K-Ar ages of metamorphic rocks from the Puerto Berrio area in the Antioquia province of the Central Cordillera,central Colombia.

Abstract

The metamorphic rocks considered as Precambrian are exposed in the Puerto Berrio area situated in the eastern edge of the Antioquia province of the Central Cordillera, central Colombia. Discordant K-Ar ages of 278 m. y. on hornblende and 127 m. y. on biotite were obtained for a gniessose amphibolite and a biotite gneiss, respectively, in the metamorphic mass of the area. The hornblende age might indicate that the metamorphic rocks in the area have been strongly subjected to late Paleozoic metamorphism as well as those widely exposed in the Antioquia province of the Central Cordillera. The biotite age might indicate that the metamorphic rocks in the area have been subjected to the effect of late Jurassic-Cretaceous orogeny.