HR: 08:00h
AN: V41B-01    [Abstracts]
TI: Viscosity of Magmatic liquids: a model.
AU: Giordano, D
EM:
AF: Dipartimento di Scienze Geologiche , Università degli Studi di Roma Tre L.go S. Leonardo Murialdo, 1 - Roma , Rome, 00146, Italy
AU: Russell, J K
EM:
AF: Earth & Ocean Sciences , University of British Columbia 6339 Stores Road , Vancouver, V6T 1Z4, Canada
AU: * Dingwell, D B
EM: Dingwell@lmu.de
AF: Earth and Environment Earth and Environment, University of Munich Theresienstr. 41/III, Munich, 80333, Germany
AB: Here we present a multicomponent chemical model for predicting the viscosity of naturally-occurring, volatile- bearing silicate melts based on ~1542 experimental measurements of viscosity at T(K) on melts of known composition. Much, but not all, of this data stems from the work of our own laboratories in the past 20 years. The model incorporates 10 major and minor oxide components and the volatile components that are known to have a major influence at geological concentrations on the viscosity of melts; H2O and F. We use the oxide mole % as a chemical basis. We treat all iron as FeOTot. There is clear evidence that, in detail, that Fe2O3 and FeO play distinct roles in governing melt structure and that the redox state of very Fe-rich melts does measurably influence viscosity. Our redox simplification here is purely empirical, resulting from the fact that tests for model improvement, based on a redox factor, fail to produce an improvement of the fit. Fluorine is treated as mole % F2O-1. The model has the following attributes: i) its experimental basis spans virtually the entire compositional range found in naturally-occurring volcanic rocks, ii) the chemical model captures the effects of 10 major and minor oxide components and the volatile components H2O and F, iii) it is computationally continuous across the entire compositional and temperature spectrum of the database, iv) it is capable of accommodating both strong (near-Arrhenian T-dependence) and fragile (very non-Arrhenian T-dependence) behaviour of silicate melts, and v) it reproduces all empirically observed relationships between melt composition and transport properties such as glass transition temperature (Tg) and fragility (m). The model uses a total of 18 empirical coefficients.
DE: 8425 Effusive volcanism
DE: 8428 Explosive volcanism
DE: 8429 Lava rheology and morphology
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly