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  • 1
    Electronic Resource
    Electronic Resource
    40 Ar retention in the terrestrial planets (2007)
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 299-304 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The solid Earth is widely believed to have lost its original gases through a combination of early catastrophic release and regulated output over geologic time. In principle, the abundance of 40Ar in the atmosphere represents the time-integrated loss of gases from the interior, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06144
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  • 2
    Electronic Resource
    Electronic Resource
    A diffusion mechanism for core–mantle interaction (2007)
    [s.l.] : Nature Publishing Group
    Nature 450 (2007), S. 709-711 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Understanding the geochemical behaviour of the siderophile elements — those tending to form alloys with iron in natural environments — is important in the search for a deep-mantle chemical ‘fingerprint’ in upper mantle rocks, and also in the evaluation of models of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06380
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusion in fluid-bearing and slightly-melted rocks: experimental and numerical approaches illustrated by iron transport in dunite (1991)
    Springer
    Contributions to mineralogy and petrology 107 (1991), S. 417-434 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Bulk diffusion of iron in synthetic dunites containing 1–6 vol.% fluid or melt at 10 kbar (1 GPa) and 900°–1300° C was examined by encapsulating the samples in platinum, which served as a sink for iron. The rate of iron loss from the dunite was found to depend strongly upon the identity of the fluid, which was varied from CO2 and H2O to melts of basaltic and sodium carbonate composition. Carbon dioxide in amounts up to 4 vol.% has no effect upon bulk iron diffusion because it exists in the dunite are isolated pores. The interconnected nature of H2O, basaltic melt, and carbonate melt, on the other hand, results in marked enhancement of bulk-rock Fe diffusion that is correlated with the diffusivity and solubility of olivine components in the fluid. At 1300° C, 4–5 vol.% of either water or basaltic melt increases the effective bulk diffusivity from the fluidabsent value of ≈10-10 cm2/s to ≈10-8 cm2/s. A single experiment involving a similar volume fraction of carbonate melt yielded a minimum bulk diffusivity of 10-7–10-6 cm2/s. This remarkably high value is attributable to the concurrent high diffusivity and high solubility of olivine components in molten carbonate H2O has a high diffusivity, estimated at ≈10-4 cm2/s in this study, and basaltic melt can dissolve large amounts of olivine, but neither possesses these two qualities in combination. Bulk transport of Fe in dunite containing 〈2 vol.% of pure H2O is independent of olivine grain size for samples having an average grain diameter of 〈10 μm to ≈60 μm. This is probably because bulk diffusion specifically in these H2O-bearing samples is ratelimited by the flux (which is proportional to concentration) of olivine components in the fluid. Given a constant fluid volume fraction, the effect of reducing the grain size is to increase the number of fluid-filled channels, but at the same time to decrease their average aperture, thus keeping constant the cross-sectional area through which the diffusional flux occurs. (Independence of bulk diffusivity from grain size is not anticipated for rocks containing melt, in which the silicate components are much more soluble.) In numerical (finite difference) simulations of selected laboratory experiments, the bulk Fe transport process was modeled as diffusion in fluid-filled tubules of triangular cross-section that are supplied by volume diffusion from contacting olivine grains with which they are in surface equilibrium. Applying a tortuosity factor of 1.7 brings the numerically computed diffusional loss profiles for experiments containing basaltic melt into near-coincidence with the experimentally-determined curves. This success in reproducing the experimental results lends credence to the interpretation of the bulk diffusional loss profiles as composites of gradients due to volume, grain-boundary and fluid-phase diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310677
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  • 4
    Electronic Resource
    Electronic Resource
    Inclusion/host relations involving accessory minerals in high-grade metamorphic and anatectic rocks (1989)
    Springer
    Contributions to mineralogy and petrology 101 (1989), S. 220-231 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In general, accessory minerals are expected to participate in partial fusion of their host rocks to a degree determined simply by their solubilities in the melt. The possibility must be recognized, however, that a given accessory grain may be physically isolated from the melt by inclusion within a residual major mineral. Because of the importance of accessory minerals to crustal-rock trace element and isotope geochemistry, and because of their common existence as inclusions in major phases, we undertook an evaluation of the factors that affect inclusion formation during ultrametamorphism. Three approaches are taken: 1) a review of interfacial energy considerations is used to show that the free energy of the system is lowered by location of accessory minerals