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1.
H. W. Nesbitt A. G. Schaufuss G. M. Bancroft R. Szargan 《Physics and Chemistry of Minerals》2002,29(1):72-77
Synchrotron excited X-ray photoelectron spectra (SXPS) of hexagonal pyrrhotite reveal three distinct Fe 3d-derived photopeaks within its outer valence band. The t
2gα band (majority spin) is centered at about 2.5 eV, the e
g
α band at about 1.0 eV and the t
2gβ (minority spin) contribution at about 0.25 eV. From these data the ligand field splitting energy is 1.5 (±0.2) eV and the
majority spin pairing energy is 2.25 (±0.2) eV. These are the first such XPS measurements for this mineral. S 3p-derived bonding and non-bonding bands are identified, with the former centred at about 6.5 eV and the latter near 4.5 eV.
The XPS results are remarkably consistent with SCF-Xα scattered wave molecular orbital calculations. Although the calculations
and the collected spectra are consistent, they differ from a recent interpretation of the pyrrhotite valence band. An explanation
for the discrepant results is provided. Auger resonant enhancement of Fe 3d photopeaks at 60 eV photon energy results in the
t
2gα emission (at 2.5 eV) being strongly enhanced and broader than the t
2gβ emission (0.25 eV). The explanation of these observations requires the presence of weak Fe–Fe π and π* crystal (molecular) orbitals located near 2.5 eV, and separated by no more than about 0.5 eV. The π-bonded crystal orbitals
are derived from weak mixing of adjacent Fe t
2g atomic orbitals along the c crystallographic axis.
Received: 15 June 2000 / Accepted: 11 June 2001 相似文献
2.
Summary Investigations of natural and synthetic quartz specimens by cathodoluminescence (CL) microscopy and spectroscopy, electron
paramagnetic resonance (EPR) and trace-element analysis showed that various luminescence colours and emission bands can be
ascribed to different intrinsic and extrinsic defects.
The perceived visible luminescence colours in quartz depend on the relative intensities of the dominant emission bands between
380 and 700 nm. Some of the CL emissions of quartz from the UV to the yellow spectral region (175 nm, 290 nm, 340 nm, 420 nm,
450 nm, 580 nm) can be related to intrinsic lattice defects. Extrinsic defects such as the alkali (or hydrogen)-compensated
[AlO4/M+] centre have been suggested as being responsible for the transient emission band at 380–390 nm and the short-lived blue-green
CL centered around 500 nm. CL emissions between 620 and 650 nm in the red spectral region are attributed to the nonbridging
oxygen hole centre (NBOHC) with several precursors.
The weak but highly variable CL colours and emission spectra of quartz can be related to genetic conditions of quartz formation.
Hence, both luminescence microscopy and spectroscopy can be used widely in various applications in geosciences and techniques.
One of the most important fields of application of quartz CL is the ability to reveal internal structures, growth zoning and
lattice defects in quartz crystals not discernible by means of other analytical techniques. Other fields of investigations
are the modal analysis of rocks, the provenance evaluation of clastic sediments, diagenetic studies, the reconstruction of
alteration processes and fluid flow, the detection of radiation damage or investigations of ultra-pure quartz and silica glass
in technical applications.
Zusammenfassung
Ursachen, spektrale Charakteristika und praktische Anwendungen der Kathodolumineszenz (KL) von Quarz – eine Revision
Untersuchungen von natürlichen und synthetischen Quarzproben mittels Kathodolumineszenz (KL) Mikroskopie und -spektroskopie,
Elektron Paramagnetischer Resonanz (EPR) und Spurenelementanalysen zeigen verschiedene Lumineszenzfarben und Emissionsbanden,
die unterschiedlichen intrinsischen und extrinsischen Defekten zugeordnet werden k?nnen.
Die sichtbaren Lumineszenzfarben von Quarz werden durch unterschiedliche Intensit?tsverh?ltnisse der dominierenden Emissionsbanden
zwischen 380 und 700 nm verursacht. Einige der KL Emissionen vom UV bis zum gelben Spektralbereich (175 nm, 290 nm, 340 nm,
420 nm, 450 nm, 580 nm) stehen im Zusammenhang mit intrinsischen Defekten. Die kurzlebigen Lumineszenzemissionen bei 380–390 nm
sowie 500 nm werden mit kompensierten [AlO4/M+]-Zentren in Verbindung gebracht. Die KL-Emissionen im roten Spektralbereich bei 620 bis 650 nm haben ihre Ursache im “nonbridging
oxygen hole centre” (NBOHC) mit verschiedenen Vorl?uferzentren.
