[meteorite-list] Carancas Thin sections

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun, 7 Oct 2007 16:53:46 -0500
Message-ID: <12a801c8092c$8a821110$b92ee146_at_ATARIENGINE>

Thanks, Bernd,

The video in the link Stefan Brandes supplied:
http://spacefiles.blogspot.com/2007/10/carancas-meteorite-peru.html
shows a local resident holding a "meteorite' under a
magnifying glass -- a perfect grey metal sphere like
a ball bearing -- so we know it contained free metal
in droplet form, which I assume is the source of the
INGEMMET bulk analysis of 15% kamacite.

But in so many photos, the metorite matrix appears
to be very, very light; in many photos it's almost white.
I'll admit to being petrologically challenged, but it seems
to me that a matrix that incorporates a large amount of
chemically bound iron would not appear so "blanco."
In some photos the meteorite doesn't appear so white,
so perhaps it's an exposure control effect introduced
by the photographer.

Perfectly in character for an ambiguous event.


Sterling K. Webb
---------------------------------------------------------------------
----- Original Message -----
From: <bernd.pauli at paulinet.de>
To: <meteorite-list at meteoritecentral.com>
Sent: Sunday, October 07, 2007 4:01 PM
Subject: [meteorite-list] Carancas Thin sections


Sterling wrote:

"People who understand thin sections are invited to comment in reply"

Hi Sterling and List,

Unfortunately these thin section pics are very low-resolution so it is hard
to judge from these low-quality pictures. But let's try and others, like
John
Kashuba, are invited to chime in.

The dark areas in the cross-polarized image are probably opaque minerals
(metal, troilite, etc.) and the conclusion we can draw is that this
meteorite
is metal- and FeS-rich, in other words an H5 or H6 chondrite (I think Mike
Farmer already said so in one of his first mails).

On the left, in the nine o'clock position there is a small, circular
chondrule
that has a thick, igneous rim of, well, I guess olivine (vivid purplish red)
and
pyroxene (blue tints ... pigeonite ???).

Between this chondrule and an even smaller chondrule right of center (tiny
BO
chondrule???), there is a "conglomerate" of what may have been one or
several
large BO chondrules (chondrule fragments). This causes a bit of headache
because,
if this is or was a large BO chondrule, I wouldn't rule out an L chondrite
as H
chondrites tend to have smaller chondrules!

Right above center, there is what looks like a POP (porphyritic
olivine-pyroxene)
chondrule about the same size as the one in the nine o'clock position.

The overall texture is that of a recrystallized chondrite (H5 or H6, L5 or
L6)
but as the chondrule in the 9 o'clock position is relatively unaltered as is
the
small one right of center, I'd say it might be an H5 or an L5.

Best wishes,

Bernd (who neither owns Cali nor Carancas)


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Received on Sun 07 Oct 2007 05:53:46 PM PDT