Main Mineral Phases Research Articles

Age constraints of the Wassa and Benso mesothermal gold deposits, Ashanti Belt, Ghana, West Africa

The Ashanti Belt in Ghana hosts numerous multi-million ounce gold deposits and is one of the most richly gold endowed Paleoproterozoic belts of the West African Craton. This work shows that the Wassa mineralized intrusion is part of the Sefwi Group. This unit at Wassa is strongly magnetic and show a distinctly high response in regional magnetic data sets compared to other units of equivalent age within the belt. The unit is inferred to be a lateral extension of an exposed fragment of what defines the substrate to the Tarkwa Basin sediments.The Wassa deposit, located in the eastern limb of the belt, is hosted within mafic to intermediate volcanic flows that are interbedded with minor horizons of volcaniclastics, clastic sediments. The clastic sediments include wackes and magnetite rich sedimentary layers, presumably derived from banded iron formations. The previously described sequence is intruded by syn-volcanic mafic intrusives and felsic porphyries rocks that are all part of the Birimian stratigraphy. Two new key SHRIMP II U–Pb ages were determined as part of this study: a new age of 2191±6Ma was determined on magmatic zircon grains of the Wassa porphyry host rock, which now represents the oldest known felsic intrusion hosting gold mineralization in the Ashanti Belt region.The Benso gold deposit system, which is located in the eastern limb of the Ashanti Belt approximately 38km southwest of Wassa is hosted within a series of volcanic units intruded by mafic to intermediate units. A SHRIMP II U–Pb age of 2157±5Ma was determined from magmatic zircons obtained from a granodiorite of the G-Zone of the Benso deposit. This granodiorite is the main host rock for gold mineralization and thus the age provides an upper constraint for mineral emplacement.The newly determined ages provide an upper constraint for the gold mineralization within this region of the Ashanti Belt. They also support recent structural studies that have interpreted that the Wassa mineralization is related to the Eoeburnean period, defined to have occurred between 2191 and 2158Ma (D1 event) prior to the main phase of gold mineralization. This new U–Pb age on the host rock provides an upper age limit to the Wassa mineralization of ca. 2191Ma and is compatible with the proposed Eoeburnean early mineralization model for the Wassa deposit. The age of the intrusion along with the location of the deposit in the Sefwi Group give a unique characteristic that distinguishes Wassa from the other gold deposits along the Ashanti belt which are believed to have been the result of a mineralizing event between ca. 2090 and 2070Ma.

Properties of water confined in hydroxyapatite nanopores as derived from molecular dynamics simulations

Bone tissue is characterized by nanopores inside the collagen-apatite matrix where fluid can exist and flow. The description of the fluid flow within the bone has however mostly relied on a macroscopic continuum mechanical treatment of the system, and, for this reason, the role of these nanopores has been largely overlooked. However, neglecting the nanoscopic behaviour of fluid within the bone volume could result in large errors in the overall description of the dynamics of fluid. In this work, we have investigated the nanoscopic origin of fluid motion by conducting atomistic molecular dynamics simulations of water confined between two parallel surfaces of hydroxyapatite (HAP), which is the main mineral phase of mammalian bone. The polarizable core–shell interatomic potential model used in this work to simulate the HAP–water system has been extensively assessed with respect to ab initio calculations and experimental data. The structural (pair distribution functions), dynamical (self-diffusion coefficients) and transport (shear viscosity coefficients) properties of confined water have been computed as a function of the size of the nanopore and the temperature of the system. Analysis of the results shows that the dynamical and transport properties of water are significantly affected by the confinement, which is explained in terms of the layering of water on the surface of HAP as a consequence of the molecular interactions between the water molecules and the calcium and phosphate ions at the surface. Using molecular dynamics simulations, we have also computed the slip length of water on the surface of HAP, the value of which has never been reported before.

