Storage and eruption of near-liquidus rhyolite magma at Cordón Caulle, Chile

Abstract

International audienceThe last three eruptions at the Cordón Caulle volcanic complex, Chile, have been strikingly similar in that they have started with relatively short pre-eruptive warning and produced chemically homogeneous rhyolite to rhyodacite magma with glassy to aphyric texture. These characteristics collectively call for an understanding of the storage conditions leading to the rise and extraction of crystal-poor silicic magma from volcanoes. We have analyzed and experimentally reproduced the mineral assemblage and glass chemistry in rhyolite magma produced in the most recent eruption of Cordón Caulle, and we use these to infer magma storage and ascent conditions. Fe-Ti oxide mineral geothermometry suggests that the rhyolite was stored at ∼870-920 °C. At these temperatures, the phenocryst assemblage (plag∼An37 > cpx + opx > mag + ilm) can be reproduced under H2O-saturated conditions of between 100 and 50 MPa, corresponding to crustal depths between about 2.5 and 5.0 km. The shallow and relatively hot magma storage conditions have implications for the rapid onset, degassing efficiency, and progression from explosive to mixed pyroclastic-effusive eruption style at Cordón Caulle

Puyehue-Cordón Caulle eruption of 2011: tephra fall and initial forest responses in the Chilean Andes

“…The 2011 eruption produced a rhyolite lava flow and pyroclastic flows close to the vent. It sent tephra to the SE to ESE, blanketing parts of the Chilean Andes, central Argentina, and the southern At-1 http://www.volcano.si.edu/volcano.cfm?vn=357150 lantic Ocean (Castro et al 2013). The axis of the tephra plume intersected Route 215 20 km southeast of the vent where tephra deposits were approximately 50 cm thick.…”

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

“…Shaw et al 1968;Walker 1971;Fink 1983;Webb and Dingwell 1990;Dragoni et al 1992;Manley 1992;Fink and Griffiths 1998;Manga et al 1998;Castro and Cashman 1999;Gottsmann and Dingwell 2001;Hess et al 2008;Castro et al 2013). It has been previously reported that the Rocche Rosse behaved as a Bingham fluid during emplacement (Clay et al 2013), which can promote strain localisation and folding.…”

“…Once the flow had cooled sufficiently, a brittle deformational phase dominated, and the flow no longer behaved as a viscous or ductile flow. (Carn et al 2009;Lara 2009;Castro et al 2013;Schipper et al 2013;Tuffen et al 2013). Recent active observations also give new perspectives on the formation of older rhyolitic lavas, such as the Rocche Rosse.…”

“…These processes are all inferred in the Rocche Rosse based on observations made at Cordón Caulle, and the role played by these variable factors may be understated in the reconstruction of other older lava flows. Recent studies (Carn et al 2009;Lara 2009;Castro et al 2013;Schipper et al 2013;Tuffen et al 2013;Bertin et al 2015;Farquharson et al 2015;Magnall et al 2017) of active flows and domes also highlight processes which may not be evident in older flows due to overprinting or lack of exposure.…”

“…Specifically, morphological features observed in real-time eruptions can help to decipher how structures were formed and modified in older flows. Observations of active rhyolite lava effusion at Chaitén and Cordón Caulle (Carn et al 2009;Lara 2009;Castro et al 2013;Tuffen et al 2013) provide a new motivation to revisit the emplacement mechanisms of older rhyolite lava flows such as the Rocche Rosse flow. This study aims to focus on Rocche Rosse flow morphology, satellite observations and structural measurements, using detailed qualitative and quantitative structural measurements to formulate new interpretations of the flow dynamics associated with emplacement of the Rocche Rosse flow.…”