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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogarnet substitution in pyrope: a possible location for ''water'' in the mantle
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 62 (1983), S. 208-214 
    Details
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0012-821X(83)90084-5
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical conductivity measurements on synthetic olivines and on olivine, enstatite and diopside from Dreiser Weiher, Eifel (Germany) under defined thermodynamic activities as a function of temperature and pressure
    Amsterdam : Elsevier
    Physics of the Earth and Planetary Interiors 25 (1981), S. 245-254 
    Details
    ISSN: 0031-9201
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0031-9201(81)90068-6
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental determination of the upper stability of scorzalite, FeAl2[OH/PO4]2, and the occurrence of minerals with a composition intermediate between scorzalite and lazulite(ss) up to the conditions of the amphibolite facies (1997)
    Springer
    Mineralogy and petrology 61 (1997), S. 211-222 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Das Stabilitätsfeld von Skorzalith (FeAl2[OH/PO4]2) wurde im P-T-Bereich zwischen 487 und 684 °C und zwischen 0.1 und 0.3 GPa in Hydrothermalexperimenten unter der Sauerstoffugazität des Ni/NiO-Puffers untersucht. Skorzalith zerfällt unter diesen Bedingungen gemäß der Reaktion: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (Berlinit) + H2O. Die Reaktionsenthalpie und -entropie für Standardbedingungen wurden zu ΔH R 0 = 94(13) kJ und ASR = 180(16) JK−1 bestimmt.57 Fe-Mößbaueruntersuchungen ergaben, daß ungefähr 4% des Gesamteisens in Skorzalith dreiwertig vorliegen.
    Notes: Summary The stability field of scorzalite (FeAl2[OH/PO4]2) was investigated in the P-T range from 487 to 684 °C and 0.1 to 0.3 GPa. in hydrothermal experiments. The oxygen fugacity was fixed by the Ni/NiO buffer. Scorzalite shows a decomposition according to the reaction: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (berlinite) + H2O. The mean standard enthalpy and standard entropy of reaction were determined as ΔH R 0 = 94(13) kJ, ASR = 180(16) JK−1. A57Fe-Mößbauer spectroscopic examination showed that about 4 atomic % of the total Fe in scorzalite is trivalent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172485
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  • 4
    Electronic Resource
    Electronic Resource
    P-T stability of the lazulite-scorzalite solid-solution series (2000)
    Springer
    Mineralogy and petrology 70 (2000), S. 55-71 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung P-T Stabilität von Lazulith-Scorzalith Mischkristallen Die Stabilität der Glieder der Lazulith-Scorzalith Mischkristallreihe, (Mg, Fe)Al2(OH)2(PO4)2 wurde als Funktion der Temperatur (505 bis 675 °C), des Druckes (0.1 bis 0.3 GPa) und des Fe/Mg-Verhältnisses in hydrothermalen Syntheseversuchen untersucht. Die Sauerstoffugazität wurde mittels eines Ni/NiO-Puffer kontrolliert. Es konnte festgestellt werden, daß ausgehend vom Lazulith-Endglied die Stabilität der Mischkristalle mit zunehmendem Scorzalith-Gehalt stark abnimmt. Reiner Lazulith, MgAl2(OH)2(PO4)2 zerfällt unter 0.2 GPa bei 660 °C, während ein Mischkristall mit 80 mol% Gehalt an Lazulith-Komponente nur bis 590 °C unter der Sauerstoffugazität des Ni/NiO-Puffers stabil ist. Hierbei koexistieren die Lazulith-Scorzalith Mischkristalle mit Grenzzusammensetzung mit eisenreicheren Mischphasen des Systems (Mg,Fe)Al(PO4)2O und Berlinit. Das Mischungsverhalten sowohl der Lazulith-Scorzalith- als auch der (Mg,Fe)Al(PO4)2O-Reihe wurde mit Hilfe eines quantitativen Modelles auf der Basis einer symmetrischen Mischung für Lazulith-Scorzalith und einer idealen Mischung für das System (Mg,Fe)Al(PO4)2O interpretiert. Mit Hilfe dieses Modelles wurde der Wechelwirkungsparameter , der die Nichtidealität der Lazulith-Scorzalith Mischreihe ausdrückt zu bestimmt.
