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  • 1
    Electronic Resource
    Electronic Resource
    Hydrothermal alteration, fluid flow and volume change in shear zones: the layered mafic–ultramafic Kettara intrusion (Jebilet Massif, Variscan belt, Morocco) (2004)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 22 (2004), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: During emplacement and cooling, the layered mafic–ultramafic Kettara intrusion (Jebilet, Morocco) underwent coeval effects of deformation and pervasive fluid infiltration at the scale of the intrusion. In the zones not affected by deformation, primary minerals (olivine, plagioclase, clinopyroxene) were partially or totally altered into Ca-amphibole, Mg-chlorite and CaAl-silicates. In the zones of active deformation (centimetre-scale shear zones), focused fluid flow transformed the metacumulates (peridotites and leucogabbros) into ultramylonites where insoluble primary minerals (ilmenite, spinel and apatite) persist in a Ca-amphibole-rich matrix. Mass-balance calculations indicate that shearing was accompanied by up to 200% volume gain; the ultramylonites being enriched in Si, Ca, Mg, and Fe, and depleted in Na and K. The gains in Ca and Mg and losses in Na and K are consistent with fluid flow in the direction of increasing temperature.When the intrusion had cooled to temperatures prevailing in the country rock (lower greenschist facies), deformation was still active along the shear zones. Intense intragranular fracturing in the shear zone walls and subsequent fluid infiltration allowed shear zones to thicken to metre-scale shear zones with time. The inner parts of the shear zones were transformed into chlorite-rich ultramylonites. In the shear zone walls, muscovite crystallized at the expense of Ca–Al silicates, while calcite and quartz were deposited in ‘en echelon’ veins. Mass-balance calculations indicate that formation of the chlorite-rich shear zones was accompanied by up to 60% volume loss near the centre of the shear zones; the ultramylonites being enriched in Fe and depleted in Si, Ca, Mg, Na and K while the shear zones walls are enriched in K and depleted in Ca and Si. The alteration observed in, and adjacent to the chlorite shear zones is consistent with an upward migrating regional fluid which flows laterally into the shear zone walls. Isotopic (Sr, O) signatures inferred for the fluid indicate it was deeply equilibrated with host lithologies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2004.00495.x
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  • 2
    Electronic Resource
    Electronic Resource
    Major and trace element geochemistry and isotope (Sr, Nd, Pb, O) systematics of an Archaean basement involved in a 2.0 Ga very high-temperature (1000°C) metamorphic event: In Ouzzal Massif, Hoggar, Algeria (1996)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 14 (1996), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The In Ouzzal granulitic massif is composed mainly of various meta-igneous rocks which, in spite of Rb, U, Th, Cs and some K and Sr mobility, can be dated and generally classified according to their chemical composition as follows.Basic and ultrabasic granulites interlayered with the metasediments correspond to (1) ultrabasic cumulates from dislocated tholeiitic bodies, (2) ancient komatiitic to high-Mg tholeiitic basalts similar to the suites found in Archaean greenstone belts and (3) calcalkaline protoliths of high-K andesitic composition. No geochronological constraints are available apart from the depositional age of some associated sediments which is younger than 2.70 Ga detrital zircons, and the Nd model age of the andesitic granulites of c. 3.4 Ga.In spite of the high-grade metamorphism, the acidic magmatic precursors of the charnockites can be divided in three groups. (1) The most juvenile acid orthogneisses are trondhjemitic or tonalitic in composition, being similar to the TTG suites which are classically considered to be formed by partial melting of mantle-derived protoliths. The 3.3–3.2 Ga TDM indicates a possible age of separation from the mantle reservoir while the plutons may have been emplaced between 3.3 and 2.7 Ga (U–Pb zircon & Nd ages). (2) A group of alkaline granitic gneisses, similar in composition to rift-related-granites, were emplaced at 2650±10 Ma (U–Pb & Rb–Sr ages) in a thick continental crust. (3) Calcalkaline granodioritic and monzogranitic suites derived from the partial melting of continental precursors (3.5–3.3 Ga), in lower to middle levels of the continental crust. They were emplaced close to 2.5 Ga during crustal thickening.The very high-temperature metamorphism occurred at 2002±7 Ma from the age of synfoliation intrusions and was probably related to major overthrusting. Retrogressive metamorphism is dated at 1.95 Ga from garnet-Nd ages. In spite of the very high-temperature conditions, partial melting during granulite facies metamorphism may be restricted to scarce cordierite-bearing monzogranitic gneisses. The 2.0 Ga VHT metamorphism could be related to overthrusting, extensional or underplating processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1996.00054.x
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  • 3
    Electronic Resource
    Electronic Resource
    The Pyrenees: Subduction and collision?
