[meteorite-list] Angrite NWA 4931 & Willamette cutting

From: John Hendry <pict_at_meteoritecentral.com>
Date: Sun, 13 Sep 2009 12:03:06 +0300
Message-ID: <000601ca3451$02c216b0$08464410$_at_co.uk>

Elton,

I subsequently found the missing bit here...
http://www.darrylpitt.com/willamette.html

The article states that there is evidence of sampling elsewhere, and that
"science was again served when this meteorite was cut in 1997" and the end
piece in question was removed. So twelve years ago there was undoubtedly no
issues with core sampling technology not being available, so science would
appear to have been served in a clumsy fashion. Possibly something to do
with the trade value of an end piece versus a core?

Greg,

I like this, it looks much less intrusive..
>Link to image of core sampling at MIT laboratory:
>http://www.lunarrock.com/nwa4931/nwa4931core.jpg

Interesting paper you link to...
>Link to LPSC abstract on magnetic field on Angrite Parent Body:
>http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2143.pdf

Especially interesting (re: D'Orbigny) is the differentiation of the random
field from the collector's magnet and the stable oriented field presumably
induced by the parent body. Now the stable oriented field is discounted as
having been acquired by slow thermal acquisition of the earth's field after
landing (VRM) or from recrystallisation from a weathering process. However
is there any possibility that an oriented meteorite might become magnetised
on entry - it gets hot (ok, probably not in the middle), keeps it's
orientation, and crosses the earth's albeit rather weak flux extremely
quickly?

Also I thought coercivity was the resistance to demagnetisation and was
related to the magnetic material. I therefore don't get how one can have one
magnetic material (the meteorite) carrying high and low coercivity fields
unless the fields are carried in different mineral components e.g. one in
pyrrhotite and one in magnetite (or throw native iron into the mix). Maybe
this is the point that the stable field is held equally through all magnetic
minerals but the one from the collector's magnet only really established
itself in the more easily magnetised (and demagnetised) component - whatever
that is (iron I guess).

Regards,
John
Received on Sun 13 Sep 2009 05:03:06 AM PDT