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  • 1
    Electronic Resource
    Electronic Resource
    New constraints on metamorphism in the Rauer Group, Prydz Bay, east Antarctica (2003)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 21 (2003), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Granulite facies metapelites of the Mather and Filla Paragneisses within the Rauer Group, east Antarctica, possess markedly different compositions. The metamorphic evolution of the two metapelite types has been interpreted as temporally distinct, with the Rauer Group preserving at least two distinct granulite facies tectonothermal episodes. Calculated P–T pseudosections and orthopyroxene Al content indicate the revised maximum-preserved P–T conditions within the Mather Paragneiss to lie in the vicinity of 950–975 °C and 10–10.6 kbar, less extreme than previous estimates. The range of possible P–T paths for the Mather Paragneiss consistent with mineral textural relationships and pseudosections contoured for mineral proportion are significantly shallower (dP/dT) than previous estimates. A near-isothermal decompression P–T path, and extreme peak metamorphic conditions, are not necessary to explain the development of preserved mineral reaction textures. The Filla Paragneiss contains pelitic assemblages less amenable to rigorous quantitative analysis. Nevertheless, possibilities for the shared or otherwise metamorphic evolution of the Mather and Filla Paragneisses may be postulated on the basis of calculated pseudosections in the context of existing geochronology for the Rauer Group and preserved microstructures. A shared evolution, most likely during Pan-African granulite facies metamorphism, is plausible and consistent with mineral assemblage development, geochronology and microstructures. A revised interpretation of the Rauer Group's preserved metamorphic evolution may warrant the revision of existing tectonic models, applicable also to the remainder of Prydz Bay. More generally, the employed approach may incite a revision of peak P–T and P–T paths in other granulite facies terranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1525-1314.2003.00476.x
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  • 2
    Electronic Resource
    Electronic Resource
    Partial melting during tectonic exhumation of a granulite terrane: an example from the Larsemann Hills, East Antarctica (1997)
    Oxford, UK : Blackwell Science Ltd.
    Journal of metamorphic geology 15 (1997), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Anatectic migmatites in medium- to low-pressure granulite facies metasediments exposed in the Larsemann Hills, East Antarctica, contain leucosomes with abundant quartz and plagioclase and minor interstitial K-feldspar, and assemblages of garnet–cordierite–spinel–ilmenite–sillimanite. Qualitative modelling in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2, in conjunction with various P–T  calculations indicate that the high-grade retrograde evolution of the terrane was dominated by decompression from peak conditions of c. 7 kbar at c. 800 °C to 4–5 kbar at c. 750 °C. Extensive partial melting during decompression involved the replacement of biotite by the assemblage cordierite–garnet–spinel within the leucosomes. These leucosomes represent the site of partial melt generation, the cordierite–garnet–spinel–ilmenite assemblage representing the solid products and excess reactants from the melting reaction. The extraction and accumulation of this decompression-generated melt led to the formation of syntectonic pegmatites and extensive granitic plutons. Leucosome development and terrane decompression proceeded during crustal transpression, synchronous with upper crustal extension, during a progressive Early Palaeozoic collisional event. Subsequent retrograde evolution was characterized by cooling, as indicated by the growth of biotite replacing spinel and garnet, thin mantles of cordierite replacing spinel and quartz within metapelites, and garnet replacing orthopyroxene and hornblende within metabasites. P–T calculations on late mylonites indicate lower grade conditions of formation of c. 3.5 kbar at c. 650 °C, consistent with the development of late cooling textures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1997.00059.x
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  • 3
    Electronic Resource
    Electronic Resource
    Metapelitic granulites from Jetty Peninsula, east Antarctica: formation during a single event or by polymetamorphism? (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 12 (1994), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Granulite facies metasedimentary gneiss exposed on Jetty Peninsula, east Antarctica, contains assemblages involving garnet-sillimanite-biotite-cordierite-spinel-ilmenite-rutile and garnet-orthopyroxene-cordierite-biotite, as well as quartz and K-feldspar. Peak assemblages involve garnet + sillimanite + ilmenite (±rutile) and garnet + orthopyroxene. P-T calculations suggest formation conditions of approximately 800d̀ C at 7-7.5 kbar. Cooling from peak conditions is suggested by biotite + garnet (±sillimanite) overprinting some peak assemblages. A subsequent increase in temperature is inferred from the formation of cordierite + garnet + biotite + ilmenite, garnet + sillimanite + cordierite + ilmenite and cordierite + orthopyroxene assemblages during D2. In slightly zincian bulk compositions, hercynitic spinel + cordierite + sillimanite constitutes the peak D2 assemblage. Average pressure calculations indicate peak pressures of 5.9 ±0.4 kbar at 700d̀ C for the cordierite-bearing D2 assemblages. Available radiometric data suggest that