Individual Mineral Components Research Articles

Application of AFM on Identifying Mechanical Properties of Individual Minerals and Surface Properties of Crack with High Resolution in Shale

Improving the resolution and accuracy of the mechanical properties of organic-rich shale is very important. The results can reveal the mechanical properties of shale from micro scale and serve as a guide for the design of hydraulic fracture optimization parameters. This study introduced an advanced technique to obtain the mechanical properties of shale with high resolution (58.6 nm/pixel) by combining SEM, EDS, and Atomic Force Microscopy (AFM). To locate the target area in SEM and AFM accurately, a positioning technique that uses special distributions of pyrite was established. AFM PeakForce QNM mode was selected due to its advantages at capturing topography and mechanical properties in material. Results illustrated the ability of AFM to obtain the mechanical properties (modulus) of individual mineral components in shale, the detailed topography of crack, and mechanical properties of minerals in a specific area. In particular, the mechanical properties of minerals around crack explained the layered distribution of minerals around the fractures, and the cracks developed in the clay mineral layer was detected. This article demonstrates the great potential application of AFM in shale.

Thermal emission measurements of ordinary chondrite mineral analogs in a simulated asteroid environment: 2. Representative mineral mixtures

We investigate a suite of synthetic mineral mixtures designed to act as bulk mineralogical analogs to H, L, and LL ordinary chondrite meteorites in order to probe how the thermal emission characteristics of such materials change between ambient and simulated asteroid environmental conditions. Due to the parent body link with certain S-type asteroids, studying these analog mixtures in an environment that is relevant to actual asteroid surfaces advances our understanding of the thermal emission properties of one of the most common regolith types among the main-belt and near-Earth asteroid populations. The observed changes in spectral emissivity features due to cold, vacuum conditions are not as large as previously observed for single mineral (silicate) samples. We interpret this difference to be the result of metallic and opaque components weakening near-surface thermal gradients in the mixtures. As such, we predict that near-surface thermal gradients on ordinary chondrite parent bodies (e.g., S-type asteroids) are likely much weaker than would be inferred from cold, vacuum measurements of individual mineral components. We tested whether the increased spectral contrast observed in fine-grained (<25 μm) samples measured in a cold, vacuum environment increases the efficacy of least squares linear unmixing methods. It is found that the accuracy of such models does not improve relative to measurements made under ambient conditions, thus linear unmixing models are not expected to yield accurate estimates of the modal mineralogy of airless planetary surfaces if they are dominated by fine-grained regolith. Mixtures with coarse particle sizes (125–250 μm) that were modeled using the coarse particle size endmembers yielded results that were largely independent of the environmental conditions, but with larger errors in spectral fits for samples measured in a simulated asteroid environment. At simulated asteroid environmental conditions, the bulk silicate composition and metal content play a more important role in determining the thermal state and brightness temperature of the sample than at ambient conditions. Modest changes in metal content (10–25 wt%) lead to large differences in the brightness temperature of a sample. Under simulated asteroid conditions, an ~10 K increase in maximum brightness temperature that tracks with increased iron content is observed at fine particle sizes (<25 μm) between each of the analog ordinary chondrite groups. Based on these results, it may be difficult to distinguish H, L, and LL compositions of suspected ordinary chondrite parent bodies using only Earth- or space-based thermal emission spectra. This is inferred from the spectral similarity of the analog mixtures and the absence of significant variation in spectral emissivity associated with reported differences in bulk metal content for ordinary chondrites.

Mechanical characteristics and factors controlling brittleness of organic-rich continental shales

Brittleness is an essential parameter in the evaluation of wellbore stability and hydraulic fracturing design of shale reservoirs. It is an inherent geomechanical property controlled by the mineral composition, sedimentary structure, and geological condition. However, traditional brittleness evaluation methods based on the elastic parameters and mineral composition analyses are limited by the anisotropic petrophysical behaviors of continental organic-rich shale. In this paper, we analyzed the contributing mechanical properties of individual mineral components and organic contents of shale using laboratory stress experiments. Based on the principle of energy conservation and post-peak deformation, we evaluated the brittleness and analyzed the main factors influencing shale brittleness. In addition, we established a new method of quantifying the representative shale Brittle-Ductile Index (BDI) via combined consideration of its organic matter content, mineral composition, and mechanics characteristics. The results identified quartz and feldspar as the main brittle minerals with a substantial contribution to shale brittleness. Conversely, the organic matter and carbonate minerals have little effects on the pre-peak elastic parameters but are very sensitive to the post-peak rupture parameters and significantly influence the brittle shale fractures. Specifically, the calculated BDI is high in areas of rich in organic matter or developments of shale lamination. This usually leads to brittle fracturing along the weak surfaces when the stress is mainly applied in the bedding directions. In contrast, the BDI is small in carbonate rich shales as mineral particles are heavily compacted which disperses the stress, resulting in scattered ductile fractures.

