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

[David Weir]

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