Central Composite Volcanoes—Stratovolcanoes

Abstract

Cenozoic central composite volcanoes with their steep profiles and conspicuous elevations up to 5 km are distinctive of the Central Andes. The most voluminous and long-lived of those volcanoes are located in the back-arc and extend their activity from 13–10 Ma up to 1.2 Ma. They are andesitic to dacitic in composition, with minor contribution of rhyolites and basaltic andesites. They are the result of Strombolian, Vulcanian eruptions, Pelean episodes involving dome collapse, as well as Plinian and phreatomagmatic events. Distinctive in them are the processes of avalanches of detritus, stages of collapse of craters and collapse of domes, as well as lava stages of construction or reconstruction of the building. Their volcanic products belong to high-K calc-alkaline series with a large compositional range, a broad range of aluminosity, and variable enrichments in incompatible large-ion lithophile elements (LILE) and light rare elements (LREE) and variable degrees of the high field strength elements along their long history. Epithermal deposits of basic metals rich in Ag are frequently related. They correspond to deposits of intermediate sulphuration (IS) with high sulfidation manifestations as siliceous deposits bearing As, Sb, Ag, and in some cases exhalative manifestations of S, in cuspidal portions.