Journal ArticleDOI
Mineral-chemical and isotopic studies of Namaqualand granulites, South Africa: A grenville analogue
TLDR
In this paper, the results of electron microprobe studies of minerals from two-pyroxene, cordierite-orthopyroxene (-gedrite) (-sapphirine) and garnet and/or Cordierite parageneses from Namaqualand, in the N.W. Cape Province of South Africa were reported.Abstract:
The northwestern part of South Africa and southern South-West Africa/Namibia is amongst the most extensive granulite terranes in Africa. This work reports the results of electron microprobe studies of minerals from two-pyroxene, cordieriteorthopyroxene (-gedrite) (-sapphirine) and garnet and/or cordierite parageneses from Namaqualand, in the N.W. Cape Province of South Africa. Determined PT conditions of prograde metamorphism based on thermodynamic calculations are 800°–900° C and ca. 6–7 Kb; and it is argued that rocks of unusual composition, notably cordierite-orthopyroxene rocks, are restites after the extraction of granitic liquid from former argillites. This interpretation is consistent with previously published data on similar rocks, and with McCarthy's (1976) suggestion of extensive partial melting in the quartzofeldspathic rocks in the area.read more
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The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens
TL;DR: The role of deformation in enhancing segregation of melt is discussed in this article, where the authors emphasize the role of ductile shear zones and fault systems in the ascent and emplacement of granite magma.
Journal ArticleDOI
On ultrahigh temperature crustal metamorphism: phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings
David E. Kelsey,Martin Hand +1 more
TL;DR: In this article, a ferric iron activity-composition thermodynamic model for sapphirine was developed, allowing phase diagram calculations for oxidised rock compositions and quantification of UHT conditions via trace element thermometry, with Zr-inrutile more commonly recording higher temperatures than Ti-inzircon.
Journal ArticleDOI
Melt segregation in migmatites
TL;DR: In this article, the authors evaluate the compaction model for segregation as it applies to migmatites and develop models for melt segregation based upon convection driven by volume change and upon advection down pressure gradients that result from applied differential stress acting on an anisotropic multilayer protolith.
Journal ArticleDOI
Etendeka Volcanism of the Goboboseb Mountains and Messum Igneous Complex, Namibia. Part I: Geochemical Evidence of Early Cretaceous Tristan Plume Melts and the Role of Crustal Contamination in the Paraná–Etendeka CFB
TL;DR: Ewart et al. as discussed by the authors inferred that the mafic lavas are derived from the Goboboseb-Messum Centre and the Messum Carter Basalts (MCB) and showed evidence for crystal fractionation, have 'arc-like' trace element signatures, correlated e-SiO, e-Ti/γ and -Ti/Zr.
Journal ArticleDOI
The History of Granulite-Facies Metamorphism and Crustal Growth from Single Zircon U-Pb Geochronology: Namaqualand, South Africa
TL;DR: The Namaqualand metamorphic complex is a well-exposed, INTRODUCTION Mesoproterozoic, low-pressure, amphibolite-granulite-facies terrane flanking the Archaean Kaapvaal Craton of southern Africa as discussed by the authors.
References
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Journal ArticleDOI
Approximation of terrestrial lead isotope evolution by a two-stage model
J.S. Stacey,Jan Kramers +1 more
TL;DR: In this paper, a two-stage model for terrestrial lead isotope evolution is proposed, which permits the age of the earth to be that of the meteorite system and also yields good model ages for samples of all ages.
ReportDOI
Thermodynamic Properties of Minerals and Related Substances at 298.15 K and 1 Bar (105 Pascals) Pressure and at Higher Temperatures
TL;DR: A report about values for the entropy, molar volume, and for the enthalpy and Gibbs energy of formation for the elements and minerals and substances at 298.15 K was given in this paper.
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A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations
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Nomenclature of amphiboles
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