Testing the use of Tungsten isotopes as impact markers

Samenvatting

The Late Heavy Bombardment (LHB) at 3.9 Ga affected the whole inner solar system. Traces of this cataclysmic surge of impacts are found in the Moon cratering record and the shock-melt ages of meteorites derived from the asteroid belt or Mars. On Earth, despite the age coincidence between the LHB and the oldest surviving rock sequences (Acasta, Isua), no traces, - such as Ir anomaly, shock mineral concentration or Cr isotopic-signature - of this event are known. In 2002, Schoenberg et al. reported possible W isotope (182Hf-182W half life ~ 9 Ma) heterogeneities from Early Archean sequences in West Greenland and Northern Labrador, which they attributed to a meteoritic contribution delivered during the LHB. According to their data, the 182W/183W ratios digresse from terrestrial values and show an almost meteoritic ?W (Fig. 1 in Schoenberg et al.). If these results are correct, they not only represent the only known traces of the LHB, but also document that it coincided with the most ancient terrestrial sequences. This hypothesis requires confirmation

Datum prijs	2010
Originele taal	English
Begeleider	Philippe Claeys (Promotor)