at major-phase grain perimeters, and that the magnitude of this effect is proportional to the square of the accessory grain radius; 2) annealing and partial melting experiments (1000° C, 10 and 15 kbar) on rock analogs are described, and the results are shown to confirm the predicted tendency of accessory minerals to occupy grain boundaries; and 3) the results of a study of accessory phase (rutile and zircon) distribution in a migmatite from the Tibetan slab are reported, again in confirmation of the prediction that accessories tend to be situated at majorphase grain perimeters. The latter two aspects of the study reveal that, although included accessory grains are common, their generally small size results in only a minor contribution to the bulk-rock budget of accessory mineral components: Most of the mass of these components is contained within populations of generally larger accessory grains located at major-phase grain boundaries. Accordingly, the assumption that accessory minerals are involved in crustal melting is generally valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375308
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  • 5
    Electronic Resource
    Electronic Resource
    Erratum (1989)
    Springer
    Contributions to mineralogy and petrology 102 (1989), S. 255-255 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375346
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  • 6
    Electronic Resource
    Electronic Resource
    Two-liquid partition coefficients: Experimental data and geochemical implications (1976)
    Springer
    Contributions to mineralogy and petrology 56 (1976), S. 119-134 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Partition coefficients for Cs, Ba, Sr, Ca, Mg, La, Sm, Lu, Mn, Ti, Cr, Ta, Zr, and P between immiscible basic and acidic liquids in the system K2O-Al2O3-FeO-SiO2 were experimentally determined at 1,180 °C and 1 atm. Phosphorus is most strongly enriched in the basic melt (by a factor of 10), followed by rare earth elements, Ta, Ca, Cr, Ti, Mn, Zr, Mg, Sr, and Ba (enriched by a factor of 1.5). Of the elements studied, only Cs is enriched in the acidic melt. The two-liquid partition coefficients of Zr, Ta, Sm, and Mn are constant for concentrations ranging from 〈0.1% to as high as 1 wt.-%, suggesting that Henry's law is applicable in silicate melts (at least for these elements) to concentrations well above typical trace element levels in rocks. The strong relative preference of many elements for the basic melt implies that the structural characteristics of basic melts more readily permit stable coordination of cations by oxygen. Partitioning of elements between crystal and liquid in a magma must therefore be influenced by the composition (and consequent structure) of the liquid. Application of the two-liquid partition coefficients to possible occurrences of liquid immiscibility in magmas reveals that typical basalt-rhyolite associations are probably not generated by two-liquid phase separation. However, liquid immiscibility cannot be discounted as a possible origin for lamprophyric rocks containing felsic segregations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375424
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  • 7
    Electronic Resource
    Electronic Resource
    Zircon saturation in felsic liquids: Experimental results and applications to trace element geochemistry (1979)
    Springer
    Contributions to mineralogy and petrology 70 (1979), S. 407-419 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Hydrothermal experiments were carried out at 2 kbar water pressure, 700 °–800 ° C, with the objective of determining the level of dissolved Zr required for precipitation of zircon from melts in the system SiO2-Al2O3-Na2O-K2O. The saturation level depends strongly upon molar (Na2O + K2O)/Al2O3 of the melts, with remarkably little sensitivity to temperature, SiO2 concentration, or melt Na2O/ K2O. For peraluminous melts and melts lying in the quartz-orthoclase-albite composition plane, less than 100 ppm Zr is required for zircon saturation. In peralkaline melts, however, zircon solubility shows pronounced, apparently linear, dependence upon (Na2O + K2O)/Al2O3, with the amount of dissolvable Zr ranging up to 3.9 wt.% at (Na2O + K2O)/Al2O3 = 2.0. Small amounts (1 wt.% each) of dissolved CaO and Fe2O3 cause a 25% relative reduction of zircon solubility in peralkaline melts. The main conclusion regarding zirconium/zircon behavior in nature is that any felsic, non-peralkaline magma is likely to contain zircon crystals, because the saturation level is so low for these compositions. Zircon fractionation, and its consequences to REE, Th, and Ta abundances must, therefore, be considered in modelling the evolution of these magmas. Partial melting in any region of the Earth's crust that contains more than ∼ 100 ppm Zr will produce granitic magmas whose Zr contents are buffered at constant low (〈 100 ppm) values; unmelted zircon in the residual rock of such a melting event will impart to the residue a characteristic U- or V-shaped REE abundance pattern. In peralkaline, felsic magmas such as those that form pantellerites and comendites, extreme Zr (and REE, Ta) enrichment is possible because the feldspar fractionation that produces these magmas from non-peralkaline predecessors does not drive the melt toward saturation in zircon. Zircon solubility in felsic melts appears to be controlled by the formation of alkali-zirconosilicate complexes of simple (2:1) alkali oxide: ZrO2 stoichiometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371047
