Scanning Electron Microscope Cathodoluminescence Research Articles

Fluid overprints and mineralization of the Zhuguangshan granite-related U district in China: Recorded by cathodoluminescence textures and chemistry of quartz

Most high-grade U ores are mined from quartz veins hosted in granites. The veins formed at shallow depths during episodic hydrothermal activity, however, the evolution of multiple stage fluids is not well constrained. In this study, we collected 56 quartz samples from the world-class, granite-related, Zhuguangshan U district (>17,000 t U from seven deposits) in southern China. Their textures and compositions were analyzed using scanning electron microscope cathodoluminescence (SEM-CL, n = 98) and laser ablation-induction coupled plasma-mass spectrometry (LA–ICP–MS, n = 643). Four types of quartz were identified, including magmatic quartz, early hydrothermal euhedral quartz, ore stage hydrothermal quartz (U-rich), and late hydrothermal quartz. New quartz textures and chemical compositions show that the transition of early hydrothermal quartz from the magmatic to hydrothermal stages is discontinuous, unlike the continuous trend observed in most magmatic-hydrothermal systems. Ore stage quartz is CL dark (with a peak at 650 nm), occurs as rims on early barren quartz, and has high contents of Mn, Al, and Sb. Altered textures of magmatic quartz developed through fluid-rock reactions at low temperatures, while rimmed textures of hydrothermal quartz formed during subsequent late-stage U-bearing fluid events, which played a crucial role in U mineralization. Quartz in the Zhuguangshan U district has distinct features compared to other magmatic-hydrothermal systems that can guide exploration for high-grade ore in this, and perhaps other, granite-related U systems.

Genesis and fluid evolution of the Hatu orogenic gold deposit in the West Junggar, Western China

The West Junggar in Xinjiang, western China, represents a significant gold mineralization belt hosting over 200 gold deposits, with the Hatu gold deposit being the largest among them. In this study, ore geology and fluid inclusion assemblages of quartz samples from the Hatu gold deposit were investigated in an effort to clarify the mineralization process and its relationship with the geodynamic settings. The mineralization process is delineated into early (pyrite-albite-quartz veins), middle-a (quartz-ankerite veins), middle-b (quartz-ankerite-sulfide-native gold veins), and late (quartz-calcite veins) stages. The early stage veins suggest a compressional setting while the middle-a and middle-b stage veins suggest a tensional shear setting. The late stage veins are typically filled fissures cutting through earlier veins. Scanning electron microscope-cathodoluminescence (SEM-CL) reveals that early stage quartz (Q1) exhibits concentric CL-oscillatory growth zoning, while middle-a stage quartz (Q2a) displays unidirectional zoning and ranges from CL-bright to CL-dark, middle-b stage quartz (Q2b) is CL-bright and weakly zoned, and late-stage euhedral quartz (Q3) shows sector zoning transitioning from CL-gray to CL-dark. Quartz that formed in these stages developed three types of fluid inclusions: pure CO2 (PC-type), CO2–H2O (C-type), and H2O–NaCl (W-type). The early stage quartz contains C- and W-type fluid inclusions homogenizing at 309–345 °C, while the late stage quartz contains only W-type fluid inclusions with homogenization temperatures of 164–229 °C. Microthermometry of fluid inclusion indicated the evolutionary of the metallogenic fluid from a high-temperature, CO2-rich, and minor CH4 metamorphic fluid to a low-temperature, CO2-poor meteoric fluid. From the early to middle-a stages, fluid boiling caused the unloading of ore-forming elements whereas fluid mixing led to the precipitation of polymetallic sulfides and gold in the middle-b stage. Trapping pressures in the middle-b stage were estimated using C-type inclusions, illustrating that gold mineralization took placed at depth of 8.0 km. We propose classifying the Hatu gold deposit as an orogenic deposit, originating from the collisional orogenesis between the Yili-Kazakhstan and Siberian continents in the Late Carboniferous.

