Viscosity changes during the crystallization of a shoshonitic lava from the Vulcanello peninsula (Aeolian Islands, southern Tyrrhenian Sea, Italy) were measured by use of a electromagnetic rotational viscometer under Ni-NiO buffered conditions at temperatures ranging from 1539 K to 1381 K. Results showed an increase in effective viscosity from 131 Pa s to 15320 Pa s as the crystal content increased from 0 vol% to similar to 14 vol%. The crystallization processes in the nominally dry shoshonite began at 1420 K with the formation of clinopyroxene, which was followed by the formation of plagioclase and olivine at 1401 K. Experimental observations differed from predictions derived from the use of the Einstein-Roscoe equation with the Marsh (E-R-M) parameter at crystal contents higher than 8 vol%. The relative viscosity of samples was larger than that calculated by E-R-M by a factor of up to 9.5 as the temperature decreased to 1381 K. The large departure of the experimental results from the E-R-M equation predictions was likely caused by the interaction of elongated pyroxene crystals. The measured viscosity data were used to estimate the potential for emplacement of shoshonitic lavas.

Viscosity changes during crystallization of a shoshonitic magma: new insights on a lava flow emplacement

DE ROSA, Rosanna;DONATO, Paola
2013

Abstract

Viscosity changes during the crystallization of a shoshonitic lava from the Vulcanello peninsula (Aeolian Islands, southern Tyrrhenian Sea, Italy) were measured by use of a electromagnetic rotational viscometer under Ni-NiO buffered conditions at temperatures ranging from 1539 K to 1381 K. Results showed an increase in effective viscosity from 131 Pa s to 15320 Pa s as the crystal content increased from 0 vol% to similar to 14 vol%. The crystallization processes in the nominally dry shoshonite began at 1420 K with the formation of clinopyroxene, which was followed by the formation of plagioclase and olivine at 1401 K. Experimental observations differed from predictions derived from the use of the Einstein-Roscoe equation with the Marsh (E-R-M) parameter at crystal contents higher than 8 vol%. The relative viscosity of samples was larger than that calculated by E-R-M by a factor of up to 9.5 as the temperature decreased to 1381 K. The large departure of the experimental results from the E-R-M equation predictions was likely caused by the interaction of elongated pyroxene crystals. The measured viscosity data were used to estimate the potential for emplacement of shoshonitic lavas.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11770/140407
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