Mica Minerals Research Articles

MINERALS AND SEDIMENTARY CHARACTERISTICS OF QUATERNARY SEDIMENTS OF DIFFERENT REGIONS IN SOUTHERN IRAQ

This study tries to evaluate the sediments of Quaternary deposits with a depth from 8 to 24 meters, and determine the lights and heavy minerals with their origin. Three boreholes; Basrah, Thi-Qar and Missan, were selected, based on the grain size analysis of samples, three types of sediment were identified: silt, sandy silt, and silty sand. The statistical size parameters were applied to determine the energy and sedimentation environment, showed that the sediments of the study area were deposited in low-energy conditions. The sorting values ranged from poorly to very poorly, while the skewness ranged from strongly fine to near symmetrical skewed and kurtosis values ranged from platy to leptokurtic. The results of heavy minerals analysis proved the very low values comparative with light ones; Opaque was predominant in all study sites, accounting for about 50% of the heavy minerals and divided to mica minerals and Chlorite, Pyroxene, Amphibole, Zircon, Epidote, and Garnet, while Kyanite, Tourmaline and Staurolite. The light minerals are dominated by carbonate and quartz with few amounts of chert, evaporates, Feldspar, rock fragments and light muscovite. The difference in the values and diversity of heavy minerals in the study area indicates the multiple sources contributing to the deposits of the Mesopotamia Plain. The sources are limited between the rivers of Tigris, Euphrates and Shatt Al-Arab and the dust-fallouts, as well as the nearest formations and the Arabian shield.

南西インド洋海嶺Atlantis Bankの斑レイ岩類中のMg-Fe雲母と変質鉱物

南西インド洋海嶺Atlantis Bankの斑レイ岩類中のMg-Fe雲母と変質鉱物

АНАЛІЗ ОСОБЛИВОСТЕЙ ПОКЛАДІВ ГАЗУ УЩІЛЬНЕНИХ ПОРІД-КОЛЕКТОРІВ ТА ЛІТОЛОГО-ПЕТРОФІЗИЧНА ОЦІНКА ВІДКЛАДІВ ВЕРХНЬОГО ТА СЕРЕДНЬОГО КАРБОНУ СВЯТОГІРСЬКОЇ ПЛОЩІ

The paper concerns the analysis of the world practice in the study of tight gas reservoirs and some of their lithological and petrophysical properties are demonstrated on the example of Svyatogorska Area perspective intervals. The purpose of this work is to establish the features of petrophysical properties of tight gas reservoirs from the upper and middle Carboniferous strata of Svyatogorska area according to laboratory and well logging data and matching the obtained geophysical results with lithological composition and mineral structure of rocks to assess gas prospects. The laboratory investigation on core samples included petrographic and petrophysical analysis of rocks. The effective porosity cutoff value for tight gas reservoirs of the studied area is 4,5 % under reservoir conditions and 4 % in the laboratory settings. 130 core samples were selected, for which the effective porosity is larger than the cutoff value. The histogram of effective porosity and absolute permeability distribution for tight gas intervals shows that PHI is in the range of 4–7 % and K – 0.01–2 mD (the largest number of samples has K – 0.01 mD). Conducted analysis of the micropetrographic study results of the core material showed that the matrix of the Moscowian stage rocks takes an average of 70 % from the volume, represented by 41-47 % quartz, 3 - 10.5 % – feldspar and 2.1–6 % – mica minerals. Cement is represented mainly by illite clay component (14–17.5 %) with calcite content (3–8.75 %). According to the formation evaluation of the well logging data clay volume, effective porosity and gas saturation were calculated for the well N10 Svyatogorska area. The intervals: 3836.4–3866.6 m and 4107.6–4140,4 4 m were indicated as tight gas reservoirs. The effective porosity of promising formations varies in the range - 4.5–9.5 %, and the gas saturation in 50–65 %. According to the results of well testing – 19.0 thousand m3/d flow rate of gas was obtained in the interval 4042–4150 m of the well N10 (before intensification). Summarizing the obtained results and comparing with the world oil and gas practices in the field of unconventional sources of hydrocarbons one suggests that the rocks of the Moscow strata of Svyatogorska Area are tight gas reservoirs.