Pore structure characterization for organic-rich Lower Silurian shale in the Upper Yangtze Platform, South China: A possible mechanism for pore development

The Lower Silurian shale in the Upper Yangtze Platform has become one of the main targets of the exploration and development of marine shale gas in South China. This study is focused on the organic-rich Lower Silurian black shale from four wells in the Upper Yangtze Platform, and their organic geochemistry, petrology, porosity and pore characterization were investigated. A combination of field emission scanning electron microscopy (FE-SEM), low pressure N2/CO2 adsorption and mercury intrusion porosimetry (MIP) measurements was conducted to characterize the pore structure and the effects of organic matter and inorganic minerals on porosity were discussed. Then the contribution of individual mineral components to total porosity was analyzed quantitatively. The results indicate that (1) FE-SEM images show that there are mainly three types of pores in the Lower Silurian shale: OM pores, pores of framework minerals, and pores in clay minerals. (2) CO2 adsorption results suggest that the micropores of the shale samples are mainly contributed by the pores with width between 0.4 and 0.7 nm, while N2 adsorption results show that the mesopores of the shale samples are mainly contributed by the pores with width between 2 and 10 nm, which is consistent with MIP results. (3) The TOC content shows a weakly positive correlation with porosity, suggesting that organic matter has an important influence on shale porosity, but it is not the most essential factor. When the maturity is lower than 2.6%, the porosity increases with increasing maturity, and when the maturity value is greater than 2.6%, the porosity decreases gradually. (4) The presence of rigid grains led to the formation of rigid frameworks, which can prevent pores from collapsing and benefit the preservation of OM pores and pores in clay minerals. Pores of framework minerals are mainly generated by the corrosion effect of organic acids produced in the process of hydrocarbon generation. (5) Organic matter has the largest pore volume per unit mass, followed by clay minerals, and then framework minerals. This means that organic matter and clay minerals contribute significantly to shale pore space given the same mass percentage condition; the matrix pores are mainly composed of pores in clay minerals and OM pores, which account for approximately 90% of the matrix pores.

Hot-spot heat generation in coal–shale deposits

Some consequences of a known but insufficiently studied phenomenon, local heat generation in solid caustobioliths under near-surface conditions, when temperatures can be sufficient for the pyrolysis of organic matter (OM), the heating of underground waters, and even the melting of individual mineral components, were considered. A specific structural-deformation geofiltration medium (with the sections of thermally changed rocks and polygenetic breccias) is formed in the sections of the heating and burning (complete or partial) of caustobioliths, thermal conversion, and the deformations of host rock deposits. It was noted that increased permeability appears in not only thermally converted (pyrometamorphic) but also unchanged deposits (due to sagging, splitting, caving, and associated explosive degassing). The concepts of the possibility of these bodies to contain hydrocarbon components (of different genesis) at different depths. The results obtained can be useful in the forecast of the anthropogenic destabilization of the interior of the Earth due to waste storage and burial and the underground gasification of solid caustobioliths and in the studies of shale hydrocarbons.

Establishing the Relationship Between Mineral Content and Palatability Attributes of Ribeye Steaks from Savannah-Fed Brahman-Influenced Cattle

