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Quantitative Mineralogical Analysis Using the Rietveld Full-Pattern Fitting Method
Abstract
Quantitative phase analysis of a number of multicomponent standard and natural mineral mixtures has been done using an adaptation of the Rietveld method. Quantitative information was extracted from refined individual scale factors and unit-cell volumes (derived from refined unit-cell parameters), obtained with a Rietveld refinement program modified to analyze up to ten phases. The quantitative results for standard mixtures were within 2.5% (absolute) of the true values, with the exception of the hematite, ilmenite, and magnetite mixtures. Quantitative mineralogical analysis by the Rietveld method has several significant advantages over conventional methods of quantitative analysis. The method should find a wide application in geology, including in modal analysis and compositional determinations of individual mineral components using unit-cell parameter systematics. -from Authors
... The contained minerals were found with the aid of the DIFFRAC plus EVA 12 ® software (Bruker-AXS, Gmbtl, Karlsruhe, Germany) based on the ICDD Powder Diffraction File of PDF-2 2006. Furthermore, their modal mineralogy was also semi-quantitatively calculated through the Rietveld method according to Bish and Post [65]. The microtopography of the diabases was identified by using secondary electron images (SEI) (BS 812 Part 1 [66]), outlining seven qualitative categories, namely, granular, smooth, rough, honeycomb, crystalline, glassy and porous, with the aid of a JEOL JSM-6300 SEM equipped with energy dispersive and wavelength dispersive spectrometers and INCA software. ...
... Table 2. Mineralogical compositions of representative diabasic samples (-: not detected). The quantification errors calculated for each phase according to Bish and Post [65] were estimated to bẽ 1%. Abbreviations: cpx-clinopyroxene, qz-quartz, plg-plagioclase, Kfs-K-feldspar, bi-biotite, ttn-titanite, ilm-ilmenite, mgt-magnetite, ap-apatite, ser-sericite, chl-chlorite, act-actinolite, ep-epidote, prh-prehnite, grt-garnet. ...
... Mineralogical compositions of representative diabasic samples (-: not detected). The quantification errors calculated for each phase according to Bish and Post[65] were estimated to be ~1%. ...
This article presents, for the first time, the study of diabases from various ophiolite complexes from Greece and Cyprus to identify their performance as concrete aggregates. Within this scope, in the first step, diabase samples from four selected ophiolite complexes of Greece (Veria-Naousa, Edessa and Guevgueli) and Cyprus (Troodos) were collected in order to estimate their suitability as concrete aggregates by means of their petrographic and physicochemical characteristics. In the next step, concrete specimens were prepared and their mechanical strength was measured in order to investigate their mechanical performance. Additionally, their petrographic characteristics in relation to the mechanical strength of the created concretes were investigated for the first time. Concrete specimens prepared by employing diabases from the Veria-Naousa and Guevgueli complexes as aggregates were reckoned as the most durable ones in contrast to those derived from the Edesssa complex and even more so than those from Cyprus, with the latter containing the most altered diabases (rodingitised). The overall conclusion of this research is that the engineering properties of the aggregates were dependent on their petrographic characteristics and hence they influenced the final mechanical behaviour of each produced concrete.
... Crushed bulk rock samples were scanned through a range of 5 to 60 • 2θ at a scanning speed of 1 • per minute with a step of 0.02 • . Quantitative mineralogical analyses of the whole rock data were performed by Rietveld analysis [27] using PDXL and Siroquant 3.0 software [28]. ...
... The main mineral components are quartz grains buried in dolomite and anhydrite cement ( Figure 6). The highest concentration of quartz is observed in the lower part, where it reaches 75-80 (samples D3/ [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The rock consists of only two minerals: well-rounded quartz grains and anhydrite poikilitic cement ( Figure 6; sample D3/38). ...
Predominantly fine-grained strata deposited on the East Siberia craton are considered to mainly consist of Neoproterozoic sandstones. Clastic rocks near the unconformity border of the Edia-caran and Riphean are represented by sandstone and siltstone layers with thicknesses of several tens of metres belong to the Nepa, Tira and Byuk horizons in the Nepa-Botuoba region. These Neoproterozoic sandstones have features characteristic of aeolianites formed under the action of high wind velocity in Ediacaran time. Sandstone samples near the Riphean-Ediacaran boundary were collected from 5 deep wells and characterized for granulometry and mineral composition using optical microscopy, XRD, SEM and ICP-MS techniques. These sandstones have a high pro-portion of quartz (60-98%) with minor amounts of feldspars, carbonate and sulfate cements. Thin sections of the sandy rocks feature bimodal distributions of the grains throughout many sections with large well-rounded quartz grains being several orders of magnitude greater than the silt matrix grains. The monomineralic quartz rocks have quartz grains overgrowth. These rocks can be petroleum reservoirs with good porosity and permeability but, in most of the studied inter-val, a high content of anhydrite and dolomite interstitial cement significantly reduces both. The porosity of the rocks is low, while the permeability is very low, which may be associated with a significant content of clay and cement material. The fact that aeolianites normally contain large amounts of bimodal quartz (due to its high stability and resistance to weathering) and the pres-ence of heavy minerals.
... Crushed bulk rock samples were scanned through a range of 5 to 60 • 2θ at a scanning speed of 1 • per minute with a step of 0.02 • . Quantitative mineralogical analyses of the whole rock data were performed by Rietveld analysis [27] using PDXL and Siroquant 3.0 software [28]. ...
... The main mineral components are quartz grains buried in dolomite and anhydrite cement ( Figure 6). The highest concentration of quartz is observed in the lower part, where it reaches 75-80 (samples D3/ [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The rock consists of only two minerals: well-rounded quartz grains and anhydrite poikilitic cement ( Figure 6; sample D3/38). ...
Fine-grained strata deposited on the Eastern Siberian craton are predominantly considered to mainly consist of Neoproterozoic sandstones. Clastic rocks near the unconformity border of the Ediacaran and the Riphean are represented by sandstone and siltstone layers with thicknesses of several tens of meters, belonging to the Nepa, Tira, and Byuk horizons in the Nepa–Botuoba region. These Neoproterozoic sandstones have features characteristic of aeolianites formed under the action of high wind velocity in the Ediacaran period. Sandstone samples near the Riphean–Ediacaran boundary were collected from five deep wells and characterized for granulometry and mineral composition using optical microscopy, XRD, SEM, and ICP-MS techniques. These sandstones have a high proportion of quartz (60–98%) with minor amounts of feldspars, carbonate, and sulfate cements. Thin sections of the sandy rocks feature bimodal distributions of the grains throughout many sections, with large well-rounded quartz grains being several orders of magnitude greater than the silt matrix grains. The monomineralic quartz rocks have an overgrowth of quartz grains. These rocks can be petroleum reservoirs with good porosity and permeability, but in most of the studied intervals, a high content of anhydrite and dolomite interstitial cement significantly reduces both. The porosity of the rocks is low, while the permeability is very low, which may be associated with a significant amount of clay and cement material. Aeolianites normally contain large amounts of bimodal quartz (due to its high stability and resistance to weathering) and possess the presence of heavy minerals.
... 1:1 modulated clay minerals with their 0.7 nm basal spacing are represented by the kaolin and serpentine group. Kaolinite is the most abundant mineral species described in the inventory, occurring in 384 studies (Bish and Post, 1993;Arzola et al., 2003;Alves and Omotoso, 2009;Geramian et al., 2018). This is in contrast to its polymorphs, dickite and nacrite, which were quantified in just a selection of studies (Philippo et al., 1997;Martín-Martín et al., 2007). ...
... The most common XRD method used is that of Rietveld analysis with almost half of all studies employing this technique (303 out of 639; Table 2). Studies employing Rietveld analysis for clay mineral quantification have been extensively used over the past 30 years following pioneering studies by Bish and Post (1993) and Taylor and Matulis (1994). Today, a broad range of commercial and non-commercial software programs are available for use, the most common of which are based on the BGMN code of Bergmann et al. (1998), such as Autoquan and Profex (Doebelin and Kleeberg, 2015). ...
Much work has been undertaken quantifying the abundance of phyllosilicate clay minerals in soils, sediments and rocks of Earth's crust. However, no detailed global compilation of these minerals has yet been presented. Such information has implications for understanding the interactions between weathering, soil formation, plate tectonics, climate change, diagenesis, low-temperature metamorphism and hydrothermal alteration. It is also central to understanding the distribution of bound (crystalline) and adsorbed water in upper crustal environments. This database presents the first clay mineral inventory based on mineral quantifications of 21 lithological units representing the brittle continental and oceanic crust characterised by varying degrees of water-rock interaction at temperatures between ∼ −25 and +350 °C. Published mineral abundances for >24,000 samples, determined largely by the Rietveld X-ray diffraction-based technique, indicates 21.5 weight% (wt%) of the brittle crust is composed of clay minerals: 12.9 wt% located in the upper (< 12 km) continental crust and 8.6 wt% in the thinner oceanic crust down to average depths of 6.57 km. In terms of clay mineral types, the 2:1 clay minerals with little or no expandability (commonly illite) are most abundant in Earth's upper crustal environments and total 7.7 wt%. The remaining 13.8 wt% is distributed more equally between the 1:1 kaolin-serpentine minerals (5.7 wt%), the highly expandable 2:1 smectites (3.0 wt%) and the 2:1:1 chlorites (5.1 wt%). Whereas continental soils and the underlying regolith represent only a small part of the clay mineral inventory (just 0.02 wt%), they do constitute important generating zones. These minerals and other products of surface weathering are redistributed to the main depositional sink located in sedimentary basins where 8.2 wt% of hydrous phyllosilicates reside and are modified during diagenesis or hydrothermal activity. A further 1.0 wt% are redistributed as oceanic sediment. The remaining 4.7 wt% of clay minerals in the continental crust are found in the altered igneous and crystalline rocks. Although less well quantified, the altered basalts, gabbros and ultramafic rocks of the oceanic crust, together with the overlying oceanic sediments, represent a significant part of the inventory characterised by notably high amounts of smectite, chlorite and serpentine minerals. The total amount of stored water (adsorbed and crystalline water) held in the inventory is equivalent in volume to 22% of today's surface water with approximately half located in altered oceanic crust. The trapping and release of surface water in and from the clay mineral sink likely influenced both interior crustal processes and climate change throughout Earth's history. On a shorter time scale, clay minerals aid climate stability by influencing atmospheric CO2 concentrations and the carbon cycle.
... Finally, X-ray diffraction (XRD) analysis through a PANalytical® diffractometer X´Pert Pro model was conducted. Both the mineral and the amorphous phases were quantitatively determined relying on the Rietveld method [14][15][16], using the software PANalytical X'Pert HighScore Plus. The refines variables were: scale factor, specimen displacement, preferential orientation with spherical harmonics, unit cell parameters and profile variables, using Finger, Cox, Jephcoat asymmetry type. ...
