MECHANISMS OF CONTINENTAL GROWTH IN EXTENSIONAL ARCS - AN EXAMPLE FROM THE ANDEAN PLATE-BOUNDARY ZONE

During the Late Triassic, Jurassic, and Early Cretaceous, an extension al magmatic are was formed in the Andean margin of northern Chile. Plu tons emplaced at ramps within a hinterland-propagating extensional dup lex were fed by dikes that transferred magma through the lower crust f rom a reservoir in the mantle. Phases of volcanism separated phases of plutonism, and our model demonstrates that plutonism was favored only when upper-plate extensional fault systems were active. When they wer e not, dikes cut across inactive faults, and magma rose directly to th e surface during volcanic phases of arc growth.