ObjectivesCombination of eating qualities of beef plays an important role in beef consumer satisfaction; however, it is not well-understood how those eating attributes could be influenced by individual mineral components. The objective of this study was to examine the multivariate relationships between mineral profile and palatability attributes determined by consumers of Venezuelan Brahman-influenced cattle (Brahman).Materials and MethodsSteers and bulls (n = 33) of Brahman cattle were raised under similar extensive and feeding conditions (native grass pasture) and slaughtered at 19 and 24 mo of age (MOA). Ribeye steaks (2.54-cm thick) were removed from the longissimus thoracis muscle (posterior end) from the right side of each carcass at 48 h post-mortem. All samples were vacuum-packaged and immediately frozen at -30°C for Warner-Bratzler shear force (WBSF), mineral content (ash, Na, K, Mg, P, Ca, Cu, Mn, Zn, Fe; mg/100 g fresh tissue) and consumer sensory evaluation (n = 137; 9-point hedonic scale for overall, flavor liking, flavor intensity and tenderness liking). Principal component analysis was performed to identify the influence of the measured attributes.ResultsCorrelations coefficients did not reveal strong relationship among the variables measured. The total variance was distributed into 15 principal components (PC). The factor analysis showed that the first five PC with eigenvalues greater than 1 explained 67.24% of the standardized variance; PC1 explained 21.28%, PC2 16.82%, PC3 12.88%, PC4 8.68%, and PC5 7.59% of the total variance. The set of variables for the first PC included mineral components mainly Na, K, Mg, Ca, Cu, Mn, and Fe (based on the largest loading values). Next, PC2 was related to overall liking, tenderness liking, flavor liking, Ca and Zn. Principal component 3 had a large loading for ash, Na, P, Mn, WBSF, and flavor intensity. The fourth PC had ash and Fe; while PC5 K, Ca, WBSF and tenderness liking, flavor liking, and flavor intensity. Results obtained after plotting the first two PC showed segregation of ribeye steaks from animals slaughtered at 19 MOA and 24MOA (regardless of sex classes); younger animals tended to have more Ca, P, Fe, Mn, Mg, Cu, and less Na and K; and their samples had more desirables scores in overall liking, tenderness liking, flavor liking than older ones. In the second plotting (PC1 × PC3), WBSF and P were located in the positive side of PC1 along with 19MOA Brahman steaks; while ash, Zn, Na, and K on the PC1 negative side along with 24MOA Brahman steaks and closely associated with flavor intensity. Further results plotting (PC1 × PC4; PC1 × PC5) reaffirmed and showed a closely association between minerals and treatments previously mentioned.ConclusionThese results indicate sensory attributes are weak to moderate influenced by individual mineral content in beef. Content of individual minerals can affect the degree of liking more than overall ash content. Additionally, Ca, P, Fe, Mn, Mg, Cu content were positively associated to overall liking, tenderness liking, and flavor liking; in contrast ash, Zn, Na, and K were negative associated to such sensory attributes; but not to flavor intensity.

Pore structure characteristics of lower Silurian shales in the southern Sichuan Basin, China: Insights to pore development and gas storage mechanism

Silurian shale in Sichuan Basin is currently the most important target zone for shale gas exploration and development in China. Pore structure characteristics of Lower Silurian Longmaxi shales from southern Sichuan Basin were investigated. The combination of field emission scanning electron microscope (FE–SEM) and argon ion beam milling was utilized to describe the nanometer-to micrometer-scale (>1.2nm) pore systems. The shales were characterized by organic geochemical and mineralogical analyses. Total porosity, pore size distribution (PSD), specific surface area, and gas content were determined. Controls of organic matter richness, thermal maturity, and mineralogy on porosity were examined. The contribution of individual mineral components to total porosity was analyzed quantitatively. Total gas contents of the shales determined from canister desorption data were compared with theoretical (sorptive and volumetric) gas storage capacities.The total organic carbon (TOC) content of the shale samples ranges between 0.1 and 8.0 wt.% and helium porosity varies between 0.7 and 5.7%. Maturity in terms of equivalent vitrinite reflectance of bitumen (Reqv) ranges from 1.8 to 3.2%. TOC content is a strong control for the pore system of these shales, and shows a positive correlation with porosity. Porosity increases with increasing thermal maturity when Reqv is less than 2.5%, but decreases for higher thermal maturity samples. FE–SEM reveals four pore types related to the rock matrix that are classified as follows: organic matter (OM)–hosted pores, pores in clay minerals, pores of framework minerals, and intragranular pores in microfossils. Pores in clay minerals are always associated with the framework of clay flakes, and develop around rigid mineral grains because the pressure shadows of mineral grains prevent pores from collapsing. Pores of framework minerals are probably related to dissolution by acidic fluids, and the dissolution–related pores promote porosity of shales. A unimodal PSD exists in the micropore range of TOC–rich samples, while the PSD of carbonate–rich samples are bimodal. A PSD maximum in the micropore range is attributed by OM and another maximum in the range of mesopore–macropores is probably caused by the dissolution of carbonate minerals. Quantitative evaluation of the contribution of individual mineral components to porosity shows that the organic matter contributes approximately 62% to the total porosity. Framework minerals (quartz, feldspar, and carbonates, et al.) and clay minerals contribute 25% and 13%, respectively. The total gas content of these shales ranges from 0.4 to 6.2m3/t, and the total gas contents of selected samples determined from canister desorption tests agree with the theoretically estimated original gas-in-place (OGIP). OM-hosted pores are the main space for gas storage, and accounted for about 78% (55% adsorbed gas plus 23% free gas) of the OGIP, while pores in the inorganic matter accommodate 22% free gas of the OGIP.

Molecular architecture requirements for polymer-grafted lignin superplasticizers.

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement.

