[meteorite-list] A vs. Z and halite

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:49 2004
Message-ID: <DIIE.0000002300001BF1_at_paulinet.de>

Adam wrote:

> Two laboratories are currently studying Amgala and neither one has
> observed water bearing minerals but some interesting clasts have
> been found which we will report on later. Another party suggested
> halite because ~10% of the most recently collected broken stones
> show some oxidation on the exposed surfaces.

Hello Adam, John, and List,

The halite (NaCl) and sylvite (KCl) inclusions in Monahans and Zag are
mostly very small, and the tiny amount of liquid water [plus bubbles that
are in constant motion at room temperature(!)] they contain was found
locked in salt crystals inside the meteorites. That's why I don't believe
they are responsible for the oxidation on the exposed surfaces of some
Amgalas.

But, according to M.E. Zolensky et al., these halides (the "d" is not a typo)
may be the culprits of the sulfate / halide efflorescence noted on Antarctic
meteorites where preterrestrial halite was dissolved and then precipitated
once again. Thus the common assumption that the efflorescence is derived
from components introduced from the ice may have to be reconsidered.

Interestingly, my database query for salt deposits on/in Antarctic samples
resulted in 31 meteorites, all of which are CM or CK chondrites. The only
non-carbonaceous meteorite of all these is LEW 86022 and the description
says that only a: "... minute amount of salts is present in the interior".

When we last discussed Zag and Monahans, someone (I don't remember if
it was Jeff Grossman or Ron Baalke) wrote that "the water previously found
in the carbonaceous chondrites and Martian meteorites was not liquid water.
The water in these meteorites was extracted by heating the meteorites".

The question now is whether the salt deposits on Antarctic carbonaceous
chondrites are due to halides and/or sulfides, from the decomposition of
hydrated minerals (copiously present in carbonaceous chondrites), from
"components introduced from the ice" or whether these salt deposits are
due to a combination of all these phenomena.

One last interesting point: Zolensky et al. studied carbonaceous chondrite
clasts in Zag that had been discovered by "our" O.R. Norton (see p. 127,
Cambridge Encyclopedia of Meteorites). They suggest that there is a link
between this caronaceous clast and the halite in Zag !

References:

ZOLENSKY M.E. et al. (1999) Asteroidal Water Within Fluid-Inclusion-Bearing
Halite In Ordinary Chondrites (MAPS 34-4, Supplement, 1999, A124).

ZOLENSKY M.E. et al. (2003) Carbonaceous chondrite clasts in
the halite-bearing H5 chondrite Zag (MAPS 38-7, 2003, A114).


Best wishes,

Bernd
Received on Sun 14 Mar 2004 02:39:54 PM PST