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  • 1
    Electronic Resource
    Electronic Resource
    Reductive deposition of graphite at lithological margins in East Central Vermont: a Sr, C and O isotope study (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 20 (2002), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: O, Sr and C isotopes from east-central Vermont are used to provide information on the timing and volume of metamorphic fluid flow. The results are then used to assess the evidence for redox transformations between C species. Oxygen profiles are homogenised on a metre scale; comparison with Sr isotopes suggest that O alteration may have occurred over a significantly larger timescale than that of Sr, possibly because O was modified during dewatering and diagenesis in addition to the high temperature alteration recorded by strontium. Sr isotope distributions are consistent with cross-layer fluid fluxes of 104−106 moles m−2; absolute values depend on the Sr fluid-rock distribution coefficient which is poorly known; however, reaction progress constraints suggest that fluxes were towards the lower end of this range. High δ13C values observed at lithological boundaries cannot be explained by volume loss or closed system processes and are taken to indicate reductive precipitation of graphite as a result of mixing between CO2 and CH4-bearing fluids. Mass balance calculations indicate that redox reactions occurring under metamorphic conditions convert a minimum of 10% of the CO2 released from limestones into graphite, thus providing a potentially important control on the average residence time of C within the crust with implications for C cycling models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1525-1314.2002.00403.x
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  • 2
    Electronic Resource
    Electronic Resource
    Chloritoid and staurolite stability: implications for metamorphism in the Archaean Yilgarn Block, Western Australia (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 2 (1984), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The stability of quartz-chloritoid-staurolite-almandine-cordierite and aluminium silicates is used to constrain both metamorphic conditions and pressure-temperature trajectories for two localities within the 2700 Ma Archaean Yilgarn Block in Western Australia. Available experimental data are used to calculate thermodynamic data for a self-consistent set of equilibria between these minerals. A lower amphibolite facies locality from the margin of a lower strain area contains assemblages including quartz-chloritoid-staurolite-garnet-biotite with altered cordierite replacing chloritoid, quartz-staurolite-andalusite, and quartz-cordierite-andalusite-biotite. This locality was heated to 530–560°C in the andalusite field, at 4.2 kbar. A sample from a mid- to upper-amphibolite facies, highly strained locality contains relict staurolite enclosed by andalusite, in turn replaced by cordierite and muscovite with biotite and sillimanite in the matrix. The assemblage was heated isobarically from conditions near the maximum experienced by the lower grade locality of 560°C at 4.2 kbar to temperatures in excess of the andalusite-sillimanite transition but within the quartz plus muscovite stability field (600–650°C). The higher grade locality is close to a granitoid dome and sections based on gravity profiles reveal that this locality is underlain by granitoid at shallow depths. The higher grade metamorphism apparently reflects superposition of the thermal aureole on regional metamorphic conditions similar to those in the lower grade areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1984.tb00295.x
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  • 3
    Electronic Resource
    Electronic Resource
    An investigation of the relationship between bulk composition, inferred reaction progress and fluid-flow parameters for layered micaceous carbonates from Maine, USA (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 23 (2005), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Reaction progress exhibited by multivariant assemblages in micaceous limestones can provide an excellent record of metamorphic fluid flow. However, it is necessary to understand the sensitivity of these assemblages to bulk-composition parameters. Here, analysis of bulk composition on different scales and pseudosection construction are used to draw conclusions on relationships between bulk composition, fluid flow and reaction progress. Issues addressed include the effects of bulk composition on the mineralogical evolution of micaceous carbonates, the sensitivity of bulk composition to bulk-composition sampling methods, the magnitude of cross-layer fluid-composition gradients, the potential for metasomatism to drive reaction progress, and the relative timing of reaction in adjacent layers. Pseudosections successfully represent observed mineral assemblages, constrain the position of reactions in T–X(CO2) space, and allow assessment of the sensitivity of reaction position, inferred reaction progress and calculated fluid fluxes to uncertainties in bulk composition. The scale of bulk-composition sampling affects bulk compositions, calculated modes, predicted mineral assemblages and calculated fluid compositions. Larger samples record an average of different lithological subdomains, while point-count-derived bulk compositions are subject to uncertainties related to the small number of sample points. The optimum bulk composition for pseudosection purposes probably lies between measured bulk compositions. Results suggest that reaction progress in some extensively reacted layers was driven by infiltration of H2O-rich fluid which flowed or diffused parallel to layering, perpendicular to layering in response to fluid-composition gradients, and out of veins. Small variations in fluid composition across layering (ΔX(CO2) 〈 0.02) were maintained by internal buffering by the mineral assemblages. Internal buffering must also have driven samples up a sequence of narrow low-variance fields in T–X(CO2) space, and so reaction in adjacent layers must have close to simultaneous. Metasomatic effects on reaction progress are likely to have been small, so long as the porosity was low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2005.00571.x
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  • 4
    Electronic Resource
    Electronic Resource
    Mantle composition derived from the chemistry of ultramafic lavas (1976)
    [s.l.] : Nature Publishing Group
    Nature 263 (1976), S. 577-580 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. l Major and trace element compositions of ultramafic lavas rescaled to ignore the water content of the rock. The TiO2 against MgO graph illustrates the method of estimating mantle composition. Regression lines with MgO as the independent variable give liquid compositions at 22% and 32% MgO ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/263577a0
