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  • 1
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Interpretations based on quantitative phase diagrams in the system CaO–Na2O–K2O–TiO2–MnO–FeO–MgO–Al2O3–SiO2–H2O indicate that mineral assemblages, zonations and microstructures observed in migmatitic rocks from the Beit Bridge Complex (Messina area, Limpopo Belt) formed along a clockwise P–T path. That path displays a prograde P–T increase from 600 °C/7.0 kbar to 780 °C/9–10 kbar (pressure peak) and 820 °C/8 kbar (thermal peak), followed by a P–T decrease to 600 °C/4 kbar. The data used to construct the P–T path were derived from three samples of migmatitic gneiss from a restricted area, each of which has a distinct bulk composition: (1) a K, Al-rich garnet–biotite–cordierite–sillimanite–K-feldspar–plagioclase–quartz–graphite gneiss (2) a K-poor, Al-rich garnet–biotite–staurolite–cordierite–kyanite–sillimanite–plagioclase–quartz–rutile gneiss, and (3) a K, Al-poor, Fe-rich garnet–orthopyroxene–biotite–chlorite–plagioclase–quartz–rutile–ilmenite gneiss. Preservation of continuous prograde garnet growth zonation demonstrates that the pro- and retrograde P–T evolution of the gneisses must have been rapid, occurring during a single orogenic cycle. These petrological findings in combination with existing geochronological and structural data show that granulite facies metamorphism of the Beit Bridge metasedimentary rocks resulted from an orogenic event during the Palaeoproterozoic (c. 2.0 Ga), caused by oblique collision between the Kaapvaal and Zimbabwe Cratons. Abbreviations follow Kretz (1983).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1759-1766 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pressure-gradient–velocity correlation and return to isotropy term in the Reynolds stress transport equation are analyzed using the Yakhot–Orszag renormalization group. The perturbation series for the relevant correlations, evaluated to lowest order in the ε expansion of the Yakhot–Orszag theory, are infinite series in tensor product powers of the mean velocity gradient and its transpose. Formal lowest-order Padé approximations to the sums of these series produce a rapid pressure strain model of the form proposed by Launder et al. [J. Fluid Mech. 68, 537 (1975)], and a return to isotropy model of the form proposed by Rotta [Z. Phys. 129, 547 (1951)]. In both cases, the model constants are computed theoretically. The predicted Reynolds stress ratios in simple shear flows are evaluated and compared with experimental data. The possibility is discussed of deriving higher-order nonlinear models by approximating the sums more accurately.
    Type of Medium: Electronic Resource
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  • 3
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    Manchester : Periodicals Archive Online (PAO)
    Journal of Semitic studies. 5:3 (1960:July) 281-328 
    ISSN: 0022-4480
    Topics: Linguistics and Literary Studies , Ethnic Sciences
    Notes: REVIEWS
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  • 4
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Archaische Granodiorite des Ventersdorp Domes sind durch zwei Typen hydrothermaler Verdnderung, Epidotisierung und Kalifeldspatisierung überprägt worden. Die Veránderung tritt sowohl durchdringend als auch auf Adern auf. Massenvergleichsberechnungen ergaben, daß während der Epidotisierung CaO, Fe2O3, Sr und Y angereichert und Na2O, K2O, MgO, Pb und Ba abgeführt worden sind. Während der kombinierten Epidotisierung und Kalifeldspatisierung treten eine Zufuhr von SiO2, Fe2O3, CaO, K2O, Ba, Sr und Rb auf. A12O3 und Nb verhielten sich während beider Verdnderungen immobil. Die hydrothermale Veränderung wurde von einer Verminderung des Ca-Gehaltes der Plagioklase begleitet (An11 zu An1).
    Notes: Summary Archaean granodioritic rocks from the Ventersdorp Dome have been hydrothermally altered in two stages: epidotization and K-feldspatization. The alteration locally is both pervasive or occurs along veins. Mass balance calculations reveal CaO, Fe2O3, Sr and Y addition and loss of Na2O,K2O, MgO, Pb and Ba during epidotization. The combined epidotization and K-feldspatization involved a gain in SiO2, Fe2O3, CaO, K2O, Ba, Sr and Rb. A12O3 and Nb were immobile during both alteration stages. The alteration is accompanied by a change in the An-content of the plagioclase (An11 to An1).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mineralogy and petrology 40 (1989), S. 39-56 
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Hydrothermal veränderte granitische Gesteine kommen am nördlichen und nordwest-lichen Rand von dem vor, was man klassisch als “Witwatersrand-Becken” bezeichnet. Während dieser hydrothermalen Umwandlung wurden Pyrit, Kupferkies, Zinkblende, Molybdänglanz, Bleiglanz, Wurtzit und andere Sulfide abgesetzt, ebenso Uran- und SEE-reiche Knollen aus kohliger Substanz und Freigold. Erhitzungs- und Ausfrierdaten von sekundären Fluideinschlüssen in Gesteinsquarz, ebenso wie von primären Fluideinschlüssen in Gangquarz und Karbonat weisen darauf hin, daß zwei Hauptgruppen von wäßrigen Fluideinschlüssen existieren. Der Bereich der finalen Schmelztemperaturen der ersten Gruppe liegt zwischen 0 °C und −9 °C, was einer Salinität zwischen 0 und 13 äquiv. Gew.-% NaCl entspricht. Homogenisierung erfolgte bei Temperaturen zwischen 130 °C und 230 °C. Die zweite Gruppe von Einschlüssen hat im allgemeinen finale Schmelztemperaturen zwischen −14 °C und −26 °C, mit Salinitäten, die sich zwischen 12 und 30 äquiv. Gew.-% NaCl bewegen. Die Homogenisierungstemperaturen variieren von 120 °C bis ungefähr 170 °C. Die niedrigen initialen Schmelztemperaturen von −60 °C bis −35 °C und SEM-EDX-Analysen von Inkrustationen, die sich nach der Verdunstung der Flüssigkeit in geöffneten Einschlüssen bilden, weisen auf Ca, Cl und S als weitere Bestandteile. Gelegentliches Clathratschmelzen in beiden Typen von Fluiden zeigt die Anwesenheit von CO2, CH, und einigen anderen Clathratbildnern. Die niedrigsalinaren Fluide werden als von meteorischem, Seewasser oder metamorphem Ursprung gedeutet, während die hochsalinaren Fluide als “con.nate brines” oder sehr gereifte Formationswässer angesehen werden.