A selection of fifty-one artificial aggregates, manufactured with different proportions of kaolinite, an iron phase (Fe 0 , Fe 2 O 3 , Fe 3 O 4 or FeS 2), cork powder and sodium carbonate in three previous works, have been studied mineralogically using the quantitative Rietveld XRD method. Comparisons between the mineral percentage in the raw materials and the phase percentage in the aggregate have been carried out. Additionally, independence contrast tests have been conducted to determine if significant relationships exist between the raw material mineralogical composition and the aggregate phase composition. Based on these statistical results, the miner-alogical evolution, the possible reactions that may have taken place and the type of atmosphere required for them have been presented. Mullite, metallic iron, cristobalite, hematite, magnetite, hercynite, fayalite, clino-pyroxenes, troilite, nepheline and amorphous material were new phases produced in the aggregates. The presence and/or percentage of the majority of them were greatly influenced by the added iron phase and by the type of atmosphere in the aggregates. In the latter, cork powder and/or sodium carbonate addition played an important role since their thermal decomposition could give rise to different conditions (oxidizing, reducing or both) depending on whether it is the external or internal zone of the aggregates
... The particular implementation of the PSPW DFT approach used is the one in the NWCHEM series of codes, while the second is the one in the CRYSTAL series of codes. The DFT implementation is based on the Kohn-Sham formalism, in which the energy of the system is written in the form of the Kohn-Sham functional: (1) where in equation (1), Eion is the Coulomb energy of interionic interactions, {R} denotes the momentary set of ionic (i.e., nuclear) positions, Vion is the interaction potential between electrons and ions, and Exc[(r)] is the exchange-correlation energy functional. The electron density is defined as: ...
Many analytical methods have been successfully employed for the study of minerals, in particular, vibrational infrared (FTIR) and Raman spectroscopies and X-ray powder diffraction (XRPD). The advantages of the vibrational spectroscopic techniques for identifying and characterizing minerals include: rapid and versatile use; qualitative and quantitative chemical signatures; distinctive chemical fingerprint of a material; indirect determination of the crystal features (polymorphism, isomorphism, coordination, degree of deformation of structural polyhedra); small sample quantity (area less than 1 μm2 for Raman); wide coverage of 4,000 – 50 cm−1 region in a single scan; in situ and direct measurements without sample preparation; nondestructive use; etc. On the other hand, XRPD is a destructive technique that, depending on the method used and the density of the material, requires from a few micrograms up to around 5 grams of sample quantity for analysis. In spite of that, it is a rapid and powerful technique used in mineral studies with relatively straightforward interpretation of the results. During the last decade, portable X-ray powder diffractometers for the nondestructive analysis of art and archeological materials have been developed along with the portable and hand-held vibrational spectroscopy instrument. Here, some advantages and limitations in the process of the complementary use of FTIR and Raman vibrational spectroscopy and XRPD for identification and characterization of minerals are outlined.
... Powdered samples were scanned from 5º to 90º 2θ at a scan rate of 4º per minute. Quantitative Rietveld analysis (Bish and Post, 1993) of the shale samples was performed using Siroquant TM V5.0 software. ...
This study aims to investigate the phenomenon of vitrinite reflectance (VRo) suppression in the Devonian-Lower Mississippian New Albany Shale in the Illinois Basin, USA. Thirty-two samples from Indiana and Illinois were analyzed using organic petrography (vitrinite reflectance measurements and maceral analyses) and organic geochemistry (Rock-Eval and biomarkers) techniques. Based on VRo variations, we suggest that vitrinite reflectance suppression occurs in both locations. This conclusion is supported by vitrinite reflectance equivalent values obtained from biomarker ratios. The study documents strong negative relationships between alginite and alginite + solid bitumen content and measured VRo values, suggesting that the contribution of these macerals can be used to determine the correction to measured VRo values. No relationship between VRo and Rock-Eval Tmax was revealed. Still, a positive correlation was found between alginite and alginite + solid bitumen content versus the hydrogen index (HI), further emphasizing the role of maceral composition in assessing the thermal maturity and hydrocarbon generation potential of the New Albany Shale.
... The mineralogy of the kaolin and the specimens has been quantitatively determined by X-ray diffraction with Rietveld refinement on randomly oriented powder samples [24,25]. For this purpose, a representative fraction of the specimens was previously ground below 53 µm in an agate mortar. ...
The construction sector provides 14.8 million jobs in the European Union. However, it also accounts for 36% of greenhouse gas emissions and 35% of total waste. High-temperature ceramic manufacturing consumes substantial energy, yielding basic structural products. The alternatives presented, such as geopolymers, still do not replace traditional materials and are not as sustainable as believed. This innovative study combines hydro-thermal zeolitization with kaolin-based ceramics fired at both conventional (900ºC) and much lower temperatures (600ºC), exploring varied conditions, including the use of microplastic wastes as pore-forming agents. Significant zeolite crystallization (15-74%) and mechanical strength increase (2-37-fold compared to untreated materials) is demonstrated in granular specimens, especially when adding microplastics. Geopolymerization appears as a secondary process during treatment. This innovative method offers energy-efficient lower temperatures , transforming fired specimens into zeolite-enriched, robust materials, adaptable to current technology. This study paves the way for further research, opening up a new field of study on hydrothermally manufactured Zeolitic Construction Materials.
... The whole-rock samples were ground to a fine powder. X-ray diffractograms of the samples were subjected to quantitative mineralogical analysis using the Rietveldbased Siroquant V5 software package (Bish & Post, 1993). ...
Thin tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation are laterally widespread in the central part of the West Siberian Basin ( ca 0.5 million km ² ). However, the source of the tuff beds remains unclear. The stratigraphy, geochemistry and geochronology of the tuff beds were investigated to reveal their magmatic origin and potential source region. Most of the tuff beds are recorded in member 4 and can be correlated through the Bazhenovo sequence. Thin‐section petrography and X‐ray diffraction indicate that the tuffs mostly comprise clay minerals and K‐feldspars. Less common minerals are plagioclase, quartz and pyrite. The geochemical composition of the Bazhenovo tuff beds suggests a parental magma origin of andesite/basalt, which came from volcanic arc‐related settings. Considering the results of geochemical studies along with LA‐ICP‐MS zircon U–Pb dating (141.3 ± 0.3/2.8 Ma), the palaeovolcanoes of the Caucasus region or south‐east Mongolia–North‐East China are one of the potential source regions of the tuffs. The record of these tuffs indicates the intensive volcanic eruption during the Volgian–Ryazanian, accompanied by a very low‐sedimentation rate and preservation in a reducing environment. The tuff beds have broad implications as an isochronous marker horizon and constraints for the numerical age of the Jurassic–Cretaceous boundary in the Boreal Realm.
... Diagnostics of the mineral composition of bulk samples and samples of isolated clay fractions was conducted using the method of comparison of experimental and reference X-ray diffraction patterns. Quantitative mineral analysis was conducted through the full-profile processing of X-ray patterns from non-oriented preparations using the Rietveld method [29]. Oriented specimens were prepared from clay fraction samples and studied in an air-dried state and after saturation with ethylene glycol vapor in a desiccator for 24 h [30]. ...
Due to various historical events, in the Russian Federation, in addition to the radioactive waste storage facilities used in world practice, there are various nuclear and radiation hazardous facilities that require special procedures for monitoring and decommissioning. One of these facilities is the disposal site for LRW on the territory of the JSC Siberian Chemical Plant, where specially prepared waste is injected into sand reservoirs lying at depths of 300–350 m between clayey strata. This study examines in detail the features of the lithological and mineral composition of reservoir sands and aquitards. The processes of environmental transformation in reservoir sands, which lead to changes in the composition and structure of rocks, were characterized. These processes manifest themselves in the form of the development of leaching zones and their “healing” with newly formed smectite, the destruction of terrigenous grains, including the development of cracks, and the growth of newly formed smectite in the pore space of reservoirs. The forms of occurrence and localization of authigenic smectite formed as a result of technogenic impact are described. It has been shown that, despite the obvious impact of highly reactive solutions accompanying liquid radioactive waste, the insulating properties of the geological environment are maintained and even improved to some extent.
... XRD was conducted using a PANalytical X'Pert3 diffractometer on homogenized and micronized powders. The diffractograms were analyzed using HighScore Plus by PANalytical and quantified using the Rietveld method [2][3][4] with BGMN AutoQuan software. Automated mineralogy was undertaken using a Hitachi SU3900 SEM fitted with a single large area (60 mm 2 ) Bruker SDD energy-dispersive spectrometer and running the AMICS automated mineralogy software package (Figure 3). ...
... XRD was conducted using a PANalytical X'Pert3 diffractometer on homogenized and micronized powders. The diffractograms were analyzed using HighScore Plus by PANalytical and quantified using the Rietveld method [2][3][4] with BGMN AutoQuan software. Automated mineralogy was undertaken using a Hitachi SU3900 SEM fitted with a single large area (60 mm 2 ) Bruker SDD energy-dispersive spectrometer and running the AMICS automated mineralogy software package (Figure 3). ...
... Å), and a secondary monochromator operated at 40 kV and 30 mA. Rietveld refinement procedure was developed using Highscore Plus software®, based on the work of Bish and Post [30]. ...
The increasing demand for energy storage devices requires sustainable practices for implementation, functionalization and recycling procedures that enable a circular economy with minimal wastes. Zinc and manganese are non-critical raw materials with an environmentally friendly character and proven merits in several energy storage solutions, amongst which supercapacitors, important electrochemical energy storage devices able to manage high-power, however lacking energy density. In this work, we demonstrate how these materials can be combined to improve the energy storage ability of manganese-based electrodes, through a simple, low-cost, and eco-friendly chemical precipitation method. The manipulation of manganese-based spinel was performed through the introduction of zinc, developing an enhanced electrochemical response in aqueous electrolyte media. A binary Mn3O4 + ZnMn2O4 phase achieved a high specific capacitance of 238 F/g at 0.5 A/g in a 1 V potential window. This material displayed 80.5 % rate capability at 10 A/g, and excellent capacitance retention (97 %) after 5000 consecutive GCD cycles. Furthermore, the work evidences that the concentration of zinc in the ZnMn2O4 structure can enlarge the active potential window up to 1.2 V, keeping high-rate reversibility. These electrodes reached a specific capacitance of 175 F/g at 0.5 A/g, 84 % rate capability at 10 A/g, and 78 % capacitance retention after 5000 consecutive GCD cycles. A comprehensive electrochemical study was performed to extract information on the energy storage mechanisms of the developed Manganese-based materials.
... It consists of analyzing powder diffraction data in which the all the components contributing to a calculated diffraction pattern are fitted, step by step, to the measured pattern by least-squares methods. As a fundamental parameters approach [30] was selected, refined parameters include the instrumental variables and the complete crystallographic information, among others [31]. ...
This study presents the results of the mineralogical characterization of Ti-Zr ore from the Jiboia deposit, located in the municipality of Brejo Grande, Sergipe State, Brazil. The goal is to identify the main Ti, Zr, and REE carrier phases in the different particle size fractions in order to subsidize the development of a cost-effective processing route for the production of heavy minerals concentrate. The mineral resources are estimated at 31.5Mt @ 3.5% of total heavy minerals (THM) for the Jiboia Ti-Zr deposit, of which 5 Mt @ 3.39% THM were classified as measured and indicated. The mineralogy of the heavy mineral concentrate recalculated to 100% is represented by 22% pseudorutile, 20% ilmenite, 15% zircon, 5% rutile, 2% monazite, and 36% gangue. The ore minerals are preferably concentrated in the 150 × 53-μm granulometric fractions, which represents 80% of the THM and only 27% of the ROM (Run-of-Mine) ore. Therefore, by cutting the ore to 150 μm, it is possible to discard 73% of the ROM mass and recover 80% of the THM, including 100% of the zircon and monazite which are the most valuable minerals present in the heavy mineral concentrate. The global recovery of THM starts to decline rapidly in the fractions finer than 106 μm and the mass disposal (tailing) does not follow in the same proportion. Higher zircon contents in the concentrates of the fractions finer than 150 μm imply a significantly lower recovery of heavy minerals like ilmenite, pseudorutile, and rutile that make the fractions coarser than 150 μm.
