[meteorite-list] Franconia area chondrites and Irons

From: Ruben Garcia <meteoritemall_at_meteoritecentral.com>
Date: Sun Jul 25 20:33:41 2004
Message-ID: <20040726003339.17233.qmail_at_web20802.mail.yahoo.com>

Hi Bob and List,

Unfortunately I do not have the numbers in front of
me and therefore do not know the exact % Fa in the
olivine. Although I'm sure Lora Varley (who did the
microprobe work at the university) could tell you very
quickly.

The shock of each of the first eight meteorites was
not entirely consistent. Of the eight specimens
classified, five meteorites had a shock factor of 2
and three meteorites had a shock factor of 1.

The tiny irons we've found have not yet been seriously
considered as being related to the Dutch Flat Iron .
This is partly because a lot of time has NOT been
devoted to studying them. Also as I recall the Dutch
Flat iron is a coarse or coarsest octahedrie and
displays a wide Widmanstatten pattern. The one
Franconia iron I tried to etch seemed to have no
recognizable pattern at all, instead it was very
grainy. (Keep in mind the iron I attempted to etch did
have a high percentage of nickel, least anyone think
it was not a meteorite). However, When I etched a
Franconia chondrite with large metal veins a very
brilliant medium to fine widmanstatten pattern did
appear. What does all this mean? I don't know but more
help is on the way.

Rob Reisener and I have started working together on
this and hopefully Rob will have some answers soon.
He is a geochemist with a special interest in
meteorite metallurgy, and
has recently published several papers that relate
directly to this
problem:

1) Reisener R.J. and Goldstein J.I. (2003) Ordinary
chondrite
metallography: Part 1. Fe-Ni taenite cooling
experiments. Meteoritics and
Planetary Science 38, # 11, pp. 1669-1678.

2) Reisener R.J. and Goldstein J.I. (2003) Ordinary
chondrite
metallography: Part 2. Formation of zoned and unzoned
metal particles in
relatively unshocked H, L, and LL chondrites.
Meteoritics and Planetary
Science 38, # 11, pp. 1679-1696.

Rob says
"There are important differences between the metal in
iron meteorites and the metal in ordinary chondrites.
These differences are usually easy to detect when one
knows what to look for. Unfortunately, most meteorite
researchers have limited metallurgical training and do
not perform complete analyses of the metal
microstructures."
 
We will inform the list as more is learned.


Ruben Garcia










                
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Received on Sun 25 Jul 2004 08:33:39 PM PDT