Electrical Anisotropy Evidence in the in Ouzzal Granulitic Unit, Western Hoggar (Southern Algeria)

The In Ouzzal Granulitic Unit (IOGU) is an Archean/Paleoproterozoic terrane located in the Northwestern part of the Tuareg Shield, in southern Algeria. The IOGU lithosphere was first remobilized during the Paleoproterozoic and then by the Pan-African orogenies. Magnetotelluric (MT) survey consisting of 12 sites was carried out in the In Ouzzal terrane along the East–West profile with approximately a hundred kilometers long. The main objective of this study is to evaluate the electrical anisotropy of the In Ouzzal underlying lithosphere. For dimensionality and directionality analysis, we used the phase tensor method and the real induction arrows. The outcomes show that data for periods up to 1 s are more consistent with 3D with a strike angle of N20°E. The direction of the real induction arrows according to the Parkinson convention is in agreement with the regional geological strike of the IOGU. It is well known that electrical anisotropy can have a significant influence on the MT responses and may create artifacts in isotropic inversions. The combination between the phase split and the induction arrows’ patterns reveals two electrical anisotropy zones at the lithospheric mantle level, where each of them is located in the western and the eastern parts of the profile.