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1.
《Chemical Geology》1999,153(1-4):81-91
Cathodoluminescence (CL) investigations of igneous, metamorphic and sedimentary feldspars indicate that rare earth elements (REE)-activated CL in feldspars is more common than previously assumed. Hot-cathode CL microscopy combined with high-resolution spectrometric analysis of CL emission allow to detect some REE below the detection limits of electron microprobe and proton-induced X-ray emission analysis (PIXE) and reveal variations in the REE distribution within single feldspar crystals. Differently luminescing zones can reflect changes during feldspar crystallization and/or element fluctuations during secondary alteration processes which are not discernible using conventional polarizing microscopy. The results of the study document Eu2+, Sm3+, Dy3+, Tb3+, and Nd3+-activated CL in feldspars of different origin. The influence of the crystal field on shape and position of REE luminescence spectra significantly differs for divalent and trivalent REE ions. Whereas Eu2+ shows a broad band emission (∼420 nm) which is influenced by the local crystal field, trivalent ions of the rare earth show narrow emission lines which reflect the transitions between excited state wave functions lying inside closed electronic shells. The positions of these peaks and the characteristic energies are described for the different REE3+.  相似文献   

2.
For the first time, the luminescence properties of Pr3+, Nd3+ and Tm3+ and Yb3+ ions in fluorite crystal have been obtained by steady-state measurements. In addition, the luminescence spectra of Ce3+, Sm2+, Sm3+, Dy3+, Er3+ and Yb3+ were measured. It was pointed out that λexc.?=?415?nm is most suitable for measuring the Ho3+ emission beside the Er3+. The emission of trivalent holmium and erbium ions was measured independently using time-resolved measurements and tentative assignment of luminescence lines to C 3v and C 4v symmetry sites was proposed. Besides for natural fluorite crystal, the transitions between Stark energy levels of lanthanide ions were presented.  相似文献   

3.
The photoluminescence properties of synthetic zircon, ZrSiO4, doped with REE3+ (REE = Pr, Sm, Eu, Gd, Dy, Ho, Er) were investigated using combined excitation and emission spectroscopy. All samples showed luminescence characteristics of intra-ion energy transitions, similar to other lanthanide-doped materials. However, the relative intensities were dependent on the energy of excitation and the presence of charge-transfer bands were inferred from excitation spectra. From the data, we conclude that the lanthanides in zircon occur in more than one type of coordination. Energy transfer between different lanthanides was observed in some co-doped samples and emissions that were unassigned in previous studies have been assigned to specific lanthanides based on excitation spectroscopy.  相似文献   

4.
Summary This work examines the red luminescence of benitoite studied by laser-induced time-resolved luminescence spectroscopy. This method allows the differentiation between luminescence centers of similar emission wavelengths, but different decay times. We have also examined the luminescence intensity and decay time as a function of temperature. We found that the red emission of benitoite consists of two individual bands and one line and suggest that the activators of luminescence in benitoite system are Ti3+ and a d3 element, namely Cr3+ or Mn4+.  相似文献   

5.
The accumulation of structural damage that is created in minerals upon corpuscular irradiation, has two apparently contrarious effects on their luminescence behaviour. First, irradiation may cause the generation of luminescent defect centres, which typically results in broad-band emissions. Such defect emissions are characteristic of low levels of radiation damage. Second, radiation damage depletes in general the luminescence of minerals, which is associated with broadenings and intensity losses of individual emission lines. Minerals that have suffered elevated levels of irradiation hence tend to be virtually non-luminescent. This review paper aims at giving an overview of the possible correlations of radiation damage and emission characteristics of minerals. After a brief, introductory summary of the damage-accumulation process and its causal corpuscular radiation, an array of examples is presented for how internal and/or external irradiation may change appreciably the emission of rock-forming and accessory minerals. As a detailed example for the complexity of changes of emissions upon damage accumulation, preliminary results of a case study of the photoluminescence (PL) of synthetic CePO4 irradiated with 8.8 MeV He ions are presented. Irradiation-induced spectral changes include (i) the initial creation, and subsequent depletion, of a broad-band, defect-related PL emission of orange colour, and (ii) gradual broadenings and intensity losses of PL lines related to electronic transitions of rare-earth elements, eventually leading to gradual loss of their splitting into multiple Stark levels (shown for the 4F3/2 → 4I9/2 transition of Nd3+).  相似文献   

