Magmatic evolution of the Peruvian Eastern Cordilleran intrusive belt: insights into the growth of continental crust and tectonism along the proto-Andean Western Gondwana

Abstract

The results of a coupled, in situ, laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb study on zircon and geochemical characterisation of the Eastern Cordilleran intrusives of Peru reveal 1.15 Ga of intermittent magmatism along central western Amazonia, the Earth's oldest active open continental margin. The eastern Peruvian batholiths are volumetrically dominated by plutonism related to the assembly and breakup of Pangea during the Paleozoic-Mesozoic transition. A Carboniferous-Permian (340- 285 Ma) continental arc is identified along the regional orogenic strike from the Ecuadorian border (6oS) to the inferred inboard extension of the Arequipa-Antofalla terrane in southern Peru (14oS). Widespread crustal extension and thinning, which affected western Gondwana throughout the Permian and Triassic resulted in the intrusion of the late- to posttectonic La Merced-San Ramon-type anatectites dated between 275 and 220 Ma, while the emplacement of the southern Cordillera de Carabaya peraluminous granitoids in the Late Triassic to Early Jurassic (220-190 Ma) represents, temporally and regionally, a separate tectonomagmatic event likely related to resuturing of the Arequipa-Antofalla block.