Soil Minerals Serving as Source of Arsenic in Alluvial Aquifers of Holocene: A Case Study from Indus Delta, Sindh, Pakistan

Groundwater arsenic contamination is recently reported in the alluvial aquifers of Indus deltaic plain. Since the source of arsenic is believed to be natural as widely reported in other deltaic aquifers of same age (Holocene), it is imperative to evaluate the soil characteristics for identifying the sources of arsenic and its mobilization mechanism. For this purpose, 49 soil samples were collected from near aquifer sites in all three talukas of Tando Muhammad Khan district. Visual analysis revealed that soil is light grey in color with fine texture ranging from silt to silty-clay. The X-ray diffraction study reveals the occurrence of quartz, mica and clay minerals in all collected soil samples. Plagioclase feldspar is second dominant mineral group in the order of albite (calcian) >albite>albite (disordered) = anorthite > anorthite (sodian) = anorthite (disordered). Calcite is major carbonate mineral which is detected in 40 out of total 49 soil samples. The occurrence of other occasional minerals includes amesite, nitro-calcite, rutile and zinnwaldite. The frequency of micaceous minerals in collected samples is in the order of clinochlore> polylithionite> Biotite > phlogopite> muscovite. Polylithionite is found in about half of the total soil samples, where most of the aquifers contain arsenic >20 μg/L (Khan, 2014). Phlogopite is observed in seven soil samples which are also associated with clinochlore. On the other hand, biotite is found in 14 sediment samples collected from Tando Muhammad Khan and Bhulri Shah Karim talukas and muscovite occurs in three soil samples of Tando Muhammad Khan taluka. It can be concluded from present study that fine-grained Phyllosilicates have strong affinity for arsenic retention. These sediments are important source of arsenic Indus delta and other deltaic plains of the world.

Anisotropy of quartz mica schist based on quantitative extraction of fabric information

In this study, comprehensive laboratory experiments, such as thin-section and optical section analyses and P wave velocity and uniaxial compression tests, are performed on three types of quartz mica schist samples. The thin-section analysis reveals that the schist predominately consists of flaky mica and granular minerals, including quartz, feldspar, and calcite. The two types of minerals, both presenting a certain degree of orientation, are arranged to form a quasi-bedded structure as a whole, which essentially leads to macroscopic physicomechanic anisotropy. By means of optical section observation, directional microfissures are found to mainly be distributed alongside the edge of the oriented mica layer, while defects in other parts exhibit irregular orientation. Moreover, quantitative information is extracted from gray images by Image-Pro Plus (IPP), and then, relevant indicators are proposed to quantitatively analyze the differences in the content, morphology, and distribution characteristics of minerals and defects among the three types of samples. P wave velocity measurements of dry cylindrical specimens with different schistosity angles α show that the minimum value lies in the direction of the transverse schistosity planes (α = 90°) and that the P wave velocity increases with the decrease of the schistosity angle. There is an obvious linear positive correlation between the orientation coefficient of mica, which is adopted to indirectly reflect the orientation degree of microfissure, and the 0.5 power of the velocity anisotropy coefficient. The uniaxial compression test of specimens reveals the anisotropic characteristics of the peak strength, failure mode, and crack initiation and propagation for the schist samples. In particular, with the change of the schistosity angle, the peak strength and crack initiation strength have a U shape, characterized by a minimum value at α = 30° and maximum value at α = 0° or 90°. Directional microfissures and irregular defects with a dominant angle control the crack initiation of the specimens with 0° ≤ α ≤ 45° and 45° < α ≤ 90°, respectively. The weak edge of the directional mica layers has a more or less guiding effect on crack propagation when compressive loading is applied obliquely to the schistosity planes, while crack propagation is independent of weak edges when perpendicular to the planes. Three failure modes occur in the specimens with the change of the schistosity angle: tension-splitting failure, shear-slip failure, and shear failure. It is found that the mechanical anisotropy properties of the schist samples are closely associated with the content, morphology, and distribution characteristics of minerals and defects based on the analyses of the macro- and microquantitative data.

