[meteorite-list] Acapulcoites and NWA 725
I'm must be missing something. What could one conclude by comparing thin sections of NWA 725 and a known winonaite? I understand that distinguishing among acapulcoites, lodranites and winonaites is not a textural exercise nor can they be resolved by just their mineral composition. Hello John and List, I thought other list members might also be interested in this thread, so I hope you don't mind me sending this mail to the List as well. No, you are not missing anything. Hand samples of acapulcoites, lodranites and winonaites look pretty much the same tan color (at least to me). Only the micro- scope will reveal their subtle textural differences and only a thin section in polarized light will show mineralogical differences or differences in grain size. Unortunately I still don't have a thin section of an acapulcoite but the one pictured in Marvin Killgore's Color Atlas of Meteorites in Thin Section on pages 208-211 (Acapulco) surely looks different than the winonaite on pages 232-235 (NWA 1054). Something readily noticed is grain-size: The grains in winonaites are usually smaller than in acapulcoites. I know, unfortunately their grain sizes overlap as a comparative overview on p. 252 of Hutchison (Meteorites: A Petrologic, Chemical, and Isotopic Syn- thesis ) shows. To make matters even worse: almost all cited properties overlap :-( Maybe the amount of troilite in NWA 725 could help here. According to Hutchison, acapulcoites have 3-6 vol% FeS whereas winoaites have 1-19 %. The mineral composition of NWA 725 may also be useful in determining whether it is a winonaite or an acapulcoite. Olivine Fo and orthopyroxene En have (slightly) higher values in winonaites, and the same is valid for plagioclase An. Unfortunately both acapulcoites and winonaites can have relict chondrules, so this doesn't help either. But what may help is the fact that winonaites are more depleted in 16-O and so plot closer to the terrestrial fractionation line than acapulcoites. Well, you are right ... a thin section will not disclose such information so I can only repeat what I already mentioned above: grain size and visual appearance of thin sections of winonaites and acapulcoites - they just look different to me and Hutchison also states: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. So, maybe, the grain size of NWA 725 visible under the microscope does hold a clue ... Cheers, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Acapulcoites and NWA 725
Hmm ?!? Just noticed something contradictory: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. Marvin's pic of the Acapulco thin section shows grains that are coarser than the ones of NWA 1054 but maybe this is a result of the different fields of view: 1.8 cm for NWA 1054 and 1.2 cm for Acapulco Best wishes, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoites and NWA 725
--- [EMAIL PROTECTED] ha scritto: Unortunately I still don't have a thin section of an acapulcoite but the one pictured in Marvin Killgore's Color Atlas of Meteorites in Thin Section on pages 208-211 (Acapulco) surely looks different than the winonaite on pages 232-235 (NWA 1054). but NWA 1054 is not a winonaite, but a acapulcoite. Matteo M come Meteorite - Matteo Chinellato Via Triestina 126/A - 30030 - TESSERA, VENEZIA, ITALY Email: [EMAIL PROTECTED] Sale Site: http://www.mcomemeteorite.it Collection Site: http://www.mcomemeteorite.info MSN Messanger: spacerocks at hotmail.com EBAY.COM:http://members.ebay.com/aboutme/mcomemeteorite/ ___ Yahoo! Messenger with Voice: chiama da PC a telefono a tariffe esclusive http://it.messenger.yahoo.com __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoites and NWA 725
hello this is the official study and analysis http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1808.pdf Matteo --- [EMAIL PROTECTED] ha scritto: Hmm ?!? Just noticed something contradictory: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. Marvin's pic of the Acapulco thin section shows grains that are coarser than the ones of NWA 1054 but maybe this is a result of the different fields of view: 1.8 cm for NWA 1054 and 1.2 cm for Acapulco Best wishes, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list M come Meteorite - Matteo Chinellato Via Triestina 126/A - 30030 - TESSERA, VENEZIA, ITALY Email: [EMAIL PROTECTED] Sale Site: http://www.mcomemeteorite.it Collection Site: http://www.mcomemeteorite.info MSN Messanger: spacerocks at hotmail.com EBAY.COM:http://members.ebay.com/aboutme/mcomemeteorite/ ___ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Acapulcoites and NWA 725
