Tectonometamorphic evolution of an intracontinental orogeny inferred fromP-T-t-dpaths of the metapelites from the Rehamna massif (Morocco)
Autor: | Pavla Štípská, M. El Houicha, Delphine Bosch, Francis Chopin, Pauline Wernert, Karel Schulmann |
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Přispěvatelé: | Czech Geological Survey [Praha], Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Université Chouaib Doukkali (UCD) |
Rok vydání: | 2016 |
Předmět: |
010504 meteorology & atmospheric sciences
Greenschist Metamorphic rock Geochemistry Metamorphism engineering.material 010502 geochemistry & geophysics 01 natural sciences intracontinental orogeny [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry Geochemistry and Petrology Carboniferous metapelite pseudosection monazite dating 0105 earth and related environmental sciences geography geography.geographical_feature_category Variscan Morocco Geology Orogeny Massif P-T-t-d paths Andalusite visual_art Staurolite engineering visual_art.visual_art_medium |
Zdroj: | Journal of Metamorphic Geology Journal of Metamorphic Geology, Wiley-Blackwell, 2016, 34 (9), pp.917-940. ⟨10.1111/jmg.12214⟩ |
ISSN: | 0263-4929 1525-1314 |
Popis: | New petrographic and microstructural observations, mineral equilibria modelling and U/Pb (monazite) geochronological studies were carried out to investigate relationship between deformation and metamorphism across the Rehamna massif (Moroccan Variscan belt). In this area, typical Barrovian (muscovite to staurolite) zones developed in Cambrian to Carboniferous metasedimentary rocks that are distributed around a dome-like structure. First assemblages are characterized by the presence of locally preserved andalusite, followed by prograde evolution culminating at 6 kbar and 620 °C in the structurally deepest staurolite zone rocks. This Barrovian sequence was subsequently uplifted to supracrustal levels, heterogeneously reworked at greenschist facies conditions, which was followed locally by static growth of andalusite, indicating heating to 2.5−4 kbar and 530−570 °C. The 206Pb/238U monazite age of 298.3 ± 4.1 Ma is interpreted as minimum age of peak metamorphic conditions whereas the ages of 275.8 ± 1.7 Ma and 277.0 ± 1.1 Ma date decompression and heating at low pressure, in agreement with previous dating of Permian granitoids intruding the Rehamna massif. The prograde metamorphism occurred during thickening and associated horizontal flow in the deeper crust (S1 horizontal schistosity). The horizontally disposed metamorphic zones were subsequently uplifted by a regional scale antiform during ongoing N-S compression. The re-heating of the massif follows late massive E-W shortening, refolding and retrograde shearing of all previous fabrics coevally with regionally important intrusions of Permian granitoids. We argue that metamorphic evolution of the Rehamna massif occurred several hundred kilometres from the convergent plate boundaries in the interior of continental Gondwanan plate. The tectonometamorphic history of the Rehamna massif is put into Palaeozoic plate tectonic perspective and Late Carboniferous reactivation of (Devonian)-Early Carboniferous basins formed during stretching of the north Gondwana margin and formation of the Palaeotethys Ocean. The inherited heat budget of these magma-rich basins plays a role in the preferential location of this intracontinental orogen. It is shown that rapid transition from lithospheric stretching to compression is characterized by specific HT type of Barrovian metamorphism, which markedly differs from similar Barrovian sequences along Palaeozoic plate boundaries reported from Variscan Europe. This article is protected by copyright. All rights reserved. |
Databáze: | OpenAIRE |
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