 |
| Titel |
Crystallographic preferred orientations and deformation mechanisms in mantle shear zones |
| VerfasserIn |
Martyn Drury, Gill Pennock, Laurie Palasse, Hans Ave Lallemant, Reinoud Vissers |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081992
|
|
|
|
|
|
| Zusammenfassung |
| In this contribution we will review our research on deformation mechanisms and olivine crystallographic preferred orientation (CPO) development in naturally deformed peridotites from mantle shear zones. In naturally deformed exhumed upper mantle rocks a strong olivine crystallographic preferred orientation (CPO) is generally developed in coarse grained rocks. Fine grained peridotites (grain size less than 15 microns) tend to have random to weak olivine CPO and this weak CPO is usually interpreted in terms of dominant grain size sensitive deformation mechanisms. Recently examples have been found of modest CPO development in pyroxene rich olivine rocks with ultra-fine grain size and microstructures consistent with dominant grain boundary sliding and diffusion creep. Several mechanisms can explain CPO development and preservation during grain size sensitive creep, indicating that the magnitude of seismic anisotropy in mantle shear zones may not be simply related to deformation mechanisms. The studies on mantle rocks indicate that grain size sensitive creep is often important in exhumed mantle shear zones, although, in many cases deformation involves a combination of dislocation creep and grain size sensitive mechanisms. We will discuss the significance of observations made on exhumed mantle rocks to shear zones in the lithosphere and asthenosphere. |
|
|
|
|
|
|