Evaluating rare earth element (REE) mineralization mechanisms in Proterozoic gneiss, Music Valley, California

Research Article| July 01, 2015 Evaluating rare earth element (REE) mineralization mechanisms in Proterozoic gneiss, Music Valley, California S. Tyson McKinney; S. Tyson McKinney Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA Search for other works by this author on: GSW Google Scholar John M. Cottle; John M. Cottle † Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA †cottle@geol.ucsb.edu Search for other works by this author on: GSW Google Scholar Graham W. Lederer Graham W. Lederer Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA Search for other works by this author on: GSW Google Scholar Author and Article Information S. Tyson McKinney Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA John M. Cottle † Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA Graham W. Lederer Department of Earth Science, University of California, Santa Barbara, California 93106-9630, USA †cottle@geol.ucsb.edu Publisher: Geological Society of America Received: 16 Jul 2014 Revision Received: 15 Dec 2014 Accepted: 09 Feb 2015 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2015 Geological Society of America GSA Bulletin (2015) 127 (7-8): 1135–1152. https://doi.org/10.1130/B31165.1 Article history Received: 16 Jul 2014 Revision Received: 15 Dec 2014 Accepted: 09 Feb 2015 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation S. Tyson McKinney, John M. Cottle, Graham W. Lederer; Evaluating rare earth element (REE) mineralization mechanisms in Proterozoic gneiss, Music Valley, California. GSA Bulletin 2015;; 127 (7-8): 1135–1152. doi: https://doi.org/10.1130/B31165.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Monazite ([LREE]PO4, where LREE stands for light rare earth element) and xenotime (Y[HREE]PO4, where HREE stands for heavy rare earth element) occur in ore-grade concentrations within the Pinto Gneiss in the Music Valley region of southern California. However, both the age and petrogenesis of this potentially economically significant rare earth element (REE) deposit remain uncertain. New petrologic and geochronologic data enable assessment of the textural and temporal relationships between REE-bearing minerals and the host rock and development of a petrogenetic model for REE mineralization. Ore-forming monazite and xenotime are typically restricted to biotite folia within the host Pinto Gneiss, with greatest modal abundances occurring within a few meters of contacts between the host gneiss and a metadiorite intrusive unit, the latter of which is crosscut by pegmatite veins generated by partial melting of the Pinto Gneiss. Ore-forming monazite and xenotime preserve complex internal elemental zonation defining two distinct textures: (1) oscillatory zoning interpreted to represent primary crystallization, overprinted by (2) irregular embayed textures inferred to be the result of fluid-mediated dissolution re-precipitation reactions. The altered domains in monazite consist of primary monazite replaced by secondary monazite along with xenotime and uranothorite [(U,Th)SiO4] inclusions. Similarly, primary xenotime is replaced by secondary xenotime with monazite and uranothorite inclusions. Localized breakdown of monazite, anorthite, and biotite to apatite and allanite provides further evidence for postmineralization metasomatism of the ore bodies. In situ monazite and xenotime U-Pb geochronology constrains the timing of primary REE mineralization to ca. 1.71 Ga, consistent with zircon dates obtained from the Pinto Gneiss. Based on the similarity in ages of monazite, xenotime, and zircon in the Pinto Gneiss, along with relict “igneous” zoning in the ore-bearing phosphate minerals, REE mineralization is inferred to have occurred during crystallization of the igneous protolith to the Pinto Gneiss. Metadiorite emplacement at ca. 1.4 Ga and pegmatite genesis at ca. 165 Ma both postdate the main phase of REE mineralization but likely played a role in fluid-assisted alteration, breakdown, and partial resetting of monazite and xenotime U-Pb systematics in the Pinto Gneiss. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Influence of Basicity on High-Chromium Vanadium-Titanium Magnetite Sinter Properties, Productivity, and Mineralogy

