Cathodoluminescence Data Research Articles

Diverse dolomitization models in the Aptian Dariyan (Shu'aiba) Formation in the Persian Gulf, Iran: Evidence from petrography, geochemistry and impact on reservoir quality

This study investigates dolomitization as one of the key diagenetic processes influencing the reservoir quality of the Dariyan Formation (Aptian) in three oil/gas fields in the Persian Gulf. To achieve this goal, petrographic studies of core samples and thin-sections are integrated with cathodoluminescence microscopy, carbon and oxygen isotopic analyses, and fluid inclusion studies. The formation exhibits two main dolomitization models, including hydrothermal-related saddle dolomites and stylolite-associated dolomites, as well as two minor models including bacterial activity-related dolomites and mixed meteoric and marine waters. Hydrothermal dolomitization, associated with deep burial diagenesis, results in saddle dolomites filling fractures and voids, characterized by high-temperature and salinity formation conditions. Stylolite-related dolomitization occurs in mud-dominated facies, as fine to medium crystals with a cloudy center and a clear rim, concentrated along the solution seams and stylolites. Bacterial activity-related dolomitization is distinguished in Lithocodium–algal facies, highlighting the role of microbial mediation in dolomite formation at low temperatures. Mixed-water dolomitization is observed in grain-dominated shoal and lagoonal facies, where the interaction of meteoric and marine waters leads dolomite cementation. Geochemical (δ13C and δ18O) and cathodoluminescence data support the diagenetic model, indicating varying stages and conditions of dolomite formation. Fluid inclusion analyses of saddle and stylolite-related dolomites reveal salinity (9.5 wt% NaCl equiv.) and temperature (105 °C) conditions consistent with burial diagenesis. The paragenetic sequence shows a diagenetic history encompassing marine, meteoric, and burial environments. Marine diagenesis includes early (microbial and mixing type) dolomitization, bioturbation, micritization and isopachous cementation, while meteoric diagenesis comprises dissolution, cementation and recrystallization during prolonged (>1 Myr) exposure at the end of Aptian. Burial diagenesis involves compaction, hydrothermal and stylolite-related dolomitization, cementation, and recrystallization, critically controlling reservoir quality. This study demonstrates that dolomitization significantly enhances permeability, with the highest reservoir quality found in dolomitized facies of the lower carbonate unit of the Dariyan Formation. This study highlights the complexity of diagenetic processes in the Dariyan Formation, providing valuable insights into the factors controlling its reservoir quality. The findings emphasize the importance of integrated geological and geochemical approaches for accurate reservoir evaluation and prediction in dolomitized carbonate formations.

Probing densified silica glass structure by molecular oxygen and E’ center formation under electron irradiation

This study aims to learn more about the structure of densified silica with focus on the metamict-like silica phase (density = 2.26 g/cm3) by examining the formation of E’ point defects and interstitial molecular oxygen O2 by 2.5 MeV electron irradiation. High-dose (11 GGy) irradiation creates a metamict-like phase and a large amount of interstitial O2, which is destroyed upon subsequent additional lower-dose electron irradiation. The O2 cathodoluminescence (CL) data indicate that the formation of O2 from peroxy linkages Si–O–O–Si in silica network is strongly dependent on the intertetrahedral void sizes. The position and shape of the O2 emission line support the idea that the configuration of these voids in metamict phase is close to that of non-densified silica. Moreover, data support the strong correlation between the formation of 3-membered rings of Si–O bonds and E’-centers when silica density increases from 2.20 to 2.26 g/cm3.