MINERALOGICAL PROPERTIES OF OAK FOREST SOILS IN IRAQI KURDISTAN REGION

This experiment was conducted from 1/7/2016 to 20/12/2018 to study the mineralogical properties of oak forest at 12 locations (Gara, Matin and Brifca) from Dohuk governorate, (Bilah, Malakan and Awagrd) from Hawler Governorate, (Bardanga, Badawan and Chwarta) from Sulaimani Governorate, and (Bakhakon, Hawar and Sartak) from Halabja governorate in Iraqi Kurdistan region. The samples collected from a depth of (0 – 60) cm for laboratory analysis. The study includes qualitative identification of clay minerals by X- ray diffraction data. Peak height was used as a rough indicator of relative abundance of minerals. In general, the expansion of 14°A to ≈ 17°A in ethylene glycol treatment was not detected because the measuring was started from 5θ (degree 5 theta) so the differentiation between Chlorite and Semectite was not done in this treatment. The main results indicated that the swelling chlorite being the dominant mineral in these soils. While the miner clay mineral in that locations were Kaolinite. Mica was identified in all location except of Bilah site, the dominant type of Mica was Muscovite which was obtained from 6 Locations, while Biotite obtained from 5 sites. It appears that Muscovite was recorded from 50% of Forest sites while Biotite recorded at 41.7% of Forest sites and Both Mica mineral type was not recorded from 8.3% of studied Forest soils.

Magmatic-hydrothermal evolution of rare metal pegmatites from the Mesoproterozoic Orange River pegmatite belt (Namaqualand, South Africa)

The 450 km long Orange River pegmatite belt intruded the Namaqua Sector of the Mesoproterozoic Namaqua-Natal Province, Southern Africa, at ca. 1 Ga. The western part of the belt is characterized by the occurrence of LCT pegmatites locally mineralized in Li, Ta, Nb, Be and Bi. Most of these mineralized pegmatites display zonation with a quartz-feldspar-muscovite-garnet-beryl-bearing aplite border and wall zone, a quartz-feldspar-spodumene-lepidolite-bearing intermediate zone, and a quartz-K-feldspar core. The pegmatites and their granodioritic country rocks commonly show evidence of albitization and greisenization (i.e. secondary muscovitization). In this study, detailed petrographic observations and the compositions of mica, feldspar, spodumene and Nb-Ta oxide minerals are reported. This information is combined with bulk country rock compositions and new U-Pb zircon and monazite ages plus Sm-Nd isotope compositions of monazite to constrain the origin and magmatic-hydrothermal evolution of weakly and strongly mineralized LCT pegmatites.The Li-Ta-Be Kokerboomrand I pegmatite emplaced at ca. 985 Ma during the main stage of pegmatite emplacement in the Orange River belt and regional strike-slip deformation. It has εNd(t)monazite = −14 ± 3 and potentially formed by partial melting of Paleoproterozoic rocks from the Richtersveld magmatic arc. Alternatively, Mesoproterozoic sediments of the Bushmanland Subprovince may also provide a suitable magma source for the Kokerboomrand I pegmatite.The rare metal contents of muscovite and columbite group minerals (CGM) increase from the weakly mineralized to strongly mineralized pegmatites, suggesting early-stage fractional crystallization or variable partial melting conditions. Mica Nb/Ta values of <14 and K/Rb ratios of <40 can be used as geochemical tools for Li-Ta-(Nb)-Be exploration in the region, and possibly in other pegmatite belts worldwide.Rare metal-bearing minerals crystallized throughout the magmatic-hydrothermal evolution of mineralized pegmatites. During the magmatic-dominated stage I, constitutional zone refining likely induced a decrease of spodumene Fe contents and increase of CGM Ta contents toward the pegmatite core. Stage II marks the pervasive circulation of an immiscible hydrosaline melt. This stage is characterized by the replacement of the primary mineral assemblage by lamellar albite (cleavelandite), (fluor)calciomicrolite and Cs-Ta-rich Li-muscovite and zinnwaldite. Stage III represents the progressive transition from a magmatic-hydrothermal system dominated by a Li-Cs-Ta-rich hydrosaline melt toward a system mainly involving (Li)-Cs-(Ta)-Bi-rich aqueous fluids. This stage is characterized by the crystallization of lepidolite and zero-valence-dominant pyrochlore as well as strong localized greisenization and Bi mineralization.Magmatic-hydrothermal alteration of the immediate country rock of the mineralized pegmatites is marked by the crystallization of albite, Li-Ta-Cs-rich mica, various Nb-Ta oxide minerals, and led to a strong decrease of the whole-rock Nb/Ta ratio plus significant rare metal enrichment.Our findings from the Orange River belt demonstrate that an important role can be ascribed to melt-melt and melt-fluid immiscibility and metasomatism in the formation of pegmatite-related rare metal deposits. Greisens and albitites associated with pegmatites and their immediate country rocks can be considered as favorable targets for Li-Ta mineral exploration. Strong and pervasive metasomatism across the mineralized pegmatites and their country rocks suggests involvement of a parental medium that was highly enriched in water.

