Les tholeiites a affinité alcaline du secteur ouest du Siroua (Anti-Atlas central, Maroc): temoins d'une distension au Néoproterozoïque |
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| Authors: | Ahmed Touil Abdelmajid El-Boukhari Essaid Bilal Jacques Moutte |
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| Institution: | 1 Faculté des Sciences et Techniques Guéliz, Département de Géologie, Université Cadi Ayad, BP 618 Marrakech, Maroc;2 Faculté des Sciences Semlalia, Département de Géologie, Université Cadi Ayad, BP 518 Marrakech, Maroc;3 Ecole des Mines, centre SPIN, Laboratoire de Géochimie, 158 Cours Fauriel, 42023 Saint-Etienne, France |
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| Abstract: | The Upper Proterozoic granitoids of the western part of the Siroua Massif (central Anti-Atlas, Morocco) are cut by doleritic dykes injected along submeridian and equatorial directions. These dykes were emplaced before deposition of late Neoproterozoic formations (PIII). According to 
and incompatible element ratios, these dolerites constitue two discrete chemical groups unrelated to orientation and thickness. They are both enriched in large ion lithophile elements, Zr, Th and light rare earth elements, and correspond to continental tholeiites displaying an alkaline affinity. This alkaline affinity is also confirmed by clinopyroxene and amphibole chemistry. Emplacement of these doleritic dykes occurred under an extensional regime active in the Anti-Atlas range during the Upper Proterozoic. |
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