Next Issue
Previous Issue

Table of Contents

Minerals, Volume 9, Issue 6 (June 2019)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story (view full-size image) A multi-approach study of tufa microbialites offers an explanation for mineralization intensities [...] Read more.
View options order results:
result details:
Displaying articles 1-57
Export citation of selected articles as:
Open AccessArticle
Elucidating the Effects of Hydrothermal Alteration on Seismic Reflectivity in the Footwall of the Lalor Volcanogenic Massive Sulfide Deposit, Snow Lake, Manitoba, Canada
Minerals 2019, 9(6), 384; https://doi.org/10.3390/min9060384
Received: 2 May 2019 / Revised: 13 June 2019 / Accepted: 19 June 2019 / Published: 25 June 2019
Viewed by 319 | PDF Full-text (5564 KB) | HTML Full-text | XML Full-text
Abstract
The integrated analysis of seismic rock properties, lithogeochemical data, and mineral compositional data, estimated via scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), provides insight into the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive sulfide (VMS) [...] Read more.
The integrated analysis of seismic rock properties, lithogeochemical data, and mineral compositional data, estimated via scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), provides insight into the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive sulfide (VMS) deposit, Manitoba, Canada. The effects of hydrothermal alteration on variations in acoustic impedance are secondary in magnitude and superimposed on the dominant acoustic impedance contrast between felsic and mafic volcanic protoliths. This secondary effect is due to an increase in P-wave velocity with increasing intensity of hydrothermal alteration, as measured by the Ishikawa and Carbonate-Chlorite-Pyrite alteration indices. Mixture modeling of the seismic rock properties and mineral percentages suggests that the increase in seismic velocity is due to an increase in abundance of cordierite, which is one of the diagnostic aluminum silicates for hydrothermally-altered volcanic rocks metamorphosed in the upper almandine amphibolite facies. The synthetic seismic data of a simple VMS model consisting of mafic-felsic host rock contacts, a sulfide ore lens, and a discordant hydrothermal conduit, consisting of the amphibolite-facies mineral assemblage (600 °C, 6 kbar) encountered at Lalor, show enhanced seismic reflections at conduit-host rock contacts, in comparison to its greenschist facies equivalent (350 °C, 2.5 kbar). This zone of enhanced seismic reflectivity in the footwall of the massive sulfide ore zone is also recognized on the Lalor seismic data suggesting that high-grade terrains hosting VMS deposits possess enhanced potential for the seismic detection of their footwall hydrothermal alteration zones. Full article
(This article belongs to the Special Issue Seismic Methods in Mineral Exploration)
Figures

Figure 1

Open AccessArticle
Typomorphic Characteristics of Pyrites from the Shuangwang Gold Deposit, Shaanxi, China: Index to Deep Ore Exploration
Minerals 2019, 9(6), 383; https://doi.org/10.3390/min9060383
Received: 23 May 2019 / Revised: 20 June 2019 / Accepted: 21 June 2019 / Published: 25 June 2019
Viewed by 262 | PDF Full-text (7621 KB) | HTML Full-text | XML Full-text
Abstract
The large Shuangwang gold deposit (>80 t gold) is located in the Western Qinling Orogen (WQO) of central China. It is an orogenic-type gold deposit hosted in an NW-extending breccia belt in the Devonian Xinghongpu Formation. Gold mineralization of the Shuangwang deposit is [...] Read more.
The large Shuangwang gold deposit (>80 t gold) is located in the Western Qinling Orogen (WQO) of central China. It is an orogenic-type gold deposit hosted in an NW-extending breccia belt in the Devonian Xinghongpu Formation. Gold mineralization of the Shuangwang deposit is featured by hydrothermal breccia ores with strata fragments cemented by hydrothermal minerals dominated by ankerite, quartz, and pyrite with minor amounts of calcite and albite. Pyrite is the major gold-hosting sulfide and the most abundant ore mineral. Crystal habits, thermoelectricity, and trace-element composition of pyrites from the main ore-forming stage of the Shuangwang gold deposit were studied by microbinocular, BHTE-06 thermoelectric coefficient measuring instrument, and high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). Spatial distribution of the above data for pyrites was delineated by contour maps of morphology index, P-type frequency, and primary halo elements (e.g., supraore halo elements Ba and Sb; near-ore halo elements Pb, Zn, and Cu; and subore halo elements Co, Mo, and Bi). Based on the above results, four target areas (areas between prospecting lines 0 and 1, between lines 14 and 18 below orebody KT9; areas between prospecting lines 30 and 34, between lines 44 and 46 below orebody KT8) were put forward for deep gold exploration in the future. These targets are consistent with the depth extrapolation of proven gold orebodies, indicating the practicality of typomorphic characterization of pyrites as vector to deep/concealed gold orebodies. The effectiveness of the pyrite typomorphic parameter for deep gold prediction seems to be chemical composition, crystal habits, and then thermoelectricity. Full article
Figures

Figure 1

Open AccessArticle
Geochemistry of Magmatic and Xenocrystic Spinel in the No.30 Kimberlite Pipe (Liaoning Province, North China Craton): Constraints on Diamond Potential
Minerals 2019, 9(6), 382; https://doi.org/10.3390/min9060382
Received: 29 April 2019 / Revised: 22 June 2019 / Accepted: 23 June 2019 / Published: 24 June 2019
Viewed by 197 | PDF Full-text (3220 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
There are two genetic types of spinel (magmatic spinel crystallizing directly from kimberlite magma and xenocrystic spinel derived from mantle xenoliths) in the No.30 kimberlite pipe (Liaoning Province, North China Craton). Their geochemistry is investigated to reveal processes of diamond capture and resorption [...] Read more.
There are two genetic types of spinel (magmatic spinel crystallizing directly from kimberlite magma and xenocrystic spinel derived from mantle xenoliths) in the No.30 kimberlite pipe (Liaoning Province, North China Craton). Their geochemistry is investigated to reveal processes of diamond capture and resorption during kimberlite magmatism to constrain the diamond potential. Magmatic spinels are mostly euhedral to subhedral, 20 to 60 µm in size, and have compositional zones: the cores are classified as chromite with high Cr and Mg contents, and the rims are classified as magnetite with low Cr and high ferric Fe. The compositional trends suggest that magmatic spinel and olivine phenocrysts are crystallized contemporaneously during the early stages of kimberlite crystallization. During this period, temperature (T) and oxygen fugacity (fO2) values calculated at an assumed pressure of 1 GPa are in the range of 994–1274 °C and 1.6–2.4 log fO2 units below the nickel-nickel oxide (NNO) buffer, respectively. The high values of fO2 suggest heavy diamond resorption during kimberlite magmatism. Estimated temperatures of xenocrystic spinel range from 828 to 1394 °C, and their distributions indicate that only a small proportion of xenocrystic spinels are derived from the diamond stabilization field, which suggests a low potential of diamond capture. The low diamond capture and heavy diamond resorption during kimberlite magmatism contributed to the low diamond grade of the No.30 kimberlite. Full article
Figures

