Clay Components Research Articles

Heat-resistant insulation film containing clay and wood components

In this paper, we prepared a novel organic–inorganic nanocomposite film with excellent insulation properties relative to the polyimide film in mild-processing conditions. The main component of the film is clay mineral and wood component, i.e., the layered silicate and poly(ethylene glycol)-modified lignin derivatives. In the nanocomposite film, an interlayer of silicate was bound by triethanolamine. Furthermore, the lignin derivatives filled the voids of the layered silicate, producing a defect-free densely packed nanocomposite film. This unique structure of the nanocomposite film provides high-thermal stability, a low thermal expansion coefficient of film consisting of clay and lignin derivatives, low gas transmittance rate, low volume/surface resistivity, and high dielectric breakdown voltage. The obtained nanocomposite film was installed in a planar-type transformer where it acted as an insulation film in the transformer coil with high dielectric breakdown voltage.

Mineralogy, geochemistry, and fluid action process of uranium deposits in the Zhiluo Formation, Ordos Basin, China

Some controversies still exist regarding the genesis of sandstone-type uranium deposits in the northeastern Ordos Basin. Herein, based on boreholes and well logging data, we selected sandstone samples representing different epigenetic alteration environments as the research object and comprehensively utilized polarizing microscopy, scanning electron microscopy, electron probe analysis, elemental analysis, and other test methods to research sandstone genesis. The main altered minerals in the sandstone of this area include limonite, pyrite, achavalite, carbonate, sulfate, clay, and uranium minerals. The complex characteristics of alteration minerals indicate multi-stage fluid mixed mineralization in this area. According to the relationship between the major elements in different types of sand bodies, the components were classified into three groups. The first is the reduction media group, including CaO, MnO, total oxygen carbon (TOC), S, U, and burning loss. The second is the detrital particle group, including SiO2, K2O, and Na2O, and the third contains the clay and volcano component group, including Fe2O3, P2O5, TiO2, FeO, MgO, and Al2O3. Among these, the content of reduction media is positively correlated with uranium enrichment, whereas detrital particles and clay components reflect the influence of alteration on the sand body composition, which indirectly affects the uranium adsorption and precipitation. Through the normalization of rare earth element (REE) chondrites, we find that the distribution patterns of REEs in rocks with different geochemical environments show a fractionation of light and heavy rare earth elements (HREEs), a right-leaning enrichment of light rare earth elements (LREEs), and relatively flat HREE. Further, via the Post Archean Australian Shale (PAAS) normalization, we observe that the mudstone of the Zhiluo Formation exhibits a relatively flat curve, whereas the sandstones have strongly positive Eu anomalies. The difference in REE values for different types of sand bodies indicates that, although all types of rocks have a similar sedimentary environment, their original sediments underwent fluid alterations such as oxidation and reduction. Based on the uranium mineralization evolution history in the study area, the water-rock reaction process and mineral-alteration sequence were determined on the basis of alteration types and elemental concentrations. Our findings provide new insight into the petrological significance, mineralogy, and geochemical composition of uranium deposits in the Ordos Basin.

Carbon coated halloysite nanotubes as efficient sulfur host materials for lithium sulfur batteries

To impede the shuttle effect of lithium sulfur (LiS) batteries and improve the battery performance, carbon coated halloysite nanotubes (HNT@C) composites were synthesized and applied as sulfur host materials for LiS batteries. The unique one-dimensional tubular structure and abundant alumina-silicates components of HNT clay were synergistically utilized to physically confine and chemically adsorb lithium polysulfides, which could play important role to suppress the shuttle effect of polysulfides. Moreover, to solve the insulating issue of HNT, conducting carbon was deposited on the surface of HNT through polydopamine (PDA) coating and pyrolysis. The electrical conductivity of HNT@C host was thus significantly enhanced. As a result, the cycling stability and rate capability of the sulfur cathode were improved. In addition, the effect of carbon content on the properties of HNT@C composites and the electrochemical performance of the sulfur cathode were investigated. With carbon content of 3%, HNT@C hosted sulfur cathode delivered an initial discharge capacity of 922.7 mAh g−1 at current rate of 0.1C. Also, the capacity still retained about 82% after 500 cycles at 1C and the corresponding capacity decay is as low as 0.036% per cycle. This work can not only extend the application of HNT clay in energy storage but also provide a low-cost and promising HNT@C host material for advanced LiS batteries.

