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  • 1
    Electronic Resource
    Electronic Resource
    Rare earth element and gallium diffusion in yttrium aluminum garnet (1998)
    Springer
    Physics and chemistry of minerals 26 (1998), S. 156-163 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Diffusion of four rare-earth elements and gallium has been measured in yttrium aluminum garnet (YAG). Sources of diffusant were mixtures of alumina and rare-earth element oxides for REE diffusion, and mixtures of gallium and yttrium oxides for Ga diffusion. Diffusion profiles were measured with Rutherford backscattering spectrometry (RBS). For the rare-earth elements investigated, the following Arrhenius relations were obtained: DLa=6.87×10–1 exp (–582±21 kJ mol–1 /RT) m2s–1 DNd=1.63×10–1 exp (–567±15 kJ mol–1 /RT) m2s–1 DDy=2.70×100 exp (–603±35 kJ mol–1 /RT) m2s–1 DYb=1.50×10–2 exp (–540±26 kJ mol–1 /RT) m2s–1 Diffusion rates for the rare earths are quite similar, in contrast with trends noted for zircon. It is likely that these differences are a consequence of the relative ionic radii of the REE and the cations for which they substitute in the mineral lattice. For gallium, the following Arrhenius relation was determined: DGa=9.96×10–6 exp (–404±19 kJ mol–1 /RT) m2s–1 Gallium diffuses faster than the REE in YAG and has a smaller activation energy for diffusion. These data mirror relative trends in diffusion rates for YIG, in which trivalent cations occupying tetrahedral and octahedral sites (i.e., Al, Ga, Fe) diffuse faster than trivalent cations occupying dodecahedral sites (i.e., Y and the REE), and suggest that the rate-limiting process in the diffusion-controlled regime of solid-state creep of YAG is the diffusion of yttrium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050172
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion of lead in plagioclase and K-feldspar: an investigation using Rutherford Backscattering and Resonant Nuclear Reaction Analysis (1995)
    Springer
    Contributions to mineralogy and petrology 120 (1995), S. 358-371 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Chemical diffusion of Pb has been measured in K-feldspar (Or93) and plagioclase of 4 compositions ranging from An23 to An93 under anhydrous, 0.101 MPa conditions. The source of diffusant for the experiments was a mixture of PbS powder and ground feldspar of the same composition as the sample. Ruther ford Backscattering (RBS) was used to measure Pb diffusion profiles. Over the temperature range 700–1050° C, the following Arrhenius relations were obtained (diffusivities in m2s-1): Oligoclase (An23) : Diffusion normal to (001) :   log D=(−6.84±0.59)−[(261±13 kJ mol-1)/2.303RT ] Diffusion normal to (010):   log D=(−3.40±0.50)−[(355±11 kJ mol-1/2.303RT ] Andesine (An43): Diffusion normal to (001):   log D=(−6.73±0.54)−[(266±12 kJ mol-1)/2.303RT ] Diffusion normal to (010) appears to be only slightly slower than diffusion normal to (001) in andesine. Labradorite (An67): Diffusion normal to (001):   log D=(−7.16±0.61)−[(267±13 kJ mol-1)/2.303RT ] Diffusion normal to (010) is slower by 0.7  log units on average. Anorthite Diffusion normal to (010):   log D=(−5.43±0.48)−[(327±11 kJ mol-1)/2.303RT ] K-feldspar (Or93): Diffusion normal to (001):   log D=(−4.74±0.52)−[(309±16 kJ mol-1)/2.303RT ] Diffusion normal to (010):  log D=(−5.99±0.51)−[(302±11 kJ mol-1) /2.303RT ] In calcic plagioclase, Pb uptake is correlated with a reduction of Ca, indicating the involvement of Pb→Ca exchange in chemical diffusion. Decreases of Na and K concentrations in sodic plagioclase and K-feldspar, respectively, are correlated with Pb uptake and increase in Al concentration (measured by resonant nuclear reaction analysis), suggesting a coupled process for Pb exchange in these feldspars. These results have important implications for common Pb corrections and Pb isotope systematics. Pb diffusion in apatite is faster than in the investigated feldspar compositions, and Pb diffusion rates in titanite are comparable to both K-feldspar and labradorite. Given these diffusion data and typical effective diffusion radii for feldspars and accessory minerals, we may conclude that feldspars used in common Pb corrections are in general less inclined to experience diffusion-controlled Pb isotope exchange than minerals used in U-Pb dating that require a common Pb correction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050080
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusion of lead in plagioclase and K-feldspar: an investigation using Rutherford Backscattering and Resonant Nuclear Reaction Analysis (1995)
    Springer