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  • 5
    Electronic Resource
    Electronic Resource
    Granite-greenstone terrains of the Rhodesian Archaean craton (1978)
    [s.l.] : Nature Publishing Group
    Nature 271 (1978), S. 23-27 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Granite-greenstone terrains of possibly three different ages exist in the Rhodesian Archaean craton. Their respective greenstone belts can be tentatively delineated across the central cratonic area. The main stratigraphic units of the youngest ( ∼ 2,700 Myr) and most widespread development can ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/271023a0
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  • 6
    Electronic Resource
    Electronic Resource
    Evolution of an active sea-floor massive sulphide deposit (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 668-671 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Hydrothermal circulation at oceanic spreading ridges causes sea water to penetrate to depths of 2 to 3 km in the oceanic crust where it is heated to ∼400 °C before venting at spectacular ‘black smokers’. These hydrothermal systems exert a strong influence on ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/29279
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  • 7
    Electronic Resource
    Electronic Resource
    The transport of heat and matter by fluids during metamorphism (1987)
    Springer
    Contributions to mineralogy and petrology 95 (1987), S. 384-392 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Non-dimensional solutions to the equations for the combined advective and diffusive one-dimensional transport of heat and solute in a layer are derived for fixed temperature/concentration on the boundaries and initial conditions of a linear gradient across the layer or a step function at the lower boundary. The solutions allow distinction of regimes in which advective or diffusive transport of either heat or solute predominate as a function of fluid flux, time and a length scale. The much lower diffusive coefficients for solute than heat results in a significant range of length scales and fluid flux rates characterised by advection of matter and diffusion of heat. The advective velocity of a component is a function of its fluid:rock partition coefficient. The most rapidly transported tracers which partition largely into the fluid phase, such as He, will travel orders of magnitude faster than heat or compatible solutes such as oxygen. Geochemical profiles in boundary layer regions where both advective and diffusive transport are significant are shown to be particularly informative as to properties of the rocks related to fluid flow such as porosity, permeability, time scales and fluid flux rates. The importance of advection can be directly estimated from the asymmetry of the geochemical profiles across individual layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371852
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  • 8
    Electronic Resource
    Electronic Resource
    The role of metamorphic decarbonation reactions in returning strontium to the silicate sediment mass (1994)
    [s.l.] : Nature Publishing Group
    Nature 367 (1994), S. 699-704 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The strontium-isotope evolution of the Earth's silicate sediments indicates that they must interact with a strontium reservoir whose 87Sr/86Sr ratio is relatively low. The Sr-isotope budget for these sediments can be balanced if the Sr lost to solution by ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/367699a0
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  • 9
    Electronic Resource
    Electronic Resource
    Calcite-dolomite geothermometry for iron-bearing carbonates (1977)
    Springer
    Contributions to mineralogy and petrology 59 (1977), S. 281-292 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The effect of the addition of iron on the calcite-dolomite solvus in the system CaCO3-MgCO3 is predicted from an approximate thermodynamic description of the systems CaCO3-MgCO3 and CaCO3-FeCO3. Coexisting calcites and dolomites in 15 samples from the Glockner area of the Tauern Window have been analysed to estimate metamorphic temperatures. These range from about 410 °C at the top of the Matrei Zone, on the southern margin of the Tauern Window, to about 490 °C at Hochtor in the centre of the Glockner Depression, implying a geothermal gradient of about 25 °C/km during metamorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374557
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  • 10
    Electronic Resource
    Electronic Resource
    A 3500 Ma plutonic and volcanic calc-alkaline province in the Archaean East Pilbara Block (1983)
    Springer
    Contributions to mineralogy and petrology 84 (1983), S. 25-35 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Variably foliated, predominantly granodioritic plutonic rocks from the northern part of the Shaw Batholith in the east Pilbara Archaean craton are dated at 3,499±22 Ma (2σ errors) by a whole-rock Pb-Pb isochron. These rocks intrude the surrounding greenstone sequence, and their age is indistinguishable from that sequence. High strain grey gneisses which occupy much of the western and southern Shaw Batholith are chemically and isotopically similar to the North Shaw suite and are inferred to have been derived from this suite by tectonic processes. Felsic volcanics within the greenstones together with a major portion of the granitic batholiths apparently formed in a calc-alkaline volcanic and plutonic province at ∼3,500 Ma. This volcanic and plutonic suite is similar to modern calc-alkaline suites on the basis of major element, rare earh element and most other trace element contents. The Archaean suite contrasts with modern equivalents only in having lower concentrations of HREE and higher concentrations of Ni and Cr. The average composition of the North Shaw suite is similar to that of Archaean gneiss belts for most elements and is consistent with the previously formulated hypothesis that the Shaw Batholith is transitional to the upper crustal level of a high-grade gneiss belt. Enrichment of the gneissic crust in the Shaw Batholith in alkali and heat-producing elements is inferred to have taken place by both igneous and hydrothermal processes over a protracted time interval. Late- and post-tectonic adamellite and granite melts intrude the gneissic rocks and there is isotopic evidence consistent with the gneisses being substantially enriched in Rb by pegmatite injection at ∼3,000 Ma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132327
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