Ages K-Ar de l'Événement Hydrothermal et des Intrusions Associées dans le District Minéralisé Miocène d'Aīn-Barbar (Est Constantinois,Algérie)

The Ain-Barbar district (Edough — Cap de Fer massif, northeastern Algeria) displays numerous microgranitic plugs and several rhyolitic dykes. These intrusives are cross-cut by polymetallic ore veins (Fe-Cu-Zn-Pb), and are hydrothermally altered in association with the mineralization. K-Ar measurements were carried out in order to determine the age of this event. Measurements gave conventional “ages” in the interval 15 to 16 M.Y., as well as two “isochron ages”, respectively at 15.1 and 16.0 M.Y. The 16.0 M.Y. age could be representative for the intrusion of microgranites, and one of the rhyolitic dykes. The 15.1 M.Y. one is clearly the age of the intrusion for two other rhyolitic dykes, and is coeval with the age of their hydrothermal alteration. The 15.1 M.Y. age is equally the one for the hydrothermal alteration affecting previous intrusive rocks. These results are compatible with previous data concerning magmatic events within the Edough — Cap de Fer massif. They show that hydrothermal process occurred very close after the end of intrusion in the Ain-Barbar district. They give also indirect evidence for the age of the last folding event in the area.