[meteorite-list] Portales Valley
From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:31 2004
Rhett Bourland wrote:
> My 8 cents
Hello Rhett and List,
Those 8 cents are well spent :-)
> I also know there are large sections of iron in this chondrite that are
> unlike any other meteorite out there. These large sections of irons will
> display a Widmanstatten like most iron meteorites when etched. To be able
> to form the necessary bands in the pattern would require that this meteorite
> was formed deep within the asteroid so that there would be plenty of
> insulation (in the form of rock) to keep the heat in the inside of the
> asteroid so that the kamacite and taenite would have the needed time
> to grow large enough to show up when etched.
> Early in the H parent body's history a pretty good sized impact happens
> on the H parent body. Its powerful enough to disrupt the asteroid to its
> center but not necessarily powerful enough to break up the asteroid.
> When it does this, some of the free metal in this region pools together
> to form the large metal veins.
KRING D.A., HILL D.H., GLEASON J.D., BRITT D.T. et al. (1999)
Portales Valley: A meteoritic sample of the brecciated and metal-veined
floor of an impact crater on an H-chondrite asteroid (MAPS 34-4, 1999,
Summary of the authors' conclusions:
01) Portales Valley has unusually large veins of metal and pockets of
metal produced by intersecting veins.
02) Provenance of these veins:
a) produced by an impact event on the original H-chondrite parent body,
b) a large asteroid produced from the fragmentation of that parent body.
03) Cooling rate about a few to perhaps tens of degrees per million
years for the products of that shock metamorphism.
04) The meteorite was deep within the H-chondrite body at the time of
the large impact event.
05) The crater diameter was >= 20 km in diameter (about 10% of the
original H-chondrite parent body).
06) The impact event probably occurred about 4.4 or 4.5 Ga, soon after
accretion from the solar nebula.
Received on Wed 05 Jun 2002 05:17:34 PM PDT