Figure 1

Open AccessArticle
Mineralogical Analysis of Mortars in the Walls of Ávila (Spain) and Its Surroundings
Minerals 2019, 9(6), 381; https://doi.org/10.3390/min9060381
Received: 22 April 2019 / Revised: 18 June 2019 / Accepted: 22 June 2019 / Published: 24 June 2019
Viewed by 191 | PDF Full-text (12511 KB) | HTML Full-text | XML Full-text
Abstract
The present article evaluated the mineralogical composition of 85 mortar samples from some emblematic monuments of Ávila city (Spain), which were collected during the restoration of the monuments. The aim of this article is to try to extract the relationship between the composition [...] Read more.
The present article evaluated the mineralogical composition of 85 mortar samples from some emblematic monuments of Ávila city (Spain), which were collected during the restoration of the monuments. The aim of this article is to try to extract the relationship between the composition and the origin of the raw materials, as well as to identify possible alterations in the samples. The study of the samples was carried out using visual and petrographic techniques such as stereoscopic microscope, XRD, and SEM/EDX analysis. The main components of the mortars were calcite, feldspar and quartz, although small amounts of phyllosilicates were also identified. The minerals of the mortars came from the surroundings of the city, and some of the samples presented evident alteration of the original materials due to humidity, salt concentration, and biological weathering, possibly inducted by unfortunate effects of the restoration. Finally, a study of the salts present in some mortars showed that most samples display contamination of soluble salts such as halite, thenardite, hexaedrite, and carnalite. This investigation offers fresh insight into historic building activity and related techniques, and should provide knowledge useful for restoration and conservation processes. Full article
Figures

Figure 1

Open AccessArticle
Biotic–Abiotic Influences on Modern Ca–Si-Rich Hydrothermal Spring Mounds of the Pastos Grandes Volcanic Caldera (Bolivia)
Minerals 2019, 9(6), 380; https://doi.org/10.3390/min9060380
Received: 29 April 2019 / Revised: 11 June 2019 / Accepted: 21 June 2019 / Published: 23 June 2019
Viewed by 285 | PDF Full-text (32209 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The lacustrine-to-palustrine Pastos Grandes Laguna (Bolivia) is located in a volcanic caldera fed by active hot springs, with a carbonate crust extending over 40 km2. An integrated approach based on geology and hydrochemistry was used to characterize La Salsa, one of [...] Read more.
The lacustrine-to-palustrine Pastos Grandes Laguna (Bolivia) is located in a volcanic caldera fed by active hot springs, with a carbonate crust extending over 40 km2. An integrated approach based on geology and hydrochemistry was used to characterize La Salsa, one of its hydrothermal systems, composed of a flat mound with a hydrothermal discharge. The mound is composed of carbonate–diatom aggregates, forming muds that accumulate and undergo slight swelling. The discharge area along the hydrothermal pathway exhibits several facies and microfabrics, with considerable biological activity and microbialite development. Both the downstream evolution of carbonate and silica content in sediments and the distribution of microbialites can be linked to changes in biotic-abiotic processes occurring along the pathway. The spatial distribution of microbialites and their morphologies are related to hydrodynamic conditions, the nature of the substrate on which they grow and, to a lesser extent, to the accommodation space available. The evolution of the physicochemical properties of the water and biological activity mainly impact mineral precipitation but also affect microbialite morphologies and microstructures. This atypical Si- and Ca-rich hydrothermal system therefore provides insights into the diversity of environmental, chemical, and biotic factors controlling mineralization, which also responds to independent thermodynamic controls. Full article
(This article belongs to the Special Issue Microbialites: Preservation of Extant and Extinct Systems)
Figures

Figure 1

Open AccessArticle
Pilot-Scale Removal of Arsenic and Heavy Metals from Mining Wastewater Using Adsorption Combined with Constructed Wetland
Minerals 2019, 9(6), 379; https://doi.org/10.3390/min9060379
Received: 14 May 2019 / Revised: 12 June 2019 / Accepted: 20 June 2019 / Published: 23 June 2019
Viewed by 305 | PDF Full-text (1979 KB) | HTML Full-text | XML Full-text
Abstract
This study was conducted to assess the removal of arsenic (As) and heavy metals from mining wastewater by the combination of adsorption, using modified iron-ore drainage sludge, and horizontal-subsurface-flow constructed wetland with common reed (Phragmites australis). The pilot-scale experiment with a [...] Read more.
This study was conducted to assess the removal of arsenic (As) and heavy metals from mining wastewater by the combination of adsorption, using modified iron-ore drainage sludge, and horizontal-subsurface-flow constructed wetland with common reed (Phragmites australis). The pilot-scale experiment with a constant flow rate of 5 m3/day was operated for four months using real wastewater from a Pb–Zn mine in northern Vietnam. Atomic absorption spectroscopy was used for elemental analysis in wastewater and plant. X-ray diffraction (XRD), surface charge measurements (by a particle charge detector (PCD)), Fourier-transform infrared (FTIR), and surface area Brunauer–Emmet–Teller (BET) measurements were performed to determine the characteristics of the adsorbent. The results showed that the average removals of As, Mn, Cd, Zn, and Pb by the combined system with limestone substrate during four months were 80.3%, 96.9%, 79.6%, 52.9%, and 38.7%, respectively. The use of another constructed wetland substrate, laterite, demonstrated better removal efficiency of As than limestone. The concentrations of As and heavy metals in the effluent were lower than the limits established by the QCVN 40:2011/BTNMT for industrial wastewater, which indicated the feasibility of combining adsorption and constructed wetland for the treatment of mining wastewater. Full article
(This article belongs to the Special Issue Arsenic Geochemistry and Health)
Figures

Figure 1

Open AccessArticle
Post-spreading Basalts from the Nanyue Seamount: Implications for the Involvement of Crustal- and Plume-Type Components in the Genesis of the South China Sea Mantle
Minerals 2019, 9(6), 378; https://doi.org/10.3390/min9060378
Received: 28 May 2019 / Revised: 19 June 2019 / Accepted: 21 June 2019 / Published: 23 June 2019
Viewed by 347 | PDF Full-text (6370 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Fresh samples of basalts were collected by dredging from the Nanyue intraplate seamount in the Southwest sub-basin of the South China Sea (SCS). These are alkali basalts displaying right-sloping, chondrite-normalized rare earth element (REE) profiles. The investigated basalts are characterized by low Os [...] Read more.
Fresh samples of basalts were collected by dredging from the Nanyue intraplate seamount in the Southwest sub-basin of the South China Sea (SCS). These are alkali basalts displaying right-sloping, chondrite-normalized rare earth element (REE) profiles. The investigated basalts are characterized by low Os content (60.37–85.13 ppt) and radiogenic 187Os/188Os ratios (~0.19 to 0.21). Furthermore, 40Ar/39Ar dating of the Nanyue basalts showed they formed during the Tortonian (~8.3 Ma) and, thus, are products of (Late Cenozoic) post-spreading volcanism. The Sr–Nd–Pb–Hf isotopic compositions of the Nanyue basalts indicate that their parental melts were derived from an upper mantle reservoir possessing the so-called Dupal isotopic anomaly. Semiquantitative isotopic modeling demonstrates that the isotopic compositions of the Nanyue basalts can be reproduced by mixing three components: the average Pacific midocean ridge basalt (MORB), the lower continental crust (LCC), and the average Hainan ocean island basalt (OIB). Our preferred hypothesis for the genesis of the Nanyue basalts is that their parental magmas were produced from an originally depleted mantle (DM) source that was much affected by the activity of the Hainan plume. Initially, the Hainan diapir caused a thermal perturbation in the upper mantle under the present-day Southwest sub-basin of the SCS that led to erosion of the overlying LCC. Eventually, the resultant suboceanic lithospheric mantle (SOLM) interacted with OIB-type components derived from the nearby Hainan plume. Collectively, these processes contributed crustal- and plume-type components to the upper mantle underlying the Southwest sub-basin of the SCS. This implies that the Dupal isotopic signature in the upper mantle beneath the SCS was an artifact of in situ geological processes rather than a feature inherited from a Southern Hemispheric, upper mantle source. Full article
(This article belongs to the Section Mineral Deposits)
Figures

