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SUMMARY:Pressure-dependent changes in Zr coordination in silicate liquid: 
 in vs. ex situ measurements
DTSTART;VALUE=DATE-TIME:20211124T055000Z
DTEND;VALUE=DATE-TIME:20211124T060500Z
DTSTAMP;VALUE=DATE-TIME:20260814T132822Z
UID:indico-contribution-4301@events01.synchrotron.org.au
DESCRIPTION:Speakers: Nicholas Farmer (Macquarie University)\nChanges in t
 he coordination of elements in silicate melts as a function of pressure im
 pact their geochemical behaviour and are key to understanding processes su
 ch as planetary differentiation. Questions persist as to the extent to whi
 ch the coordination environment of elements in silicate melts at high pres
 sure and temperature can be preserved in glasses recovered to ambient cond
 itions.\n\nThe only method to unambiguously measure the coordination envir
 onment of trace elements in a silicate liquid at high pressure is via *in 
 situ* measurements such as x-ray absorption spectroscopy\, preferably in l
 arge volume apparatus that can simulate the environment of the upper mantl
 e such as the Macquarie D-DIA apparatus. These measurements are difficult 
 and only possible at a handful of facilities worldwide\, so most experimen
 tal data are derived from *ex situ* measurements of recovered glasses.\n\n
 We made Zr K-edge XANES measurements *in situ* at conditions simulating th
 e mantle\, showing a pressure-dependent change consistent with an earlier 
 *ex situ* study on samples recovered from piston-cylinder experiments in w
 hich glasses were annealed close to their glass transition temperature (Bu
 rnham et al. 2019). We plan further XAS experiments measuring samples reco
 vered from our *in situ* experiments to determine the differences between 
 quenched glasses\, annealed glasses\, and *in situ* measurements.\n\nWe pr
 opose that changes in Zr XANES correspond to an increase in the coordinati
 on number of Zr with pressure. This could explain previously observed chan
 ges in Zr solubility at high pressure not predicted by current models\, an
 d changes in Zr olivine/melt partition coefficients at mantle pressures.\n
 \nhttps://events01.synchrotron.org.au/event/146/contributions/4301/
LOCATION:Online
URL:https://events01.synchrotron.org.au/event/146/contributions/4301/
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