Influence of the calcination temperature on the properties of a mica mineral as a suitability study for the use as SCM

Calcined clays as SCM have the potential of compensating the future decrease of slag and fly ash. The present work dealt with a mica mineral, a common component of raw clays, and its change of properties during calcination. Raw and at four temperature levels calcined mica were investigated on the following properties: Water absorption capacity, specific surface area, particle size distribution, lattice parameters by XRD, heat flow and Al-/Si solubility. The results showed a low ion solubility throughout all samples. Thus, the contribution to the chemical pozzolanic reaction due to calcination was low. However, mica's physical and hygroscopic properties influenced the cement hydration. Contrary to common knowledge, which predicts a decrease in water absorption capacity with a decrease in BET specific surface area, calcined mica behaved in the opposite direction. To conclude, for mica containing raw clays the calcination temperature should be lower in regard to mica's physical-hygroscopic properties, but higher in regard to pozzolanic reactivity of other phyllosilicates. Therefore, a balanced calcination temperature should be applied. These results can be used to assess their suitability as SCM in mortar and concrete.

Changes in the material composition of fluid seals of bitumen deposits during thermal effects on the productive formation

Fluid seals are the most important element of oil fields, because they prevent the spread and dispersion of hydrocarbons and contribute to the preservation of deposits. The role of the fluid seals increases in the later stages of oil field development, especially when using thermal methods of intensification. As a result, changes in the mechanical, mineralogical, and lithological properties of the fluid seal rocks can occur. The deposits of natural bitumen of the Volga-Ural petroleum province are a complex geological and geochemical object. The degree of preservation of hydrocarbon deposits is determined by the filtration characteristics of the fluid seal. The composition of the fluid seals is represented by dense clay components of the rock. The use of thermal or steam-thermal methods of exposure to hydrocarbon reservoirs, primarily affects the minerals-indicators (clay minerals of cement collectors). The results of thermal effects on the reservoir can lead to changes in the material composition, parameters of porosity and permeability of the fluid seal rocks: the clay component is destroyed with the active participation of organic matter.

Collaborative involvement of woody plant roots and rhizosphere microorganisms in the formation of pedogenetic clays.

Previous studies have described the laying down of specific B horizons in south-western Australian ecosystems. This paper presents biomolecular, morphological and physicochemical analyses elucidating the roles of specific woody plant taxa and rhizosphere bacteria in producing these phenomena. Clayey deposits within lateral root systems of eucalypts and appropriate background soil samples were collected aseptically at multiple locations on sand dunes flanking Lake Chillinup. Bacterial communities were profiled using tagged next-generation sequencing (Miseq) of the 16S rRNA gene and assigned to operational taxonomic units. Sedimentation, selective dissolution and X-ray diffraction analyses quantitatively identified clay mineral components. Comparisons were made of pedological features between the above eucalypt systems, giant podzols under proteaceous woodland on sand dunes at the study site of Jandakot and apparently similar systems observed elsewhere in the world. Bacterial communities in clay pods are highly diverse, resolving into 569 operational taxonomic units dominated by Actinobacteria at 38.0-87.4 % of the total reads. Multivariate statistical analyses of community fingerprints demonstrated substrate specificity. Differently coloured pods on the same host taxon carry distinctive microfloras correlated to diversities and abundances of Actinobacteria, Acidobacteria, Firmicutes and Proteobacteria. A number of these microbes are known to form biominerals, such as phyllosilicates, carbonates and Fe-oxides. A biogenic origin is suggested for the dominant identified mineral precipitates, namely illite and kaolinite. Comparisons of morphogenetic features of B horizons under eucalypts, tree banksias and other vegetation types show remarkably similar developmental trajectories involving pods of precipitation surrounding specialized fine rootlets and their orderly growth to form a continuous B horizon. The paper strongly supports the hypothesis that B-horizon development is mediated by highly sophisticated interactions of host plant and rhizosphere organisms in which woody plant taxa govern overall morphogenesis and supply of mineral elements for precipitation, while rhizosphere microorganisms execute biomineralization processes.

