Banded iron-formations of late Proterozoic age in the central eastern desert, Egypt: Geology and tectonic setting

In the central Eastern Desert of Egypt, deposits of iron-formation of the Algoma type occur as sharply defined stratigraphic units within layered volcanogenic rocks of late Proterozoic age. The volcanic sequence is characterized by interfingering and repetition of rocks of dominantly andesite-basalt composition and by tectonically juxtaposed ophiolitelike assemblages; it is intruded by voluminous syntectonic granodiorite-tonalite and post-tectonic potassic granite. The iron deposits were formed as chemical precipitates during lulls in dominantly subaqueous, calc-alkaline volcanism, apparently in an intraoceanic island-arc environment. During subsequent complex telescoping of the sequence, the rocks were transported along thrust faults and are now allochthonous.