From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:00 2004
> I received a reply ... that Angrites have their origins from
> Carbonaceous Chondrites (probably CM2) material ... Is this
> possible that a Carbonaceous Chondrite can become a basaltic
> rock with anorthositic crystals and elevated levels of calcium?
McSWEEN H.Y.Jr. (1999) Meteorites and Their Parent Planets,
2nd Edition, Cambridge University Press, pp. 147-148:
The angrites are a small group of meteorites composed of
pyroxene, olivine, and plagioclase. The pyroxene is fassaite,
a distinctive composition rich in calcium, aluminum, and titanium.
Olivine contains considerable amounts of calcium, and plagioclase
is almost pure anorthite (the calcium-rich end member). These
mineral compositions reflect the marked enrichment in refractory
elements and depletion in volatiles that are characteristic of
angrites. The textures of angrites are variable, but all indicate
crystallization from basaltic magmas. They have very ancient ages,
approximately 4.56 billion years. The oxygen isotopic compositions
of angrites are indistinguishable from those of HED achondrites,
but differences in chemistry are interpreted to indicate that these
meteorites came from a separate parent body. Experiments suggest that
partial melting of chondrites under more oxidizing conditions than
those that produced eucrite magmas could have generated angrite melts.
Received on Sat 15 Sep 2001 09:26:54 PM PDT