Mesozoic arc magmatism along the southern Peruvian margin during Gondwana breakup and dispersal

A high-resolution U–Pb zircon geochronological study of plutonic units along the south Peruvian margin between 17° and 18°S allows the integration of the geochemical, geodynamic and tectonic evolution of this part of the Andean margin. This study focuses on the composite Jurassic–early Cretaceous Ilo Batholith that was emplaced along the southern Peruvian coast during two episodes of intrusive magmatism; a first period between 173 and 152 Ma (with a peak in magmatic activity between roughly 168 and 162 Ma) and a second period between 110 and 106 Ma. Emplacement of the Jurassic part of the composite Ilo Batholith shortly post-dated the accumulation of the volcanosedimentary succession it intruded (Chocolate formation), which allows to estimate a subsidence rate for this unit of ~ 3.5 km/Ma. The emplacement of the main peak of Jurassic plutonism of the Ilo Batholith was also closely coeval with widespread and repeated slumping (during deposition of the Cachíos Formation) in the back-arc region, suggesting a common causal link between these phenomena, which is discussed in the context of an observed 100 km trenchward arc migration at ~ 175 Ma, and the relation with extensional tectonics that prevailed along the Central Andean margin during Pangaea break-up.

► The Ilo Batholith was emplaced during two episodes of intrusive magmatism.
► A peak in magmatic activity is observed between 168 and 162 Ma.
► This plutonism was coeval with widespread and repeated slumping in the back-arc.
► We observe a 100 km trenchward arc migration at ~ 175 Ma.
► We suggest a causal link between these phenomena in an overall extensional setting.