[meteorite-list] RFS Picture of the Day => Brenham slice withunusual inclusion - part 2

From: bernd.pauli at paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: 22 Jan 2007 19:13:30 UT
Message-ID: <DIIE.000000C1000014F1_at_paulinet.de>

Tett wrote:

"Thank you for the research and the comprehensive
 answer. It is a pleasure learning from you!"
 
Thank you for these kind words!

Tett continues: "The swathing kamacite sounds like it might be the case here."

Last night I got a mail from a Canadian meteorite collector who wondered if
I had or knew of a probable classification for the Brenham slices now on the
Internet.

Difficult question. According to the current literature, it should be close
to the IIIAB irons and the MAPS article that David Weir references (Honda
et al., 2002) on his website, mentions this:

"The metallic fraction of this meteorite has also been identified as
Hopewell Mounds, a medium octahedrite, IIIA, with olivine inclusions"

..but: David's website and the on-line database of the Met.Society also clearly state
that this meteorite is anomalous in several respects - for example its anomalous metal
composition.

Maybe this anomalous metal composition is the answer to the following piece of
information I found regarding its phosphorus content. Yesterday I had written:

"one may conclude that Brenham has an appreciable amount (above ca. 0.4% P
- according to Buchwald) of phosphorus. Otherwise we wouldn't see those ...
long, needles of schreibersite with their seams of swathing kamacite."

.. and here is what I found in Kunz et al. 1890:

"The following analyses of the Kiowa meteorites were made by Mr. L.G. Eakins
in the laboratory of the United States Geological Survey: ... P = 0.14% ..."

Hmm, ... much too low but these Brezina lamellae are there (provided they are
what I think they are!). Two ways out here: Either Mr. L.G. Eakins's data are
outdated or imprecise or it's because of Brenham's anomalous metal composition.
Any thoughts from those who own these gorgeous slices? Mike Miller, Geoff Notkin,
Steve Arnold, and others?

References:

HONDA M. et al. (2002) Cosmogenic nuclides in the Brenham
pallasite (MAPS 37-12, 2002, pp. 1711-1728).

WASSON J.T.et al. (2002) Main-group pallasites: Relationship to
IIIAB irons, role of magmatic gases (MAPS 37-7, 2002, A147).

KUNZ G.F. (1890) On five new American Meteorites (The American
Journal of Science, Volume 140, 1890, Art. XLII, pp. 312-318).

To: tett at rogers.com
    Meteorite-list at meteoritecentral.com
Received on Mon 22 Jan 2007 02:13:30 PM PST