Lead


Lay summary
This proposal studies the pre-Andean evolution of the South American active margin in Peru using geochemical and geochronological tools.
We intend to focus on three well-defined topics of general interest:
Subproject A Carboniferous to Jurassic magmatism of the Eastern Cordillera: The on going PhD project will continue to characterize the magmatic evolution, timing and geodynamic significance of an 800 km long magmatic belt in the Eastern Cordillera, which is composite in terms of age, melt sources and geodynamic setting.
Subproject B The birth and death of an intracontinental rift: the Mitu Group in southern Peru: The southern part of the Eastern Cordillera is characterized by development of a large Triassic to early Jurassic intracontinental rift (Mitu Group). With a PhD project, we plan to study the timing and rates of crustal thinning, basin subsidence and magma emplacement. We hope to provide answers to the questions of when and how transtension and finally rifting replaced Carboniferous orthogonal subduction and magmatism, was the crustal thinning caused by a highly oblique direction of the subducting plate or by the response of the South American continent to Pangea breakup. Rifting terminated in the early Jurassic after emplacement of an anorogenic peralkaline volcanic and plutonic suite, offering insight into the contribution of crustal vs. mantle sources over time in an evolving and eventually aborted continental rift.
Subproject C The Jurassic magmatic arc in southwestern Peru: The Triassic-Jurassic transition is characterized by the abortion of the Mitu rift and renewed subduction-related magmatism in a magmatic arc along the present-day coastline, and in the interior of the Arequipa massif south of 12°S. Numerous continuous sections indicate that an early bimodal volcanic suite may be transitional from extensional/transtensional tectonics and that calc-alkaline arc magmatism resumes in the middle Jurassic. We intend to study, with a PhD project, the transition from the extensional geodynamic scenario forming the Mitu Rift to renewed (orthogonal) subduction and subsequent magma production, in terms of timing and sources of magmatic liquids. Understanding the timing and nature of Jurassic arc magmatism will also shed light on the reasons for the lack of Jurassic rocks in the enigmatic “craton-free zone”, north of 12°S (north of Lima).