Figure 1

Open AccessArticle
Stable Isotope (S, Mg, B) Constraints on the Origin of the Early Precambrian Zhaoanzhuang Serpentine-Magnetite Deposit, Southern North China Craton
Minerals 2019, 9(6), 377; https://doi.org/10.3390/min9060377
Received: 23 May 2019 / Revised: 18 June 2019 / Accepted: 18 June 2019 / Published: 22 June 2019
Viewed by 298 | PDF Full-text (5915 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The origin of the Zhaoanzhuang serpentine-magnetite deposit in the southern North China Craton (NCC) is highly disputed, with some investigators having proposed an ultramafic origin, whereas others favor a chemical sedimentary origin. These discrepancies are largely due to the difficulty in determining the [...] Read more.
The origin of the Zhaoanzhuang serpentine-magnetite deposit in the southern North China Craton (NCC) is highly disputed, with some investigators having proposed an ultramafic origin, whereas others favor a chemical sedimentary origin. These discrepancies are largely due to the difficulty in determining the protolithic characteristics of the highly metamorphosed rocks. Sulfur, magnesium, and boron isotope geochemistry combined with detailed petrography was carried out in this study to constrain the original composition of the Zhaoanzhuang iron orebodies. Anhydrite is present as coarse crystals intergrown with magnetite, indicating that the anhydrite formed simultaneously with the magnetite during metamorphism rather than as a product of later hydrothermal alteration. The anhydrite has a narrow range of positive δ34S values from +19.8 to +22.5‰ with a mean value of +21.1‰. These values are significantly higher than that of typical magmatic sulfur (δ34S = 0 ± 5‰) and deviate away from primary igneous anhydrite towards mantle-sulfur isotopic values, but they are similar to those of marine evaporitic anhydrite and gypsum (~+21‰). The sulfur isotopic compositions of several samples show obvious signs of mass-independent sulfur fractionation (Δ33S = −0.47‰ to +0.90‰), suggesting that they were influenced by an external sulfur source through a photochemical reaction at low oxygen concentrations, which is consistent with the Neoarchean-Paleoproterozoic atmosphere. Coarse-grained tourmaline from the tourmaline-rich interlayers of the orebodies occurs closely with Mg-rich minerals such as phlogopite, talc, and diopside, indicating that it has a metamorphic origin. The δ11B values of the tourmaline range from −0.2‰ to +3.6‰ with a mean value of +2.0‰, which is much positive relative to that of magmatic tourmaline but is consistent with that of carbonate-derived tourmaline. The magnesium isotopic analyses of the serpentine–magnetite ores and the magnesium-rich wall rocks revealed a wide range of very negative δ26Mg values from −1.20‰ to −0.34‰ with an average value of −0.80‰. The value is higher than that of ultramafic rocks (δ26Mg = −0.25‰) and exhibits minor Mg isotopic fractionation. However, these values are consistent with those of marine carbonate rocks, which have lower δ26Mg values and larger Mg isotopic variations (δ26Mg = −0.45‰ to −4.5‰). Collectively, the S–Mg–B isotopic characteristics of the Zhaoanzhuang iron orebodies clearly indicate a chemical sedimentary origin. The protoliths of these orebodies most likely reflect a series of Fe–Si–Mg-rich marine carbonate rocks with a considerable evaporite component, indicating a carbonate-rich superior-type banded iron formation precipitated in an evaporitic shallow marine sedimentary environment. Full article
Figures

Figure 1

Open AccessArticle
Basalt Tectonic Discrimination Using Combined Machine Learning Approach
Minerals 2019, 9(6), 376; https://doi.org/10.3390/min9060376
Received: 20 March 2019 / Revised: 6 June 2019 / Accepted: 18 June 2019 / Published: 22 June 2019
Viewed by 314 | PDF Full-text (3004 KB) | HTML Full-text | XML Full-text
Abstract
Geochemical discrimination of basaltic magmatism from different tectonic settings remains an essential part of recognizing the magma generation process within the Earth’s mantle. Discriminating among mid-ocean ridge basalt (MORB), ocean island basalt (OIB) and island arc basalt (IAB) is that matters to geologists [...] Read more.
Geochemical discrimination of basaltic magmatism from different tectonic settings remains an essential part of recognizing the magma generation process within the Earth’s mantle. Discriminating among mid-ocean ridge basalt (MORB), ocean island basalt (OIB) and island arc basalt (IAB) is that matters to geologists because they are the three most concerned basalts. Being a supplement to conventional discrimination diagrams, we attempt to utilize the machine learning algorithm (MLA) for basalt tectonic discrimination. A combined MLA termed swarm optimized neural fuzzy inference system (SONFIS) was presented based on neural fuzzy inference system and particle swarm optimization. Two geochemical datasets of basalts from GEOROC and PetDB served as to test the classification performance of SONFIS. Several typical discrimination diagrams and well-established MLAs were also used for performance comparisons with SONFIS. Results indicated that the classification accuracy of SONFIS for MORB, OIB and IAB in both datasets could reach over 90%, superior to other methods. It also turns out that MLAs had certain advantages in making full use of geochemical characteristics and dealing with datasets containing missing data. Therefore, MLAs provide new research tools other than discrimination diagrams for geologists, and the MLA-based technique is worth extending to tectonic discrimination of other volcanic rocks. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
Figures

Figure 1

Open AccessArticle
A New Plagioclase-Liquid Hygrometer Specific to Trachytic Systems
Minerals 2019, 9(6), 375; https://doi.org/10.3390/min9060375
Received: 13 May 2019 / Revised: 10 June 2019 / Accepted: 20 June 2019 / Published: 22 June 2019
Viewed by 525 | PDF Full-text (1680 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present a new empirical plagioclase-liquid hygrometer for estimating the amount of H2O dissolved in trachytic magmas. The hygrometer is based on the exchange reaction of anorthite between plagioclase and liquid, and is calibrated using crystallization experiments where the concentration of [...] Read more.
We present a new empirical plagioclase-liquid hygrometer for estimating the amount of H2O dissolved in trachytic magmas. The hygrometer is based on the exchange reaction of anorthite between plagioclase and liquid, and is calibrated using crystallization experiments where the concentration of H2O in quenched glasses has been accurately determined based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The multiple linear regression of plagioclase-liquid cation fractions and components from experimental data obtained at 150–202 MPa, 850–1020 °C, 1.17–7.57 wt. % H2O and ΔNNO + 2.5 buffer, yields to a highly accurate model with uncertainty of only ±0.29 wt. % H2O. The model reliability has been demonstrated using an independent test data set consisting of crystallization experiments from the literature and thermodynamically derived compositions. The fairly good convergence between our model calibration and the test data set excludes systematic H2O overestimates or underestimates caused by miscalibration and data overfitting. The plagioclase-liquid hygrometer from this study has been applied to trachyandesitic (latitic) and trachytic products erupted over the last 1000 years at the La Fossa cone of Vulcano Island (Aeolian Islands, Southern Italy). Results from calculations indicate that the concentration of H2O in the latitic and trachytic melts is comprised between ~2.5 and ~3.5 wt. %. These values are in good agreement with data from melt inclusions and, overall, testify to low-pressure, open-system differentiation of trachytic magmas under strong degassing conditions. Full article
(This article belongs to the Special Issue Magma Plumbing Systems)
Figures

