[meteorite-list] CAI inclusions

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Sun, 07 Aug 2011 13:53:20 -0400
Message-ID: <8CE234202E270DF-104-F1D8_at_webmail-m035.sysops.aol.com>

Hello Ed,

First,, note that for Calcium Aluminum rich inclusions, "CAI Inclusion"
is redundant to say/type ... the third letter of CAI is "I" as in
*Interesting*, not "L" as in lazy. Which makes CAI a very funny
three-letter shorthand since the chemical symbol of Calcium is actually
Ca and Aluminum is Al... ok, the question ...

Maybe a simple question, but it really depends who you ask as to what
sort of answer you get. To most collectors, the answer is probably CV3
and perhaps CM if we are so lucky to have the latter in our
collections. ....because they are large and contrasty enough to see
without trashing too much material. However, the firast clue to the
diversity and abundance of CAIs comes from saying that even the Ivuna
(CI type specimen) which is highly aqueously altered has had CAI
studies.

"Big" CAIs are commonly seen oozing from CV3 types of carbonaceous
chondrites. CV3s also average the most abundance in the sense of mass
to my knowledge of CAIs.

However most chondrites contain CAIs if you are looking with a big
enough magnifying glass. Literally all carbonaceous chondrite types
have them relatively abundantly (compared to other meteorites, of
course), though sub-millimeter sized.

But you shouldn't categorize all of these CALs (Calcium Aluminum Lumps)
in the same category. Just like meteorites themselves, the types,
oxidations, alterations, compositions, etc., of CAIs vary. And DON't
jump to the conclusion that ALL CAIs were formed at the same time, nor
in the beginning of the beginning ... Even Bencubbinites, an oddly
related to carbonaceous class, but thermally quite altered, have tiny
detectable CAIs - Gujba for example. Isheyevo, an oddity similar to to
the bencubbinites has them at 1% the meteorites volume... could that
mean CAIs (and chondrules, btw) were formed in large object collisions,
vs. the commonly held belief of spontaneous or seeded condensation?
Beats me.

The CV3 Allende is perhaps the most classic for CV3 demonstrations, but
is actually atypical since it is rather highly oxidized within its clan
of meteorites. Vigarano, the CV3 type specimen for that class
(carbonaceous Vigarano type = CV) is actually much more representative
of CAIs from a perspective having a date with the virgin Solar System.

There are CAIs in E chondrites and well as H and low metal chondrites,
in lower concentrations. Semarkona (LL3) is an interesting study
target in which the CAIs have been studies and compared. Maybe Dr.
Grossman is interested in adding or correcting something ...

Meanwhile hope that helps! best wishes,

Doug




  Allende is somewhat atypical in this sense and Vigarano is more
representative.


of sort
-----Original Message-----
From: E.P. Grondine <epgrondine at yahoo.com>
To: meteorite-list at meteoritecentral.com
Sent: Sat, Aug 6, 2011 8:12 pm
Subject: [meteorite-list] CAI inclusions


Hi all -

Simple question - what classes of meteorites have CAI inclusions?

E.P.
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Received on Sun 07 Aug 2011 01:53:20 PM PDT