TY - JOUR

T1 - Viscosity of high-K basalt from the 5th April 2003 Stromboli paroxysmal explosion

AU - Misiti, V.

AU - Vetere, F.

AU - Mangiacapra, A.

AU - Behrens, H.

AU - Cavallo, A.

AU - Scarlato, P.

AU - Dingwell, D. B.

N1 - Funding Information: This work has been supported by the Gruppo Nazionale per la Vulcanologia 2005–2007 framework programme, Project n. V2-UR8 of P. Scarlato and by the EU Volcanic Dynamics Research and Training Network. A. Mangiacapra would like to thank Kai-Uwe Hess for the technical support during micropenetration measurements. We thank Guido Ventura for the comments and suggestions of an early version of the manuscript. We would also like to thank D. Giordano for his helpful comments. Finally we would like to thank Zhang and a second unknown reviewer for helpful comments improving the quality of the paper.

PY - 2009/3/30

Y1 - 2009/3/30

N2 - The 5th April 2003 paroxysmal event was the strongest explosion that has occurred at Stromboli in the last 50 years. This event lasted only few minutes and was characterised by two violent explosions, followed by gas and pyroclast emission. In order to constrain models of the dynamics of the paroxystic event the viscosity of anhydrous and hydrous Stromboli high potassium (HK)-basaltic melts have been measured. Viscosity has been investigated in the low viscosity range with the falling sphere method at superliquidus temperatures (1423 to 1673 K) and 0.5 GPa and in the high viscosity range with micropenetration near the glass transition temperature (723 to 1035 K) at atmospheric pressure. Falling sphere experiments were performed in a piston cylinder apparatus with melts whose water content varies from nominally anhydrous (0.02 wt.% H2O) to 4.16 wt.% H2O. The combination of high- and low-viscosity data permits a general description of the viscosity as a function of temperature and water contentusing a modified Tamman-Vogel-Fulcher equation. Using these new viscosity data, an estimation of the flow regime and magma velocity is performed. Our data suggest that the ascent of magma from the 7-8 km deep reservoir to a shallower reservoir located at about 3 km of depth, may occur within minutes. Moreover, we infer a turbulent flow regime. Finally, our estimates of the ascent velocity agree qualitatively with results from petrological studies (e.g. [Bertagnini, A., Métrich, N., Landi, P., Rosi, M., 2003. Stromboli volcano (Aeolian Archipelago, Italy): an open window on the deep-feeding system of a steady state basaltic volcano. Journal of Geophysical Research 108, 2336-2350.]), which indicate a turbulent flow regime and rapid ascent velocities such to inhibit volatile-loss-induced crystallization. We conclude that hazard evaluation at Stromboli Island should incorporate the likelihood of very rapid ascent of less-evolved melts from depth.

AB - The 5th April 2003 paroxysmal event was the strongest explosion that has occurred at Stromboli in the last 50 years. This event lasted only few minutes and was characterised by two violent explosions, followed by gas and pyroclast emission. In order to constrain models of the dynamics of the paroxystic event the viscosity of anhydrous and hydrous Stromboli high potassium (HK)-basaltic melts have been measured. Viscosity has been investigated in the low viscosity range with the falling sphere method at superliquidus temperatures (1423 to 1673 K) and 0.5 GPa and in the high viscosity range with micropenetration near the glass transition temperature (723 to 1035 K) at atmospheric pressure. Falling sphere experiments were performed in a piston cylinder apparatus with melts whose water content varies from nominally anhydrous (0.02 wt.% H2O) to 4.16 wt.% H2O. The combination of high- and low-viscosity data permits a general description of the viscosity as a function of temperature and water contentusing a modified Tamman-Vogel-Fulcher equation. Using these new viscosity data, an estimation of the flow regime and magma velocity is performed. Our data suggest that the ascent of magma from the 7-8 km deep reservoir to a shallower reservoir located at about 3 km of depth, may occur within minutes. Moreover, we infer a turbulent flow regime. Finally, our estimates of the ascent velocity agree qualitatively with results from petrological studies (e.g. [Bertagnini, A., Métrich, N., Landi, P., Rosi, M., 2003. Stromboli volcano (Aeolian Archipelago, Italy): an open window on the deep-feeding system of a steady state basaltic volcano. Journal of Geophysical Research 108, 2336-2350.]), which indicate a turbulent flow regime and rapid ascent velocities such to inhibit volatile-loss-induced crystallization. We conclude that hazard evaluation at Stromboli Island should incorporate the likelihood of very rapid ascent of less-evolved melts from depth.

KW - Basalt

KW - Falling sphere

KW - Micropenetration

KW - Silicate melt

KW - Stromboli

KW - Viscosity

UR - http://www.scopus.com/inward/record.url?scp=61349186314&partnerID=8YFLogxK

U2 - 10.1016/j.chemgeo.2008.12.023

DO - 10.1016/j.chemgeo.2008.12.023

M3 - Article

AN - SCOPUS:61349186314

VL - 260

SP - 278

EP - 285

JO - Chemical geology

JF - Chemical geology

SN - 0009-2541

IS - 3-4

ER -