peak metamorphism occurred at c. 1000 Ma and D2 occurred after 940 ± 20 Ma. The following two possibilities exist for the metamorphic evolution. (1) The formation of the lower pressure cordierite-bearing assemblages is associated with a separate metamorphic event (M2), unrelated to the peak assemblage (M1), and the lower pressure assemblages have no relevance in terms of a single tectonothermal event. (2) The cordierite-bearing assemblages formed during a progression from peak conditions. In this case, the lower pressure assemblages reflect a broadly decompressional metamorphic evolution, during which temperatures fluctuated. Comparison with P-T paths from granulites of similar age in adjacent areas suggests that the second possibility should be preferred. The cooling interval between peak conditions and the development of cordierite-bearing coronas and symplectites suggests affinities with isobarically cooled granulites of similar age immediately to the west, and the low-P/high-T post-peak conditions are similar to the later stages of decompressional paths recognized in much of east Antarctica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1994.tb00042.x
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  • 4
    Electronic Resource
    Electronic Resource
    Early Cambrian crustal shortening and a clockwise P–T–t path from the southern Prince Charles Mountains, East Antarctica: implications for the formation of Gondwana (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: Cambrian orogenesis (550–490 Ma) in the Lambert Province of the southern Prince Charles Mountains resulted in three successive stages of deformation. The earliest of these deformations resulted in the development of a layer-parallel foliation (S1) that was folded into macro-scale recumbent folds (F2). Subsequent deformation buckled the rocks into long-wavelength (c. 20 km), SW- to NW-trending antiformal closures (F3) mostly separated from each other by west to SW trending, steeply dipping, high-strain zones. Metapelitic rocks from the region are divisible into two compositional types: a high-Al, -Fe and -K type and a high-Mg, -Ca and -Na type. In rocks of both composition, relic staurolite preceded the formation of upper amphibolite facies garnet + biotite + sillimanite ± muscovite mineral assemblages that record peak pressures and temperatures of c. 650–700 °C and 6–7 kbar. Subsequent decompression of c. 3 kbar is implied from texturally late plagioclase and a reduction in the modal abundance of garnet in the high-Al, -Fe and -K metapelites, and from texturally late cordierite in the more magnesium rocks. This clockwise P–T–t path, with prograde heating followed by rapid decompression, is: (i) equivalent to that recorded in the same-aged rocks at Prydz Bay located 600 km to the north, and (ii) similar to the modelled response of the crust to thickening following continent–continent collision. These results indicate that large areas of East Antarctica were thickened and rapidly exhumed, probably in response to collisional orogenesis during the Early Cambrian. This supports the inference that Early Cambrian orogenesis in the Prydz Bay–Prince Charles Mountains region of East Antarctica marks one of the fundamental lithospheric boundaries within Gondwana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2005.00598.x
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  • 5
    Electronic Resource
    Electronic Resource
    Contact metamorphism around the Stawell granite, Victoria, Australia (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 12 (1994), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The contact metamorphosed metapelitic and metapsammitic rocks surrounding the Stawell granite, western Victoria, Australia, are divided into three zones: the low-grade zone, the medium-grade zone and the high-grade zone. Detailed petrological study shows consistency of element distributions, implying that equilibrium was widely attained in the rocks, although equilibrium volumes are generally small (millimetre scale) and considerable mineral chemical variations exist between adjacent domains. The metamorphic mineral assemblages are generally of high variance (KFMASH variance ≤ 2). Consequently, the chemical evolution of assemblages is controlled largely by bulk composition and metamorphic temperature, the former factor being more important in most rocks. The chemographic relations of mineral assemblages in low- and medium- to high-grade zones are presented in compatibility diagrams projected from biotite, quartz and H2O, and biotite, K-feldspar and H2O, respectively. These compatibility diagrams have the advantage of showing both quartz-bearing and quartz-absent assemblages. The metamorphic reactions are modelled successfully by a calculated petrogenetic grid that combines both KFASH and KMASH equilibria. Based on petrographic observations and with constraints from the calculated petrogenetic grid, the following KFMASH reactions, in the order of increasing metamorphic grade, are responsible for producing the various mineral assemblages in the Stawell rocks:chl + mu + q = bi + cd + V,chl + q + cd = g + V,mu + bi + q = ksp + cd + V,mu + q = ksp + and + cd + V (or KASH mu + q = ksp + and + V),mu + cd = ksp + and + bi + V,mu + bi + and = ksp + sp + V,and + bi = ksp + sp + cd + V,mu + bi = ksp + cor + sp + V,mu = ksp + cor + and + sp + V (or KASH mu = ksp + cor + V),bi + cd + q = g + ksp + V.The combined KFASH and KMASH grid provides constraints on reaction coefficients in the above sequence of reactions and on temperature and pressure of metamorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1994.tb00046.x