The Role of pH, Temperature, and NH4+ during Mica Weathering

Phyllosilicates are abundant materials both on Earth and Mars, and the weathering of these minerals is an essential part of a wide variety of geochemical cycles. Alteration mainly takes place at the solution−mineral interface and needs to be fully understood in order to correctly model global water−rock interactions. To directly link the physicochemical solution properties to the dominant surface processes controlling phyllosilicate alteration, we used a custom-built hydrothermal atomic force microscope to study in situ the surface reactivity of biotite, phlogopite, and muscovite in contact with aqueous solutions for a broad range of temperatures and pH values. On the basis of our microscopic observations correlated with previously obtained macroscopic dissolution rates, we have constructed a tentative weathering diagram for mica minerals connecting the dominant surface mechanisms and bulk dissolution behavior to the physicochemical solution properties (pH, T, and speciation). The resulting diagram can be divided into two main areas: low-grade weathering occurring at low temperatures and mildly acidic to neutral pH and highgrade weathering taking place at high temperatures and low pH, separated by a transition zone. Each of these areas is characterized by a series of chemical and physical surface processes, which can be related directly or indirectly to incongruent and congruent bulk dissolution. The transition temperatures and pH values depend on the type of mica, with biotite being the most reactive one and muscovite the least reactive one. It is noteworthy that for close to neutral pH conditions the presence of NH4+ shifts the transitions from low- to high-grade weathering to a significantly lower temperature.

The effect of activating treatment on demineralization of a lignite sample by reverse flotation method

ABSTRACT In this study, the influence of activating treatment on the demineralization of a lignite sample utilizing the reverse flotation was studied. A lignite sample containing 42.09% ash, 0.86% sulfur, 38.46% volatile matter and 19.45% fixed carbon was used in experiments. Quartz, clay mineral, feldspar (plagioclase) mineral and mica mineral were determined as dominant minerals. The activation of gangue minerals (particularly quartz) using lead, tin, iron, and aluminum salts were performed. The influences of different parameters were investigated. Reverse flotation results demonstrated that a clean coal having 35.81% ash and 61.81% combustible yield could be gained in the usage of tin salt.