... Each sample was scanned initially in air-dried and ethylene glycol solvated states and after heating up to 550 • C for 2 h. Mineral quantification was performed using Rietveld refinement (Bish and Post, 1993) with PDXL and Siroquant software (Taylor, 1991). ...
The East Siberian Arctic shelf is renowned for its active methane-rich fluid seeps, confirmed by numerous gas flares in the water column and direct observations of methane release from the seafloor. These cold-seep sites serve as natural laboratories for studying the impact of methane seepage on early diagenesis, authigenic mineral formation, and the geochemical cycles of carbon, sulfur, and other elements. This study examines the grain size and chemical composition of two sediment types from the Laptev Sea shelf: cold-seep sediments influenced by sulfate-driven anaerobic methane oxidation, and unaffected “seep-free” sediments (i.e., control site). High methane concentrations (up to 649 μM/L) in the surface layer of sediments indicate that the sulfate–methane transition zone is found close to the sediment–water interface approximately 5–6 cm below the seabed. At the
cold-seep site, thin layers containing up to 40% sand fraction were discovered among the fine-grained sediments.
We infer that upward-migrating fluids may contribute to the remobilization of the fine fraction, resulting in concentration of coarse particles. Cold-seep sediments are characterized by molybdenum (Mo) enrichment compared to the lithological background, although one “seep-free” core exhibits evidence of authigenic Mo deposition. The Mo concentration (up to 16.8 ppm) indicates that enrichment occurs under sulfidic conditions restricted to pore water, which are caused by anaerobic methane oxidation. The high Mo concentration in one “seep-free” core likely implies past cold-seep activity. A general Mo–U covariation indicates that the molybdenum enrichment in cold-seep sediments from the Laptev Sea outer shelf is controlled by a weak particulate shuttle process.
... (14) Apesar das vantagens que o método de Rietveld oferece, é necessário ter alguns cuidados na hora de interpretar os resultados. (15) A influência de orientação preferencial, extinção primaria e detecção não-linear devem ser reduzidas neste método. Além disso, o resultado final achado por este método pode sofrer variações significativas se outro mineral é acrescentado, eliminado ou substituído. ...
... Corundum (20 wt%) was added to the samples as an internal standard. Qantitative analysis was performed using the combined Rietveld and Reference Intensity Ratio (RIR) methods (Bish and Post, 1993;Gualtieri et al., 1996). The phase analysis was refined using X'pert HighScore Plus software, version 4.9, using the goodness of fit χ 2 , the profile residual R p and the weighted profile residual R wp as figures of merit to assess the quality of the refinement. ...
Mud volcanoes in northwestern Colombia are used by local people as inexpensive recreation and wellness centres, especially for pelotherapy. However, the potential therapeutic value of the muds and thermal waters released by these volcanoes has not been fully investigated. The main objective of this research is to determine the potential therapeutic value of the solid and liquid fractions of the muds sampled from nine mud volcanoes located along the northwestern Caribbean coast of Colombia through geochemical and mineralogical analysis. An evaluation of the granulometric characteristics was also carried out. The presence of a hypertonic saline environment created by secondary volcanic processes is indicated by the thermal fluid fraction. The mineral composition of the muds is dominated by quartz, phyllosilicates (kaolinite, smectite, illite and chlorite), feldspar, carbonates (dolomite, calcite) and a significant amorphous component. Based on the composition of the clay fraction, three distinct groups can be distinguished: (i) kaolinite-rich, (ii) illite-rich, and (iii) chlorite-rich. These muds are suitable for use by the local population due to the extremely low levels of contaminants harmful to human health, such as potentially toxic elements, nitrates, nitrites or fluorides. The results of this study suggest that the muds and thermal waters released by these mud volcanoes have potential therapeutic value. Further research is needed to confirm these findings and to investigate the specific mechanisms by which these muds and waters can be used in medical practice.
... A Pilatus 300 K detector with a 172-pixel size was used to collect the diffracted intensities with long exposure time per frame, in the range 30-60 min, to ensure high quality data. The identification of the crystalline phases in the XRPD patterns was carried out through the EVA-Bruker software (Bruker AXS, Karlsruhe, Germany), using the PDF2-2023 database, and furtherly validated through a Rietveld refinement of the XRPD patterns 36 , carried out using the Topas-Academic v7 software 37 . ...
Pyrolysis in an inert atmosphere is a widely applied route to convert tannery wastes into reusable materials. In the present study, the Cr(III) conversion into the toxic hexavalent form in the pyrolyzed tannery waste referred to as KEU was investigated. Ageing experiments and leaching tests demonstrated that the Cr(III)–Cr(VI) inter-conversion occurs in the presence of air at ambient temperature, enhanced by wet environmental conditions. Microstructural analysis revealed that the Cr-primary mineral assemblage formed during pyrolysis (Cr-bearing srebrodolskite and Cr-magnetite spinel) destabilized upon spray water cooling in the last stage of the process. In the evolution from the higher to the lower temperature mineralogy, Cr is incorporated into newly formed CrOOH flakes which likely react in air forming extractable Cr(VI) species. This property transforms KEU from an inert waste to a hazardous material when exposed to ordinary ambient conditions.
... In general, all procedures were carried out according to generally accepted recommendations [41]. Quantification was performed using the Rietveld method [42] with PDXL and Siroquant software (version 5) using the PDF-2, PDF-4 and PDF-14 databases (ICDD, Denver, CO, USA). Data on glauconite were obtained from the PDF 2014 database, card PDF 00-063-0583. ...
This article presents the results of a study of glauconite obtained from phosphate rock waste. The aim is to study the morphological, structural and chemical characteristics of glauconite and to determine the potential for secondary use of mining waste in the agricultural sector. The electromagnetic separation method was used to obtain glauconite concentrate. The optimum parameters for obtaining the maximum mineral content in the concentrate were determined. Studies have shown that glauconite is characterised by globular, granular grains of the highly mature variety. Glauconite almost invariably contains inclusions of pyrite and apatite, which significantly improve the characteristics of the fertiliser. Laboratory experiments have shown that glauconite waste and glauconite concentrate have a positive effect on plant growth and development. The high potassium content, the favourable globular shape of the grains, and the presence of apatite and pyrite inclusions indicate the potential use of glauconite from mining waste as a potash fertiliser. Application of glauconite fertiliser to the soil will provide an opportunity to improve its texture, providing better moisture and aeration. The use of glauconite fertiliser is particularly valuable on acidic soils where apatite can be dissolved, making phosphorus available to plants. This nutrient additionally favours plant growth, as well as reducing the risk of heavy metal accumulation in the soil. Thus, glauconite from the waste of the Egorievsk deposit represents a promising fertiliser for improving soil quality and increasing crop yields.
... Each sample was assessed in the air-dried and ethylene glycol-solvated states after 24 h in a desiccator at roughly 60 • C. Methods described in [76,77] were used to identify glauconite and smectite. Quantitative mineral evaluation was accomplished using Rietveld analysis [78] with PDXL and Siroquant software packages [79]. ...
This paper studies the chemical and mechanochemical preparation of glauconite with ammonium dihydrogen phosphate (ADP) nanocomposites with a ratio of 9:1 in the vol.% and wt.%, respectively. The methods include X-ray diffraction analysis, scanning electron microscope with energy-dispersive X-ray spectroscopy, transmission electron microscopy, infrared spectroscopy, and differential thermal analysis with a quadruple mass spectrometer. The manufactured nanocomposites keep the flaky glauconite structure. Some glauconite unit structures have been thickened due to minimal nitrogen (ammonium) intercalation into the interlayer space. The globular, granular, or pellet mineral particles of nanocomposites can be preserved via chemical techniques. Globular and micro-aggregate particles in nanocomposites comprise a thin film of adsorbed ADP. The two-step mechanochemical method makes it possible to slightly increase the proportion of adsorbed (up to 3.2%) and intercalated (up to 6.0%) nutrients versus chemical ways. Nanocomposites prepared via chemical methods consist of glauconite (90%), adsorbed (1.8–3.6%), and intercalated (3.0–3.7%) substances of ADP. Through the use of a potassium-containing clay mineral as an inhibitor, nitrogen, phosphorus, and potassium (NPK), nanocomposite fertilisers of controlled action were obtained. Targeted and controlled release of nutrients such as phosphate, ammonium, and potassium are expected due to various forms of nutrients on the surface, in the micropores, and in the interlayer space of glauconite. This is confirmed via the stepwise dynamics of the release of ammonium, nitrate, potassium, and phosphate from their created nanocomposites. These features of nanocomposites contribute to the stimulation of plant growth and development when fertilisers are applied to the soil.
... The production of abundant Fe-containing amorphous material at Gale crater 1 may therefore also be consistent with wet and near-freezing mean annual conditions. The abundant Ferich amorphous material within Gale Crater thus bolsters arguments 22,[47][48][49][50] for the presence of wet but cold conditions during formation followed by long term cold and dry conditions facilitating preservation. Returned samples from Mars will allow a detailed comparison of martian amorphous material with material such as that examined here to better understand past martian environments. ...
The assemblage of secondary minerals in martian rocks can help constrain the characteristics of past surface and subsurface fluids as well as past climatic conditions. X-ray amorphous material is an important part of martian surface materials, making up 15–73 wt.% of sedimentary rocks and eolian sediments in Gale crater, Mars. This X-ray amorphous material is variably siliceous, Fe-rich, and contains volatiles, and it therefore likely contains incipient weathering products. To better understand the implications of this material for past aqueous and climatic conditions in Gale crater and elsewhere on Mars, we investigated X-ray amorphous material formation and longevity within terrestrial Fe-rich soils of different ages in terrestrial mediterranean, subarctic, and desert climates using bulk and selective dissolution methods, Rietveld refinements of powder XRD patterns, and transmission electron microscopy. Results indicate that in situ aqueous alteration is required to concentrate Fe into the clay-size material and to form abundant Fe-containing X-ray amorphous material. Cooler climates promote the formation and persistence of Fe-rich X-ray amorphous material whereas warmer climates promote the formation of crystalline secondary phases. Fe-rich X-ray amorphous material formation and persistence on Mars are therefore consistent with past cool and relatively wet environments followed by long-term cold and dry conditions.
... Glauconite and smectite were determined according to the procedures described in (Moore and Reynolds Jr., 1997) and (Hillier, 2003). Quantitative mineralogical analysis of the whole rock data was achieved using Rietveld analysis (Bish and Post, 1993) with PDXL and Siroquant software (Taylor, 1991). ...
... On two contrasting natural samples from a Brazilian pisolitic duricrust (Alto Paranaíba region, Minas Gerais State), the XRD_rotat patterns are compared to the better-resolved XRD_synch patterns. Related data allowed us to determine parameters that are useful to recognize distinct generations of iron phases (i.e., mean coherent domain (MCD) sizes and Al substitution rate) and the weight percentage (wt %) ratio of the main phases using Rietveld refinement analysis (Bish and Post, 1993). Indeed, Al is a typical substitutional impurity in hematite (up to 15 mol %) and goethite (up to 33 mol %) and thus is due to specific conditions of formation, for example related to the dissolution of kaolinite while the iron oxide crystallizes (Schwertmann et al., 1979;Schulze, 1984). ...
