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SUMMARY:Pressure-induced coordination change of Ge<sup>4+</sup> and Ga<sup
 >3+</sup> in silicate melts
DTSTART;VALUE=DATE-TIME:20141120T223000Z
DTEND;VALUE=DATE-TIME:20141120T224000Z
DTSTAMP;VALUE=DATE-TIME:20260809T071548Z
UID:indico-contribution-636@events01.synchrotron.org.au
DESCRIPTION:Speakers: Eleanor Mare (Australian National University)\nIn ge
 ochemical systems\, the relative stability of a given element in one phase
  or another is known as its partitioning behaviour\, and many models of Ea
 rth processes are based on the changes in partitioning with pressure (and/
 or other intensive variables). Since higher pressures favour smaller volum
 es\, changes in partitioning with pressure can be predicted if the pressur
 e-dependence of the volume of each phase in the system is known. Volumes o
 f mineral phases can be measured at high pressure\, but partial molar volu
 mes of melt components can only be measured at 1 atm. The partial molar vo
 lume of a melt component may change with pressure because of the mechanism
 s of melt compression\, such as coordination changes. Si4+ and Al3+\, majo
 r cations in natural melts\, are tetrahedrally coordinated by oxygen at am
 bient pressure but convert to octahedral coordination at higher pressure. 
 Similar coordination changes may occur for trace cations\, yet few have be
 en studied. In this work\, x-ray absorption near edge structure (XANES) sp
 ectroscopy was used to show a partial coordination change beginning at ~3-
 4 GPa for trace Ge4+ and Ga3+ in synthetic silicate glasses\, quenched fro
 m high-pressure melts. Such coordination changes will affect the partition
 ing behaviour of Ge and Ga between silicate melt and other minerals\, and 
 thus have implications for geochemical models such as the depth of formati
 on of erupted magmas and the formation of the Earth’s core.\n\nhttps://e
 vents01.synchrotron.org.au/event/3/contributions/636/
LOCATION: Oliphant Auditorium
URL:https://events01.synchrotron.org.au/event/3/contributions/636/
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