6.
The orientation dependence of the luminescence of a well-characterized plagioclase crystal at room temperature and 40 K is reported. A beam of H + ions was used to provide the excitation. Ion beam luminescence provides emissions effectively from the bulk of the material, and therefore minimizes the contribution to the luminescence from atypical regions. The intensity of the luminescence is strongly orientation-dependent. The intensity and photon energy, particularly of the red/infrared and yellow emission bands, vary significantly. We interpreted this as resulting from Fe 3+ and Mn 2+ activator ions, respectively, on crystallographic sites with low point symmetry. An emission at 860 nm was also significantly orientation-dependent. The blue luminescence showed the least variability. At room temperature, a 350 nm near-UV emission was noted, whereas at 40 K, emissions were at 240, 260, 300 and 340 nm. UV emissions may result from Na + diffusion along interfaces within the plagioclase, notably albite-law (010) twins. This variability has significant consequences for the use of single-crystal quantitative luminescence techniques. We have also studied the dependence of the peak intensities and profiles during prolonged ion beam bombardment with heavier (He +) ions. Broadening of the red-infrared emission is interpreted as reflecting growing amorphization of the sample.  相似文献   

7.
Kunzite, the pink, manganese-bearing variety of spodumene, is strongly luminescent under UV or electron beam excitation. Laser excitation of an oriented kunzite single crystal has been used to determine the polarization dependence of the luminescence. The emission spectrum, assigned to an Mn2+ center, can be fitted by two Gaussian bands with maxima at 16 568 and 15 679 cm–1. Analysis of the temperature dependence of emission intensity and band width give estimates of the frequency of the phonons assisting the luminescence transitions. These appear to be bond stretching modes of the octahedral site. Analysis of the polarization dependence of emission intensity allows determination of the orientation of the emission dipole. Comparison of the polarization dependence of excitation and emission radiation shows that coupling between absorption dipole and emission dipole is incoherent.Work supported by the National Science Foundation under Grant No. DMR-74-00340  相似文献   

8.
《Chemical Geology》2002,182(2-4):203-225
Accessory gangue scheelite (CaWO4) from the Archaean Mt. Charlotte lode Au deposit can be divided into two types with different rare earth element (REE) signatures. In some scheelite grains, specific REE signatures are reflected by different cathodoluminescence colours, which can be used to map their often complex oscillatory intergrowths. Domains with specific REE contents from two grains were sampled for Sm/Nd, Rb/Sr and Pb isotopic analyses using a micro-drilling technique.Type I scheelite is strongly enriched in middle REE (MREE) and Eu anomalies are either absent or slightly positive. Four fragments collected from Type I regions of two crystals have initial 87Sr/86Sr and εNd values ranging from 0.70141 to 0.70163 and +2.5 to +3.5, respectively, and Pb isotope ratios reflecting the composition of greenstone sequence. This may indicate that Nd and Pb have their source, either locally or regionally, in the greenstones. Basic greenstone lithologies have 87Sr/86Sr<0.7015, and the radiogenic Sr signatures indicate that part of the Sr originated from felsic lithologies located either within or beneath the host greenstone pile. Alternatively, the Sr signature may have evolved from preferential leaching of a Rb-rich mineral during hydrothermal alteration of the greenstone.The REE patterns of Type II scheelite are either flat or MREE-depleted and have strong positive Eu anomalies. Three fragments collected from Type II regions of the same two crystals have initial 87Sr/86Sr ratios and εNd values between 0.70130 and 0.70146, and +1.1 to +2.6, respectively, and Pb isotope signatures that are once again similar to that of the greenstone. This implies that 87Sr/86Sr ratios in Type II fluids were closer to those of the host dolerite (0.7008–0.7013), due to more extensive fluid interaction with the dolerite.A positive correlation between Na and REE suggests that REE3+ are accommodated by the coupled substitution REE3++Na+=2 Ca2+ into both Type I and Type II scheelite. This is consistent with a fractional crystallisation model to explain the change in REE patterns from Type I to Type II, but not with a model involving different coupled substitutions and fluids from different origins. We propose that the complex REE and isotopic signatures of scheelite at Mt. Charlotte are related to small (<m) to medium (<km) scale processes involving mixing between “fresh” batches of hydrothermal fluid with fluids that had already been involved in extensive wall-rock alteration.The very high-εNd values measured in some scheelites have been previously used to link gold mineralisation with komatiites containing unusually high Sm/Nd ratios. However, tiny (<20 μm) grains of secondary hydroxyl-bastnäsite were found within micro-fractures of one scheelite grain containing an extremely high-εNd signature. The hydroxyl-bastnäsite probably formed during recent REE redistribution within the scheelite as a result of meteoric fluid circulation. The scale of this cryptic low-temperature alteration is sufficient to explain the anomalously high-εNdi values observed in scheelite from Western Australia.  相似文献   

