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Re: Phil: Meteor May Not Have Destroyed Dinosaurs Afterall?
"E.P. Grondine" schrieb:
> I seem to remember a post last year about the composition
> of the K-T impactor, but don't remember the nickle content.
Sky & Telescope, March 1999, p. 22: Piece of a Killer Asteroid ?
"While the mineralogy of the fossil meteorite has undoubtedly changed
over time, K y t e reports that the amounts of iron, chromium, and
iridium are nevertheless close to the ranges seen in carbonaceous
chondrites, ..."
BOND P. (1999) Fossilized remnant of dinosaur killer found (Astronomy
Now, 1999, Jan, p. 9):
"His [= Kyte] findings suggest that the meteorite’s composition
resembles a metal- and sulphide-rich carbonaceous chondrite asteroid,
..."
SHUKOLYUKOV A. et al. (1998) Chromium in the K-T boundary layer: First
isotopic evidence for an impactor and its type - carbonaceous material
(Meteoritics 33-4, 1998, A144):
"... we have measured the isotopic composition of Cr in bulk samples
of Allende and Orgueil. Treated in the same way as the K/T samples,
preliminary data for Allende and Orgueil show that their Cr-isotopic
signature is very similar to that of the K/T samples. Thus, regardless
of what the "negative" 53Cr/52Cr ratio actually will translate into...,
the obtained results strongly suggest that the K/T boundary impactor
was comprised of carbonaceous-chondrite-type material."
As for nickel content, I found in the bulk analysis data:
0.29% Ni for Camel Donga 003, a CK3 carbonaceous chondrite.
0,30% Ni for Watson 002, another CK3 carbonaceous chondrite.
On Mon, 19 Apr 1999, Jeff wrote to the Meteorite Central "gang":
"In fact, Allende has almost no metal, if what you mean is metallic
Fe-Ni. Jarosewich (1990) measured ~0.5 wt% metallic iron plus nickel in
Allende. Most of the metal in these oxidized CV3
chondrites is the high-Ni alloy awaruite. There was once low-Ni metal
(kamacite), but late stage oxidation has destroyed it all. There is a
big debate going on as to whether this sort of process happened during
parent body aqueous alteration or earlier, in the solar nebula."
Best regards,
Bernd
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