Zircon U-Pb ages of super-units in the Coastal batholith, Peru: implications for magmatic and tectonic processes.

Zircon U-Pb ages on 50 plutonic samples from super-units in the Lima, Arequipa, and Toquepala segments of the Peruvian Coastal batholith range from 188 to 37Ma, revealing previously unrecognized Jurassic elements. The Jurassic plutons represent a distinct, time-defined, continental arc separated from the Cretaceous arc by a quiescent period of 50Ma. Only 4 of the 50 samples have discordant zircons, and these are all from the Arequipa and Toquepala segments. This regionally limited discordance, interpreted to be due to inherited radiogenic Pb from the Precambrian basement, suggests that there are fundamental differences in the nature of the crust beneath the Lima and the Arequipa/Toquepala segments. -from Author