Damage quantification of archaeological pottery in Sheikh Hamad “Athribis” Sohag-Egypt

Abstract Many archaeological potteries in Sheikh Hamad (Athribis) Sohag, Egypt suffer from different processes, which led to many deterioration forms. Samples collected from Athribis were submitted to qualitative and quantitative measurements through using different techniques to evaluate their durability states. Significant information derived from these techniques prove that our materials are composed of Si, Al, Fe, Mg, K, Ca, Na and Cl as the main elements of Quartz Albite, Microcline, Calcite and Hemetite (main components of Nile clays) and Halite (main salt characterizes Egyptian land). In addition, SEM reveals that the samples are characterizes by cohesion of the granules, non homogeneous texture and different size pores in addition to degradation, dissolution features and cracks. Finally, it can be concluded that most of these artifacts are affected by two main aggressive mechanisms: their burial environment (before excavation) and aired environment (after excavation). These process that finally led to some aggressive deterioration forms.

Mechanical behavior of micaceous clays

This study aims to investigate the effect of mica content on the mechanical properties of clays. Commercially available ground mica was blended with a locally available clayey soil, at varying mica contents by mass of 5%, 10%, 15%, 20%, 25% and 30%, to artificially prepare various micaceous clay blends. The preliminary testing phase included consistency limits and standard Proctor compaction tests. The primary testing program consisted of unconfined compression (UC), direct shear (DS) and scanning electron microscopy (SEM) tests. The test results showed that the liquid and plastic limits exhibited a linear, monotonically increasing trend with increase in mica content. The rate of increase in the plastic limit, however, was found to be greater than that of the liquid limit, thereby leading to a gradual transition towards a non-plastic, cohesionless character. The soft, spongy fabric and high water demand of the mica mineral led to higher optimum water contents and lower maximum dry unit weights with increasing mica content. Under low confinement conditions, i.e. the UC test and the DS test at low normal stresses, the shear strength was adversely affected by mica. However, the closer packing of the clay and mica components in the matrix under high confinement conditions offsets the adverse effects of mica by inducing frictional resistance at the shearing interface, thus leading to improved strength resistance.

A Modified Expanded Clay as a Yielding Material in Deep Mechanized Tunnel Boring

This paper investigates the use of a modified expanded clay as a yielding fill material in the overcut behind the segmental lining. In order to match the stress-strain curves of the ideal yielding material, expanded clay of different sizes and different clay mixed components were tested. Both of the field tests and numerical calculation were conducted to evaluate the behaviour of liner in deep tunnel when the modified expanded clay was backfilled. The safety of the liner was assessed. The results show that the non-modified expanded clay offers a linear behaviour up to a deformation of 25% to 40%, and with an average limit compressive strength between 1 MPa to 5 MPa. By adding a certain percentage of polystyrene to the expanded clay, the limit compressive strength and the linear deformation phase can be modified. Polystyrene reduces the stiffness and offers a yielding section in the deformation phase, which makes the expanded clay close to an ideal yielding material. Through modification of the expanded clay, the limit compressive strength can be adjusted to an approximately 55% compressive strain. The results of field tests and numerical simulation verified the use of the modified expanded clay as a yielding material in deep tunnels.

