Middle Triassic to Jurassic convergence at the north-western margin of Gondwana: insights from the Central Cordillera of Colombia

Abstract

ABSTRACT The northern Andes are crucial for understanding the processes associated with the break-up of Pangea and its impact on the evolution of the Pacific margin of South America. Despite its importance, the origin and significance of mafic magmatism and its relationship with the Permian arc-related granitoids in the northern Andes remains controversial. To address this, we examined the Tierradentro gneisses and amphibolites, which comprise Permian-Triassic lithologies that may help resolve this controversy. Our study focuses on representative lithologies of the Central Cordillera of Colombia, including mylonitized granitoids, metabasites, metapelites, and serpentinites, to shed light on the history of the western margin of Gondwana during and after its break-up (~230 to 200 Ma). To investigate these lithologies, we conducted field observations, petrographic analyses, U-Pb dating of zircons, and whole-rock geochemical, Nd, Pb, and Hf isotopic analyses. Our results show that mylonitized mafic rocks with Triassic crystallization ages (ca. 236 Ma) intruded Permian granitoids. Furthermore, these mafic and felsic rocks were intruded by Jurassic calc-alkaline batholiths. The geochemical and isotopic signatures of these rocks indicate their subduction-related extension origin and further mylonitic deformation, possibly during the Jurassic strike-slip movement of the Farallón plate relative to western Gondwana. The Otú-Pericos fault bounds these rocks to the west, where Jurassic metabasic and metapelitic sequences with serpentinites interleaved and formed in a collisional setting. Our findings suggest that the Pacific margin of northern South America underwent subduction-related extension during the middle Triassic and evolved towards a more oblique convergence during the Jurassic.