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SUMMARY:Copper isotopes and the role of sulfides during Earth’s differen
 tiation - Paul Savage\, Institut de Physique du Globe de Paris
DTSTART:20141014T150000Z
DTEND:20141014T160000Z
UID:TALK54762@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:The differentiation of Earth into a metallic core and silicate
  mantle has left its signature on the chemical and isotopic composition of
  the bulk silicate Earth (BSE). This is seen in the depletion of siderophi
 le (metal-loving) relative to lithophile (rock-loving) elements in Earth
 ’s mantle as well as\, for instance\, the silicon (Si) isotope offset be
 tween primitive meteorites (a good proxy for the composition of bulk Earth
 ) and BSE\, which further implies that Si is present in Earth’s core.\nA
 nother putative light element in Earth’s core is sulfur\; however\, esti
 mates of core S abundance vary significantly and\, due to its volatile nat
 ure\, no unequivocal S isotopic signature for core fractionation has thus 
 far been detected. I present new high precision isotopic data for Cu\, a s
 iderophile and chalcophile (sulfur-loving) element\, which shows that Eart
 h’s mantle is isotopically fractionated relative to bulk Earth. Critical
 ly\, high-pressure metal-sulfide-silicate equilibration experiments sugges
 t that the sense of Cu isotopic fractionation between BSE and bulk Earth r
 equires that a sulfide-rich liquid segregated from Earth’s mantle during
  differentiation\, which most likely entered the core.\n\nReferences:\n1) 
 Palme\, H and O'Neill H. St.C. (2014) Cosmochemical estimates of mantle co
 mposition\, Treatise on Geochemistry (Second Edition)\, Volume 3\, pp.1-39
  (a brilliant review of the composition of the Earth's mantle\, and how we
  think it got that way)\n\n2) Badro\, J.\, Cote\, A.S. & Brodholt\, J.P. (
 2014) A seismologically consistent compositional model of Earth’s core. 
 Proc. Nat. Acad. Sci.\, 111\, pp.7542-7545 (some interesting ideas of how 
 to constrain the light element budget in the core - also\, well referenced
  if you want to read further)\n\n3) Wood\, B. J. and Halliday A. N.  (2010
 ) The lead isotopic age of the Earth can be explained by core formation al
 one. Nature. 465\, pp.767-770 (info about the Pb isotope composition of th
 e mantle - and how core formation could explain it)\n\n4) O'Neill H. St.C.
  (1991) The origin of the moon and the early history of the earth-A chemic
 al model. Part 2: The earth. Geochim. Cosmochim. Acta. 55\, pp.1159-1172. 
 (optional - an oldie but a goodie - my inspiration for the sulphide matte 
 model) \n
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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