Die unterschiedlichen KL-Farben und Emissionsspektren von Quarz k?nnen oft bestimmten genetischen Bildungsbedingungen zugeordnet
werden und erm?glichen deshalb vielf?ltige Anwendungen in den Geowissenschaften und in der Technik. Eine der gravierendsten
Einsatzm?glichkeiten ist die Sichtbarmachung von Internstrukturen, Wachstumszonierungen und Defekten im Quarz, die mit anderen
Analysenmethoden nicht oder nur schwer nachweisbar sind. Weitere wesentliche Untersuchungsschwerpunkte sind die Modalanalyse
von Gesteinen, die Eduktanalyse klastischer Sedimente, Diageneseuntersuchungen, die Rekonstruktion von Alterationsprozessen
und Fluidmigrationen, der Nachweis von Strahlungssch?den oder die Untersuchung von ultrareinem Quarz und Silikaglas für technische
Anwendungen.
Received March 29, 2000 Accepted October 27, 2000 相似文献
3.
Aierken Sidike Alifu Sawuti Xiang-Ming Wang Heng-Jiang Zhu S. Kobayashi I. Kusachi N. Yamashita 《Physics and Chemistry of Minerals》2007,34(7):477-484
The photoluminescence and excitation spectra of sodalites from Greenland, Canada and Xinjiang (China) are observed at 300
and 10 K in detail. The features of the emission and excitation spectra of the orange-yellow fluorescence of these sodalites
are independent of the locality. The emission spectra at 300 and 10 K consist of a broad band with a series of peaks and a
maximum peak at 648 and 645.9 nm, respectively. The excitation spectra obtained by monitoring the orange-yellow fluorescence
at 300 and 10 K consist of a main band with a peak at 392 nm. The luminescence efficiency of the heat-treated sodalite from
Xinjiang is about seven times as high as that of untreated natural sodalite. The emission spectrum of the S2
− center in sodalite at 10 K consists of a band with a clearly resolved structure with a series of maxima spaced about 560 cm−1 (20–25 nm) apart. Each narrow band at 10 K shows a fine structure consisting of a small peak due to the stretching vibration
of the isotopic species of 32S34S−, a main peak due to that of the isotopic species of 32S2
− and five peaks due to phonon sidebands of the main peak. 相似文献
4.
Aierken Sidike Nuerrula Jilili S. Kobayashi K. Atobe Nobuhiko Yamashita 《Physics and Chemistry of Minerals》2010,37(2):83-89
The photoluminescence (PL) spectra, optical excitation spectra and PL decay curves of anthophyllite from Canada were obtained
at 300 and 10 K. The MnO content in the sample, determined using an electron probe microanalyzer, was high at 5.77 wt%. In
the PL spectra obtained under 410-nm excitation, bright red bands with peaks at 651 and 659 nm were observed at 300 and 10 K,
respectively. The origin of the red luminescence was ascribed to Mn2+ in anthophyllite from the analysis of the excitation spectra and PL decay times of 6.1–6.6 ms. In the PL spectra obtained
under 240-nm excitation at 300 K, a small violet band with a peak at 398 nm was observed. On the violet band at 10 K, a vibronic
structure was observed. The origin of the violet luminescence was attributed to a minor impurity in anthophyllite. 相似文献
5.
J. Garcia-Guinea P. D. Townsend L. Sanchez-Muñoz J. M. Rojo 《Physics and Chemistry of Minerals》1999,26(8):658-667
Laboratory driven ionic thermal exchange of alkali feldspars from K to Na produces samples which are strongly luminescent
in the ultraviolet region near 320 nm. The sites providing this luminescence are suggested as being correlated with the motion
of Na atoms along interface-interphases of the material (i.e. with Na-O bond fracture). The thermoluminescence peaks show
multi-order kinetics. Thermal preheatings of low albite sensitize the feldspar lattice with respect to thermoluminescence
generated by exposure to UV irradiation and heating produces a strong blue luminescence spread over the range 350 nm to 500 nm
band in feldspars. The upper temperature for thermoluminescence in feldspars is ∼300 °C, which is also the point where ionic
conductivity of albite (010) begins, but the 300 °C region is also the starting point of a large second glow peak in adularia.