The effect of basicity on high-chromium vanadium-titanium magnetite (V-Ti-Cr) sintering was studied via sintering pot tests. The sinter rate, yield, and productivity were calculated before determining sinter strength (TI) and reduction degradation index (RDI). Furthermore, the effect of basicity on V-Ti-Cr sinter mineralogy was clarified using metallographic microscopy, x-ray diffraction, and scanning electron microscopy-energy-dispersive x-ray spectroscopy. The results indicate that increasing basicity quickly increases the sintering rate from 25.4 mm min−1 to 28.9 mm min−1, yield from 75.3% to 87.2%, TI from 55.4% to 64.8%, and productivity from 1.83 t (m2 h)−1 to 1.94 t (m2 h)−1 before experiencing a slight drop. The V-Ti-Cr sinter shows complex mineral composition, with main mineral phases such as magnetite, hematite, silicate (dicalcium silicate, Ca-Fe olivine, glass), calcium and aluminum silico-ferrite (SFCA/SFCAI) and perovskite. Perovskite is notable because it lowers the V-Ti sinter strength and RDI. The well intergrowths between magnetite and SFCA/SFCAI, and the decrease in perovskite and secondary skeletal hematite are the key for improving TI and RDI. Finally, a comprehensive index was calculated, and the optimal V-Ti-Cr sinter basicity also for industrial application was 2.55.

The quartz-dioritic Hospitais intrusion (SW Iberian Massif) and its mafic microgranular enclaves — Evidence for mineral clustering

The Hospitais pluton is an elliptical body, with its long axis oriented WNW–ESE, that belongs to the Évora Massif (Iberian Variscan belt). This intrusion has a quartz-dioritic composition, with plagioclase, quartz, amphibole (hornblende, but locally also cummingtonite) and biotite as the main mineral phases. Mafic microgranular enclaves in the quartz–diorite show the same minerals as the host, but with a greater abundance of amphibole and lower proportions of felsic minerals, especially quartz. U–Pb zircon ages obtained in one sample of the quartz–diorite and one sample of a mafic microgranular enclave gave identical ages, within error, of ca. 337Ma. Geochemical data show that the quartz–diorite has a calc-alkaline signature with moderate enrichment in LILE/HFSE ratio (ThN/YN: 2.71–11.43) and clear negative Ti and Nb–Ta anomalies (ThN/NbN: 1.33–6.22). The composition of the enclaves shows that they do not represent direct melt compositions. Instead, their geochemical features (namely the abundances of Fe and Mn in variation diagrams and REE patterns in primitive mantle normalized diagrams) suggest that they correspond to mineral clustering formed during the previous crystallization stage of quartz-dioritic magma. Overlapping of mineral chemistry and Sr–Nd isotope compositions in the quartz–diorite and the enclaves provides further support to that conclusion. The values for [87Sr/86Sr]i and εNdi (calculated for 337Ma) in the quartz–diorite vary from 0.706147 to 0.706491 and from −1.87 to −3.22, respectively. This isotope composition may be explained either by differentiation of a mafic magma extracted from a mantle wedge enriched by long lasting subduction processes, or by mixing between a mafic magma from a depleted mantle source and a crustal melt. In the second case, the most likely source for the felsic component should be meta-igneous rocks, like the Lower Cambrian Alcáçovas orthogneisses that outcrop in neighbouring areas.

Geotechnical, chemical and mineralogical evaluation of lateritic soils in humid tropical area (Mfou, Central-Cameroon): Implications for road construction