    Contributions to mineralogy and petrology 120 (1995), S. 358-371 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Chemical diffusion of Pb has been measured in K-feldspar (Or93) and plagioclase of 4 compositions ranging from An23 to An93 under anhydrous, 0.101 MPa conditions. The source of diffusant for the experiments was a mixture of PbS powder and ground feldspar of the same composition as the sample. Rutherford Backscattering (RBS) was used to measure Pb diffusion profiles. Over the temperature range 700–1050°C, the following Arrhenius relations were obtained (diffusivities in m2s-1): Oligoclase (An23): Diffusion normal to (001): log D = ( − 6.84 ± 0.59) − [(261 ± 13 kJ mol −1)/2.303RT]Diffusion normal to (010): log D = ( − 3.40 ± 0.50) − [(335 ± 11 kJ mol −1)/2.303RT] Andesine (An43): Diffusion normal to (001): log D = ( − 6.73 ± 0.54) − [(266 ± 12 kJ mol −1)/2.303RT] Diffusion normal to (010) appears to be only slightly slower than diffusion normal to (001) in andesine. Labradorite (An67): Diffusion normal to (001): log D = ( − 7.16 ± 0.61) − [(267 ± 13 kJ mol −1)/2.303RT] Diffusion normal to (010) is slower by 0.7 log units on average. Anorthite Diffusion normal to (010): log D = ( − 5.43 ± 0.48) − [(327 ± 11 kJ mol −1)/2.303RT] K-feldspar (Or93): Diffusion normal to (001): log D = ( − 4.74 ± 0.52) − [(309 ± 16 kJ mol −1)/2.303RT] Diffusion normal to (010): log D = ( − 5.99 ± 0.51) − [(302 ± 11 kJ mol −1)/2.303RT] In calcic plagioclase, Pb uptake is correlated with a reduction of Ca, indicating the involvement of Pb→Ca exchange in chemical diffusion. Decreases of Na and K concentrations in sodic plagioclase and K-feldspar, respectively, are correlated with Pb uptake and increase in Al concentration (measured by resonant nuclear reaction analysis), suggesting a coupled process for Pb exchange in these feldspars. These results have important implications for common Pb corrections and Pb isotope systematics. Pb diffusion in apatite is faster than in the investigated feldspar compositions, and Pb diffusion rates in titanite are comparable to both K-feldspar and labradorite. Given these diffusion data and typical effective diffusion radii for feldspars and accessory minerals, we may conclude that feldspars used in common Pb corrections are in general less inclined to experience diffusion-controlled Pb isotope exchange than minerals used in U-Pb dating that require a common Pb correction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306513
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  • 4
    Electronic Resource
    Electronic Resource
    Diffusion of tetravalent cations in zircon (1997)
    Springer
    Contributions to mineralogy and petrology 127 (1997), S. 383-390 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Diffusion rates for the three tetravalent cations U, Th and Hf have been measured in synthetic zircon. Diffusant sources included oxide powders and ground pre-synthesized silicates. Rutherford backscattering spectrometry (RBS) was used to measure depth profiles. Over the temperature range 1400–1650 °C, the following Arrhenius relations were obtained (diffusion coefficients in m2sec−1): log D Th = (1.936 ± 0.9820) + (− 792 ± 34 kJ mol−1 /2.303 RT) log D U = (0.212 ± 2.440) + (− 726 ± 83 kJ mol−1 /2.303 RT) log D Hf = (3.206 ± 1.592) + (− 812 ± 54 kJ mol−1 /2.303 RT) The data show a systematic increase in diffusivity with decreasing ionic radius (i.e., faster diffusion rates for Hf than for U or Th), a trend also observed in our earlier study of rare earth diffusion in zircon. Diffusive fractionation may be a factor in the Lu-Hf system given the much slower diffusion rates of tetravalent cations when compared with the trivalent rare earths. The very slow diffusion rates measured for these tetravalent cations suggest that they are essentially immobile under most geologic conditions, permitting the preservation of fine-scale chemical zoning and isotopic signatures of inherited cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050287
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  • 5
    Electronic Resource
    Electronic Resource
    Pb diffusion in rutile (2000)
    Springer
    Contributions to mineralogy and petrology 139 (2000), S. 198-207 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Diffusion of Pb was measured in natural and synthetic rutile under dry, 1 atmosphere conditions, using mixtures of Pb titanate or Pb sulfide and TiO2 as the sources of diffusant. Pb depth profiles were then measured with Rutherford Backscattering Spectrometry (RBS). Over the temperature range 700–1100 °C, the following Arrhenius relation was obtained for the synthetic rutile: D=3.9 × 10−10exp(−250 ± 12 kJ mol−1/RT) m2s−1. Results for diffusion in natural and synthetic rutile were quite similar, despite significant differences in trace element compositions. Mean closure temperatures calculated from the diffusion parameters are around 600 °C for rutile grains of ∼100 μm size. This is about 100 °C higher than rutile closure temperature determinations from past field-based studies, suggesting that rutile is more resistant to Pb loss through volume diffusion than previously thought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00007671
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