Whilst it seems appropriate to link the Na motion to the 350–500 nm emission, it is unclear whether these changes are the
result of the large anisotropic thermal vibration of Na atoms or the massive Na jumps that occur when the lattice reaches
300 °C. A speculative model is considered in which the UV TL emissions of natural minerals are linked to different interface-interphases
(grain boundaries, exsolution limits, twinning planes, antiphase domains). Increased interface coherency energies are related
to the kinetic order and the spectral position of luminescence emission peaks.
Received: 3 December 1998 / Revised, accepted: 17 April 1999 相似文献
6.
M. R. Krbetschek J. Götze G. Irmer U. Rieser T. Trautmann 《Mineralogy and Petrology》2002,76(3-4):167-177
Summary ?Feldspar specimens covering the whole Or–Ab–An ternary have been investigated by cathodoluminescence (CL), photoluminescence
(PL), radioluminescence (RL) and radiophosphorescence (RP) spectrometry. A red luminescence emission, which is commonly explained
by Fe3+ lattice defects, is a characteristic feature of all the spectra. Different shifts of the peak-wavelength between ∼680–750 nm
(1.82–1.65 eV) were observed with varying feldspar composition. Despite the dependence of the peak position on the Ca/Na ratio,
initially described for CL in the 1970s, there is also a shift induced by changing NaK composition. The observed effects can
be explained by known relations that the peak position of the red luminescence emission in feldspars can be affected both
by the structural state of the feldspar and the site occupancy of the trivalent iron. In the case of alkali feldspars another
factor may influence the peak-shift. The incorporation of the larger potassium ion causes non-linear variations of the cell
dimensions and therefore Fe–O bond distance. The behaviour of the red peak-shift dependent on the feldspar composition is
not equal for all types of luminescence investigated. This is most likely caused by the different luminescence excitation
mechanism.
Received December 3, 2001; revised version accepted March 25, 2002 相似文献
7.
Time-resolved luminescence spectra of natural and synthetic hydrous volcanic glasses with different colors and different
Fe, Mn, and H2O content were measured, and the implications for the glass structure are discussed. Three luminescence ranges are observed
at about 380–460, 500–560, and 700–760 nm. The very short-living (lifetimes less than 40 ns) blue band (380–460 nm) is most
probably due to the 4T2(4D) →6A1(6S) and 4A1(4G) →6A1(6S) ligand field transitions of Fe3+. The green luminescence (500–560 nm) arises from the Mn2+ transition 4T1(4G) →6A1(6S). It shows weak vibronic structure, short lifetimes less than 250 μs, and indicates that Mn2+ is tetrahedrally coordinated, occupying sites with similar distortions and ion–oxygen interactions in all samples studied.
The red luminescence (700–760 nm) arising from the 4T1(4G) →6A1(6S) transition of Fe3+ has much longer lifetimes of the order of several ms, and indicates that ferric iron is also mainly tetrahedrally coordinated.
Increasing the total water content of the glasses leads to quenching of the red luminescence and decrease of the distortions
of the Fe3+ polyhedra.
Received: 30 July 2001 / Accepted: 15 November 2001 相似文献
8.
Alain Cheilletz Dominique Gasquet Fouad Filali Douglas A. Archibald Massimo Nespolo 《Mineralium Deposita》2010,45(4):323-329
El Hammam is the only fluorite mine in Morocco (production 100,000 t/year). The fluorite mineralization is in an array of
fluorite–calcite veins and is characterized by unusually high REE content in carbonate minerals (1,400 ppm in calcite; up
to 2,000 ppm in siderite) and in fluorite (about 600 ppm). Since the 1960s, the genesis of the deposit has been attributed
to a mesothermal hydrothermal event connected with late-Variscan granitic intrusions. Precise 40Ar/39Ar dating of hydrothermal K-feldspar yields an age of formation of the El Hammam deposit at 205 ± 1 Ma. Its genesis is therefore
associated in time and space with the development of the Triassic–Jurassic basins and the associated anorogenic continental
flood basalts of the Moroccan Mesetian Middle Atlas. The source of the hydrothermal mineralization (magmatic and/or metamorphic)
is discussed. 相似文献
9.