Interpreting the ages of supergene mineralogical phases in
laterite is complex because they consist of polycrystalline mixtures of
different phases at the microscopic scale that could be crystalized at
different epochs. Among the geochronometers, the (U-Th)/He method on
hematite and goethite is more often used, but ages can be difficult to interpret
due to phases mixing. To resolve this issue, this study proposes a
methodology for performing detailed mineralogical analysis of hematite and
goethite single grains prior to their dating using the (U-Th)/He method.
Strictly non-destructive mineralogy of single grains is not achievable by
classical tools, such as conventional powder XRD (X-ray diffraction; requiring at least some milligrams
of powder) or SEM (scanning electron microscopy; that can contaminate the grain by coating or fixing).
Therefore, we performed X-ray diffraction patterns of single grains using
high-flux X-ray beams from both a rotating anode (XRD_rotat)
laboratory diffractometer and a synchrotron beamline (XRD_synch) and compared the results in order to design a method based on
XRD_rotat only. For this purpose, two samples from the
pisolitic facies of a Brazilian ferruginous duricrust (Alto Paranaíba
region, Minas Gerais State, Brazil) were chosen because they presented a
usual heterogeneity. Rietveld refinements of the XRD patterns obtained from
both XRD_rotat and XRD_synch yielded similar
results for the weight percentage ratio of the main phases and mean coherent domain
sizes and less similar results for Al substitution rates, thus validating the
XRD_rotat approach. No beam damage was observed when
increasing X-ray exposure time, neither on XRD patterns nor on (U-Th)/He ages. Hence, sub-millimeter, undisturbed grains can be used to analyze the
mineralogy of ferruginous duricrusts by XRD_rotat with a
short exposure, and the same grains can subsequently be dated by (U-Th)/He geochronology analysis. The (U-Th)/He dating of pisolitic core and cortex
grains also provided meaningful ages: they revealed two evolution phases of
the ferruginous duricrust, which occurred at or before the Oligocene for
the pisolitic core and middle Miocene for the pisolitic cortex, agreeing with the
previous model for the development of pisolites. The mineralogy of single
grains selected for dating is helpful for discussing the crystallization
ages, and the high-flux XRD approach may be applied to other supergene
mineral parageneses used for absolute dating.
... Iron occupation was refined for the barbosalite-like compounds in order to properly account for relative intensities. Scale factors were refined for all phases and were used to calculate relative weight fraction of the mineral phases in the samples using the classical procedure by Bish and Post (1993), assuming a sum of weight fractions equal to one. ...
Thermococcales, a major order of hyperthermophilic archaea inhabiting iron- and sulfur-rich anaerobic parts of hydrothermal deep-sea vents, are known to induce the formation of iron phosphates, greigite (Fe3S4) and abundant quantities of pyrite (FeS2), including pyrite spherules. In the present study, we report the characterization of the sulfide and phosphate minerals produced in the presence of Thermococcales using X-ray diffraction, synchrotron-based X ray absorption spectroscopy and scanning and transmission electron microscopies. Mixed valence Fe(II)-Fe(III) phosphates are interpreted as resulting from the activity of Thermococcales controlling phosphorus-iron-sulfur dynamics. The pyrite spherules (absent in abiotic control) consist of an assemblage of ultra-small nanocrystals of a few ten nanometers in size, showing coherently diffracting domain sizes of few nanometers. The production of these spherules occurs via a sulfur redox swing from S0 to S-2 and then to S-1, involving a comproportionation of (-II) and (0) oxidation states of sulfur, as supported by S-XANES data. Importantly, these pyrite spherules sequester biogenic organic compounds in small but detectable quantities, possibly making them good biosignatures to be searched for in extreme environments.
... Clay minerals were identified according to the procedures described in Moore and Reynolds Jr. (1997) and Hillier (2003). Quantitative mineralogical analysis of the whole rock data was performed by Rietveld analysis (Bish and Post, 1993) with PDXL and Siroquant software (Taylor, 1991) along with peaks matching using the PDF-2 and PDF-4 databases (ICDD, Denver, USA). ...
The formation of clay minerals in volcanic successions follows various evolutionary trends, the understanding of which is crucial for estimating the age of volcanism and the prospecting clay deposits. Early Devonian volcanics within the Byskar Series of the Minusa Depression (Khakassia) are variably altered to a range of phyllosilicate mineral assemblages. This study highlights the origin and formational conditions of the clay minerals, including illite, glauconite, smectite (saponite) and chlorite. Detailed mineralogical and chemical investigation identifies the predominant phyllosilicates, including 1 M illite, illite-smectite (R = 3), 1 M glauconite, smectite, chlorite and kaolinite within trachyandesite, trachyte, and rhyodacite. The phyllosilicates formed by the diagenetic transformation of volcanics after eruptive phases. Evolution trends of phyllosilicates depend largely on the composition of the volcanic substrate. The smectite to illite trend developed due to the dissolution of felsic volcanics and the alteration of smectites into illites with the K+, Al3+ and Mg2+ dominating the mineral formation system. The illites evolved by the substitution of Fe2+ and Mg2+ for Al3+ in the octahedral sheets of smectites. The K+, which was released due to devitrification of felsic substances, was introduced into the interlayer sites for compensating the layer charge originated by the isomorphic substitution in tetrahedral and octahedral sheets. The smectite to glauconite transition trend corresponds to the devitrification and dissolution of alkaline intermediate-felsic volcanics. Early formed dioctahedral smectites evolved into glauconite probably with the predominance of K+ and Fe2+/3+ ions in the formation environment. The substitution of Fe2+/3+ to Al3+ and Mg2+ in the octahedral sheets of smectite contributed to the formation of a layer charge and the entry of exchangeable K+ into the interlayers of glauconite. The third trend involved the formation of smectites (saponites) or chlorites within the intermediate volcanics possibly with Mg-rich but K-poor mineral system.
... The techniques are an implementation of Rietveld analysis (Post and Bish 1989;Bish and Post 1993), which was used first to understand and refine crystal structure as determined by XRD. Since the 1980s, the method has been extended to quantification of phases in mineral samples. ...
A prerequisite to understanding the evolution and resource potential of a basin is to establish a reliable stratigraphic framework that enables the correlation of rock units across multiple depocentres. Establishing a stratigraphic model for the Adavale Basin is challenging due to its structurally complexity, lack of well penetration and its lateral changes in facies. Biostratigraphy appears broad-scale, and despite providing chronostratigraphic control for the Lower Devonian Gumbardo Formation when combined with U/Pb zircon geochronology, the rest of the Devonian succession is hampered by a lack of microfossil assemblages and their poor preservation. The aim of this study is to establish an independent chemostratigraphic correlation across the Adavale Basin using whole rock inorganic geochemistry. Within this study, a total of 1489 cuttings samples from 10 study wells were analysed by Inductively Coupled Plasma – Optical Emission Spectrometry and Inductively Coupled Plasma – Mass Spectrometry for whole rock geochemistry, in order to establish an independent chemostratigraphic zonation scheme. Based on key elemental ratios selected to reflect changes in feldspars, clay minerals and provenance, the Devonian-aged stratigraphy is characterised into four chemostratigraphic mega-sequences that encompass the Gumbardo Formation (Mega-sequence 1); the Eastwood Formation, the Log Creek Formation and the Lissoy Sandstone (Mega-sequence 2); the Bury Limestone and the Boree Salt formations (Mega-sequence 3); and the Etonvale and the Buckabie formations (Mega-sequence 4). These mega-sequences have been further subdivided into a series of chemostratigraphic sequences that can be correlated across the study wells, establishing a regional correlation framework.
... The FPS method is based on the principal that the observed diffraction pattern is the sum of signals from the individual phases that compose a sample [19,20,22,32]. The Rietveld method, which differs from single reflection techniques, is a process of refinement between observed and calculated patterns by partial least squares regression based on a crystal structure database [33,34]. The weight of each phase in a sample is obtained from the optimal value of the scale factor during refinement. ...
X-ray diffraction (XRD) analysis, as one of the most powerful methods, has been widely used to identify and quantify minerals in earth science. How to improve the precision of mineral quantitative analysis is still a hot topic. To date, several quantitative methods have been proposed for different purposes and accompanied by diverse software. In this study, three quantitative mineral analysis methods, including the reference intensity ratio (RIR), Rietveld, and full pattern summation (FPS) methods, are compared and evaluated to systematically investigate their accuracy and applicability. The results show that the analytical accuracy of these methods is basically consistent for mixtures free from clay minerals. However, there are significant differences in accuracy for clay-mineral-containing samples. In comparison, it seems that the FPS method has wide applicability, which is more appropriate for sediments. The Rietveld method has been shown to be capable of quantifying complicated non-clay samples with a high analytical accuracy; nevertheless, most conventional Rietveld software fails to accurately quantify phases with a disordered or unknown structure. The RIR method represents a handy approach but with lower analytical accuracy. Overall, the present results are expected to provide a potentially important reference for the quantitative analysis of minerals in sediments.
... The most reliable and robust methods for determination of base cation weathering are based on soil mineralogy; however, wide-scale regional application of these methods is limited by the availability of quantitative soil mineralogy, which is a challenge in using PROFILE [10]. X-ray Diffraction (XRD), which is based on the crystallographic structure of minerals, is typically used to estimate quantitative soil mineralogy in conjunction with Reitveld fitting [11]. However, it can be a time-consuming procedure, especially if a large located in Manitoba [26]. ...
Weathering of soil minerals provides base cations that buffer against acidity, and nutrients that support plant growth. In general, direct observations of soil minerals are rare; however, their abundance can be determined indirectly through soil geochemistry using normative-calculation procedures. This study compiled a data set of major oxide content from published and archived soil geochemical observations for 1170 sites across Canada (averaged over the soil profile [A, B, and C horizons], weighted by depth and bulk density to a maximum depth of 50 cm). Quantitative soil mineralogy (wt%) was systematically determined at each site using the normative method, ‘Analysis to Mineralogy’ (A2M); the efficacy of the approach was evaluated by comparison to X-ray Diffraction (XRD) mineralogy available for a subset of the study sites. At these sites, predicted A2M mineralogy was significantly related to estimated XRD, showing a strong linear relationship for plagioclase, quartz, and K-feldspar, and a moderate linear relationship for chlorite and muscovite. Further, the predicted A2M plagioclase content was almost identical to the estimated XRD soil mineralogy, showing no statistical difference. The Canada-wide predicted quantitative soil mineralogy was consistent with the underlying bedrock geology, such as in north-western Saskatchewan and north-eastern Alberta, which had high amounts of quartz due to the Western Canadian Sedimentary Basin. Other soil minerals (plagioclase, potassium feldspar, chlorite, and muscovite) varied greatly in response to changing bedrock geology across Canada. Normative approaches, such as A2M, provide a reliable approach for national-scale determination of quantitative soil mineralogy, which is essential for the assessment of soil weathering rates.