Study of the Sensor Properties of Ordered ZnO Nanorod Arrays for the Detection of UV Radiation

Zinc oxide is one of the most promising materials used to create devices in the ultraviolet (UV) range. In this article, we study the sensor properties of ordered ZnO nanorod arrays grown by chemical vapor deposition. The possibility of their use as an indicator of UV radiation to control the dose of UV radiation, both from natural and artificial light sources, is assessed. The X-ray diffraction, Raman spectroscopy (RS), and cathodoluminescence (CL) data demonstrate the high quality of nanorods. Based on the ZnO nanorod array, a sensor prototype was fabricated based on the change in ZnO conductivity under the UV irradiation. A compari-son of the response of such a sensor with the readings of a UV radiometer showed a high correlation.

Deconvolution of Light-Induced Ion Migration Phenomena by Statistical Analysis of Cathodoluminescence in Lead Halide-Based Perovskites.

Studying the compositional instability of mixed ion perovskites under light illumination is important to understand the mechanisms underlying their efficiency and stability. However, current techniques are limited in resolution and are unable to deconvolute minor ion migration phenomena. Here, a method that enables ion migration to be studied allowing different segregation mechanisms to be elucidated is described. Statistical analysis is applied to cathodoluminescence data to generate compositional distribution histograms. Using these histograms, two different ion migration phenomena, horizontal ion migration (HIM) and vertical ion migration (VIM), are identified in different perovskite films. It is found that most passivating agents inhibit HIM, but not VIM. However, VIM can be reduced by deposition of imidazolium iodide on the perovskite surface. This method can be used to study perovskite‐based devices efficiency and stability by providing molecular level mechanistic understanding of passivation approaches leading to performance improvement of perovskite solar cells via rational design.

Synthesis and luminescence properties of Eu2+/Ce3+, Ce3+/Tb3+ and Eu2+/Tb3+ co-doped AlONs

Series of Eu2+/Ce3+, Ce3+/Tb3+ and Eu2+/Tb3+ co-doped aluminum oxynitrides Al5O6N were prepared using the standard sol-gel technique with following annealing in the flow of N2. In all the samples Al5O6N is a major phase, just traces of α-Al2O3 and AlN were found for some particular samples with high loading of rare-earth ions. According to pulsed cathodoluminescence and photoluminescence data a non-radiative energy transfer occurs from Ce3+ to Eu2+, from Ce3+ to Tb3+ and from Eu2+ to Tb3+. Also, it was shown that for Eu2+/Ce3+ co-doped Al5O6N the optimal contents of both REE ions are different compared to those for single doped Al5O6N (0.25 at% of Eu2+ and 0.04 at% of Ce3+). In case of Al5O6N:0.4%Tb3+,yCe3+ (y = 0.01…0.08%) the PCL and PL intensities increase in the whole range of Ce3+ content. Finally, for Al5O6N:0.4%Tb3+,yEu2+ (y = 0.1…0.8%) no pronounced dependence of luminescence caused by Tb3+ ions on the Eu2+ content is observed. Concentration quenching of Eu2+ caused luminescence is given at Eu2+ content above 0.3%. The chromaticity coordinates of prepared co-doped AlONs were calculated and three samples were found to give close to white emission.

The Origin of Quartz Cement in the Upper Triassic Second Member of the Xujiahe Formation Sandstones, Western Sichuan Basin, China

High-precision in situ δ18O values obtained using secondary ion mass spectrometry (SIMS) for μm-size quartz cement are applied to constrain the origin of the silica in the deep-buried Upper Triassic second member of Xujiahe Formation tight sandstones, western Sichuan Basin, China. Petrographic, cathodoluminescence (CL), and fluid inclusion data from the quartz cements in the Xu2 sandstones indicate three distinct, separate quartz precipitation phases (referred to as Q1, Q2, and Q3). The Q1 quartz cement was formed at temperatures of approximately 56–85 °C and attained the highest δ18O values (ranging from 18.3 to 19.05‰ Vienna Standard Mean Ocean Water (VSMOW)). The Q2 quartz cement was generated at temperatures of approximately 90–125 °C, accompanying the main phase of hydrocarbon fluid inclusions, with the highest Al2O3 content and high δ18O values (ranging from 15 to 17.99‰ VSMOW). The Q3 quartz cement was formed at temperatures of approximately 130–175 °C, with the lowest δ18O values (ranging from 12.79 to 15.47‰ VSMOW). A portion of the Q2 and Q3 quartz cement has a relatively high K2O content. The dissolution of feldspar and volcanic rock fragments was likely the most important source of silica for the Q1 quartz cement. The variations in δ18O(water) and trace element composition from the Q2 quartz cement to the Q3 quartz cement suggest that hydrocarbon emplacement and water-rock interactions greatly altered the chemistry of the pore fluid. Feldspar dissolution by organic acids, clay mineral reactions (illitization and chloritization of smectite), and pressure dissolution were the main sources of silica for the Q2 and Q3 quartz cements, while transformation of the clay minerals in the external shale unit was a limited silica source.

