Tectonic and sedimentary history of the neoproterozoic metavolcanic–volcaniclastic rocks of the El-Dabbah Group, Central Eastern Desert, Egypt

Abstract

The El-Dabbah Group is a >7500 m-thick sequence of metavolcanic rocks, volcaniclastics, and banded iron-formation located within the Nubian Shield, Central Eastern Desert, Egypt. The sequence preserves lower greenschist-facies island arc rocks. We used detailed mapping to reconstruct the stratigraphic and tectonic history of the El-Dabbah Group and the surrounding sedimentary basins. The El-Dabbah Group was identified as deposition at central rift zone of an oceanic island arc and was overlies by the subaerial sedimentary rocks (the Atshan Formation and the Hammamat Group). Four faulting were distinguished within the El-Dabbah area: (1) top-to-the-S low-angle thrusting; (2) NNE side down normal faulting; (3) sinistral displacement on north–south faults; and (4) WNE trend N-side-down normal faulting with the Hammamat Group. We obtained the crystallization ages of a granite (638.1 ± 2.9 Ma) and a quartz porphyry (659.6 ± 3.0 Ma). The detrital zircon age of the Hammamat Group show peaks at 650, 680, and 790 Ma. These evidences suggest, three sedimentation-deformation stages were identified in this area. Stage 1 involved sedimentation of island-arc-derived volcaniclastic rocks at 770-700 Ma and to thrust related accretion at 700–680 Ma. Stage 2 involved collisional and transtensional deformation related to formation of the subaerial basin that contains the Atshan Formation at 670-640 Ma, the normal fault, the strike-slip fault and granite intrusion during 660–620 Ma. Stage 3 involved orogenic collapse, regional strike-slip-related sedimentation and deformation of the Hammamat Group at 610–570 Ma. We show that the El-Dabbah Group records a history of oceanic island arc accretion, collision, and collapse within the northern East African Orogeny during 770–570 Ma in Neoproterozoic.