Dispersed Mineral Research Articles

Fluorescence X-ray microscopy on hydrated tributyltin-clay mineral suspensions

Using the scanning transmission X-ray microscope at ID21 beamline of the ESRF in fluorescence mode, we mapped tin at a bulk concentration of 1000 μg(Sn)/ml within hydrated tributyltin (TBT) - clay mineral (Kaolinite) dispersion with sub-300 nm spatial resolution. Using the L absorption edges of tin at 3929, 4156 and 4465 eV fluorescence radiation was excited in tin atoms with incident photon energies of 4 and 4.5 keV. When using 4 keV radiation, only tin fluorescence is excited. For 4.5 keV X rays, both the fluorescence of tin and calcium (which is present in the solid phase) can be measured. Methodologically, we were interested in assessing and proving the possibilities and limitations of fluorescence mapping using the L absorption edges of tin, where the fluorescence yield is significantly lower compared to other elements with their K edges in the same energy range. Scientifically, organotin-clay mineral interactions are of environmental concern because this factor influences significantly the distribution of toxic TBT in the aquatic system. On one hand, the half-life of TBT deposited to the sediment phase increases, and consequently the time of its bioavailability. On the other hand, the adsorption process is reversible, which means that contaminated sediments can act as a source of pollution. The adsorption and desorption effects can be studied directly with high spatial resolution and brought into connection to the surface properties of the clay mineral under study as well as to other experimental parameters, like pH or salinity.

Triassic–Jurassic weathering and clay mineral dispersal in basement areas and sedimentary basins of southern Sweden

The basement rocks of southern Sweden were deeply weathered in Late Triassic through Cretaceous times, and possibly even earlier. Sub-Mesozoic saprolites formed, presumably due to long-term warmth and humidity, in conjunction with decomposition of abundant organic matter and subsequent infiltration of acidic water. The upper parts of the weathering profiles were subjected to intense leaching and kaolinitisation whereas the less evolved deep weathering front is enriched in smectite. Thus, any erosion prior to full regolith development, or extraordinary deep erosion, released less developed, smectite-rich weathering material to the Late Triassic–Jurassic receiving basins. Mesozoic sedimentary successions in Southern Sweden show high detrital smectite and/or kaolinite contents, moderate illite contents and low chlorite contents, compatible with expected mid-latitude warm equable greenhouse conditions. Norian and older Triassic haematite-cemented continental arkoses and smectite-dominated clays (smectite≫kaolinite) were clearly formed in arid settings. From the Rhaetian and throughout the Jurassic, humid onshore conditions sustained abundant plant and peat accumulation, early diagenetic meteoric flushing, and intense chemical weathering. Kaolinite is therefore a dominating detrital clay mineral in these sedimentary successions (kaolinite≈illite≫chlorite and smectite (I/S)). Minor quantitative variations in clay mineralogy within the “humid climate” Rhaetian–Jurassic sedimentary successions are difficult to interpret. In deltaic coal-bearing successions, the detrital clay mineral composition is conspicuously constant (kaolinite≈illite≫chlorite), possibly due to post-depositional clay mineral transformation. Conversely, in shallow marine deposits, some quantitative variation is notable (kaolinite≈illite>variable smectite≫chlorite). This may reflect that the original detrital composition was better preserved in shallow marine settings. Smectitic clay minerals associated with gypsum and caliche nodules ambiguously indicate increased aridity towards the end of the Jurassic.

Multi-sources of desert sands for the Jungger Basin

The grain size and mineral composition analyses of 236 samples from nine different sub-deserts within the Jungger Basin of north-western China reveal that dune sands from that region may be derived by local reworking of the underlying sands. That the grain size characteristics and mineral compositions vary with different sub-deserts show the diversities of their sand sources. The similarities and differences in mineral assemblage, mineral dispersion, quartz/feldspar value and grain size distribution between the dune sands and their underlying sands in the same sub-desert indicate that dune sands have derived from underlying sands within the same sub-basin, but dune sands have also received minor contributions of sediment from areas outside the sub-deserts.

