Abstract

U/Pb zircon and ⁴⁰Ar/³⁹Ar hornblende ages of medium- to high-grade metamorphic basement rocks from La Vela Bay in the Falcon Basin and of granitic gneiss rocks from a basement inlier in the southeastern Guajira Peninsula, northwestern Venezuela, measured by laser ablation–inductively coupled plasma–mass spectrometry and sensitive high-resolution ion microprobe, document the presence of Meso- to Neoproterozoic crust related to the Putumayo orogen, which probably correlates with the Chibcha terrane, in Colombia. Metawackes, metapelites, and granitic gneisses from these localities showed a high-grade metamorphism peak between 1.0 Ga and 0.98 Ga. Ages of inherited zircon cores of 1212 ± 11 Ma, 1214 ± 10 Ma, 1227 ± 9 Ma, 1366 ± 38 Ma, 1519 ± 9 Ma, and 2707 ± 8 Ma, are interpreted as relicts of detrital igneous grains that were originally incorporated from the Amazon craton into the sedimentary protolith. In addition, ⁴⁰Ar/³⁹Ar ages of hornblende crystals in metapelites preserve younger events between 923 Ma and 916 Ma, which indicate cooling under 530°C after the granulite facies peak. Radiometric ages presented in this study support the idea that these basement rocks probably formed part of a single orogenic belt in western South America, that formed in an active margin located in the northwestern part of the Amazon craton, which gave rise to a continental collision with Baltica during the Neoproterozoic assemblage of Rodinia.