Tectonic interpretation of Jabal Eghei area and its regional application to Tibesti orogenic belt, south central Libya (S.P.L.A.J.)

Abstract

The super Tibestian magamatic series (>600 Ma) of the Jabal Eghei area developed on a destructive plate margin and includes calcalkalic gabbro to granite. These rocks are followed by the Eghei magmatic series (570-500 Ma). This series includes post-tectonic alkali granites, widespread in Jabal Eghei and south along the eastern and southern parts of the Tibesti massif, that apparently formed during a period of stress relaxation and were followed by diabasse dikes (500 Ma?) during an aborted rifting stage. Metamorphic rocks of the Jabal Eghei area are present in linear belts trending NNE. The degree of metamorphism increaseseastward from low greenschist facies to upper greenschist and almandine-amphibolite facies. The north-northeast strike of axial planes of isoclinal folds in the metamorphic rocks suggests a WNW maximum compressional stress, followed by late-stage open folding on northwest-southeast axes. The Tibesti massif evolved during Middle to Late Proterozoic as a result of complex subduction processes. It is composed of two orogenic belts, the eastern Tibesti (Eghei area and southward) and western Tibesti (Bin Ghanimah batholith), which were amalagamated during the Early to Middle Cambrian.