Magnetic susceptibility of Mesozoic and Cenozoic sediments off Mid Norway and the role of siderite: implications for interpretation of high-resolution aeromagnetic anomalies

The study was designed to examine lithological and stratigraphic variations in magnetic susceptibility of the Mesozoic and parts of the Cenozoic sedimentary succession in petroleum exploration areas offshore Norway, and investigate the source of the susceptibility. The study includes measurements of more than 6 km core from exploration wells and shallow drill sites, with main focus on the northern North Sea—Norwegian Sea area. Considerable variation in susceptibility is detected and includes: (1) Average higher susceptibility in the finer-grained lithologies and lowest susceptibility in mineralogically mature sandstones. (2) Relatively high susceptibility in Upper Jurassic–Cretaceous shaly sequences. (3) Provenance controls on susceptibility in Triassic–Jurassic coarse clastic sediments. (4) In all exploration wells, positive correlation of high susceptibility to diagenetic siderite-cementation. The siderite-cemented beds and nodules are of particular importance in controlling the susceptibility distribution in the dark shale units. Susceptibility log patterns from different sediment environments are also exemplified and can tentatively be divided into four types of patterns, reflecting combinations of dispersed and concentrated mineral sources of susceptibility. Magnetic laboratory measurements verify presence of both paramagnetic and ferrimagnetic components in samples with high susceptibility values and with a dominance of the induced magnetisation.

Composite suspended sediment particles and flocculation in glacial meltwaters: preliminary evidence from Alpine and Himalayan basins

AbstractResearch over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles. These particles are also known as aggregates or flocs, and are commonly made up of constituent mineral particles, which evidence a wide range of grain sizes, and organic matter. The resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment, transport and deposition. The significance of composite suspended sediment particles in glacial meltwater streams has, however, not been established. Existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction (absolute particle size), which, for certain size fractions, may bear little relationship to the effective or in situ distribution. Existing understanding of composite particle formation within freshwater environments would suggest that in‐stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents. However, we report preliminary scanning electron microscopy data for one Alpine and two Himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system. The genesis and structure of these composite particles and their constituent grain size characteristics are discussed. We present evidence for the existence of both aggregates, or composite particles whose features are largely inherited from source materials, and flocs, which represent composite particles produced by in‐stream flocculation processes. In the absence of organic materials, the latter may result solely from electrochemical flocculation in the meltwater sediment system. This type of floc formation has not been reported previously in the freshwater fluvial environment. Further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events. Such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation. Copyright © 2002 John Wiley & Sons, Ltd.

Influence of anions on the rheological properties of clay mineral dispersions

The flow behavior of sodium montmorillonite dispersions and kaolin slurries can have different responses to anionic dispersants. Viscosity, pH, and dynamic mobility measurements using a variety of salts help elucidate this important observation. The flow behavior is determined not only by the counterions but also by the coions (anions) surrounding the clay mineral particles. The viscosity of sodium montmorillonite dispersions with increasing salt or acid concentration decreased to a minimum, then increased sharply. The concentration at this point was identified as the critical coagulation concentration, c K. Salts with multivalent anions such as sulphates and phosphates increased the critical coagulation concentration. Na 4P 2O 7 actually impeded coagulation. The liquefying effect of these anions was counterbalanced by the protons of acidic salts such as NaHSO 4, Na 2HPO 4, and NaH 2PO 4 and by acids. The critical coagulation concentration for sodium montmorillonite was a function of the montmorillonite concentration and the type of ion. In 2% sodium montmorillonite dispersions, c K for sodium chloride and sulphate was higher than c K in dilute dispersions (0.025%). For the strongly liquefying agents Na 2HPO 4, NaH 2PO 4, and H 3PO 4, the opposite was true. The c K values for the dilute dispersion were 1100, 460, and 32 mmol/l respectively, and for the 2% dispersion 80, 40, and 10 mmol/l. Kaolinite dispersions in contrast to sodium montmorillonite showed the pronounced liquefying effect of multivalent anions up to high salt concentrations. The data underscored the complexity of dispersed systems. For example, the dynamic mobility of the particles and the viscosity of the system were not always directly related. An interesting aspect concerns the dynamic mobility of the montmorillonite and kaolinite particles which in different ways changed with concentration of salts and acids.