Meta-sedimentary rocks including marbles and calcsilicates in Central Dronning Maud Land (CDML) in East Antarctica experienced
a Pan-African granulite facies metamorphism with peak metamorphic conditions around 830 ± 20 °C at 6.8 ± 0.5 kbar which was
accompanied by the post-kinematic intrusion of huge amounts of syenitic (charnockitic) magmas at 4.5 ± 0.7 kbar. The marbles
and calcsilicates may represent meta-evaporites as indicated by the occurrence of metamorphic gypsum/anhydrite and Cl-rich
scapolite that formed in the presence of saline fluids with X
NaCl in the range 0.15–0.27. The marbles and calcsilicates bear biotite, tremolite and/or hornblende and humite group minerals
(clinohumite, chondrodite and humite) which are inferred to have crystallized at about 650 °C and 4.5 kbar. The syenitic intrusives
contain late-magmatic biotite and amphibole (formed between 750 and 800 °C) as well as relictic magmatic fayalite, orthopyroxene
and clinopyroxene. Two syenite and two calcsilicate samples contain fluorite. Corona textures in the marbles and calcsilicates
suggest very low fluid-rock ratios during the formation of the retrograde (650 °C) assemblages. Biotite in all but two syenite
samples crystallized at log(f
H
2
O/f
HF) ratios of 2.9 ± 0.4, while in the calcsilicates, both biotite and humite group minerals indicate generally higher log(f
H
2
O/f
HF) values of up to 5.2. A few samples, though, overlap with the syenite values. Log(f
H
2
O/f
HCl) derived from biotite covers the range 0.5–2.6 in all rock types. Within a single sample, the calculated values for both
parameters vary typically by 0.1 to 0.8 log units. Water and halogen acid fugacities calculated from biotite-olivine/orthopyroxene-feldspar-quartz
equilibria and the above fugacity ratios are 1510–2790 bars for H2O, 1.3–5.3 bars for HF and 7–600 bars for HCl. The results are interpreted to reflect the reaction of relatively homogeneous
magmatic fluids [in terms of log(f
H
2
O
/f
HF)] derived from the late-magmatic stages of the syenites with both earlier crystallized, still hotter parts of the syenites
and with adjacent country rocks during down-temperature fluid flow. Fluorine is successively removed from the fluid and incorporated
into F-bearing minerals (close to the syenite into metamorphic fluorite). In the course of this process log(f
H
2
O
/f
HF) increases significantly. Chlorine preferably partitions into the fluid and hence log(f
H
2
O
/f
HCl) does not change markedly during fluid-rock interaction.
Received: 28 November 1997 / Accepted: 27 April 1998 相似文献
10.
Several F, Pb, Zn and Ba deposits are located in the province of Zaghouan in north-eastern Tunisia. They are hosted in Lower
Liassic or Upper Jurassic reef limestones, and the overlying condensed Carixian phosphatic limestones and Campanian marls,
respectively. The mineralization occurs in three types of orebodies: stratiform replacement heaps and lenses (Jebel Stah and
Hammam Zriba), breccia fillings and dissolution void fillings (Sidi Taya) and lodes (Jebel Oust). More than one generation
of fluorite is observed in the stratiform deposits. Microthermometric analyses of the inclusion fluids observed in fluorite
and quartz show that the economic concentrations of fluorite have deposited from moderate to highly saline (12–22.5 wt% NaCl
equivalents) hydrothermal (110–160 °C) mineralizing fluids at the center (Jebel Stah, Sidi Taya) and to the east of the province
(Hammam Zriba). Late remobilizations, observed in the stratiform deposits, are related to the circulation of a warmer (up
to 185 °C) but less saline (10 wt% NaCl equivalents) fluid (Jebel Stah) and more saline (12–22 wt% NaCl equivalents) fluid
(Hammam Zriba). The highest temperature (up to 250 °C) and salinity (32–34 wt% NaCl equivalents) are observed to the west
of the province of Zaghouan (Jebel Oust). Less saline (3–6 wt% NaCl equivalents) and moderately hot to hot fluids (up to 220 ± 20 °C)
and rich in gaseous CO2 invade most of the ore deposits in later stages and give rise to the massive quartz within fractures at Jebel Stah. Chemical
analyses of the fluids extracted from the inclusions occuring in fluorite show compositions dominated by the presence of Na+, Ca2+ and Cl− ionic species and allow the mean temperature of the fluids in the source reservoir to be estimated as 275 ± 25 °C. The circulation
of the ore-forming fluids is triggered by a regional tectonic extensional phase which occurs within the post-Jurassic to ante-Miocene
time interval. The deposition of the economic concentrations of fluorite resulted from the decrease in pressure and temperature
of the hydrothermal brines (Jebel Oust), along with the increase in the dissolved calcium activity (Jebel Stah and Sidi Taya),
or a decrease in salinity due to the mixing with a hot, less saline and Na-poor, Ca-rich fluid (Hammam Zriba). The mineralogical
associations (CaF2, PbS, ZnS, BaSO4) hosted within carbonate rocks, the temperatures and the salinities of the fluids that gave rise to the more important ore
deposits (110–160 °C and 12–22.5 wt% NaCl equivalents), their composition (Na, Ca, Cl) and the molar ratios between the major
ionic species, as well as the presence of liquid hydrocarbons in the mineralizing fluids, show that the ore deposits of the
province of Zaghouan belong to the carbonate-hosted F, Pb, Zn, Ba Mississippi Valley-type deposits.