Increased cost associated with the used of high quality materials have led to the need for local soils to be used in civil engineering works. In this paper, geo-chemical approaches coupled with conventional geotechnical techniques has been used to investigate vertical and lateral peculiar engineering index properties (EIP) of micaschist derived soils from Mfou, Central-Cameroon for their uses in road construction. The X-ray diffraction (XRD) analysis conducted on the soils indicated the absence of swelling clays. The main mineral phases were quartz, kaolinite, goethite, magnetite and chlorite. Geo-chemical results show that the investigated soils are “true laterites” made up of 41 wt.% of Fe2O3, 35 wt.% of SiO2, 21 wt.% of Al2O3, 1.17 wt.% of K2O and 0.05 wt.% of CaO. The results of geotechnical tests suggest that the upper clayey layer (UCL) and bottom mottled clayey layer (MCL) of the weathering profiles are poorly graded soils with EIP (fines particles (FP) of 61 and 63%, plasticity index (PI) of 30 and 31%, Californian Bearing Ratio (CBR) at 95% of 21 and 19%), which do not allow their use as raw materials in road construction whereas, intermediate nodular layer (INL) are well graded soils having EIP (FP of 26%, PI of 26% and CBR of 39%) that meet the specification required for sub-base materials for light traffic roads. The relatively high sesquioxyde present in these residual soils may act as cementing agent, thereby making the compacted soils relatively brittle. The direct shear test results show that the soils have high bearing capacity (cohesion of 62 Kpa and 27.2° angle of internal friction) making them to be useful in slope stability and shallow foundation design. The comparison of the studied soils with some lateritic soils in Sub-Saharan Africa indicates that i) genesis and climatic conditions are potentials factors that influence EIP of lateritic soils, ii) lateritic soils developed under semi-arid conditions exhibits EIP better than those developed under tropicaland sub-tropical conditions.

Low-grade magnesium oxide by-products for environmental solutions: Characterization and geochemical performance

The reutilization of the by-products from the calcination of natural magnesite for environmental solutions is conditioned by the availability of MgO, CaO and other compounds. In order to overcome their great heterogeneity, an exhaustive chemical and physical characterization is necessary in order to assess their potential applications. In this study, the acid neutralization capacity (ANC) test was used to categorize three types of by-products (LG-MgO, LG-D and LG-F), which mainly differed according to source ore and processing conditions. The experimental data concerning the leaching of Mg2+, Ca2+, Fe2+ and SO42− was corroborated with geochemical predictions using the modelling software Visual MINTEQ. Likewise, the main solubility-controlling mineral phases were also identified. According to the results, there is a buffer capacity within the pH8–10 range, mainly dominated by the neutralization of MgO/Mg(OH)2, equilibrium with a small contribution from the carbonate content at lower pH values. The release of sulphates showed a non-pH dependency attributed to the solubility of CaSO4 and elemental sulphur present in petcoke. For dust materials, leaching of Fe was minimal above pH6 owing to the insoluble nature of the Fe2O3/Fe3O4 pair. Accordingly, the by-products labeled as LG-D and LG-F are better suited for stabilizing solid wastes or wastewater that are acid while LG-MgO is more appropriate for alkaline residues such as contaminated soils. In both cases, a suitable pH range in which pH-dependent heavy metals and metalloids show minimum solubility can be obtained. The use of these by-products guarantees an environmentally friendly alkali reservoir for the long-term stabilization of heavy metals and metalloids at a very competitive price as a substitute for the widely used lime.

In situ U–Pb geochronology of xenotime and monazite from the Abra polymetallic deposit in the Capricorn Orogen, Australia: Dating hydrothermal mineralization and fluid flow in a long-lived crustal structure

The Proterozoic Capricorn Orogen is a major tectonic zone that records the assembly and subsequent reworking of the West Australian Craton. Recent seismic transects across the orogen have identified major crustal structures, some of which are spatially associated with hydrothermal mineral deposits. The sedimentary-rock-hosted Abra deposit, which is the largest base-metal accumulation in the Capricorn Orogen, is localized within the crust-cutting Lyons River–Quartzite Well fault zone. Robust radiometric dates for the timing of sediment deposition and hydrothermal mineralization are essential for understanding the geological history of this long-lived orogen and the processes that formed the ore deposits. In situ U–Pb SHRIMP geochronology of xenotime intergrown with magnetite–hematite–galena from the Abra ore zone yields a weighted mean 207Pb/206Pb age of 1594±10Ma (n=14, MSWD=2.6) which is interpreted to represent a period of xenotime growth during the hydrothermal activity responsible for the mineralization. An older coherent cluster within this group gives a weighted mean age of 1610±16Ma (n=5, MSWD=1.5), which constrains the depositional age of the lower Edmund Group sediments to between c. 1680Ma (maximum age of the basal Mt Augustus Sandstone) and c. 1610Ma. Authigenic monazite from the ore zone gives 207Pb/206Pb ages of 1375±14 (n=16, MSWD=0.99)Ma, interpreted to represent a hydrothermal event postdating the main phase of mineralization. Monazites in samples distal to mineralization yield weighted mean 207Pb/206Pb ages of 1221±14Ma (n=5, MSWD=1.04) and 995±18Ma (n=6, MSWD=1.3), interpreted as records of discrete episodes of hydrothermal fluid flow. Our results suggest that the Lyons River–Quartzite Well Fault, which is one of the principal structures in the Capricorn Orogen, has a long history of tectonic reactivation, spanning more than 600 million years and involving crustal extension and sediment deposition, hydrothermal mineralization and multiple episodes of fluid flow. Xenotime and monazite represent ideal chronometers for investigating the complex histories of hydrothermal mineralization and fluid flow in major crustal structures, and helping to unravel the geological evolution of intracratonic orogens.