Separating off the Solidus Portion of Finely Dispersed Mineral Sludge by a Filtering-Screw Conveyor Press: A Model Calculation

Separating off the Solidus Portion of Finely Dispersed Mineral Sludge by a Filtering-Screw Conveyor Press: A Model Calculation

Drainage evolution in south-central Africa since the breakup of Gondwana

The drainage system in south-central Africa has undergone major reorganisations since the disruption of Gondwana. Isopachs of the Kalahari sequence and a variety of geomorphological features can be used to pinpoint abandoned drainage lines. Continental fluvial sediments of Mesozoic-Cenozoic age reflect river systems which existed prior to and immediately following continental break-up. The east coast sedimentary sequence documents changes in the location of major supplies of terrigenous sediments, and provides a framework for establishing the timing of changes in drainage configuration. This evidence indicates that during the upper Jurassic to Cretaceous, the Okavango, Cuando and Zambezi-Luangwa rivers formed the headwaters of the proto-Limpopo. The lower-Zambezi-Shire formed a separate graben-bound river system with a discharge point into the Indian Ocean in the vicinity of mouth of the present-day Zambezi. A third major drainage entered the Indian in the vicinity of the modern Save mouth. End Cretaceous uplift along the Okavango-Kalahari-Zimbabwe Axis severed the links between the Limpopo and the Okavango, Cuando and Zambezi-Luangwa. This resulted in a senile endoreic drainage system which supplied sediment to the Kalahari basin. However, the uplift rejuvenated the lower Zambezi, initiating headward erosion and progressive capture of the Luangwa, upper Zambezi and Kafue. Predatory headward extension of the Zambezi is still active, and this river will eventually capture the Okavango. The model developed for drainage reorganisation provides a framework for interpreting kimberlitic heavy mineral dispersion patterns. It also forms the basis for explaining fish and plant dispersion patterns, and understanding recent water level fluctuations in the Makgadigadi pans system in Botswana.

An evolutionary model of glacial dispersal and till genesis in Maritime Canada

Abstract Glacier process models of till genesis cannot fully explain the properties of tills in Maritime Canada. A succession of local ice caps, called the Appalachian Ice Complex, developed during the last glaciation and were drained by ice streams into the submarine channels bordering the region. The migration of these centres produced areas with widely differing flow patterns, landform assemblages and deposits. Early regional phases of ice flow were characterized by wide, rapidly-flowing ice-streams that formed thick exotic, silty tills. In later phases, ice divides developed over highland areas underlain by metamorphic and igneous rocks, forming stony local tills. Terrain zones characterized by distinct transport histories and depositional sequences were produced by the interplay and migration of regional ice sheets and local ice caps. The interaction of local glaciers and previously deposited tills formed hybrid tills through two reworking processes: inheritance and overprinting. Inheritance is incorporation of till components and/or fabric into a younger till by erosion and entrainment of material from an older till. Overprinting is the injection or imprint of matrix, clasts or fabric on older tills by overriding ice. Glacial dispersal of rocks, minerals and trace elements in this complex glaciated terrain is controlled by the location of former ice divides. Simple unidirectional trains are preserved in relict terrains under divides. In ice marginal areas, reworking processes result in complex dispersal fans produced by smearing and widening of previously formed trains and fans. These dispersal fans can be modelled by vector addition of discrete flow events within each dispersal zone. A simple empirical model of glacier dispersal is presented using exponential decay and uptake algorithms, and incorporating the reworking of older till material.

