[meteorite-list] Nice CAI in a CV3

[bernd.pauli at paulinet.de]

Rob wondered:

> If CAI's are the oldest things out there then how does chondritic
> material get completely encapsulated inside of one?

Martin mused:

> a cone or other shape where if cut along the right plane, it would
> appear as if the CAI was completely surrounding the chondrules, but
> in reality, the chondrule material is actually inside more of a CAI
> pipe or ice cream cone.

John B. added:

> could be a crucible shaped CAI with chondritic
> material within the bowl shaped depression.

and:

> may be a radically deformed crucible shaped CAI.

An interesting comment by Robert Hutchison culled from his book:

HUTCHISON R. (2004) Meteorites: A Petrologic, Chemical, and
Isotopic Synthesis (Cambridge Planetary Science Series, pp. 506).

On p. 229 (Chapter 7.4: Origin of CAI-rich inclusions), the author
writes: "The origin of CAIs is an enigma. They are probably older
than chondrules, which rarely enclose CAIs; the  r e v e r s e has
n o t  been found."

After a detail about 26Al synthesization, however, the author continues:

"... CAIs may have been almost contemporaneous with the earliest
chondrules."

* contemporaneous * ... This brings me back to an abstract I had read
half an hour before while trying to find something interesting on CAIs:

KROT A.N. (2000) Anorthite-rich chondrules from primitive carbonaceous
chondrites: Genetic links between CAIs and chondrules (Meteoritics and
Planetary Science 35-5, 2000, Suppl., A093):

"Although CAIs and chondrules formed in isotopically different regions, it
remains unclear (1) whether these regions were separated  s p a t i a l l y
or  t e m p o r a l l y  and (2) what was the (26Al/27Al)i in the chondrule-
forming regions."


Best wishes,

Bernd