Received: 23 June 1995 / Accepted: 18 November 1996 相似文献
11.
The second-order elastic constants of CaF2 (fluorite) have been determined by Brillouin scattering to 9.3 GPa at 300 K. Acoustic velocities have been measured in the
(111) plane and inverted to simultaneously obtain the elastic constants and the orientation of the crystal. A notable feature
of the present inversion is that only the density at ambient condition was used in the inversion. We obtain high-pressure
densities directly from Brillouin data by conversion to isothermal conditions and iterative integration of the compression
curve. The pressure derivative of the isentropic bulk modulus and of the shear modulus determined in this study are 4.78 ± 0.13
and 1.08 ± 0.07, which differ from previous low-pressure ultrasonic elasticity measurements. The pressure derivative of the
isothermal bulk modulus is 4.83 ± 0.13, 8% lower than the value from static compression, and its uncertainty is lower by a
factor of 3. The elastic constants of fluorite increase almost linearly with pressure over the whole investigated pressure
range. However, at P ≥ 9 GPa, C
11 and C
12 show a subtle structure in their pressure dependence while C
44 does not. The behavior of the elastic constants of fluorite in the 9–9.3 GPa pressure range is probably affected by the onset
of a high-pressure structural transition to a lower symmetry phase (α-PbCl2 type). A single-crystal Raman scattering experiment performed in parallel to the Brillouin measurements shows the appearance
of new features at 8.7 GPa. The new features are continuously observed to 49.2 GPa, confirming that the orthorhombic high-pressure
phase is stable along the whole investigated pressure range, in agreement with a previous X-ray diffraction study of CaF2 to 45 GPa. The high-pressure elasticity data in combination with room-pressure values from previous studies allowed us to
determine an independent room-temperature compression curve of fluorite. The new compression curve yields a maximum discrepancy
of 0.05 GPa at 9.5 GPa with respect to that derived from static compression by Angel (1993). This comparison suggests that
the accuracy of the fluorite pressure scale is better than 1% over the 0–9 GPa pressure range.
Received: 10 July 2001 / Accepted: 7 March 2002 相似文献
12.
Four of the major plutons in the vicinity of the Candelaria mine (470 Mt at 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag) and a dike–sill system exposed in the Candelaria open pit have been dated with the U–Pb zircon method. The new geochronological data indicate that dacite magmatism around 123 Ma preceded the crystallization of hornblende diorite (Khd) at 118 ± 1 Ma, quartz–monzonite porphyry (Kqm) at 116.3 ± 0.4 Ma, monzodiorite (Kmd) at 115.5 ± 0.4 Ma, and tonalite (Kt) at 110.7 ± 0.4 Ma. The new ages of the plutons are consistent with field relationships regarding the relative timing of emplacement. Plutonism temporally overlaps with the iron oxide Cu–Au mineralization (Re–Os molybdenite ages at ∼115 Ma) and silicate alteration (ages mainly from 114 to 116 and 110 to 112 Ma) in the Candelaria–Punta del Cobre district. The dated dacite porphyry and hornblende diorite intrusions preceded the ore formation. A genetic link of the metallic mineralization with the quartz–monzonite porphyry and/or the monzodiorite is likely. Both of these metaluminous, shoshonitic (high-K) intrusions could have provided energy and contributed fluids, metals, and sulfur to the hydrothermal system that caused the iron oxide Cu–Au mineralization. The age of the tonalite at 110.7 Ma falls in the same range as the late alteration at 110 to 112 Ma. Tonalite emplacement may have sustained existing or driven newly developed hydrothermal cells that caused this late alteration or modified 40Ar/39Ar and K/Ar systematic in some areas. 相似文献
13.