Factors Affecting the Ratio of Cation Exchange Capacity to Clay Content in Lignite Overburden

Unusually high cation exchange capacity (CEC) values relative to clay content are frequently reported for lignite overburden and minesoils. The CEC to percent clay ratio is commonly greater than one and would require that the average charge of the clay fraction be greater than 100 cmol(c) kg(-1). A comparison of methods for particle-size distribution suggests that the major reason lignite overburden samples have CEC to percent clay ratios greater than one is incomplete dispersion of aggregates of clay minerals or shale fragments. Preliminary investigations revealed the presence of shale fragments, smectite, and partially weathered mica in the silt fraction. Methods commonly used in soil textural analysis underestimated clay content by approximately 24%. The silt fraction may, therefore, provide a "hidden" source of CEC. Another important factor influencing the CEC to percent clay ratio was the presence of organic materials (lignite) in the samples. Lignite may make a significant contribution to CEC in overburden materials. In a study designed to estimate the pH-dependent charge of both the mineral and organic fractions, the CEC of overburden organic constituents was determined to be approximately 158 cmol(c) kg(-1) at pH 8.2. The high CEC to percent clay ratio in lignite overburden and minesoils may be resolved by adjusting methods for clay determination to optimize dispersion and by accounting for CEC due to organic materials. An alternative approach is to use existing methodology and use correction factors to account for incomplete dispersion of clay minerals and the charge contributions of organic materials.

The application of heavy indicator mineralogy in mineral exploration with emphasis on base metal indicators in glaciated metamorphic and plutonic terrains

Abstract Indicator mineralogy is used to explore for a wide variety of mineral commodities. The method utilizes minerals which are sufficiently heavy to be readily concentrated in the laboratory, often colourful and possess other useful physical and chemical properties. The minerals also must be source specific. Some indicator minerals are true resistate minerals. The others, although less resistant, are stable in oxidized glacial drift and many non-glacial sediments. A few, such as gold grains, are silt sized but most are coarse grained. Grain size has a major impact on indicator mineral dispersal patterns in glacial drift. The coarse-grained indicator minerals are of two main types: (1) kimberlite indicator minerals (KIMs); and (2) metamorphosed or magmatic massive sulphide indicator minerals (MMSIMs). KIMs are enriched in Mg and Cr and most MMSIMs are enriched in Mg, Mn, Al or Cr. These indicator elements cannot be diagnosed geochemically in anomalous heavy mineral concentrates because the concentrates contain other, more plentiful non-indicator minerals containing the same elements in the same chemical form. Chalcopyrite is also a very useful MMSIM but the number of surviving grains in a dispersal train is too low for detection by selective geochemical analysis. MMSIMs are derived from three main types of base metal deposits and their associated alteration or reaction zones: (1) volcanosedimentary massive sulphides (encompassing volcanogenic, Sedex and Mississippi Valley subtypes) in medium to high grade regional metamorphic terrains; (2) skarn and greisen deposits; and (3) magmatic Ni-Cu sulphides. The variety of MMSIMs associated with Ni-Cu deposits is astonishing, apparently reflecting mineral hybridization related to assimilation of sulphurous sedimentary rocks by ultramafic magmas. Cr-diopside is one of the best indicators of fertile Ni-Cu environments although not necessarily of the actual Ni-Cu deposits. Heavy indicator mineralogy is much more sensitive than heavy mineral geochemical analysis and offers many exploration benefits in regional exploration programs including: (1) sampling efficiencies; (2) enlargement of both the bedrock target and dispersal train; (3) coverage of a wider range of mineral commodities; (4) undiminished sensitivity in areas of overabundant non-indicator heavy minerals; (5) visual evidence of points of origin of dispersal trains; and (6) indications of the economic potential of the source mineralization. It is most effective as a reconnaissance exploration tool and is particularly well suited for testing gneissic volcanosedimentary and plutonic terranes where base and precious metal deposits are highly modified and difficult to recognize by other prospecting methods.

