Mise en évidence de téphrites à néphé line syntectoniques dans le bassin cambrien de Sidi Saïd Maâchou (Meseta ĉtière, Maroc); signification géodynamique

Abstract

Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Saïd Maâchou (coastal Meseta) in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral submeridian shear zone which has been activated at the end of the aledonian orogenesis, by a mantellic advection.