HR: 11:50h
AN: V52A-07    [Abstracts]
TI: Rheological properties of explosively erupted magmas at the Campi Flegrei caldera (Italy) through experimental studies.
AU: * Mangiacapra, A
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, D-80333 Germany
AU: * Mangiacapra, A
AF: Osservatorio Vesuviano, INGV-Naples, Naples, I-80124 Italy
AU: Dingwell, D B
EM: Dingwell@lmu.de
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, D-80333 Germany
AU: Orsi, G
AF: Osservatorio Vesuviano, INGV-Naples, Naples, I-80124 Italy
AU: DiMatteo, V
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, D-80333 Germany
AU: Nichols, A
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, D-80333 Germany
AU: Potuzak, M
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, D-80333 Germany
AB: In recent years, new methods to evaluate the rheological properties of silicate melts have been developed. Nevertheless, we are still far away from fully satisfactory modelling of complex eruptive processes due to lack of data on evolved magmas. The Campi Flegrei caldera (CFc), a restless nested structure in Southern Italy, is an ideal natural laboratory for this purpose. The erupted magmas have a broad spectrum of compositions, from trachybasalt to alkali trachyte. Analysing the deposits of the Campanian Ignimbrite, Neapolitan Yellow Tuff, Minopoli 2, Fondo Riccio, Agnano-Monte Spina and Astroni eruptions, we have completed the description of the temperature-dependent Newtonian viscosities for the dry compositional spectrum of the erupted magmas that was initiated by the Munich, Rome and Pisa groups. Viscosities were investigated at high (1323-1873 K) and low (889-1134 K) temperature using the concentric cylinder and the micropenetration techniques, respectively. In addition, complementary hydrous viscosity measurements have been performed on trachybasaltic and latitic compositions. We synthesised samples with different water content (0.5- 2wt%) using an internally heated pressure vessel at 200 MPa and 1473 K. Water content was checked using FTIR spectroscopy. For this the molar absorptivity has been calibrated for both compositions. Hydrous viscosity measurements using the micropenetration technique were performed between 883 and 893 K, depending on the glass transition temperature Tg of each sample. In order to evaluate the Tg we performed calorimetric measurements using differential scanning calorimetry. For each sample the cooling rate was unknown and the heating rate 10 K/min. Tg was defined as the onset of the glass transition. The obtained results provide the first rheological properties dataset for the whole CFc compositional range, helping to constrain the modelling of magma chamber processes and conduit dynamics.
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting