Petrotectonic characterization of the Central Andean Terrane, Colombia

Abstract

The Central Andean Terrane is a lower Paleozoic metavolcanoclastic-metapelitic belt that extends from the Central Andes of Colombia to northern Peru. On a section across the Central Cordillera of Colombia, the terrane consists mainly of amphibolitic schists and graphitic schists that range from greenschist facies to epidote-amphibolite facies. The mineral assemblages depict one prograde metamorphic event. Schists are isoclinally folded and, toward the western margin of the terrane, foliation is transposed. This transposition is probably related to overthrusting of the Amaime Terrane, which lies west of the Central Andean Terrane. Major and trace element geochemistry reveals two distinct sources for the terrane's protolith: an intra-oceanic island arc, and a continental margin. Accretion and metamorphism of the terrane took place in Late Silurian-Early Devonian time. Based on current Paleozoic reconstructions, two models of tectonic evolution of the Central Andean Terrane are presented here, both involving closure of a back-arc basin. The first model is within an Andean-type margin setting and the second is within a continental collision setting.