    Notes: Summary Hydrothermally altered granitic rocks occur along the northern and northwestern edge of what is classically termed the “Witwatersrand Basin”. Pyrite, chalcopyrite, sphalerite, molybdenite, galena, wurtzite and other sulphides were deposited during this hydrothermal alteration, as were uranium and REE-rich nodules of carbonaceous matter and free gold. Heating and freezing data from secondary fluid inclusions in igneous quartz as well as primary fluid inclusions in vein quartz and carbonate indicate that two main groups of aqueous fluid inclusions exist. The first group has a range of final melting temperatures from 0 °C to −9 °C, corresponding to salinities between 0 and 13 equivalent wt.% NaCl. Homogenization occurred at temperatures between 130 °C and 230 °C. The second group of inclusions generally have final melting temperatures between −14 °C and −26 °C, with salinities ranging between 12 and 30 equivalent wt.% NaCl. Homogenization temperatures range from 120 °C to about 170 °C. The low initial melting temperatures of -60°C to −35°C and SEM-EDX analyses of encrustations formed after evaporation of fluid in opened inclusions indicate as additional components Ca, Cl and S. Rare clathrate melting in both types of fluids indicate the presence of CO2, CH4 or some other clathrate compound. The low salinity fluids are interpreted to be of a meteoric, seawater or metamorphic origin, whereas the highly saline fluids are thought to be connate brines or highly evolved formation waters.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 287 (1980), S. 33-35 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The layering and mineralogical variation in the Bushveld Complex, shown in Fig. 1, is accepted to be the result of fractional crystallization from a basic magma. However, the exact composition of this magma has been debated. Willemse1 believed it to be similar to the voluminous metamorphosed ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 283 (1980), S. 756-758 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The BMS has been intruded by the 3,320 Myr old Tsawela gneiss6,7, the 3,030 Myr old Lochiel (Homogeneous Hood) granite (refs 15, 22 and J.M.B., unpublished data) and mafic dykes. Faulting and mylonisation in some areas have intensely deformed the BMS gneisses and fresh exposures of the BMS commonly ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 487-490 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Rb/Sr whole-rock ages from two suites of tholeiitic dykes establish a pre-3,600 Myr history for some granodioritic gneisses in the Limpopo Mobile Belt and identify two previously unrecognised magmatic events in the evolution of this region. This has important implications with regard to ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 97 (1987), S. 488-496 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Annandagstoppane Granite is exposed at three nunataks in Western Dronning Maud Land, Antarctica. It comprises medium- to coarse-grained granite crosscut by veins of pegmatite and graphic granite and has many S-type characteristics such as containing normative corundum greater than 1.1%, molecular Al2O3/(CaO+K2O+Na2O) greater than 1.1 and very little zircon. Hydrothermal alteration in the Granite is variably developed and has affected only certain minerals in any phase. R-Sr and Pb whole rock and mineral isotopic data suggest: 1) that Sr isotopes within it were nearly homogenized on a whole rock scale about 2823 Ma ago by this hydrothermal alteration; 2) that the Pb isotopic system was also disturbed at that time, and 3) that the Granite may have been was emplaced sometime during the interval 3115 Ma to 2945 Ma ago. The Granite was probably intruded by the Annandagstoppane Gabbro about 1200 Ma ago, resetting the Rb-Sr system in biotite. The Annandagstoppane Granite may form part of a basement complex to the Proterozoic sedimentary, volcanic and mafic igneous rocks exposed to the east in the Ahlmannryggen and the Borgmassivet. Its chemical composition and geologic history appears to be unique in Antarctica and in the Kaapvaal Craton of Southern Africa, consistent with the possibility that the Annandagstoppane Granite is part of a crustal fragment that joined Antarctica relatively late in the history of that continent.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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