Metamorphism and tectonics of a Pan-African terrain in southeastern Sinai |
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| Authors: | APS Reymer |
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| Institution: | Institute of Earth Sciences, The Hebrew University of Jerusalem Israel |
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| Abstract: | The Precambrian crystalline basement of Sinai represents a low-pressure metamorphic terrain intruded by large volumes of granitic rock. Based on detailed fieldwork, a general assessment of the metamorphic and tectonic history of the Wadi Kid area, southeastern Sinai, is presented. Three lithostratigraphic units can be traced over the whole area; the Umm Zariq Formation (arkoses, greywackes, pelites), the Tarr Formation (dolomitic-calcareous rocks) and, unconformably overlying the previous two units, the Heib Formation (flows, pyroclastics, conglomerates). D1 deformation of this 3.5 km thick sequence resulted in upright folds, with changing strike of the axial planes from NE to NW across the area. Low-grade conditions prevailed during this phase. D2 produced recumbent folds and a subhorizontal cleavage, leading to transposition of D1 structures in the higher grade parts of the area. Metamorphism reached its peak conditions around D2. Pressures are estimated at 2.5–3.5 kb, whereas temperatures vary from 450–660°C. In the central Wadi Kid area, garnet, staurolite, cordierite and andalusite occur in metapelitic rocks. Highest grade rocks are syn-D2 andalusite—K-feldspar gneiss diapirs. Metamorphic zones are shallow dippin and form a domed pattern. Most of the metavolcanics and the syntectonic and late tectonic plutonic rocks belong to the calc-alkaline suite.The Kid Group sediments and volcanics were deposited in a shallow basin and subaerially, respectively, probably on older sialic basement. This basement is at present not exposed because post-orogenic uplift directly after the Pan-African event was relatively small (3–6 km). Metamorphism and the D2 formation phase can both be related to a rising (mafic?) diapir. The Sinai Peninsula may have been a continental margin or a cratonized, mature island arc, in Late Proterozoic times. |
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