[meteorite-list] Fusion crusts on stony meteorites

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Sat, 24 Mar 2007 17:52:19 -0700
Message-ID: <93aaac890703241752l497184e9l4ae383d170edcb23_at_mail.gmail.com>

Hello Marcin, All,
It's probably impossible to say precisely what that melt is without
tapping into those gas bubbles and checking out the composition of
whatever gas (if any) is in there.
Just because there is no other melt within the matrix of the meteorite
itself does not rule out the possibility of its being impact melt.
The fact that it occurs on the edge is actually not a bad indicator of
the vein of melt (if it is one) simply having been a weak point in the
stone. As it hit lower levels of the atmosphere and stress increased,
the stone would have split along the crack, and you get what we see -
a nice thick vein of melt along a side of the stone, which has since
been fused slightly over (it was early enough to remelt the surface of
the melt, but not early enough to burn it away completely).
Of course, there's the other angle as well - there is no other impact
melt in the meteorite (to suggest that this would indeed be melt), and
the only apparent melt occurs on he trailing edge of the stone where
one would expect a very thick fusion crust.
I tend to lean towards the possibility that this melt is fusion crust,
simply because I see no other melt (I know there are a few shock
veins, but you're looking at a substantial amount of melt there)
within the stone. It was an oriented stone, and I have seen unaltered
fragments of meteorite included within crust on the trailing edges of
highly oriented stones before - it's unusual, but not unheard-of to
see such things - most of the time, however, the meteorite simply
isn't cut (who cuts beautifully oriented meteorites..?) and I assume
that these features tend not to be seen for just such a reason.
Of course, in the original pictures that Marcin posted of the main
mass, the 'rear' of the meteorite did appear to be quite rough...a
late split along a weak vein of melt is possible, but I find this
unlikely given the appearance of the rest of the stone.
Regards,
Jason


On 3/23/07, PolandMET <marcin at polandmet.com> wrote:
> Some spies melting my emails to the list.
>
> Here is my personal collection full slice of NWA 2826.
> It have also this thick crust but not soo beautifull as on some other
> slices, but I have hold it as it was the only one full slice that contain
> soul of this LL5. Big troilites, one big chondrule?, large unknown dark
> inclusions and shock veins.
>
> I have leave photos in original size for better view, but it is only 2M pix
> so they are not soo sharp.
>
> Some fragments was glued back together becouse they was broken while cutting
> but fortunatelly I was able to find them and put together like puzzles.
>
> There are also interesting two different inclusions in this slice. This
> large dark one on the bottom side and one grey on the center right.
>
> slice is around 9cm wide
> ===============================
>
> http://www.meteoryt.net/ebay/P0019261.JPG
> http://www.meteoryt.net/ebay/P0019262.JPG
> macro view
> http://www.meteoryt.net/ebay/P0019263.JPG
> http://www.meteoryt.net/ebay/P0019264.JPG
> http://www.meteoryt.net/ebay/P0019265.JPG
> http://www.meteoryt.net/ebay/P0019266.JPG
> http://www.meteoryt.net/ebay/P0019267.JPG
> http://www.meteoryt.net/ebay/P0019268.JPG
> http://www.meteoryt.net/ebay/P0019269.JPG
>
>
> -----[ MARCIN CIMALA ]-----[ I.M.C.A.#3667 ]-----
> http://www.Meteoryt.net marcin at meteoryt.net
> http://www.PolandMET.com marcin at polandmet.com
> http://www.Gao-Guenie.com GSM +48(607)535 195
> --------[ Member of Polish Meteoritical Society ]--------
>
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Received on Sat 24 Mar 2007 08:52:19 PM PDT