Occurrence and Distribution of Moganite and Opal-CT in Agates from Paleocene/Eocene Tuffs, El Picado (Cuba)

Agates in Paleocene/Eocene tuffs from El Picado/Los Indios, Cuba were investigated to characterize the mineral composition of the agates and to provide data for the reconstruction of agate forming processes. The volcanic host rocks are strongly altered and fractured and contain numerous fissures and veins mineralized by quartz and chalcedony. These features indicate secondary alteration and silicification processes during tectonic activities that may have also resulted in the formation of massive agates. Local accumulation of manganese oxides/hydroxides, as well as uranium (uranyl), in the agates confirm their contemporaneous supply with SiO2 and the origin of the silica-bearing solutions from the alteration processes. The mineral composition of the agates is characterized by abnormal high bulk contents of opal-CT (>6 wt%) and moganite (>16 wt%) besides alpha-quartz. The presence of these elevated amounts of “immature” silica phases emphasize that agate formation runs through several structural states of SiO2 with amorphous silica as the first solid phase. A remarkable feature of the agates is a heterogeneous distribution of moganite within the silica matrix revealed by micro-Raman mapping. The intensity ratio of the main symmetric stretching-bending vibrations (A1 modes) of alpha-quartz at 465 cm−1 and moganite at 502 cm−1, respectively, was used to depict the abundance of moganite in the silica matrix. The zoned distribution of moganite and variations in the microtexture and porosity of the agates indicate a multi-phase deposition of SiO2 under varying physico-chemical conditions and a discontinuous silica supply.

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Agates from Western Atlas (Morocco)—Constraints from Mineralogical and Microtextural Characteristics

Minerals ◽

10.3390/min10020198 ◽

2020 ◽

Vol 10 (2) ◽

pp. 198 ◽

Cited By ~ 2

Author(s):

Jaroslav Pršek ◽

Magdalena Dumańska-Słowik ◽

Tomasz Powolny ◽

Lucyna Natkaniec-Nowak ◽

Tomasz Toboła ◽

...

Keyword(s):

Carbonaceous Material ◽

Hydrothermal Activity ◽

Silica Matrix ◽

Jigsaw Puzzle ◽

Iron Sulfides ◽

Physico Chemical ◽

Vein Deposits ◽

Chemical Conditions ◽

Silica Phases ◽

Host Rocks

Agate samples collected from the vicinity of Asni and Agouim (Western Atlas, Morocco) were investigated using microscopic observations supported by Raman micro-spectroscopy. The agates are marked by the presence of various microtextures typical of epithermal vein deposits, including jigsaw-puzzle, feathery, and lattice-bladed. The first two indicate that the formation of agates was likely marked by recrystallization of metastable silica phases (i.e., opaline silica or massive chalcedony). The presence of lattice-bladed (after barite and calcite) quartz may be, in turn, ascribed to the boiling-related conditions that could have triggered the formation of abundant copper and iron sulfides found within silica matrix. Additionally, the local occurrence of growth lines (so-called Bambauer quartz) and intergrowth of length-slow and length-fast chalcedony are linked to the variations of physico-chemical conditions during rock formation (alkaline-acidic). According to Raman spectroscopy, silica matrix of the agates is made of α-quartz with a local admixture of moganite (from 0.0 up to 78 wt.%), but also contains numerous solid inclusions of hematite, celadonite, as well as poorly-organized carbonaceous material and rutile. These phases were likely emplaced during low-temperature hydrothermal activity of SiO2-bearing fluids that originated from post-magmatic hydrothermal activity developed within host rocks and/or meteoric waters.