Figure 1

Open AccessArticle
Measurement of Process Conditions Present in Pilot Scale Iron Ore Sintering
Minerals 2019, 9(6), 374; https://doi.org/10.3390/min9060374
Received: 20 May 2019 / Revised: 18 June 2019 / Accepted: 18 June 2019 / Published: 22 June 2019
Viewed by 311 | PDF Full-text (17292 KB) | HTML Full-text | XML Full-text
Abstract
An improved experimental technique has been developed to measure, concurrently, the oxygen partial pressures and temperatures within a pilot scale iron ore sinter pot as a function of time. The measurements and thermodynamic calculations have demonstrated that the oxygen partial pressure at peak [...] Read more.
An improved experimental technique has been developed to measure, concurrently, the oxygen partial pressures and temperatures within a pilot scale iron ore sinter pot as a function of time. The measurements and thermodynamic calculations have demonstrated that the oxygen partial pressure at peak bed temperature and during cooling can be oxidising or reducing relative to hematite. Examples of typical microstructures and phase assemblages observed in product sinters are presented. Potential mechanisms of hematite and magnetite formation at sub-liquidus and sub-solidus conditions are demonstrated. The relative impacts of changes to coke rate and draft pressure drop on the process conditions and proportions of the phases formed in the sinter have been measured. Increasing coke rate was shown to result in a faster sinter heating rates, higher peak bed temperatures and times at peak temperature. Higher draft pressures across the sinter bed resulted in faster sinter heating rates and shorter times at peak temperature. Full article
(This article belongs to the Special Issue Mineralogy of Iron Ore Sinters)
Figures

Figure 1

Open AccessArticle
Thermal Behavior and Phase Transition of Uric Acid and Its Dihydrate Form, the Common Biominerals Uricite and Tinnunculite
Minerals 2019, 9(6), 373; https://doi.org/10.3390/min9060373
Received: 24 May 2019 / Revised: 19 June 2019 / Accepted: 21 June 2019 / Published: 22 June 2019
Viewed by 265 | PDF Full-text (4691 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Single crystals and powder samples of uric acid and uric acid dihydrate, known as uricite and tinnunculite biominerals, were extracted from renal stones and studied using single-crystal and powder X-ray diffraction (SC and PXRD) at various temperatures, as well as IR spectroscopy. The [...] Read more.
Single crystals and powder samples of uric acid and uric acid dihydrate, known as uricite and tinnunculite biominerals, were extracted from renal stones and studied using single-crystal and powder X-ray diffraction (SC and PXRD) at various temperatures, as well as IR spectroscopy. The results of high-temperature PXRD experiments revealed that the structure of uricite is stable up to 380 °C, and then it loses crystallinity. The crystal structure of tinnunculite is relatively stable up to 40 °C, whereas above this temperature, rapid release of H2O molecules occurs followed by the direct transition to uricite phase without intermediate hydration states. SCXRD studies and IR spectroscopy data confirmed the similarity of uricite and tinnunculite crystal structures. SCXRD at low temperatures allowed us to determine the dynamics of the unit cells induced by temperature variations. The thermal behavior of uricite and tinnunculite is essentially anisotropic; the structures not only expand, but also contract with temperature increase. The maximal expansion occurs along the unit cell parameter of 7 Å (b in uricite and a in tinnunculite) as a result of the shifts of chains of H-bonded uric acid molecules and relaxation of the π-stacking forces, the weakest intermolecular interactions in these structures. The strongest contraction in the structure of uricite occurs perpendicular to the (101) plane, which is due to the orthogonalization of the monoclinic angle. The structure of tinnunculite also contracts along the [010] direction, which is mostly due to the stretching mechanism of the uric acid chains. These phase transitions that occur within the range of physiological temperatures emphasize the particular importance of the structural studies within the urate system, due to their importance in terms of human health. The removal of supersaturation in uric acid in urine at the initial stages of stone formation can occur due to the formation of metastable uric acid dihydrate in accordance with the Ostwald rule, which would serve as a nucleus for the subsequent growth of the stone at further formation stages; afterward, it irreversibly dehydrates into anhydrous uric acid. Full article
Figures

Figure 1

Open AccessArticle
Spodumene Flotation Mechanism
Minerals 2019, 9(6), 372; https://doi.org/10.3390/min9060372
Received: 23 April 2019 / Revised: 31 May 2019 / Accepted: 11 June 2019 / Published: 21 June 2019
Viewed by 298 | PDF Full-text (2818 KB) | HTML Full-text | XML Full-text
Abstract
Fine and coarse fractions of spodumene were obtained from a pegmatite ore and their flotation was investigated under different conditions. In particular, the optimum pH and collector dosage were studied. It was found that the best flotation performance occurs at pH 10 using [...] Read more.
Fine and coarse fractions of spodumene were obtained from a pegmatite ore and their flotation was investigated under different conditions. In particular, the optimum pH and collector dosage were studied. It was found that the best flotation performance occurs at pH 10 using 250 mg/L of sodium oleate. It was also observed that upon the addition of CaCl2, spodumene flotation recovery increases to about 90%. In addition, poor floatability was found for spodumene when Na2CO3 was used as a pH regulator (compared to NaOH).The zeta potential data confirmed the adsorption of oleate on the spodumene surface. It was found that activation of spodumene by calcium ions makes the surface charge less negative due to the adsorption of Ca2+ on the surface. The crystallographic properties of spodumene were analyzed. The adsorption of sodium oleate was attributed to the chemisorption of oleate to the exposed Al and Si sites generated after breakage of the Al–O and Si–O bonds on the mineral surface. It was observed that the {110} planes are the most favorable for the adsorption of oleate. The {110} plane is the weakest plane, and spodumene has the highest tendency to cleave along this plane. The XRD data revealed that fine spodumene particles have more {110} planes than the coarser fraction, which may explain why the former has better floatability. Full article
(This article belongs to the Section Mineral Processing and Metallurgy)
Figures

Figure 1

Open AccessReview
The Olympic Cu-Au Province, Gawler Craton: A Review of the Lithospheric Architecture, Geodynamic Setting, Alteration Systems, Cover Successions and Prospectivity
Minerals 2019, 9(6), 371; https://doi.org/10.3390/min9060371
Received: 29 May 2019 / Revised: 17 June 2019 / Accepted: 19 June 2019 / Published: 20 June 2019
Viewed by 830 | PDF Full-text (17976 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The Olympic Cu-Au Province is a metallogenic province in South Australia that contains one of the world’s most significant Cu-Au-U resources in the Olympic Dam deposit. The Olympic Cu-Au Province also hosts a range of other iron oxide-copper-gold (IOCG) deposits including Prominent Hill [...] Read more.
The Olympic Cu-Au Province is a metallogenic province in South Australia that contains one of the world’s most significant Cu-Au-U resources in the Olympic Dam deposit. The Olympic Cu-Au Province also hosts a range of other iron oxide-copper-gold (IOCG) deposits including Prominent Hill and Carrapateena. This paper reviews the geology of the Olympic Cu-Au Province by investigating the lithospheric architecture, geodynamic setting and alteration systematics. In addition, since the province is almost entirely buried by post-mineral cover, the sedimentary cover sequences are also reviewed. The Olympic Cu-Au Province formed during the early Mesoproterozoic, ca. 1.6 Ga and is co-located with a fundamental lithospheric boundary in the eastern Gawler Craton. This metallogenic event was driven in part by melting of a fertile, metasomatized sub-continental lithospheric mantle during a major regional tectonothermal event. Fluid evolution and multiple fluid mixing resulted in alteration assemblages that range from albite, magnetite and other higher temperature minerals to lower temperature assemblages such as hematite, sericite and chlorite. IOCG mineralisation is associated with both high and low temperature assemblages, however, hematite-rich IOCGs are the most economically significant. Burial by Mesoproterzoic and Neoproterozoic-Cambrian sedimentary successions preserved the Olympic Cu-Au Province from erosion, while also providing a challenge for mineral exploration in the region. Mineral potential modelling identifies regions within the Olympic Cu-Au Province and adjacent Curnamona Province that have high prospects for future IOCG discoveries. Exploration success will rely on improvements in existing potential field and geochemical data, and be bolstered by new 3D magnetotelluric surveys. However, drilling remains the final method for discovery of new mineral resources. Full article
(This article belongs to the Special Issue Iron Oxide-Copper-gold (IOCG) Deposits)
Figures