... Quantification of phases present can be performed through several established methods (Bish and Post, 1989;Henderson et al., 2014). Advanced techniques, such as Rietveld refinement, can allow for precise determination of crystallographic parameters of specific minerals (Bish and Post, 1993) as well as quantify the proportion of individual phases within a sample. Techniques have been developed utilizing XRD to quantify low levels (100's of PPM) in asbestos samples (Gunter et al., 2007;Sanchez and Gunter, 2006). ...
Mineral specimens and mineral reference materials should be understood to be mixtures of various mineral species and the properties of each individual species will likely represent a range of quantifiable values and qualitative characteristics. The use of incompletely characterized mineral specimens may introduce significant uncontrolled variables in any experiment. Any mineral characterization should include an understanding of the bulk properties of the specimen as well as microanalytical and crystallographic characterization of individual mineral phases. This characterization should comprise a range of length scales to accommodate naked-eye level observations up to electron microscopic observations and analyses. Large spatial scale observations are useful to describe the physical properties of the material and understand the scale of inhomogeneities that may be present in a mineral sample. Microanalysis provides critical compositional and crystallographic information for mineral identification. It is critical to recognize where gaps might exist in the data produced during the characterization of a material and if those gaps are critical to evaluating the effect those minerals might have on the result of a given experiment. Likewise, it is critical to understand the interplay of various minerals that might be present in a sample other than the specific mineral of interest. Where accessory minerals are present, even if only trace amounts, that could have a major impact and those minerals need to be isolated, or their impact accounted for in the interpretation of results. Dimensional characterization of particulate produced from a mineral specimen is not as simple a task as it might appear. Dimensional data can be produced through any of several microscopic techniques, each with specific limitations and potential to be biased due to sample preparation technique. This understanding of the full composition of a mineral specimen cannot be obtained through rudimentary examination and it cannot be taken for granted that it has been performed by the supplier of the specimen.
... Samples were analyzed from 3 to 65° 2θ. XRD and abundances were quantified via the Rigaku PDXL 2 software, using a Rietveld structure refinement method (e.g., Bish & Post, 1993). ...
Lakes are invaluable archives of past ecosystem changes, and this study focuses on one of the largest freshwater lakes in the western US. At 380 km², Utah Lake is the third-largest freshwater lake in the USA west of the Mississippi River. Adjacent to an urban corridor, it is an important resource for surrounding communities as well as being impacted by them. Recently, large harmful algal blooms have drawn attention to its ecosystem health, and a rapidly growing population and recent lengthy drought continue to stress the lake. Its sedimentary record is an important archive of human impacts to ecosystems. Three freeze cores were obtained in 2019 to investigate environmental changes and human impacts since European settlement began in ~1850. After establishing core chronologies using ²¹⁰Pb, ¹³⁷Cs and correlation, proxies investigated included pollen, C- and N-isotopes, nutrients (C, N, and P), and heavy metal abundances. Low C:N ratios indicated that organic matter budget was dominated algae rather than plant debris. Discernable increases in nutrients began in the mid-twentieth century, whereas increases in Pb began as early as ~1900. Nutrient increases were related to agricultural runoff and variably treated sewage effluent, whereas heavy metal loading was due to heavy industry (iron and steel), coal combustion, and urban runoff. Over the last several decades, nutrient and metal loadings have stabilized, indicating a steady state has been reached. Gains in nutrient removal from effluent have been offset by growing populations and decreases in heavy industry and coal combustion have been countered by urbanization. Overall, the lake has been continually oxic, with possible episodes of anoxia during algal blooms. This study also provides a measure of pre_Eurpopean ecosystem health using geochemical baselines in order to establish reasonable water-quality standards.
... The measurements were recorded several times and have demonstrated good reproducibility. To extract the structural parameters such as crystal phase composition, degrees of crystallinity, average linear sizes of crystallites, and lattice constants, the Rietveld refinement (see, e.g., [34]) was applied to the XRD data. XPS is a well-known method providing sensitive probing of chemical bonds in surface layers [35,36]. ...
Mechanisms responsible for spatiotemporal changes in the atomic-molecular architecture of the human femur in intact and osteoarthritis-affected areas were studied using high-resolution X-ray diffraction and spectroscopic techniques. Comparison of the experimental data demonstrates strong deviations of core electron-binding energies, lattice constants of hydroxyapatite crystal cells, linear sizes of crystallites, and degrees of crystallinity for both intact and osteoarthritic areas. The quantitative values of these characteristics and their standard deviations in each area are measured and presented. A systematic analysis of the site-dependent deviations was carried out within the framework of the 3D superlattice model. It is argued that the main mechanism responsible for the deviations arises primarily as a result of carbonization and catalytic reactions at the mineral-cartilage interface. The impact of the mechanism is enhanced in the vicinities of the area of sclerosed bone, but not inside the area where mechanical loads are maximum. Restoration of the atomic-molecular architecture of mineralized bone in the sclerosis area is revealed. Statistical aspects of the spatiotemporal changes in mineralized bone under pathogenic conditions are discussed.
... 14000(Masse et al. 1976;Coimbra et al. 2019). The parameters optimized in this study were: scalar factor, 2θ displacement, sample position, baseline with polynomial coe cients, adjustment to the Bragg diffraction peak shape using modi ed Thompson-Cox-Hastings pseudo-Voigt convolution with axial divergence asymmetry (TCHZ-pV), cell parameters (a, b, c), angular parameters (α, β, γ), network deformation, and anisotropy factor(Caglioti et al. 1958;Bish and Post 1993).Fig. S2a-f illustrated the structural re nement graphs for Ag 3 PO 4 crystals obtained at room temperature and treated at 100, 200, 300, 400, and 500°C, respectively. ...
The incorrect disposal of medicines can trigger an imbalance in the ecosystem of rivers and lakes, as well as human and animal health. Therefore, the heterogeneous photocatalysis technique is a promising technology to minimize or even eliminate these pollutants from aquatic systems. Silver phosphate crystals (Ag 3 PO 4 ) have excellent photocatalytic and bactericidal properties. For the synthesis of crystals of silver phosphate, the method of preparation used was precipitation at room temperature, followed by heat treatment at 100, 200, 300, 400, and 500 ºC for six h. The X-ray Diffraction data show structures with excellent crystallinity, remaining even after temperature variation. Scanning electron microscopy images exhibited a variation in the morphology of the materials with increasing temperature. Diffuse reflectance spectroscopy revealed the materials optical band energy values ranging from 2.33 to 2.41 eV. On the other hand, the Raman and Infrared spectra showed a reduction in the bands referring to the phosphate groups. The Ag 3 PO 4 crystals heat treated at 200 and 500 ºC showed the better performance for the photodegradation of 17α-ethinylestradiol (EE2) with highest kinetic constant (7.42x10 − 3 min − 1 ) and TOF (3.11x10 − 4 min − 1 ) values for photocatalyst test carried out on crystals heat treated at 200 ºC.
... The weighted profile R values are the easiest to understand because they come straight from the square root of the minimum amount, which is scaled using weighted intensities. Typical values of Rwp range from a few per cent for very accurate refinements to 20-30% for X-ray refinements, depending in part on the counting times used, the degree of preferred orientation, and the number of variable parameters [38,39]. The refinements were adequate. ...
The present study aimed to develop the electrical performance of outdoor insulators using a nano-TiO2 coating for railway electrification systems. The prototype design of porcelain insulators with normal coatings and using a nano-TiO2 coating is based on IEC 60815-1. The first test was performed to measure the low-frequency flashover AC voltage under both dry and wet conditions. In addition, the other test was conducted to measure the lightning impulse critical-flashover voltage at positive and negative polarity under dry-normal and wet-contaminated conditions. X-ray diffraction (X-RD) and Scanning electron microscopy (SEM) were used to examine the micro surface and show that the nano-TiO2 coating was adhered to the surface of the outdoor porcelain insulator and exists in an amorphous state. Additionally, it was observed and discovered that scattered nano-TiO2 strengthens the glassy matrix and creates a sturdy barrier that causes flashover voltage to be reduced under conditions of high dielectric strength. Nanostructured ceramic formulations outperform ordinary porcelain in terms of breakdown voltage strength, particularly for the insulators’ low-frequency flashover performances under dry and wet test conditions. However, a significant change in the lightning impulse critical-flashover voltage characteristics is observed and is not much better when adding the nano-TiO2 coating to the porcelain insulators.
... Diffraction patterns were interpreted using the HighScore software version 4.9 (Malvern Panalytical B.V.) and JCPDS PDF-2 database. QPA followed the combined Rietveld and Reference Intensity Ratio (RIR) methods (Chung 1974a, b;Bish and Post 1993;Gualtieri et al., 1996;Gualtieri 2000). The profile was refined using the High Score plus 4.9 software exporting the structure models for each phase from ICSD data library. ...
Delineating hydrothermal alteration and supergene caps is fundamental for mineral exploration of sulfide ores. The aim of this study is to apply a multi-scale workflow based on hyperspectral remote and proximal sensing data in order to delineate hydrothermal dolomitization and supergene alteration associated with the Mississippi Valley-Type Zn-Pb(-Ag) deposit of Jabali (Western Yemen). The area was investigated through hyperspectral images derived from the new launched Italian Space Agency’s PRISMA satellite, which has a higher spectral resolution compared to multispectral sensors and covers the mineral-diagnostic wavelength regions (such as the 2100 nm to 2300 nm range) with a Signal to Noise Ratio (SNR) ≥100. Spectral mineral maps were produced through the band ratios method using specific feature extraction indices applied to the hyperspectral satellite data. The results were validated by using Visible Near InfraRed (VNIR) to Short Wave InfraRed (SWIR) reflectance spectra, mineralogical (XRPD) and geochemical (ICP-ES/MS) analyses on rock samples collected in the Jabali area. The dolomites footprint was mapped using a PRISMA Level 2C image, by enhancing the spectral differences between limestones and dolomites in the SWIR-2 region (major features centered at 2340 nm and 2320 nm, respectively). Gossans were detected due to the Fe³⁺ absorption band in the VNIR region at 900 nm. The Zn-Pb mineralized area, extended for approximately 25 km², was thus identified by recognizing gossan occurrences in dolomites. The study demonstrates that the PRISMA satellite is effective in identifying Zn-Pb mineralized outcrops in sedimentary basins.
... Powdered samples were scanned from 2 to 70°2h with a step size of 0.02°and a count time of 2 s. The patterns were analyzed by Rietveld refinement (Rietveld, 1969;Bish and Post, 1993) with TOpas (Bruker AXS) software to quantitatively determine mineral abundances, with uncertainties determined by the variance of the least squared fit. The XRD results are reported in Table S1 and shown in Fig. S2. ...
... Powdered samples were scanned from 2 to 70°2h with a step size of 0.02°and a count time of 2 s. The patterns were analyzed by Rietveld refinement (Rietveld, 1969;Bish and Post, 1993) with TOpas (Bruker AXS) software to quantitatively determine mineral abundances, with uncertainties determined by the variance of the least squared fit. The XRD results are reported in Table S1 and shown in Fig. S2. ...
