Neoproterozoic structural evolution of SE Sinai, Egypt: I. Re-investigation of the structures and deformation kinematics of the Um Zariq and Malhaq Formations, northern Wadi Kid area

摘要

The Wadi Kid area of the SE Sinai comprises Neoproterozoic arc metavolcanics and metasediments bordered to the N, W and S by post-kinematic granitoid plutons. The structure and tectonics of the Kid area remain controversial despite more than two decades of investigations. In this study the structural history and characteristics of the northern part of the Kid area (Um Zariq and Malhaq Formations) are described. The earliest tectonic event, D1, produced upright folds with probably originally WNW-ESE trending hinges. The F1 folding weakens to the north. The main deformation, D2, produced regionally penetrative shallow-dipping S2 foliations and semi-recumbent tight to isoclinal F2 folds. S2 cleavage is a product of pure flattening strain that involved pressure solution deformation mechanism, rather than a shear foliation that involved mylonitization as previously reported. Macroscopic F2 folds are dissected by top-to-SSE low-angle thrusts and mylonite zones that emplaced the high T Um Zariq Formation schists over the low-grade metavolcanics in the southern part of the Kid area. The SSE direction of thrusting is parallel to stretching lineations on the S2 cleavage planes. Later folds include D3 WNW-ESE to E-W trending upright gentle folds and D4 upright gentle N-S to NE-SW trending folds. In contrast to the extensional histories recently proposed this study finds the deformation events in the northern Kid area to comprise a compressional folding and thrusting history.