Miocene to Recent collapse calderas of the southern and central volcanic zones of the Andes and their tectonic constraints

Abstract

Central (18–28° S) and Southern (33–46° S) Andean Volcanic Zones (CVZ and SVZ, respectively) have several Miocene to Recent collapse calderas. We compare their characteristics based on published data to identify how the tectonic variables have influenced their features. Typical calderas of the CVZ are large, have a masked pre-caldera stage, have multiple collapses and a large lifespan, have emitted high volumes of crystal-rich dacitic to rhyodacitic magma, and show a resurgent stage; other calderas with smaller sizes are crystal-poor, rhyolitic and younger, and they do not display resurgence stages. SVZ calderas are typically smaller than those of the CVZ, with generally a long-lived pre-caldera stage, a single collapse history, a wide spectrum of compositions in the same eruptive cycle and rare resurgence. Resurgence is always related to calderas with major axis > 14 km and to magmas with > 26 vol% of crystals. The observed main differences are highly dependent on tectonic variables, such as slab anchoring in the lower mantle and maturity of the subduction zone. Large calderas are related to thick crust, horizontal extension of the upper crust and zones of heat flow peaks. In the CVZ, calderas are also related with a high magmatic flux at the base of the crust and melted magma bodies within the crust, in addition to crustal weakness zones. The SVZ, with lesser crustal thickness, lacks the presence of large magma bodies and thus, also lacks giant caldera complexes.