Provenance Analysis and Diagenesis Using Integrated SEM-Cathodoluminescence and Optical Microscopy for the Sandstones of the Pirispiki Formation, Kurdistan Region, Northern Iraq

The paragenetic history and provenance of framework grains in marginal marine and deltaic sandstones of the Pirispiki Formation in two sections, (Ora and Kaista), northern Iraq were examined. This was achieved using an integrated approach employing scanning electron microscopy-cathodoluminescence (SEM-CL), and optical microscopy. The Pirispiki Formation is lithologically characterized by alternating layers of thin- and thick-bedded sandstones. These were intercalated with thin laminae of grey-black shale. Petrographic analysis revealed that the dominant detrital grains in the mature quartz arenite sandstone were monocrystalline quartz grains with undulose extinction. The diagenetic analysis of the sandstones documented several processes that occur in three distinct stages. The SEM-CL technique enabled the identification of two distinct quartz overgrowth phases. Quartz cementations are of two types, the earliest phase and the most significant by volume is the Q1 cement characterized by dark non-luminescence which led to the destruction of most of the primary pores and the healing of mechanically induced cracks. Q2 cement is formed after major compaction and is characterized by bright luminescence with sector zoning, revealing an intricate SEM-CL zonation. CL revealed five special textures within detrital quartz grains including healed fractures and zoning. The provenance of the detrital quartz grains indicated the dominance of plutonic and metamorphic sources, with trace amounts originating from volcanic sources. These were mostly derived from the Bitlis Massif Zone in Turkey.

Genesis of the Nuri Cu‐W‐Mo Deposit, Tibet, China: Constraints from in situ Trace Elements and Sr Isotopic Analysis of Scheelite

AbstractThe Nuri deposit is the only Cu‐W‐Mo polymetallic deposit with large‐scale WO3 resources in the eastern section of the Gangdese metallogenic belt, Tibet, China. However, the genetic type of this deposit has been controversial since its discovery. Based on a study of the geological characteristics of the deposit, this study presents mineralization stages, focusing on the oxide stage and the quartz‐sulfide stage where scheelite is mainly formed, referred to as Sch‐A and Sch‐B, respectively. Through LA‐ICP‐MS trace element and Sr isotope analyses, the origin, evolutionary process of the ore‐forming fluid and genesis of the ore deposit are investigated. Scanning Electron Microscope‐Cathodoluminescence (SEM‐CL) observations reveal that Sch‐A consists of three generations, with dark gray homogenous Sch‐A1 being replaced by relatively lighter and homogeneous Sch‐A2 and Sch‐A3, with Sch‐A2 displaying a gray CL image color with vague and uneven growth bands and Sch‐A3 has a light gray CL image color with hardly any growth band. In contrast, Sch‐B exhibits a ‘core‐rim’ structure, with the core part (Sch‐B1) being dark gray and displaying a uniform growth band, while the rim part (Sch‐B2) is light gray and homogeneous. The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore‐forming fluid in the Nuri deposit originated from granodiorite porphyry and, later on, some country rock material was mixed in, due to strong water‐rock interaction. Combining the O‐H isotope data further indicates that the ore‐forming fluid in the Nuri deposit originated from magmatic‐hydrothermal sources, with contributions from metamorphic water caused by water‐rock interaction during the mineralization process, as well as later meteoric water. The intense water‐rock interaction likely played a crucial role in the precipitation of scheelite, leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz‐sulfide stage, while also causing a gradual decrease in oxygen fugacity (fO2) and a slow rise in pH value. Additionally, the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic‐hydrothermal scheelite. Therefore, considering the geological features of the deposit, the geochemical characteristics of scheelite and the O‐H isotope data published previously, it can be concluded that the genesis of the Nuri deposit belongs to porphyry‐skarn deposit.

3D structure of threading screw dislocation at a deep location in 4H-SiC using 3D micro-X-ray topography

We used 3D micro-X-ray topography (3D μ-XRT) to construct a 3D structure of the threading screw dislocations (TSDs) in 4H-SiC. The 00012 diffraction condition, which can observe the strain field at a deep location in the sample, was employed in the 3D μ-XRT geometry. The dislocation core-lines of TSDs propagating from the surface to the interior of the sample were successfully captured spatially, and TSDs parallel to and inclined from the 〈0001〉 axis were both confirmed. Either the component 〈〉 or 〈〉 of the Burgers vector is considered to be mixed in the inclined TSD. To verify this suggestion, scanning electron microscopy (SEM) and cathodoluminescence (CL) spectroscopy were performed on the molten-alkali-etched TSDs. Both the SEM shapes and CL intensities of the TSD etch pits with inclination showed the features of the mixed component, supporting the correlation between the inclination and mixed component in TSD.

Asian dust-deposition flux to the subarctic Pacific estimated using single quartz particles

Iron availability limits marine ecosystem activities in large areas of the ocean. However, the sources and seasonal supply of iron, critically important for controlling surface ocean biogeochemistry and carbon cycling, are poorly understood. The western subarctic Pacific is a high-nutrient and low-chlorophyll region, and despite high concentrations of macronutrients, iron limits phytoplankton production in summer. Here, we determine the seasonal deposition flux of Asian dust using scanning electron microscope–cathodoluminescence analysis of single quartz particles derived from the western subarctic Pacific during 2003–2022 to trace provenance. We found a high (up to 6.9 mg m−2 day−1) deposition flux of Asian dust in May, June, and early July, with an annual average of 1.0 ± 0.2 mg m−2 day−1. The supply of dissolved-iron flux calculated from Asian dust was 0.9 ± 0.3 µg m−2 day−1 during the high productivity season (April–July), which is approximately half that from the deeper part of the ocean, calculated from vertical profiles of dissolved iron. Our study provides a reliable approach for estimating iron supply from dust to the surface ocean that may be critical for sustaining biological productivity under future ocean stratification, which suppresses nutrient supply from the subsurface ocean.

Role of nanoscale compositional inhomogeneities in limiting the open circuit voltage in Cu(In,Ga)S2 solar cells

As Si-based solar cell technologies approach their theoretical efficiency limits, alternative photovoltaic systems, such as tandem solar cells, are gathering increased attention due to their potential to reach higher efficiencies by better use of the solar spectrum. Cu(In,Ga)S2 (CIGS) is a promising material for the top cell due to its large, tunable bandgap energy (Eg), stability, and already established high efficiencies. However, the deficit in open circuit voltage is still large; therefore, an improved understanding of the efficiency losses is required. Scanning electron microscopy cathodoluminescence was used to study the role of the polycrystalline nature for radiative recombination in CIGS samples of varying Cu-content. Considerable differences between neighboring grains were observed in the emission energy and the emission intensity, with significant drops in emission energy at the grain boundaries. Lateral homogeneity in the near band edge (NBE) energy was found to reduce for samples with Cu-poor compositions, with its standard deviation halving (σNBE ∼ 20 meV) compared to the more stoichiometric films (σNBE ∼ 50 meV), which corresponds to an open circuit voltage loss contribution that is nearly an order of magnitude lower. Such inhomogeneities can be attributed mainly to local variations of the Ga concentration. Hence, the differences between the samples could be explained by the different deposition times at elevated temperature allowing for different extents of homogeneity. Thus, Cu-poor films are not only favorable because of lower concentrations of deep defects but also because of reduced bandgap variations.

Cathodoluminescence as a tracing technique for quartz precipitation in low velocity shear experiments

