Rocas piroclásticas asociadas conla formación de la caldera de Guayabo, Cordillera de Guanacaste, Costa Rica

Abstract

The volcanic depression of the Guayabo calderas was emplaced during several collapses between 1.5 to 0.6 m.y. ago. These eruptions are recorded in a series of pumice-ash flows, pyroclastic surges and air-falls tuffs, called Guayabo Formation, that are exposed in the western and southern part of the Guayabo caldera rim. The pyroclastic-flow sheets represent more than 30 km³ of dacitic to rhyolitic magma associated to crystal fractionation processes. The volumen and also the energy of the  eruptions decrease in the time. Microprobe and geobarometric analyses of amphiobole suggest that the level of the magma chamber was less than 5 km.