9.
The study of radiation of intrinsic and impurity excitations in natural barite showed that the patterns of BaSO4 luminescence were mostly controlled by the presence of the [SO4] anion complex. Several types of self-radiation were registered including those at the expense of the presence of O2– ions of the axial and nonaxial configurations of the anionic group (emission bands within the wavelength ranges of 209–213 and 330–350 nm, respectively). Exitons located near the impurity and intrinsic defects largely participate in emission. Impurity defects participating in the luminescent centers of barite from the Ore Altai include Pb2+, Gd3+, Eu2+, Eu3+, Cu+, and Ag+ (under X-ray excitation). Variations in the spectral composition of barite indicate the different conditions of its formation.  相似文献   

10.
The luminescence spectra of a suite of natural sodium framework silicates including four different sodalite variants and tugtupite have been collected during X-ray irradiation as a function of temperature between 20 and 673 K. The origin of the emission bands observed in these samples is attributed to F-centres (360 nm), paramagnetic oxygen defects (400 and 450 nm), S2 ? ions (620 nm) and tetrahedral Fe3+ (730 nm). Luminescence in the yellow (550 nm) is tentatively attributed to Mn2+, and red luminescence in Cr-rich pink sodalite is possibly from Cr3+ activation. Sudden reduction in luminescence intensities of emission centres was observed for all minerals in the 60–120 K range. Since it is common to all the sodalite-group minerals, we infer it is a feature of the aluminosilicate framework. Sodalite luminescence has responses from substitutions on the framework (e.g. paramagnetic oxygen defects, Fe3+) which give sodalite properties akin to other framework silicates such as feldspar and quartz. However, the presence of the sodalite cage containing anions (such as F-centres, S2 ? ions) imparts additional properties akin to alkali halides. The possibility of coupling between Fe3+ and S2 ? is discussed. The overall luminescence behaviour of sodalite group can be understood in terms of competition between these centre types.  相似文献   

11.
Summary The mineral chemistry of a Variscan lamprophyre (kersantite) from the Frankenwald, Germany, has been investigated by electron microprobe. This potassic, Si-saturated, mafic rock contains an assemblage of different generations of titanite and allanite-(Ce), Th-rich zircon, and metamict REE–Ti–Zr–Th silicates. The primary ferroan-ceroan titanite contains unusually high contents of REE2O3 (max. (ΣLa to Sm)+Y = 36.8 oxide wt.%), ZrO2 (max. 5.4 wt.%), and ThO2 (max. 3.1 wt.%). Its empirical formula averages to (Ca0.31 La0.17 Ce0.30 Pr0.03 Nd0.08 Sm0.01 Y0.01 Fe2+0.06 Th0.02 Mn0.01)Σ1.00 (Ti0.60 Fe2+0.22 Al0.06 Zr0.07 Mg0.04 Nb0.01)Σ1.00 O1.00(Si0.93 Al0.07)Σ1.00 O4. Element correlations reveal operation of the complex substitution Ca2++Ti4++Th4+ ⇔ REE3++Al3++Zr4+. In comparison to allanite-(Ce), ferroan-ceroan titanite preferentially incorporated the LREE and Th. This finding is inconsistent with previous experimental studies and suggests that both minerals are not cogenetic. High Zr contents in titanite, usually known only from Si-undersaturated alkaline rocks, and the predominance of Fe2+ suggest that the ferroan-ceroan titanite crystallized from an alkali-rich, low-fO2 residual melt.  相似文献   