Two simulated gouges (a pure quartz and a quartz-muscovite mixture) were experimentally deformed in a ring shear apparatus at a constant low velocity under hydrothermal conditions favourable for dissolution–precipitation processes. Microstructural analysis using scanning electron microscope cathodoluminescence imaging and cathodoluminescence spectroscopy combined with chemical analysis showed that quartz dissolution and precipitation occurred in both experiments. The starting materials and deformation conditions were chosen so that dissolution–precipitation microstructures could be unambiguously identified from their cathodoluminescence signal. Precipitated quartz was observed as blue luminescent fracture fills and overgrowths with increased Al content relative to the original quartz. In the pure quartz gouge, most of the shear deformation was localized on a boundary-parallel slip surface. Sealing of fractures in a pulverized zone directly adjacent to the slip surface may have helped keeping the deformation localized. In the quartz-muscovite mixture, some evidence was observed of shear-accommodating precipitation of quartz in strain shadows, but predominantly in fractures, elongating the original grains. Precipitation of quartz in fractures implies that the length scale of diffusive mass transfer in frictional-viscous flow is shorter than the length of the quartz domains. Additionally, fracturing might play a more important role than generally assumed. Our results show that cathodoluminescence, especially combined with chemical analysis, is a powerful tool in microstructural analyses of experimentally deformed quartz-bearing material and visualizing quartz precipitation.

Nanoscale Cathodoluminescence and Conductive Mode Scanning Electron Microscopy of van der Waals Heterostructures.

van der Waals heterostructures (vdW-HSs) integrate dissimilar materials to form complex devices. These rely on the manipulation of charges at multiple interfaces. However, at present, submicrometer variations in strain, doping, or electrical breakages may exist undetected within a device, adversely affecting macroscale performance. Here, we use conductive mode and cathodoluminescence scanning electron microscopy (CM-SEM and SEM-CL) to investigate these phenomena. As a model system, we use a monolayer WSe2 (1L-WSe2) encapsulated in hexagonal boron nitride (hBN). CM-SEM allows for quantification of the flow of electrons during the SEM measurements. During electron irradiation at 5 keV, up to 70% of beam electrons are deposited into the vdW-HS and can subsequently migrate to the 1L-WSe2. This accumulation of charge leads to dynamic doping of 1L-WSe2, reducing its CL efficiency by up to 30% over 30 s. By providing a path for excess electrons to leave the sample, near full restoration of the initial CL signal can be achieved. These results indicate that the trapping of charges in vdW-HSs during electron irradiation must be considered, in order to obtain and maintain optimal performance of vdW-HS devices during processes such as e-beam lithography or SEM. Thus, CM-SEM and SEM-CL form a toolkit through which nanoscale characterization of vdW-HS devices can be performed, allowing electrical and optical properties to be correlated.

Vein Formation and Reopening in a Cooling Yet Intermittently Pressurized Hydrothermal System: The Single-Intrusion Tongchang Porphyry Cu Deposit

Porphyry deposits are the dominant sources of copper and major sources of several base and precious metals. They are commonly formed via the repeated emplacement of hydrous magmas and associated fluid exsolution. As a result, mineralized hydrothermal veins may undergo multiple deposition and reopening processes that are not fully accounted for by existing fluid models. The Tongchang porphyry Cu deposit is a rare example of being related to a single intrusion. The simplicity in intrusive history provides an ideal starting point for studying fluid processes in more complex multi-intrusion porphyry systems. Detailed scanning electron microscope (SEM) cathodoluminescence imaging (CL) revealed rich microtextures in quartz and anhydrite that point to a fluid timeline encompassing early quartz deposition followed by fluid-aided dynamic recrystallization, which was succeeded by an intermediate stage of quartz dissolution and subsequent deposition, and ended with a late stage of continuous quartz deposition, brecciation, and fracturing. Vein reopening is more common than expected. Fifteen out of seventeen examined vein samples contained quartz and/or anhydrite that was older or younger than the vein age defined by vein sequences. Thermobarometry and solubility analysis suggests that the fluid events occurred in a general cooling path (from 650 °C to 250 °C), interspersed with two episodes of fluid pressurization. The first episode occurred at high-T (>500 °C), under lithostatic conditions alongside dynamic recrystallization, whereas the second one took place at a lower temperature (~400 °C), under lithostatic to hydrostatic transition conditions. The main episode of chalcopyrite veining took place subsequent to the second overpressure episode at temperatures of 380–300 °C. The results of this study reaffirm that thermal and hydraulic conditions are the main causative factors for vein reopening and growth in porphyry deposits.

3D Perovskite Passivation with a Benzotriazole-Based 2D Interlayer for High-Efficiency Solar Cells.

2H-Benzotriazol-2-ylethylammonium bromide and iodide and its difluorinated derivatives are synthesized and employed as interlayers for passivation of formamidinium lead triiodide (FAPbI3) solar cells. In combination with PbI2 and PbBr2, these benzotriazole derivatives form two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) as evidenced by their crystal structures and thin film characteristics. When used to passivate n-i-p FAPbI3 solar cells, the power conversion efficiency improves from 20% to close to 22% by enhancing the open-circuit voltage. Quasi-Fermi level splitting experiments and scanning electron microscopy cathodoluminescence hyperspectral imaging reveal that passivation provides a reduced nonradiative recombination at the interface between the perovskite and hole transport layer. Photoluminescence spectroscopy, angle-resolved grazing-incidence wide-angle X-ray scattering, and depth profiling X-ray photoelectron spectroscopy studies of the 2D/three-dimensional (3D) interface between the benzotriazole RPP and FAPbI3 show that a nonuniform layer of 2D perovskites is enough to passivate defects, enhance charge extraction, and decrease nonradiative recombination.

Dolomite cement microstratigraphy: A record of brine evolution and ore precipitation mechanisms, upper Knox Group, Tennessee and Kentucky, USA

AbstractTrace element changes in fluids associated with ore-forming events in sedimentary basins may be recorded by contemporaneous cements, especially zoned carbonate minerals (microstratigraphy). Cement analysis using advanced mapping and analytical techniques including scanning electron microscopy cathodoluminescence (SEM-CL), charge contrast imaging, high-resolution X-ray computed tomography (XCT), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) documents geochemical changes associated with Mississippi Valley–type mineralization in solution-collapse breccias of the Cambrian–Ordovician Knox Group (Tennessee and Kentucky, USA). Dolomite cement zonation coincident with changes in Fe and Mn can be observed with optical microscope CL in bands as narrow as 5 µm, whereas panchromatic SEM-CL reveals microfractures and cement subzones coincident with changes in La and Ce concentrations in bands as narrow as 0.1 µm. XCT scans image a high-density (Fe-rich) dolomite zone at the onset of late sulfide precipitation. The transition from pre-ore to ore-stage cementation is marked by increased Fe, Mn, Zn, Cd, Ga, Pb, and Sr and decreased La and Ce concentrations. Fine-scale metal depletion cycles during this transition may record metal precipitation from brine in response to the availability of reduced sulfur. Except for Fe and Mn, post-ore dolomite zones generally have low metal concentrations. Thus, dolomite microstratigraphy tracks systematic changes in brine metal concentrations modified by episodes of localized sulfide mineral precipitation.

High resolution imaging of ultrafine bubbles in water by Atmospheric SEM-CL

Various analytical methods such as high-resolution observation of ultrafine bubbles in water are required to clarify the mechanisms and interrelationships of various effects brought about by ultrafine bubbles. In this study, we used atmospheric scanning electron microscopy-cathodoluminescence (ASEM-CL) method for observing ultrafine bubbles in water. ASEM can observe samples in water, and the fine electron beam provides high spatial resolution. Furthermore, the gas in the bubble can be estimated from the CL emission spectrum. We have measured characteristics such as bubble size and particle number density. Also, the CL spectra has shown that the ultrafine bubbles contained nitrogen.

Scanning Electron Microscopy-Cathodoluminescence Imaging of Industrial Steelmaking Slag for Identifying and Determining the Free Magnesia Content

Scanning Electron Microscopy-Cathodoluminescence Imaging of Industrial Steelmaking Slag for Identifying and Determining the Free Magnesia Content

Development of Tourmaline-Bearing Lithologies of the Peraluminous Tusaquillas Composite Granitic Batholith, NW Argentina: Evidence from Quartz and Tourmaline

