AbstractCharacterization of the alteration present at the Brent impact structure, revealed at least the presence of a chloritization, Au-depletion and K-enrichment process in the melt-fragment breccias. While this totally scattered the mobile Ni, Co and Cr, the immobile PGE are not affected. Also the melt lens shows alteration, albeit to a lesser degree. Ni, Co and Cr still have a strong correlation here. The use of the Os isotope system delivered a meteorite contribution up to 1 a 2 wt.% for the deepest melt lens sample. Together with the moderately and siderophile elements, it rejects the possibility of a fractionation during post-impact cooling, as suggested by Evans et al. , and implicates an impact identification.
We also reject the assumption of Grieve  and Palme et al.  that no (ultra)mafic components are present. However, if present, they can only be responsible for (a part of) the Ni, Co and Cr scatter in the melt-fragment breccias. The melt lens is for certain not affected. A more regional target rock study should be conducted to examine the possibility of (ultra)mafic components and their effect on the melt-fragment breccias.
|Date of Award||2011|
|Supervisor||Philippe Claeys (Promotor)|
- Brent crater