15. Late Veneer
• Material certainly added post core formation
• Need ~20:1 Earth:Moon accretion
• Can this amount of material be delivered
without being added to core?
16. Late Veneer vs High T core
• Internal or external source of precious
metals
• Sample Earth before Late Veneer?
17. The oldest part of the planet
Jack Hills,
Yilgarn Block, W. Australia
Wilde et al 01
24. Precious Metal Content of Earliest
Mantle?
• Need to see through melting, crystallisation and
metamorphism
• Hard to constrain moden mantle Platinum Group
Elements (PGE) contents even with samples of
mantle
• Need a robust proxy for PGE
• Isotopic tracer of terrestrial vs extra-terrestrial
PGE?
30. ε182W variability in modern mantle?
• Entrainment of core material into mantle via
plumes may lower ε182W
• High 186Os/188Os of Hawaiian plume attributed to
core component (Walker and Brandon)
• Outer core should have low ε182W ~-1.9 and
much W
38. Origin of Precious Metals
• Homogeneity of ε182W of modern mantle leaves no room
for precious metal deliver from core to mantle
• Contrast of 0.15 ε182W between modern and Isua rocks
entirely compatible with Late Veneer
• Current inventory of precious metals delivered to Earth by
meteorite bombardment post core formation
• 20x higher flux to Earth compared to Moon a lucky
chance of the random nature of accretion (Botke et al
2011)
Notas do Editor
Confusing 143 referenced to chur (chondrite) as assumed the same, for 142 clearly not the case and for covenience refed to Earth
Half life on 103Ma so the signature must have been imparted before formation at 3.8
Confusing 143 referenced to chur (chondrite) as assumed the same, for 142 clearly not the case and for covenience refed to Earth
Have checked strongest current plume, but is a tail. Worth checking out heads- most head on continents and very prone to contamination, however W. Pacific LIPs oceanic and mark major pulse of volcanism, strongly argued to be from lower mantle. Worth looking at other plumes. Notably deep root of hawaii still not especially clear, whereas as other less vigorous volcanoes aparently have (or did when we started)
Montelli 2004 banana doughnutCanaries and Azores w resolved, deep rooted origins- (Canaries ‘Robust merge with Canaries?) Cape Verde, clearest topographic and geoid anom (Montelli ‘deep’ plume merging with Canaries/Azores. NB Hawaii and Iceland not so defined