Effects of Quicklime and Iron Tailings as Modifier on Composition and Properties of Steel Slag

Steel slag had lower activity and much lower hydration rate than cement. Quicklime and iron tailings were designed as modification agent to adjust the composition and properties of high temperature steel slag. The results show that quicklime as modifier can greatly increase the content of cementitious minerals in modified steel slag and also promote the decomposition of RO phases and transformation of MgO in RO phase to f-MgO. After high temperature modification with compound modifier of quicklime and iron tailings, steel slag shows the main mineral phases of C3S, C2F and MgFe2O4. The activity index of modified steel slag at 28 days reaches 95.5% when the steel slag is modified by 15% of the compound modifier with the ratio of quicklime to iron tailings equal to 2:1 at 1350 °C. Moreover, the sample with the modified steel slag exhibits the dense structure of hydration paste and the main hydration products of C-S-H gels and Ca(OH)2 crystals.

Sintering characteristics of CaO-rich municipal solid waste incineration fly ash through the addition of Si/Al-rich ash residues

Thermal treatment is a promising technology for the fast disposal of hazardous municipal solid waste incineration (MSWI) fly ash in China. However, fly ash produced in grate incinerator (GFA) is rich in CaO and chlorides, which promote the formation of toxic hexavalent chromium [Cr(VI)] and ash agglomeration during the thermal process, inhibiting the thermal disposal of GFA. In this study, sintering characteristics of CaO-rich GFA were improved by adding Si/Al-rich MSWI ash residues. According to the results, ash agglomeration was well suppressed during thermal treatment of the mixed ash. Si/Al/Fe-compounds competed with un-oxidized Cr-compounds to react with CaO and suppressed Cr(VI) formation. Meanwhile, chlorides in GFA facilitated heavy metal volatilization from added ashes to the secondary fly ash, favoring the recovery of these metals. Ca-aluminosilicates was found as the main mineral phase in the thermally treated mixed ash, which has attractive potential for applications. The formation of the aluminosilicates made the heavy metals that remained in the treated mixed ash more stable than the thermally treated single ash.

Preparation of K2CO3Using Potassic Syenite from East Qinling Mountains

1 Introduction Songxian at East Qinling mountains in China possesses more than 100 million tons potassic syenite with the average K2O content of 13%and the main mineral phase of K-feldspar which is a kind of potential potassium

Metal deposition in deep sediments from the Central and South Adriatic Sea

Geochemical analysis and trace element distribution were performed on the marine sediments from short cores (30 to 50 cm) from the Middle (Jabuka and Palagruža pits, depth 230 m and 170 m respectively) and South Adriatic Sea (depth 1030 m) and the Albanian offshore (50 m depth). The distribution and mineralogy of trace elements (As, Co, Cd, Cu Cr, Ni, Zn, Hg, and Pb) and major elements (Al, Ca and Mn) in the sediments is presented. Sediments are highly heterogeneous and consist of carbonate and detrital aluminosilicates. The main mineral phase is calcite, followed by quartz, feldspars, micas and clay minerals (smectite, chlorite, illite and kaolinite). The cores were dated using 137Cs. The cores from the South Adriatic Pit and Palagruža Sill gave estimated sedimentation rates of 1.8 mm y-1 and 3.1 mm y-1 in Jabuka Pit. Distributions of Ni and Cr showed that they can be used as tracers of sediment provenance along the southern part of the Eastern Adriatic Current. Calculated enrichment factors for Pb, Cd and Hg are highest in the top 2 cm of the cores. Mercury shows the highest degree of enrichment in 0-2 cm sediment intervals (the highest in the Albania core). Generally the estimated surface enrichment follows the order: Hg>Pb>Cd. No enrichment was found for Zn, Ni and Cr.

