Mineralogy, geochemistry and genesis of the Banded Iron Formations (BIFs) of Semna and Abu Marawat areas, northern Eastern Desert, Egypt

Late Proterozoic layered volcanics (metavolcanics) and volcaniclastics associated with Banded Iron Formations (BIFs) occur at Semna and Abu Marawat. As part of the BIFs occurrences in the Eastern Desert of Egypt, their nature arises much debate about their origin. Detailed investigations have been applied to indicate their mineralogy, textures, geochemistry and their genetic significance. The studied BIFs are interbedded concordantly with the topmost part of metabasalt and metatuffites (lentil). The metavolcanics (originally submarine volcanics) form a thick succession of weakly regionally metamorphosed pyroclastics and lava flows of tholeiitic basaltic, basaltic-andesitic and andesitic compositions. Original textures are more or less preserved. Mineral assemblages consist mainly a/quartz (jasper), hematite, and magnetite. It is concluded that the deposition of the BIFs took place in island-arc environs, probably back-arc
basins.

Abu Marawat BlF represents shallower and proximal deposit compared to Semna BIF which represents a deeper and more distal relative to the volcanogenic hydrothermal source. Silica concentrated by biogenic processes is not excluded.