The continental crust is an important reservoir for incompatible elements, including the halogen elements (F, Cl, Br, and I), but their concentrations remain poorly known, thus hindering better understanding of the role of the crust in Earth’s halogen cycle. We present halogen data (F, Cl, Br, and I) for twenty-four well-characterized glacial diamictite composites that derive from the upper continental crust (UCC) and were deposited during discrete glacial events at ∼2.9 Ga, ∼2.4–2.2 Ga, 0.75–0.58 Ga, and ∼0.30 Ga. A good correlation between Cl and the highly soluble Na (R² = 0.70), together with low and scattered Cl concentrations in the diamictites (2–279 ppm), indicates significant Cl loss during chemical weathering of the continents. The other halogens (F, Br, and I), however, are not strongly affected by chemical weathering as revealed by their correlations with less soluble elements like K, P, Nd, and Lu, which may be due to their retention in secondary minerals and/or organic matter. Increasing concentrations of F in the composites through time may reflect the evolving composition of the UCC. Using the median values of the Neoproterozoic and Paleozoic diamictite composites, halogen concentrations of the present-day weathered UCC are estimated to be: 575 ± 87 ppm F, 29 ± 20 ppm Cl, 0.65 ± 0.14 ppm Br, and 0.05 ± 0.01 ppm I (errors quoted at the median absolute deviation). Linear correlations between halogens and other elements provide estimates for minimum halogen concentrations of the present-day crystalline UCC: 394 ± 67 ppm F, 83 ± 24 ppm Cl, 0.41 ± 0.04 ppm Br, and 0.03 ± 0.01 ppm I (with 2σ uncertainties). These estimates are all lower than normalized concentrations of elements of similar incompatibility during igneous differentiation, which may reflect loss of halogens via magmatic degassing/exsolution and/or chemical weathering during the formation of the continental crust. The distinct behavior of Cl compared to Br and I during continental weathering leads to a wide range of Br/Cl (2–265 * 10⁻³) and I/Cl (122–197,952 * 10⁻⁶) ratios, and Br/I ratios that are distinctly higher than those of pelagic sediments and marine pore fluids. Similar halogen signals have been reported from the lithospheric mantle and may reflect recycling of terrigenous sediments. The calculated weathering flux of Cl from the continents is quite small compared to the total Cl content of seawater (< 8–34 %), suggesting that Cl in seawater is mainly derived from outgassing of the mantle and/or late volatile accretion. On the other hand, the significantly higher Br and I contents in terrigenous organic-rich sediments compared to those of crystalline bedrocks suggest that significant amounts of Br and I were transported from the oceans to the continents.
... The quantitative mineralogical composition of the original Dt and the phases formed from it was determined by X-ray diffraction (XRD) using a PANalytical ® diffractometer X'Pert Pro model. For this analysis, polycrystalline powder diffractograms were obtained after adding ~25 wt.% alumina to the sample in order to determine both the crystalline and amorphous phases by Rietveld refinement [13,14]. The measurement conditions were as follows: 45 kV, 40 mA, Cu radiation, soller slit of 0.04 rad, antiscattering slit of 1/2°, divergence slit of 1/8°, step size of 0.0167, counting time (s) of 130, Bragg-Brentano HD module and X'celerator detector. ...
The possibility of transforming a diatomite-rich waste from the brewing industry into synthetic zeolites has been investigated. After precalcination at 550 °C to eliminate the retained organic matter, the clean diatomite (Dt; with a Si/Al molar ratio of 17.4), was hydrothermally treated for 24 h with continuous stirring in a 3M NaOH solution at 80 °C. The results of mineralogical characterization by X-ray diffraction with Rietveld refinement have shown a crystallization of 55% of zeolite P, which was neoformed from the amorphous phase, opal-CT and quartz of the starting sample. The spectra obtained by Fourier Transform Infrared Spectrometry have corroborated such zeolitization. N2 adsorption–desorption isotherms have shown that the zeolitized material (Dt-Z) is mesoporous, with almost 60% more specific surface area than Dt (62.6 m2/g vs. 39.4 m2/g), greater microporosity and 40% smaller average pore size than Dt (71 Å vs. 118 Å). This study is a first approximation to know the potential of diatomite wastes as zeolite precursors, for which additional research including an aluminum source will be required.
... O método de Rietveld é reconhecido como uma ferramenta para a quantificação das fases cristalinas presentes em um determinado material, uma vez que todo o espectro é utilizado e não apenas as reflexões mais intensas (1) . Este método consiste em minimizar a diferença entre espectros medidos e calculados, possibilitando o refinamento de parâmetros geométricos das fases presentes, assim como suas características cristalográficas (2,3) . ...
O método de Rietveld é reconhecido como uma ferramenta para a quantificação das fases cristalinas presentes em um determinado material, uma vez que todo o espectro é utilizado e não apenas as reflexões mais intensas (1). Este método consiste em minimizar a diferença entre espectros medidos e calculados, possibilitando o refinamento de parâmetros geométricos das fases presentes, assim como suas características cristalográficas (2,3). A quantificação baseia-se no fato de que cada estrutura tem seu próprio espectro, caracterizado por posições e intensidades específicas. A superposição dos espectros medidos e calculados é realizada por adição e a integral da superfície do espectro de cada fase é proporcional à sua porcentagem mássica e/ou volumétrica na amostra (4-6). AGRADECIMENTOS Tabela 1. Especificações das matérias-primas de acordo com informações dos fabricantes, em porcentagem mássica.
... Samples were measured from 2-70 • 2θ with a step size of 0.02 • . Rietveld refinements (Bish and Post, 1993) were performed using the TOPAS 5 software package (Bruker AXS). The limits of detection by XRD methods are ∼ 1 wt %m depending on the mineral and the count time used for data collection. ...
We report a new sampling strategy for collecting representative samples of
drill core. By splitting the core with a diamond saw into working and
archive halves, the saw cuttings constitute a “channel” sample, the best
subsample from which to obtain an average mineralogical and geochemical
composition of a core. We apply this procedure to sampling core of the lower oceanic crust in the Hess Deep obtained during Expedition 345 of the
Integrated Ocean Drilling Program (now International Ocean Discovery
Program).
Our results show that particles produced by sawing range from sand to clay
sizes. Sand- and silt-sized cuttings can be sampled with a spatula, whereas
clay-sized particles remained in suspension after 12 h and could be
collected only by settling, aided by centrifuge. X-ray diffraction (XRD) analysis and Rietveld
refinement show that phyllosilicates were fractionated into the clay-sized
fraction. Thus, collection of both the sedimented fraction and the clay-sized suspended fraction (commonly > 15 wt % of the total) is
necessary to capture the whole sample. The strong positive correlation
between the recovered sample mass (in grams) and length of core cut demonstrates
that this sampling protocol was uniform and systematic, with almost 1.4 g
sediment produced per centimeter of core cut. We show that major-element
concentrations of our channel samples compare favorably with the
compositions of billet-sized samples analyzed aboard the JOIDES Resolution,
but the results show that individual billet analyses are rarely
representative of the whole core recovered. A final test of the validity of
our methods comes from the strong positive correlation between the loss on
ignition (LOI) values of our channel samples and the H2O contents
calculated from the modal mineralogy obtained by X-ray diffraction and
Rietveld refinement. This sampling procedure shows that grain-sized
fractionation modifies both mineralogical and chemical compositions;
nevertheless, this channel sampling method is a reliable method of obtaining
representative samples of bulk cores. With the ever-increasing precision
offered by modern analytical instrumentation, this sampling protocol allows
the accuracy of the analytical results to keep pace.
For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and three scooped soil samples have been analyzed during the rover’s 30+ km transit. These samples document the mineralogy of over 800 m of flat-lying fluvial, lacustrine, and aeolian sedimentary rocks that comprise the lower strata of the central mound of Gale crater (Aeolis Mons, informally known as Mt. Sharp) and the surrounding plains (Aeolis Palus, informally known as the Bradbury Rise). The principal mineralogy of the sedimentary rocks is of basaltic composition, with evidence of post-depositional diagenetic overprinting. The rocks in many cases preserve much of their primary mineralogy and sedimentary features, suggesting that they were never strongly heated or deformed. Using aeolian soil composition as a proxy for the composition of the deposited and lithified sediment, it appears that, in many cases, the diagenetic changes observed are principally isochemical. Exceptions to this trend include secondary nodules, calcium sulfate veining, and rare Si-rich alteration halos. A surprising and yet poorly understood observation is that nearly all of the ~3.5 Ga sedimentary rocks analyzed to date contain 15–70 wt.% of X-ray amorphous material. Overall, this >800 m section of sedimentary rock explored in lower Mt. Sharp documents a perennial shallow lake environment grading upward into alternating lacustrine/fluvial and aeolian environments, many of which would have been habitable to microbial life.
The improper disposal of pharmaceuticals can disrupt aquatic ecosystems in rivers and lakes, as well as impact human and animal health. Consequently, heterogeneous photocatalysis stands as a promising technology to mitigate or even eradicate these pollutants from aquatic systems. Silver phosphate crystals (Ag3PO4) exhibit exceptional photocatalytic and bactericidal properties. Ag3PO4 crystals were synthesized using the precipitation method, followed by a 6h heat treatment at temperatures of 100, 200, 300, 400, and 500 °C. X-ray diffraction data showcase structures with outstanding crystallinity, which remain stable even under fluctuating temperatures. Scanning electron microscopy images reveal shifts in material morphology as the temperature rises. Diffuse reflectance spectroscopy unveils optical band energy values ranging from 2.33 to 2.41 eV for the materials. Conversely, both Raman and infrared spectra indicate a reduction in bands linked to phosphate groups. Lastly, Ag3PO4 crystals exhibited remarkable performance in the photodegradation of 17α-ethinylestradiol (EE2) during a 280 min test, achieving removal rates of 77.5 %, 71.2 %, 92.4 %, 82.0 %, 41.3 %, and 92.5 % for crystals treated at 25, 100, 200, 300, 400, and 500 °C, respectively. Ag3PO4 crystals treated at 200 and 500 °C demonstrated the highest photocatalytic efficiency, attributed to their enhanced structural and morphological properties.
Alteration of basaltic glass and in situ mineral growth are fundamental processes that influence the chemical and material properties of Earth’s oceanic crust. These processes have evolved at the basaltic island of Surtsey (SW Iceland) since eruptions terminated in 1967. Here, subaerial and submarine lapilli tuff samples from a 192 m-deep borehole drilled in 2017 (SE-02b) are characterized through petrographic studies, X-ray powder diffraction analyses, and SEM–EDS imaging and chemical analyses. The integrated results reveal (i) multi-stage palagonitization processes in basaltic glass and precipitation of secondary minerals from matrix pore fluids, (ii) multi-stage crystallization of secondary phillipsite, analcime and Al-tobermorite in the vesicles of basaltic pyroclasts and (iii) variations in palagonitization processes as a function of thermal and hydrological domains. Although temperature appears to be an important factor in controlling rates of secondary mineralization, the chemistry of original basaltic components and interstitial fluids also influences reaction pathways in the young pyroclastic deposits. The integration of systematic mineralogical analyses of the 50-year-old tuff from one of the most carefully monitored volcanic sites on Earth, together with temperature monitoring in boreholes since 1980, provide a reference framework for evaluating mineralogical evolution in other Surtseyan-type volcanoes worldwide.
