatic design and assessment method for discrimination diagrams is proposed based on topology theory. The method is aimed at programming the traditional process of discrimination diagram design, enabling computers to simulate the visual discrimination process. It thus automatically designs tectonic setting discrimination diagrams by investigating all possible combinations of geochemical elements. In the experiment, analyses of 3803 gabbro samples were collected from three tectonic settings, including island arc, ocean island, and mid-oceanic ridge. Using the proposed method, we found thousands of discrimination diagrams with fields overlapping less than 10%. By analyzing these diagrams, the most critical elements (or element ratio pairs) are identified. Based on the result, the feasibility of using gabbroic rocks to discriminate between tectonic settings is illustrated and four representative discrimination diagrams, including the La/Y–Nb/Ba diagram, Nb/Sc–Sc/Ba diagram, Ba/Nb–Ba/Sc diagram, and La/Na2O–Nb/Ba diagram, are recommended for use. This research supports the view that gabbroic rocks can also be used to discriminate between different tectonic settings. The method could also be applied to other rock types. Full article
(This article belongs to the Section Mineral Deposits)
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Open AccessFeature PaperArticle
Multivariate Statistical Analysis of Trace Elements in Pyrite: Prediction, Bias and Artefacts in Defining Mineral Signatures
Minerals 2020, 10(1), 61; https://doi.org/10.3390/min10010061 - 10 Jan 2020
Viewed by 368
Abstract
Pyrite is the most common sulphide in a wide range of ore deposits and well known to host numerous trace elements, with implications for recovery of valuable metals and for generation of clean concentrates. Trace element signatures of pyrite are also widely used [...] Read more.
Pyrite is the most common sulphide in a wide range of ore deposits and well known to host numerous trace elements, with implications for recovery of valuable metals and for generation of clean concentrates. Trace element signatures of pyrite are also widely used to understand ore-forming processes. Pyrite is an important component of the Olympic Dam Cu–U–Au–Ag orebody, South Australia. Using a multivariate statistical approach applied to a large trace element dataset derived from analysis of random pyrite grains, trace element signatures in Olympic Dam pyrite are assessed. Pyrite is characterised by: (i) a Ag–Bi–Pb signature predicting inclusions of tellurides (as PC1); and (ii) highly variable Co–Ni ratios likely representing an oscillatory zonation pattern in pyrite (as PC2). Pyrite is a major host for As, Co and probably also Ni. These three elements do not correlate well at the grain-scale, indicating high variability in zonation patterns. Arsenic is not, however, a good predictor for invisible Au at Olympic Dam. Most pyrites contain only negligible Au, suggesting that invisible gold in pyrite is not commonplace within the deposit. A minority of pyrite grains analysed do, however, contain Au which correlates with Ag, Bi and Te. The results are interpreted to reflect not only primary patterns but also the effects of multi-stage overprinting, including cycles of partial replacement and recrystallisation. The latter may have caused element release from the pyrite lattice and entrapment as mineral inclusions, as widely observed for other ore and gangue minerals within the deposit. Results also show the critical impact on predictive interpretations made from statistical analysis of large datasets containing a large percentage of left-censored values (i.e., those falling below the minimum limits of detection). The treatment of such values in large datasets is critical as the number of these values impacts on the cluster results. Trimming of datasets to eliminate artefacts introduced by left-censored data should be performed with caution lest bias be unintentionally introduced. The practice may, however, reveal meaningful correlations that might be diluted using the complete dataset. Full article
(This article belongs to the Special Issue Feature Papers in Mineral Geochemistry and Geochronology 2019)
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Open AccessArticle
Effects of Fine Minerals on Pulp Rheology and the Flotation of Diaspore and Pyrite Mixed Ores
Minerals 2020, 10(1), 60; https://doi.org/10.3390/min10010060 - 09 Jan 2020
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Abstract
In this study, the effects of four fine minerals, which were fine diaspore (FDIA), kaolinite, illite, and pyrophyllite (D50 is about 4.55 μm, D80 is about 10.78 μm), on the pulp rheology of the diaspore and pyrite mixed ores (D50 [...] Read more.
In this study, the effects of four fine minerals, which were fine diaspore (FDIA), kaolinite, illite, and pyrophyllite (D50 is about 4.55 μm, D80 is about 10.78 μm), on the pulp rheology of the diaspore and pyrite mixed ores (D50 is about 120.53 μm, D80 is about 187.36 μm) and the recovery of pyrite were investigated through flotation tests, pulp rheology measurements, and sedimentation tests. It was found that fine minerals could change the pulp rheology and affect the pyrite recovery. The apparent viscosity of the mixed ores slurry increased with the addition of FDIA, kaolinite, and illite and the pyrite recovery decreased in varying degrees. When the addition was 15 wt.%, the recovery of pyrite decreased from 92.3% to 60.8%, 81.4%, and 84.7%, respectively. The addition of pyrophyllite had a significant deteriorating effect on flotation. When the addition of pyrophyllite was 5 wt.%, the pyrite recovery was reduced to 49.2%, and when the addition was further increased to 15 wt.%, the pyrite recovery reduced to 28.5%. However, the effect of pyrophyllite addition on the pulp rheology of the mixed ore was not remarkable. Pyrophyllite affected pyrite recovery not only by affecting the rheological behavior of the pulp, but also because pyrophyllite was adsorbed on the surface of pyrite and diaspore, producing hetero-aggregation, which made it difficult for the pyrite particles to collide with the bubbles effectively. This was the main reason for the reduction of pyrite recovery. Generally, the order in which the reduction of pyrite recovery was affected by the additions of fine minerals was pyrophyllite > FDIA > kaolinite > illite. Full article
(This article belongs to the Section Mineral Processing and Metallurgy)
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Open AccessArticle
Ab Initio Thermoelasticity of Liquid Iron-Nickel-Light Element Alloys
Minerals 2020, 10(1), 59; https://doi.org/10.3390/min10010059 - 09 Jan 2020
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Abstract
The earth’s core is thought to be composed of Fe-Ni alloy including substantially large amounts of light elements. Although oxygen, silicon, carbon, nitrogen, sulfur, and hydrogen have been proposed as candidates for the light elements, little is known about the amount and the [...] Read more.
