Episodic construction of the early Andean Cordillera unravelled by zircon petrochronology

José Joaquín Jara,Fernando Barra,Diego Morata,Mathieu Leisen,Rurik Romero,Martin Reich

doi:10.1038/s41467-021-25232-z

José Joaquín Jara, Fernando Barra + Show 4 more

Open Access

https://doi.org/10.1038/s41467-021-25232-z

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Abstract

The subduction of oceanic plates beneath continental lithosphere is responsible for continental growth and recycling of oceanic crust, promoting the formation of Cordilleran arcs. However, the processes that control the evolution of these Cordilleran orogenic belts, particularly during their early stages of formation, have not been fully investigated. Here we use a multi-proxy geochemical approach, based on zircon petrochronology and whole-rock analyses, to assess the early evolution of the Andes, one of the most remarkable continental arcs in the world. Our results show that magmatism in the early Andean Cordillera occurred over a period of ~120 million years with six distinct plutonic episodes between 215 and 94 Ma. Each episode is the result of a complex interplay between mantle, crust, slab and sediment contributions that can be traced using zircon chemistry. Overall, the magmatism evolved in response to changes in the tectonic configuration, from transtensional/extensional conditions (215–145 Ma) to a transtensional regime (138–94 Ma). We conclude that an external (tectonic) forcing model with mantle-derived inputs is responsible for the episodic plutonism in this extensional continental arc. This study highlights the use of zircon petrochronology in assessing the multimillion-year crustal scale evolution of Cordilleran arcs.

Highlights

The subduction of oceanic plates beneath continental lithosphere is responsible for continental growth and recycling of oceanic crust, promoting the formation of Cordilleran arcs
The evidence presented in this study, coupled with current knowledge of the tectonic and structural evolution of Gondwana’s southwestern margin, allows us to conclude that the episodic magmatism of the early Andean Cordillera resulted from a multistage, transtensional to extensional subduction setting[21,24,28]
These episodes are better identified and characterised based on zircon petrochronology coupled with whole-rock geochemical analyses (Figs. 2 and 3), and can be associated with significant tectonic changes in the continental margin (Fig. 4)

Summary

Introduction

The subduction of oceanic plates beneath continental lithosphere is responsible for continental growth and recycling of oceanic crust, promoting the formation of Cordilleran arcs. We use a multi-proxy geochemical approach, based on zircon petrochronology and whole-rock analyses, to assess the early evolution of the Andes, one of the most remarkable continental arcs in the world. The Coastal Cordillera comprises an orogenic belt that extends parallel to the Peru–Chile trench for more than 1500 km It was shaped by subduction during multistage, episodic magmatism over more than 100 million years, beginning in the Late Triassic and extending to earliest Late Cretaceous[21,22]. We use a multi-proxy geochemical approach, based on zircon petrochronology and whole-rock analyses, to determine the contributions of mantle-crust-slabsediments to the magma source in order to better understand the early evolution of the Andean continental arc

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Conclusion