Adsorption interaction of oligomeric sebacic acid peroxide with aerosil surface and its thermolysis in different solvents

Adsorption of oligomeric sebacic acid peroxide on dispersed mineral filler (aerosil) from different solvents was studied. IR spectroscopy was used to study an effect of solvent–peroxide–aerosil adsorption interaction on the products of peroxide thermolysis. Thermodynamic quality of a solvent with respect to oligoperoxide decreases in benzene > chloroform > dimethylformamide > dioxane series. Due to competitive adsorption and the change in the conformation of oligomeric molecule, the solvent considerably affects the peroxide decomposition in the presence of aerosil.

Environmental geochemistry of the Gulf Creek copper mine area, north-eastern New South Wales, Australia

Past mining and smelting of sulphide ore (pyrite-chalcopyrite-sphalerite) at the abandoned Gulf Creek mine has resulted in a stream highly contaminated by acid mine drainage (pH: 2.2–3.4), as well as degradation of local soil and vegetation. Physical dispersion of secondary metal-bearing minerals from abandoned ore and waste dumps into Gulf Creek and adsorption and coprecipitation of dissolved metals and metalloids in the stream bed cause elevated Ag, As, Cd, Cu, Fe, Pb and Zn values in stream sediments. The bioavailability of individual heavy metals to freshwater organisms changes downstream, however, selective bioaccumulation processes in algae reject readily bioavailable Zn and concentrate less bioavailable Cu. Polluted soils in the vicinity of the mine and smelter sites are subject to continuing soil erosion and either support no vegetation, or a depauperate flora with certain species showing bioaccumulation of metals and resistance to high metal contents. Rehabilitation of disturbed areas should involve covering and sealing sulphidic mine waste or removal of ore and waste dumps, installation of a physical and chemical plant or construction of a wetland environment (plus anoxic lime drains), and import of topsoil and planting of local, metal-tolerant plant species.

Soft X-ray spectromicroscopy on solid-stabilized emulsions

Oil–water emulsions stabilized by solids have been imaged with sub-100 nm spatial resolution and analyzed spectroscopically using a scanning transmission X-ray microscope. The emulsions are stabilized by particle heterocoagulate cages surrounding the oil droplets. These cages form due to the interaction of negatively charged clay mineral particles (sodium montmorillonite, Wyoming) and positively charged particles of calcium/aluminum layered double hydroxide (LDH). The emulsions were studied at atmospheric pressure, without any pretreatment using carbon K and calcium L X-ray absorption edges. Oil- and calcium-rich LDH were separately mapped, and the clay mineral dispersions were also imaged. Applying X-ray absorption-edge contrast, oil could be distinguished from water in the emulsion near the carbon K absorption edge (284 eV, 4.4 nm). Spectromicroscopy near the calcium L absorption edge (346 eV, 3.6 nm) allowed the structural details of heterocoagulate formation to be revealed.

Smectites as colloidal stabilizers of emulsions: II. Rheological properties of smectite-laden emulsions

Oil-in-water emulsions were prepared by dispersing aqueous dispersions of several bentonites, montmorillonites, and hectorites (2% solid content) in paraffin oil which contained 100 mg/25 ml of a coemulsifier (alkyl polyglucoside, glycerol monostearate, lecithin, tetra- and deca(ethylene oxide) hexadecyl ethers). The colloidal stabilizers were sodium montmorillonite from Wyoming (USA), sodium bentonite from Kimolos (Greece), soda-activated bentonite from Milos (Greece) and Kimolos, also after decomposition of the carbonate. Three samples of synthetic hectorites (as synthesized, after washing, and after impregnation with sodium polyphosphate) were also used as colloidal stabilizers. The processing steps had strong effects on the rheological properties of the clay mineral dispersions. The rheological behavior of emulsions reflected these properties of the dispersions. Due to the presence of the dispersed oil droplets, the shear stresses of the emulsions were distinctly higher than the corresponding values of the dispersions and increased with the oil volume fraction. Their behavior changed from antithixotropic to thixotropic with increasing oil volume fraction. The storage modulus G′ of the emulsions with alkyl polyglucoside and glycerol monostearate showed no linear viscoelastic regions indicating the destructive character of the oscillation experiments even at the smallest deformation and the lowest frequencies. The structure of the emulsion was more stable in the presence of lecithin and ethylene oxide ethers and resisted to the shearing forces during the oscillation experiments as indicated by the observation of linear viscoelastic regions.

