 |
| Titel |
Relative strength of the pyrope-majorite solid solution and the flow-law of majorite containing garnets. |
| VerfasserIn |
Simon Hunt, David Dobson, Li Li, Don Weidner, John Brodholt |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042450
|
|
|
|
|
|
| Zusammenfassung |
| Even though the garnet phase is the second most abundant phase in the upper-mantle and
transition-zone, no previous studies have directly measured the effect of majorite content on
the strength of garnet under mantle conditions. Here we report the results of constant
strain-rate and stress-relaxation experiments on garnets in the pyrope–majorite solid solution
which constrain the strength of majoritic containing garnets relative to pyrope as a function of
majorite content and temperature. We find that at temperatures below 650-C both pure
pyrope and majoritic garnets have the same strength. Conversely, above 650-C we
find that majoritic garnets are initially stronger than pure pyrope but weaken with
increasing temperature and majorite content and with significant majorite contents are
weaker than pyrope above approximately 800 -C. We develop a flow law for the
entire pyrope–majorite solid solution as a function of temperature and majorite
content.
From our experimental results it is necessary that majorite is the weak phase in the
transition-zone. Furthermore, the relative-weakness of majorite garnet, which dominates the
mineralogy of the subducted MORB layer at transition-zone depths, further promotes
thermal run-away processes as the causal mechanism for deep-focus Earthquakes. |
|
|
|
|
|
|