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 ______________________________________________ Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
