Autores Ckelar: Daniel Díaz, Luis E. Lara
Otros autores: Maximiliano Pavez, Heinrich Brasse, Gerhard Kapinos, Eva Schill
Revista científica: Volcanology and Geothermal Research
Abstract
The active volcanic arc of the Andes is controlled by subduction of the Nazca and Antarctic Plates beneath the South American Plate. The Southern Volcanic Zone is the segment with the most active volcanoes in the Andes and the one where volcano-tectonic interactions are more evident. Magmatic fluids are there channeled through the brittle crust by faults and fractures, becoming an important region for understanding the mechanisms associated with melt migration and storage in subduction zones. The Liquiñe–Ofqui Fault System and Andean Transverse Faults, control the overall architecture of the volcanic arc and play an important role on magmatic transport and compositional partitioning. Evidence of this is the oblique chain composed of Villarrica, Quetrupillán and Lanín stratovolcanoes and a number of minor eruptive centers, where a wide range of magma compositions have been erupted with basalts and basaltic andesites dominating the suite. We used long–period and broad–band magnetotelluric stations deployed surrounding of Villarrica volcano to investigate the implications of crustal faulting and volcanism and their consequence on crustal reservoirs. Inversion of the data was used to generate three–dimensional electrical resistivity models. The resistivity distribution shows the upper crust as highly resistive, but below and east of Villarrica volcano, the model suggests the presence of a magmatic reservoir at shallow crustal levels (between 1.5 and 3 km b.s.l.), possibly corresponding to a transient magma storage. Meanwhile, the middle crust contains several intermediate to low conductive features interpreted as fluid pathways and/or melt storage regions, respectively, revealing the important role of fault systems. The lower crust also contains low resistivity zones indicating the presence of partial melt and/or fluids, associated with deep reservoirs (8–20 km), with a significant proportion of them likely non eruptible parts. This would suggest that melt is accumulated as highly crystallized mush or disconnected melt pockets and highlight the complex vertical extent of the structurally-controlled plumbing systems even in thin crust settings.