Abstract

Combined strontium and neodymium isotope data on the Mio-Pliocene Cordillera Blanca batholith (9-11” S) are compared with acid plutonic and volcanic rocks of similar age and composition from the central Andes (16-20” S). The Cordillera Blanca magmas show no evidence of contamination by, or remobilisation of, mature continental basement, contrasting strongly with central Andean volcanics where elevated Sr(i) and negative sNd reflect significant reworking of old continental crust. These contrasting along strike variations relate to horizontal shortening in the central Andes and magmatic underplating in the north.