Ссылка для цитирования: Калинина Н.А., Рудмин М.А. Минералого-геохимическая специфика ооидовых железняков гидротермального происхождения // Известия Томского политехнического университета. Инжиниринг георесурсов. – 2023. – Т. 334. – № 2. – С. 111-129. Актуальность. Гипотезы формирования ооидовых железняков остаются дискуссионными на протяжении долгого времени. В рамках данной работы предполагается, что изучение вещественного состава ооидовых железняков из областей с явной фиксируемой или доказанной вулканической и гидротемальной активностью позволит понять природу ооидовых железняков. Цель: изучение минерального и химического состава ооидовых железняков гидротермального месторождения Вани (о. Милос, Кикладский архипелаг) для оценки влияния гидротермальных растворов на особенности их вещественного состава. Методика исследования включала оптическую микроскопию (петрографический анализ), рентгенофлуоресцентный анализ, сканирующую электронную микроскопию с локальным рентгеноспектральным энергодисперсионным анализом, рентгенодифракционный анализ, просвечивающую электронную микроскопию и масс-спектрометрию с индуктивно связанной плазмой. В результате исследования были определены текстурно-структурные особенности и получена минералого-геохимическая характеристика ооидовых железняков из гидротермального марганцевого месторождения Вани (Греция). Выводы. На основе полученных данных в изучаемом разрезе месторождения Вани (Греция) выделены породы трех литотипов, различающихся текстурно-структурными и минералогическими характеристиками: два хемогенных (оксидные марганцевые породы, ооидовые железные руды) и один вулканогенно-обломочный (глауконитовый песчаник). Судя по геолого-структурному положению и геохимическим особенностям, предполагается, что основным источником металлов для железняков являются гидротермальные растворы. Двухактное внедрение гидротермальных растворов в толщу песчаников способствовало формированию железистых минералов в две стадии, которые различаются примесными элементами. Ооидовые железняки обогащены редкоземельными элементами, относительно остальных литотипов, что обусловлено высокой сорбционной способностью гидроокислов железа (гетита и лепидокрокита) в условиях осаждения металлов. Основная масса редких земель концентрируется в минеральных формах (арсенатах), представленных включениями в кортексе ооидов. Источники редкоземельных элементов – гидротермальные растворы и денудированные толщи вулканического аппарата.
Data collected by orbiters and landers have consistently shown abundant amorphous materials on Mars. Developing analytical techniques that target amorphous materials in terrestrial analogs can help determine the environmental conditions under which the amorphous assemblages on Mars were formed. However, the inherent short-range order, chemical heterogeneity, and nanoscale phase interactions create challenges in characterizing these phases. This study is aimed to overcome these challenges by combining chemical dissolution rate analysis with spectroscopy-based mass balance calculations (MBC) to characterize different pools of amorphous materials in terrestrial analogs. The differences in dissolution rates between rapidly dissolving Si, Al, and Fe amorphous materials and the slowly dissolving crystalline minerals were modeled to predict amorphous composition in five palagonitic samples from Hawaii (Mauna Kea) and four hyaloclastite tuffs from the subglacial volcanoes in southwest Iceland. These samples were selected as potential analogs because of their spectral and compositional resemblance to Mars's surface materials.
The amorphous Si, Al, and Fe compositions from both sites varied based on the degree of aqueous alteration, grain size, and location. The amorphous fractions of the unconsolidated palagonitic analogs from Hawaii are composed of alteration products such as opal CT and ferrihydrite with minor amounts of unaltered basaltic glass. In contrast, the amorphous fractions of the cemented Icelandic samples were composed mainly of unaltered glass and mixed Fe(II, III) iron phases. Amorphous compositions of the loose Hawaiian and the consolidated Icelandic palagonites are comparable with the Martian modern and ancient aeolian materials respectively. The amorphous compositions in the Hawaiian sample, HWMK101, closely resemble the amorphous materials in Rocknest, a modern aeolian material from the sand shadow, and the Icelandic samples are comparable to the ancient aeolian materials from the Stimson formation. Our analysis indicates the presence of hydrated secondary alteration products such as ferrihydrite and allophane in Rocknest, and a mixture of reduced iron phases and silicate glass outlined with finer altered opaline silicates in Greenhorn. The chemical extraction analysis combined with MBC can be used to characterize amorphous phases in terrestrial analogs to better constrain the formation and characterization of the abundant amorphous materials on Mars.
X-ray Diffractometry is a very useful analytical technique to achieve detailed information about the crystal structure and mineralogical composition, qualitative and quantitative, of matter. It is a technique that exploits the interaction between solid matter and X-rays that, converged on a substance, are diffracted. The outgoing X-rays, on the basis of the wavelength of the incident beam and according to the path within the analyzed sample provide information on fundamental parameters of the crystalline state as the distance of the lattice planes and the parameters of the elementary cell. The analytical result is called diffraction pattern containing a series of peaks that show the intensity and angular position of the diffracted X-rays. Typically, a diffraction pattern represents, for individual minerals, a kind of distinct fingerprint and can be used to easily identify the material or distinguish it from others, especially with the use of modern databases. X-Ray Diffractometry can be successfully used in a variety of fields: building materials, geological samples, environmental pollutants and increasingly by forensic sciences as a scientific aid for the analysis of evidence from crime scenes.
Lime mud in northern Belize lagoon is composed predominantly of silt-size cryptocrystalline grains and clay-size clumps, both of which consist of anhedral, equant crystals less than 0.5 μm in size. This mud is 70-90% Mg-calcite containing 9-10 mole % MgCO 3. Detailed petrographic, morphologic and mineralogic analyses suggest that the cryptocrystalline grains are micritized skeletal grains and that the mud formed by abrasion and bioerosion of these altered grains. The abundance of cryptocrystalline grains in the Bahamas and other shallow carbonate environments suggests that micritized grains are potentially an important source of lime mud that has not previously been identified. -from Authors
Results are given of an assessment of a Rietveld-type X-ray powder diffraction pattern fitting structure refinement technique for assaying powdered mixtures as an alternative to conventional discrete peak empirical methods of the type described by Klug and Alexander (1974) and Chung (1974). The values obtained for a mixture of corundum and α-quartz, following calibration of the instrument with a profile of the former, indicate that this technique has excellent potential as an analytical tool.
High-resolution synchrotron-radiation powder data for quartz and Mg2GeO4, an olivine homologue, were obtained with a 365 mm long parallel-slit collimator with 0.05° aperture. The crystal structures were refined using a pseudo-Voigt profile fitting function and POWLS. Fourier maps were calculated from the measured structure factors of the germanate. The results for quartz were in good agreement with single-crystal data and R(Bragg) increased from 1.35 to 2.20% as the number of reflections included in the refinement increased from 46 to 119; the e.s.d.'s of the positional parameters were 4 to 8 × 10−4. The germanate gave R(Bragg) 4.85% using 77 Miller planes and the e.s.d.'s were 4 to 42 × 10−4. Special attention was given to the profile fitting function and the non-random particle distributions. The JCPDS Diffraction File Nos. will be reported in a later communication.
Quantitative phase analysis of multicomponent mixtures using X-ray powder diffraction data has been approached with a modified version of the Rietveld computer program of Wiles & Young [J. Appl. Cryst. (1981), 14, 149–151]. This new method does not require measurement of calibration data nor the use of an internal standard; however, the approximate crystal structure of each phase of interest in a mixture is necessary. The use of an internal standard will allow the determination of total amorphous phase content in a mixture. Analysis of synthetic mixtures yielded high-precision results, with errors generally less than 1.0% absolute. Since this technique fits the complete diffraction pattern, it is less susceptible to primary extinction effects and minor amounts of preferred orientation. Additional benefits of this technique over traditional quantitative analysis methods include the determination of precise cell parameters and approximate chemical compositions, and the potential for the correction of preferred orientation and microabsorption effects.
In spite of the wide availability of automated diffractometers and advanced data reduction software, numerous traditional problems still exist that make highly precise and accurate quantitative analyses of complex mixtures difficult. The problems include particle statistics, primary extinction, microabsorption, preferred orientation, overlapping and broad reflections, variation in standard data with composition, availability of pure standards, and detection of amorphous and trace phases. Our analyses of rocks use the matrix flushing method on < 5μm particle-size material mixed with a 1.0-μm corundum internal standard to minimize the first four effects. Integrated intensities are used, and we employ several peaks from each phase whenever possible. We overcame overlap problems through iterative calculations using integral, multiple peaks or with profile refinement. Use of observed and calculated diffraction patterns for every phase enables us to predict the effects of composition and preferred orientation on RIRs. This allows us to correct for these effects if reference intensity ratios (RIRs) are known as a function of composition and orientation. Detection of amorphous phases is a significant problem, and standard mixtures reveal that amounts of amorphous components below 30% are difficult to detect. The poor detection limit and the nature of the diffraction band from amorphous phases make internal standard or spiking methods the best approach for analyzing samples containing amorphous materials. The Rietveld method of quantitative analysis has the potential to minimize all of the above problems. This method requires a knowledge of the crystal structures of all component crystalline phases, but no calibration data are necessary, structural and cell parameters can be varied during the refinement process, so that compositional effects can be accommodated and precise cell parameters can be obtained for every phase. Since this method fits the entire diffraction pattern and explicitly uses all reflections from every phase, complex, overlapped patterns can be easily analysed. In addition, this method presents the opportunity to correct for preferred orientation and microabsorption during data analysis.
La méthode de détermination du degré d'ordre-désordre Ai/Si d'un feldspath alcalin proposé en 1969 par Stewart et Ribbe est testée dans cette étude. Dans ce but les dimensions précises de la maille de feldspaths de structure bien connue et celles des échantillons utilisés pour les expériences d'échanges des cation, d'effets thermiques et de la thermochimie ont été employées. Toutes les hypothèses de base du modèle Stewart-Ribbe ont été confirmées. De légères modifications sont toutefois nécessaires pour les paramètres des mailles d'albite de B. T. et de sanidine H. T.
Les graphiques représentant la variation de b en fonction de c et celle de α* en fonction de γ* sont révisés. Ces diagrammes ont été utilisés pour caractériser la distribution des atomes de Al et Si dans les mailles de 98 feldspaths alcalins. La plupart d'entre eux ont été utilisés dans les études précédentes mais leurs dimensions de maille ont été de nouveau déterminées. Le graphique représentant la variation de b en fonction de c indique également l'influence de a sur cette variation. Cette influence a été établie par les données de beaucoup de feldspaths homogènes. L'indice de contrainte ∆a est défini comme a[obs] – a[est] où a[est] désigne la valeur de a estimée à partir des données de b et c en utilisant le graphique b-c.
Un échantillon de feldspath ayant ∆a > 0,05 Å est considéré « sous contrainte ». Les dimensions de la maille des 138 feldspaths potassiques, compte tenu des nouvelles données de cette étude, ont été utilisées pour relier la distribution des atomes Al et Si et la symétrie de la maille des feldspaths naturels à leur mode de gisement et à leur histoire thermique.
Ces données ont été également utilisées pour discuter les processus d'exsolution des alcalins, le polymorphisme et la progression des contraintes dans les feldspaths naturels.
Une série de données de 139 feldspaths potassiques provenant d'une même région géologique et étudiés par Guidotti, Herd et Tuttle (1973) est interprétée pour obtenir des informations détaillées sur les processus de mise en ordre et de variation de la symétrie entre orthose et microcline.