Graphical abstract

Open AccessArticle
Jahn-Teller Distortion and Cation Ordering: The Crystal Structure of Paratooite-(La), a Superstructure of Carbocernaite
Minerals 2019, 9(6), 370; https://doi.org/10.3390/min9060370
Received: 23 May 2019 / Revised: 16 June 2019 / Accepted: 18 June 2019 / Published: 20 June 2019
Viewed by 253 | PDF Full-text (4933 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The crystal structure of paratooite-(La) has been solved using crystals from the type locality, Paratoo copper mine, near Yunta, Olary Province, South Australia, Australia. The mineral is orthorhombic, Pbam, a = 7.2250(3) Å, b = 12.7626(5) Å, c = 10.0559(4) Å, V [...] Read more.
The crystal structure of paratooite-(La) has been solved using crystals from the type locality, Paratoo copper mine, near Yunta, Olary Province, South Australia, Australia. The mineral is orthorhombic, Pbam, a = 7.2250(3) Å, b = 12.7626(5) Å, c = 10.0559(4) Å, V = 927.25(6) Å3, and R1 = 0.063 for 1299 unique observed reflections. The crystal structure contains eight symmetrically independent cation sites. The La site, which accommodates rare earth elements (REEs), but also contains Sr and Ca, has a tenfold coordination by seven carbonate groups. The Ca, Na1, and Na2 sites are coordinated by eight, eight, and six O atoms, respectively, forming distorted CaO8 and Na1O8 cubes, and Na2O6 octahedra. The Cu site is occupied solely by copper and possess a distorted octahedral coordination with four short (1.941 Å) and two longer (2.676 Å) apical Cu–O bonds. There are three symmetrically independent carbonate groups (CO3)2− with the average <C–O> bond lengths equal to 1.279, 1.280, and 1.279 Å for the C1, C2, and C3 sites, respectively. The crystal structure of paratooite-(La) can be described as a strongly distorted body-centered lattice formed by metal cations with (CO3)2− groups filling its interstices. According to the chemical and crystal-structure data, the crystal-chemical formula of paratooite-(La) can be described as (La0.74Ca0.11Sr0.07)4CuCa(Na0.75Ca0.15)(Na0.63)(CO3)8 or REE2.96Ca1.59Na1.38CuSr0.28(CO3)8. The idealized formula can be written as (La,Sr,Ca)4CuCa(Na,Ca)2(CO3)8. The structure of paratooite is a 1 × 2 × 2 superstructure of carbocernaite, CaSr(CO3)2. The superstructure arises due to the ordering of the chemically different Cu2+ cations, on one hand, and Na+ and Ca2+ cations, on the other hand. The formation of a superstructure due to the cation ordering in paratooite-(La) compared to carbocernaite results in the multiple increase of structural complexity per unit cell. Therefore, paratooite-(La) versus carbocernaite represents a good example of structural complexity increasing due to the increasing chemical complexity controlled by different electronic properties of mineral-forming chemical elements (transitional versus alkali and alkaline earth metals). Full article
Figures

Figure 1

Open AccessArticle
Bubble Size Distribution Characteristics of a Jet-Stirring Coupling Flotation Device
Minerals 2019, 9(6), 369; https://doi.org/10.3390/min9060369
Received: 6 May 2019 / Revised: 3 June 2019 / Accepted: 17 June 2019 / Published: 20 June 2019
Viewed by 261 | PDF Full-text (2714 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a new jet-stirring coupling flotation device that incorporates the advantages of three conventional flotation machines (specifically, Jameson cell, mechanical flotation cell, flotation column) was designed based on jet suction. The suction capacity of a double cosine self-aspirated nozzle utilized by [...] Read more.
In this study, a new jet-stirring coupling flotation device that incorporates the advantages of three conventional flotation machines (specifically, Jameson cell, mechanical flotation cell, flotation column) was designed based on jet suction. The suction capacity of a double cosine self-aspirated nozzle utilized by the device was analyzed under different feeding pressures, and the effects of frother concentration, feeding pressure, suction capacity, and height of sampling location on the bubble size distribution (BSD) were investigated using a high-speed video system. It was found that a large amount of air was sucked into the flotation cell by the self-aspirated nozzle arranged in a non-submerged manner, which met the requirements of flotation in terms of the suction amount of air. The suction capacity showed a positive linear correlation with negative pressure inside the nozzle. When the Methyl isobutyl carbinol (MIBC) concentration reached the critical coalescence concentration (CCC), the bubble size stabilized at approximately 0.31 mm, which was smaller than the bubble size produced by the conventional flotation machine. This indicated that bubbles suitable for flotation were generated. D32 linearly decreased with increasing of feeding pressures and conversely increased with increasing suction capacities and sampling location heights, independent of the frother concentration. Full article
Figures

Graphical abstract

Open AccessArticle
Comparison of Methods for Determining the Thresholds of Geochemical Anomalies and the Prospecting Direction—A Case of Gold Deposits in the Gouli Exploration Area, Qinghai Province
Minerals 2019, 9(6), 368; https://doi.org/10.3390/min9060368
Received: 4 April 2019 / Revised: 3 June 2019 / Accepted: 10 June 2019 / Published: 18 June 2019
Viewed by 344 | PDF Full-text (14157 KB) | HTML Full-text | XML Full-text
Abstract
Geochemical anomalies play an important role in mineral exploration, because they are closely related to the formation of ore deposits. In this paper, the Au in the geochemical samples of 1:50,000 stream sediments in the Gouli exploration area, Qinghai Province, is selected as [...] Read more.
Geochemical anomalies play an important role in mineral exploration, because they are closely related to the formation of ore deposits. In this paper, the Au in the geochemical samples of 1:50,000 stream sediments in the Gouli exploration area, Qinghai Province, is selected as an example. The cumulative frequency method, local singularity analysis, and exploration data analysis method are used to process the Au data and determine the abnormal thresholds. Robust principal component analysis is used to explore the elemental associations. Among them, the effect of local singularity analysis is the best and it delineates the weak geochemical anomalies not delineated by cumulative frequency method and exploration data analysis method, which shows its superiority. Robust principal component analysis shows that Sb, W, and As are closely related to Au mineralization. Three anomalous areas are delineated in the Gouli exploration area. Gold ore-body is found to occur within anomaly area I. The other anomalous areas are highly consistent with abnormal elemental composition of Sb, W, and As. Moreover, these two areas are extremely conformable with the high-value areas determined by the binary state method. The optimality of the three methods are compared comprehensively, it is pointed out that it is more reasonable to use the local singularity analysis to determine the abnormal threshold. The anomaly areas II and III of Au determined by local singularity analysis have shown great potential for prospecting. Full article
Figures

Figure 1

Open AccessArticle
Critical Metals Ga, Ge and In: Experimental Evidence for Smelter Recovery Improvements
Minerals 2019, 9(6), 367; https://doi.org/10.3390/min9060367
Received: 15 April 2019 / Revised: 11 June 2019 / Accepted: 15 June 2019 / Published: 18 June 2019
Viewed by 322 | PDF Full-text (1755 KB) | HTML Full-text | XML Full-text
Abstract
High-tech metals, including Ga, Ge and In, are critical for the performance of electrical and electronic equipment (EEE). None of these three metals exist in mineable levels in natural minerals, and thus their availability and production are dependent on the primary and secondary [...] Read more.
High-tech metals, including Ga, Ge and In, are critical for the performance of electrical and electronic equipment (EEE). None of these three metals exist in mineable levels in natural minerals, and thus their availability and production are dependent on the primary and secondary base metals (including Zn, Al and Cu) production. To secure the supply of high-tech metals in the future, their behavior, including distribution coefficients (LCu/s = [wt% M]in copper/(wt% M)in slag), in primary and secondary processes need to be characterized. This study reports three series of copper-slag distribution experiments for Ga, Ge and In in simulated secondary copper smelting and refining process conditions (T = 1300 °C, pO2 = 10−9–10−5 atm) using a well-developed drop–quench technique followed by EPMA and LA-ICP-MS analyses. This study shows how an analytical technique more traditionally applied to the characterization of ores or minerals can also be applied to metallurgical process investigation. The LA-ICP-MS analysis was used for the first time for measuring the concentrations of these minor elements in metallurgical glasses, i.e., slags, and the results were compared to the geological literature. The distribution coefficient of indium increased as a function of decreasing oxygen partial pressure from 0.03 to 10, whereas the distribution coefficient of gallium was 0.1 at 10−9 atm and decreased as the pO2 increased. The concentrations of gallium in slags were between 0.4 and 0.6 wt% and germanium around 1 ppm. Germanium was vaporized almost entirely from the samples. Full article
Figures

