Quartz Layers Research Articles

Zinc oxide aluminum doped slabs for heat-eliminating coatings of spacecrafts

This paper discuss a possibility for using a thin-film functional coating based on transparent conducting thin films of aluminum doped zinc oxide (AZO) as a heat-eliminating material on the surface of a spacecraft. The structure of the functional coating has been chosen taking into account the plasmonic properties of AZO and silver and represents the AZO slabs with embedded silver nanoparticles deposited on AZO layer and AZO slabs with embedded silver nanoparticles deposited on thin film fused quartz layer. The paper contains COMSOL finite element simulations of the scattering cross section for thermal radiation in the IR band in the case the investigated coating deposited on a reflective aluminum film, and absorption cross section in the near UV and visible spectral bands when the coating deposited on silicon solar panels. The calculations demonstrate an increase in the scattering cross-section in the spectral band of blackbody radiation by several orders of magnitude, with the maximum in the scattering spectrum of the AZO slabs/ AZO /Al structure corresponding to the maximum intensity of the blackbody thermal radiation, which has been heated to 100 °C in the case the lattice period of the AZO slabs is equal to the resonance wavelength for AZO. Also an increase in the absorption cross-section of AZO slabs/ AZO /Si structure in visible spectral band is observed corresponding to plasmon absorption of embedded silver nanoparticles.

Fluid‐Assisted Strain Localization in Quartz at the Brittle/Ductile Transition

AbstractA mylonitic quartzite with conjugate and synthetic shear bands was investigated by Electron Backscatter Diffraction and optical microscopy to obtain insights on recrystallization mechanisms and strain localization in quartz at plastic to semibrittle conditions close to the brittle‐ductile transition. The mylonitic quartzite deformed during late Miocene thrusting coeval with contact metamorphism in the high‐strain domains of the Calamita Schists (Elba Island, Italy). Mylonitic deformation occurred from amphibolite to lower greenschist facies conditions during cooling of the aureole. Dynamic recrystallization, dominated by the activity of dislocation creep by prism <a> slip, produced recrystallized quartz layers mantling relic large quartz porphyroclasts. Under decreasing temperature and fluid‐rich conditions, quartz porphyroclasts acted as relatively rigid bodies and fractured along synthetic and conjugate C′ shear bands. Shear bands developed along kinematically favored orientations, just locally assisted by weak crystallographic planes in quartz. Fracturing along shear bands was assisted by cataclasis and fluid infiltration enhancing fracture propagation and healing by recrystallization and authigenesis of new quartz and phyllosilicate grains. The process enhanced the propagation of and strain localization in shear bands, with the development of bands of weak phyllosilicates. Furthermore, we observed the development of a c axis preferred orientation (CPO) related to dissolution and precipitation of new grains with their c axis oriented parallel to shear bands. This study highlights the importance of the interplay between brittle and crystal‐plastic processes and fluid ingress in the semibrittle regime to understand deformation partitioning and strain localization.

Preferred Orientation of Quartz in Metamorphic Rocks from the Bergell Alps

Crystal preferred orientation of 47 samples of quartzite and eight samples of associated marbles from the Bergell Alps have been analyzed with time-of-flight neutron diffraction and EBSD. The results show a clear distinction of texture types for quartzites transformed from Triassic sandstones and quartz layers in gneiss. Textures of Triassic quartzites are overall weak and display a maximum of c-axes perpendicular to the foliation or a crossed girdle perpendicular to the lineation. Pole figures for positive rhombs {10 1 ¯ 1} show a maximum perpendicular to the foliation and negative rhombs {01 1 ¯ 1} generally display a minimum. Based on polycrystal plasticity models this texture type can be attributed to a combination of basal and rhombohedral slip. Asymmetry of the distributions is attributed to simple shear and local strain heterogeneities. The relatively weak texture is partially caused by muscovite limiting dislocation motion and grain growth, as well as adjacent layers of marble that accommodate significant strain. Most quartz layers in gneiss, including mylonites, display a texture with a-axes parallel to the lineation and a c-axis maximum in the intermediate fabric direction. This texture type can be attributed to dominant prismatic slip. Many samples are recrystallized and recrystallization appears to strengthen the deformation texture. The study shows good agreement of neutron diffraction and EBSD. Neutron diffraction data average over larger volumes and maximum pole densities are generally lower and more representative for the bulk material. With EBSD the microstructure and mechanical twinning can be quantified.

Investigation of landslide zones with geoelectric methods for disaster mitigation in Pamekasan

Madura is one of the islands in Indonesia. This island had a landslide in 2016. The occurrence of this landslide resulted in the Madura community being mentally and financially burdened. The results of this study were that the soil layer consists of six types of soil, namely clay, clay, sandstone, sandstone with clay stones, quartz and limestone. Crossing types of clay and sandstone was the top layer with an average thickness of ± 1.2 m-6 m. quartz and limestone layers were bed rock rocks that were in depths of more than 10 m. While the slip plane was a field that becomes the basis of moving the ground mass. The soil layer which is the slip plane was clay and sandstone with slope 8°-25°. This soil layer has a low resistivity with a depth of ± 9.5 m - 11.5 m. The higher the slope of a layer, the faster the time needed for the avalanche to occur. For the evacuation route the batumarmar was heading north because the landslide direction was heading west and east, the springs were heading eastward because the landslide direction was heading west, proppo was heading north because the landslide direction was heading north to the east and south to the west, go east and west because the landslide was heading west and east. The results of the Community outreach on our research were the increasing readiness for landslides.

Deformation of feldspar at greenschist facies conditions – the record of mylonitic pegmatites from the Pfunderer Mountains, Eastern Alps

Abstract. Deformation microstructures of albitic plagioclase and K-feldspar were investigated in mylonitic pegmatites from the Austroalpine basement south of the western Tauern Window by polarized light microscopy, electron microscopy and electron backscatter diffraction to evaluate feldspar deformation mechanisms at greenschist facies conditions. The main mylonitic characteristics are alternating almost monophase quartz and albite layers, surrounding porphyroclasts of deformed feldspar and tourmaline. The dominant deformation microstructures of K-feldspar porphyroclasts are intragranular fractures at a high angle to the stretching lineation. The fractures are healed or sealed by polyphase aggregates of albite, K-feldspar, quartz and mica, which also occur along intragranular fractures of tourmaline and strain shadows around other porphyroclasts. These polyphase aggregates indicate dissolution–precipitation creep. K-feldspar porphyroclasts are partly replaced by albite characterized by a cuspate interface. This replacement is interpreted to take place by interface-coupled dissolution–precipitation driven by a solubility difference between K-feldspar and albite. Albite porphyroclasts are replaced at boundaries parallel to the foliation by fine-grained monophase albite aggregates of small strain-free new grains mixed with deformed fragments. Dislocation glide is indicated by bent and twinned albite porphyroclasts with internal misorientation. An indication of effective dislocation climb with dynamic recovery, for example, by the presence of subgrains, is systematically missing. We interpret the grain size reduction of albite to be the result of coupled dislocation glide and fracturing (low-temperature plasticity). Subsequent growth is by a combination of strain-induced grain boundary migration and formation of growth rims, resulting in an aspect ratio of albite with the long axis within the foliation. This strain-induced replacement by nucleation (associated dislocation glide and microfracturing) and subsequent growth is suggested to result in the observed monophase albite layers, probably together with granular flow. The associated quartz layers show characteristics of dislocation creep by the presence of subgrains, undulatory extinction and sutured grain boundaries. We identified two endmember matrix microstructures: (i) alternating layers of a few hundred micrometres' width, with isometric, fine-grained feldspar (on average 15 µm in diameter) and coarse-grained quartz (a few hundred micrometres in diameter), representing lower strain compared to (ii) alternating thin layers of some tens of micrometres' width composed of fine-grained quartz (<20 µm in diameter) and coarse elongated albite grains (long axis of a few tens of micrometres) defining the foliation, respectively. Our observations indicate that grain size reduction by strain-induced replacement of albite (associated dislocation glide and microfracturing) followed by growth and granular flow simultaneous with dislocation creep of quartz are playing the dominating role in formation of the mylonitic microstructure.

Myrmekite and strain weakening in granitoid mylonites

Abstract. At mid-crustal conditions, deformation of feldspar is mainly accommodated by a combination of fracturing, dissolution–precipitation, and reaction-weakening mechanisms. In particular, K-feldspar is reaction-weakened by the formation of strain-induced myrmekite – a fine-grained symplectite of plagioclase and quartz. Here we use electron backscattered diffraction to (i) investigate the microstructure of a granodiorite mylonite, developed at ∼ 450 °C during cooling of the Rieserferner pluton (Eastern Alps); and (ii) assess the microstructural processes and the weakening associated with myrmekite development. Our analysis shows that the crystallographic orientation of plagioclase in pristine myrmekite was controlled by that of the replaced K-feldspar. Myrmekite nucleation resulted in both grain-size reduction and anti-clustered phase mixing by heterogeneous nucleation of quartz and plagioclase. The fine grain size of sheared myrmekite promoted grain-size-sensitive creep mechanisms including fluid-assisted grain boundary sliding in plagioclase, coupled with heterogeneous nucleation of quartz within creep cavitation pores. Flow laws, calculated for monomineralic quartz, feldspar, and quartz + plagioclase aggregates (sheared myrmekite) during deformation at 450 °C, show that grain-size-sensitive creep in sheared myrmekite accommodated strain rates several orders of magnitude higher than monomineralic quartz layers deforming by dislocation creep. Therefore, diffusion creep and grain-size-sensitive processes contributed significantly to bulk rock weakening during mylonitization. Our results have implications for modelling the rheology of the felsic middle crust.

