Timing and kinematics of Eburnean tectonics in the central Reguibat shield, Mauritania

摘要

The Reguibat Shield of north Mauritania comprises a western Archaean terrane dominated by gneisses and granitic rocks and an eastern Eburnean terrane largely made Lip of Palaeoproterozoic granitic and metasedimentary rocks. These were juxtaposed during the c. 2.1-2.0 Ga Eburnean Orogeny, which formed an approximately north-trending front contiguous with the Eburnean belt of the Leo Shield in equatorial West Africa. Geological surveying in the Sfariat region of the Reguibat Shield has shown that a metamorphosed Palacoproterozoic continental margin succession has been intruded by and intercalated with synorogenic granitoids and transported SW onto the Archaean foreland during sinistral oblique Collision preserved as strongly partitioned D, shortening and D-2 strike-slip-dominated transpression within the Sfariat Belt, This was subsequently affected by retrogressive dextral transcurrent deformation and the propagation of the en echelon Imarkene and Tmeimichat fault zones. Laser ablation and conventional thermal ionization mass spectrometry U-Pb geochronology were carried out on five samples of granitic rock and migmatitic gneiss from the region, which reveal that anatexis and sinistral transpression took place between c. 2117 and 2064 Ma. Timing and kinematics of the Eburnean event in the Reguibat Shield are similar to those for the Leo Shield, which underwent SW-directed sinistral transpression at this time.