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Tungsten Ores of the Dzhida W-Mo Ore Field (Southwestern Transbaikalia, Russia): Mineral Composition and Physical-Chemical Conditions of Formation

Minerals ◽

10.3390/min11070725 ◽

2021 ◽

Vol 11 (7) ◽

pp. 725

Author(s):

Ludmila B. Damdinova ◽

Bulat B. Damdinov

Keyword(s):

Mineral Composition ◽

Fluid Inclusions ◽

Apical Part ◽

Hydrothermal Fluids ◽

True Temperature ◽

Gangue Mineral ◽

Mineral Formation ◽

Physical Chemical ◽

Homogenization Temperatures ◽

Chemical Conditions

This article discusses the peculiarities of mineral composition and a fluid inclusions (FIs further in the text) study of the Kholtoson W and Inkur W deposits located within the Dzhida W-Mo ore field (Southwestern Transbaikalia, Russia). The Mo mineralization spatially coincides with the apical part of the Pervomaisky stock (Pervomaisky deposit), and the W mineralization forms numerous quartz veins in the western part of the ore field (Kholtoson vein deposit) and the stockwork in the central part (Inkur stockwork deposit). The ore mineral composition is similar at both deposits. Quartz is the main gangue mineral; there are also present muscovite, K-feldspar, and carbonates. The main ore mineral of both deposits is hubnerite. In addition to hubnerite, at both deposits, more than 20 mineral species were identified; they include sulfides (pyrite, chalcopyrite, galena, sphalerite, bornite, etc.), sulfosalts (tetrahedrite, aikinite, stannite, etc.), oxides (scheelite, cassiterite), and tellurides (hessite). The results of mineralogical and fluid inclusions studies allowed us to conclude that the Inkur W and the Kholtoson W deposits were formed by the same hydrothermal fluids, related to the same ore-forming system. For both deposits, the fluid inclusion homogenization temperatures varied within the range ~195–344 °C. The presence of cogenetic liquid- and vapor-dominated inclusions in the quartz from the ores of the Kholtoson deposit allowed us to estimate the true temperature range of mineral formation as 413–350 °C. Ore deposition occurred under similar physical-chemical conditions, differing only in pressures of mineral formation. The main factors of hubnerite deposition from hydrothermal fluids were decreases in temperature.

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Uranium(VI) Uptake by Synthetic Calcium Silicate Hydrates

MRS Proceedings ◽

10.1557/proc-1107-467 ◽

2008 ◽

Vol 1107 ◽

Cited By ~ 13

Author(s):

J. Tits ◽

T. Fujita ◽

M. Tsukamoto ◽

E. Wieland

Keyword(s):

Solid Phase ◽

Near Field ◽

Sorption Isotherms ◽

Alkaline Solutions ◽

Precipitation Process ◽

Direct Reaction ◽

Reaction Method ◽

Calcium Silicate Hydrates ◽

Chemical Conditions ◽

Co Precipitation

AbstractThe immobilization of U(VI) by C-S-H phases under conditions relevant for the cementitious near field of a repository for radioactive waste has been investigated. C-S-H phases have been synthesized using two different procedures: the “direct reaction” method and the “solution reaction” method.The stabilities of alkaline solutions of U(VI) (presence of precipitates or colloidal material) were studied prior to sorption and co-precipitation tests in order to determine the experimental U(VI) solubility limits. These U(VI) solubility limits were compared with the U(VI) solubilities obtained from thermodynamic speciation calculations assuming the presence of combinations of different solid U(VI) phases. The solid phase controlling U(VI) solubility in the present experiments was found to be CaUO4(s).The U(VI) uptake kinetics and sorption isotherms on C-S-H phases with different C:S ratios were determined under various chemical conditions; e.g., sorption and co-precipitation experiments and different pH’s. U(VI) was found to sorb fast and very strongly on C-S-H phases with distribution ratios (Rd values) ranging in value between 103 L kg-1 and 106 L kg-1. Both sorption and co-precipitation experiments resulted in Rd values which were very similar, thus indicating that no additional sorption sites for U(VI) were generated in the co-precipitation process. Furthermore, C-S-H synthesis procedures did not have a significant influence on U(VI) uptake. The U(VI) sorption isotherms were found to be non-linear, and further, increasing Ca concentrations resulted in increasing U(VI) uptake. The latter observation suggests that U(VI) uptake is controlled by a solubility-limiting process, while the former observation further indicates that pure Ca-uranate is not the solubility-limiting phase. It is proposed that a solid solution containing Ca and could control U(VI) uptake by C-S-H phases.