Geochemical characteristics of a pre-Middle Jurassic oceanic crust fragment from the Central Pontides in northern Turkey: Geodynamic implications on intra-oceanic subduction initiation

The Central Pontides (northern Turkey) is one of the key localities to understand the geodynamic evolution of the Palaeo- and Neotethyan oceans. It consists of the pre-Jurassic basement units, the Early Jurassic and the Early Cretaceous accretionary complexes, the widespread Middle Jurassic continental arc magmatics and the Late Jurassic to Tertiary cover units. The Early Cretaceous accretionary complex is represented by the Central Pontide Structural Complex and includes the Middle Jurassic oceanic units, which were metamorphosed during the Early Cretaceous. Apart from these oceanic units, a few metaophiolite and serpentinite fragments have been recognized within the basement units, which may represent the remnants of an older ocean. The pre-Middle Jurassic Devrekani Metaophiolite is the largest oceanic fragment and tectonically intercalated within/between the Devrekani Metamorphics and the Çangaldağ Metamorphic Complex. It is mainly composed of harzburgites, dunites with chromite veins and metagabbros, and cut by metabasaltic andesites and metadacites. Petrographically, the gabbro consists mainly of plagioclase and clinopyroxene, and displays phaneritic/porphyritic texture. In contrast, the metabasaltic andesite includes plagioclase and mica phenocrysts within a fine-grained groundmass. Also, the metadacite is composed predominantly of quartz, plagioclase, and mica minerals. Two different magmatic groups belonging to completely different tectono-magmatic settings have been geochemically determined based on the immobile trace element systematics. The metadacites and metabasaltic andesites are akin to continental arc magmatics and characterized by negative Nb and Ta anomalies and depleted HFSE relative to Th and La contents. However, the metagabbro samples display the geochemical signatures of boninitic rocks and characterized by highly depletion in HFSEs and REEs relative to N-MORB. The Devrekani Metaophiolite in the Central Pontides may represent another remnant of pre-Middle Jurassic oceanic crust generation and can be north-eastward continuation of the Permian-aged Almacık complex and the Boğazköy Metaophiolite fragment in the western Sakarya Composite Terrane. It may have been cut by intrusions of the extensive Middle Jurassic continental arc magmatism after its imbrication within the basement unit. The presence of pre-Middle Jurassic oceanic units may indicate that the Paleozoic ocean may have survived as the Jurassic Intra-Pontide Ocean between the Scythian Platform and Sakarya Composite Terrane during the Mesozoic time. Thus, the Intra-Pontide Suture may normally include the Palaeozoic and Mesozoic remnants of the long-lived northward subducting Tethyan ocean.

Controlling factors on the geochemistry of Al-Shuaiba and Al-Mejarma coastal lagoons, Red Sea, Saudi Arabia

Abstract Geochemical and mineralogical analyses of bottom sediments collected from Al-Shuaiba (SHL) and Al-Mejarma (MJL) coastal lagoons, Red Sea were carried out. Mineralogically, the sediments consist mainly of carbonate minerals particularly aragonite, high and low Mg-calcite and traces of dolomite admixed with non-carbonate minerals including quartz, k-feldspars, plagioclase and traces of amphiboles, mica and clay minerals. The spatial distribution of major and trace elements at the bottom of the lagoons indicates two groups of elements. The first, less significant, is of terrigenous origin concentrates mainly in the shoreward direction. This group includes the silicates (Al2O3-Fe2O3-SiO2), Feldspars (K2O-Rb-Ba) and heavy minerals (V-Cr-Zr, TiO2-Y-Nb) related elements. The second most dominant group is the carbonate related elements (CaO-Sr) that concentrates in the seaward direction. The two lagoons are not affected by urbanization or anthropogenic impact, and hence the siliciclastic elements are related to the terrigenous influx mainly by aeolian transportation. The carbonate related elements are mainly of biogenic origin related to calcareous skeletal remains. The elemental distribution in the bottom sediments of the MJL is more homogeneous than those in the SHL reflecting the bottom conditions that are mainly controlled by lagoon morphology, hydrodynamic and the water circulation between the lagoon and the sea. Geochemical data show no obvious enrichment of Al-normalized redox-sensitive trace elements V and Cr suggesting that there is no variation in the bottom redox conditions in contrast with other previous studies. The information in this work is an important tool for biogeochemical and biological research projects in the Red Sea coastal lagoons.

Modeling CO2 wettability behavior at the interface of brine/CO2/mineral: Application to CO2 geo-sequestration

Carbon capture and storage (CCS) has been introduced as an effective method for reduction of CO2 emissions to the atmosphere. While different aspects and controlling parameters of geological CO2 sequestration process are well understood, there is still large uncertainty regarding brine/CO2/rock wettability and no model has yet been presented for characterizing the contact angle of brine/CO2/rock system at different environmental conditions. In this study, various intelligent models have been developed for accurate estimation of brine/CO2/rock contact angles. Results demonstrated that the proposed models have the ability to accurately simulate the brine/CO2 wettability behavior for quartz, calcite, feldspar, and mica minerals at different pressures, temperatures and salinities. Additionally, results revealed that adaptive neuro-fuzzy interference system has the best performance compared with the other models and its superiority is shown through statistical and graphical analyses. Afterward, the most effective input parameters on brine/CO2/rock wettability were investigated by employing Monte-Carlo algorithm, which showed that mineral type, salinity and pressure are the most sensitive variables for this process. As wettability can highly affect the residual and structural trapping mechanisms during carbon geo-sequestration, presenting reliable models for estimating brine/CO2/rock wettability is crucial. Therefore, the outcomes of this study can be useful for accurate estimation of these mechanisms capacity.

Batch sorption experiments of cesium and strontium on crushed rock and biotite for the estimation of distribution coefficients on intact crystalline rock

The distribution coefficient (Kd) of radionuclides on bedrock is one of the key parameters used in the safety analysis of spent nuclear fuel repositories. Typically, distribution coefficients have been determined using crushed rock. However, recent studies have shown that crushing of the rock increases considerably the distribution coefficient compared with the values of intact rock. This study aimed to test if batch sorption experiments using different grain sizes (i.e. mean diameter of grains) can be used to evaluate the Kd of strontium (Sr) and cesium (Cs) on intact crystalline rock, which would decrease the needed experimental time compared with transport experiments. Here we report the results of the batch sorption experiments with crushed rocks and compare the results with those from a recent study performed using electromigration experiments with intact drill core samples (Puukko et al., 2018). The batch sorption experiments were done for rock samples from Olkiluoto, Finland, as a function of grain size and of Cs and Sr concentration. Furthermore, the specific surface areas of the same rock samples with different grain sizes were determined. It was shown that Cs distribution coefficients correlate with specific surface areas of the studied rocks and biotite, the correlation coefficient being 0.95. The Cs distribution coefficient was highest for biotite at about 0.1 m3/kg at 10−4 M cesium concentration and increased systematically to about 1 m3/kg at 10−8 M. Distribution coefficients for rocks were up to about two orders of magnitude lower, being lowest with the rock with the lowest biotite content (3.3%). The distribution coefficient of Sr varied from 0.04 m3/kg to 0.007 m3/kg and behaved in a different manner: it remained constant in two out of three studied rocks in the concentration range of 10−8-10−4 M and only in the case of one rock a decreasing trend was seen at the higher concentration range. It was also shown that batch sorption experiments overestimate the distribution coefficient in respect to intact rock. The decrease of the distribution coefficient as a function of grain size can be estimated using a power law function. It was also shown that estimation of distribution coefficients of Cs and Sr for intact rock by extrapolation of distribution coefficients determined for different grain sizes is not possible without increasing grain size, but in that case diffusion into the grains would also affect the results. A new method was developed for estimating the fraction of the inner surface area of the total surface area of crushed grains. For the mean grain sizes of 0.25 mm and 0.75 mm the fraction of the inner surface was found to be 35–70% and 60–90%, respectively. The inner specific surface area was highest with biotite at 1.2 m2/g and lowest with the rock with lowest biotite content (3.3%) at 0.07 m2/g. The surface area analysis revealed that crushing creates and/or allows access to additional inner surface area that is not measured in intact rock. Furthermore, it was demonstrated that sorption of Cs on crushed rock was dominated by mica minerals in multiple concentrations while the effect of mica minerals on the Kd of Sr was not as straightforward.

