Late Proterozoic tectonic terranes in the Arabian‐Nubian Shield and their characteristic mineralization

An extensive terrane of continental gneisses and supracrustal metasediments extends from the Nile valley westwards between southern Egypt and northern Kenya, and also occurs in southern Ethiopia, Somalia and parts of the easternmost Arabian Shield. Mica–beryl pegmatites and associated kyanite are characteristically developed. The gneiss terranes were regionally affected by metamorphic overprinting and remobilization thus masking their true age which is considered to be Middle Proterozoic or older on the basis of isotopic and petrological evidence. Between the continental terranes volcanosedimentary–ophiolite sequences and intrusive synorogenic calc‐alkaline batholiths, post‐tectonic and anorogenic calc‐alkaline to alkaline plutons occur in an area 700 km in width by over 2700 km long between Sinai and northern Kenya. Within this region of oceanic crust seven ophiolite‐ or shear‐bounded terranes are recognized which developed around 900 to 600 Ma, through closure of island‐arc and associated volcanism and sedimentation, the oldest being in the southeast. Hydrothermal gold mineralization is widespread but restricted to the oceanic terranes, and volcanogenic base metal sulphide deposits are lithologically–tectonically controlled and preferentially located parallel to certain ophiolite margined plate boundaries.