The links between subduction-zone tectonic activity and volcanism remain fundamental problems in geology. The object of this study is a volume and time-constrained analysis of a large and long-lived volcano in the Central Andes with a view toward evaluating the mass and heat flux in this classic continental subduction zone setting. Aucanquilcha volcano and the surrounding cluster of volcanoes span at least 9.4 million years of volcanic history and constitute an erupted volume of about 170 km3. The preserved record of volcanic edifices from Miocene to present is unparalleled due to a prolonged arid climate. Compositionally and isotopically the Aucanquilcha cluster conforms with regional trends and so is typical of this remarkable continental arc. The approach to this study is: (1) to document changes in volume and composition in time through extensive mapping and radiometric dating; (2) to identify the petrologic processes and crustal reservoirs at each stage and to obtain a mass balance through time; and (3) to calculate the heat budget dictated by the mass flux and evaluate temporal variations in crustal thickening and mafic magma input into the crust. The emphasis is to place all processes in a temporal context through geologic and geochronologic data. It is precisely because volcanism provides sequential sampling of magmatic processes that the planned approach yields significant promise of addressing fundamental unresolved issues pertaining to magmatism in continental arc settings.