    Notes: Summary The stability of members of the lazulite-scorzalite solid-solution series, (Mg,Fe)Al2 (OH)2(PO4)2, was investigated as a function of T (505 to 675 °C), P (0.1 to 0.3 GPa) and Fe/Mg ratio in hydrothermal synthesis experiments. The oxygen fugacity was controlled by means of the Ni/NiO buffer. It was found that starting from end-member lazulite the stability of the solid-solution members strongly decreases with increasing content of scorzalite component. At 0.2 GPa pure lazulite decomposes at about 660 °C whereas at the same pressure a solid-solution with 80% of lazulite component is only stable up to 590 °C under the oxygen fugacity of the Ni/NiO buffer. The members of the lazulite-scorzalite solid-solution series with limiting composition coexist with an Fe-richer member of the (Mg,Fe)Al(PO4)O series and berlinite. The mixing behaviour of both the lazulite-scorzalite and the (Mg,Fe)Al(PO4)O solid-solution series disregarding small amounts of Fe3+ is interpreted in terms of a model on the basis of a simple mixture for the lazulite-scorzalite system and of an ideal mixture for the (Mg,Fe)Al(PO4)O series. With this model the interaction parameter which expresses the non-ideality of the lazulite-scorzalite solid-solution series amounts to .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007100070013
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  • 5
    Electronic Resource
    Electronic Resource
    High temperature calorimetry of sulfide systems (1987)
    Springer
    Physics and chemistry of minerals 14 (1987), S. 52-57 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Enthalpies of solution of synthetic pentlandite Fe4.5Ni4.5S8, natural violarite (Fe0.2941Ni0.7059)3S4 from Vermillion mine, Sudbury, Ontario, synthetic pyrrhotite, FeS, synthetic high temperature NiS, synthetic vaesite, NiS2, synthetic pyrite, FeS2, Ni and Fe have been measured in a Ni0.6S0.4 melt at 1,100 K. Using these data and the standard enthalpies of formation of binary sulfides, given in literature, standard enthalpies of formation of pentlandite and violarite were calculated. The following values are reported: ΔH f o, Pent =−837.37±14.59 kJ mol−1 and ΔH f o, Viol =−378.02±11.81 kJ mol−1. While there are no thermo-chemical data for pentlandite with which our new value can be compared, an equilibrium investigation of stoichiometric violarite by Craig (1971) gives a significantly less negative enthalpy of formation. It is suggested that the difference may be due to the higher degree of order in the natural sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311148
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  • 6
    Electronic Resource
    Electronic Resource
    Calorimetric determination of the enthalpy of Mg-Fe ordering in orthopyroxene (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 220-224 
    Details
    ISSN: 1432-2021
    Keywords: Key words Enthalpy of ordering ; Mg-Fe-orthopyroxene ; Calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The enthalpy of Mg-Fe ordering in En50Fs50 orthopyroxene was measured using the transposed temperature drop calorimetric method. Heat effects associated with two consecutive drops were recorded. In the first drop, synthetic orthopyroxene samples equilibrated at 823 K, 0.1 MPa and a f O2 of the WI buffer were dropped from 823 K into the calorimeter, which was held at 1173 K. The measured heat effect corresponds to the enthalpy change due to the heat capacity of the sample from 823 to 1173 K and to the enthalpy associated with the (dis)ordering of Mg and Fe2+. In the second drop, the samples, with an Fe-Mg order corresponding to 1173 K, were dropped again from 823 to 1173 K. From the difference of the heat effects measured in the two experiments, the enthalpy of disordering associated with the temperature change from 823 to 1173 K was calculated to be −1.73±0.04 J mol−1. The observed enthalpy corresponds to a change in the mole fraction of iron on the M2 site, ΔX Fe,M2=−0.096 ± 0.001, which leads to of ΔH 0 exch of 18.0 ± 0.4 kJ mol−1 for the exchange reaction: The degree of Fe-Mg order was characterized by 57Fe Mössbauer resonance spectroscopy. In order to minimize the error due to the thickness of the absorber, the iron concentration of the absorber was reduced step by step from 5 to 1 mg Fe cm−2. The iron distribution extrapolated to zero thickness was used for the calculations of the enthalpy of exchange reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050010
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal chemical properties of synthetic lazulite–scorzalite solid-solution series (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 496-505 
    Details
    ISSN: 1432-2021
    Keywords: Key words Phosphate minerals ; Lazulite ; Scorzalite ; Solid-solution ; 57Fe-Mössbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Members of the lazulite–scorzalite (MgAl2- (PO4)2(OH)2-FeAl2(PO4)2(OH)2) solid-solution series were synthesized in compositional steps of 12.5 mol% at T = 485 °C and P = 0.3 GPa under hydrothermal conditions and controlled oxygen fugacities of the Ni/NiO-buffer. X-ray powder diffraction and 57Fe-Mössbauer studies show that under these conditions a complete solid-solution series is formed which is characterized by the substitution of Mg2+ and Fe2+ on the octahedral Me 2+ site. The 57Fe-Mössbauer spectra which reveal the presence of both ferrous and ferric iron and the compositional data were interpreted in terms of a defect model with a distribution of the ferric ions over both the Me 2+ and the Al3+ positions and vacancies on the Me 2+ site. The 57Fe-Mössbauer parameters of the synthetic compounds correspond to those of natural lazulites except for the total absorption ratio of the ferric iron A(Fe3+)/(A(Fe3+)+A(Fe2+)), which is significantly higher in natural lazulites of the same composition. The total absorption ratio of the ferric iron increases from 4% in pure scorzalite to 15% in a Mg-rich solid-solution with x Fe  = 12(1)%
