[meteorite-list] Ureilite Origins
From: meteoriteshow <meteoriteshow_at_meteoritecentral.com>
Date: Mon Sep 6 14:49:39 2004 Message-ID: <00d901c49442$6339c7e0$6396e052_at_ibmthinkpad> Thanks for your response Bernd! As far as CI are concerned, yes they have no chondrule and I did not think of them before writing my e-mail. But then the oxygen-isotope study is getting us confused... CV?... As far as I know, there was no evidence of presolar diamonds existence. Am I right or wrong? Should they exist, and should one find some in a Ureilite, what can we expect then about the origin of those meteorites? I know that some studies are on rails both in France and Japan about Ureilites, so let's hope that they will bring some answers... Cheers, Fred ----- Original Message ----- From: <bernd.pauli_at_paulinet.de> To: <Meteorite-list_at_meteoritecentral.com> Sent: Monday, September 06, 2004 8:31 PM Subject: [meteorite-list] Ureilite Origins > They had to have been carbonaceous meteorites of some sort to begin > with, but the articles I've seen don't seem to offer a clear picture > of what they were like before they were shocked. CM, perhaps? Hello Marc, Fr?d?ric, and List, Here is what I've harvested during the last few minutes: Cyrena Anne Goodrich, Lunar and Planetary Laboratory, University of Arizona Invited Review - Ureilites: A critical review (Meteoritics 27-4, 1992, pp. 327-352): 1) Nilpena contains clasts of carbonaceous chondrite matrix material. Detailed petrographic and mineralogic studies have shown that this material has close affinities to CI - and differs substantially from CM-matrix (Brearley and Prinz, 1989; 1992). Fr?d?ric, "close affinities to CI" would also explain why we do not find any chondrules or relict chondrules in ureilites - there have never been any. But, ... now look at this - it is from the same review by C.A. Goodrich: 2) CI-matrix clasts in Nilpena have an oxygen-isotope composition plotting on the extension of the Allende mixing line on the 17^O-rich side of the terrestrial fractionation line, rather than within the field of CI matrix compositions (Brearley and Prinz, 1992). So the starting material may have been CI- o r CV-like. If it was CV-like, we might really expect to find traces of chondrules or at least chondrule precursor material. Best wishes, Bernd ______________________________________________ Meteorite-list mailing list Meteorite-list_at_meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Mon 06 Sep 2004 02:50:31 PM PDT |
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