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1808.pdf Matteo, thank you for the link. An interesting detail with regard to NWA 725's status as a winonaite or an acapulcoite might be this conclusion by the authors at the end of the paper: ... the Cr2O3 contents of high-Ca pyroxenes, (1.56 - 1.85 wt. %), are, according to [5], in good agreement with those displayed by acapulcoite meteorites, since winonaites exhibit much lower contents (around 0.2 wt. %). Best wishes, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Acapulcoites and NWA 725
Hmm-ing again :-) The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. Could this by a typo because: Marvin's pic of the Acapulco thin section shows grains that are coarser than the ones of NWA 1054 ... and because: The Antarctic acapulcoite TIL 99002 is mineralogically similar to GRA 98028 but has a larger grain size (300-400 µm) than GRA 98028 (50-100 µm). (Met.Bull. 86, MAPS 37-7, July 2002). .. and now back to Hutchison who states in Table 8.2 on page 252: Grain-size of acapulcoites = 150-230 µm Grain-size of winonaites = 55-230 µm Regards, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoites and NWA 725
Bernd, I don't mind at all. I think I'm with you wishing I could lean over the 'scope and think Ah, yes, heat and time makes crystals grow and chondrules disappear. Metal migrates and other stuff does too. And thereby progress in an orderly way from chondrites through these primitive achondrites. Unfortunately, it looks like there is more to it than that. In Discrimination of Acapulcoites and Lodranites from Winonaites Rumble et al. state: Combined petrological and oxygen isotopic analyses of five Northwest African primitive achondrites . . . have clarified the relationships among acapulcoites, lodranites and winonaites. It would not be possible to properly classify some specimens in these groups using their mineral compositions alone . . . . http://www.lpi.usra.edu/meetings/metsoc2005/pdf/5138.pdf To say nothing of mere appearances. I don't know what to think about Marvin's NWA 1054 Winonaite. Matteo points out that NWA 1054 is an acapulcoite. Further, I don't see the abundant 120° triple junctions mentioned in the descriptions of NWA 1054. To me it looks a lot like NWA 725 (Tissemoumine). The differences I see under the microscope aren't very subtle. Nor are they orderly. Please see these examples. The fields of view are all the same, three and a half millimeters from left to right. http://www.johnkashuba.com/Ach%20Acapulcoites_and_Winonaites.html Regards, - John John Kashuba Ontario, California - Original Message - From: [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, February 16, 2006 11:02 AM Subject: [meteorite-list] Acapulcoites and NWA 725 I'm must be missing something. What could one conclude by comparing thin sections of NWA 725 and a known winonaite? I understand that distinguishing among acapulcoites, lodranites and winonaites is not a textural exercise nor can they be resolved by just their mineral composition. Hello John and List, I thought other list members might also be interested in this thread, so I hope you don't mind me sending this mail to the List as well. No, you are not missing anything. Hand samples of acapulcoites, lodranites and winonaites look pretty much the same tan color (at least to me). Only the micro- scope will reveal their subtle textural differences and only a thin section in polarized light will show mineralogical differences or differences in grain size. Unortunately I still don't have a thin section of an acapulcoite but the one pictured in Marvin Killgore's Color Atlas of Meteorites in Thin Section on pages 208-211 (Acapulco) surely looks different than the winonaite on pages 232-235 (NWA 1054). Something readily noticed is grain-size: The grains in winonaites are usually smaller than in acapulcoites. I know, unfortunately their grain sizes overlap as a comparative overview on p. 252 of Hutchison (Meteorites: A Petrologic, Chemical, and Isotopic Syn- thesis ) shows. To make matters even worse: almost all cited properties overlap :-( Maybe the amount of troilite in NWA 725 could help here. According to Hutchison, acapulcoites have 3-6 vol% FeS whereas winoaites have 1-19 %. The mineral