Figure 1

Open AccessArticle
Optimization of Solids Concentration in Iron Ore Ball Milling through Modeling and Simulation
Minerals 2019, 9(6), 366; https://doi.org/10.3390/min9060366
Received: 24 May 2019 / Revised: 12 June 2019 / Accepted: 13 June 2019 / Published: 18 June 2019
Viewed by 272 | PDF Full-text (4947 KB) | HTML Full-text | XML Full-text
Abstract
Important advances have been made in the last 60 years or so in the modeling of ball mills using mathematical formulas and models. One approach that has gained popularity is the population balance model, in particular, when coupled to the specific breakage rate [...] Read more.
Important advances have been made in the last 60 years or so in the modeling of ball mills using mathematical formulas and models. One approach that has gained popularity is the population balance model, in particular, when coupled to the specific breakage rate function. The paper demonstrates the application of this methodology to optimize solids concentration in ball milling of an iron ore from Brazil. The wet grinding experiments were conducted in bench (0.25 m diameter) and pilot-scale mills (0.42 m diameter), and surveys in a full-scale industrial (5.2 m diameter) mill. It is first demonstrated that the successful application of the model required recognizing the non-normalizable nature of the breakage function of the particular ore. It is then demonstrated how the model can be used to predict results of pilot-scale grinding tests under different conditions (overflow/grate discharge) based on data from batch grinding tests. Finally, the model is used to predict the effect of changing solids concentration inside the industrial mill, with good correspondence between the pilot plant and full-scale results, which demonstrated the benefit of reducing solids concentration to values between 76 and 80% in weight for the ore of interest from the 83% that was originally used in the operation. Full article
(This article belongs to the Section Mineral Processing and Metallurgy)
Figures

Figure 1

Open AccessEditorial
Editorial for the Special Issue “Platinum-Group Minerals: New Results and Advances in PGE Mineralogy in Various Ni-Cu-Cr-PGE Ore Systems”
Minerals 2019, 9(6), 365; https://doi.org/10.3390/min9060365
Received: 10 June 2019 / Accepted: 11 June 2019 / Published: 17 June 2019
Viewed by 454 | PDF Full-text (162 KB) | HTML Full-text | XML Full-text
Abstract
The platinum-group minerals (PGM) consist of a group of accessory minerals that concentrate the six platinum-group elements (PGE): osmium (Os), iridium (Ir), ruthenium (Ru), rhodium (Rh), platinum (Pt), and palladium (Pd) [...] Full article
Open AccessArticle
Zircon at the Nanoscale Records Metasomatic Processes Leading to Large Magmatic–Hydrothermal Ore Systems
Minerals 2019, 9(6), 364; https://doi.org/10.3390/min9060364
Received: 30 April 2019 / Revised: 1 June 2019 / Accepted: 13 June 2019 / Published: 16 June 2019
Cited by 1 | Viewed by 649 | PDF Full-text (22416 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The petrography and geochemistry of zircon offers an exciting opportunity to better understand the genesis of, as well as identify pathfinders for, large magmatic–hydrothermal ore systems. Electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, high-angle annular dark-field scanning transmission electron microscopy [...] Read more.
The petrography and geochemistry of zircon offers an exciting opportunity to better understand the genesis of, as well as identify pathfinders for, large magmatic–hydrothermal ore systems. Electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging, and energy-dispersive X-ray spectrometry STEM mapping/spot analysis were combined to characterize Proterozoic granitic zircon in the eastern Gawler Craton, South Australia. Granites from the ~1.85 Ga Donington Suite and ~1.6 Ga Hiltaba Suite were selected from locations that are either mineralized or not, with the same style of iron-oxide copper gold (IOCG) mineralization. Although Donington Suite granites are host to mineralization in several prospects, only Hiltaba Suite granites are considered “fertile” in that their emplacement at ~1.6 Ga is associated with generation of one of the best metal-endowed IOCG provinces on Earth. Crystal oscillatory zoning with respect to non-formula elements, notably Fe and Cl, are textural and chemical features preserved in zircon, with no evidence for U or Pb accumulation relating to amorphization effects. Bands with Fe and Ca show mottling with respect to chloro–hydroxy–zircon nanoprecipitates. Lattice defects occur along fractures crosscutting such nanoprecipitates indicating fluid infiltration post-mottling. Lattice stretching and screw dislocations leading to expansion of the zircon structure are the only nanoscale structures attributable to self-induced irradiation damage. These features increase in abundance in zircons from granites hosting IOCG mineralization, including from the world-class Olympic Dam Cu–U–Au–Ag deposit. The nano- to micron-scale features documented reflect interaction between magmatic zircon and corrosive Fe–Cl-bearing fluids in an initial metasomatic event that follows magmatic crystallization and immediately precedes deposition of IOCG mineralization. Quantification of α-decay damage that could relate zircon alteration to the first percolation point in zircon gives ~100 Ma, a time interval that cannot be reconciled with the 2–4 Ma period between magmatic crystallization and onset of hydrothermal fluid flow. Crystal oscillatory zoning and nanoprecipitate mottling in zircon intensify with proximity to mineralization and represent a potential pathfinder to locate fertile granites associated with Cu–Au mineralization. Full article
(This article belongs to the Special Issue Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes)
Figures

Figure 1

Open AccessArticle
Cryogenic Raman Spectroscopic Studies on Common Ore-forming Fluid Systems
Minerals 2019, 9(6), 363; https://doi.org/10.3390/min9060363
Received: 10 May 2019 / Revised: 5 June 2019 / Accepted: 10 June 2019 / Published: 13 June 2019
Viewed by 333 | PDF Full-text (12757 KB) | HTML Full-text | XML Full-text
Abstract
The composition and properties of ore-forming fluids are key to understanding the mechanisms of mineralization in ore deposits. These characteristics can be understood by studying fluid inclusions. Hydrates in fluid inclusions containing NaCl–H2O and MgCl2–H2O were studied [...] Read more.
The composition and properties of ore-forming fluids are key to understanding the mechanisms of mineralization in ore deposits. These characteristics can be understood by studying fluid inclusions. Hydrates in fluid inclusions containing NaCl–H2O and MgCl2–H2O were studied using cryogenic Raman spectroscopy. The intensity ratio of peaks at 3401, 3464, 3514, and 3090 cm−1 shows a positive correlation with the concentration of hydrates in the inclusions, as does the ratio of the total integrated area of the MgCl2 hydrate peak (3514 cm−1) to the 3090 cm−1 peak with the concentration of MgCl2 (correlation coefficient >0.90). These correlations are important in the quantitative analysis of MgCl2 in synthetic and natural NaCl–MgCl2–CaCl2–H2O-bearing fluid inclusions. Semi-quantitative analysis of NaCl–MgCl2–H2O solutions indicates that peaks at 3437 and 3537 cm−1 reflect the presence of NaCl in the solution. Further, a peak at 3514 cm−1 is indicative of the presence of MgCl2. The relative intensities of these peaks may be related to the relative abundances of NaCl and MgCl2. A quantitative attempt was made on NaCl–MgCl2–CaCl2–H2O system, but it was found that quantifying NaCl, MgCl2 and CaCl2 separately in NaCl–MgCl2–CaCl2–H2O system by the secondary freezing method is difficult. Full article
Figures