ABSTRACT Textural and chemical characteristics of quartz and tourmaline found in tourmaline-rich orbicules, greisens, pegmatites, and tourmalinite segregations associated with the peraluminous leucogranitic Tusaquillas Batholith Complex of northwest Argentina exhibit both magmatic and hydrothermal features. Imaging of quartz by optical cathodoluminescence and scanning electron microscopy cathodoluminescence shows three stages of development. Stage-1 quartz, considered magmatic, develops as large grains in pegmatites that have optical cathodoluminescence homogeneity; as anhedral relict grains partially replaced by stage-2 hydrothermal quartz in tourmalinite segregations, orbicules, and greisens; and as idiomorphic grains with irregularly spaced oscillatory zoning seen in scanning electron microscopy cathodoluminescence in orbicules. Stage-2 quartz, interpreted as hydrothermal, partially replaces stage-1 quartz and generation-1 tourmaline in most lithologies. Stage-3 quartz, a late hydrothermal stage, occurs in all lithologies as weakly luminescing quartz in healed quartz fractures with abundant fluid inclusions, commonly associated with the crystallization of irregular late-stage tourmaline. Multiple generations of tourmaline span magmatic to hydrothermal phases of development. In all lithologies, generation-1 tourmaline is compositionally similar: highly aluminous (range of average values of Altotal = 6.31–6.95 apfu), markedly Fe- and X□-rich (XMg = 0.01–0.17, X□= 0.21–0.51), and having variable F and WO (F = 0.00–0.57 apfu, WO = 0.00–0.40). Generation-1 tourmaline is interpreted as magmatic with compositions reflecting the chemical environment of the host lithologies and with compositional zoning patterns characteristic of both closed- and open-system behavior, possibly related to the transition to subsolidus conditions. Similar to generation-1 tourmaline, later-stage generations-2 and -3 tourmaline compositions are highly aluminous (range of average values of Altotal = 6.38–6.79 apfu), markedly Fe- and X□-rich (XMg = 0.00–0.20, X□= 0.28–0.40), and variably F- and WO-enriched (F = 0.07–0.57 apfu, WO = 0.00–0.31), but notably poorer in Ca and Ti (<0.01 apfu). The later-stage tourmaline is considered to have developed during the subsolidus hydrothermal conditions. External chemical contributions to tourmaline compositions from the country rocks appear to be minor to nonexistent. The X-site and W-site occupancies of the late-generation tourmaline implies subsolidus invasive alkaline, saline aqueous fluids with high Na but minimal Ca contents derived from the crystallizing leucogranites and related rocks across the solidus-to-subsolidus transition.

Trace Element Composition and Cathodoluminescence of Quartz in the Hongniu–Hongshan Skarn Deposit in Yunnan Province, Southwest China

The Hongniu–Hongshan Cu skarn deposit is located in the central part of the Zhongdian porphyry and skarn Cu belt in southwestern China. Various elements, including Al, Ti, Li, K, Na, Ca, Fe, and Ge, have been completed by using scanning electron microscopy–cathodoluminescence (SEM-CL) and laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) on quartz phenocrysts from the Hongniu–Hongshan porphyry and skarn Cu deposit. Three quartz generations were identified in the porphyritic granite based on the CL textures and trace element signatures. Samples of the first-generation quartz (Qtz1) contain dark gray luminescent cores assaying 22–85 ppm Ti, 58–129 ppm Al, 4–18 ppm Li, and 0.43–40 ppm Fe. The Ti-in quartz geothermometer indicates crystallization temperatures of 593–664°C for Qtz1. Samples of the second-generation quartz (Qtz2) are characterized by clear bright gray oscillatory overgrowths with medium Ti concentrations of 51–70 ppm with elevated and variable amounts of Al, Li, and Fe, and low K. The Ti-in quartz geothermometer indicates crystallization temperatures of 672–706°C. Samples of the third-generation quartz (Qtz3) contain narrow light gray rims assaying 56–93 ppm Ti, 80–101 ppm Al, 11–19 ppm Li, 1.42–17 ppm K, and 2–25 ppm Fe. The Qtz3 crystallised crystallized at higher temperatures of 706–799°C. Our study indicates that the quartz phenocryst in the Hongniu–Hongshan porphyry may have undergone two mixing episodes involving a second hotter magma. Before the first resorption, average Ti concentration in the quartz phenocryst cores was 24 ppm, and Ti of the bright band halo at the edge of the crystal core is 56 ppm; the maximum temperature difference is 109°C higher than that of the pre-resorption. Furthermore, the Ti concentration is 75 ppm at the edge of the quartz phenocryst before resorption. After resorption, the average Ti increased to 81 ppm at maximum temperature difference of 54°C higher than that of pre-resorption. Moreover, on the basis of quartz composition collected from 14 different deposits and our new dataset, we propose that covariations of Ge/Al ratio can be used to effectively discriminate magmatic quartz and hydrothermal quartz. Magmatic quartz has a Ge/Al ratio of <0.013, and the hydrothermal quartz has a ratio of >0.013.