composition of NWA 725 may also be useful in determining whether it is a winonaite or an acapulcoite. Olivine Fo and orthopyroxene En have (slightly) higher values in winonaites, and the same is valid for plagioclase An. Unfortunately both acapulcoites and winonaites can have relict chondrules, so this doesn't help either. But what may help is the fact that winonaites are more depleted in 16-O and so plot closer to the terrestrial fractionation line than acapulcoites. Well, you are right ... a thin section will not disclose such information so I can only repeat what I already mentioned above: grain size and visual appearance of thin sections of winonaites and acapulcoites - they just look different to me and Hutchison also states: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. So, maybe, the grain size of NWA 725 visible under the microscope does hold a clue ... Cheers, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoites and NWA 725
Hello NWA 1054 was very affected, and its 100% confirmed is a acapulcoite - many oldest why we have found complete chondrules into - and is paired to nWA 1052, another acapulcoite. The problem is, NWA 1052/1054 have the same matrix of NWA 1058, and this have the same problems of classification why one say its a primitive achondrite like winonaite, another say its a acapulcoite etc...all 3 examples have complete chondrules and not relitic. In only one we have found Melliniite, other 2 notmistery Matteo --- Kashuba, Ontario, California [EMAIL PROTECTED] ha scritto: Bernd, I don't mind at all. I think I'm with you wishing I could lean over the 'scope and think Ah, yes, heat and time makes crystals grow and chondrules disappear. Metal migrates and other stuff does too. And thereby progress in an orderly way from chondrites through these primitive achondrites. Unfortunately, it looks like there is more to it than that. In Discrimination of Acapulcoites and Lodranites from Winonaites Rumble et al. state: Combined petrological and oxygen isotopic analyses of five Northwest African primitive achondrites . . . have clarified the relationships among acapulcoites, lodranites and winonaites. It would not be possible to properly classify some specimens in these groups using their mineral compositions alone . . . . http://www.lpi.usra.edu/meetings/metsoc2005/pdf/5138.pdf To say nothing of mere appearances. I don't know what to think about Marvin's NWA 1054 Winonaite. Matteo points out that NWA 1054 is an acapulcoite. Further, I don't see the abundant 120° triple junctions mentioned in the descriptions of NWA 1054. To me it looks a lot like NWA 725 (Tissemoumine). The differences I see under the microscope aren't very subtle. Nor are they orderly. Please see these examples. The fields of view are all the same, three and a half millimeters from left to right. http://www.johnkashuba.com/Ach%20Acapulcoites_and_Winonaites.html Regards, - John John Kashuba Ontario, California - Original Message - From: [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, February 16, 2006 11:02 AM Subject: [meteorite-list] Acapulcoites and NWA 725 I'm must be missing something. What could one conclude by comparing thin sections of NWA 725 and a known winonaite? I understand that distinguishing among acapulcoites, lodranites and winonaites is not a textural exercise nor can they be resolved by just their mineral composition. Hello John and List, I thought other list members might also be interested in this thread, so I hope you don't mind me sending this mail to the List as well. No, you are not missing anything. Hand samples of acapulcoites, lodranites and winonaites look pretty much the same tan color (at least to me). Only the micro- scope will reveal their subtle textural differences and only a thin section in polarized light will show mineralogical differences or differences in grain size. Unortunately I still don't have a thin section of an acapulcoite but the one pictured in Marvin Killgore's Color Atlas of Meteorites in Thin Section on pages 208-211 (Acapulco) surely looks different than the winonaite on pages 232-235 (NWA 1054). Something readily noticed is grain-size: The grains in winonaites are usually smaller than in acapulcoites. I know, unfortunately their grain sizes overlap as a comparative overview on p. 252 of Hutchison (Meteorites: A Petrologic, Chemical, and Isotopic Syn- thesis ) shows. To make matters even worse: almost all cited properties