Figure 1

Open AccessReview
A Review on Comprehensive Utilization of Red Mud and Prospect Analysis
Minerals 2019, 9(6), 362; https://doi.org/10.3390/min9060362
Received: 21 April 2019 / Revised: 6 June 2019 / Accepted: 10 June 2019 / Published: 13 June 2019
Viewed by 290 | PDF Full-text (1430 KB) | HTML Full-text | XML Full-text
Abstract
Red mud (RM) is a by-product of extracting of alumina from bauxite. Red mud contains high quantities of alkali-generating minerals and metal ions, which can cause significant environmental damage. Many valuable components such as rare-earth elements, Al, and Fe, in RM are difficult [...] Read more.
Red mud (RM) is a by-product of extracting of alumina from bauxite. Red mud contains high quantities of alkali-generating minerals and metal ions, which can cause significant environmental damage. Many valuable components such as rare-earth elements, Al, and Fe, in RM are difficult to be utilized owing to their particle size and alkalinity. Thus, developing an economical and efficient technology to consume a large amount of RM can efficiently solve RM disposal issues. This paper systematically reviews the comprehensive utilization methods for reducing RM environmental pollution and divides the comprehensive utilization of RM into three aspects: the effective extraction of valuable components, resource transformation, and environmental application. Based on resource, economic, and environmental benefits, the development of new technologies and new processes with market competitiveness, environmental protection, and ecological balance should be the prerequisite for the low-energy, low-pollution, low-cost, and high-efficiency comprehensive utilization of RM. The direction of future research to solve RM disposal issues is also suggested. Full article
Figures

Figure 1

Open AccessArticle
Thermodynamic Modelling of Iron Ore Sintering Reactions
Minerals 2019, 9(6), 361; https://doi.org/10.3390/min9060361
Received: 20 May 2019 / Revised: 7 June 2019 / Accepted: 7 June 2019 / Published: 13 June 2019
Viewed by 303 | PDF Full-text (3523 KB) | HTML Full-text | XML Full-text
Abstract
Silico-ferrite of calcium and aluminum (SFCA) is one of the most commonly-produced phases in fluxed iron-ore sintering, and has long been regarded as an important bonding phase in industrial sinters. It is thus considered to have a significant effect on sinter quality. In [...] Read more.
Silico-ferrite of calcium and aluminum (SFCA) is one of the most commonly-produced phases in fluxed iron-ore sintering, and has long been regarded as an important bonding phase in industrial sinters. It is thus considered to have a significant effect on sinter quality. In this study, a solid solution model and database has been developed for the SFCA phase, and has been incorporated into the thermodynamic software, Multi-Phase Equilibrium (MPE). MPE calculations were compared with the in situ X-ray powder diffraction (XRD) observations of the formation of SFCA phase during sintering. The effects of the raw material composition, temperature and the oxygen partial pressure on the formation of mineral phases in the sinter, as well as the viscosity of the melt formed during sintering under equilibrium conditions, were modelled using MPE. The results show that the formation of SFCA phase can be promoted by increasing oxygen partial pressure and basicity of the raw material. Increases of Al2O3 and MgO content have no significant effect on the SFCA formation under equilibrium condition. The increase of oxygen partial pressure (10−3 atm or above) and basicity also leads to a decrease in melt viscosity, which enhances the fluidity of the melt, and hence, the assimilation of the sinter. However, increases of Al2O3 and MgO result in the increase of melt viscosity. Full article
(This article belongs to the Special Issue Mineralogy of Iron Ore Sinters)
Figures

Figure 1

Open AccessArticle
Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China
Minerals 2019, 9(6), 360; https://doi.org/10.3390/min9060360
Received: 5 May 2019 / Accepted: 22 May 2019 / Published: 13 June 2019
Viewed by 293 | PDF Full-text (7585 KB) | HTML Full-text | XML Full-text
Abstract
The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence [...] Read more.
The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence and their fault controls for Ordovician carbonates in the northern Tarim intracratonic basin in NW China (Halahatang area). In contrast to the uniform nature of diagenesis observed in country rocks, there is a relatively complicated style of compaction and pressure solution, multiple fracturing, and cementation and dissolution history along the carbonate fault damage zones. The relative paragenetic sequence of the structure related diagenesis suggests three cycles of fracture activities, following varied fracture enlargement and dissolution, and progressively weaker calcite cementation. These processes of structure related diagenesis are constrained to the fault damage zones, and their variation is affected by the fault activities. The results of this study suggest that the carbonate reservoir and productivity could be impacted by the structure related diagenesis locally along the fault damage zones. Full article
Figures

Figure 1

Open AccessArticle
The Role of the Substrate on the Mineralization Potential of Microbial Mats in A Modern Freshwater River (Paris Basin, France)
Minerals 2019, 9(6), 359; https://doi.org/10.3390/min9060359
Received: 15 May 2019 / Revised: 29 May 2019 / Accepted: 11 June 2019 / Published: 13 June 2019
Cited by 1 | Viewed by 389 | PDF Full-text (30134 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The relationship between environmental conditions and the development, mineralization and preservation of modern tufa microbialites was investigated in a 1.1 km long freshwater stream in Villiers-le-Bâcle, a tributary of Mérantaise river. Detailed mapping of the tufa microbialite distribution combined with sedimentological, petrographical and [...] Read more.
The relationship between environmental conditions and the development, mineralization and preservation of modern tufa microbialites was investigated in a 1.1 km long freshwater stream in Villiers-le-Bâcle, a tributary of Mérantaise river. Detailed mapping of the tufa microbialite distribution combined with sedimentological, petrographical and mineralogical analyses were coupled with chemical measurements. Six organosedimentary structures were identified; their distribution appears heterogeneous along the stream and responds to physicochemical conditions of water and specific biological components (e.g., microorganism, exopolymeric substance). Two of the organosedimentary structures show evidence of mineralization and only one is lithified. Based on field observations and in-situ deployment of mineralization markers (bricks), three zones with increasing mineralization intensities are defined, ranging from no mineralization to thick mineralized crusts forming riverine tufa. Both biotic and abiotic processes were proposed for the tufa microbialite formation. We explained changes in mineralization intensities by the specific physicochemical conditions (e.g., calcite saturation index (SIcalc) and partial pressure of CO2 (pCO2) and a closed proximity of the cyanobacterial biofilm and carbonates precipitates. The physical and chemical composition of substrate impact development of microbial communities, mineralization potential of tufa microbialite. Even though the physicochemical and biological conditions were optimal for mineral precipitation, the potential of lithification depended on the presence of a suitable (physical and chemical) substrate. Full article
(This article belongs to the Special Issue Microbialites: Preservation of Extant and Extinct Systems)
Figures

Figure 1

Open AccessArticle
Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China
Minerals 2019, 9(6), 358; https://doi.org/10.3390/min9060358
Received: 13 March 2019 / Revised: 31 May 2019 / Accepted: 1 June 2019 / Published: 12 June 2019
Viewed by 324 | PDF Full-text (2873 KB) | HTML Full-text | XML Full-text
Abstract
In order to determine the structural characterization of aluminosilicates in two types of fly ashes, two samples from Shanxi Province, China were selected for study. One was from a pulverized coal boiler (FA-1), and the other from a circulating fluidized bed boiler (FA-2). [...] Read more.
In order to determine the structural characterization of aluminosilicates in two types of fly ashes, two samples from Shanxi Province, China were selected for study. One was from a pulverized coal boiler (FA-1), and the other from a circulating fluidized bed boiler (FA-2). FA-1 had a much higher content of silicon dioxide (SiO2) (70.30%) than FA-2(42.19%), but aluminum oxide (Al2O3) was higher in FA-2 (25.41%) than in FA-1 (17.04%). The characterizations were investigated using various methods including X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), magic angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, and X-ray photoelectron spectroscopy (XPS). The XRD analysis showed that FA-1 contained aluminosilicate glass, quartz and mullite, while FA-2 contained significant amounts of amorphous aluminosilicate, quartz and gypsum. The FTIR results showed an increased substitution of Al3+ for Si4+ as the band of asymmetric stretching vibrations Si–O(Si) (1100 cm−1) moved to 1090 cm−1 for FA-2, much lower than for FA-1(1097 cm−1). Moreover, the sharpness of the bands in the 1250–1000 cm−1 region for FA-2 indicates that the silicate structure of FA-2 was more ordered than for FA-1. It can be understood from the 29Si MAS–NMR results that Q4(mAl) (Q4 are connected via 4 bridging O atoms to mAl) is the main structural type in FA-1 and FA-2, and that FA-2 contains more Al, which substitutes for Si in the Q4 structure. 27Al MAS–NMR demonstrated that a combination of tetrahedral, pentahedral, and octahedral Al existed in FA-1 and FA-2. The Si 2p XPS spectra suggested that there were three forms of Si, including bridging Si (Si–O2), non–bridging Si (Si–O), and SiO2 gel. The content of Si–O2 for FA-1 was 37.48% higher than Si–O (28.57%), while the content of Si–O2 was 30.21% lower than Si–O (40.15%) for FA-2. The Al 2p XPS spectra showed that octahedral Al was the dominant form for FA-1 with a content of 40.25%, while the main phase was tetrahedral Al for FA-2 with a proportion of 37.36%, which corresponds well with the 27Al MAS–NMR results. Full article
(This article belongs to the collection Minerals in Coal and Coal Combustion Products)
Figures

Figure 1

Open AccessArticle
Chemical Characteristics of Freshwater and Saltwater Natural and Cultured Pearls from Different Bivalves
Minerals 2019, 9(6), 357; https://doi.org/10.3390/min9060357
Received: 19 April 2019 / Revised: 26 May 2019 / Accepted: 5 June 2019 / Published: 12 June 2019
Viewed by 365 | PDF Full-text (4795 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The present study applied Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) on a large number of natural and cultured pearls from saltwater and freshwater environments, which revealed that freshwater (natural and cultured) pearls contain relatively higher quantities of manganese (Mn) and barium (Ba) and [...] Read more.
The present study applied Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) on a large number of natural and cultured pearls from saltwater and freshwater environments, which revealed that freshwater (natural and cultured) pearls contain relatively higher quantities of manganese (Mn) and barium (Ba) and lower sodium (Na), magnesium (Mg) and strontium (Sr) than saltwater (natural and cultured) pearls. A few correlations between the host animal’s species and chemical elements were found; some samples from Pinctada maxima (P. maxima) are the only studied saltwater samples with 55Mn >20 ppmw, while some P. radiata are the only studied saltwater samples with 24Mg <65 ppmw and some of the P. imbricata are the only studied saltwater samples with 137Ba >4.5 ppmw. X-ray luminescence reactions of the studied samples has confirmed a correlation between its yellow-green intensity and manganese content in aragonite, where the higher Mn2+ content, the more intense the yellow-green luminescence becomes. Luminescence intensity in some cases is lower even if manganese increases, either because of pigments or because of manganese self-quenching. X-ray luminescence can be applied in most cases to separate saltwater from freshwater samples; only samples with low manganese content (55Mn <50 ppmw) might be challenging to identify. One of the studied natural freshwater pearls contained vaterite sections which react by turning orange under X-ray due to a different coordination of Mn2+ in vaterite than that in aragonite. Full article
(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)
Figures

Figure 1

Open AccessArticle
Nano-Scale Pore Structure and Fractal Dimension of Longmaxi Shale in the Upper Yangtze Region, South China: A Case Study of the Laifeng–Xianfeng Block Using HIM and N2 Adsorption
Minerals 2019, 9(6), 356; https://doi.org/10.3390/min9060356
Received: 30 April 2019 / Revised: 1 June 2019 / Accepted: 8 June 2019 / Published: 12 June 2019
Viewed by 277 | PDF Full-text (5928 KB) | HTML Full-text | XML Full-text
Abstract
This paper tries to determine the key evaluation parameters of shale reservoirs in the complex tectonic provinces outside the Sichuan Basin in South China, and also to target the sweet spots of shale reservoirs accurately. The pore-structure characteristics of the Lower Silurian Longmaxi [...] Read more.
This paper tries to determine the key evaluation parameters of shale reservoirs in the complex tectonic provinces outside the Sichuan Basin in South China, and also to target the sweet spots of shale reservoirs accurately. The pore-structure characteristics of the Lower Silurian Longmaxi shale gas reservoirs in Well LD1 of the Laifeng–Xianfeng Block, Upper Yangtze region, were evaluated. N2 adsorption and helium ion microscope (HIM) were used to investigate the pore features including pore volume, pore surface area, and pore size distribution. The calculated results show good hydrocarbon storage capacity and development potential of the shale samples. Meanwhile, the reservoir space and migration pathways may be affected by the small pore size. As the main carrier of pores in shale, organic matter contributes significantly to the pore volume and surface area. Samples with higher total organic carbon (TOC) content generally have higher porosity. Based on the Frenkel–Halsey–Hill equation (FHH model), two different fractal dimensions, D1 and D2, were observed through the N2 adsorption experiment. By analyzing the data, we found that large pores usually have large values of fractal dimension, owing to their complex pore structure and rough surface. In addition, there exists a good positive correlation between fractal dimension and pore volume as well as pore surface area. The fractal dimension can be taken as a visual indicator that represents the degree of development of the pore structure in shale. Full article
(This article belongs to the Special Issue Nanomineralogy)
Figures

Figure 1

Open AccessArticle
Provenance of Heavy Minerals: A Case Study from the WNW Portuguese Continental Margin
Minerals 2019, 9(6), 355; https://doi.org/10.3390/min9060355
Received: 27 February 2019 / Revised: 6 June 2019 / Accepted: 10 June 2019 / Published: 12 June 2019
Viewed by 308 | PDF Full-text (24824 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This work describes and interprets the presence of heavy minerals in the WNW Portuguese continental margin using a set of 78 bottom samples collected from three distinct areas of this margin: the Porto, Aveiro, and Nazaré canyon head areas. The main transparent heavy [...] Read more.
This work describes and interprets the presence of heavy minerals in the WNW Portuguese continental margin using a set of 78 bottom samples collected from three distinct areas of this margin: the Porto, Aveiro, and Nazaré canyon head areas. The main transparent heavy mineral assemblage (mineral grains with frequencies ≥1% identified under a petrographic microscope) is composed of amphibole, andalusite, tourmaline, biotite, garnet, staurolite, pyroxene, zircon, and apatite. The felsic igneous and metamorphic rock outcrops in the main Northern Portuguese river basins and the relict sedimentary continental shelf deposits explained the presence of most of these mineral grains (both considered as distal sources). However, the presence of pargasite, augite, diopside-hedenbergite, enstatite-ferrosilite, and forsterite in the Porto and Aveiro areas (minerals identified by electronic microprobe analysis) is probably related to the presence of an igneous basic source next to dolomitic limestones affected by thermal metamorphism. These geological formations are considered as local sources. The high concentration of biotite observed in the Nazaré area is the result of the selective transport of the most lamellar sand particles of this mineral. Full article
(This article belongs to the Special Issue Heavy Minerals)
Figures

Graphical abstract

Minerals EISSN 2075-163X Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top