Paper Number: 1396
Magnetotelluric study of the Neoproterozoic 4°50’ Hoggar shear zone
Aboubakr Deramchi 1, 2, Abderrezak Bouzid1, Abderrahmane Bendaoud2, Abdeslam Abtout1, Mohamed Hamoudi2, Khadidja Ouzegane2, Abdelhamid Bendekken3, Zakaria Boukhalfa1, 2 and Walid Boukhlouf3.
1 Centre de recherche d’astronomie d’astrophysique et de géophysique, CRAAG. Alger, Algérie. aboubakarderamchi@gmail.com ab.deramchi@craag.dz
2 Faculté des Sciences de la Terre, de la Géographie et de l’Aménagement du Territoire, USTHB, Alger, Algérie.
3 Unité de recherche de Tamanrasset, CRAAG, Tamanrasset, Algérie.
The orogenic belt of the Hoggar is a product of the assembly of Gondwana. The greatest 4°50’ Hoggar Shear zone is also known in Nigeria as Kandi fault and in Brazil as Transbrasiliano lineament (TBL). The Neoproterozoic 4°50’ fault played an important role in the structuration of Hoggar during the Panafrican orogeny. It’s considered as a major suture zone between two domains (Caby 2003, Liégeois et al., 2003): LATEA and ISKEL forming part respectively of the Central Hoggar and the Western Hoggar. According to Liégeois et al., 2005, LATEA is a metacraton constituted of five terranes (Laouni, Azrou N’fad, Tefedest, Egéré-Aleksod and Assodé Issalane) with an Archean-Paleoproterozoic basement (Betrand et al., 1986; Peucat et al., 2003) and affected by a high grade rocks (Amphibolitic to granulitic facies) (Bendaoud et al., 2008), and the Iskel terrane corresponding to a Panafrican arc material, showing a low metamorphism grade (greenschist to amphibolite) (Caby 2003).
To image the 4°50’ shear zone resistivity deep structure, the magnetotelluric (MT) method has been used. Thus, new MT data were collected in November 2015 at 15 stations along a NW-SE profile of 100 km with a step of ~7 km crossing the 4°50’ shear zone and the other linked faults. The collected MT signals cover a wide frequency band from 104 to 10-3 Hz. The collected data imaged the variation of electrical resistivity down to a depth of about 100 km and resolve three distinct highly conductive structures that most probably represent the mainly shear zones in the area including the 4°50’ fault. Analysis and first conductivity 2D modeling will be presented and discussed in this work.
Key words : Neoproterozoic, 4°50’, Magnetotelluric, shear zones, LATEA, ISKEL, suture.
References:
[1] Bendaoud A et al. (2008) in: Geological Society, 297, 111–146.
[2] Bertrand J M et al. (1986) in: Tectonics 5, 955–972.
[3] Bouzid A et al. (2015) in: The Geological Society of America 514.
[4] Bouzid A et al. (2008) in: Comptes Rendus Geoscience 240: 711-722.
[5] Caby R (2003) Journal of African Earth Sciences 37, 133–159.
[6] Liégeois J P et al. (2003) in: Journal of African Earth Sciences, 161–190.
[7] Liégeois J P et al. (1994): Precambrian Research 67: 59-88. (199
[8] Peucat J et al. (2003) in: Journal of African Earth Sciences 37: 229–239.