[meteorite-list] Tambo Quemado

From: Jeff Kuyken <jeff_at_meteoritecentral.com>
Date: Sat Aug 21 05:04:05 2004
Message-ID: <006801c4875d$cbf6e480$04348690_at_mandin4f89ypwu>

G'day Bernd & List,

I've made a quick page up and the images can be seen at:

http://www.meteoritesaustralia.com/space/tambo.html

I highly recommend checking them out as this inclusion is pretty amazing.
Might be time to go and have a closer look at your Tambo folks!

Cheers,

Jeff Kuyken
I.M.C.A. #3085
www.meteorites.com.au

  ----- Original Message -----
  From: bernd.pauli_at_paulinet.de
  To: Meteorite-list_at_meteoritecentral.com
  Sent: Friday, August 20, 2004 11:41 PM
  Subject: [meteorite-list] Tambo Quemado


  Hello List,

  One if the irons that have always been high on my wish list, apart
  from Cape York, is Tambo Quemado, a member of the IIIAB irons
  that must have been artificially reheated to about 1000?C at some
  point of its history and the result: fused schreibersite crystals
  and transformed kamacite grains are clearly visible under a microscope.

  Eric Twelker has a batch of beautiful Tambos and so I was finally able to
  acquire a museum-quality 80.6-gram slice from him. My slice (that I am so
  very proud of and so happy to own) can be seen at:

  http://www.meteoritemarket.com/TAM.htm

  The troilite nodule has a whopping diameter of 17 millimeters, has
  a mottled appearance and is surrounded by a seam of schreibersite.

  It's an incredibly beautiful iron - see Martin Horejsi's and Marlin Cilz's
  article in the Meteorite Magazine, May 1998, Volume 4, No. 2, p. 13 or go
  to BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Vol. 3, pp.
1174-1177.

  When I closely inspected the troilite nodule under my microscope at 16x
and at
  32x magnification, I was "dumbfounded" when I found something that should
not be
  there. I instantly took some pics with my digital camera but will have to
ask
  Jeff Kuyken if he can upload them for me on his website for everyone to
muse about.

  It is a "stony", maybe a silicate-related inclusion at the upper edge of
the troilite
  nodule. Wondering what I was looking at, I searched for information both
in O. Richard
  Norton's Encyclopedia, in Buchwald, and in McSween. On page 205 of
"Meteorites and Their
  Parent Planets", Mc Sween says that "silicates in IIIAB irons are similar
in composition
  to HED chondrites".

  Now, my inclusion doesn't look like it could be of HED origin. Visually,
it looks more
  like the Cumberland aubrite texture - a very improbable, unlikely
provenance though.

  Vagn Buchwald says that silicate inclusions in IIIAB irons are extremely
rare and
  in Appendix I, pp. 152-153, he mentions only 2 irons that may be
silicate-bearing:
  Avoca (olivine?) and Grant (tridymite, glass or silicates?)

  In "Astronomy Now" for October 1996, p. 4, I found this:

  Silicate inclusion is meteorite mystery

  Type IIIA and IIIB iron meteorites are thought to have formed in the cores
of asteroids.
  They often contain small inclusions of chromite and one or more
iron-bearing phosphate
  minerals which probably formed in the late stages of core crystallisation.
The recent
  discovery by American scientists of a silicate inclusion in a type IIIA
meteorite Puente
  del Zacate is much harder to explain. According to the authors of the
report in Science,
  "How a graphite-bearing silicate inclusion was introduced into a
low-carbon IIIA iron core
  is difficult to envision." One possible answer is that the inclusion
originated in the lower
  mantle of the asteroid close to its iron core. Another possibility is that
some small masses
  of iron formed and cooled inside the silicate-rich mantle (by Peter Bond).

  See also:

  OLSEN E.J. et al. (1996) A silicate inclusion in Puente del
  Zacate, a IIIA iron meteorite (Science 273, 1365-1367).


****************************************************************************
***************

  Puzzling questions:

  Does my Tambo Quemado slice harbor such a graphite-bearing
  silicate inclusion which would make it no. 3 among the IIIAB irons?

  Is it something glassy, quartz/tridymite-related?

  Is it a stony component from the lower mantle-core interface?

  Is it preterrestrial or (unlikely) terrestrial?

  Is it something chondritic or achondritic?

  How, after all, did it get there ???


****************************************************************************
***************

  Parameters of my digital pics:

  Tambo Quemado, IIIABx16-01a
  Magnification: 16x
  Exposure: 1/20
  Eyepiece projection
  Aperture: 6.7

  Tambo Quemado, IIIABx32-01b
  Magnification: 32x
  Exposure: 1/25
  Eyepiece projection
  Aperture: 3.5

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Received on Sat 21 Aug 2004 05:03:58 AM PDT