The evolution of the Pan African crystalline basement in NE Africa and Arabia

Abstract

The crystalline basement of NE Africa and Arabia has all the geophysical and geological characteristics of continental crust. But, field and petrographic evidence indicate an intraoceanic island arc environment for the mainly volcanoclastic sediments and geochemical data suggest that magmatic products were generated at or above easterly inclined Benioff zones. Some of the mafic-ultramafic masses that lie in NE zones across the region have been identified as ophiolites and the zones are thought to mark the approximate margin of individual arc systems; four or five arc systems are identified. The episodic evolution of these Proterozoic island arcs took c. 600 Ma (1100–500 Ma) before the continental character of the area was attained. As calc-alkaline igneous rocks and intervening ophiolite bodies occur elsewhere in northern Africa, the Pan African island arc model may have wider application.

Age of Feiran basement rocks, Sinai: implications for late Precambrian crustal evolution in the northern Arabian–Nubian Shield

“…Gass 1977;Kroner 1985). One of the most remarkable aspects of this episode of crust formation is the apparent lack of involvement of pre-Pan-African continental crust, especially in the basement exposed east of the River Nile.…”

Osmium isotope systematics of the Proterozoic and Phanerozoic ophiolitic chromitites: In situ ion probe analysis of primary Os-rich PGM

“…The occurrence of ophiolite complexes and their association with calc-alkaline volcanic rocks of island arc affinities have led to the conclusion that subduction processes were responsible for the Pan African mobile belts of NE Africa and Saudi Arabia [11][12][13][14][15].…”

A Lead-isotope study of mineralization in the Arabian Shield

“…Other workers who have contributed to the island arc concept include Al Shanti and Mitchell (1976), Bakor and others (1976), Frisch and Al-Shanti (1977), Nasseef and Gass (1977), Gass (1977), and Schmidt and others (197«n. On the other hand, Garson and Shalaby (1976), El-Shazly and Engel (1978), and Stern (1979) have maintained that whereas the Arabian-Nubian craton has clearly evolved'"an oceanic crustal environment, the region lacks several characteristics that are normally found in island arc systems elsewhere in the world. Instead, they envisage an older Afro-Arabian continent that in the late Precambrian rifted and spread apart to form a proto-Red Sea in a similar location to the present one.…”