Grain Size Classes Research Articles

Совершенствование реагентных режимов флотации руд сложного вещественного состава

Pyrite copper-zinc (sulfide) and polymetallic ores in Russia are complex and rebellious mineral raw materials. The main processing technology for such ores is flotation. Enhancement of the flotation technology for such mineral raw materials is currently performed in several directions. The practice of copper-zinc ore processing proves that obtaining highquality zinc and pyrite concentrates is impossible without the use of various modifiers in the sphalerite and pyrite flotation process. Such reagents are copper (II), zinc and iron (II) sulfates in the alkali-calcic medium. Therefore, research was carried out to study floatation properties of sphalerite and pyrite in the alkali-calcic medium with addition of one of the indicated sulfates to the mineral flotation process. The effect of each of the sulfates of copper (II), zinc and iron (II) on the flotation properties of sphalerite and pyrite was studied during flotation of the mineral with butyl xanthate and dithiophosphate at pH equal to 8, 10, and 12. The aim of this work was to study the effect of the sulfhydryl collectors in presence of copper sulfates, zinc and iron for flotation of sphalerite and pyrite with the grain-size class of 0.074 + 0.044 mm from one of the Russian deposits.

Investigation of old waste dump composition of lean gold-bearing ores from the Golden Pride Project (GPP) mining operation in Nzega district, Tanzania

The search for alternative sources of useful minerals is a pressing issue. One such possible source is the processing of lean gold-bearing ores, which previously did not seem feasible to exploit for subsoil users, leading to their disposal in off-balance ore dumps. Processing these resources becomes economically viable as gold prices rise and processing technologies improve over time. This paper presents the elemental and mineralogical composition of lean gold-bearing ore dumps from the Golden Pride Project (GPP) mining operation in Tanzania’s Lihendo district. This area contains an old dump of lean gold-bearing ores, weighing approximately 1.4 million tons. Extracting valuable components from lean mineral raw materials is a current priority. Sampling was conducted to study the dumps. Boreholes were drilled to a depth of 1 m, covering a total sampling area of 20 ha; 18 samples, each averaging 3 kg in weight, were collected. The results of X-ray fluorescence analysis (XRF) indicated the presence of Fe, S, Si, Ca, Ca, Mn, Cu, Al, Cr, Ti, As, and Ag in the collected samples. X-ray diffraction (XRD) analysis revealed that the main minerals in the dumps are muscovite, kaolinite, quartz, montimorillonite, and goethite. The average gold grade in the selected samples is 0.72 g/t. Studies of the grain-size distribution and gold distribution by grain-size classes after ore grinding demonstrated that the majority of gold (74%) is in the −75 μm class. In the initial mineral material of the dumps, the share of the +30-50 mm grain-size class is 81%. The paper proposes potential methods for processing lean dumps of gold-bearing ores. One such methods involves crushing the dump material, separating the −75 μm class, and subjecting it to direct leaching or leaching using “carbon-in-pulp” technique. Heap leaching appears to be the most promising method for extracting gold from such dumps in terms of technical and economic feasibility. Positive experience has been reported in applying this process to ores of similar mineralogical type.

Numerical modelling of tidal sediment dynamics in the Bay of Brest over the Holocene: How the use of a process-based model over paleoenvironmental reconstitutions can help understand long-term tidal deposits?

Long-term sedimentary infill of tide-dominated estuaries remains poorly understood. The main issue is the time-scale gap between the tidal process (hourly variations) and sedimentary layer formation (hundreds to thousands of years). Hydrodynamics induced by tides are responsible for intense remobilization of sedimentary layers inside estuaries and thus only partial sedimentary records are available. This consequently complicates understanding and interpreting the influence of hydrodynamic forcings via the preserved sedimentary deposits, as well as their chronology. Numerical modelling would appear to be the most-appropriate solution to overcome the lack of sediment deposit preservation. Hydro-sediment modelling explicitly simulates the impact of tidal processes on sediments. However, simulations time-span of these models are currently limited to decades, without simplification or schematization of the tide impact on sediments. This study (and Olivier et al., 2021) exposes a methodology exploring the evolution of sediment dynamics induced by tide over large time-scales (e.g. a transgression, ∼10 ka). The aim is to use sedimentary records to identify and rebuild each key paleoenvironments of the sediment infilling in a tide-dominated estuary (defined as seafloor morphology and sea-level), in order to run them through hydro-sedimentary simulations (MARS3D/MUSTANG). The Bay of Brest is the area selected to test the methodology. Four paleoenvironments defined by distinct sea-level and seafloor scenarios are used to study the evolution of tidal-current impact on the erosion/deposition patterns over the last 9000 years. Simulation results were compared with sedimentary records in terms of: sedimentation rates, distribution of erosion/deposition patterns (as deduced from seismic records) and distribution of grain-size classes (comparison with cores). Simulation results allowed to: (I) explain most of the sediment distribution for each sedimentary unit, reconstruct tide influence on the Holocene infilling of the Bay of Brest over 9 ka; (II) discuss the evolution of the influence of sediment supply sources; (III) highlight the spatial evolution of erosion and deposition, and the limit between cohesive and non-cohesive deposits, which evolve with tidal prism increase in relation to the active-flow section width in the Bay of Brest: when fast and significant expansion of the active-flow section width occurs (e.g. inundation of extended terraces becoming subtidal) those boundaries move down-estuary, while the opposite occurs when the increase of active-flow section width remains low during sea-level rise.

Sensitive Grain-Size Components of Last Glacial Loess on Chinese Loess Plateau and Their Response to East Asian Winter Monsoon

Chinese loess provides the most detailed terrestrial records of paleoclimate changes. We employed the grain-size components of aeolian sediments to reconstruct the history of the East Asian winter monsoon (EAWM) on the Chinese Loess Plateau (CLP). Here, using the grain-size class vs. standard deviation method, we extracted the environmentally sensitive grain-size components of nine last glacial loess sections. The grain-size class vs. standard deviation diagrams showed two major grain-size components (fine and coarse), which varied from section to section. Material resource distances and post-depositional pedogenesis were the main factors affecting environmentally sensitive grain-size components. The coarse grain-size components of the Yulin, Baicaoyuan, Xifeng, and Luochuan sections were influenced by the transportation distance, while we attributed the fine grain-size components of the Weinan, Shaoling, Duanjiapo, and Chaona sections to pedogenesis. At the same time, the Mianchi section’s sensitive grain-size component was also coarse, and was affected by the local circulation from the nearby Yellow River terrace. Our comparison of sensitive grain-size components and EAWM revealed that the coarse grain-size components were progressively finer along with the EAWM from the northwest to the southeast on the CLP, and they can be regarded as the most suitable proxy indicator of the EAWM on the CLP.

Investigating Metals and Metalloids in Soil at Micrometric Scale Using µ-XRF Spectroscopy—A Case Study

Micrometric 2D mapping of distinct elements was performed in distinct soil grain-size fractions of a sample using the micro-X-ray Fluorescence (µ-XRF) technique. The sample was collected in the vicinity of São Domingos, an old mine of massive sulphide minerals located in the Portuguese Iberian Pyrite Belt. As expected, elemental high-grade concentrations of distinct metals and metalloids in the dependence of the existent natural geochemical anomaly were detected. Clustering and k-means statistical analysis were developed considering Red–Green–Blue (RGB) pixel proportions in the produced 2D micrometric image maps, allowing for the identification of elemental spatial distributions at 2D. The results evidence how elemental composition varies significantly at the micrometric scale per grain-size class, and how chemical elements present irregular spatial distributions in the direct dependence of distinct mineral spatial distributions. Due to this fact, elemental composition is more differentiated in coarser grain-size classes, whereas griding-milled fraction does not always represent the average of all partial grain-size fractions. Despite the complexity of the performed analysis, the achieved results evidence the suitability of µ-XRF to characterize natural, heterogeneous, granular soils samples at the micrometric scale, being a very promising investigation technique of high resolution.

Confidence of a k-Nearest Neighbors Python Algorithm for the 3D Visualization of Sedimentary Porous Media

In a previous paper, the authors implemented a machine learning k-nearest neighbors (KNN) algorithm and Python libraries to create two 3D interactive models of the stratigraphic architecture of the Quaternary onshore Llobregat River Delta (NE Spain) for groundwater exploration purposes. The main limitation of this previous paper was its lack of routines for evaluating the confidence of the 3D models. Building from the previous paper, this paper refines the programming code and introduces an additional algorithm to evaluate the confidence of the KNN predictions. A variant of the Similarity Ratio method was used to quantify the KNN prediction confidence. This variant used weights that were inversely proportional to the distance between each grain-size class and the inferred point to work out a value that played the role of similarity. While the KNN algorithm and Python libraries demonstrated their efficacy for obtaining 3D models of the stratigraphic arrangement of sedimentary porous media, the KNN prediction confidence verified the certainty of the 3D models. In the Llobregat River Delta, the KNN prediction confidence at each prospecting depth was a function of the available data density at that depth. As expected, the KNN prediction confidence decreased according to the decreasing data density at lower depths. The obtained average-weighted confidence was in the 0.44−0.53 range for gravel bodies at prospecting depths in the 12.7−72.4 m b.s.l. range and was in the 0.42−0.55 range for coarse sand bodies at prospecting depths in the 4.6−83.9 m b.s.l. range. In a couple of cases, spurious average-weighted confidences of 0.29 in one gravel body and 0.30 in one coarse sand body were obtained. These figures were interpreted as the result of the quite different weights of neighbors from different grain-size classes at short distances. The KNN algorithm confidence has proven its suitability for identifying these anomalous results in the supposedly well-depurated grain-size database used in this study. The introduced KNN algorithm confidence quantifies the reliability of the 3D interactive models, which is a necessary stage to make decisions in economic and environmental geology. In the Llobregat River Delta, this quantification clearly improves groundwater exploration predictability.

РЕСУРСЫ БАРИТА, ЦВЕТНЫХ И БЛАГОРОДНЫХ МЕТАЛЛОВ В ХВОСТОХРАНИЛИЩЕ ТАЛМОВСКИЕ ПЕСКИ: МИНЕРАЛОГО-ГЕОХИМИЧЕСКИЕ И ГЕОФИЗИЧЕСКИЕ ДАННЫЕ

The estimation of barite resources (BaSO4) as well as resources of metals (Au, Ag, Cu, Zn, Pb) was made with the help of modern precision research methods at the Talmovskie Peskitailing dump (Salair Ridge). Processed ores at the tailings dump are characterized by a large vertical heterogeneity; primary (substantially non-oxidized) and oxidized sands are distinguished with Bacontents of 39 and 35 %, respectively. Grain-size classes lower 0.25 mm are the most productive from the point of view of barite. Such occurrence forms and typomorphic characteristics as color, morphology, grain size distribution, mineral paragenesis and inclusions are described for barite and metals. Geoelectric measurements have shown a horizontally-layered structure of the tailing dump, where the values of ER (21–50 Ohm•m) corresponds to the friable oxidized matter of low humidity (up to the depth of 70 cm), 0.1–20 Ohm•m – to primary, substantially non-oxidized matter. According to the results of electrical resistivity tomography, the volumes of both media were determined (48,000 and 53,000 cu), that, in comparison with the data on the concentrations of Ba, Pb, Cu, Zn, Au, Ag in them, made it possible to calculate the resources of metals within the studied area and, in some approximation, in the entire storage.

Metamorphic Ages of the Jurassic Accretionary Complexes in the Kanto Mountains, Central Japan, Determined by K–Ar Dating of Illite: Implications for the Tectonic Relationship between the Chichibu and Sanbagawa Belts

To determine the metamorphic ages of the accretionary complexes in the Northern Chichibu Belt in SW Japan, K–Ar dating was conducted using weakly metamorphosed sedimentary rocks collected from the Kanto Mountains, Central Japan. Whole-rock ages were obtained for chert and red shale samples, and the mineral ages of fine-grained illite with a grain size of less than 4 μm were obtained for chert, red shale, mudstone, acidic tuff, and basic tuff. The K–Ar ages of chert and red shale presented large variations, with systematically older ages compared to those of mudstone and tuff in the same strata. The influence of submarine hydrothermal activities on chert and red shale before subduction is a possible cause of this deviation. The illite samples, which were fractionated into four grain-size classes using a suspension method, yielded older ages and higher illite crystallinity (i.e., smaller values of Kübler’s crystallinity index) for larger grain-size classes. The peak metamorphic ages were determined from the K–Ar ages of the 3–4 μm class illite in mudstone and tuff. The Late Jurassic to the Earliest Cretaceous accretionary complex of the lowest structural unit (Kashiwagi Unit) was dated within a small range between 117–110 Ma, which is distinctly older than the K–Ar ages of white mica reported from the Sanbagawa Belt. The peak metamorphic age of acidic tuff (113 Ma) at the type locality of the Mikabu Greenstones indicates that the subducted Mikabu seamount is a constituent of the Kashiwagi Unit. The peak metamorphic ages of the Manba and Kamiyoshida Units were obtained as 132–107 Ma and 163–144 Ma, respectively. Major structural discontinuity is suggested within the Middle Jurassic accretionary complexes.

Mineralogical and technological features and patterns of selective disintegration of ferruginous quartzites of the Mikhailovskoye deposit

The growing demand for ferrous metallurgy products necessitates the introduction of technologies that increase the efficiency of the processing of iron-bearing raw materials. A promising trend in this area is the implementation of solutions based on the possibility of selective disintegration of ores. The purpose of this work was to establish the laws of selective disintegration of ferruginous quartzites based on the results of the study of mineralogical and technological properties of raw materials. We present data on the study of mineralogical and technological features of ferruginous quartzites of the Mikhailovskoye deposit. The data were obtained using X-ray fluorescence analysis and automated mineralogical analysis. Based on studies of the nature of dissemination and the size of grains of rock-forming and ore minerals, the tasks of ore preparation are formulated. The parameters for the iron and silicon oxide distribution by grain-size classes in the grinding products were established during the study. Based on empirical dependences, the grain size of grinding was predicted, at which the most effective release of intergrowths of ore minerals and their minimum transition to the size class of –44 µm should be achieved.

Determining the rational operating parameters for granite crushing to obtain cubiform crushed stone

Purpose. Determining the rational operating parameters for granite crushing under impact in the field of centrifugal forces to obtain cubiform crushed stone. In order to achieve the purpose set, the task is to determine the operating parameters for obtaining the main grain-size classes: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm. Methods. The crushing process of granite crushed stone is studied in the conditions of the Kolomoievskyi Granite Quarry, Dnipropetrovsk region. Granite crushed stone with an initial grain-size of 100.0-0.0 mm and strength grade of M1400 is subjected to crushing. The accelerating rotor rotation frequency is the design value n = 200-1200 min-1. Fine crushing of granite is performed in a centrifugal-impact crusher by a free impact in the field of centrifugal forces. Findings. The optimal speed modes of centrifugal crusher operation, which provide the production of high-quality crushed stone with a maximum content of 90-95% cubiform fractions, have been substantiated. Originality. The yield dependences have been obtained of the grain-size classes: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm depending on the speed mode of the centrifugal crusher operation. Practical implications. The operating parameters for obtaining the main grain-size classes of cubiform crushed stone from granite have been determined: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm. In particular, it has been determined that for the production of cubiform crushed stone with -50.0 + 20.0 mm grain-size, the rotor rotation reasonable speed is 400-500 min-1 (the speed of material departure from the accelerating rotor is 45-50 m/sec); for cubiform crushed stone of -40.0 + 20.0 mm grain-size, the speed mode is 200 min-1 (25 m/sec); for cubiform crushed stone of -20.0 + 10.0 mm grain-size – 600-650 min-1 (70-80 m/sec), respectively. The maximum content of cubiform fractions in the -20.0 + 10.0 mm grain-size class is 95%, which is achieved at a rotor speed of 650-700 min-1 (departure speed is 75-80 m/sec). The maximum content of cubiform fractions in the -10.0 mm grain-size class is 94-95%, which is achieved at the accelerating rotor speed within 700-800 min-1 (departure speed is 70-80 m/sec). The obtained data make it possible to practically choose a rational speed mode of the centri-fugal-impact crusher operation to obtain the maximum yield of cubiform crushed stone.

Distribution of non-uniform particles in an open channel flow from the concept of mixing length

This study deals with unsteady transport of suspended sediment in a fluid flow through an open channel that carries non-uniform particles coming from erodible sediment beds in which the flow is considered to be uniform and time-independent. To that purpose, the advection-diffusion equation is modified for the i-th grain-size class. The hiding and hindering effects caused by the interactions between non-uniform sediment particles have been taken into account through the modified expression of settling velocity. Additionally, the study utilizes the concentration-dependent expression of mixing length, which has been used previously for the transport of uniform sediment particles. The reference level for each non-uniform grain-size class has been calculated by determining the average saltation height of that class of grain. The effects of incipient motion probability, non-ceasing possibility and particle pick-up probability are taken into account while computing the reference concentration for each grain-size class. The governing equation has been solved numerically by the fourth order Runge-Kutta method. The temporal evolution of the grain-size distribution over a sediment bed has been shown at different heights. The findings indicate that starting from a unimodal bed distribution, a bimodal distribution of grain-size with one strong peak and one weak peak evolves to a bimodal distribution with two strong peaks as the vertical height increases. The effects of mixing length and modified settling velocity on the concentration profiles of non-uniform sediment particles have been shown. Both the effects result in a decrease in the magnitude of the concentration profile. Due to lack of data for unsteady transport, the obtained solution has been compared with the experimental data for steady transport of non-uniform grain-size particles at a sufficiently large time. Because the model reaches steady state after a sufficiently long time, has been shown through the analysis of relative change in concentration over time. Close agreement has been observed in all the cases. Also, the efficacy of the considered effects has been shown through the error analysis. The main advantage of the study is that, unlike most of the previous studies, the present model is able to predict the grain-size distribution in suspension without having any fitting parameters.

Potential of Using Waste Incinerator Slag to Sequester Carbon Dioxide

Data on conditions and volumes of slag formation resulting from waste fuel incineration is presented, technological schemes of processing and disposal are made including carbon dioxide fixation. Results of gravitational-magnetic slag enrichment to process polymetallic bulk concentrate are achieved. Granulometric, chemical and mineral composition of fresh and unused slags resulting from waste incineration were measured. Differences of slag material composition depending on grain-size class were identified. Reaction equations of slag carbonization were studied. Reactivity of slag phases with respect to carbonic oxide was assessed. Carbonization potential of unused and fresh slags resulting from waste incineration was calculated depending on grain-size class.

Reconstruction of flow conditions from 2004 Indian Ocean tsunami deposits at the Phra Thong island using a deep neural network inverse model

Abstract. The 2004 Indian Ocean tsunami caused significant economic losses and a large number of fatalities in the coastal areas. The estimation of tsunami flow conditions using inverse models has become a fundamental aspect of disaster mitigation and management. Here, a case study involving the Phra Thong island, which was affected by the 2004 Indian Ocean tsunami, in Thailand was conducted using inverse modeling that incorporates a deep neural network (DNN). The DNN inverse analysis reconstructed the values of flow conditions such as maximum inundation distance, flow velocity and maximum flow depth, as well as the sediment concentration of five grain-size classes using the thickness and grain-size distribution of the tsunami deposit from the post-tsunami survey around Phra Thong island. The quantification of uncertainty was also reported using the jackknife method. Using other previous models applied to areas in and around Phra Thong island, the predicted flow conditions were compared with the reported observed values and simulated results. The estimated depositional characteristics such as volume per unit area and grain-size distribution were in line with the measured values from the field survey. These qualitative and quantitative comparisons demonstrated that the DNN inverse model is a potential tool for estimating the physical characteristics of modern tsunamis.

Technology of Gold Extraction from Mature Dumps by Thiourea Leaching

Tajikistan has a large volume of gold-containing dumps, which on conversion to gold equals ~18 t. These dumps are products of amalgamation and cyanidation processes, resulting from treating the ores from Tarorskoe, one of the largest deposits in Tajikistan, and from a few other nearby deposits: Dzhilau, Khirskhon, and Olimpiiskoe. The mineralogical composition of the dumps is represented primarily by quartz, feldspar, and clay minerals. Their average content of gold is rather high, 2.4 g/t. Therefore, it is expedient to treat the dumps on the premises of JV Zerafshan plant (in the city of Pendzhikent, Tajikistan), which processes ores of the Tarorskoe deposit and has an unloaded technological cycle. The treatment of these dumps does not require an ore pretreatment stage, since, for the actual grain-size class (–0.074 mm, 58.11%), the content of cyanided gold is 89.7%. This work presents the results of studying the extraction of gold from the dumps by thiourea leaching. The purpose of this work is to find ways to decrease the consumption of expensive reagent thiourea. It is found that the sample of the dumps contains sorption-active minerals, which lead to the loss of gold with tails. Therefore, it is suggested that raw material should undergo a preliminary acid treatment to reduce the consumption of thiourea and sodium sulfite should be added to the pulp during carbon in thiourea leach. A high degree of extraction (~89%) is achieved when thiourea is loaded in the amount of 2 kg/t, ferric sulfate 7 kg/t, sodium sulfite 12 kg/t, and the initial concentration of sulfuric acid of 0.5% (at the stage of acid treatment). In this case, the consumption of thiourea is 0.8 kg/t. A process flow diagram for the dump treatment is proposed, which includes the following operations: preliminary acid treatment, carbon in thiourea leach, desorption, reactivation, electrolysis, and melting.

Grain size dependent distribution of different plastic types in coarse shredded mixed commercial and municipal waste

The Waste Framework Directive regulates the recycling of waste in Europe. The definition of waste is specified in different guidelines and regulations. Mixed Commercial Waste is waste from industry which is not collected separately. Currently there is little known about its composition. Mixed Municipal Waste, on the other hand, is household waste that cannot be attributed to any separately collected waste fraction (AdSLR, 2012). Both wastes are currently treated focussing on the generation of refuse-derived fuel rather than on the separation of recyclables (mainly performed for metals).The purpose of this paper is to characterise the amounts of various plastic types contained in different grain sizes of two-dimensional and three-dimensional plastics sorting fractions of both waste types. Nine types of plastics were identified as potential recycling materials for which recycling processes as well as a market are available. Both wastes were shredded, sampled and sieved into nine grain size classes (GSC). Fractions coarser than 20 mm were sorted, generating a ‘plastics-2D’ and a ‘plastics-3D’ fraction among others. The two plastics fractions were further characterised as plastic types using a near-infrared sensor and a Fourier-transform infrared spectrometer. The results reveal a potential for plastic recycling through mechanical and feedstock recycling options for the examined wastes. Certain types of plastics, of certain dimensionality, tend to come in certain grain sizes, which is essential for mechanical enrichment and discharge.