Coloration changes in natural ruby induced by oxygen ion implants correlated with cathodoluminescence data

Ruby is a mineral in the corundum (Al2O3) family and it is remarkably valuable as a gemstone. From the physics point of view, the ruby coloration depends on the balance of trace or chromophore impurities and defect complexes in the Al2O3 lattice. Shifting this balance into right direction is of paramount importance for the ruby value as the gemstone and ion implantation can be applied for this purpose. Thus, in the present study, we explored the influence of high dose oxygen ion implants on the natural ruby coloration. By performing quantitative colorimetry analysis, we detected prominent coloration changes unambiguously attributed to the effect of the implants, even though the implanted oxygen profile was located at the near surface region of the sample. Moreover, applying near surface sensitive cathodoluminescence measurements we observed spectacular changes in the spectra correlated with the implants. Importantly, the trends observed in the colorimetry and cathodoluminescence as a function of the implantation parameters were consistent. As such, the present paper provides both the scientific perspective and quantitative interpretations potentially paving the way for the ion beams applications in the gemstone industry.

Thick AlN Templates By MOCVD for the Thermal Management of III-N Electronics

Ultra-wide bandgap semiconductors have attracted much interest over the last decade. These materials have strong chemical bonding that led to high temperature tolerance, high voltage and power handling capabilities as described by the Baliga figure of merit. Al-rich III-nitride materials are expected to have the best performance over the industry standard Si, and newer options such as SiC and GaN. Continuous improvements dictate the miniaturization of electronic devices, leading to increasingly higher power densities in smaller footprints, leading to heating that causes system failure. Thus, the thermal management is the limiting task for continuous performance scaling. In past we have reported on deep ultraviolet light emitting diodes (LEDs) and AlxGa1-xN (x>0.4) channel Heterojunction Field-Effect Transistors (HFETs) on 2-3 µm thick MOCVD grown high quality AlN/sapphire templates. For template thicknesses over 5 µm either sapphire or AlN patterning is needed to avoid stress related cracking. In this research, we for the first-time report on the direct MOCVD growth and characterization of crack-free, low-impurity AlN templates in excess of 16 μm on basal plane sapphire substrates without doing any external processing. Increasing the thickness improves thermal management and enables an easier sapphire substrate’s laser liftoff for increased DUV light extraction. It would also be used as a heat spreader in power electronics to minimize the operating temperature to maximize power output to industrial loads such as electric vehicles, and large turbines in manufacturing and transportation.All growths were carried out in custom MOCVD reactors with a fast-metalorganic switching manifold using a modified epitaxy procedure in which the Al- and N-precursors (Trimethyl Aluminum and NH3) are pulsed for increased surface mobility. At the initial pulsed growth stage, the growth-temperature and precursor-flow rates are adjusted to yield air-pocketed (voids) rough AlN layers. Most of these high defect materials are located near the AlN/sapphire interface. As the AlN thickness increases in the subsequent growths, the layers turned out smooth and the number of defects is significantly reduced due to dislocation bending/annihilation and cracking is avoided due to strain relief from the voids at the interface. All template growths were carried out at temperatures ~ 1200 - 1300 °C and 40 torr.From