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 35 (1977), S. 151-160 
    Details
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0012-821X(77)90038-3
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  • 4
    Electronic Resource
    Electronic Resource
    Relationships between granite-gneiss terrains, greenstone belts and granulite belts in the archean crust of Lapland (Fennoscandia) (1980)
    Springer
    International journal of earth sciences 69 (1980), S. 648-658 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The Archean crust of Lapland (Fennoscandia) consists of four units (from north to south): (1) the Inarijärvi nucleus, old basement complex of gneisses and greenstones, (2) the granulite belt, thick terrigenous metasedimentary sequence intruded by small amounts of calc-alkaline plutonic rocks, (3) the Tana River belt composed of tholeiitic metavolcanics, and (4) a set of gneiss domes fringed with younger greenstone belts. The main feature of their metamorphic and tectonic evolution are described. Geodynamic models applied to the Archean are discussed and a crustal evolutionary model suitable for this region is proposed. We assume that the Tana River and granulite belts represent a suture between an older domain in the north (craton of Kola Peninsula) and the northern part of the Archean basement of Central Finland.
    Abstract: Résumé La croûte archéenne de Laponie (Fennoscandie) comprend quatre unités principales. Ce sont du Nord au Sud: (1) le nucleus de l'Inarijärvi, formé par un vieux socle complexe avec des gneiss et des roches vertes, (2) la ceinture granulitique, à l'origine formée par une épaisse séquence sédimentaire térrigène et par des intrusions calcoalcalines, (3) la ceinture de la Tana River composée de métavolcanites tholéitiques et, (4) un ensemble de dÔmes de gneiss flanqués de jeunes ceintures de roches vertes. Les grands traits de l'évolution tectonométamorphique de cet ensemble sont décrits. Les modèles géodynamiques archéens classiques sont discutés et un modèle d'évolution crustale pour cette région est proposé. Nous pensons que la ceinture de la Tana River et celle des granulites représentent une suture entre un domaine ancien au Nord (craton de la Péninsule de Kola) et la partie septentrionale du socle archéen de Finlande centrale.
    Notes: Zusammenfassung Die archaische Kruste von Lapland (Fennoscandia) besteht von Nord nach Süd aus vier Einheiten: (1) der Inarijärvi-Kern, ein alter Grundgebirgskomplex mit Gneisen und Grünschiefem; (2) der Granulit-Gürtel mit mächtigen terrigenen Metasedimenten, in die kleine Kalkalkaliplutone intrudierten; (3) der Tana-Gürtel, der aus tholeiitischen Metavulkaniten besteht; (4) eine Gruppe von Gneisdomen, die von jüngeren Grünschieferzonen umgeben werden. Wir nehmen an, daß der Tana-Gürtel und der Granulit-Gürtel eine Sutur zwischen einem älteren Kern im Norden (Kola-Kraton) und dem nördlichen Teil des archaischen Grundgebirges von Zentralfinnland bildet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02104639
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  • 5
    Electronic Resource
    Electronic Resource
    Archaeobotanical remains of hulled and naked cereals in the Iberian Peninsula (1997)
    Springer
    Vegetation history and archaeobotany 6 (1997), S. 15-23 
    Details
    ISSN: 1617-6278
    Keywords: Hulled and naked cereal ; Prehistoric agriculture ; Iberian Peninsula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract Archaeobotanical finds in Spain show differences in the representation of the different wheats and barleys. From the beginning of agriculture (around 5000 B.C.) onwards, all wheats and barleys can be found at the sites of the eastern Peninsula. But in later periods of the early Neolithic, free-threshing wheat becomes more important in the northeast and the southeast, compared to the hulled wheats (emmer and einkorn). Nevertheless, both naked and hulled barleys can be found in similar frequencies in this period. Seed analyses in the southeast and the east of Spain show the importance of naked barley compared with hulled barley in the third millenium uncal B.C. This is not the case in the northeast, where hulled barley has a similar frequency in this period until the Iron Age, when both hulled barley and free-threshing wheat are the most important taxa. The substitution of naked barley for hulled barley in the south-east Iberian Peninsula is very significant in the period of greatest growth of the Argar culture. Free-threshing wheat can be found at a similar frequency throughout the study area, and was an important human food source together with the barleys. Hulled wheats seem to have played a secondary role as food in all periods, although they are constantly present in our samples. Nevertheless spelt wheat does not appear until the Roman period, when it is only found on the Cantabrian north coast, where it is important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01145882
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