Integrating X-Ray Computed Tomography With Chemical Imaging to Quantify Mineral Re-crystallization From Granulite to Eclogite Metamorphism in the Western Italian Alps (Sesia-Lanzo Zone)

Metamorphic transformations and fabric evolution are the consequence of thermo-dynamic processes, lasting from thousands to millions of years. Relative mineral percentages, their grain size distribution, grain orientation, and grain boundary geometries are first-order parameters for dynamic modeling of metamorphic processes. To quantify these parameters, we propose a multidisciplinary approach integrating X-ray computed microtomography (µ-CT) with X-ray chemical mapping obtained from an Electron MicroProbe Analyzer (EMPA). We used a metapelitic granulite sample collected from the Alpine HP-LT metamorphic rocks of the Mt. Mucrone (Eclogitic Micaschists Complex, Sesia-Lanzo Zone, Western Alps, Italy). The heterogeneous Alpine deformation and metamorphism allowed the preservation of pre-Alpine structural and mineralogical features developed under granulite-facies conditions. The inferred granulitic mineral association is Grt + Bt + Sil + Pl + Qtz ± Ilm ± Kfs ± Wm. The subsequent pervasive static eclogite-facies re-equilibration occurred during the Alpine evolution. The inferred alpine mineral association is Wm + Omp ± Ky + Qtz+ Grt though local differences may occur, strongly controlled by chemistry of microdomains. X-ray µ-CT data extracted from on centimeter-sized samples have been analyzed to quantify the volumetric percentage and shape preferred orientation for each mineral phase. By combining tomographic phase separation with chemical variation and microstructures (i.e., different grain-size classes for the same phase and morphology of different pre-Alpine microdomains) the pre-Alpine mineralogical phases from the Alpine overprint have been distinguished and quantified. Moreover, the sample preserves 100% of the pre-Alpine granulite fabric, which surprisingly corresponds to less than 22% of the corresponding pre-Alpine metamorphic assemblages, while the Alpine eclogitic static assemblage corresponds to 78% though no new fabric is developed. This contribution demonstrates that the combined use of EMPA X-ray chemical mapping with the X-ray µ-CT shape analysis permits a dynamic approach to constrain the chemistry of the mineral phases linked to the development of metamorphic-related static and dynamic fabrics.

Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt

This article illustrates a multi-technique frontier approach for the provenance study of silt-size sediments. The mineralogical composition of low-density and heavy-mineral fractions of four samples of fine to very coarse silt deposited on the Bengal shelf was analyzed separately for six different grain-size classes by combining grain counting under an optical microscope, Raman spectroscopy, and X-ray diffraction. The geochemical composition was determined on both bulk-sediment samples and on their <5-μm classes. Such a “multiple-window” approach allowed capturing the full mineralogical information contained in each sample, as well as the size-dependent intra-sample variability of all compositional parameters. The comparison between grain-size distributions obtained by different methods highlighted a notable fallacy of laser granulometry, which markedly overestimated the size of the finest mode represented by fine silt and clay. As a test case, we chose to investigate sediments of the Bengal shelf, where detritus is fed from the Meghna estuary, formed by the joint Ganga and Brahmaputra Rivers and representing the largest single entry point of sediment in the world’s oceans. The studied samples show the typical fingerprint of orogenic detritus produced by focused erosion of collision orogens. Bengal shelf silt is characterized by a feldspatho-quartzose (F-Q) composition with a Q/F ratio decreasing from 3.0 to 1.7 with increasing grain size, plagioclase prevailing over K-feldspar, and rich transparent-heavy-mineral assemblages including mainly amphibole with epidote, and minor garnet and pyroxene. Such a detrital signature compares very closely with Brahmaputra suspended load, but mineralogical and geochemical parameters, including the anomalous decrease of the Q/F ratio with increasing grain size, consistently indicate more significant Ganga contribution for cohesive fine silt. The accurate quantitative characterization of different size fractions of Bengal shelf sediments represents an essential step to allow comparison of compositional signatures characterizing different segments of this huge source-to-sink system, from fluvial and deltaic sediments of the Himalayan foreland basin and Bengal shelf to the Bengal Fan.