X-ray diffraction (XRD), Reciprocal space map (RSM), and Transmission Electron Microscopy (TEM) analysis of these thick AlN templates, we established that they were fully relaxed. Cross-section TEM data clearly shows the presence of voids at ~ 0.4 – 0.9 μm from the AlN/sapphire interface. There is a high density of dislocations present near the void region. Above this region, at least one order of magnitude lower dislocations is observed at the AlN smooth layer region. From the room-temperature Cathodoluminescence (CL) data we see an increase in the band edge emission and a decrease in the defect related long-wavelength signal with increasing AlN template thicknesses. The CL spectra were measured in the edge emission pump geometry on cleaved bars due to the transverse-magnetic polarized nature of the band-edge emission. The monochromatic CL imaging data also confirmed a highly defective region at the AlN/sapphire interface which is also the origin of the long wavelength (below bandgap) CL emission. The Atomic Force Microscopy (AFM) surface scans of the templates showed the surface roughness ~ 0.15 nm to 0.25 nm (for a 5 µm x 5 µm scan). The (102) off axis X-ray linewidths for all these samples ranged from 280 to 330 arc-secs. XRD and Raman experiments confirmed a residual compressive strain in AlN templates compared to the bulk sample. The measured stress ranges from -0.6 GPa to -1.2 GPa for all the templates, reasonable agreement with previous reports. We have found no obvious thickness dependence of the stresses measured from both XRD and Raman, an indication of preserving similar stresses in thick and thin templates.The thermal conductivity of our high-quality 16 µm thick template and the bulk AlN are measured at different temperatures by Time-domain Thermoreflectance (TDTR) technique. The thermal conductivity of the thick AlN at room temperature is 320 Wm-1K-1, or ~10% higher than that of the bulk AlN (~285 W/m-K). At low temperatures (120 K), it exceeds that of bulk AlN by more than 40%. In summary, these templates showed thermal conductivity as high or better than high-cost bulk AlN substrates, demonstrating for the first time that sapphire-based power electronics could be effectively managed thermally. Figure 1

Mineralogy composition and texture indicative of fluid-assisted remobilization in carbonate units of the Irecê Basin, Brazil

Carbonates of the Salitre Formation, Irecê Basin, Brazil, have been the focus of extensive stratigraphic and structural studies for several decades. Besides hosting phosphorites deposits, these rocks are analogues to fractured and certified oil reservoirs, such as those of the Cretaceous pre-salt oil system offshore Brazil. The present study presents an integration of X-Ray Diffraction (XRD), Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMScan), Optical Petrography, Cathodoluminescence (CL), and Charge Contrast Imaging (CCI) data that allows a high-resolution characterization of the mineralogy within the carbonate units. In addition, we also present carbon and oxygen stable isotope data to identify possible origins of the associated fluids. The mineral characterization revealed that calcite (50–70%), quartz (20–30%) and dolomite (10–20%) are the main post-sedimentary mineral phases found in veins, vesicle structures and cement of the carbonate units. The mineral phases of veins were formed by the interaction with hydrothermal fluids, which had an important role in the dissolution, karstification, and remobilization of carbonate units. Isotopic analysis shows that δ13C and δ18O are more negative in veins and vesicles when compared to host rock, indicating that there is no effective isotopic exchange between the host rock and the filled structures and that these structures were filled with hydrothermal fluids from an external source.