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050212
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  • 8
    Electronic Resource
    Electronic Resource
    Impedance spectroscopy and defect chemistry of fayalite (1996)
    Springer
    Physics and chemistry of minerals 23 (1996), S. 186-192 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Impedance spectra of polycrystalline synthetic fayalite were measured at 900°C and 1 atm pressure in a CO/CO2 gas mixing furnace at oxygen fugacities f O 2=10-13 to 10-17 atm. The frequency range applied to the samples was 20 Hz–1 MHz. The spectra show two semicircular arcs, which are attributed to polarization processes within the bulk material and at the sample-electrode interface. Two different types of behaviour of the bulk resistance as a function of oxygen fugacity were observed. The first is proportional to the -1/4.5 to -1/6 power of fI 2, which is consistent with the existing defect model. The second shows a lesser dependence on fO 2, often lowered by a factor of about two, relative to the expected value, resulting in a resistance proportional to the -1/10 to -1/12 power of fO 2. It is assumed, that the lesser f O 2-dependence is caused by aliovalent impurities, producing an fO 2-independent amount of charge carriers. The electrode arcs show a resistance proportional to the-1/2 to -1/4 power of oxygen fugacity, implying that a reaction with the gas phase is involved in the polarization process at the sample-electrode interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220729
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  • 9
    Electronic Resource
    Electronic Resource
    High temperature calorimetry of sulfide systems (1988)
    Springer
    Physics and chemistry of minerals 16 (1988), S. 172-179 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The standard enthalpies of formation of FeS (troilite), FeS2 (pyrite), Co0.9342S, Co3S4 (linnaeite), Co9S8 (cobalt pentlandite), CoS2 (cattierite), CuS (covellite), and Cu2S (chalcocite) have been determined by high temperature direct reaction calorimetry at temperatures between 700 K and 1021 K. The following results are reported: $$\Delta {\rm H}_{f,FeS}^{tr} = - 102.59 \pm 0.20kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,FeS}^{py} = - 171.64 \pm 0.93kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_{0.934} S} = - 99.42 \pm 1.52kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_9 S_8 }^{ptl} = - 885.66 \pm 16.83kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_3 S_4 }^{In} = - 347.47 \pm 7.27kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,CoS_2 }^{ct} = - 150.94 \pm 4.85kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Cu_2 S}^{cc} = - 80.21 \pm 1.51kJ mol^{ - 1} ,$$ and $$\Delta {\rm H}_{f,CuS}^{cv} = - 53.14 \pm 2.28kJ mol^{ - 1} ,$$ The enthalpy of formation of CuFeS2 (chalcopyrite) from (CuS+FeS) and from (Cu+FeS2) was determined by solution calorimetry in a liquid Ni0.60S0.40 melt at 1100 K. The results of these measurements were combined with the standard enthalpies of formation of CuS, FeS, and FeS2, to calculate the standard enthalpy of formation of CuFeS2. We found $$\Delta {\rm H}_{f,CuFeS_2 }^{ccp} = - 194.93 \pm 4.84kJ mol^{ - 1}$$ . Our results are compared with earlier data given in the literature; generally the agreement is good and our values agree with previous estimates within the uncertainties present in both.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203201
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  • 10
    Electronic Resource
    Electronic Resource
    Electrical conductivity measurements on olivines Mg2SiO4-Fe2SiO4 under defined thermodynamic conditions (1980)
    Springer
    Physics and chemistry of minerals 6 (1980), S. 95-107 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The isobaric (P=10 kb) temperature dependence of the electrical conductivities of forsterite, fayalite and forsterite-fayalite mixed crystals was measured with special regard to the thermodynamics of point defects in these minerals. Measurements, taken at increasing and decreasing temperature, were performed on synthetic powders of the following compositions: Fo 100/Fa 0, Fo 90/Fa 10, Fo 80/Fa 20, Fo 60/Fa 40, and Fo 0/Fa100. Control of oxygen partial pressure was achieved with solid state buffers (Fa/Q/M, Fa/Q/I, and Fe/FeO). Activities of the binary components were controlled by equilibrating the sample with its neighbouring phases. All values for σ, obtained with controlled pO2 and fixed activities of the binary components, agree well upon either heating or cooling. From the gradient of lg σ vs. 1/T plots, the following activation energies were estimated: 2,461 eV (970°–1075°C) and 0.984 eV (522°–970°C) for Fo 100/Fa 0 equilibrated with MgO; 0.777 eV and 0.683 eV for Fo 90/Fa 10 and Fo 80/Fa 20 equilibrated with enstatite and pO2 controlled by Fe/FeO buffer; 0.622 eV, 0.528 eV, and 0.479 eV for Fo 90/Fa 10, Fo 80/Fa 20, and Fo 60/Fa 40 equilibrated with enstatite and pO2 controlled by Fa/Q/M buffer; and 0.524 eV and 0.383 eV for Fo 0/Fa 100 equilibrated with Q/I and Q/M respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311048
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