Blue nodule on the finger

A 67-year-old woman sought treatment for a painful nodule on the perionychium of the right second finger that had rapidly enlarged over the previous year. The patient reported that the point of a lead pencil had become lodged in her skin at the age of 10 years. The nodule was blue-gray in color, 9.6 mm in maximum diameter, and unattached to the subcutaneous tissue (Fig 1). Dermoscopic examination found homogeneous blue pigmentation (HBP) over the lesion. Several dotted vessels were observed in the lesion center under higher magnification (Fig 2). Histologic findings confirmed a diagnosis of pencil-core granuloma (Fig 3).Key messageThis case displayed HBP by dermoscopy that resembled a blue nevus. HBP generally corresponds to dermal melanin granules of melanocytic tumors, such as blue nevus, but is also observed in hemangioma, dermatofibroma, and other nonmelanocytic tumors.1Longo C. Scope A. Lallas A. et al.Blue lesions.Dermatol Clin. 2013; 31: 637-647Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar Histopathologic examination found that the HBP in this case was caused by the dermal deposition of graphite and graphite accumulation within macrophages. Several cases of pencil-core granuloma have been reported to exhibit HBP on dermoscopy,2Menzies S.W. Moloney F.J. Byth K. et al.Dermoscopic evaluation of nodular melanoma.JAMA Dermatol. 2013; 149: 699-709Crossref PubMed Scopus (76) Google Scholar with a history of embedded pencil-tip graphite at the site representing a clue for correct diagnosis. However, melanoma could not be completely excluded in this case because of the dermoscopic finding of dotted vessels and the rapid size increase of the tumor. Close attention is necessary for nodular melanoma, as it frequently shows a symmetrical pigmentation pattern without pigment network.2Menzies S.W. Moloney F.J. Byth K. et al.Dermoscopic evaluation of nodular melanoma.JAMA Dermatol. 2013; 149: 699-709Crossref PubMed Scopus (76) Google Scholar Pencil-core granulomas may suddenly develop long after the initial trauma, presumably because of delayed granulomatous reactions towards the graphite, clay, wax, and other components of pencil cores.3Terasawa N. Kishimoto S. Kibe Y. Takenaka H. Yasuno H. Graphite foreign body granuloma.Br J Dermatol. 1999; 141: 774-776Google Scholar This case displayed HBP by dermoscopy that resembled a blue nevus. HBP generally corresponds to dermal melanin granules of melanocytic tumors, such as blue nevus, but is also observed in hemangioma, dermatofibroma, and other nonmelanocytic tumors.1Longo C. Scope A. Lallas A. et al.Blue lesions.Dermatol Clin. 2013; 31: 637-647Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar Histopathologic examination found that the HBP in this case was caused by the dermal deposition of graphite and graphite accumulation within macrophages. Several cases of pencil-core granuloma have been reported to exhibit HBP on dermoscopy,2Menzies S.W. Moloney F.J. Byth K. et al.Dermoscopic evaluation of nodular melanoma.JAMA Dermatol. 2013; 149: 699-709Crossref PubMed Scopus (76) Google Scholar with a history of embedded pencil-tip graphite at the site representing a clue for correct diagnosis. However, melanoma could not be completely excluded in this case because of the dermoscopic finding of dotted vessels and the rapid size increase of the tumor. Close attention is necessary for nodular melanoma, as it frequently shows a symmetrical pigmentation pattern without pigment network.2Menzies S.W. Moloney F.J. Byth K. et al.Dermoscopic evaluation of nodular melanoma.JAMA Dermatol. 2013; 149: 699-709Crossref PubMed Scopus (76) Google Scholar Pencil-core granulomas may suddenly develop long after the initial trauma, presumably because of delayed granulomatous reactions towards the graphite, clay, wax, and other components of pencil cores.3Terasawa N. Kishimoto S. Kibe Y. Takenaka H. Yasuno H. Graphite foreign body granuloma.Br J Dermatol. 1999; 141: 774-776Google Scholar

Pliocene-Pleistocene magneto-cyclostratigraphy of IODP Site U1499 and implications for climate-driven sedimentation in the northern South China Sea

