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SUMMARY:Reconciling macroscopic olivine grain growth with the microscopic 
 physical properties of the intergranular medium - Leila Hashim (Universit
 é d'Orléans)
DTSTART:20160412T150000Z
DTEND:20160412T160000Z
UID:TALK65417@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Co-authors: Gard&eacute\;s Emmanuel (CNRS - Universit&eacute\;
  Caen)\, Sifr&eacute\; David (CNRS - Universit&eacute\; d&#39\;Orl&eacute\
 ;ans)\, Morales Luiz F.G. (GFZ Potsdam)\, Pr&eacute\;cigout Jacques (CNRS 
 - Universit&eacute\; d&#39\;Orl&eacute\;ans)\, Gaillard Fabrice (CNRS - Un
 iversit&eacute\; d&#39\;Orl&eacute\;ans)<span><br><br>Grain size is a crit
 ical parameter for the understanding of our planet&rsquo\;s mantle since i
 t has considerable impact on seismological properties\, on the permeabilit
 y of mantle rocks and therefore on melt migration characteristics of Earth
 &rsquo\;s interior. Grain growth therefore becomes an important process th
 at should be meticulously determined in order to better understand the dyn
 amics of our planet&rsquo\;s interior.<br><br>Olivine grain growth has the
 refore been experimentally determined by a wide number of grain growth stu
 dies where different effects have been considered (water\, fO2\, melt\, se
 condary phases). However\, no clear consensus on the values of the differe
 nt material-dependent parameters in the empirical law has been reached. To
  increase the existing database on olivine grain growth\, we experimentall
 y investigated the effect of melt (from nominally melt-free to 12 wt.% mel
 t) and water on San Carlos olivine under different pressure-temperature-du
 ration conditions (0.3 GPa < P < 3.0 GPa\, 1200&deg\;C < T < 1350&deg\;C\,
  1h < t < 360h).<br><span><br>By combining the existing database on olivin
 e grain growth and our experimental data\, we have succeeded in modeling (
 i) genuinely dry olivine grain growth aggregates\, through grain boundary 
 diffusion-controlled processes\, (ii) H2O-oversaturated olivine aggregates
  and (iii) melt-bearing olivine aggregates\, from nominally melt-free to &
 sim\; 50 wt.% melt. Different important parameters have been constrained b
 y using our model\, namely the dry effective grain boundary thickness (&de
 lta\; &sim\; 6 nm)\, melt contents in nominally melt-free samples (&Phi\; 
 &le\; 0.5 wt.%) as well as the wetting properties (&Psi\;) of melt as a fu
 nction of melt content\, pressure and temperature. We expect that our resu
 lts will not only have considerable implications on the grain size-depende
 nt deformation mechanisms of mantle rocks but also reconcile macroscopic o
 bservations to microscopic-scale key processes governing the mantle behavi
 or\, particularly in intergranular zones impregnated by low melt content s
 .</span></span>
LOCATION:Seminar Room 1\, Newton Institute
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