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| Titel |
The Influence of Cooling Rates on Paleointensity of Volcanic Glasses: an Experimental Approach on Synthetic Glass |
| VerfasserIn |
F. W. von Aulock, A. Ferk, R. Leonhardt, K.-U. Hess, D. B. Dingwell |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030134
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| Zusammenfassung |
| The suitability of volcanic glass for paleointensity determinations has been proposed in many
studies throughout the last years. Besides the mainly single domain magnetic remanence
carriers and the pristine character of the volcanic glass, this was also reasoned by the
possibility to correct paleointensity data for cooling rate dependency using relaxation
geospeedometry. This method gives the cooling rate of a glass at the glass transition interval
which marks the change of a ductile supercooled liquid to a brittle glass. In this study the
cooling rate correction as carried out for example by Leonhardt et al. 2006 is tested on
synthetic volcanic glass. In order to obtain a stable multicomponent glass with
ideal magnetic properties, a natural phonolithic glass from Tenerife (Spain) was
melted to avoid heterogeneity and degassing. Further it was tempered for 5 hours at
900Â -C to yield a sufficient concentration of magnetic remanence carriers. To exclude
nucleation or crystallisation 7 samples were then heated to about 50Â -C above the glass
transition temperature at around 720Â -C and quenched at different rates from 0.1 to
15Â K/min. After carrying out a paleointensity experiment using a modified Thellier
method, which incorporated alteration, additivity and tail checks, the dependence of
the thermoremance on cooling rate was investigated. Using the original cooling
rates we corrected the data and obtained paleointensities of around 46 μT, which
is a good approximation of the ambient field of 48 μT. Taking into account that
the uncorrected mean paleointensity is about 57 μT, this suggests that cooling
rate correction is not only working, but also a necessary tool to yield the true field
value.
R. Leonhardt , J. Matzka, A.R.L. Nichols , D.B. Dingwell Cooling rate correction of
paleointensity determination for volcanic glasses by relaxation geospeedometry; Earth and
Planetary Science Letters 243 (2006) 282–292 |
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