12.
Calcite crystals were grown from solution with single-crystal dimensions up to 3 mm and doped up to 0.1 at% with Nd3+ ions. Phase purity was verified by powder X-ray diffraction. The concentration of Nd3+ was measured by energy-dispersive spectrometry and Rutherford backscattering spectrometry. Micro X-ray fluorescence mapping of the calcite grains indicates uniform Nd distribution in as-grown crystal grains. X-ray absorption fine structure suggests that Nd3+ is substituted for Ca2+ with local lattice distortion. Temperature-dependent near-infrared spectroscopy of Nd3+ impurities in calcite reveals large inhomogeneous linewidths and smooth line profiles that are characteristic of glassy hosts, though the samples are well crystallized.  相似文献   

13.
In this study, a series of RE3+:YVO4 catalysts were successful synthesized by environmentally friendly mild hydrothermal and supercritical hydrothermal techniques. The rare earth-doped YVO4 photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy. The X-ray diffraction analysis reveals that the as-prepared YVO4 crystals are of tetragonal phase. Further, the Fourier transform infrared spectroscopy result shows the absence of OH– molecules. The photoluminescence spectroscopy curves and UV–Vis spectra suggest that the band gap energy of YVO4 is shifted to lower energy level due to doping of Nd3+ and Er3+ ions. The catalytic activities of the as-prepared RE3+:YVO4 samples were tested for the photodegradation of amaranth aqueous dye solution under sunlight irradiation. Remarkably, the rare earth-doped YVO4 nanocrystal sample showed outstanding photocatalytic degradation activities than undoped YVO4 nanocrystal sample with good reusability. Under full spectrum irradiation, the as-prepared Nd3+-doped YVO4 nanocrystals exhibited about 83% degradation efficiency. The apparent rate constant k for as-prepared Nd3+-doped YVO4 nanocrystals with 50 mg of photocatalyst exhibits highest k value (0.32 min?1), which is 2.9% higher than pure YVO4 nanocrystals (0.11 min?1).  相似文献   

14.
The optical absorption and luminescence spectra of MgAl2O4:Cr3+ natural spinel (from Ural) have been measured at 77 K and 293 K. The luminescent emission from 4 T 2g , 2 E g covers wide region of 600–750 nm. The emission spectrum at 77 K shows a very rich vibrational structure which can be mainly explained through the vibrational modes of the oxygen octahedron.  相似文献   

15.
The intrinsic luminescence center (LC) of SO 4 2? appears at 360 nm in all types of sulfates, but is absent in sulfates with large quantities of impurities. Three nonequivalent Gd3+ LC have been observed in luminescence spectra of anhydrite. Gd3+, Ce3+ O 2 ? LC were established in celestite. Photoluminescence (PL) bands in the sulfates were assigned as follows: the band at 460 nm is related to Eu2+ (a connection with Al3+ or donor-acceptor pair is possible also) in sulfates of Ca and Ba; bands at 520 nm and 590 nm are related to VO4, MoO4 and TiO4 substituting SO4; the band at 660 nm is assigned to Ti3+ X-ray luminescence (XL) band at 620 nm is assigned to Ag+.  相似文献   