Characterization of nodular structure in shale with a proposed growth model in the Sitakund anticline, Bengal basin, Bangladesh

Nodular shales commonly occur in silty shales near the axial (proximity to core) regions of anticlinal structures (Sitakund anticline, Sitapahar anticline, Patharia structure, and Mirinja anticline) of eastern fold belt of Bangladesh. Stratigraphically, they are pronounced in the Surma group of Neogene succession. In many outcrops, these are found in the incompetent beds bounded by the competent ones. An initial investigation has been followed by comprehensive petrographical and geochemical studies including thin section microscopy, laser particle size analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) to characterize the nodular shale of Sitakund structure. From laser diffraction analysis, it is evident that nodular shales are silty in nature containing approximately 60% silt (mainly quartz). XRD pattern shows that nodular shale contains quartz, feldspar, illite, kaolinite, chlorite, and expandable mixed layer clay mineral including minor amount of calcite and siderite. Geochemical analysis shows that there is no significant variation from host rocks in context of major and trace element concentration. Microcracks within the quartz grains and squeezed clay minerals were observed in some nodular shale samples correlating the influence of regional tectonics and local structural dynamics in the axial regime of the anticline. Projection of 15 nodular shale long axes in outcrop shows their orientation in NNW-SSE that is parallel to the fold axis. The study suggests a new name of conventionally called nodular shales based on their origin, composition, and occurrence. The proposed name is “Clay Cabbage”. Diagenesis involving the conversion of montmorillonite to illite clay through a mixed layer illite/montmorillonite along with the regional and local tectonics is responsible for the formation of nodular shale. A new model naming as “Tectono-Diagenetic (TD) Model” is proposed in this study concerning the origin of nodular shale. Fluid pressure during diagenesis along with axial deformation due to folding produces hemispherical bodies by brittle and plastic flow that initiates the core of nodular shale at greater depth. Spiral geometry of the body is attained through several deformation stages with the evolution of the folded pattern.

Organic matter, mineral composition, pore size, and gas sorption capacity of lacustrine mudstones: Implications for the shale oil and gas exploration in the Dongying depression, eastern China

Because clay minerals and pore-size distribution are important for oil and gas accumulation in lacustrine mudstone reservoirs, this study aimed to characterize the pore-size distribution in lacustrine mudstone, reveal the importance of clay minerals in gas sorption capacity (GSC), provide insights into the primary GSC controls for lacustrine mudstones, and discuss the shale oil and gas resource potential and possible risks in their future production. A total of 256 core samples from the lower Paleogene sequence of the Dongying depression in the Bohai Bay Basin in China were analyzed to determine organic richness and hydrocarbon generation potential. A series of analyses was conducted on a suite of 28 mudstone samples from the S121 well to investigate the mineral composition, pore-size distribution, and primary controls on GSC. Scanning electron microscopy and x-ray diffraction were used to observe the microscopic characteristics and identify various minerals. Nitrogen adsorption experiments at low temperatures and a methane isothermal adsorption test were conducted to study the pore sizes and gas adsorption capacities. Experimental results show that the majority of the samples were rich in type II and I kerogen with moderate to high hydrocarbon generation potential and are thermally mature in the main oil window. The contents of illite and mixed layer illite–smectite (I–S) are high (>40%) in these lacustrine mudstones. The pores were mainly thin, long, and bottleneck shaped and dominated by type IV and H2 hysteresis loop characteristics. The abundance of quartz, feldspar, illite, and mixed layer I–S all presented a positive correlation with their Brunauer–Emmett–Teller surface area and total pore volume, whereas the abundance of carbonate minerals (dominated by calcite) showed a negative correlation. The volume of micropores and clay minerals were the main factors controlling GSCs. The results highlight the importance of clay minerals, including the illite and mixed layer I–S, in the lacustrine mudstones because of their considerable GSC. High content of illite and mixed layer I–S in lacustrine mudstone is in favor of gas storage, whereas at the same time, it is not conducive to shale gas development because of its reducing the brittleness of shale. The Paleogene of Dongying depression has shale oil and gas resources; however, several key geological factors, including pore-size distributions, pore diameters, oil density, and low brittleness, may pose risks in shale oil and gas development.