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Suspension Plasma Spraying (SPS) of Cobalt Spinel

Thermal Spray 1997: Proceedings from the United Thermal Spray Conference ◽

10.31399/asm.cp.itsc1997p0343 ◽

1997 ◽

Author(s):

G. Schiller ◽

M. Müller ◽

F. Gitzhofer ◽

M.I. Boulos ◽

R.B. Heimann

Keyword(s):

Plasma Spraying ◽

Inductively Coupled Plasma ◽

Solid Phase ◽

Spinel Phase ◽

Rf Plasma ◽

Dry Powders ◽

Inductively Coupled ◽

Cobalt Spinel ◽

Chemical Conditions ◽

Physical And Chemical

Abstract Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co3O4) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.

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Generalization of the Unified Analytic Melt-Shear Model to Multi-Phase Materials: Molybdenum as an Example

Crystals ◽

10.3390/cryst9020086 ◽

2019 ◽

Vol 9 (2) ◽

pp. 86 ◽

Cited By ~ 2

Author(s):

Leonid Burakovsky ◽

Darby Luscher ◽

Dean Preston ◽

Sky Sjue ◽

Diane Vaughan

Keyword(s):

Shear Modulus ◽

Solid Phase ◽

Model Parameters ◽

Quantum Molecular Dynamics ◽

Face Centered Cubic ◽

Shear Model ◽

Bcc Structure ◽

Face Centered ◽

Multi Phase ◽

Theoretical Results

The unified analytic melt-shear model that we introduced a decade ago is generalized to multi-phase materials. A new scheme for calculating the values of the model parameters for both the cold ( T = 0 ) shear modulus ( G ) and the melting temperature at all densities ( ρ ) is developed. The generalized melt-shear model is applied to molybdenum, a multi-phase material with a body-centered cubic (bcc) structure at low ρ which loses its dynamical stability with increasing pressure (P) and is therefore replaced by another (dynamically stable) solid structure at high ρ . One of the candidates for the high- ρ structure of Mo is face-centered cubic (fcc). The model is compared to (i) our ab initio results on the cold shear modulus of both bcc-Mo and fcc-Mo as a function of ρ , and (ii) the available theoretical results on the melting of bcc-Mo and our own quantum molecular dynamics (QMD) simulations of one melting point of fcc-Mo. Our generalized model of G ( ρ , T ) is used to calculate the shear modulus of bcc-Mo along its principal Hugoniot. It predicts that G of bcc-Mo increases with P up to ∼240 GPa and then decreases at higher P. This behavior is intrinsic to bcc-Mo and does not require the introduction of another solid phase such as Phase II suggested by Errandonea et al. Generalized melt-shear models for Ta and W also predict an increase in G followed by a decrease along the principal Hugoniot, hence this behavior may be typical for transition metals with ambient bcc structure that dynamically destabilize at high P. Thus, we concur with the conclusion reached in several recent papers (Nguyen et al., Zhang et al., Wang et al.) that no solid-solid phase transition can be definitively inferred on the basis of sound velocity data from shock experiments on Mo. Finally, our QMD simulations support the validity of the phase diagram of Mo suggested by Zeng et al.