Aierken Sidike I. Kusachi S. Kobayashi K. Atobe N. Yamashita 《Physics and Chemistry of Minerals》2008,35(3):137-145
The emission and excitation spectra of yellow luminescence due to S2
− in scapolites (#1 from Canada and #2 from an unknown locality) were observed at 300, 80 and 10 K. Emission and excitation
bands at 10 K showed vibronic structures with a series of maxima spaced 15–30 and 5–9 nm, respectively. The relative efficiency
of yellow luminescence from scapolite #2 was increased up to 117 times by heat treatment at 1,000°C for 2 h in air. The enhancement
of yellow luminescence by heat treatment was ascribed to the alteration of SO3
2− and SO4
2− to S2
− in scapolite. 相似文献
14.
The equilibrium water content of cordierite has been measured for 31 samples synthesized at pressures of 1000 and 2000 bars
and temperatures from 600 to 750° C using the cold-seal hydrothermal technique. Ten data points are presented for pure magnesian
cordierite, 11 data points for intermediate iron/magnesium ratios from 0.25 to 0.65 and 10 data points for pure iron cordierite.
By representing the contribution of H2O to the heat capacity of cordierite as steam at the same temperature and pressure, it is possible to calculate a standard
enthalpy and entropy of reaction at 298.18° K and 1 bar for,
(Mg,Fe)2Al4Si5O18+H2O ⇄ (Fe,Mg)2Al4Si5O18.H2O
Combining the 31 new data points with 89 previously published experimental measurements gives: ΔH
°
r
=–37141±3520 J and ΔS
°
r
=–99.2±4 J/degree. This enthalpy of reaction is within experimental uncertainty of calorimetric data. The enthalpy and entropy
of hydration derived separately for magnesian cordierite (–34400±3016 J, –96.5±3.4 J/degree) and iron cordierite (–39613±2475,
–99.5±2.5 J/degree) cannot be distinguished within the present experimental uncertainty. The water content as a function of
temperature, T(K), and water fugacity, f(bars), is given by n
H2O=1/[1+1/(K ⋅ f
H2O)] where the equilibrium constant for the hydration reaction as written above is, ln K=4466.4/T–11.906 with the standard state for H2O as the gas at 1 bar and T, and for cordierite components, the hydrous and anhydrous endmembers at P and T.
Received: 2 August 1994/Accepted: 7 February 1996 相似文献
15.
J. Götze M. Plötze Th. Götte R. D. Neuser D. K. Richter 《Mineralogy and Petrology》2002,76(3-4):195-212
Summary ?Sheet silicates of the serpentine–kaolin-group (serpentine, kaolinite, dickite, nacrite, halloysite), the talc–pyrophyllite-group
(talc, pyrophyllite), the smectite-group (montmorillonite), and illite (as a mineral of the mica-group) were investigated
to obtain information concerning their cathodoluminescence behaviour. The study included analyses by cathodoluminescence (CL
microscopy and spectroscopy), electron paramagnetic resonance (EPR), X-Ray diffraction (XRD), scanning electron microscopy
(SEM) and trace element analysis.
In general, all dioctahedral clay minerals exhibit a visible CL. Kaolinite, dickite, nacrite and pyrophyllite have a characteristic
deep blue CL, whereas halloysite emission is in the greenish-blue region. On the contrary, the trioctahedral minerals (serpentine,
talc) and illite do not show visible CL.
The characteristic blue CL is caused by an intense emission band around 400 nm (double peak with two maxima at 375 and 410 nm).
EPR measurements indicate that this blue emission can be related to radiation induced defect centres (RID), which occur as
electron holes trapped on apical oxygens (Si–O centre) or located at the Al–O–Al group (Al substituting Si in the tetrahedron).
Additional CL emission bands were detected at 580 nm in halloysite and kaolinite, and between 700 and 800 nm in kaolinite,
dickite, nacrite and pyrophyllite.