Multichannel tunable omnidirectional photonic band gaps of 1D ternary photonic crystal containing magnetized cold plasma

By using the transfer matrix method, theoretical investigations have been carried out in the microwave region to study the reflection properties of multichannel tunable omnidirectional photonic bandgaps (OPBGs) based on the magneto-optic Faraday effect. The proposed one dimensional ternary plasma photonic crystal consists of alternate layers of quartz, magnetized cold plasma (MCP), and air. In the absence of an external magnetic field, the proposed structure possesses two OPBGs induced by Bragg scattering and is strongly dependent on the incident angle, the polarization of the incident light, and the lattice constant unlike to the single-negative gap and zero-n¯ gap. Next, the reflection properties of OPBGs have been made tunable by the application of external magnetic field under right hand and left hand polarization configurations. The results of this manuscript may be utilized for the development of a new kind of tunable omnidirectional band stop filter with ability to completely stop single to multiple bands (called channels) of microwave frequencies in the presence of external static magnetic field under left-hand polarization and right-hand polarization configurations, respectively. Moreover, outcomes of this study open a promising way to design tunable magneto-optical devices, omnidirectional total reflectors, and planar waveguides of high Q microcavities as a result of evanescent fields in the MCP layer to allow propagation of light.

The effect of pyrite particle size on the electrochemical dissolution of gold during cyanidation

Pyrite is considered as the most common sulphide mineral that carries gold in refractory gold ores. In these ores, pyrite can be found in different particle sizes. Following flotation process, the flotation tailings is sent to the cyanidation circuit for gold extraction that may contain appreciable amounts of pyrite. Until now, the effect of pyrite on gold dissolution was reported to be either positive or negative in the open literature. This current research examines the effect of particle size and amount of pyrite on gold dissolution in a packed bed leach reactor (PBLR). Electrochemical characterization as a function of pyrite particle size on gold dissolution was tested. It was found that pyrite (4g) has positive galvanic effect on gold dissolution especially in the presence of fine particles, −106μm (i.e., 54% Au in the absence of pyrite vs. 95% with +20–53μm pyrite). On the other hand, gold dissolution showed a sharp decrease when particle size was coarser than +106μm. Highest gold extraction, 98%, was achieved when gold particles are in contact with +75–106μm pyrite particles. When the pyrite amount was doubled (8g of +75–106μm), gold dissolution was decreased to 35% due to the partial passivation of gold. If the pyrite amount were reduced by half (2g of +75–106μm), gold dissolution increased by 30% as compared to the case without pyrite. Different scenarios were also considered regarding to activation and passivation of gold. For instance, when gold was split and dispersed equally within the pyrite layer and within the adjacent quartz layer, gold dissolution was found to be around 35%, suggesting a negative effect of released species from pyrite. Cyclic voltammetry and potentiodynamic polarization findings are in line with the cyanide leaching results. The shift in open circuit potential in presence of pyrite is in support of observed leach kinetics. SEM-EDS results have confirmed the decrease in gold dissolution in the presence of coarse particles. These findings have revealed that pyrite particle size and its amount have significant impact on gold dissolution.

Petrogenesis, detrital zircon SHRIMP U-Pb geochronology, and tectonic implications of the Upper Paleoproterozoic Seosan iron formation, western Gyeonggi Massif, Korea

This study involves investigations on the Upper Paleoproterozoic iron formation (viz., Seosan iron formation) from the Seosan Group, Gyeonggi Massif of the southwestern Korean Peninsula. It occurs as thin banded layers within meta-arkosic sandstone, formed by alternating processes of chemical (hydrothermal) and detrital depositions under a shallow marine environment. It mainly consists of alternating layers of iron oxides, mostly hematite, and quartz. Minor amounts of magnetite surrounded by muscovite, clinopyroxene and amphibole indicate hydrothermal alteration since its formation. Meta-arkosic sandstone is composed of recrystallized or porphyroclastic quartz and microcline, with small amounts of hematite and pyrite clusters. The Seosan iron formation has high contents of total Fe2O3 and SiO2 with positive Eu anomalies similar to those of other Precambrian banded iron formations, and its formation is clearly related to hydrothermal alteration since its deposition. Detrital zircon SHRIMP U-Pb geochronology data from a meta-arkosic sandstone (SN-1) and an iron formation (SN-2) show mainly two age groups of ca. 2.5 Ga and ca. 1.9–1.75 Ga. This together with intrusion age of the granite gneiss (ca. 1.70–1.65 Ga) clearly indicate that the iron formations were deposited during the Upper Paleoproterozoic. The dominant Paleoproterozoic detrital zircon bimodal age peaks preserved in the Seosan iron formation compare well with those from the South China Craton sedimentary basins, reflecting global tectonic events related to the Columbia supercontinent in East Asia.

