[meteorite-list] Portales Valley

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:31 2004
Message-ID: <3CFE7FEE.BF03AD65_at_lehrer1.rz.uni-karlsruhe.de>

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.

Best regards,

Received on Wed 05 Jun 2002 05:17:34 PM PDT

Help support this free mailing list:

Yahoo MyWeb