Time-resolved spectral CL measurements show typical luminescence kinetics for the different clay minerals, which enable differentiation
between the various dioctahedral minerals (e.g. kaolinite and dickite), even in thin section.
Received December 3, 2001; revised version accepted February 27, 2002 相似文献
16.
Hydroxyl defects in garnets from mantle xenoliths in kimberlites of the Siberian platform 总被引:12,自引:0,他引:12
A suite of more than 200 garnet single crystals, extracted from 150 xenoliths, covering the whole range of types of garnet
parageneses in mantle xenoliths so far known from kimberlites of the Siberian platform and collected from nearly all the kimberlite
pipes known in that tectonic unit, as well as some garnets found as inclusions in diamonds and olivine megacrysts from such
kimberlites, were studied by means of electron microprobe analysis and single-crystal IR absorption spectroscopy in the v
OH vibrational range in search of the occurrence, energy and intensity of the v
OH bands of hydroxyl defects in such garnets and its potential use in an elucidation of the nature of the fluid phase in the
mantle beneath the Siberian platform. The v
OH single-crystal spectra show either one or a combination of two or more of the following major v
OH bands, I 3645–3662 cm−1, II 3561–3583 cm−1, III 3515–3527 cm−1, and minor bands, Ia 3623–3631 cm−1, IIa 3593–3607 cm−1. The type of combination of such bands in the spectrum of a specific garnet depends on the type of the rock series of the
host xenolith, Mg, Mg-Ca, Ca, Mg-Fe, or alkremite, on the xenolith type as well as on the chemical composition of the respective
garnet. Nearly all garnets contain band systems I and II. Band system III occurs in Ti-rich garnets, with wt% TiO2 > ca. 0.4, from xenoliths of the Mg-Ca and Mg-Fe series, only. The v
OH spectra do not correspond to those of OH− defects in synthetic pyropes or natural ultra-high pressure garnets from diamondiferous metamorphics. There were no indications
of v
OH from inclusions of other minerals within the selected 60 × 60 μm measuring areas in the garnets. The v
OH spectra of pyrope-knorringite- and pyrope-knorringite-uvarovite-rich garnets included in diamonds do not show band systems
I to III. Instead, they exhibit one weak, broad band (Δv
OH 200–460 cm−1) near 3570 cm−1, a result that was also obtained on pyrope-knorringite-rich garnets extracted from two olivine megacrysts. The quantitative
evaluation, on the basis of relevant existing calibrational data (Bell et al. 1995), of the sum of integral intensities of
all v
OH bonds of the garnets studied yielded a wide range of “water” concentrations within the set of the different garnets, between
values below the detection limit of our single-crystal IR method, near 2 × 10−4 wt%, up to 163 × 10−4 wt%. The “water” contents vary in a complex manner in garnets from different xenolith types, obviously depending on a large
number of constraints, inherent in the crystal chemistry as well as the formation conditions of the garnets during the crystallization
of their mantle host rocks. Secondary alteration effects during uplift of the kimberlite, play, if any, only a minor role.
Despite the very complex pattern of the “water” contents of the garnets, preventing an evaluation of a straightforward correlation
between “water” contents of the garnets and the composition of the mantle's fluid phase during garnet formation, at least
two general conclusions could be drawn: (1) the wide variation of “water” contents in garnets is not indicative of regional
or local differences in the composition of the mantle's fluid phase; (2) garnets formed in the high-pressure/high-temperature
diamond-pyrope facies invariably contain significantly lower amounts of “water” than garnets formed under the conditions of
the graphite-pyrope facies. This latter result (2) may point to significantly lower f
H2O and f
O2 in the former as compared to the latter facies.
Received: 25 November 1997 / Accepted: 9 March 1998 相似文献
17.
