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  • 1
    Electronic Resource
    Electronic Resource
    Litholog and structure of the Grenville-aged (≈1.1 Ga) basement of heimefrontfjella (East Antarctica) (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 800-821 
    Details
    ISSN: 1437-3262
    Keywords: East Antarctica ; Greenville ; Pan-African ; Rodinia ; Heimefrontfjella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Heimefrontfjella mountains, Western Dronning Maud Land (East Antarctica), are dominantly composed of Grenville-aged (≈ 1.1 Ga) rocks, which were reworked during the Pan -African orogeny at ≈500 Ma. Three discontinuity-bounded Grenville-aged terranes have been recognized namely (from north to south) the Kottas, Sivorg and Vardeklettane terranes. The terranes contain their own characteristic lithological assemblages, although each is made up of an early supracrustal sequence of metavolcanic and/or metasedimentary gneisses, intruded by various (predominantly granitoid) suites. No older basement upon which the protoliths of these older gneisses were deposited has been recognized. In each terrane the older layered gneisses were intruded by various plutonic suites ranging in age from ≈ 1150 to ≈1000 Ma. The Vardeklettane terrane is characterized by abundant charnockites and two-pyroxene granulite facies parageneses in metabasites, whereas the Sivorg and Kottas terranes were metamorphosed to amphibolite facies grade. P-T estimates show that peak metamorphic conditions changed from ≈600°C at 8 kbar in the south, to ≈700 °C at 4 kbar in the northern Sivorg terrane. Regional greenschist retrogression of high-grade assemblages may be of Pan-African age. The Heimefrontfjella terranes were juxtaposed and pervasively deformed during a complex and protracted period of E-W collision orogenesis in a transpressive regime at ≈ 1.1 Ga. This is manifest as early, gently dipping thrust-related shear fabrics (D1), succeeded by the initiation of an important (D2) steep dextral shear zone (Heimefront shear zone, HSZ), during which the early fabrics and structures were steepened and rotated in an anticlockwise sense. The HSZ is a curvilinear structure which changes from a dextral oblique strike-slip lateral ramp in the north to a steep dip-slip frontal ramp in the south, where it forms the boundary between the Sivorg and Vardeklettane terranes. The Pan-African event is manifested as discrete, low- to medium-temperature ductile to brittle shears (D3) and numerous K/Ar cooling ages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02440112
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  • 2
    Electronic Resource
    Electronic Resource
    Cadomian terranes, wrench faulting and thrusting in the central Europe Variscides: geophysical and geological evidence (1995)
    Springer
    International journal of earth sciences 84 (1995), S. 412-432 
    Details
    ISSN: 1437-3262
    Keywords: Cadomian terranes ; Wrench faults ; European Variscides ; DEKORP ; gravity-magnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sixty five per cent of the Paleozoic basement of western and central Europe is hidden by a sedimentary cover and/or sea. This work aims to remove that blanket to detect new structures which could used to build a more comprehensive model of the Variscan orogeny. It is based on the interpretation of various forms of data: (a) published gravity maps corrected for the effects of the crust-mantle boundary topography and light sedimentary basins; (b) aeromagnetic maps; (c) measurements of densities; and (d) induced and remanent magnetizations on rocks from Paleozoic outcrops of the upper Rhenish area. From the northern Bohemian Massif to the eastern Paris Basin, the Saxothuringian is characterized by a 500 km long belt of gravity highs, the most important being the Kraichgau high. Most of the corresponding heavy bodies are buried under a post-early Viséan cover. They are interpreted as relics of Late Proterozoic terranes overlain by an Early to Middle Paleozoic sequence, equivalent to the Bohemian terrane in the Bohemian Massif. The most probable continuation of these dense Bohemian terranes toward the west is the Southern Channel-Northern Brittany Cadomian terrane. The gravity lows are correlated with Variscan granites and pre- and early Variscan metagranites. Gravity and magnetic maps demonstrate large-scale displacement in Devonian-Early Carboniferous times along the parallel and equidistant, NW-SE striking, Vistula, Elbe, Bavarian, Bray and South Armorican dextral wrench faults. In the Vosges-Schwarzwald and Central Massif the faults continue with the east-west striking Lalaye-Lubine-Baden-Baden and Marche faults and with south vergent thrusts. The Bavarian faults shift the Kraichgau terrane by 150 km relative to the Bohemian terrane, whereas the offset of the Northern Brittany Cadomian relative to the Northern Vosges-Kraichgau terranes is estimated at 400 km along the Bray fault. Sinistral wrench faults are the NE-SW striking Sillon Houiller, Rheingraben, Rodl, Vitis and Diendorf faults. The southern Vosges-Schwarzwald Devonian-Dinantian basin is interpreted as a pull-apart basin at the south-easterly extremity of the Bray fault. The Bohemian and Kraichgau body form allochthonous terranes which were thrust over the Saxothuringian crust. Thrusting to the north-west was accompanied by back-thrusting and led to the formation of pop-up structures. Contemporaneous dextral and sinistral wrench faulting resulted in transpressive strain during collision. The zonal structure of the Variscides in the sense of Kossmat (1927) is relevant only to the Rhenohercynian Foreland Belt. Kossmat (1927) already spoke of a Moldanubian Region because it displays no real zonal structure. The Saxothuringian Zone was formed by terrane accretion. Their apparent zonal structure is not a pre-collisional feature, but only the result of accretion and collision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260450