Role of Eu2+ and Dy3+ Concentration in the Persistent Luminescence of Sr2MgSi2O7 Glass-Ceramics.

In this study, glass-ceramics based on Sr2MgSi2O7 phosphor co-doped with Eu/Dy were obtained from the sintering and crystallisation of glass powders. The glasses were melted in a gas furnace to simulate an industrial process, and the dopant concentration was varied to optimise the luminescence persistence times. The doped parent glasses showed red emission under UV light excitation due to the doping of Eu3+ ions, while the corresponding glass-ceramics showed persistent blue emission corresponding to the presence of Eu2+ in the crystalline environment. The dopant concentration had a strong impact on the sintering/crystallisation kinetics affecting the final glass-ceramic microstructure. The microstructures and morphology of the crystals responsible for the blue emission were observed by scanning electron microscopy–cathodoluminescence. The composition of the crystallised phases and the distribution of rare-earth (RE) ions in the crystals and in the residual glassy phase were determined by X-ray diffraction and energy dispersive X-ray analysis. The emission and persistence of phosphorescence were studied by photoluminescence.

Temperature and basinal fluid controls on feldspar diagenesis, Lower Cretaceous sandstones, Scotian Basin, Canada

The passive-margin Scotian Basin accumulated thick Upper Jurassic–Lower Cretaceous deltaic sandstones and shales, which were influenced by high heat flow in the mid-Cretaceous and deformed by salt tectonics. This study takes advantage of the complex thermal history and record of saline fluid flow in the basin to determine the relative importance of burial depth, temperature, salinity of basinal brines, overpressure, and sandstone permeability in controlling the dissolution of detrital feldspar and growth of authigenic K-feldspar and albite. Feldspar grains and volcanic lithic clasts from two transects, with differing thermal and salt tectonic histories, were studied by scanning electron microscope (SEM) backscattered electron images, energy-dispersive spectroscopy, SEM cathodoluminescence (CL) imaging, and hot-cathode CL microscopy. Published fluid inclusion measurements are integrated with burial history curves and timing of deformation on salt detachment surfaces to provides a new synthesis of the post-Jurassic thermal and saline fluid flow history of the basin. Surface-controlled dissolution of K-feldspar and growth of authigenic K-feldspar rims occur from 1.5 to 3.1 km. More destructive transport-controlled dissolution, down to 3.9 km, is more effective in thick-bedded permeable sandstones that acted as fluid pathways. Albitization of detrital K-feldspar and sodic plagioclase, and of feldspars in volcanic lithic clasts was facilitated by high Na+ content of formation waters migrating preferentially through such pathways at the time of silica and carbonate cementation, with strong albitization coinciding with transport-controlled dissolution of K-feldspar. Authigenic albite partially fills pores created by K-feldspar dissolution. Overpressured conditions enhance albite authigenesis, as a result of slower fluid advection. Episodic release of hot, saline, overpressured fluids in the zone of surface-controlled dissolution of K-feldspar favoured albitization but had no detectable effect on K-feldspar dissolution. Basin hydrology plays a definitive role in feldspar diagenesis, producing patterns that cannot be interpreted as a simple consequence of temperature and activity of Na+.

