Abstract

The concentrically zoned Zaër pluton (Variscan Meseta of Morocco), previously modeled as the nesting of two magmas forming a ballooning pluton, is here subjected to a study of its internal magmatic and solid-state structures. The magmatic flow patterns, derived mainly from anisotropy of magnetic susceptibility measurements, together with structural observations down to thin-section scale, indicate that these two magmas have undergone totally independent kinematics of emplacement. This supports recent isotope geochemistry and geochronology data indicating independent origin of the magmas and diachronism of emplacement, respectively. Thus, we propose that a magma diapir, probably emplaced within a crustal fracture zone, cooled down to brittle conditions, before a likely flat-lying fracture was opened within the fracture zone and was filled with a new and compositionally different pulse of magma.

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