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  • 3
    Electronic Resource
    Electronic Resource
    Cadomian terranes, wrench faulting and thrusting in the central Europe Variscides: geophysical and geological evidence (1995)
    Springer
    Geologische Rundschau 84 (1995), S. 412-432 
    Details
    ISSN: 0016-7835
    Keywords: Key words Cadomian terranes ; Wrench faults ; European Variscides ; DEKORP ; gravity-magnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Sixty five per cent of the Paleozoic basement of western and central Europe is hidden by a sedimentary cover and/or sea. This work aims to remove that blanket to detect new structures which could used to build a more comprehensive model of the Variscan orogeny. It is based on the interpretation of various forms of data: (a) published gravity maps corrected for the effects of the crust–mantle boundary topography and light sedimentary basins; (b) aeromagnetic maps; (c) measurements of densities; and (d) induced and remanent magnetizations on rocks from Paleozoic outcrops of the upper Rhenish area. From the northern Bohemian Massif to the eastern Paris Basin, the Saxothuringian is characterized by a 500 km long belt of gravity highs, the most important being the Kraichgau high. Most of the corresponding heavy bodies are buried under a post-early Viséan cover. They are interpreted as relics of Late Proterozoic terranes overlain by an Early to Middle Paleozoic sequence, equivalent to the Bohemian terrane in the Bohemian Massif. The most probable continuation of these dense Bohemian terranes toward the west is the Southern Channel–Northern Brittany Cadomian terrane. The gravity lows are correlated with Variscan granites and pre- and early Variscan metagranites. Gravity and magnetic maps demonstrate large-scale displacement in Devonian–Early Carboniferous times along the parallel and equidistant, NW–SE striking, Vistula, Elbe, Bavarian, Bray and South Armorican dextral wrench faults. In the Vosges–Schwarzwald and Central Massif the faults continue with the east–west striking Lalaye-Lubine–Baden-Baden and Marche faults and with south vergent thrusts. The Bavarian faults shift the Kraichgau terrane by 150 km relative to the Bohemian terrane, whereas the offset of the Northern Brittany Cadomian relative to the Northern Vosges–Kraichgau terranes is estimated at 400 km along the Bray fault. Sinistral wrench faults are the NE–SW striking Sillon Houiller, Rheingraben, Rodl, Vitis and Diendorf faults. The southern Vosges–Schwarzwald Devonian–Dinantian basin is interpreted as a pull-apart basin at the south-easterly extremity of the Bray fault. The Bohemian and Kraichgau body form allochthonous terranes which were thrust over the Saxothuringian crust. Thrusting to the north-west was accompanied by back-thrusting and led to the formation of pop-up structures. Contemporaneous dextral and sinistral wrench faulting resulted in transpressive strain during collision. The zonal structure of the Variscides in the sense of Kossmat (1927) is relevant only to the Rhenohercynian Foreland Belt. Kossmat (1927) already spoke of a Moldanubian Region because it displays no real zonal structure. The Saxothuringian Zone was formed by terrane accretion. Their apparent zonal structure is not a pre-collisional feature, but only the result of accretion and collision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260450
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  • 4
    Electronic Resource
    Electronic Resource
    Lithology and structure of the Grenville-aged (∼1.1 Ga) basement of Heimefrontfjella (East Antarctica) (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 800-821 
    Details
    ISSN: 0016-7835
    Keywords: Key words East Antarctica ; Greenville ; Pan-African ; Rodinia ; Heimefrontfjella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Heimefrontfjella mountains, Western Dronning Maud Land (East Antarctica), are dominantly composed of Grenville-aged (∼1.1 Ga) rocks, which were reworked during the Pan -African orogeny at ∼500 Ma. Three discontinuity-bounded Grenville-aged terranes have been recognized namely (from north to south) the Kottas, Sivorg and Vardeklettane terranes. The terranes contain their own characteristic lithological assemblages, although each is made up of an early supracrustal sequence of metavolcanic and/or metasedimentary gneisses, intruded by various (predominantly granitoid) suites. No older basement upon which the protoliths of these older gneisses were deposited has been recognized. In each terrane the older layered gneisses were intruded by various plutonic suites ranging in age from ∼1150 to ∼1000 Ma. The Vardeklettane terrane is characterized by abundant charnockites and two-pyroxene granulite facies parageneses in metabasites, whereas the Sivorg and Kottas terranes were metamorphosed to amphibolite facies grade. P–T estimates show that peak metamorphic conditions changed from ∼600  °C at 8 kbar in the south, to ∼700  °C at 4 kbar in the northern Sivorg terrane. Regional greenschist retrogression of high-grade assemblages may be of Pan-African age. The Heimefrontfjella terranes were juxtaposed and pervasively deformed during a complex and protracted period of E–W collision orogenesis in a transpressive regime at ∼1.1 Ga. This is manifest as early, gently dipping thrust-related shear fabrics (D1), succeeded by the initiation of an important (D2) steep dextral shear zone (Heimefront shear zone, HSZ), during which the early fabrics and structures were steepened and rotated in an anticlockwise sense. The HSZ is a curvilinear structure which changes from a dextral oblique strike-slip lateral ramp in the north to a steep dip-slip frontal ramp in the south, where it forms the boundary between the Sivorg and Vardeklettane terranes. The Pan-African event is manifested as discrete, low- to medium-temperature ductile to brittle shears (D3) and numerous K/Ar cooling ages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050113
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