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SUMMARY:Chemical equilibrium in the Earth's core - Prof. Dario Alfè\, Uni
 versity College London
DTSTART:20200227T141500Z
DTEND:20200227T151500Z
UID:TALK134305@talks.cam.ac.uk
CONTACT:Bartomeu Monserrat
DESCRIPTION:The core of the Earth is a source of thermal energy for the ma
 ntle\, helping to drive convection\, plate tectonics and volcanism. It is 
 mainly formed by iron\, but it also contains light impurities. The exact c
 hemical inventory of the core is unknown\, but it is believed that oxygen 
 may be present in relatively large quantities\, as it is a major element i
 n the mantle. Freezing of the inner core causes oxygen to be released in t
 he liquid\, which is thought to be the main form of energy driving core co
 nvection at the present day\, responsible for the generation of the Earth'
 s magnetic field. One of the fundamental questions is therefore how oxygen
  entered the core in the first place.\n\nUsing first principles calculatio
 ns of chemical potentials we put constraints on the equilibrium concentrat
 ions of oxygen between liquid iron and a liquid silicate mixture\, represe
 ntative of long lived magma ocean (MO) at the base of the mantle. We show 
 that the presence of a large fraction of oxygen in the core can be explain
 ed by a relatively large thermodynamic advantage of partitioning from the 
 MO into the liquid core. We also computed chemical potentials in solid fer
 ropericlase\, thought to be one of the main constituents of the Earth's ma
 ntle\, and found that the current oxygen concentration in the core is lowe
 r than its equilibrium concentration\, suggesting that the mantle may be c
 ontinually pumping oxygen into the core\, even at the present day. This ha
 s important consequences for our understanding of convection in the core\,
  supporting the idea of the presence of a stratified\, oxygen rich\, layer
  at the top of the core\, which may have been observed in the seismologica
 l record.\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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