HR: 1340h
AN: V53C-1581    [Abstracts]
TI: Thermal Calibration of a High-Load, High-Temperature Uni-axial Press for Volcanological Studies
AU: * Cordonnier, B
EM: cordonnier@min.uni-muenchen.de
AF: LMU, Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AU: Hess, K
EM: hess@lmu.de
AF: LMU, Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AU: Lavallee, Y
EM: yanlavallee@hotmail.com
AF: LMU, Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AU: Dingwell, D B
EM: dingwell@lmu.de
AF: LMU, Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AB: The need for an adequate understanding of the nature and extent of physico-chemical processes involved in explosive volcanism is considerable. In recent years much effort has been concentrated on rhyolitic melts under conditions relevant to explosive volcanism. Especially the description of single phase rhyolitic melt properties such as temperature, pressure, and compositional dependence of viscosity has been greatly improved. Yet, modelling of the emplacement and eruption of silicic domes is still hampered by the lack of a sufficiently accurate rheological database for multi-phase lavas with crystals and vesicles. We have developed a unique high-load, high-temperature deformation apparatus for studying in situ the non-Newtonian flow behaviour of magmas. The apparatus accommodates samples that are up to 100 mm in diameter and 100 mm long, and can be used to run constant displacement rate and constant load experiments. The rig is ideal for volcanological studies because it uses experimental conditions that closely match those found in volcanic processes: stress (0 to > 500 MPa), strain rates (10E-6 to 10E-2 s), total strain (0 to 100%) and temperature (25 to 1300 °C).
Viscosity is strongly temperature dependent. Therefore temperature gradients must be adjusted to minimum. This is accomplished by an improved thermal insulation and improved localisation inside the hot zone of the furnace. Following these modifications the temperature gradient has been reduced to 3 K for a 4 cm high and 10 cm wide cylindrical volume. After deformation the samples exhibit barrel shape, indicating homogeneous deformation under no-slip conditions. This allows us to test the rheological behaviour of Unzen magma. Several deformation experiments have been performed on various natural samples (variation of crystal fraction, porosity, etc .) and the transition from Newtonian to Non-Newtonian flow behaviour has been observed.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8428 Explosive volcanism
DE: 8429 Lava rheology and morphology
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005