0 Academic des sciences / Elsevier, Paris GComat&iaux / Ceomaterials Nature, origine et holution des fluides dans le district minier de la caldeira d’Oued B&f (Nefza, Tunisie septentrionale) Nature, origin and evolution offluids in the mining district of the Oued B&f caldera (Nefza, northern Tunisia) Fouad Talbi, Najet Slim-Shimi, Said Tlig, Fouad Zargouni Groupe Geodynamique et transfer& de mat&es, departement de gealogie, faculte des sciences de Tunis, campus universitaire, 1060 Tunis, Tunisie (Recu le 26 mai 1998, accepte apres revision le 16 novembre 1998) Abstract-Fluid inclusion studies were undertaken on quartz, fluorite and calcites in the Oued Belif caidera ore district in northern Tunisia. Two main groups of inclusions were distinguished: a fluid inclusion group, of magmatic origin, with a temperature higher than 350 ‘C and salinity higher than 30 wt % NaCl; and a group of mixing between magmatic and meteoric fluids with temperatures and salinities ranging from 150 to 250 “C and from 15 to 25 wt % NaCl, respectively. These two groups result from hydrothermal circulations of respectively, “porphyry copper” and epithermal systems; this is confirmed by the nature of the alteration. (0 Academic des sciences / Elsevier, Paris). fhdd iaclusions / caldera / porphyry phase / epithermal activity / magmatism / alteration / Chd Bdif/ Tunisia R&urn6 - L’etude des inclusions fluides dans la caldeira d’Oued Belif, au nord de la Tunisie, a ete effect&e principalement sur des cristaux de quartz et, accessoirement, de fluorine et de calcite. Deux familles principales d’inclusions fluides sont distinguees : un groupe, d’origine magmatique, 2 temperatures et salinites respectivement superieures a 350 “C et a 30 % eq. NaCI, et un groupe de melange entre fluides magmatiques et meteoriques, avec des temperatures de I’ordre de 150-250 “C et des salinites d’environ 15 a 25 % eq. NaCI. Ces deux groupes correspondent P des fluides mineralisants, respectivement de type porphyre cuprifere et epithermal, dont on retrouve egalement les marques au travers des alterations. (0 Academic des sciences / Elsevier, Paris). inclusions fluides / caldeira / porphyre cuprifkre / activite Cpithermale / magmatisme / alteration / Oued BClif / Tunisie Abridged version Introduction The Oued Belif district is located in the north of Tunisia, ten kilometers north of Nefza city yigure 1). It contains several ore deposits illustrating the direct association between mineraliza- tion and calcalkaline magmatism of the Tunisian Alpine chain (Gottis and Sainfeld, 1952; Nicolini, 1968; Crampon, 1971; Rouvier, 1977; Negra, 1987; Halloul, 1989; Dermech, 1990 and Slim-Shim& 1992). The l/50 000 geological map (Rouvier, 7988) of the studied area shows four lithostratigraphic groups: - marls and limestones, including Abiod Formation (Upper Cretaceous), El Haria Formation (Early Eocene), Metlaoui Formation (Middle Eocene) and Souar Formation (Middle Eocene to Early Oligocene); Note p&sent&e par Michel Durand-Delga. C. R. Acad. Sci. Paris, Sciences de la terre et des plan&es / Earfh & Planetary Sciences 1995’. 328,153-160