Vibrational and luminescent properties of polycrystalline zircon: Effect of structural and impurity defects

Zircon was synthesized by the sol-gel route and subjected to sequential heat treatment. X-ray powder diffraction showed that single-phase zircon was obtained. The impurity content and microstructure of the obtained ceramic were studied by the mass spectrometry and scanning electron microscopy. The contents of Hf ~0.8 ​wt% and Al ~0.2 ​wt% are prevailing, while the presence of other impurity elements does not exceed 0.06 ​wt%. The photo- and cathodoluminescence data indicate the presence of structural and impurity defects. The instability of structural defects during high-temperature annealing was observed. The average value FWHM of the Raman B1g(4) band of asymmetric stretching vibrations of SiO4 tetrahedra lies in the range 2.55–3.15 ​cm-1, which slightly exceeds the minimum value ~1.8–2.0 cm-1 in the spectra of perfect single crystals. The zircon synthesized can be used as a reference sample for spectroscopic studies in mineralogy.

Impact of dopant-induced optoelectronic tails on open-circuit voltage in arsenic-doped Cd(Se)Te solar cells

Fluctuations refer to inhomogeneity in the distribution of donors and acceptors at the nanometer scale and occur in many compound solar cell materials such as Cu(In,Ga)Se2, Cu2ZnSn(S,Se)4, and CdSexTe1−x. In this work, numerical simulations show that these fluctuations produce not only electrostatic potential variation, but also, local changes in the carrier density and effective bandgap. For a CdSexTe1−x absorber doped with arsenic, simulations and cathodoluminescence data within single grains demonstrate how donor and acceptor densities—consistent with capacitance-voltage and secondary-ion mass-spectrometry data—produce tails in photoluminescence, quantum efficiency, and absorption measurements. Using multiple theoretical approaches, we demonstrate that the fluctuations can hinder expected performance gains from increased carrier density, and we describe the significant open-circuit voltage deficit observed in the CdSexTe1−x:As solar technology. Our results demonstrate that it is critical to characterize and reduce carrier compensation to realize a higher efficiency.

Optimum Carbon Concentration in GaN-on-Silicon for Breakdown Enhancement in AlGaN/GaN HEMTs

This article reports on the experimental and analytical determination of the optimum carbon concentration in GaN to achieve enhanced breakdown in AlGaN/GaN high-electron mobility transistors (HEMTs). The lateral breakdown voltage increases when carbon doping is increased from $3\times 10^{{18}}$ to 1019 cm−3 beyond which it decreases, whereas there is no substantial enhancement in the vertical breakdown voltage with carbon doping. We invoke carrier statistics in a compensated semiconductor vis-a-vis the formation energy of carbon-occupying Ga (or N) vacancies to explain the observed buffer leakage. Temperature-dependent data indicate that the buffer leakage current is due to hopping transport, the activation energy of which yields the positions of the defect states within the bandgap. The increase in buffer leakage beyond optimum C concentration is attributed to the formation of shallow donor traps by carbon atoms occupying Ga vacancies (CGa). The observations correlated with the relative intensities of the defect-mediated peaks in the cathodoluminescence (CL) data of the samples. Based on our findings, a C doping beyond 1019 cm−3 is not recommended for GaN buffers in order to achieve high breakdown voltages.

Effect of Sintering Temperature on the Characteristics of Zn0.99Li0.01O Thin Film on Si Substrate

Lithium-doped zinc oxide (Zn0.99Li0.01O) film was manufactured by the sol-gel method using uniform and stable solution of zinc acetate dehydrate and lithium acetate dehydrate in methanol. Films were deposited by spin-coating using spinner between 4500 and 5000 rpm on silicon substrates. The prepared samples were sintered at various temperatures (600 oC ~ 1000 oC) in the air. The structural, morphological, and optical properties of the prepared lithium-doped ZnO films were investigated. The XRD pattern of Zn0.99Li0.01O film demonstrated the hexagonal wurzite structure. However, new crystal phase was discovered at a sintering temperature of 800 oC. New peak was found near 2θ = 22.6o in XRD patterns. The peak is thought to be the (101) plan in SiO2 cristobalite structure. Moreover, another new crystal phase related to Li2SiO5 was occurred at a sintering temperature of 900 oC. From XRD analysis, it was confirmed that C axis was decreased and the stress was increased, as sintering temperatures was increased from 600 oC to 900 oC. In cathodo luminescence (CL) data, zinc oxide usually appears ultra violet and green emission. However, the green emission did not appear in all these samples used in this study. The ultra violet emission showed red shift from 600 oC to 800 oC in the CL spectrum as the sintering temperature was increased. The phenomenon of the red shift can be explained in Burstein-Moss effect. At sintering temperature of 700 oC, the intensity of ultra-violet emission was the largest and full width at half maximum (FWHM) was the smallest.