Applying heatmaps in interpretation of geochemical baseline data on urban soils in Finland

Urban soil geochemical mapping was carried out, using the same sampling and analytical protocol, in seven Finnish towns in 2012–2017. All samples were taken from urban topsoil (0–10 cm), dried at <40 °C and sieved to <2 mm grain size. Aqua regia-extractable concentrations of 24 elements and total carbon content were assessed in this statistical study. Soil geochemical results are a typical example of compositional data. Thus, the data were isometric log-ratio (ilr) transformed before correlation analyses and heatmap production. Heatmapping involves colour coding of correlations, with different colours for positive and negative correlations. Elements were re-arranged for heatmaps by clustering the correlation matrix, using hierarchical clustering with distances based on the correlations. Heatmaps were produced for four general soil classes derived from samples taken from the urban topsoil: natural fine-grained sediments, natural coarse-grained sediments, man-made minerogenic soil material and man-made soil material rich in organic matter. The heatmaps revealed two distinct groups in all urban soil parent materials: elements related to abundance of trioctahedral mica minerals and elements bound to soil organic matter. Some man-made soil materials reflecting a single source of pollutants were also identified in the heatmaps.

Mineralogical and major oxide characterization of Panyam clays, North - Central Nigeria

Clay minerals are form over long periods of time, through weathering as a result of gradual chemical breakdown of rocks rich in feldspar. The extent of weathering is determined by many factors. Most common constituent mineral of clays is often one of the members of the mica mineral group. They include illite, sericite, muscovite, and biotite. Others are kaolinite, smectite, mixed-layer clays and chlorite. This paper characterizes eight clay samples from Panyam, North-Central Nigeria. The characterization is based on their mineralogy and major oxide chemistry. This is aimed at determining the extent of weathering and/or maturity and origin or source of the clay materials. Compositional mineralogical and oxide analysis was performed using X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) respectively. The X-ray data revealed that the primary constituents of the rocks such as feldspars, biotite and other minerals have been altered to Illite and kaolinite. Nesbitt and Young weathering trend model was used for characterizing the samples using their major oxides; four samples classified as muscovite, two as kaolinite and two as illite. From the Nesbitt and Young model, it was discovered that all samples had a granitic origin with a slower rate of weathering. Key words: Panyam, clay characterization, smectite, kaolinite, oxides.

Phyllosilicates as protective habitats of filamentous cyanobacteria Leptolyngbya against ultraviolet radiation.

Phototrophic cyanobacteria are limited in growth locations by their need for visible light and must also cope with intermittent ultraviolet radiation (UVR), especially in extreme environments such as deserts and on early Earth. One survival method for cyanobacteria is growing endolithically within minerals such as micas, gypsum, and quartz minerals. However, the capability of different mica minerals to protect cyanobacteria from UVR, while at the same time allowing transmission of photosynthetically active radiation (PAR), has only been minimally examined. In this study, we performed laboratory incubation experiments to demonstrate that a model filamentous cyanobacterium, Leptolyngbya sp., can colonize micas, such as muscovite, phlogopite, and biotite. After inoculation experiments confirmed that these cyanobacteria grew between the sheets of mica, Leptolyngbya sp. colonies were exposed to UVB and UVC for up to 24 hrs, and the level of survival was determined using chlorophyll a and carotenoid assays. Of the three micas investigated, muscovite, being an Fe-poor and Al-rich mica, provided the least attenuation of UVR, however it transmitted the most visible light. Fe-rich biotite provided the best UVR shielding. Phlogopite, apparently because of its intermediate amount of Fe, showed the greatest ability to shield UVR while still transmitting an adequate amount of visible light, making it the ideal habitat for the cyanobacterium. Upon exposure to UVR, significant shifts in several important fatty acids of the cyanobacterium were detected such as linolenic acid and oleic acid, 18:3ω3 and 18:1ω9c, respectively. These cellular changes are interpreted to be a consequence of UVR and other accessory stress (such as O3).

