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| Titel |
Influence of Hydrothermally Generated Talc Upon Fault Behaviour |
| VerfasserIn |
Amy Clare Ellis, Ernest Rutter, Katharine Brodie, Julian Mecklenburgh |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046025
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| Zusammenfassung |
| Research indicates that reactions generating phyllosilicate minerals, including talc, may be
significant in tectonically active settings such as oceanic spreading centres and large crustal
fault zones. The interaction of the growth of frictionally weak hydrothermal minerals with
progressive displacement on fault zones represents one possible explanation for anomalous
weakness observed at low angle normal (oceanic detachment) faults and the San Andreas
Fault. We performed experiments to examine the effect of the hydrothermal production of
talc upon fault behaviour. Three types of experiment have been conducted in a
triaxial apparatus, at varied effective pressure and temperatures from 20-450Ë C.
Initial experiments involve introduction of a powdered talc gouge between sawcut
blocks of lizardite and quartzite. Later tests involve the growth of talc during the
experiment by forced reaction of the sawcut blocks at their interface according
to: lizardite + quartz - talc + H2O, followed by either constant displacement
rate deformation (“cook and kick”) corresponding to an approximate shear strain
rate of 1.5x10-3Â s-1, or constant stress deformation (“cook and creep”) spanning
shear strain rates to 1.0x10-9Â s-1. Kinetic behaviour of this reaction has been
previously explored as part of this study. Stress relaxation data is also used to investigate
flow behaviour at very low strain rates. The friction coefficients determined for
lizardite and talc are in agreement with previously published values. Results do
not indicate a correlation between the thickness of the talc layer present and the
frictional weakening of the shear zone-a small amount appears sufficient to lower the
friction coefficient in constant displacement rate experiments. Microstructural study
to elucidate deformation mechanisms is ongoing and is significant for the creep
experiments in order to relate the generation of talc via reaction to the shear strain
rate. These findings are expected to be significant in the description of fault zone
weakening mechanisms, including incongruent pressure solution and reaction softening. |
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