Biological Mineral Range Effects on Biomass Conversion to Aromatic Hydrocarbons via Catalytic Fast Pyrolysis over HZSM-5

A set of 20 biomass samples, comprising 10 genotypes of switchgrass, sorghum, and miscanthus grown in two different soils with high and low poultry manure input conditions and having a wide biological range of mineral content, were subjected to catalytic fast pyrolysis (CFP) over HZMS-5 using pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). The resulting products, including benzene, toluene, ethylbenzene, and xylenes (BTEX), naphthalenes, and gases, including carbon oxides, methane, and olefins, were quantified in terms of product carbon yield and chemical selectivity. The effects of the total ash content as well as the individual mineral components were compared to evaluate the effect of the natural range of these components on the product distribution. While there was considerable variation in the data because of the biological influence, a positive correlation was found between ash content and carbon conversion to aromatic hydrocarbons, which was particularly strong when considering only the switchgrass samples. This large degree of variation may be characteristic only of this sample set. Among individual mineral elements in the biomass, potassium, an essential mineral for plant growth, was found to have a strong negative influence on the carbon conversion to aromatic hydrocarbons, but iron was found to have a positive influence on the conversion to aromatics. Correlations between mineral content, the chemical intermediates from the incipient pyrolysis process, and the final CFP products suggest that the main influence of potassium is on the initial pyrolysis reactions, while iron may affect the catalytic reactions over HZSM-5.

Automated Mineralogical Analysis of PM10: New Parameters for Assessing PM Toxicity

This work provides the first automated mineralogical/phase assessment of urban airborne PM10 and a new method for determining particle surface mineralogy (PSM), which is a major control on PM toxicity in the lung. PM10 was analyzed on a TEOM filter (Aug.-Sept. 2006 collection) from the London Air Quality Network Bexley, East London, U.K. A cross-section of the filter was analyzed using a QEMSCAN automated mineralogical analysis system which provided 381,981 points of analysis for 14,525 particles over a period of 9 h 54 min. The method had a detection limit for individual mineral components of 0.05 ppm (by area). Particle shape and mineralogical characteristics were determined for particles in the size ranges PM(10-4), PM(4-2.5), and PM(2.5-0.8). The PM(2.5-0.8) fraction contained 2 orders of magnitude more mineral particles than the PM(10-4) and PM(4-2.5) fractions, however the PM(10-4) fraction forms 94% and 79% of the mineral mass and surface area, respectively. PSM of the PM10 was dominated by gypsum (36%), plagioclase (16%), Na sulphates (8%), and Fe-S-O phases (8%) in the PM(10-2.5), which may be important in explaining the toxicity of the coarse fraction. The wider implications of the study are discussed.

Experimental Study on the Effects of Chemical and Mineral Components on the Attrition Characteristics of Coal Ashes for Fluidized Bed Boilers

In this paper, the attrition characteristics of ashes of 25 different coals used in circulating fluidized bed boilers were experimentally studied. The attrition characteristics were described by the attrition rate constant Kaf, which was obtained by the static combustion and cold sieving method. The effects of 10 chemical components and 6 mineral components on Kaf were evaluated by the gray relational analysis method. The main phases of the mineral components in the coal ashes were determined by X-ray diffraction, and anhydrite (CaSO4), lime (CaO), quartz (SiO2), hematite (Fe2O3), metakaolinite (Al2Si2O7), and metaillite (KAl2AlSi3O11) were identified. The results showed that, for a given mass fraction, the significance of the influence of the ash chemical components on Kaf follows the sequence: CaO > MgO > SO3 >P 2O5 >N a2 O>F e2O3 >K 2O > TiO2 >A l2O3 > SiO2. The significance of the influence of the ash mineral components on Kaf follows the sequence: lime (CaO) > anhydrite (CaSO4) > hematite (Fe2O3) > metaillite (KAl2AlSi3O11) > metakaolinite (Al2Si2O7) > quartz (SiO2). In addition, the effect of the hardness of individual mineral components on Kaf was also discussed.

Micro-Attenuated Total Reflection Spectral Imaging in Archaeology: Application to Maya Paint and Plaster Wall Decorations

Fourier transform infrared (FT-IR) attenuated total reflection (ATR) imaging has been successfully used to identify individual mineral components of ancient Maya paint. The high spatial resolution of a micro FT-IR-ATR system in combination with a focal plane array detector has allowed individual particles in the paint to be resolved and identified from their spectra. This system has been used in combination with micro-Raman spectroscopy to characterize the paint, which was found to be a mixture of hematite and silicate particles with minor amounts of calcite, carbon, and magnetite particles in a sub-micrometer hematite and calcite matrix. The underlying stucco was also investigated and found to be a combination of calcite with fine carbon particles, making a dark sub-ground for the paint.