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  • 8
    Electronic Resource
    Electronic Resource
    Monazite solubility and dissolution kinetics: implications for the thorium and light rare earth chemistry of felsic magmas (1986)
    Springer
    Contributions to mineralogy and petrology 94 (1986), S. 304-316 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A series of monazite dissolution experiments was conducted in a hydrous (1–6 wt.%) granitic melt at 8 kbar over the temperature range 1,000–1,400° C. A polished cube of monazite was immersed in a natural obsidian melt and allowed to partially dissolve. Electron microprobe traverses perpendicular to the crystal-melt interface revealed concentration gradients in the LREEs and P. Diffusivities of the LREEs and P were calculated from these profiles, yielding the following Arrhenius relations for the LREEs: D=0.23 exp(−60.1 kcal mol−1/RT) at 6% water D=2.30×107 exp(−122.1 kcal mol−1/RT) at 1% water These results demonstrate the importance of dissolved water on REE diffusion. Phosphorus diffusivities are nearly identical to those of the rare-earths, suggesting that P diffusion charge-compensates REE diffusion. The concentration of LREEs required for monazite saturation in these melts is given by the level of dissolved LREEs at the crystal-melt interface. These values also show a dependence on dissolved water, with LREEsat=60 ppm at 6% H2O when extrapolated down to 700° C, and LREEsat=30 ppm at 1% H2O. Calculated dissolution rates based on the above parameters indicate that minute (〈30 μm diameter) monazite crystals will be readily digested by an enclosing anatectic magma under reasonable geologic conditions (i.e., T=700–800° C and 〉2% H2O), whereas larger (〉 50 μm) crystals will likely be residual over the duration of an anatectic event. The low solubility of monazite in this melt suggests that the LREE depletion observed in some felsic differentiation suites may be the result of monazite crystallization. Limited experimental and geochemical/petrologic evidence indicates that compositional changes in the melt accompanying differentiation decrease the solubility of monazite drastically. Kinetic and chemical constraints may also lead to localized monazite saturation and inclusion in major phases or even other accessories. Variations in the REE composition of monazite from different parageneses probably reflects the REE pattern of the parent melt, and may be due to gradational differences in the stability of individual or subgroup REE-complexes as a function of melt composition. Particularly important in this regard seems to be the lime+alkali/alumina balance of the melt and its volatile content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371439
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  • 9
    Electronic Resource
    Electronic Resource
    Convection in multicomponent silicate melts driven by coupled diffusion (1994)
    [s.l.] : Nature Publishing Group
    Nature 369 (1994), S. 390-392 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Multicomponent convection due to diffusive coupling (represented below by off-diagonal terms in the diffusion matrix) is demonstrated using experiments in the system CaO-Al2O3-SiO2 at 1,500 °C and 10 kbar. The experimental design we used for both interdiffusion and convection experiments ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/369390a0
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  • 10
    Electronic Resource
    Electronic Resource
    Rutile solubility and mobility in supercritical aqueous fluids (1993)
    Springer
    Contributions to mineralogy and petrology 114 (1993), S. 321-330 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Experimental and thermodynamic data and the apparent immobility of Ti under metamorphic conditions suggest that rutile is very insoluble in aqueous fluids at upper crustal conditions. New solubility measurements at 1.0–2.93 GPa and 800–1200°C show, however, that under certain pressure and temperature conditions rutile is quite soluble in H2O. Solubilities were estimated from the measured weight loss of a single crystal equilibrated with a known mass of fluid in a piston cylinder apparatus. Measured solubilities in H2O range from 0.15 wt% (wt loss crystal/wt fluid) at 2.93 GPa and 1000°C to 1.9% at 1.0 GPa and 1100°C. Solubility increases with increasing temperature and with decreasing pressure in a manner given by the following fit to the experimental data: $$\log _{10} m_{Ti} = - 7049/T - (0.589* P)/T + 5.14$$ wherem Ti is the molality of Ti in the fluid,T is in degress Kelvin andP is in MPa. The effect of fluid composition on rutile solubility was also examined at 1.0 GPa and 1000°C for H2O-CO2, 1m NaCl, and 1m HF fluids. Kesults suggest that solubility depends on the mole fraction of H2O in the fluid but is independent of ionic strength and fluid pH. This behavior implies that Ti dissolves as the neutrally-charged hydrolysis product Ti(OH)4. The free energy of this species was calculated for each set of experimental conditions. TheP-T dependence of rutile solubility suggests that aqueous fluids derived from subducted oceanic lithosphere would dissolve rutile or other Ti-rich minerals from the deepest portion of the mantle wedge and precipitate them at higher levels. Subsequent melting of the base of the mantle wedge would form HFSE-depleted IAB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046535
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