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SELF-ORGANIZED PHASE SEGREGATION IN A DRIVEN FLOW OF DISSIMILAR PARTICLES MIXTURES

International Journal of Modern Physics C ◽

10.1142/s0129183103005108 ◽

2003 ◽

Vol 14 (07) ◽

pp. 955-962 ◽

Cited By ~ 8

Author(s):

R. B. PANDEY ◽

J. F. GETTRUST ◽

RAY SEYFARTH ◽

LUIS A. CUEVA-PARRA

Keyword(s):

Gas Phase ◽

Solid Phase ◽

Phase Segregation ◽

Continuous Phase ◽

Phase System ◽

Immiscible Fluid ◽

Fluid Mixture ◽

Self Organized ◽

Phase Scaling ◽

Multi Phase

Self-organized patterns in an immiscible fluid mixture of dissimilar particles driven from a source at the bottom are examined as a function of hydrostatic pressure bias by a Monte Carlo computer simulation. As the upward pressure bias competes with sedimentation due to gravity, a multi-phase system emerges: a dissociating solid phase from the source is separated from a migrating gas phase towards the top by an interface of mixed (bi-continuous) phase. Scaling of solid-to-gas phase with the altitude is nonuniversal and depends on both the range of the height/depth and the magnitude of the pressure bias. Onset of phase separation and layering is pronounced at low bias range.

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Silica-based solid-phase extraction of cross-linked nucleic acid–bound proteins

Life Science Alliance ◽

10.26508/lsa.201800088 ◽

2018 ◽

Vol 1 (3) ◽

pp. e201800088 ◽

Cited By ~ 22

Author(s):

Claudio Asencio ◽

Aindrila Chatterjee ◽

Matthias W Hentze

Keyword(s):

Nucleic Acid ◽

Protein Interactions ◽

Solid Phase ◽

Protein Complexes ◽

Simple Procedure ◽

Silica Matrix ◽

Cellular Functions ◽

Dna And Rna ◽

Acid Protein ◽

Huh7 Cells

Proteins interact with nucleic acids to regulate cellular functions. The study of these regulatory interactions is often hampered by the limited efficiency of current protocols to isolate the relevant nucleic acid–protein complexes. In this report, we describe a rapid and simple procedure to highly enrich cross-linked nucleic acid–bound proteins, referred to as “2C” for “complex capture.” This method is based on the observation that silica matrix–based columns used for nucleic acid purification also effectively retain UV cross-linked nucleic acid–protein complexes. As a proof of principle, 2C was used to isolate RNA-bound proteins from yeast and mammalian Huh7 cells. The 2C method makes RNA labelling redundant, and specific RNA–protein interactions can be observed and validated by Western blotting. RNA–protein complexes isolated by 2C can subsequently be immunoprecipitated, showing that 2C is in principle compatible with sensitive downstream applications. We suggest that 2C can dramatically simplify the study of nucleic acid–protein interactions and benefit researchers in the fields of DNA and RNA biology.

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Fractionation of Selected Heavy Metals in Agricultural Soils / Frakcjonowanie Wybranych Metali Ciężkich W Glebach Uprawnych

Ecological Chemistry and Engineering S ◽

10.2478/eces-2013-0009 ◽

2013 ◽

Vol 20 (1) ◽

pp. 117-125 ◽

Cited By ~ 2

Author(s):

Szymon Różański

Keyword(s):