Natural and simulated hypervelocity impacts into solar cells.

The solar array which was returned to Earth from the Hubble Space Telescope (HST) in 1993, after 3.62 years of space exposure in low Earth orbit (LEO), has offered the opportunity to document populations of natural micrometeoroids and artificial “space debris”. Residues from the hypervelocity impact (HVI) of material deposited in 25 individual solar cells from the array have been investigated herein by scanning electron microscopy. The observations have been compared with the results of simulated HVIs into solar cells using known meteorite mineralogies. This has permitted assessment of the probability of retention for residue materials derived from HVI by well-characterised mineral species. The simulation experiments have thus far suggested that some of the textural features observed in impact residues are dependent on the nature of the individual mineral components within the original impactor. Furthermore it transpires that compounds containing volatile elements, such as Ca (from calcium carbonate), can be preserved as near-intact fragments explosively emplaced in an impact crater. Such unusual particles should not always be dismissed as simply contamination products if observed in LEO-derived HVIs.

Improved Petrological Modal Analyses from X-Ray Powder Diffraction Data by Use of the Rietveld Method. Part II. Selected Sedimentary Rocks

ABSTRACT Mineral modes have been determined for specimens of five sedimentary rocks (arenite, graywacke, slate, mudstone, and shale) from Cu K X-ray powder diffraction data using the Rietveld method. Up to eight individual mineral components were measured in each sample, with a detection limit of about 0.5 wt %, depending on the mineral assemblage. The X-ray results, when expressed as reduced oxides (wt %), are in reasonable agreement with XRF oxide compositions. The power of the Rietveld method in this application to mineral mode determination is its ability to (1) cope with complex diffraction patterns containing substantial peak overlap, (2) provide modes that do not generally require independent, lengthy calibration, (3) determine the chemical composition of the major phases during the analysis (thereby providing a degree of self-calibration), and (4) deal with very fine-grained samples. Disadvantages include (1) the need to know the identity of all the components beforehand, and (2) the need for experience in X-ray diffraction analysis by the Rietveld method.

Heavy metal uptake by zeoliferous rocks from Metaxades, Thrace, Greece: An exploratory study

The uptake of mercury, cadmium and silver from aqueous solutions by unpretreated and NaCl-pretreated clinoptilolite-bearing volcaniclastic rocks from Metaxades (Thrace, Greece) has been studied using a batch method with radioactive tracers (197Hg,115Cd and110mAg). The concentration of the solutions used varied between approximately 1000 and 17000 ppm. An improvement of the uptake ability was observed in the case of NaCl-pretreated material for all the investigated metals and especially for mercury at the upper part of the concentration range studied. The heavy metal uptake is attributed to different mechanisms taking place both at the rock grains and their individual mineral components.

Mineralogy from Geochemical Well Logging

AbstractMultivariate statistical analyses of geochemical, mineralogical, and cation-exchange capacity (CEC) data from a Venezuelan oil well were used to construct a model which relates elemental concentrations to mineral abundances. An r-mode factor analysis showed that most of the variance could be accounted for by four independent factors and that these factors were related to individual mineral components: kaolinite, illite, K-feldspar, and heavy minerals. Concentrations of Al, Fe, and K in core samples were used to estimate the abundances of kaolinite, illite, K-feldspar, and, by subtraction from unity, quartz. Concentrations of these elements were also measured remotely in the well by geochemical logging tools and were used to estimate these mineral abundances on a continuous basis as a function of depth. The CEC was estimated from a linear combination of the derived kaolinite and illite abundances. The formation's thermal neutron capture cross section estimated from the log-derived mineralogy and a porosity log agreed well with the measured data. Concentrations of V, among other trace elements, were modeled as linear combinations of the clay mineral abundances. The measured core V agreed with the derived values in shales and water-bearing sands, but exceeded the clay-derived values in samples containing heavy oil. The excess V was used to estimate the V content and API Gravity of the oil. The log-derived clay mineralogy was used to help distinguish nonmarine from transitional depositional environments. Kaolinite was the dominant clay in nonmarine deposits, whereas transitional sediments contained more illite.

Mineralogical Analysis of Suspended Cohesive Sediment Using an Analytical Electron Microscope

ABSTRACT Transmission electron microscopy coupled with energy dispersive analysis of X-rays facilitates determination of chemical composition of both bulk sample and individual mineral components in fine sediment. The information is used to estimate mineralogical composition of the sediment independently of mineralogical analysis by powder X-ray diffractometry.