Tomoo Katsura Sho Yokoshi Kazuyuki Kawabe Anton Shatskiy Maki Okube Hiroshi Fukui Eiji Ito Akifumi Nozawa Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(4):249-255
The electrical conductivity of (Mg0.93Fe0.07)SiO3 ilmenite was measured at temperatures of 500–1,200 K and pressures of 25–35 GPa in a Kawai-type multi-anvil apparatus equipped
with sintered diamond anvils. In order to verify the reliability of this study, the electrical conductivity of (Mg0.93Fe0.07)SiO3 perovskite was also measured at temperatures of 500–1,400 K and pressures of 30–35 GPa. The pressure calibration was carried
out using in situ X-ray diffraction of MgO as pressure marker. The oxidation conditions of the samples were controlled by
the Fe disk. The activation energy at zero pressure and activation volume for ilmenite are 0.82(6) eV and −1.5(2) cm3/mol, respectively. Those for perovskite were 0.5(1) eV and −0.4(4) cm3/mol, respectively, which are in agreement with the experimental results reported previously. It is concluded that ilmenite
conductivity has a large pressure dependence in the investigated P–T range. 相似文献
18.
The heat capacity of end-member titanite and (CaTiSiO5) glass has been measured in the range 328–938 K using differential scanning calorimetry. The data show a weak λ-shaped anomaly
at 483 ± 5 K, presumably associated with the well-known low-pressure P21/a ⇆ A2/a transition, in good agreement with previous studies. A value of 0.196 ± 0.007 kJ mol−1 for the enthalpy of the P21/a ⇆ A2/a transition was determined by integration of the area under the curve for a temperature interval of 438–528 K, bracketing
the anomaly. The heat capacity data for end-member titanite and (CaTiSiO5) glass can be reproduced within <1% using the derived empirical equations (temperature in K, pressure in bars):
The available enthalpy of vitrification (80.78 ± 3.59 kJ mol−1), and the new heat capacity equations for solid and glass can be used to estimate (1) the enthalpy of fusion of end-member
titanite (122.24 ± 0.2 kJ mol−1), (2) the entropy of fusion of end-member titanite (73.85 ± 0.1 J/mol K−1), and (3) a theoretical glass transition temperature of 1130 ± 55 K. The latter is in considerable disagreement with the
experimentally determined glass transition temperature of 1013 ± 3 K. This discrepancy vanishes when either the adopted enthalpy
of vitrification or the liquid heat content, or both, are adjusted.
Calculations using Eq. (2), new P−V−T data for titanite, different but also internally consistent thermodynamic data for anorthite,
rutile, and kyanite, and experimental data for the reaction: anorthite + rutile = titanite + kyanite strongly suggest: (1)
the practice to adjust the enthalpy of formation of titanite to fit phase equilibrium data may be erroneous, and (2) it is
probably the currently accepted entropy of 129.2 ± 0.8 J/mol K−1 that may need revision to a smaller value.
Received: 30 December 1999 / Accepted: 23 June 2000 相似文献
19.
V. M. Gurevich M. A. Ryumin A. V. Tyurin L. N. Komissarova 《Geochemistry International》2012,50(8):702-710
The heat capacity of gadolinium orthophosphate (GdPO4) measured in the temperature range 11.15–344.11 K by adiabatic calorimetry and available literature data were used to calculate its thermodynamic functions at 0–1600 K. At 298.15 K, these functions are as follows: C p 0(298.15 K) = 101.85 ± 0.05 J K−1 mol−1, S 0(298.15 K) = 123.82 ± 0.18 J K−1 mol−1, H 0(298.15 K)–H 0(0) = 17.250 ± 0.012 kJ mol−1, and Φ 0(298.15 K) = 65.97 ± 0.18 J K−1 mol−1 The calculated Gibbs free energy of formation from the elements of GdPO4 is Δ f G 0 (298.15 K) = −1844.3 ± 4.7 kJ mol−1. 相似文献
20.
Trapping and emission centres in X-irradiated natural zircon. characterization by thermoluminescence
In this paper, by the systematic compilation of results obtained with a series of natural zircons of various origins, we show that the thermoluminescence (TL) of natural zircons is characterized by two main peaks at 155±4 and 378±7 K. Other peaks are observed at 97±1, 219±3, 240±3, 267±6, 301±6, 343±5, 458±10, 518±4, and 556±7 K. Three kinds of emission are principally observed: 1) a 380–400 nm band; 2) a series of maxima located at 480, 580, 662 and 760 nm; 3) a 285 nm band. The comparison of these results with those obtained under similar conditions from synthetic zircons permits us to extend the interpretation of mechanisms involved in synthetic zircon TL to trapping and emission centres of natural zircons. In particular, we show that the three emissions above are due to 1) a host lattice mechanism, 2) Dy3+, 3) OH? groups, respectively. 相似文献