Assessment of the impact of high temperature on the facing stone from hard rocks

Samples from two deposits of natural stone, which are located in Ukraine, were experimentally studied. Tests of granite samples were carried out at high temperatures of 300, 500, 700, 900 °C. All presented samples show the change in surface colour at a temperature of 300 °C and above. The behaviour of heated granites depends on their mineral composition, structure and texture. The surface of all the prototypes are lighter, some samples of granites have lost saturation of colors. When the samples were heated to 900 °C of natural stone, the largest growth of the component L (images of the samples of the stone brightens) of the CIELab colour system occurred in the samples of Buka gabbro by 44.4 %. The smallest growth of the component L occurs in the granodiorite by 28.6% when the samples are heated to 900 °C. In gray granites, redness appears when heated, which is mainly concentrated around mica and other minerals that are rich in Fe. The greatest change in colour was due to the transition phase of dark-coloured minerals (biotite and pyroxene) into polymorphic minerals. This gave the samples of granodiorites lighter colour because minerals change colour from black to gray or white. Shades of white were given by quartz, where white microcracks appeared when it was heated. Noticeable aesthetic damage to the surface of natural stone samples begins at temperatures from 300 to 500 °C. Thus, a fire with temperatures below this limit can be considered «safe» in terms of aesthetic damage, if we consider only the coefficient of heating of the fire and exclude ash and gases.

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.

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.

Occurrence of pyrites in sandstone-type uranium deposits: Relationships with uranium mineralization in the North Ordos Basin, China

Large quantities of pyrite have been discovered near the ore-bearing segments of the sandstone-type uranium deposits in the North Ordos Basin. In this study, the electron probe microanalysis, scanning electron microscopy, and isotope geochemical analysis were used to systematically investigate the morphology, composition, and S isotopes of the pyrites in these deposits, and their genetic order relative to the other main altered minerals. Based on the regional tectonic evolutionary sequence of the basin, the relationships between the pyrites and uranium mineralization are discussed. Macroscopically, the pyrites were found to occur in lumpy, banded, disseminated, star-like or sheet-like form. Microscopically, they exist either as detrital grains or inside detrital grains, as idiomorphic grains, in colloidal or framboidal form, inside mica minerals, in banded or petaloid form, and in other forms related to biological cells or microorganisms. The δ34S‰ values in the pyrites are highly variable (−7.3‰ to −37.2‰), but principally in the proximity of −30‰, and display obvious biogenic origin. Taking into consideration the extremely low U contents in the pyrites and achavalites (iron selenide), the genetic order of the main altered minerals is determined as follows: detrital pyrites > clay mineral overgrowths > micritic calcites during the diagenetic stage; and achavalites > pyrites > coffinite/pitchblende > vanadium oxides > sparry calcites during the metallogenic stage. The broad presence of pyrites in the Jurassic Yan'an Formation during the basin’s evolution provided detrital pyrites and organic detritus for the overlying formations. The Zhiluo Formation, host of the uranium mineralization, is also home to some primary spherical colloidal or framboidal pyrites. The Cretaceous was the main epigenetic uranium metallogenetic period as well as the main pyrite development period of the area. The pyrites, which are typically colloidal, have cemented the earlier framboidal pyrites and other minerals and are closely associated with the redox reaction related to uranium mineralization. In the Paleogene, uranium mineralization mainly occurred by the redox migration of early shallow deposits to, and fresh pyrites forming in deeper levels.