Recycling of low-silicon iron tailings in the production of lightweight aggregates

This paper reports the result of the investigation on manufacturing lightweight aggregate by the mixtures of the low-silicon iron tailings, fly ash and powdery quartz sand. The raw materials were characterized by chemical compositions, X-ray diffraction and particle size. The investigation was performed in a laboratory scale to assess the effects of the composition of the mixtures and the sintering conditions on the properties of the artificial lightweight aggregates. The effects of the composition of the mixtures and sintering temperatures on the bloating index, loose bulk density, apparent density, water absorption and compressive strength were determined. All the mixtures studied in the paper presented a bloating potential at high temperatures. The bloating index of all the samples is greater than 1, so all types of aggregates were expanded aggregates. The products obtained were lightweight aggregates. The microstructure and the phase composition of the lightweight aggregates were analyzed by scanning.electron microscopy (SEM) and X-ray diffraction (XRD). The main mineral phases of the products were hematite, quartz and anorthite, which were principally responsible for the mechanical strength of the aggregates. The analysis of microstructures with SEM revealed a vitrified matrix and an extended formation of isolated and closed pores.

Properties of masonry mortars manufactured with fine recycled concrete aggregates

This research evaluates the short- and long-term properties of masonry mortar manufactured with different replacement ratios of natural sand by fine recycled concrete aggregates. The recycled materials were collected from a recycling plant and after passage through a 4mm sieve, were directly used to make the mixtures, maintaining their original particle size distribution. A pozzolanic CEM-IV/A (V) 32.5N, with 29% fly ash in its compositions, was used at a 1:7 volumetric cement-to-aggregate ratio. Five mortars with different replacement ratios by volume were tested: 0%, 5%, 10%, 20% and 40%. The data were analysed using one-way analysis of variance to determine whether the “replacement ratio” had a statistically significant effect on the different fresh and hardened properties. DRX and electron microscope techniques were used to examine the morphologies and evolution of the main mineral phases over time during a curing period of 180days. The results proved that a replacement ratio of up to 40% is a viable alternative for producing environmentally friendly masonry mortar.

Métodos de reforço microestrutural da hidroxiapatita

A hidroxiapatita (HAp) é um fosfato de cálcio de fórmula química Ca10(PO4)6(OH)2, com relação molar Ca/P 1,67. Este material possui grande importância na tecnologia de biocerâmicas, por ser o constituinte principal da fase mineral de ossos e dentes humanos. Apresenta como algumas de suas aplicações a substituição de tecidos duros danificados, revestimento de próteses ortopédicas e de implantes e reparo de tecidos ósseos. A HAp apresenta resistência mecânica baixa e alta fragilidade o que tornam sua utilização restrita a áreas onde se exige pouco esforço mecânico. Uma das formas de melhorar essas propriedades é associá-la a outros materiais como zircônia, alumina, mulita, titânio e biovidro visando unir as propriedades desejáveis dos dois materiais, bem como pela adição de alguns íons. Este trabalho tem como objetivo descrever as propriedades resultantes da adição de diferentes materiais e íons às propriedades finais da hidroxiapatita. Observou-se que a grande maioria das abordagens de reforço mecânico utilizada atualmente é eficiente na melhoria da resistência à fratura e resistência à flexão e dureza. Verificou-se que apenas o reforço com titânio ainda não tem um efeito claramente elucidado sobre o comportamento mecânico da HAp. A melhora do comportamento mecânico devido à adição do reforço é dependente de fatores como temperatura de sinterização, quantidade de reforço utilizada, ausência de mudanças estruturais indesejáveis, bem como a ausência de outras fases que sejam deletérias às propriedades finais dos materiais produzidos.

Characterization of mineralogy and surface zeta potential of atmospheric dust fall in northwest China

The mineralogy characterization of dust fall in atmosphere is important in understanding and improving air quality. In this paper, dust fall samples were collected in the suburb of four areas of northwest China during April to May 2012. The size distribution, mineral phase and composition, morphology, and surface charge of dust fall were investigated, respectively, by particle size analyzer, X-ray powder diffraction spectrometer (XRD), scanning electron microscopy (SEM), and zeta potential analyzer. The average volume size of dust fall was from 59.17 to 62.88 μm, and the dust fall in Tuoketuo County of Inner Mongolia Autonomous Region had the finest particles (59.17 μm), while the number percentage of fine particulate matter (<1.0 μm) in dusts was about 88.36 % of total particles. The main minerals of dust fall samples are composed of quartz, calcilte, muscotive, albite, clinochlore, and gypsum. And four dust fall samples had the same main mineral phase. Minerals of surface soil were identified as an important source of atmospheric dust fall. The morphological of the atmospheric dust fall presented irregular square, sphere, agglomerate elongated particles, and granular aggregates. Zeta potentials of four dust fall samples were negative in tested pH range. Moreover, their zeta potentials decreased with increasing pH of the solution. The surface charge of dust fall was strongly affected by the quantity of carbonate minerals (calcite and dolomite) in samples. The simulated zeta potential result of multimineral dusts indicated that the magnitude and tendencies of dust’s zeta potential were dominated by the main mineral phase in dust fall.

Characteristics of the fired bricks with low-silicon iron tailings

This paper studies the feasibility of utilizing low-silicon iron tailings for production of eco-friendly fired bricks. In order to improve the bricks quality, we add different proportions of fly ash to the raw materials. Compositions were prepared with additions of 5wt.%, 10wt.%, 15wt.% and 20wt.% fly ash in tailings. Initially, the iron tailings and fly ash were characterized by their chemical compositions, X-ray diffraction and particle size. The brick pieces were prepared and fired, and then the sintering shrinkage, weight loss on ignition, water absorption, apparent porosity, compressive strength, phase compositions and microstructure of final fired samples were investigated. Results indicated that the firing temperature and fly ash proportion significantly influenced the bricks properties. With different proportions of fly ash added to the bricks, the physical properties at temperatures from 900°C to 1000°C were well conformed to Chinese Fired Common Bricks Standard (GB/T5101-2003). The main mineral phases of the product were hematite, quartz, anorthite, diopside and anhydrite, which were principally responsible for the mechanical strength of bricks.

Weathering assessment in the Achala Batholith of the Sierra de Comechingones, Córdoba, central Argentina. I: Granite–regolith fractionation

Weathering assessment in a weathering-limited environment is a difficult task because a significant proportion of the regolith has been removed by tectonically-induced denudation. In such an environment, the remnants of the altered mineral debris must be studied with care in order to attain a meaningful picture of the rate and intensity of ongoing weathering. A monolithologic (i.e., granite), small (~2km2), and mountainous (~1500m elevation) drainage basin in the Sierras de Comechingones (31°54′07″S 64°45′28″W–31°53′11″S 64°44′16″W, Córdoba, central Argentina) was selected as a pilot area to survey the nature of weathering in a weathering-limited erosional setting, and a semiarid climatic regime. A relatively thin-layered, coarse-grained regolith and scattered sediment (i.e., fine-grained regolith) that had accumulated in valleys and topographic depressions were analyzed. The most abundantly identified clay mineral in the regolith is illite followed by kaolinite>smectite. Smectite seems to be the only clay mineral clearly associated with weathering. Petrographic observations and geochemical analyses, supported by statistical tests, define chemical weathering as incipient. Petrography indicates that plagioclase and biotite are the main mineral phases affected by alteration, which is more intense in the fine-grained regolith. Coarse- and fine-grained regoliths are chemically similar, among them and with the country rock, with statistically significant losses in the fine fraction of MgO, MnO and P2O5. Depletions of trace elements and REE, which are best explained by sorting than by actual rock alteration, are not statistically significant. Ternary diagrams reveal that the masses of Al2O3, CaO, Na2O and K2O were not significantly altered during weathering and transportation, and that regolith samples correspond to a coarse residue relatively enriched in feldspars (and quartz), where the mud-fraction (with high clay mineral contents) has been removed from the drainage basin by high-energy processes.

