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  • Electronic Resource  (9)
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  • Electronic Resource  (9)
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 42 (1920), S. 237-239 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 42 (1920), S. 2531-2534 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 10 (1992), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The field relations from a quarry at Nuliyam, South India, illustrate dehydration of an amphibolite facies gneiss to granulite facies charnockite by CO2 influx, over a scale of 30 m. Both the calc-silicate source of the fluids and the full extent of their penetration into the gneiss are preserved in a continuous section. Fluid flow is by a hydraulic fracture mechanism, but is thought to be pervasive. The sharp reaction front predicted by the continuum mechanical theory for advective fluid transport is not observed. The front spreading is on too large a scale for either diffusive or dispersive control and is due to local kinetic disequilibrium between the fluid and rock, although the divariant nature of the reaction may also have a limited effect. The time-integrated fluid flux varies from the instantaneous porosity at the fluid front to 20 vol. % adjacent to the calc-silicate. Carbon isotope budgets suggest that decarbonation of the calc-silicate by a Rayleigh fractionation process provides a sufficient source for the CO2 influxing into the gneiss. Graphite abundances vary from 0.01 to 0.1% (by weight), it is principally derived by precipitation from the fluid and may be modelled from phase equilibria. Carbon isotope fronts coincide with the reaction front on the scale of sampling, although isotopic disequilibrium between graphite and inclusion-CO2 also implies local fluid-rock disequilibrium.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 11 (1993), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Incipient charnockite formation within amphibolite facies gneisses is observed in South India and Sri Lanka both as isolated sheets, associated with brittle fracture, and as patches forming interconnected networks. For each mode of formation, closely spaced drilled samples across charnockite/gneiss boundaries have been obtained and δ13C and CO2 abundances determined from fluid inclusions by stepped-heating mass spectrometry.Isolated sheets of charnockite (c.50 mm wide) within biotite–garnet gneiss at Kalanjur (Kerala, South India) have developed on either side of a fracture zone. Phase equilibria indicate low-pressure charnockite formation at pressures of 3.4 ± 1.0 kbar and temperatures of about 700°C (for XH2O= 0.2). Fluid inclusions from the charnockite are characterized by δ13C values of −8% and from the gneiss, 2 m from the charnockite, by values of −15%. The large CO2 abundances and relatively heavy carbon-isotope signature of the charnockite can be traced into the gneiss over a distance of at least 280 mm from the centre of the charnockite, whereas the reaction front has moved only 30 mm. This suggests that fluid advection has driven the carbon-isotope front through the rock more rapidly than the reaction front. The carbon-front/reaction-front separation at Kalanjur is significantly larger than the value determined from a graphite-bearing incipient charnockite nearby, consistent with the predictions of one-dimensional advection models.Incipient charnockites from Kurunegala (Sri Lanka) have developed as a patchy network within hornblende–biotite gneiss. CO2 abundances rise to a peak near one limb of the charnockite, and isotopic values vary from δ13C of c.−5.5% in the gneiss to −9.5% in the charnockite. The shift to lighter values in the charnockite can be ascribed to the formation of a CO2-saturated partial melt in response to influx of an isotopically light carbonic fluid.Thus, incipient charnockites from the high-grade terranes of South India and Sri Lanka reflect a range of mechanisms. At shallower structural levels non-pervasive CO2 influxed along zones of brittle fracture, possibly associated with the intrusion of charnockitic dykes. At deeper levels, in situ melting occurred under conditions of ductile deformation, leading to the development of patchy charnockites.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 12 (1994), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Granulite facies anorthosites on Holsenøy Island in the Bergen Arcs region of western Norway are transected by shear zones 0.1–100 m wide characterized by eclogite facies assemblages. Eclogite formation is related to influx of fluid along the shears at temperatures of c. 700d̀C and pressures in excess of 1.7 GPa. Combined carbon and nitrogen stable isotope, 40Ar/36Ar, trace-element and petrological data have been used to determine the nature and distribution of fluids across the anorthosite-eclogite transition.A metre-wide drilled section traverses the eclogitic centre of the shear into undeformed granulite facies garnet-clinopyroxene anorthosite. Clinozoisite occurs along grain boundaries and microcracks in undeformed anorthosite up to 1 m from the centre of the shear and clinozoisite increases in abundance as the edge of the shear zone is approached. The eclogite-granulite transition, marked by the appearance of sodic pyroxene and loss of albite, occurs within the most highly sheared section of the traverse. The jadeite-in reaction coincides with increased paragonite activity in mica. The separation between paragonite and clinozoisite reaction fronts can be semiquantitatively modelled assuming advective fluid flow perpendicular to the shear zone. The inner section of the traverse (0.25 m wide) is marked by retrogressive replacement of omphacite by plagioclase + paragonite accompanied by veins of quartz-phengite-plagioclase.C-N-Ar characteristics of fluid inclusions in garnet show that fluids associated with precursor granulite, eclogite and retrogressed eclogite are isotopically distinct. The granulite-eclogite transition coincides with a marked change in CO2 abundance and δ13C (〈36ppm, δ13C=-2% in the granulite; 〈180 ppm, δ13C=-10% in the eclogite). The distribution of Ar indicates mixing between influxed fluid (40Ar/36Ar 〉 25 times 103) and pre-existing Ar in the granulite (40Ar/36Ar 〈 8 times 103). δ15N values decrease from +6% in the anorthosite to +3% within the eclogite shear. The central zone of retrogressed eclogite post-dates shearing and is characterised by substantial enrichment of Si, K, Ba and Rb. Fluids are CO2-rich (δ13C ∼ -5%) with variable N2 and Ar abundances and isotopic compositions.Both Ar and H2O have penetrated the underformed granulite fabric more than 0.5m beyond the granulite/eclogite transition during eclogite formation. Argon isotopes show a mixing profile consistent with diffusion through an interconnecting H2O-rich fluid network. In contrast, a carbon-isotope front coincides with the deformation boundary layer, indicating that the underformed anorthosite was impervious to CO2-rich fluids. This is consistent with the high dihedral angle of carbonic fluids, and may be interpreted in terms of evolving fluid compositions within the shear zone.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 28 (1936), S. 522-526 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 15 (1923), S. 959-961 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 333 (1988), S. 167-170 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Incipient charnockites from southern India, which occur as veins and patches within biotite and amphibole gneiss, argue for a volatile-controlled transition from amphibolite-facies gneiss to arrested charnockite development8"11. The presence of grain-margin calcite8 and abundant CO2-rich fluid ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 108 (1991), S. 318-330 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Field evidence and fluid inclusion studies on South Indian incipient charnockites suggest that charnockite formation occurred during a decompressional brittle regime following the ‘peak’ of metamorphism and regional deformation. The most abundant type of inclusions in quartz and garnet grains in these charnockites contain high-density carbonic fluids, although lower-density fluids occur in younger arrays of inclusions. Discrete fluid inclusion generations optically are observed to decrepitate over well-defined temperature intervals, and quantitative measurements of CO2 abundance released from these inclusions by stepped thermal decrepitation show up to a four-fold increase (by volume) in the incipient charnockites relative to the adjacent gneisses from which they are derived. Studies based on optical thermometry, visual decrepitation and stepped-heating inclusion release together indicate that entrapment of carbonic fluids coincided with charnockite formation. We confirm that an influx of carbon dioxide-rich fluids is associated with the amphibolite-granulite transition, as recorded by the incipient charnockites, the remnants of which are commonly preserved as the earliest generation of high-density fluid inclusions.
    Type of Medium: Electronic Resource
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