Silicate melts are the ubiquitous components of igneous processes in the Earth's crust and mantle and serve as the key transport agents for physico-chemical differentiation and evolution of the Earth. The viscosity is a fundamental property that influences the dynamic behaviour of silicate melts (melt segregation, magma mixing, crystal fractionation, fluid exsolution, the ascent rate of a magma). This study presents a new and straightforward method for estimating the viscosity and water content in hydrous silicate melts using homogenization measurements on melt inclusions in rock-forming minerals in granites and rhyolites from the Erzgebirge, the Slavkovsky les, Thuringia, the Caucasus, the Fichtelgebirge, and the Oberpfalz. A combination of the Stokes-Einstein equation and Shaw's (1972) viscosity calculation, along with data on temperature, inclusion diameter, run time, and inclusion chemistry, was employed. The viscosity at the minimum observable homogenization temperature is 3.6 * 104 Pa . s Generally, the water content ranges from 2.5 to 9 wt. %. The accuracy of the method and the potential for diffusive water loss are critically assessed.
The relationship between diffusion and viscosity, as described by
the classic Stokes-Einstein relation, and the direct connection with viscosity
(e.g., Shaw 1963) combine all-important physical quantities: temperature, time,
length, and chemistry.
Author(s)
Details
Rainer
Thomas
Home Office Raman Laboratory, Im Waldwinkel 8, D-14662 Friesack,
Germany.
Please see the book here: https://doi.org/10.9734/bpi/nhstc/v2/5750
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