Hydrodynamic model of a dielectric-barrier discharge in pure chlorine

A one-dimensional hydrodynamic model of a dielectric-barrier discharge (DBD) in pure chlorine is developed, and the properties of the discharge are modeled. The discharge is excited in an 8-mm-long discharge gap between 2-mm-thick dielectric quartz layers covering metal electrodes. The DBD spatiotemporal characteristics at gas pressures of 15–100 Torr are modeled for the case in which a 100-kHz harmonic voltage with an amplitude of 8 kV is applied to the electrodes. The average power density deposited in the discharge over one voltage period is 2.5–5.8 W/cm3. It is shown that ions and electrons absorb about 95 and 5% of the discharge power, respectively. In this case, from 67 to 97% of the power absorbed by electrons is spent on the dissociation and ionization of Cl2 molecules. Two phases can be distinguished in the discharge dynamics: the active (multispike) phase, which follows the breakdown of the discharge gap, and the passive phase. The active phase is characterized by the presence of multiple current spikes, a relatively high current, small surface charge density on the dielectrics, and large voltage drop across the discharge gap. The passive phase (with no current spikes) is characterized by a low current, large surface charge density on the dielectrics, and small voltage drop across the discharge gap. The peak current density in the spikes at all pressures is about 4 mA/cm2. In the multispike phase, there are distinct space charge sheaths with thicknesses of 1.5–1.8 mm and a mean electron energy of 4.3–7 eV and the central region of quasineutral plasma with a weak electric field and a mean electron energy of 0.8–3 eV. The degree of ionization of chlorine molecules in the discharge is ~0.02% at a pressure of 15 Torr and ~0.01% at 100 Torr. The DBD plasma is electronegative due to the fast attachment of electrons to chlorine atoms: e + Cl2 → Cl + Cl–. The most abundant charged particles are Cl 2 + and Cl− ions, and the degree of ionization during current spikes in the active phase is (4.1–5.5) × 10–7. The mechanism of discharge sustainment is analyzed. The appearance of a series of current spikes in the active phase of the discharge is explained.

The Influence of Heterogeneity in Wettability and Pore Structure in CO2 Geological Sequestration: A Pore-scale Study

Owing to the complexity of geological formation, a detailed understanding of all transportation phenomenon of CO2/water in porous media occurring in CGS is not yet gained. Heterogeneity in wettability and pore structure exists in mostly natural geological formation which has been proof that gives strong effects on porous media flow. Since macroscopic transportation phenomenon in porous media are always determined by pore-scale properties, investigation on heterogeneity at pore-scale gives the most fundamental influence mechanisms of heterogeneity in wettability and pore structure. In this study, we reported a pore-scale study on the influence of heterogeneity in wettability and pore structure in vertical CO2/water displacement experiments using a micro-CT machine. Two stratified sand packs, BZ06+BZ02, quarz+dolomite, were employed in displacement experiments. The experiment results indicate that, CO2 saturation pattern shows a big difference between dolomite layer and quartz layer, CO2 enters more pore spaces and owns higher CO2 saturation in dolomite layer than quartz layer in drainage. While in glass beads pack, it is noticeable that the capillary barrier of BZ02 layer significantly affects CO2 percolation process. CO2 occupied little void volume of BZ02 porous matrix. In imbibition, residual CO2 was mainly trapped in more wetting quartz layer in quartz+dolomite pack, and more compact layer in BZ06+BZ02 pack.

Petrology and geochemistry of REE-rich Mafé banded iron formations (Bafia group, Cameroon)

Archaean–Paleoproterozoic foliated amphibole-gneisses and migmatites interstratified with amphibolites, pyroxeno-amphibolites and REE-rich banded-iron formations outcrop at Mafé, Ndikinimeki area. The foliation is nearly vertical due to tight folds. Flat-lying quartz-rich mica schists and quartzites, likely of Pan-African age, partly cover the formations. Among the Mafé BIFs, the oxide BIF facies shows white layers of quartz and black layers of magnetite and accessory hematite, whereas the silicate BIF facies is made up of thin discontinuous quartz layers alternating with larger garnet (almandine–spessartine)+chamosite+ilmenite±Fe-talc layers. REE-rich oxide BIFs compositions are close to the East Pacific Rise (EPR) hydrothermal deposit; silicate BIFs plot midway between EPR and the associated amphibolite, accounting for a contamination by volcanic materials, in addition to the hydrothermal influence during their oceanic deposition. The association of an oceanic setting with alkaline and tholeiitic magmatism is typical of the Algoma-type BIF deposit. The REE-rich BIFs indices recorded at Mafé are interpreted as resulting from an Archaean–Paleoproterozoic mineralization.

Enrichment of iron ores by folding in the BIF‐hosted deposit: A case study from the Archean Qian'an iron deposit, North China Craton

As part of the Archean greenstone belt, the Qian'an iron deposit is a typical banded iron formation (BIF)‐hosted iron deposit in the North China Craton. The BIF iron orebodies, together with Archean host rocks, have experienced multiphase metamorphism and plastic deformation. Folds, especially large‐scale synclines, played the most important role in the enrichment and preservation of the Qian'an BIF iron deposit. Exploration and mining reveal that orebodies in the deposit are located in the cores of folds. Structural analysis of the BIF ores suggests that rocks and minerals show obvious plasticity and tend to form types II and III folds of the Ramsay fold classification in the early stage of high temperature deformations (granulite facies), whereas type Ib parallel folds and sometimes type Ic folds are widely developed in the late stage of relatively low temperature deformations (e.g., amphibolite facies). Hand specimens of different types of folded iron ores are investigated with respect to their thickening coefficients, dimensional fabrics and lattice‐preferred orientation fabrics, to find out the characteristics and variation of folded layers, and the importance of iron enrichment during formation of different types of folds. Our studies prove that folding in Qian'an ore deposit occurred under different deformation conditions and thus led to various degrees of enrichment of magnetite. Among them, the type III folds have the most important significance to the enrichment of magnetite. Thickening coefficient analysis shows that the thicknesses of the quartz layers remain relatively constant, and those of the magnetite layers vary evidently during folding. It is concluded that the quartz‐rich layers dominate the deformation as competent layers, and magnetite‐rich layers as relatively weak and passive layers. In addition, the EBSD (Electron Back‐Scattered Diffraction) technique is applied to analyze the dimensional and crystallographic fabrics of both quartz and magnetite grains in folded BIF ores. The quartz <0001> and magnetite <001> fabrics of samples from the cores and limbs of the different types of folds show complex orientation patterns related to plastic deformation superposition. It is shown that the EBSD analysis is a very effective technique analyzing dimensional and crystallographic fabrics of deformed iron ores.

Impact of silver sulphide on gold cyanidation with conductive sulphide minerals

Gold is mostly found in metallic form, while silver exists in various mineral forms. Pyrite, chalcopyrite, sphalerite, and stibnite were the sulphidic minerals investigated for the effect of silver sulphide on gold cyanidation. Four sets of mineral systems, pyrite‐silica, chalcopyrite‐silica, sphalerite‐silica, and stibnite‐silica, were established to investigate the effect of silver sulphide. Silver sulphide addition promoted gold dissolution for the pyrite‐silica and sphalerite‐silica systems. The gold dissolution was retarded with the chalcopyrite‐silica and stibnite‐silica systems, irrespective of the dispersion of gold and silver sulphide in the mineral as well as in the quartz layer. The surface characterization of the gold particles was attempted by using X‐ray photoelectron spectroscopy (XPS) in order to identify the surface obstructing species. XPS analysis showed that the passivation layers of silver sulphide (Ag2S), Cu2O/Cu(OH)2, and antimony oxide (Sb2O5) might form on the surface of goldparticles by the simultaneous dissolution of silver sulphide as well as sulphide minerals, resulting in the retardation of gold dissolution.

Screen Printed Electromechanical Micro-total Analysis System (μtas) for Sensitive and Rapid Detection of Infectious Diseases

The main objective of this article is to demonstrate by performing simulation measurements of biosensor that can detect the presence of pathogens through simultaneous mass and impedance techniques. This biosensor merges two biosensing techniques namely resonant frequency measurements and electrochemical impedance spectroscopy (EIS) on a single biosensor. Parallel measurements provide better sensitivities, have higher diagnostics accuracy and reduce the risk of false positives. Low cost, high resolution screen printing technology was used to fabricate the microelectromechanical array of μTAS on flexible piezoelectric substrates. The basic biosensor framework includes a substrate that highly sensitive sensor like thickness shear mode and immunosensor can be fabricated using quartz crystal lattice that integrated with electrochemical sensor [1]. The quartz crystal microbalance is a label free technique, which minimizes interference with the interaction being studied. A piezoelectric device is portable, simple and cost effective, and is suitable for real-time monitoring of biospecific interactions such as antigen-antibody, receptor ligand, and enzymes-substrate interactions with high sensitivity and specificity. For instance, the biological mixtures such as antibodies are capable of binding to terminal active functional groups (i.e., COOH, OH and NH2) of self-assembled monolayers (SAM) and immunocapture antigens such as glycoproptien or other targets[2]. The QCM can consequently detect mass changes due to these molecular interactions on the surface of the QCM. The top and bottom circular excitation electrodes with 150um diameter were modeled as gold (Au) films of 16 μm thickness. A sinusoidal voltage with amplitude of 5 mV was applied across the quartz crystal. Figure 1 shows the principle of integrated biosensors which gold electrodes were printed on both sides of a thin 500um quartz layer to form the quartz crystal microbalance (QCM)-impedance device. The silver (Ag) semicircular counter electrode was modeled around the top working electrode on the same area of the quartz crystal for performing the electrochemical impedance spectroscopy (EIS) experiments for detection of bacteria (E-Coli) and the results were compared to quartz crystal microbalance measurements. Furthermore, the use of gold surface can be incorporated into the transducer compatible with the biological samples such as use of highly specific monoclonal antibodies, and incorporation of amplification step to maximize the signal detection. In general, the quartz crystal is traditionally considered to be a mass sensitive sensor that produces response which it changes its resonance frequency to different thin film samples or liquids in contact with it surface. For a straight relationship between a thin film mass of the order of nanograms, the quartz crystal response will be of of the order of Hertz according to Eq. 1, Sauerbrey Equation [3]. ρq and μq are the specific density and the shear modulus in quartz, respectively. ϝ0 is the fundamental resonance frequency in quartz, related to its thickness, nq. Δm is the thin film mass deposited A, is the piezoelectrically active crystal area and n is the overtone number. Based on Eq. 1, it can be found that if the density of QCM changes, the resonant frequency of the device also changes, making the QCM suitable for monitoring changes in mass. [Display omitted] In contact with liquids, the crystal is capable of giving information about the density-viscosity product (√ρn) of the fluid by changing its resonance frequency and quality Q-factor according with Eq.3, Kanazawa equation[3]: [Display omitted] Where ρL and ηL are the density and viscosity in fluid respectively. Whilst, Eq. 4 indicates the decay characteristic length (δ) as linear relationship to the ratio viscosity to density of the liquid and inversely proportional the angular frequency (ω).Prior to device fabrication, 3D electric field analysis, resonant frequency simulations and thickness shear deformation were performed using automatic meshers by COMSOL Multiphysics. The resonator was modeled in three dimensions (3D), as an AT-cut quartz substrate of 500 μm thickness. The eigenfrequency analysis was performed to produce the quartz surface displacement and thickness shear deformation. The frequency domain analysis was conducted to obtain the resonant frequency of the resonator. Here we have tested the performance of the application of biosensors mainly in the detection of E-coli bacteria using QCM-impedance device using Escherichia coli cells as model of detection. Both frequency and impedance measurements were successfully obtained using cells both in media and in distilled water. We believe than this work offers a promising solution for the next generation of healthcare devices where high accuracy results are provided by low cost sensors.

Investigation of the mineralogical petrographic, geochemical and physical properties of carbonate rocks from Ileia Prefecture and assesment for industrial applications

Research on carbonate rocks has been increasingly important during the last few decades, due to their numerous applications. In this paper, we examined the properties of Cretaceous carbonate rocks from the Olonos-Pindos Zone from Ileia Prefecture. The relationships between various physical properties and between petrographic features and physical properties were defined. This may lead to preliminary evaluation of carbonate rocks using microscopic investigation, which unlike the elaboration of a series of physical and mechanical properties, is a fast and inexpensive method. In addition, these properties, along with their geochemical characteristics, were used to assess the suitability of these carbonate rocks as fillers in various applications. Detailed petrographic study of the collected samples revealed the occurrence of biomicrite, intramicrite (mudstone και wackestone), biosparite (packstones and grainstones), intrasparite and rudstone. From the lower to the upper members, a decrease of the grain size of calcite is observed. X-ray diffraction study of the insoluble residue revealed the presence of quartz, chlorite, illite, smectite, and mixed layer illite-chlorite. The colour index of the investigated powdered samples is negatively influenced by the increase of organic and insoluble residue contents. The water absorption is inversely correlated with CaO content while moisture is positively correlated with insoluble residue. The grainstone and rudstone are characterized as ultra-high pure calcium limestones, except for Mg-rich crystalline dolomitic limestones. The packstones are calcium limestones of high to medium purity. Mudstones and wackestones are characterized as low calcium limestones. The results suggest that all the examined lithotypes can be used as soil conditioners and animal feed supplements; however only grainstones and rudstones are suitable for desulphurization of exhaust gasses and cement production.