The earth’s core is thought to be composed of Fe-Ni alloy including substantially large amounts of light elements. Although oxygen, silicon, carbon, nitrogen, sulfur, and hydrogen have been proposed as candidates for the light elements, little is known about the amount and the species so far, primarily because of the difficulties in measurements of liquid properties under the outer core pressure and temperature condition. Here, we carry out massive ab initio computations of liquid Fe-Ni-light element alloys with various compositions under the whole outer core P, T condition in order to quantitatively evaluate their thermoelasticity. Calculated results indicate that Si and S have larger effects on the density of liquid iron than O and H, but the seismological reference values of the outer core can be reproduced simultaneously by any light elements except for C. In order to place further constraints on the outer core chemistry, other information, in particular melting phase relations of iron light elements alloys at the inner core-outer core boundary, are necessary. The optimized best-fit compositions demonstrate that the major element composition of the bulk earth is expected to be CI chondritic for the Si-rich core with the pyrolytic mantle or for the Si-poor core and the (Mg,Fe)SiO3-dominant mantle. But the H-rich core likely causes a distinct Fe depletion for the bulk Earth composition. Full article
(This article belongs to the Special Issue Mineral Physics—In Memory of Orson Anderson)
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Open AccessArticle
The Effect of Fly Ash Microspheres on the Pore Structure of Concrete
Minerals 2020, 10(1), 58; https://doi.org/10.3390/min10010058 - 09 Jan 2020
Viewed by 231
Abstract
The fly ash microspheres (FAMs) formed during the mineral transformation stage in coal combustion are hollow spherical particles with a density less than water. This paper presents the results of X-ray micro-computed tomography and an automatic image analysis system of the porosity in [...] Read more.
The fly ash microspheres (FAMs) formed during the mineral transformation stage in coal combustion are hollow spherical particles with a density less than water. This paper presents the results of X-ray micro-computed tomography and an automatic image analysis system of the porosity in the structure of hardened concrete with microspheres. Concrete mixtures with ordinary Portland cement and two substitution rates of cement by microspheres—5% and 10%—are investigated. For all considered mixes, a constant water/binder ratio (w/b) equal to 0.50 was used. The distribution of the air voids and the compressive strength of the concrete were tested after 28 days. With the increasing mass of cement replacement by FAMs, the compressive strength decreases after 28 days. The total volume of the air voids in hardened concrete with fly ash microspheres tested by X-ray varies from 5.1% to 7.4%. The closed pores constitute more than 80% of the total content of air pores. The study proves that the use of microspheres grains with specific dimensions has a significant impact on concrete porosity. Their application in concrete technology can be an alternative aeration solution for fresh concrete mixes and an effective method for utilization. Full article
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Open AccessEditorial
Introduction to the Special Issue “Role of Magmatic Activity in the Generation of Ore Deposits”
Minerals 2020, 10(1), 57; https://doi.org/10.3390/min10010057 - 09 Jan 2020
Viewed by 183
Abstract
This Special Issue presents eight original contributions concerning ore deposits in China, Russia, and Chile [...] Full article
(This article belongs to the Special Issue Role of Magmatic Activity in Generation of Ore Deposits)
Open AccessArticle
Tectonic History of the South Tannuol Fault Zone (Tuva Region of the Northern Central Asian Orogenic Belt, Russia): Constraints from Multi-Method Geochronology
Minerals 2020, 10(1), 56; https://doi.org/10.3390/min10010056 - 09 Jan 2020
Viewed by 230
Abstract
In this study, we present zircon U/Pb, plagioclase and K-feldspar 40Ar/39Ar and apatite fission track (AFT) data along the South Tannuol Fault Zone (STFZ). Integrating geochronology and multi-method thermochronology places constraints on the formation and subsequent reactivation of the STFZ. [...] Read more.
In this study, we present zircon U/Pb, plagioclase and K-feldspar 40Ar/39Ar and apatite fission track (AFT) data along the South Tannuol Fault Zone (STFZ). Integrating geochronology and multi-method thermochronology places constraints on the formation and subsequent reactivation of the STFZ. Cambrian (~510 Ma) zircon U/Pb ages obtained for felsic volcanic rocks date the final stage of STFZ basement formation. Ordovician (~460–450 Ma) zircon U/Pb ages were obtained for felsic rocks along the structure, dating their emplacement and marking post-formational local magmatic activity along the STFZ. 40Ar/39Ar stepwise heating plateau-ages (~410–400 Ma, ~365 and ~340 Ma) reveal Early Devonian and Late Devonian–Mississippian intrusion and/or post-magmatic cooling episodes of mafic rocks in the basement. Permian (~290 Ma) zircon U/Pb age of mafic rocks documents for the first time Permian magmatism in the study area creating prerequisites for revising the spread of Permian large igneous provinces of Central Asia. The AFT dating and Thermal history modeling based on the AFT data reveals two intracontinental tectonic reactivation episodes of the STFZ: (1) a period of Cretaceous–Eocene (~100–40 Ma) reactivation and (2) the late Neogene (from ~10 Ma onwards) impulse after a period of tectonic stability during the Eocene–Miocene (~40–10 Ma). Full article
(This article belongs to the Special Issue Dating Deep-Seated Tectonic Activities with Minerals)
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