Les résultats de ces examens permettent de conclure que le « microcline maximal », orthose avec 0,8 ± 0,1 Al dans les sites T₁ et la sanidine B. T. avec 0,58 ± 0,05 Al dans T₁ sont fréquents parce qu'ils se forment dans des conditions thermodynamiques souvent présentes dans la nature et non en raison de la configuration d'ordre préférentiel énergétique des atomes. L'orthose est stable de 750° C jusqu'à moins de 625° C (roches métamorphiques de degrés sillimanite et des plutones de monzonite quartzifère ou d'adamellite) . Elle semble être un produit de cristallisation primaire, parce qu'il n'existe pas de feldspaths plus désordonnés dans ces contextes géologiques. Se basant sur l'hypothèse que le microcline maximal est stable en dessous de 375 ± 50° C et la sanidine B. T. entre 800-900° C, l'équilibre de distribution Ai/Si dans les feldspaths potassiques ne varie pas linéairement avec la température. Ceci est aussi valable pour les feldspaths sodiques. A l'état d'équilibre pour une température donnée de formation, le nombre d'atomes Al dans les sites T₁ pour les feldspaths sodiques est sensiblement le même que pour les feldspaths potassiques. L'équilibre est atteint beaucoup plus rapidement pour les feldspaths sodiques que pour les feldspaths potassiques. Même le refroidissement de quelques milliers de kilomètres cubes de roches métamorphiques n'est pas suffisamment lent pour qu'un feldspaths potassique atteigne l'équilibre de la distribution Al-Si.
Les feldspaths potassiques ayant 95 à 70 % des atomes dans les sites T₁ peuvent apparaître monocliniques ou tricliniques sur les diagrammes de poudre. La structure monoclinique possédant une ondulation orthogonale transversale décrite par McConnell (1971) semble pouvoir accepter 92 % d'atomes d'Al dans les sites T₁. II n'y a jamais de feldspaths potassiques tricliniques contenant moins de 70 % d'atomes Al dans les sites T₁.
Le processus de mise en ordre des feldspaths alcalins monocliniques est continu. C'est une transformation discontinue de l'orthose monoclinique en microcline triclinique qui explique le mieux les assemblages naturels rencontrés. Le changement de symétrie NE SE PRODUIT PAS pour une valeur bien déterminée du nombre d'atomes Al dans les sites T₁. Il existe dans la nature beaucoup de processus pour mettre en ordre la structure des microclines intermédiaires. Il est par conséquent impossible de déduire de ces observations le domaine de stabilité du microcline intermédiaire.
Les feldspaths sous contrainte constituent un tiers des feldspaths étudiés. Ils sont fréquents dans la nature. Ils se trouvent comme constituants des perthites. Bien que les volumes de la maille de chacun des feldspaths coexistant dans une perthite soient compatibles avec leurs compositions respectives, les autres paramètres, longueur de la maille notamment, sont significativement différents de ceux des feldspaths homogènes dans lesquels la teneur (Or + Ab) est supérieure à 95 %. La contrainte dans une phase potassique est maximale lorsqu'elle se trouve dans les perthites de composition globale riche en sodium. Le présent résultat suggère que le degré de contrainte est proportionnel à la teneur globale en Ab de la perthite. Les phases individuelles se manifestent avec plus de contrainte dans les cryptoperthites que dans les microperthites, mais la contrainte maximale possible dans un feldspath est presque indépendante du degré d'ordre-désordre ou de la symétrie de chaque phase. La quantité de contrainte contenue dans un feldspath dépend qualitativement de la taille des lamelles d'exsolution. Plus les lamelles sont minces plus la contrainte contenue dans le cristal sera grande.
La plus forte contrainte est dans la direction du couplage cohérent le plus fort, relation décrite par Willaime et Brown et par d'autres auteurs, ceci explique bien les observations de cette étude.
The structures of two single-crystals of synthetic ilmenite were refined using X-ray intensity data collected at 24, 400, 600, 800 and 1050oC (1 atm) and 0.001, 25.4, 34.6 and 46.1 kbar (room T). The responses of cell parameters, bond lengths, coordination, and ordering to T and P were analysed and found, generally, not to be inverse in character. -J.A.Z.
It is shown that quantitative X-ray powder diffraction analyses using full profile multiphase refinement should include corrections for the Brindley particle absorption contrast effect. This is demonstrated with synthetic mixtures of the highly contrasting phases LiF and Pb(NO3)2 (μ/ρ = 20 and 231 cm−1 for Co Kα). With contrast corrections, the only parameter which needs to be input is an effective particle radius R for each phase. For mixtures of LiF and Pb(NO3)2 over the whole composition range, quantification is achieved, under the present specimen preparation method, with an effective particle radius of 51 μm for both phases, giving analyses correct to within 1 percentage point. Without Brindley corrections, the analysis is grossly in error.
Diffracted intensities from axially symmetric flat-plate or capillary specimens, composed of effectively rod- or disk-shaped crystallites, can be corrected for preferred orientation with a single pole-density profile. A convenient procedure is to approximate this profile with a function whose variable parameters are fit during least-squares structure refinement. Several functions have previously been suggested but without theoretical justification. The present study reviews the derivation of this method and examines its assumptions and applications. The several proposed functions are compared with each other and with the March function which describes the pole-density distribution produced by rigid-body rotation of inequant crystallites (i.e. crystallites with unequal sides) upon axially symmetric volume-conserving compression or expansion. For its basis, ease of use, single variable parameter, direct interpretability and good refinement test results, the March distribution is proposed as an advantageous pole-density profile function for general use.
The application of the Rietveld refinement technique to synchrotron X-ray data collected from a capillary sample of Al2O3 in Debye–Scherrer geometry is described. The data were obtained at the Cornell High Energy Synchrotron Source (CHESS) with an Si(111) double-crystal monochromator and a Ge(111) crystal analyzer. Fits to a number of well resolved individual peaks demonstrate that the peak shapes are very well described by the pseudo-Voigt function, which is a simple approximation to the convolution of Gaussian and Lorentzian functions. The variation of the Gaussian and Lorentzian half widths, ΓG and ΓL, with Bragg angle can be approximated quite closely by the functions V tan θ and X/cos θ which represent the contributions from instrumental resolution and particle-size broadening respectively. Rietveld refinement based on this model yields generally satisfactory results. The refined values of V and X are consistent with the expected vertical divergence (≃0.1 mrad) and the nominal particle size (≃ 0.3μm). In particular, the use of a capillary specimen virtually eliminates preferred orientation effects, which are highly significant in flat-plate samples of this material.
The Rietveld [J. Appl. Cryst. (1969), 2, 65–71] method of structure refinement from powder diffraction patterns is widely used with neutron data and increasingly so with X-ray data. A computer program for the application of the method with X-ray data, or with neutron nuclear scattering data, has been written ab initio in an effort to make it versatile, user oriented, portable, convenient, and largely self-contained yet reasonably comprehensive. It is of modular construction to facilitate user-desired modifications, one of which may be additions to the choice of four profile functions now included. The program accommodates either one or two wavelengths (e.g.α1 and α2 or λ and λ/2). It permits simultaneous refinement of the structures of two phases and the background.
A structure refinement method is described which does not use integrated neutron powder intensities, single or overlapping, but employs directly the profile intensities obtained from step-scanning measurements of the powder diagram. Nuclear as well as magnetic structures can be refined, the latter only when their magnetic unit cell is equal to, or a multiple of, the nuclear cell. The least-squares refinement procedure allows, with a simple code, the introduction of linear or quadratic constraints between the parameters.
All the information relating to the quantitative composition of a mixture is coded and stored in its X-ray diffraction pattern. It has been the goal of X-ray diffraction analysts since the discovery of X-rays to retrieve and decode this information directly from the X-ray diffraction pattern rather than resort to calibration curves or internal standards. This goal appears to be attained by the application of the `matrix-flushing theory' and the now-proposed `adiabatic principle' in applied X-ray diffraction analysis. The matrix-flushing theory offers a simple intensity-concentration equation free from matrix effects which degenerates to `auto-flushing' for binary systems. The adiabatic principle establishes that the intensity–concentration relationship between each and every pair of components in a multi component system is not perturbed by the presence or absence of other components. A key equation is derived which conducts the decoding process. Both the matrix-flushing theory and the adiabatic principle are experimentally verified.
Systematic trends in the geometry of 149 oxide and 80 sulfide binary and ternary spinels have been examined from the standpoint of ionic radius and electronegativity. The mean ionic radii of the octahedral and tetrahedral cations, taken together, account for 96.9 and 90.5% of the variation in the unit cell parameter, a, of the oxides and sulfides, respectively, with the octahedral cation exerting by far the dominant influence in sulfides. The mean electronegativity of the octahedral cation exerts an additional, but small, influence on the cell edge of the sulfides. The equation a=(8/3d)d
tet+(8/3)d
oct, where d
tet and d
oct are the tetrahedral and octahedral bond lengths obained from the sum of the ionic radii, accounts for 96.7 and 83.2% of the variation in a in the oxides and sulfides, respectively, again testifying to the applicability of the hard-sphere ionic model in the case of the spinel structure. Comparison of observed and calculated u values for 94 spinels indicates that up to 40% of the experimentally measured anion coordinates may be significantly in error. In addition to these compounds, u values are given for 52 spinels for which no data have previously been determined. Diagrams are presented for the rapid interpretation of the internal consistency of published data and the prediction of the structural parameters of hypothetical or partially studied spinels.
The weight of a phase in a mixture is proportional to the product of the scale factor, as derived in a multi-component Rietveld analysis of the powder diffraction pattern, with the mass and volume of the unit cell. If all phases are identified and crystalline, the weight fraction W of phase p is given by (Figure presented.) where S, Z, M and V are, respectively, the Rietveld scale factor, the number of formula units per unit cell, the mass of the formula unit and the unit-cell volume. This is the basis of a method providing accurate phase analyses without the need for standards or for laborious experimental calibration procedures. The method is demonstrated by measurements on binary mixtures of rutile, corundum, silicon and quartz.
Quantitative analysis ofgeological materials using X-ray powder diffraction data and the Rietveld refinement method
- D L Bish
- J E Post
Bish, D.L., and Post, J.E. (1988) Quantitative analysis ofgeological materials using X-ray powder diffraction data and the Rietveld refinement
method. Geological Society of America Abstracts with Programs, 20,
4223.
Crystal structures of clay minerals I t' --i , I t Il and their X-ray identifrcation
- G W Brindley
Brindley, G.W. (1980) Quantitative X-ray mineral analysis of clays. In
G W. Brindley and G. Brown, Eds, Crystal structures of clay minerals
I t' --i
, I
t
Il
and their X-ray identifrcation, p. 4ll-438. Mineralogical Society,
bndon.
Modal analyses ofthe granite and diabase test rocks
- F Chayes
Chayes, F. (1951) Modal analyses ofthe granite and diabase test rocks.
U.S. Geological Survey Bulletin, 980, 59-68.
Lattice constants of the calcium-magnesium carbonates
- J R Goldsmith
- D L Gral
- H C Heard
Goldsmith, J.R., Gral D.L., and Heard, H.C. (1961) Lattice constants of
the calcium-magnesium carbonates. American Mineralogist, 46, 453-457.
About analytical models for texture correction
- M Jarvinen
Jarvinen, M. (1992) About analytical models for texture correction. Proceedings ofAccuracy in Powder Diffraction, 2, 34.
Quantitative analysis
- R L Snyder
- D L Bish
Snyder, R.L., and Bish, D.L. (1989) Quantitative analysis. In Mineralogicaf Society of America Reviews in Mineralogy, 20, l0l-144.