Eburnean and Pan-African granitoids and the Raghane mega-shear zone evolution: Image analysis, U–Pb zircon age and AMS study in the Arokam Ténéré (Tuareg shield, Algeria)

• Published in: Journal of African earth sciences (1994) Vol. 60; no. 3; pp. 133 - 152
• Main Authors: Nouar, O., Henry, B., Liégeois, J.P., Derder, M.E.M., Bayou, B., Bruguier, O., Ouabadi, A., Amenna, M., Hemmi, A., Ayache, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-05-2011; Elsevier
• Subjects: Anisotropy; Earth Sciences; Eburnean; Magnetic susceptibility; Pan-African; Petrography; Remote sensing; Saharan metacraton; Sciences of the Universe; Shear zone; U–Pb zircon age; Anisotropy; Pan-African; U–Pb zircon age; Eburnean; Remote sensing; Saharan metacraton; Shear zone; Magnetic susceptibility; U-Pb zircon age
• ISSN: 1464-343X; 1879-1956
• DOI: 10.1016/j.jafrearsci.2011.02.007

► The studied region lies across the western boundary of the Saharan metacraton. ► Eastern basement protolith is dated at 1918±Ma and gneissification at 580±26
Ma. ► AMS fabric of the Eburnean granitic gneiss is related to the Pan-African tectonics. ► Pan-African granites are dated at 595±3
Ma and 582±3
Ma. ► AMS fabric is late-magmatic in most Pan-African plutons.
In the Arokam Ténéré, the three studied massifs of granitoids are located around the N–S oriented Raghane mega-shear zone, which separates two of the main domains of the Tuareg shield, the Saharan metacraton and the Central Hoggar. The field observations, AMS analyses and U–Pb zircon dating were completed by a study of Landsat images because of the scarcity of outcrops in several parts of the studied area.
The image analysis allows to distinguish Arokam-East and Abdou granitoids in the eastern plutonic complex. It has also shown that the western plutonic complex corresponds to two different intrusions: the Yvonne granite and granodiorite. This is confirmed by the magnetic fabric that presents different characteristics in the different granitoids. U–Pb zircon dating and field observations show that the Arokam-West basement granite is much older (1915
Ma) than the Hanane granodiorite (582
Ma) in the central plutonic complex. Arokam-East and -West granites then belong to the Eburnean basement. The magnetic fabric of these granites is mainly associated with a post-magmatic deformation, probably of Pan-African age. Yvonne granodiorite is likely contemporaneous of the main displacement along the Raghane shear zone. The Yvonne granite (594
Ma) and Hanane granodiorite have a fabric similar to that previously obtained in most plutons of the Tiririne area. This fabric is related to the regional stress field, associated with the activity of the Raghane shear zone, during the late-magmatic phase in the plutons. On the contrary, the magnetic fabric of the Abdou pluton is still reflecting only the magma flow.