A high-resolution astronomical-tuned magnetostratigraphy was obtained from a continuous 333-m succession recovered at International Ocean Discovery Program (IODP) Hole U1499A in the north margin of the South China Sea (SCS) during joint Legs 367 & 368. A total of 12 magnetic reversals are identified through the Pliocene and Pleistocene. The cycle analysis of natural gamma ray (NGR) data shows an average suite of ca. 33 m and 8 m wavelengths with lesser 1.5-m cycles, which are consistent with the ratios of Milankovitch orbital-climate oscillations caused by long eccentricity (405 kyr), short eccentricity (~100 kyr), and precession (~20 kyr). The astronomical-tuned magnetostratigraphy correlates with nearly all features of the Pliocene-Pleistocene geomagnetic polarity time scale. There was a significant shift to ~100-kyr-dominated cyclicity at ca. 1.3 Ma, which marks the onset of the Mid-Pleistocene Transition, during which the influx of the clay component decreased. A general enrichment in silt-sand influx during the past 0.4 Myr was punctuated by surges in coarser-grained components (lowest NGR) during or at the end of each major global glacial event. Comparison to a high-resolution sediment record spanning the Pliocene-Pleistocene on the southern margin of the SCS (ODP Site 1143) indicates common intervals of changing rates of sediment accumulation. In both regions, there are relatively lower rates of sediment accumulation during the late Zanclean (mid-Pliocene; ca. 4.1 to 3.6 Ma), early Gelasian (ca. 2.5 to 2.0 Ma), early Calabrian (ca. 1.6 to 1.4 Ma) and the earliest Middle Pleistocene (ca. 0.6 Ma). The merger of magnetostratigraphy, cyclostratigraphy and the NGR record to produce a high-resolution profile of bulk sediment accumulation rates and relative clay to sand-silt components is a powerful tool and climate proxy to reconstruct the general history of sediment input into the SCS and its relationships to East Asia monsoon and tectonic evolution.

ТАМПОНАЖНЫЕ СОСТАВЫ ПОНИЖЕННОЙ ПЛОТНОСТИ ДЛЯ ЦЕМЕНТИРОВАНИЯ СКВАЖИН В УСЛОВИЯХ АНОМАЛЬНО НИЗКИХ ПЛАСТОВЫХ ДАВЛЕНИЙ

The paper considers variants of lightweight cement compositions with additives of various substances, such as clay components, ash systems, silica additives, kerogen, gilsonite, microspheres, as well as the process of cement slurry aeration. Recommendations on the use of compositions in different conditions are presented. A decrease in the density of the solution is achieved not only due to the low density of the materials used, but also as a result of an increase in the water-cement ratio. In such conditions, it is not possible to ensure the formation of a durable and impermeable cement stone in the well, which creates high quality inter-reservoir insulation. The characteristics of the physical and mechanical properties of existing lightening additives are given, which allows determining the most rational conditions for the use of cement slurries for improvement of the well cementing quality.

The influence of soil texture on the course of volume changes of soil

Volume changes of soil associated with soil moisture changes are caused by the presence of clay minerals from illite and montmorillonite groups. Clay minerals are found in the so-called clay soil component which can be quantified by laboratory analysis of the soil particle-size distribution. Consequently, the potential for volume changes in soil can be assessed from soil texture. In our study, 172 soil samples with different textures were used to measure dependencies between volume changes in soil and changes in soil moisture under laboratory conditions. The samples were collected from 11 sites in the Eastern Slovak Lowland. On the basis of the measurements, 10 mathematical models were created to compute the correlation between volume changes of soil and soil moisture content and texture. The highest accuracy was obtained with the model which assumes the content of particles < 0.002 mm. When comparing the clay particles < 0.001 mm (colloidal clay) with the particles < 0.002 mm (colloidal + physical clay) it was also found that the particles < 0.002 mm have a larger impact on the volume changes of soil than the particles < 0.001. The inclusion of particles > 0.002 mm (silt + sand) into the models resulted in either no or only negligible refinement of the soil volume change calculations.

Mineralogy of Clay Components of Aquic arenic paleudults Soils of Akamkpa, Southeastern Nigeria

Mineralogy of Clay Components of Aquic arenic paleudults Soils of Akamkpa, Southeastern Nigeria

Measurement of Complex Dielectric Permittivity of Quartz Systems

The article describes the problem of the experimental determination of complex dielectric permittivity for natural, activated, and modified quartz systems. The results of determination of specific surface, complex dielectric permittivity, sands porosity are presented in this article. The authors obtained the empirical equation of complex dielectric permittivity calculation for natural, activated, and modified quartz sands, taking into account the effect of moisture, specific surface, porosity, impurities content into consideration. The modification of the sand surface by means of mechanical beneficiation and ultrasonic treatment leads to reduction of complex dielectric permittivity and specific surface, thus contributing to the increase of the active centers quantity on the sands surface. The modification of the sand surface by polyvinyl alcohol aqueous solution leads to increase of complex dielectric permittivity. Polyvinyl alcohol aqueous solution modification envisages the creation of new active centers by oligomers inoculation to the surface and blocking the clay component and authigenous film ingredients. Among the considered methods, ultrasonic treatment in aqueous solution and mechanical beneficiation are the most efficient and technologically acceptable ways of activation.

