[meteorite-list] Gebel Kamil webpage

From: info at niger-meteorite-recon.de <info_at_meteoritecentral.com>
Date: Thu, 29 Jul 2010 15:26:18 +0200 (CEST)
Message-ID: <1168187873.264417.1280409978817.JavaMail.open-xchange_at_oxltgw02.schlund.de>

The effects of sand abrasion (corrasion) and chemical weathering (corrosion) of
objects on a desert surface, apart from other factors, depend considerably on
the texture and composition of the original surface, but also on the dimensions
and the depth to which an object is buried in the soil.
?
It does make a difference whether the surface to be attacked is coated by a
smooth layer of magnetite and other iron oxides (fusion crust), or whether the
surface is a shear surface without any protective coating (and with?large micro
surfaces inviting contaminants to adhere).
?
Also the forming of caliche or calcrete due to evaporation and condensation
processes in hyper arid regions is usually limited to a very narrow zone close
to the surface. Parts of objects buried beyond this zone or protruding above it,
are affected in a much lesser degree. This effect can be observed quite well on
Kamil shrapnel. These conditions allow to interpret caliche deposits on desert
meteorites in certain cases as markers, indicating previous ground levels of
deflation zones. The strongest activity of chemical weathering in hyper arid
environments is limited to this very zone as well.
?
If we look at the majority of the corrasion activity, which is one of the
factors responsible for the characteristic sub-milimeter pitting on the
Kamil-shrapnel, it is limited to a specific zone as well. At normal prevailing
wind velocities the leaping motion of quartz sand grains (called saltation),
which abrades the surface of an obstacle, is usually limited to 0 ? 5
centimeters above the ground. But most of the damage occurs in the lower region
of the saltation zone.


Thus, conclusions drawn from weathering patterns of iron objects of different
sizes, surface qualities?and burying levels should be considered with caution.


Regards,?
Svend
?
?
Jason Utas <meteoritekid at gmail.com> wrote at 29. July 2010, 13:31:

> I had this post as a draft earlier - seems a perfect time to post it:
>
> Hello All,
> The initial expedition did in fact find more than one *complete
> individual* from the fall.
> If you take a look at the following website, you'll see links to two photos:
>
> http://www.b14643.de/Sahara/Kamil_Patatrac_Crater/index.htm
>
> Photo links:
>
> http://www.b14643.de/Sahara/Kamil_Patatrac_Crater/Kamil_1big.jpg
>
> http://www.b14643.de/Sahara/Kamil_Patatrac_Crater/Kamil_3big.jpg
>
> Take a look at the first and second photos.? Those are both in-situ
> photos; the meteorites have yet to be moved, or the dirt around them
> disturbed.
> Also note the differing shapes and the surface patina of each iron.? I
> initially thought that the iron might simply have been rolled over -
> but take a look at the patina visible in each photo.
> The surface of Gebel Kamil irons varies greatly: especially the
> contrast between exhumed and buried surfaces.? Exposed surfaces
> typically exhibit a dark patina and sometimes corrosion pitting.
> Buried surfaces are often better-preserved, but look entirely
> different; they're rusty.
>
> Both of the photos above are of the upper, sandblasted surfaces of
> meteorites that have yet to be moved from where they were found.
>
> So, two or more individuals.
>
> Regards,
> Jason
>
>
> On Thu, Jul 29, 2010 at 3:59 AM,? <bernd.pauli at paulinet.de> wrote:
> > http://www.b14643.de/Sahara/Kamil_Patatrac_Crater/index.htm
> >
> > Gary wrote: "...some of (what I believe are) Mirko's slices..."
> >
> >
> > Yep, and the 17.5-gram endcut pictured on the right
> > now resides in the Bernd Pauli meteorite collection :-)
> >
> > Note that "cometary" inclusion of schreibersite rimmed
> > by swathing kamacite and displaying shear deformation.
> >
> >
> > Best regards,
> >
> > Bernd
> >
> >
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Received on Thu 29 Jul 2010 09:26:18 AM PDT