Organic Matter ◽

Significant Role ◽

Manganese Oxides ◽

Solid Phase ◽

Extraction Procedure ◽

Total Content ◽

Residual Fraction ◽

Geochemical Background ◽

Fraction Bound ◽

Iron And Manganese

Abstract The content of trace elements in soils varies widely and their mobility and availability depends not only on the total content but also on the form of in which these elements occur. The aim of this study was to determine the total content of nickel, lead, zinc and copper in soils used for agriculture, and assess the mobility and phytoavailability of these metals against a background of physical and chemical properties of these soils. In samples taken from three soil profiles (Phaeozem and 2 Fluvisols) the contents of Ni, Pb, Zn and Cu were determined using atomic absorption spectroscopy in the solutions obtained according to the protocol of modified BCR sequential extraction procedure supplemented with aqua regia digestion. The total content of the analyzed metals in most cases corresponded to the natural values, often not exceeding the geochemical background level. It was only in the one profile of the Fluvisols (Endogleyic Fluvisol) that a higher concentration of zinc and lead was noticed (especially in the surface horizon), slightly exceeding the legal limit. Among the studied metals the lowest phytoavailability was characterized by copper (exchangeable forms on average 4.73% of the total), and the highest by zinc (11.49%). Nickel was the most permanently bound with soil solid phase, and its content in the residual fraction reached 84.46% of the total. Approximately a half of the total lead content was determined as a fraction bound with iron and manganese oxides, while in the case of this metal a significant role in binding of this metal was playing organic matter (fraction bound with organic matter and sulphides - an average of 27.5%). Significant role in the binding of all investigated metals was credited to iron and manganese compounds.

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Dummy molecularly imprinted mesoporous silicates for selective adsorption of 2-naphthol

Open Chemistry ◽

10.1515/chem-2015-0090 ◽

2015 ◽

Vol 13 (1) ◽

Cited By ~ 1

Author(s):

Guitao Luoa ◽

Yunping Li ◽

An Wang ◽

Qiang Lin ◽

Guolin Zhang ◽

...

Keyword(s):

Solid Phase ◽

Selective Adsorption ◽

Sol Gel ◽

Silica Matrix ◽

Ionic Surfactant ◽

Mesoporous Silicates ◽

Covalent Bonds ◽

Molecularly Imprinted ◽

Pluronic P123 ◽

Triblock Copolymer Surfactant

AbstractDummy molecularly imprinted mesoporous silicates (MIMS-2) were made by co-condensation of tetraethyl orthosilicate (TEOS) with precursors of bi-functional mimic of 2-naphthol, 2,7-dihydroxynaphthalene, around triblock copolymer surfactant Pluronic (P123) micelles. The bi-functional template was linked to two functional monomers through thermally cleavable covalent bonds to generate imprint precursor. This provides the possibility of incorporating the target into the cross-linked mesoporous silicate matrix in the non-ionic surfactant templated sol-gel process. P123 was eluted by ethanol extraction and template molecules were removed by refluxing the materials in a mixture of dimethyl sulfoxide (DMSO) and water. MIMS-1 was prepared similarly except that 2-naphthol was used as template instead of 2,7-dihydroxynaphthalene. Solid phase extraction studies showed that MIMS-2 exhibited good retention and selectivity for 2-naphthol among its structural analogues. The mono-functional molecule 2-naphthol was unable to be incorporated into the silica matrix of mesoporous material by the identical method, and the resulting material MIMS-1 exhibits poor selectivity to the template analogues.

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Numerical Study of Two-Phase Granular Flow for Process Equipment

Journal of Pressure Vessel Technology ◽

10.1115/1.1310366 ◽

2000 ◽

Vol 122 (4) ◽

pp. 462-468 ◽

Cited By ~ 1

Author(s):

R. Djebbar ◽

S. B. Beale ◽

M. Sayed

Keyword(s):

Granular Flow ◽

Solid Phase ◽

Numerical Study ◽

Numerical Procedure ◽

Process Equipment ◽

Two Phase ◽

Angle Of Internal Friction ◽

Phase Liquid ◽

Multi Phase ◽

Realistic Geometries

This paper reports on a research program of modeling multi-phase granular flow. Both single-phase granular flow and two-phase liquid/granular flow in a pressure vessel were considered. For the latter case, detailed results based on a viscous/Mohr-Coulomb closure were compared to existing formulations. Idealized test cases indicated that the numerical procedure is sound. Subsequent simulations of two-phase flow using realistic geometries and boundary conditions showed that the pressure distribution in the solid phase is fundamentally different for the Mohr-Coulomb system than for the conventional system. The effect of the angle of internal friction, geometry, and other parameters is discussed. [S0094-9930(00)01204-X]

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