Randall's plaque as the origin of calcium oxalate kidney stones.

Eight decades ago, Alexander Randall identified calcium phosphate deposits at the tip of renal papillae as the origin of renal calculi. The awareness that these "Randall's plaque" promote renal stone formation has been amplified during the past years by the development of endoscopic procedures allowing the in situ visualization of these plaques. Recent studies based upon kidney biopsies evidenced that apatite deposits at the origin of these plaque originate from the basement membranes of thin loops of Henle and then spread in the surrounding interstitium. In addition, scanning electron microscopy examination of calcium oxalate stones developed on Randall's plaque evidenced that plaque may also be made of tubules obstructed by calcium phosphate plugs. Hypercalciuria has been associated to Randall's plaque formation. However, several additional mechanisms may be involved resulting in increased tissular calcium phosphate supersaturation and the role of macromolecules in plaque formation remains elusive. At last, apatite crystals are the main mineral phase identified in plaques, but other calcium phosphates and various chemical species such as purines have been evidenced, revealing thereby that several mechanisms may be responsible for plaque formation.

Mineralogical characterization of the Hakkari nonsulfide Zn(Pb) deposit (Turkey): The benefits of QEMSCAN®

The development of relatively simple and low-cost processing technologies such as solvent-extraction, AmmLeach®, leach/solvent extraction/electrowinning and pyrometallurgy, combined with the increase in Zn prices, resulted in an increase in the study and exploration of nonsulfide Zn(Pb) deposits. The Hakkari deposit is an example of a supergene nonsulfide Zn(Pb) deposit located in Southeast Turkey, hosted in brecciated Jurassic limestone. The ore concentrations, mainly consisting of oxidized Zn minerals (smithsonite and hemimorphite) were examined in this study using QEMSCAN®. The formulation of a Species Identification File (SIP) was necessary to discriminate the mineral species. QEMSCAN® analysis allowed detailed mineralogical characterization of several Hakkari drill core samples, building on, and adding to previous studies of the deposit. In particular, the modal mineralogy for the ore and gangue minerals, and mineral association and spatial distribution data of the economic minerals provided information for the advanced exploration phase of the deposit, which could influence the feasibility study and ore processing options. The results show that smithsonite is the main ore mineral, occurring in two generations: one (FeO and PbO bearing) replaces sphalerite and host carbonates, and another (CaO-bearing) is concretionary in cavities. Hemimorphite occurs in cavities or replaces smithsonite in veinlets. Fe-(hydr)oxides can be enriched in Zn, Pb, As and SiO2. Mn–Fe-(hydr)oxides (Pb≫Zn enriched) are rare. Remnant sulfides have also been detected. The QEMSCAN® study has confirmed the main mineral phases found in previous studies, but identified other phases not previously detected (e.g. minerals in trace amounts such as sauconite), being also able to distinguish and quantify impure phases (e.g. Zn-dolomite, Cd-calcite), and identify amorphous phases [pyrite/Fe-(hydr)oxides/jarosite mix] that XRD found challenging. Not detecting the detrimental minerals/elements may result in processing problems, penalties at the smelter, poor metal quality, and environmental damage. Thus the use of QEMSCAN® technology on this type of deposit is beneficial for both exploration and potential processing, provided that careful attention is paid to the complex mineralogy and limitation of the analysis technique.