[meteorite-list] NEW Plutonic Angrite - NWA 4590 "Tamassint"

From: David Weir <dgweir_at_meteoritecentral.com>
Date: Thu, 12 Apr 2007 22:03:58 -0400
Message-ID: <461EE50E.90700_at_earthlink.net>

Hello Sterling and hopeful Hermean collectors,

The angrites have FeO contents in the general range of ~25 wt%, so if
they are from Mercury this does not conform to your inverse iron core
ordering, unless the core of Mercury was not fully differentiated before
the impact-related dissemination occurred. Some angrites like NWA 2999
do contain too much iron to be consistent with representing a completely
differentiated body. As for the stable orbit, the iron cores of early
differentiated bodies which formed near Mercury and now stored in the
inner asteroid belt is a good point, although I was thinking about
possible Lagrange-like regions. Storage in the the inner asteroid belt
is definitely more reasonable.

For Rob, here is some CRE age info:

The results of CRE age studies (Eugster et al., 2002) utilizing
cosmogenic nuclide data indicate that the CRE age of D'Orbigny (12.3
+/-0.9 m.y.) is significantly different from that of other angrites
studied: Sah 99555 (6.6 +/-0.8 m.y.), Asuka 881371 (5.4 +/-0.7 m.y.),
Angra dos Reis (55.5 +/-1.2 m.y.), LEW 86010 (17.6 +/-1.0 m.y.), and LEW
87051 (~0.2 m.y.). All or most of these angrites represent unique
ejection events on the angrite parent body. I don't have CRE data yet
for the latest finds.

David
Received on Thu 12 Apr 2007 10:03:58 PM PDT