[meteorite-list] NWA 4679 Molten Chondrule?

From: bernd.pauli at paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: 04 Mar 2007 12:45:51 UT
Message-ID: <DIIE.000000BA000017DA_at_paulinet.de>

I purchased a 4.0g part slice of NWA 4679 from Carsten Giessler a couple
of weeks ago and would appreciate any comments on this unusual looking
chondrule. The piece I bought is visible at the bottom of this page:
 
http://www.gi-po.de/ebayfolder/shop/carbopre/carbo.htm
 
The feature I'm referring to is at the top left corner of the piece in
Carsten's image. I've tried to get a close up, apologies for the quality:

http://www.zen98648.zen.co.uk/temp/nwa4679_closeup_small.jpg
 
The larger chondrule is about 2mm diameter. The smaller one has a pale
(bleached?) outer layer and is darker inside. The small chondrule has an
appearence suggesting is has melted and flowed around the outside of the
larger chondrule. The darker central region is distorted into a tear-drop
shape.

Hello Matt, Carsten, and List,

No direct answer but, ...

Here is what I wrote to Carsten and to Christian after I had thoroughly looked
at my 8-gram part slice and at all the other slices that Carsten offered in his
presale campaign:

As such macrochondrules have not been observed in CK chondrites, I wonder
where this huge 12-mm BO chondrule comes from. Maybe from the meteorite
that collided with the CK parent body of NWA 4679? If so, was it an H, an L,
or an LL chondrite? The sheer size of this macrochondrule speaks in favor of
an L chondrite.

Looking at slice #10 and at slice #11, I noticed the chondrules seem to have a
preferred orientation as if matrix and chondrule material had been solidified when
still in a half-molten state.

If that is true the dark, quasi chondrule-free areas that Carsten describes as clasts
might be material that was molten on impact (or some other scenario) and we might
be looking at an impact-melted CK4 (CK3.8 - according to M. Denise) if such a
thing exists.

Furthermore I noticed that these chondrule-free clasts have different hues. Within that
area in slice #6 - let me just call it "river of melt" for the moment - you can see such
color shades on the left in Carsten's picture #6, no.2: a triangular, somewhat darker "clast"
(in the picture that clast looks like the contraction cracks in the fresh fusion crust of a
meteorite) seems to be wedged into this "river of melt".

As for your "droplet" chondrule, maybe it is an intermediary type: half chondrule, half
CAI. The late R. Hutchison mentions chondrules that are "texturally and mineralogically
intermediate between ferromagnesian chondrules and CAIs". Such chondrules have
"igneous textures and may be of droplet or clast type".

Well, "igneous" again points toward something that solidified from a melt. I'm really
looking forward to hearing more about NWA 4679 from professional meteoriticists!

Cheers,

Bernd

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Received on Sun 04 Mar 2007 07:45:51 AM PST