Braschi, E.

Casalini, M.

Francalanci, L.

Petrone, C. M.

Tommasini, S.

English

Florence Research

Geophysical Research AbstractsVol. 21, EGU2019-18571, 2019EGU General Assembly 2019© Author(s) 2019. CC Attribution 4.0 license.Interplay between rapid mixing and short storage at a steady-statevolcanoChiara Maria Petrone (1), Eleonora Braschi (2), Lorella Francalanci (2,3), Martina Casalini (3), and SimoneTommasini (3)(1) The Natural History Museum, Department of Earth Sciences, Cromwell Road, SW7 5BD, London, United Kingdom, (2)CNR-IGG Sezione di Firenze, Via G. La Pira, 4, 50100 Firenze, Italy, (3) Università degli Studi di Firenze, Dipartimento diScience della Terra, Via G. La Pira, 4, 50100 Firenze, ItalySteady-state volcanoes are characterised by equilibrium between the rate of magma input and output in an openconduit system resulting in compositionally homogeneous magmas. The equilibrium status can last for tens tothousands of years. The Present-day activity of Stromboli volcano (Italy) is typical of a steady-state volcano, witha shallow magmatic reservoir (hp-magma) continuously refilled by more mafic magma (lp-magma) at a constantrate, accompanied by mixing, crystallisation and eruption. In the effort to clarify timescale and dynamics of theplumbing system at the establishment of the Present-day steady-state activity, we investigated the Post-Pizzo (PP)pyroclastic sequence and one of the Early Paroxysms (EP) of the Present-day activity.Complex compositional zoning of clinopyroxenes from both PP and EP indicates the existence of threedifferent melt domains: a high-Mg# proto-lp recharging magma, a low-Mg# proto-hp resident magma, and atransient intermediate-Mg# magma. Repeated injections of the proto-lp magma in the shallow proto-hp magmareservoir originate turbulent flow fields and mixing regimes that produce the three melt domains. However,efficient (days to a few years) stirring and melt homogenisation (homogenisation time < residence time) allows themagmatic system to regain the pre-input proto-hp composition. This regime was established during the PP periodand typically characterizes the Present-day activity (Petrone et al., 2018 EPSL).Geospeedometry applied to Fe-Mg diffusion in clinopyroxene (NIDIS model, Petrone et al., 2016 Nat.Comms.) allows to calculate a total residence time from 1 to ∼50 years during PP and EP periods, from the arrivalof the mafic magma in the shallow system until the eruption. The mafic triggering event of the feeding proto-lpmagma occurring within few months to a few days before eruption is recorded by some clinopyroxenes from thePP. Finally, some clinopyroxene portions captured the on-going mixing and homogenisation process between theproto-lp and the proto-hp magmas leading to the eruption in only a few days. The interplay between rapid mixingand short storage timescales as captured by the lifetime history of clinopyroxenes of a typical steady-state volcano,such as Stromboli, suggests that this might be a common dynamics of the plumbing system of steady-statevolcanoes (Petrone et al., 2018 EPSL).

Interplay between rapid mixing and short storage at a steady-state volcano

https://flore.unifi.it/bitstream/2158/1164625/1/EGU2019-18571.pdf

Interplay between rapid mixing and short storage at a steady-state volcano

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