Provenance of quartz grains from soils over Quaternary terraces along the Guadalquivir River, Spain

The characterisation of quartz grains’ chemical and mineralogical properties in sediments and sedimentary rocks is widely used in provenance studies. This paper analyses quartz grains from the coarse sand fraction in soils in Quaternary fluvial terraces (Guadalquivir River, southern Spain). The tentative soil ages are 0.3 ka (Haplic Fluvisol), 7 ka (Haplic Calcisol), 70 ka (Cutanic Luvisol), 300 ka (Lixic Calcisol) and 600 ka (Cutanic Luvisol). The quartz grains analyses shed light on the sedimentological history of these terraces. Scanning electron microscope cathodoluminescence (SEM-CL) characteristics, micro inclusion inventory established by Energy-dispersive X-ray spectroscopy (SEM-EDX) and trace element contents determined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of quartz grains permitted distinguishing six types of grains in the soils studied: metamorphic quartz (type 1), undeformed granitic quartz (type 2), strongly altered granitic quartz (type 3), recrystallised (deformed) granitic quartz (type 4), sandstone-derived quartz (type 5) and hydrothermal quartz grains (type 6).Metamorphic quartz grains (type 1) come from the Sierra Morena (Iberian Massif) and Sierra Nevada (Internal Betic Zone). Granitic quartz grains (types 2 to 4) come from Los Pedroches batholith and its associated plutons (Santa Elena and Linares). The sandstone-derived quartz type 5 comes from the numerous sandstone outcrops scattered in the central catchment area of the Guadalquivir River. Finally, hydrothermal quartz grains (type 6) originate from hydrothermal veins associated with subvolcanic rocks of the Los Pedroches batholith.Variations were noted in the proportions of quartz types in soils of different ages, attributed to spatial and temporal changes in the catchment area. The most remarkable change occurred between 500 and 240 ka ago when the catchment area extended into Sierra Nevadás metamorphic rocks, well reflected in type 1 content (lower in P2, P4, P5 and PM) and their characteristics (quartz with less healed fractures, less Al content, bigger mica microinclusions, smaller Al/Ti ratio) in the post-500–240 ka soils.Our study shows that the combined study of SEM-CL characteristics, micro inclusions (SEM-EDX), and trace element contents (LA-ICP-MS) of quartz grains is an efficient approach for characterising the provenance of quartz grains in the sand fraction of soils.

Geochemical and fluid evidences for fluorine-rich magmatic-hydrothermal origin of the giant Chalukou Mo deposit in the northeast China

The Chalukou deposit is a world-class porphyry Mo deposit in the Great Hingan Range, northeast China. Fluorites were analyzed by scanning electron microscope-cathodoluminescence (SEM-CL), microthermometry, and laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS) to characterize the composition and temperature of mineralizing fluids. There are four types of veins in Chalukou deposit that can be categorised as A vein (quartz–fluorite–magnetite–K-feldspar vein), B vein (quartz–fluorite–molybdenite vein), D vein (quartz–fluorite–sphalerite–galena–pyrite vein) and post-mineralization vein. The CL images of fluorites are characterized by heterogeneous texture in A vein, but homogeneous texture in B and D veins. Fluorites in A vein have total rare earth elements (REE) contents of 10–4963 ppm and temperatures of 370–410 °C, which show similar geochemical features with ore-bearing porphyry. In contrast, fluorites in B and D veins exhibit total REE contents of 4.6–41.3 ppm and temperatures between 257 and 300 °C, showing the decreasing trends of total REE contents and temperatures from early to late stage. Fluid inclusions of four types of veins are composed of one-phase, two-phase and daughter mineral-bearing multiphase with decreasing trend of temperatures from 450 °C to 120 °C and salinities from 53.0% to 0.7 wt% NaCl equiv. during the evolution. It is proposed that high-fluorine fugacity has a considerable influence on metal solubility and migration in the early stage of the Chalukou deposit. Temperature decreasing and fluid mixing may be the key factors of metal precipitation during the Mo mineralization stage, but the effect of fluorine is not obvious.