Paleohydrogeologic reconstruction of Triassic carbonate paleolakes from stable isotopes: Encompassing two lacustrine models

Reconciling interpretations of geochemical, sedimentologic, and stratigraphic observations is a common challenge with many datasets, especially those from paleolake systems. The Triassic Cerro de las Cabras and Cerro Puntudo formations, part of the sedimentary fill of the Cuyana rift Basin in central-west Argentina, represent carbonate-rich playa-lake systems with abundant microbialites, but different sedimentologic and stratigraphic attributes such as presence or absence of efflorescent crystalline crusts and aggrading versus prograding-aggrading stacking patterns. A detailed study of the stable-carbon and oxygen-isotope composition of the limestones deposited in these paleolakes, together with sedimentological and mineralogical evidence as petrography, microprobe, XRD and cathodoluminescence data, enabled interpretation of their complex hydrology.Lack of correlation between carbon and oxygen stable-isotope values for both Cerro de las Cabras (δ13C χ–6.03‰; σ 0.67‰/δ18O χ −12.64‰; σ 0.55‰) and Cerro Puntudo (δ13C χ −3.10‰; σ 1.15‰/δ18O χ −12.58‰; σ 1.8‰) paleolakes strongly indicates open hydrology (underground flow), in apparent contradiction with sedimentologic and stratigraphic evidence for intermittent to persistently closed hydrography (overland flow). Stable-isotopic values for the Cerro de las Cabras paleolake together with sedimentology data indicate a recharge (hydrologically open) lake, and for the Cerro Puntudo a through-flow (hydrologically open) playa-lake. To resolve the apparent contradictions, we propose an integration of playa-lake hydrology (groundwater) with lake-basin type sedimentology, stratigraphy, and hydrography. This allowed identifying and proposing a balanced-fill–through-flow lake subtype for the Cerro Puntudo system and an underfilled–recharge-lake subtype for the Cerro de las Cabras paleolake; both with hydrology open to groundwater flow. This work suggests a starting point for expanding the lake-basin-type model to explicitly incorporate different groundwater and overland flow pathways.

EBSD and CL Study of Deformed Quartz Grains in Rocks: An Example for one Strain Fringe Structure From Iron Quadrangle.

Kinematic indicators, including certain strain fringes, represent an important group of structures related to the progressive deformation in rocks. The evolution of these fibrous textures can be explained by the combination of multiple mechanisms of deformation and fluid flow, mainly controlled by the orientation of the strain field and the morphology of the grains. In general, the observations are done with an optical microscope and compared with computational models of growth. This work proposes a combination of crystallographic and cathodoluminescence data obtained in rocks from banded iron formations of the Iron Quadrangle in Brazil to represent an example of how complementary analytical techniques can be useful to understand geological problems. The chosen sample exhibits a strain fringe structure of quartz around a clast of magnetite partially transformed into goethite and hematite. Through the crystallographic data it was possible to identify the grain boundary morphology and domains of low deformation areas. On the other hand, the cathodoluminescence signal evidenced the occurrence of grains with a higher concentration of crystalline defects.

Analysis of the Optical Properties of Plastically Deformed ZnS(O) Using Band-Anticrossing Theory

The cathodoluminescence and absorption of plastically deformed ZnS(O) single crystals are investigated in the light of band-anticrossing theory. The difference in the oxygen content in the surface layer and in the sample bulk is found using a scanning electron microscope and according to cathodoluminescence data. This fact explains the specifics of the spectral position of the fundamental absorption edge and exciton spectra. The shift dynamics of the bands of self-activated luminescence on deep A centers (SA luminescence) during deformation recrystallization with an increase in the dissolved oxygen concentration is presented. Restriction of the spectral range of the appearance of self-activated luminescence at shallow levels—“edge” luminescence—is established. The nature of the emission bands in the wavelength ranges of 336–350 and 364–390 nm is established. These results refine the energy model of ZnS(O) crystals and can be useful in the case of the practical use of their structure-sensitive properties.

Structure and fracture-cavity identification of epimetamorphic volcanic-sedimentary rock basement reservoir: a case study from central Hailar Basin, China

Taking the epimetamorphic volcanic-sedimentary complex basement in Beier Depression, Hailar Basin, China, as an example, the lithology, diagenesis, reservoir characteristics, and vertical zoning structure division are studied by using core, thin sections, cathodoluminescence, SEM, LSCM, well logging, FMI, diplog, and 3D seismic data. The reservoirs including fractures and cavities are identified and predicted separately under the control of vertical zoning structure, by well logging response, seismic reflection features, and multiseismic attributes. The results show that the assemblage of fine siltstone, tuffaceous sandstone, and tuff is the best lithology assemblage for reservoir development. The basement reservoir structure is divided into four zones, and zone II developing both fractures and pores has the best reservoir quality, followed by zone III having fractures dominated. Fracture and pore-cavity reservoirs have decreasing resistivity, density, and other features in conventional well log, and pore-cavity reservoirs have relatively high amplitude and bead or lenticular-shaped seismic reflection. The seismic attributes of curvature, coherence, and amplitude extracted under the control of specific zonation are effective reservoir prediction methods. Reservoir distribution including fracture and pore-cavity is controlled by the palaeogeomorphology of basement buried hill and fault activity and property. For the buried hills with high palaeogeomorphology and long-term structural activity controlled by main faults, developing high-quality reservoirs of fractures as well as pores, are the optimal targets for basement drilling, in the condition of effective hydrocarbon migration path.

Towards understanding phosphorus distribution in coal: A case study from the Bowen Basin

In coal, phosphorus can occur in a variety of minerals but apatite Ca5(PO4)3 (OH, F, Cl) is the most common. This mineral is often observed within the cell-lumens (<20 microns) of inertinite macerals, although fracture-infilling apatite has been reported. Its size and main occurrence within the cell lumens makes it difficult to liberate the apatite by current coal beneficiation strategies. It also reduces porosity and clogs flow paths for gas drainage. Present-day mineral distributions reflect the origins and geological history of the coal and fluids moving through it. Therefore, understanding the geological controls of these distributions within the coal seams can help in prediction and developing mitigation strategies. Interrogation of spatial litho- and bulk chemical-data sets within Permian coals at a single deposit affected by igneous intrusions, faults and seam splits was undertaken. Preliminary results in the study-area show elevated phosphorus contents are common in the roof and floor of the parent coal seam. However, these elevated contents transgress lithotypes, up-dip along the flanks of an anticline that is also proximal to a fault, a dyke and a rider seam split. The findings from this work provided the framework for samples selection for detailed microanalysis. Initial electron probe results show multiple phosphate minerals including: apatite and crandallite [CaAl3(PO4)(PO3OH)OH6]. There are at least two mode of occurrence of the apatite minerals: cell-lumen- and fracture-infilling, with the former most common. The cell-infilling apatite is thought to reflect either syngenetic or epigenetic mineralisation; while the fracture-infilling apatite formed later, post coalification. This is interpreted to have formed via fluids migrating through permeable and porous pathways created during geological deformation. Preliminary infrared spectroscopy results show the fracture-infilling apatite is relatively crystalline and lacking a hydroxyl peak which could reflect fluoridation. Preliminary cathodoluminescence data show this fracture-infilling apatite, as well as those in the pores, appears to be an epigenetic mineral phase that potentially formed from a single-phase fluid. The spatial distribution of bulk chemical data suggests a spatial dependence between elevated phosphorus contents and post- or syn-depositional features. However, a conclusive relationship between mode of occurrence, apatite chemistry and proximity to depositional and post-depositional features has not yet been found. Therefore, alternative analytical methods to discriminate between phosphorus-bearing minerals formed from such processes are proposed.