Sediment transport modelling in riverine environments: on the importance of grain-size distribution, sediment density, and suspended sediment concentrations at the upstream boundary

Abstract. Hydromorphodynamic models are powerful tools for predicting the potential mobilization and transport of sediment in river ecosystems. Recent studies have shown that they are able to predict suspended sediment matter concentration in small river systems satisfactorily. However, hydro-sedimentary modelling exercises often neglect suspended sediment properties (e.g. sediment densities and grain-size distribution), which are known to directly control sediment dynamics in the water column during flood events. The main objective of this study is to assess whether a better representation of such properties leads to an improved performance in the model. The modelling approach utilizes a fully coupled hydromorphodynamic model based on TELEMAC-3D (v7p1) and an enhanced version of the sediment transport module SISYPHE (based on v7p1), which allows for a refined sediment representation (i.e. 10-class sediment mixtures instead of 2-class mixtures and distributed sediment density instead of uniform). The proposed developments of the SISYPHE model enable us to evaluate and discuss the added value of sediment representation refinement for improving sediment transport and riverbed evolution predictions. To this end, we used several model set-ups to evaluate the influence of sediment grain-size distribution, sediment density, and suspended sediment concentration at the upstream boundary on model predictions. As a test case, we simulated a flood event in a small-scale river, the Orne river in north-eastern France. Depending on the model set-up, the results show substantial discrepancies in terms of simulated bathymetry evolutions. Moreover, the model based on an enhanced configuration of the sediment grain-size distribution (10 classes of particle sizes) and with distinct densities per class outperforms the standard SISYPHE configuration, with only two sediment grain-size classes, in terms of simulated suspended sediment concentration.

Influence of chemical composition of fly-ash cenospheres on their grains size

Cenospheres, which are the by-product of hard coal combustion, are characterized by properties allowing for a broad use of this material. The article presents the results of the chemical composition analysis of the cenospheres obtained from various power plants. It has been exhibited that depending on the place of origin, their chemical composition is similar and comparable to fly ash produced in hard coal combustion. A great majority of analysed cenospheres may be classified similarly as the sialic ashes—slightly acidic. The analysis of dependence of refractoriness of the cenospheres on their chemical composition confirmed the correlation between this parameter and the content of SiO2 and Al2O3. At the same time, the content of each of the chemical components indicates a correlation with the size of the cenospheres. A trend of SiO2/Al2O3 ratio decreasing along with the increasing size of the cenospheres has been noted. Also the content of K2O and—to a lesser extent—Na2O decreases along with increasing diameter of grains. An inverse correlation was noted in case of Fe2O3. The higher the diameter of the grains, the higher the content of this component. In view of the obtained results, it should be assumed that the division of cenospheres into grain-size classes before further industrial use could extent the current range of use of this material.

Reduction of technogenic load from sludge collectors due to separation and dehydration of the stored material

Purpose: the identification of geomechanical problems of mining industry wastes accumulation and substantiation of the ways for their solution with the possibility of processing the watery technogenic feedstock. It has been shown that in order to reduce the technogenic load, it is necessary to reduce the area of land under the waste ponds and the accumulated volumes themselves of mining and enrichment wastes. It has been revealed that the mineral stock, formed from wide grain-size classes with a high content of particles less than 0.2 mm, is dewatered up to 18 – 22 % by traditional methods and is practically not classified. A mathematical model has been proposed of screening and dewatering kinetics, which takes into account comprehensively the initial distribution of particles and liquid throughout the height of the screened material layer, segregation, mixing, sifting, vibrational transportation features and change in the height of the layer. The use of technology will allow: increase the economic efficiency of enterprises; to expand the feedstock base for construction, coke and chemical industries and power industry; to solve the problems of creating additional containers for storing the wastes; to improve significantly the environmental situation in the mining and processing regions.