Metallogenic Map of North Central Tunisia and Eastern Algeria (Bouhlel 2005)

Abstract

Tunisa is the eastern segment of the Atlas mountains ranges formed during the Alpine orogeny. The Atlasic foreland is in the front of the Tellian folded belt Zinc and lead ores of Tunisan Atlassic foreland occur from Triassic to Upper Miocene dolostone and limestone. Five ore-deposits groups can be distinguished: (1) Pb-Zn-Cu-As-Hg in the Tellian belt, (2) Pb-Zn in Upper Miocene strata in Upper Miocene basins; 3) Pb-Zn-Sr in Triassic cap-rocks-type; (4) Pb-Zn in the Upper Cretaceous to Miocene cover of Triassic evaporates domes, or (b) or siderite in Aptian platform carbonate; (5) F-Ba-Pb-Zn in Jurassic platform carbonate. Most of the deposits are similar to the Mississippi Valley-type deposits. Replacement of limestones and open-space fillings in karst cavities are the principal types of ore occurrences; lesser amounts occur as open-space filling of fractures. Ore-forming brines have salinities in the range of 10 to 20 Wt% NaCl eq and temperature in the range of 70 to 200°C. Hydrocarbons as oil fluid inclusions or oil seeps are aundant in most the ore-deposits. For the genesis of the ore-deposits we propose a orogenically-driven circulation of brines in crustal rocks, followed by the ascent and reaction with fluids in the overlaying rocks, as a consequence of the tectonic collisions of the European and African plates.