[meteorite-list] weathering - from the inside out

From: Phil Morgan <roxfromspace_at_meteoritecentral.com>
Date: Fri, 17 Aug 2012 22:41:04 -0600
Message-ID: <CAMpwU7nYmBO0g_8Q7EQYYBrphE=Oew1LHq_roC3ZW6GyxJdj=Q_at_mail.gmail.com>

Thanks for the off-line replies.

The piece pictured is the infamous Al Haggounia 001.

I've noticed this weathering pattern previously in OC's but it is
quite pronounced in this particular stone. A bit of further research
led me to "NORTHWEST AFRICA 2828/AL HAGGOUNIA 001 IS A
WEATHERED, UNEQUILIBRATED EL CHONDRITE:
TRACE ELEMENT AND PETROLOGIC EVIDENCE
A. J. Irving1, T. E. Bunch2, A. E. Rubin3 and J. T. Wasson3."

Which mentions that this material "has undergone unusual terrestrial
weathering".

and that "The weathering of this ancient fall evidently involved
unusual Eh/pH conditions in a semi-arid environment, so that
differential dissolution of the primary metal occurred."

So, the piece pictured seems to be a poor example of my more general
question (but pretty cool for what it is).

Phil

On Fri, Aug 17, 2012 at 9:30 AM, Phil Morgan <roxfromspace at gmail.com> wrote:
> I've always found it curious that many heavily-weathered small stone
> NWA meteorites seem to be most altered at the center.
>
> For example, I've posted a photo showing one where the metal in the
> interior has completely weathered away.
> http://i25.photobucket.com/albums/c57/pkmorgan/postingpics/whatisit.jpg
>
> Can someone explain the processes behind this in a nutshell?
>
> This is a classified meteorite - anyone want to guess which one or at
> least the type?
>
> Happy Friday and Best Regards,
> Phil
Received on Sat 18 Aug 2012 12:41:04 AM PDT