Indian Monsoonal Variations During the Past 80 Kyr Recorded in NGHP‐02 Hole 19B, Western Bay of Bengal: Implications From Chemical and Mineral Properties

AbstractDetailed reconstruction of Indian summer monsoons is necessary to better understand the late Quaternary climate history of the Bay of Bengal and Indian peninsula. We established a chronostratigraphy for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BP and examined major and trace element compositions and clay mineral components of the sediments. Higher δ18O values, lower TiO2 contents, and weaker weathering in the sediment source area during marine isotope stages (MIS) 2 and 4 compared to MIS 1, 3, and 5 are explained by increased Indian summer monsoonal precipitation and river discharge around the western Bay of Bengal. Clay mineral and chemical components indicate a felsic sediment source, suggesting the Precambrian gneissic complex of the eastern Indian peninsula as the dominant sediment source at this site since 80 kyr. Trace element ratios (Cr/Th, Th/Sc, Th/Co, La/Cr, and Eu/Eu*) indicate increased sediment contributions from mafic rocks during MIS 2 and 4. We interpret these results as reflecting the changing influences of the eastern and western branches of the Indian summer monsoon and a greater decrease in rainfall in the eastern and northeastern parts of the Indian peninsula than in the western part during MIS 2 and 4.

Morphogenesis and quantification of the pore space in a tephra-palaeosol sequence in Tlaxcala, central Mexico

Tepetates are indurated subsoil horizons developed in tephra-derived materials in various parts of the Trans-Mexican Volcanic Belt. The term ‘tepetate’ includes fragipans, duripans, pedosediments and saprolites, derived from vitric rhyolitic tuff, Pleistocene volcanic ashes or pyroclastic flows. All soils with tepetates are at high risk of erosion and so they have been intensively studied for decades. The tepetates are common in Tlaxcala State of central Mexico, being formed under Ustic Isomesic soil climate. The aim of this investigation was to characterise the pore space of fragipan-type tepetates and the role of clay components in their formation. We studied porosity of tepetate from a tephra-palaeosol sequence in the north of Tlaxcala State, in undisturbed soil samples. Observations of pore space were made in 2D and 3D by analysing microscope images of thin sections and cross-sectional images from a computed tomography scanner. In the thin sections we also identified and described clay illuvial pedofeatures. Micromorphological observations showed two main pore types. Small rounded pores had a homogeneous distribution and were probably formed before the clay illuviation process that took place in a palaeosol formed on the tepetate material. The distribution pattern of the small pores in the studied tepetate was similar to that in the fragic horizon, which was probably formed by a hydro-consolidation process. Large crack-pores were formed during the palaeosol formation. Later these large pores were filled by illuvial clay coatings and so we conclude that each tepetate was part of the set of Bt horizons in the palaeosols of Luvisol type.

Technology of Gold-Containing Technogenic Raw Materials Processing Using the Electric Explosion Method

The paper shows fundamental possibility of processing of gold-bearing technogenic raw materials using the method of electric explosion. A series of experiments using a laboratory and pilot-production high-voltage pulsed discharge (HVPD) installation for the processes of enrichment of gold-bearing mineral raw materials of Komsomolsk mine tailings in Kemerovo region is conducted with a relatively low energy electrical discharge in the pulse of up to 112.5 Joules and the cost of electric power of about 1.5 kW/ton of raw material, that allows complete destruction of clay components agglomerations to less than 0.045 mm (micron and submicron sizes). Solid minerals such as quartz are simultaneously destroyed by defects in the grains and withdrawn from the installation with water, thus increasing gold degree of the concentrate. The results of particle-size and X-ray structural analyses of gold-bearing mineral raw materials of Komsomolsk mine tailings in Kemerovo region obtained by the method of electric explosion are discussed.

Mineralogical and geochemical features of karst bauxites from Poci (western Henan, China), implications for parental affinity and bauxitization

The Poci bauxite deposits in western Henan, China, are hosted in the lower member of Upper Carboniferous Benxi Formation, unconformably overlying upon the paleokarst surface of the Ordovician Majiagou Formation. The orebodies comprise a high-grade bauxite horizon (characterized by the association of diaspore-illite-anatase) and a basal iron-rich horizon (diaspore-goethite-hematite-illite-anatase), sandwiched between the overlying clayey layer (illite-diaspore-goethite-anatase) and the underlying clayey layer (illite-diaspore-microcline-goethite). Geochemical investigations reveal that Rb, Cs, Ba, Cu, Zn are depleted, while B, Ga, Bi, V, Sc, Zr, Hf, Nb, Ta, W, U and Th are enriched in bauxite horizons. B is highly enriched in bauxite ores and clays (contents 176–1061 ppm) and positively associated with SiO2, indicating B is mainly hosted in clay components, e.g. dominantly illite, which are considered a mixture of authigenic minerals transformed from kaolinites during diagenesis and unaltered detrital minerals. Mass change calculations reveal that Hf, Zr, Nb, Ta, U, Th, Sc, Cr, and Ga are stable relative to TiO2 during the bauxitization process, indicating these elements are mainly associated with anatase and diaspore. The bauxite horizons and the underlying clays are more enriched in total REE contents (ΣREEs) and display more intense LREE/HREE fractionation than the overlying clays. Provenance analysis shows that parental materials of Poci bauxites were mainly derived from felsic-dominated igneous rocks along the southern margins of the North China Craton, with minor contribution from siliciclastic sedimentary rocks and argillaceous components of underlying carbonates. A conceptual model is proposed for the formation and evolution of Poci bauxites. Uplift caused by the North Qinling orogenesis along the southwestern margin of NCC led to the formation of karstic topography, allowing aluminum-rich source materials to be transported to the low karst plain and transformed into incipient bauxites under hot and humid tropical conditions. When the platform was submerged, Fe2+ ions were released from Fe/Al oxides/hydroxides under the reducing conditions associated with bacteria activity in an organic-rich environment, and redeposited as pyrites and siderites, generating a high-grade bauxite horizon and an iron-rich bauxite horizon. This marine modification resulted in further aluminum enrichment of bauxite ores.

Integrated analysis of fault sealing capabilities when studying and mapping hydrocarbon traps in the Dnieper-Donets Depression

This paper demonstrates how a set of advanced technologies provided a better understanding of the geological structure of the Solokha gas condensate field and underground gas storage located in onshore Ukraine. In particular, these technologies helped us improve the process of hydrocarbon trap delineation and subsequent exploration well planning in this area. The study area is structurally complex because it is located in the central part of the axial zone of the Dnieper-Donets Depression (DDD). This part of the DDD is characterized by active halokinesis that has produced morphologically developed salt bodies and associated with them plicative and disjunctive deformations of the host rocks. The structure of the area has to a large extent been formed under the impact of one of such bodies, the closely located and actively developed Bakeyski diapir. The workflow used consists in synergic integration of high-quality 3D seismic data processing, detailed structural and stratigraphic interpretation and seismic inversion combined with pore pressure measurements in wells, lithotype clustering using Kohonen self-organizing maps, and fault seal analysis. A ramified network of faults, which plays an important role in the study area, formed independent tectonic traps in the Middle Jurassic sediments of the Bayosian age and led to the compartmentalization of one of the stratigraphic traps in the Lower Carboniferous sediments of the Visean age. To analyze sealing capabilities of these faults, Allan diagrams and Shale Gouge Ratio are used. The first of these methods is based on the juxtaposition of permeable and impermeable rocks on both sides of the fault, and the second, more advanced, is based on the calculation of the percentage of the clay component of all rocks that have slipped along the fault past a given point.