[meteorite-list] CAIs

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:54:02 2004
Message-ID: <3C65501D.99888B69_at_lehrer1.rz.uni-karlsruhe.de>

Hello Michel, Rhett, and List,

Michel Franco wrote:

> I discovered some white clasts inside what seems to be
> a weathered chondrite. It does not look like a terrestrial
> contamination into cracks and I was wondering if it could
> be a CAI.

Rhett wrote:

> I've not really heard of CAI's being found in ordinary
> chondrites before but I would guess that it is possible.

Michel also wrote:

> If one has some time to lighten my ignorance I will really appreciate.

I can't enlighten you but Harry McSween can :-)

McSWEEN H.Y. (1999) Meteorites and Their Parent Planets, 2nd
Edition (Cambridge University Press). Excerpt from page 56:

Other interesting components of chondrites are the refractory inclusions
(also called calcium aluminum-rich inclusions, or "CAIs"). These are
especially abundant in certain groups of carbonaceous chondrites, but

==> they occur rarely in other chondrite clans as well.<==

Refractory inclusions take many forms, but most appear to have some
kind of concentric structure formed by layers of different minerals.
The minerals in these inclusions (commonly silicates and oxides rich
in calcium and aluminum, such as melilite and spinel) tend to crystal-
lize at high temperatures, and for this reason they are thought to have
been some of the first materials in chondrites to form. Some inclusions
have internal textures that are similar to those of chondrules and sig-
nify that they crystallized from liquids, but others are ambiguous.


Best CAIs, sorry, REGs,

Bernd
Received on Sat 09 Feb 2002 11:36:45 AM PST