A high-resolution U-Pb zircon geochronological study of plutonic units
along the south Peruvian margin between 17 degrees and 18 degrees 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 similar to 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 Cachios 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 similar to 175 Ma, and the relation with extensional tectonics that
prevailed along the Central Andean margin during Pangaea break-up. (C)
2012 Elsevier B.V. All rights reserved.