New insight of the geological structures and tectonic framework of Ahnet and northwestern part of Tin Zaouatine terranes (western Hoggar, Algeria) constraints from aeromagnetic, gamma ray, and remote sensing data

Abstract

The Ahnet and Tin Zaouatine terranes are located in the southern sector of the Algerian Desert and are part of the Tuareg Shield, which was built up during east-west shortening (Pan-African orogeny). This paper presents a new 1/200,000 geological and tectonic map of the Tin Tanet Firt sheet map (mainly of the Ahnet terrane and the northwestern part of the Tin Zaouatine terrane). Enhancement and processing of multispectral satellite data (Landsat 7 ETM+) combined with field campaign and airborne geophysics was used to discriminate geological lithologies and tectonic structures. We define six geological domains: (i) Palaeozoic formation and Cambrian continental facies and plutonic rocks, (ii) Late- to post-orogenic plutonic rocks, (iii) synchronous orogenic plutonic rocks, (iv) Neoproterozoic formation, (v) Mesoproterozoic volcanics, metasedimentary rocks, and associated plutonic rocks, and (vi) Late Paleoproterozoic metasedimentary rocks. Airborne magnetic data and textural features derived from remote sensing and fieldwork allow us to identify faults and shear zones that affect the whole studied terrane. Interpreted tectonic lines and foliation paths leads us to suggest a deformation model which involves two deformation pahses: an older N-S to NNE-SSW shortening D1 and a younger D2 defined by the N-S trend and a compressional character revealed in the Ahnet terrane and Camp Zohra Complex domain which is considered a continuum deformation split into three phases that affect and form structures of the whole Ahnet and the northwestern part of Tin Zaouatine terranes at the Pan-African orogeny. The most recent stress field recorded in this region is expressed as NE-SW strike-slip faults.