16.
Optical absorption spectra (OAS) of synthetic single crystals of the solid solution spinel sensu stricto (s.s.)–magnesioferrite, Mg(Fe3+Al1???y)2O4 (0?y?≤ 0.3), have been measured between 12 500 and 28 500?cm?1. Chemical composition and Fe3+ site distribution have been measured by electron microprobe and Mössbauer spectroscopy, respectively. Ferric iron is ordered to the tetrahedral site for samples with small magnesioferrite component, and this ordering is shown to increase with magnesioferrite component. The optical absorption spectra show a strong increase in band intensities with Fe3+→Al substitution. Prominent and relatively sharp absorption bands are observed at 25 300 and 21 300?cm?1, while less intense bands occur at 22 350, 18 900, 17 900 and 15 100?cm?1. On the basis of band energies, band intensities and the compositional effect on band intensity, as well as structural considerations, we assign the observed bands to electronic transitions in IVFe3+–VIFe3+clusters. A linear relationship (R 2= 0.99) between the αnet value of the absorption band at 21 300?cm?1 and [IVFe3+]?·?[VIFe3+] concentration product has been defined: αnet=2.2?+?15.8 [IVFe3+]?·?[VIFe3+]. Some of the samples have been heat-treated between 700 and 1000?°C to investigate the relation between Fe3+ ordering and absorption spectra. Increase of cation disorder with temperature is observed, which corresponds to a 4% reduction in the number of active clusters. Due to the high spatial resolution (??～?10?μm), the OAS technique may be used as a microprobe for determination of Fe3+ concentration or site partitioning. Potential applications of the technique include analysis of small crystals and of samples showing zonation with respect to total Fe3+ and/or ordering.  相似文献   

17.
A selected set of five different kyanite samples was analysed by electron microprobe and found to contain chromium between <0.001 and 0.055 per formula unit (pfu). Polarized electronic absorption spectroscopy on oriented single crystals, R1, R2-sharp line luminescence and spectra of excitation of λ3- and λ4-components of R1-line of Cr3+-emission had the following results: (1) The Fe2+–Ti4+ charge transfer in c-parallel chains of edge connected M(1) and M(2) octahedra shows up in the electronic absorption spectra as an almost exclusively c(||Z′)-polarized, very strong and broad band at 16000 cm−1 if <, in this case the only band in the spectrum, and at an invariably lower energy of 15400 cm−1 in crystals with  ≥ . The energy difference is explained by an expansion of the Of–Ok, and Ob–Om edges, by which the M(1) and M(2) octahedra are interconnected (Burnham 1963), when Cr3+ substitutes for Al compared to the chromium-free case. (2) The Cr3+ is proven in two greatly differing crystal fields a and b, giving rise to two sets of bands, derived from the well known dd transitions of Cr3+ 4A2g→4T2g(F)(I), →4T1g(F)(II), and →4T1g(P)(III). Band energies in the two sets a and b, as obtained by absorption, A, and excitation, E, agree well: I: 17300(a, A), 17200(a, E), 16000(b, A), 16200(b, E); II: 24800(a, A), 24400(a, E); 22300(b, A), 22200(b, E); III: 28800(b,A) cm−1. Evaluation of crystal field parameters from the bands in the electronic spectra yield Dq(a)=1730 cm−1, Dq(b)=1600 cm−1, B(a)=790 cm−1, B(b)=620 cm−1 (errors ca. ±10 cm−1), again in agreement with values extracted from the λ3, λ4 excitation spectra. The CF-values of set a are close to those typical of Cr3+ substituting for Al in octahedra of other silicate minerals without constitutional OH− as for sapphirine, mantle garnets or beryl, and are, therefore, interpreted as caused by Cr3+ substituting for Al in some or all of the M(1) to M(4) octaheda of the kyanite structure, which are crystallographically different but close in their mean Al–O distances, ranging from 1.896 to 1.919 A (Burnham 1963), and slight degrees of distortion. Hence, band set a originates from substitutive Cr3+ in the kyanite structural matrix. The CF-data of Cr3+ type b, expecially B, resemble those of Cr3+ in oxides, especially of corundum type solid solutions or eskolaite. This may be interpreted by the assumption that a fraction of the total chromium contents might be allocated in a precursor of a corundum type exsolution. Received: 3 January 1997 / Revised, accepted: 2 May 1997  相似文献   

