[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, Frédéric, 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). Frédéric, 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 [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Ureilite Origins
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: [EMAIL PROTECTED] To: [EMAIL PROTECTED] 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, Frédéric, 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). Frédéric, 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 [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Ureilite Origins
Bernd and List, Aside from the origin of ureilites, it appears that traces of chondrules are found in polymict ureilites and are probably from impactors - like the chondrules sometimes found in howardites. See Mr. Weir's page on DaG 319. I might be lucky enough to have a thin section of DaG 319 that contains a chondrule. Tell me what you think. http://www.johnkashuba.com/Ach_DaG_319_Ureilite_-_Polymict.html Regards, John Kashuba Ontario, California - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Monday, September 06, 2004 11:31 AM 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, Frédéric, 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). Frédéric, 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 [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list
