The Red Sea: History and associated mineralization

The Red Sea rifting history has been subdivided into four major periods from the beginning of its evolution, about 70 Ma ago; they are respectively: Cretaceous to Eocene (pre-rift), Oligocene (rift formation), Miocene (Red Sea depression), Pliocene to Recent (oceanic spreading). In this review several original points are highlighted: (1) The geological events – marine transgressions and regressions, tectonism, magmatism – are not synchronous in the northern and central areas on one side and in southernmost areas on the other side. Furthermore, some events are characteristic of each evolutionary stage.(2) Stretching and concomitant thinning of the continental lithosphere, together with massive basic intrusions leading to the formation of intermediate crust, must have been the dominant processes during the first phase of the Red Sea opening, i.e. during the Miocene.(3) Since the Pliocene an axial area has been formed by true oceanic spreading, which did not start at the same time along the whole length of the Red Sea.The Red Sea evolution must have been progressive and continuous but some more abrupt events must also have occurred as shown by unconformities. The mineralization, which often appeared during these events, also shows an evolution in composition, the type of mineralization and their specific distribution: (a) phosphate beds and hyperalkaline intrusive complexes with REE, F, U, Nb and Ta were formed during Cretaceous to Eocene times;(b) ‘Red-Bed’-type mineralization with Pb-Zn, Cu, U and oolitic iron ores was formed during the Oligocene;(c) ‘Mississippi-Valley’-type, or ‘unstable sedimentary cover overlying basement’-type mineralization with Pb-Zn (Ba, F, Cu, Ag) occurring as stratiform and vein-type mineralization, and with Mn and/or Ba mineralization, were formed in the early Miocene.(d) Fe-Mn (Ba) beds and Recent to Actual Zn-Cu-Ag-Mn mineralized sediments are found within axial deeps, such as Atlantis II.The descriptive data permit the exhalative sedimentary classification of many of these mineralization types, their relation with magmatism (hyperalkaline complexes) and more generally their origin and the source of metals. Finally, if such an evolution of the types of mineralization can be found in some Phanerozoic rifts, this is not the case for older Proterozoic ones.