Petrographic and Magnetic Fabric Investigation of the Tadaout-Tizi n'Rsas Dyke Swarms in the Eastern Anti-Atlas, Morocco

Abstract

Located in the eastern part of the Anti-Atlas, the Tafilalet region shows numerous dykes and sills that crosscut the Paleozoic terrains. The magmatic structures (dykes and sills) of the Tadaout-Tizi n'Rsas (TTR) anticline is studied here, it located neighboring the main branch of the Anti-Atlas Major Fault (AAMF), known in this location as the Oumejrane-Taouz Fault (OJTF). The N20° to N60°t rending dykes crosscut the Paleozoic formations (Ordovician to Devonian), whereas sills are injected into the Silurian and Devonian ones. The dyke swarms of TTR have been studied using the Anisotropy of Magnetic Susceptibility (AMS), petrographic study and structural analyses. The petrographic study of the TTR doleritic dykes shows a dominance of plagioclase feldspars, alkali feldspars, amphiboles, pyroxenes and biotite. The dykes contain also mesotype (natrolite), sphene (titanite), apatite, actinolite and pegmatitic enclaves of biotite, orthoclase feldspars and pelites. Concerning field works, they show the deformation of TTR dykes by the Variscan tectonics events, it is marked by the presence of displacements (strike-slip faults) and cleavages. The Magnetic Susceptibility (MS) measured on magmatic specimens show the dominance of ferromagnetic and paramagnetic minerals. The high values of MS in the dykes are due to the presence of hematite, amphibole, pyroxene and biotite. In addition their magnetic fabric, determined by our AMS study, allows us to reconstitute the tectonic event which affected the magmatic bodies. This one is characterized by a magnetic foliation and a NNW-trending lineation that reflect the Variscan shortening orientation.

Integrating Aster Images Processing and Fieldwork for Identification of Hydrothermal Alteration Zones at the Oumjrane-Boukerzia District, Moroccan Anti-Atlas

“…It is worth noting that, after several fieldwork missions, the iron oxides and hydroxides are closely related the mineral veins in the region, except in some tiny ferruginous levels that are interbedded in the Ordovician sedimentary series. The fact that the iron oxides and hydroxides are ultimately related the minerals veins is suggested in several districts along the Tafilalet and Maider Paleozoic basins at the extreme eastern part of the Anti-Atlas belt [11] [12].…”