Morphology, Effusion Rates, and Petrology of Postglacial Lavas of Laguna del Maule Volcanic Field, Chilean Andes, and Implications for Their Plumbing System

We analyzed the dimensions, morphology, and petrography of nine postglacial lava flows, ranging from andesites to rhyolites, located at the Laguna del Maule Volcanic Field in the Southern Andes of Chile. Our data were used in conjunction with theoretical models of magma ascent and lava flow advance to estimate time scales of lava emplacement, effusion rates, magma chamber volume, and conduit dimensions. The results indicate that the parameters of these past eruptions correspond to eruptions of months to a few years in duration, with peak effusion rates <100m(3)/s, and were fed by magma chambers of 6 to 30km(3) and conduits of radius 20 to 70m. Thermobarometric results indicate crystallization pressures between 260 and 450MPa and temperatures of 780 to 1060 degrees C for the analyzed units. These results, taken together with recent geophysical studies, suggest that the most likely scenario, in case of an eruption, corresponds to a medium size eruption (0.1-1km(3)). Initial activity would be explosive, followed by the extrusion of lava flows that can last several months.