Tube fossils from gossanites of the Urals VHMS deposits, Russia: Authigenic mineral assemblages and trace element distributions

The occurrence, types, morphology, and mineralogical characteristics of tube microfossils were studied in gossanites from twelve VHMS deposits of the Urals. Several types of tube microfossils were recognized, including siboglinids, polychaetes and calcerous serpulids, replaced by a variety of minerals (e.g. hematite–quartz, hematite–chlorite, carbonate–hematite) depending on the nature of the substrate prior to the formation of the gossanites. Colonial hematite tube microfossils (~150μm across,1–2mm long) are composed of hematitic outer and inner walls, and may exhibit a cellular structure within their cavities. Spherical forms are saturated with Fe-oxidizing bacteria inside the tubes – probably analogues of trophosomes. Colloform stromatolitic outer wall surfaces are characterized by the presence of numerous interlaced filaments of hematite (2–3μm diameter, up to 1–2mm long). Between tube microfossils, the hematitized cement contains bundles of hematitized filaments with structures similar to the hyphae of fungi. Hematite–chlorite tube microfossils are scattered in gossanites, mostly as biological debris. They are typically 30 to 300μm in diameter and 1 to 5mm long. The layered structure of their tube walls is characterized by hematite–quartz and chlorite layers. Abundant filamentous bacteria coated by glycocalix and chlorite stromatolite are associated with hematite–chlorite tubes. The carbonate–hematite tube microfossils (up to 300μm across, 2–3mm long) occur in carbonate-rich gossanites. The tubes are characterized by fine (~10μm thick) walls of hematite and cavities dominated by relatively dark carbonate or hematite. Carbonates may be present both in walls and cavities. Stromatolite-like leucoxene or hematite–carbonate aggregates were also found in association with tubes. Randomly oriented filaments are composed of ankerite. Single filaments are composed of individual cells, typically smaller than 100nm across, similar to that of magnetotactic bacteria.Three dimensional tomographic images of all types of tube microfossils demonstrate a clear wavy microlayering from outer and inner walls, which may reflect segmentation of the tube worms. The traces of burrowing or fragments of glycocalix with relict spheres are typical of tube microfossils from gossanites.The carbon isotopic composition of carbonates associated with tube microfossils from hematite–quartz, hematite–carbonate, and hematite–chlorite gossanites average−7.2, − 6.8, –22.8‰, PDB, respectively. These values are indicative of a biogenic origin for the carbonates. The oxygen isotopic composition of these carbonates is similar in all three gossanite types averaging +13.5, +14.2, +13.0‰ (relative to SMOW), and indicative of active sulfate reduction during the diagenetic (and anadiagenetic) stages of the sediments evolution. The trace element characteristics of hematite from tube microfossils are characterized by high contents of following trace elements (average, ppm): Mn (1529), As (714), V (540), W (537), Mo (35), and U (5). Such high contents are most likely the result of metal and metalloid sorption by fine particles of precursor iron hydroxides during the oxidation of sulfides and decomposition of hyaloclasts via microbially-mediated reactions.

A Rare Glimpse of Paleoarchean Life: Geobiology of an Exceptionally Preserved Microbial Mat Facies from the 3.4 Ga Strelley Pool Formation, Western Australia.

Paleoarchean rocks from the Pilbara Craton of Western Australia provide a variety of clues to the existence of early life on Earth, such as stromatolites, putative microfossils and geochemical signatures of microbial activity. However, some of these features have also been explained by non-biological processes. Further lines of evidence are therefore required to convincingly argue for the presence of microbial life. Here we describe a new type of microbial mat facies from the 3.4 Ga Strelley Pool Formation, which directly overlies well known stromatolitic carbonates from the same formation. This microbial mat facies consists of laminated, very fine-grained black cherts with discontinuous white quartz layers and lenses, and contains small domical stromatolites and wind-blown crescentic ripples. Light- and cathodoluminescence microscopy, Raman spectroscopy, and time of flight—secondary ion mass spectrometry (ToF-SIMS) reveal a spatial association of carbonates, organic material, and highly abundant framboidal pyrite within the black cherts. Nano secondary ion mass spectrometry (NanoSIMS) confirmed the presence of distinct spheroidal carbonate bodies up to several tens of μm that are surrounded by organic material and pyrite. These aggregates are interpreted as biogenic. Comparison with Phanerozoic analogues indicates that the facies represents microbial mats formed in a shallow marine environment. Carbonate precipitation and silicification by hydrothermal fluids occurred during sedimentation and earliest diagenesis. The deciphered environment, as well as the δ13C signature of bulk organic matter (-35.3‰), are in accord with the presence of photoautotrophs. At the same time, highly abundant framboidal pyrite exhibits a sulfur isotopic signature (δ34S = +3.05‰; Δ33S = 0.268‰; and Δ36S = -0.282‰) that is consistent with microbial sulfate reduction. Taken together, our results strongly support a microbial mat origin of the black chert facies, thus providing another line of evidence for life in the 3.4 Ga Strelley Pool Formation.