[meteorite-list] fusion crust observation

From: EL Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 09:54:07 2004
Message-ID: <3C73D0EB.61BC0A24_at_epix.net>

Greetings List, Dave,

Gases? Could be a connection but not the reason there is a difference. The
smoothness of Millibillillie is likely accounted for by its distinctly different
chemistry/mineral makeup..... Eucrites have a glassy fusion crust because they
are more homogeneous and have already had their gases "outgased" in the original
melt of formation ( note Ibitria ,however, as an a vesiculated exception .)

Carbonaceous material such as Allende is more loosely consolidated and could be
subject to "plucking" of small grains during transit (as well as low melting
point material). The voids I see in the crust are irregular cavities so I tend
to discount them as a gas pocket-not saying that they could not be from gas
voids.

Outgasing is a possibility if you consider that the methane in Carbs are locked
in by the cold, one could theorize, and that localized heating liberated some
aromatics and left voids in the crust. However, cutting should liberate
existing pockets also it that were the case and I don't see those cavities
within the sliced sections. These could also be a version of cooling cracks
when the fused material contracts upon cooling. Looks like we need to look
closer at this phenomena.

So, while gas could be involved in Allende's crustal pits, it shouldn't be the
reason eucrites have a smoother crust.

Regards,
Elton

Dave Harris wrote:

> Hello listees,
> ...bit of an obvious observation but I noticed on my Allende individual I
> got today (Thanks, Christian!) that the fusion crust is peppered with tiny
> holes whereas my Millbillillie crust is a solid (unperforated) glassy coat.
> I guess I know why this is ie exgassing during atmospheric entering, butI
> was just curious as to what EXACTLY what gases were escaping - water vapour
> or whatever.
> And therefore the assumption that Millbillillie has far less 'free' gases in
> the matrix maybe drawn.
> Any comments?
>
> very best!
>
> --
> In gentle decay,
> dave
>
> IMCA #0092
Received on Wed 20 Feb 2002 11:38:08 AM PST