Cathodoluminescence, fluid inclusions, and trace element data for the syntaxial quartz cementation in the sandstones of the Ora Formation, northern Iraq

Quartz cements of the quartz arenitic sandstones from the Chalky Nasara and Ora sections of the (Devonian-Carboniferous) Ora Formation in northern Iraq have been studied. A combination of hot cathodoluminescence, LA-ICP-MS, and fluid inclusion microthermometry revealed three syntaxial quartz cement generations (Q1, Q2, and Q3). The early Q1 cementation has gray to slightly brown luminescences, postdated compaction, and reduced intergranular porosity associated with illite formed during eogenesis. Q2 is characterized by dark brown luminescence overgrowths and is more voluminous in the thinly bedded sandstones than in the thickly bedded sandstones filling most of the remaining pore space during mesogenesis. Q3 was formed during the early telogenesis stage fully cementing the sandstones and the fractures were filled by hydrothermal chlorite and sulfides. Significant amounts of trace elements Al, Li, Ge, and Fe have been detected in quartz overgrowths. Al varies consistently between each cement with averages of 7125, 4044, and 2036 ppm for the Q1, Q2, and Q3 generations, respectively. A strong linear correlation between Al and Li in the three quartz cements with an average Li/Al of ~0.02 in Q1 and Q2 indicates sufficient availability of both Al and Li where Li is most likely to be found in high-saline pore waters. Illite is the most probable origin of Li since high salinities favor the mobilization of Li during diagenesis. Germanium concentrations in quartz cements are slightly less than that in the detrital quartz of the Ora Formation, indicating that the pressure dissolutions of quartz and feldspar are the dominant sources of cementation in the Ora Formation. Homogenization temperatures of fluid inclusions indicate precipitation of the Q1, Q2, and Q3 cement generations at temperature ranges of 155-160 °C, 160-166 °C, and 168-178 °C, respectively, with salinities ranging between 5.0 and 6.4 wt.% NaCl equiv., as an indication of hydrothermal burial conditions for Q3 cement, which was affected by the major Zagros Thrust Zone faulting.

Color electron microprobe cathodoluminescence of Bishunpur meteorite compared with the traditional optical microscopy method

Abstract Cathodoluminescence (CL) imaging is an outstanding method for sub classification of Unequilibrated Ordinary Chondrites (UOC) - petrological type 3. CL can be obtained by several electron beam apparatuses. The traditional method uses an electron gun coupled to an optical microscope (OM). Although many scanning electron microscopes (SEM) and electron microprobes (EPMA) have been equipped with a cathodoluminescence, this technique was not fully explored. Images obtained by the two methods differ due to a different kind of signal acquisition. While in the CL-OM optical photography true colors are obtained, in the CL-EPMA the results are grayscale monochromatic electronic signals. L-RGB filters were used in the CL-EPMA analysis in order to obtain color data. The aim of this work is to compare cathodoluminescence data obtained from both techniques, optical microscope and electron microprobe, on the Bishunpur meteorite classified as LL 3.1 chondrite. The present study allows concluding that 20 KeV and 7 nA is the best analytical condition at EPMA in order to test the equivalence between CL-EPMA and CL-OM colour results. Moreover, the color index revealed to be a method for aiding the study of the thermal metamorphism, but it is not definitive for the meteorite classification.