The Paleoproterozoic Djebel Drissa ring complex (Eglab shield, Algeria): Post-collisional intrusions in a transtentional tectonic setting

Abstract The Eburnean A-type granitic Djebel Drissa ring complex is part of the 2.08 Ga post-collisional Aftout magmatic suites that intruded the 2.22–2.09 Ga-old Paleoproterozoic granitoids in the Eglab shield, in West African Craton. It is composed of unfoliated granitoids arranged in near-concentric zones. The zoning is interpreted as resulting from multiple intrusions of continuous magmatic pulses, leading to in situ growth of the complex. New field observations, anisotropy of magnetic susceptibility (AMS), gravimetry and aeromagnetic data suggest that the regional deformation controlled the emplacement of this complex. The sub-circular form of the granitic body and the AMS pattern are consistent with a transtensional tectonic setting along a NW–SE major shear-zone and with an emplacement also related to an associated WNW–ESE extension fault. This well-dated regional deformation corresponds to the last main structural event of the Paleoproterozoic evolution of the Eglab shield.