ملخص
Abstract
As part of the NE-trending Mourizidie Shear Zone in south-central Libya (south of Mourizidie pass), four units representing Preccambrian basement rocks (metasediments) were mapped during field work: phyllites (metaclaystone); metapelites (metasiltstone); pasmmites (metasandstone) and Quartzites. Granitic bodies of various sizes (few meters to hundreds of meters) are found throughout the study area. The metasediments and granites are both intruded by veins and dikes having an overall NE trend. Four Palaeozoic sedimentary units were mapped within the study area. The concidence of the S1 foliation with the S0 of the original bedding of the protolith is a proof that the S1 foliation is caused by deep burial. The petrographic description of the minerals in thin section shows an assemblage of sericite, muscovite and biotite, all representing a sub-greenschist facies to greenshcist facies. This low grade metamorphism helped in preseving the original sedimentary structures of the protolith, thus helping in identifying the original bedding plane S0. Faults observed in the field or traced on aerial photograhs belong to three major trend: NE, NNE, and ENE. Folds are extremely diverse in shape, attiude and tightness, thus their classification is equally diverse. This diversity is observed in the field even within a distance of no more than few meters. The isostatic rebound of the basement could have caused this great difference in the attitude of the folds, especially at considerable depths characterised by a kinematically ductile, restricted and contained settingAt least two phases of deformation are present in the area. D1 is marked by the generation of S1, while D2 is marked by the first folding F1 caused by the isostatic rebound he generation of S2 foliation as fan cleavage is directly related to the F1 folding. Some folds underwent refolding, which lead to an F2 phase of folding.Sequential schematic structural model is proposed to explain the structural history of the study area. This model should be tested through intensive detailed field work large scale map in nearby areas.