Geopolymer materials based on magnesia-iron slags for normalization and storage of radioactive wastes

The adsorption and physicotechnical properties of geopolymer slag-alkaline solidifying mineral dispersions (SMD) materials make it possible to recommend them for radiation-shielding barriers, immobilization and storage of liquid and solid radioactive wastes, instead of the currently used technology employing ion-exchange resins and high-grade aluminate Portland cement.

Interaction of synthetic polyampholytes with disperse particles

The flocculating and stabilizing effect of synthetic polyampholytes with respect to negatively charged model latex systems as well as real mineral dispersions have been considered. It has been shown that the effectiveness of flocculation of disperse particles is maximal at the isoelectric point of polyampholytes. The experimental results obtained on interaction of negatively charged latex particles with synthetic polyampholytes, together with theoretical considerations of Joanny, allowed one to suggest a mechanism of flocculation of colloid dispersions by polyampholytes. It has been established that the interaction of butadiene-styrene latex with polyampholytes is accompanied by the removal of emulsifiers from the surface of latex particles, which in turn leads to a strong hydrophobization of the system and its precipitation.

Effectiveness of the Acidizing Treatment in Wells Based on the Petrographic Results of Thin-Section Acidizing Experiments

The acidizing treatment is a method usually used for the enhancement of productivity in oil-gas fields. Treating thin-sections for microscopic petrographic analyses with common acids, establishes the solubility and dispersion of minerals, as well as secondary formation damage. The best results were achieved by treating carbonate rocks and rocks with carbonate constituents. Siliceous minerals, such as quartz and micas are not dissolved, but the solubility of feldspars increases with the Ca-component in plagioclase and thc degree or alteration. Clay minerals are subject to mechanical disintegration which causes further formation damage. Anhydrite and opaque minerals are insoluble.

Chemical manipulation of soil for sealing landfills

The aim of this work was to seek a cost-effective method of limiting seepage from sanitary landfills by chemically inducing a low permeability in soil on site instead of resorting to expensive clay liners or geomembranes. The soil chemical treatment was based on the dispersion and flocculation of clay minerals, as well as the mobilisation and precipitation of humic compounds. In preliminary experiments with several contrasting soils, dispersion and subsequent flocculation were achieved by chemical treatment, and Na 2CO 3 and gypsum were selected as the most effective dispersant and flocculant, respectively. Soils were packed in columns in which a layer of soil with and without gypsum amendment was covered by untreated soil. The columns were then leached with Na 2CO 3 solution (usually 0.1 M Na) under a head of 100 cm. The characteristic result for most soils was a reduction in hydraulic conductivity to values close to and below the 10 −7 cm s −1 threshold widely considered to be acceptable for clay liners. Replacement of the Na 2CO 3 with liquids which favour flocculation, however, led to the enhancement of hydraulic conductivity. Very sandy or structurally stable soils were highly permeable unless a small amount of humate was added. Although the technique is not claimed to be suitable as a substitute for the methods currently used to line landfills, it does offer a very much cheaper alternative in situations where the cost of conventional methods is prohibitive.

Dynamical Studies of Aqueous Clay Mineral Dispersions by X-ray Microscopy

Dynamical Studies of Aqueous Clay Mineral Dispersions by X-ray Microscopy