18.
Partition coefficients (zircon/meltDM) for rare earth elements (REE) (La, Ce, Nd, Sm, Dy, Er and Yb) and other trace elements (Ba, Rb, B, Sr, Ti, Y and Nb) between zircon and melt have been calculated from secondary ion mass spectrometric (SIMS) analyses of zircon/melt inclusion pairs. The melt inclusion-mineral (MIM) technique shows that DREE increase in compatibility with increasing atomic number, similar to results of previous studies. However, DREE determined using the MIM technique are, in general, lower than previously reported values. Calculated DREE indicate that light REE with atomic numbers less than Sm are incompatible in zircon and become more incompatible with decreasing atomic number. This behavior is in contrast to most previously published results which indicate D > 1 and define a flat partitioning pattern for elements from La through Sm. The partition coefficients for the heavy REE determined using the MIM technique are lower than previously published results by factors of ≈15 to 20 but follow a similar trend. These differences are thought to reflect the effects of mineral and/or glass contaminants in samples from earlier studies which employed bulk analysis techniques.DREE determined using the MIM technique agree well with values predicted using the equations of Brice (1975), which are based on the size and elasticity of crystallographic sites. The presence of Ce4+ in the melt results in elevated DCe compared to neighboring REE due to the similar valence and size of Ce4+ and Zr4+. Predicted zircon/meltD values for Ce4+ and Ce3+ indicate that the Ce4+/Ce3+ ratios of the melt ranged from about 10−3 to 10−2. Partition coefficients for other trace elements determined in this study increase in compatibility in the order Ba < Rb < B < Sr < Ti < Y < Nb, with Ba, Rb, B and Sr showing incompatible behavior (DM < 1.0), and Ti, Y and Nb showing compatible behavior (DM > 1.0).The effect of partition coefficients on melt evolution during petrogenetic modeling was examined using partition coefficients determined in this study and compared to trends obtained using published partition coefficients. The lower DREE determined in this study result in smaller REE bulk distribution coefficients, for a given mineral assemblage, compared to those calculated using previously reported values. As an example, fractional crystallization of an assemblage composed of 35% hornblende, 64.5% plagioclase and 0.5% zircon produces a melt that becomes increasingly more enriched in Yb using the DYb from this study. Using DYb from Fujimaki (1986) results in a melt that becomes progressively depleted in Yb during crystallization.  相似文献   

19.
Amphibole/liquid partition coefficients for the REE(Damph/liqREE) obtained from natural rocks increase systematically with bulk rock compositional change from basalt to rhyolite and are higher for the middle to heavy REE. Five new experimentally determined sets of DREE (La, Sm, “Eu2+”, Ho, Lu)and 4 published sets are similar to these data and provide values for use in geochemical modelling of magmatic processes involving amphibole, over a range of temperature, pressure and oxygen fugacity. The partition coefficients increase significantly with decreasing temperature, and increase slightly with increasing oxygen fugacity. Pressure does not appear to have a major effect, although one data set suggests increased pressure lowers Damph/liqREE in a basaltic composition.  相似文献   

20.
The crystal chemistry of red phlogopites from Mt. Vulture (Italy) ignimbrites has been studied by electron microprobe, secondary ion mass spectrometry (SIMS), single crystal structural investigation and Fourier transform infrared (FTIR) spectroscopy. The analysed phlogopite has Fe/(Fe + Mg) ∼ 0.35, TiO2 (wt%): 2.8–5.0 and H2O (wt%): 1.24–3.37. Infrared spectra revealed the presence of bands due to the NH4+ and H2O stretching and bending vibrations. The samples belong to the 1M polytype. The bimodal behaviour of several structural parameters allows red micas to be clustered into two distinct groups: K+ ↔ NH4+, H2O and M3+-vacancy substitutions dominate in the first group; M3+,4+-oxy, in the second group. It has to be pointed out that quantitative analysis of hydrogen (via SIMS) together with the characterization of the local environment of the anionic site (via FTIR) are fundamental in assessing the correct structural formula and the substitution mechanisms in micas. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

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