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental folding in ice and the resultant c -axis fabrics (1979)
    [s.l.] : Nature Publishing Group
    Nature 279 (1979), S. 49-51 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. l a, An isotropic block of fine-grained ice with circular strain markers, b, The isotropic sample after 21% shortening and the strain markers are now ellipses, c, The planar fine- and medium-grained layers in the anisotropic block, separated by the films of frozen water, d, The anisotropic ice ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/279049a0
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  • 7
    Electronic Resource
    Electronic Resource
    Uranium and boron distributions related to metamorphic microstructure-evidence for metamorphic fluid activity (1981)
    Springer
    Contributions to mineralogy and petrology 76 (1981), S. 24-32 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The distribution of uranium and boron in polymetamorphosed, granulite facies schists and gneisses has been studied using particle track methods. The concentration and distribution of these elements when examined in relation to mineralogy and microstructure provide an insight into: (1) the behaviour of U and B in metamorphism, (2) the activity of a fluid phase in the metamorphic processes and (3) the nature of chemical processes during schistosity development. A low concentration of primary U occurs in micro-inclusions of apatite and zircon (many are metamict) in the granulite facies M1 assemblage. This assemblage which lacks B, except for zoned sillimanite, has undergone a localized retrograde metamorphism RM1 characterised by hydrous alteration products containing abundant U and B. The RM1 metamorphism is attributed to fluids generated during granulite facies dehydration reactions. A schistosity S2 defined by M2 fibrolite aggregates overprints the M1 events. It is associated with (1) intragranular U concentrated in M2 apatite and titanium bearing minerals and (2) abundant intergranular U within the fibrolite aggregates. High B contents also occur with the fibrolite. The S2 schistosity appears to develop in a metamorphic environment containing a fluid enriched in U and B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373680
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  • 8
    Electronic Resource
    Electronic Resource
    Recrystallization and peristerite formation in albite (1976)
    Springer
    Contributions to mineralogy and petrology 57 (1976), S. 55-69 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Plagioclase in the range An2-An10 in a relatively undeformed Quartz—feldspar pegmatite is compared with similar material in a strongly deformed and recrystallized shear zone. Optical and transmission electron microscope observations and chemical data are discussed in terms of established mechanisms of strain induced recrystallization. Recrystallization occurs by the formation of subgrains from recovery, and their subsequent growth by boundary migration or coalescence by rotation. It is suggested that the recrystallization and grain growth are enhanced by a small increase in the anorthite content. Peristerite formation in the recrystallized grains is associated with the migration of high angle boundaries under upper greenschist facies conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392852
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  • 9
    Electronic Resource
    Electronic Resource
    Combined diffusion—Infiltration of uranium in micaceous schists (1977)
    Springer
    Contributions to mineralogy and petrology 65 (1977), S. 171-181 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Fission and particle track methods have been used to study uranium and lithium/boron distributions in muscovite and biotite schists. The results show that uranium and lithium/boron have a non-uniform distribution within grain boundaries and strained crystal lattice structures of the micas. Uranium redistribution is attributed to; (1) hydrothermal or metamorphic fluids that have redistributed the uranium together with lithium/boron by diffusion and infiltration through planar and lattice defects within the mica aggregate, (2) meteoric fluids that postdate the hydrothermal or metamorphic fluid and are also responsible for the introduction of iron and manganese concentrations within planar defect structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371057
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  • 10
    Electronic Resource
    Electronic Resource
    Growth defects in metamorphic biotite (1977)
    Springer
    Physics and chemistry of minerals 2 (1977), S. 153-169 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Metamorphic biotites examined by transmission electron microscopy contain planar defects on the (001) plane, superlattices, twins and a microstructure causing streaking of k≠3n rows. Analysis of the fringe contrast shows that the fault vectors associated with the planar defects are either R 1=±1/3 [010], R 2=±1/6 [310] or R 3=±1/6 [3 $$\bar 1$$ 0]. Structural considerations indicate that a stacking fault R 1, R 2 or R 3 is most likely to exist in the octahedral layer rather than the potassium layer. The result of such a fault on a unit layer of mica is effectively to rotate it through ±120° about c* (equivalent to the common mica twin law). These stacking faults can provide the mechanism for producing the ±120° rotations associated with the common mica polytypes. Furthermore, many of the observed microstructures can be generated by these stacking faults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307529
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