overlap :-( Maybe the amount of troilite in NWA 725 could help here. According to Hutchison, acapulcoites have 3-6 vol% FeS whereas winoaites have 1-19 %. The mineral composition of NWA 725 may also be useful in determining whether it is a winonaite or an acapulcoite. Olivine Fo and orthopyroxene En have (slightly) higher values in winonaites, and the same is valid for plagioclase An. Unfortunately both acapulcoites and winonaites can have relict chondrules, so this doesn't help either. But what may help is the fact that winonaites are more depleted in 16-O and so plot closer to the terrestrial fractionation line than acapulcoites. Well, you are right ... a thin section will not disclose such information so I can only repeat what I already mentioned above: grain size and visual appearance of thin sections of winonaites and acapulcoites - they just look different to me and Hutchison also states: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. So, maybe, the grain size of NWA 725 visible under the microscope does hold
Re: [meteorite-list] Acapulcoites and NWA 725 - correct
Hello NWA 1054 was very studied, and its 100% confirmed is a acapulcoite - many oldest why we have found complete chondrules into - and is paired to nWA 1052, another acapulcoite. The problem is, NWA 1052/1054 have the same matrix of NWA 1058, and this have the same problems of classification why one say its a primitive achondrite like winonaite, another say its a acapulcoite etc...all 3 examples have complete chondrules and not relitic. In only one we have found Melliniite, other 2 notmistery Matteo --- Kashuba, Ontario, California [EMAIL PROTECTED] ha scritto: Bernd, I don't mind at all. I think I'm with you wishing I could lean over the 'scope and think Ah, yes, heat and time makes crystals grow and chondrules disappear. Metal migrates and other stuff does too. And thereby progress in an orderly way from chondrites through these primitive achondrites. Unfortunately, it looks like there is more to it than that. In Discrimination of Acapulcoites and Lodranites from Winonaites Rumble et al. state: Combined petrological and oxygen isotopic analyses of five Northwest African primitive achondrites . . . have clarified the relationships among acapulcoites, lodranites and winonaites. It would not be possible to properly classify some specimens in these groups using their mineral compositions alone . . . . http://www.lpi.usra.edu/meetings/metsoc2005/pdf/5138.pdf To say nothing of mere appearances. I don't know what to think about Marvin's NWA 1054 Winonaite. Matteo points out that NWA 1054 is an acapulcoite. Further, I don't see the abundant 120° triple junctions mentioned in the descriptions of NWA 1054. To me it looks a lot like NWA 725 (Tissemoumine). The differences I see under the microscope aren't very subtle. Nor are they orderly. Please see these examples. The fields of view are all the same, three and a half millimeters from left to right. http://www.johnkashuba.com/Ach%20Acapulcoites_and_Winonaites.html Regards, - John John Kashuba Ontario, California - Original Message - From: [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, February 16, 2006 11:02 AM Subject: [meteorite-list] Acapulcoites and NWA 725 I'm must be missing something. What could one conclude by comparing thin sections of NWA 725 and a known winonaite? I understand that distinguishing among acapulcoites, lodranites and winonaites is not a textural exercise nor can they be resolved by just their mineral composition. Hello John and List, I thought other list members might also be interested in this thread, so I hope you don't mind me sending this mail to the List as well. No, you are not missing anything. Hand samples of acapulcoites, lodranites and winonaites look pretty much the same tan color (at least to me). Only the micro- scope will reveal their subtle textural differences and only a thin section in polarized light will show mineralogical differences or differences in grain size. Unortunately I still don't have a thin section of an acapulcoite but the one pictured in Marvin Killgore's Color Atlas of Meteorites in Thin Section on pages 208-211 (Acapulco) surely looks different than the winonaite on pages 232-235 (NWA 1054). Something readily noticed is grain-size: The grains in winonaites are usually smaller than in acapulcoites. I know, unfortunately their grain sizes overlap as a comparative overview on p. 252 of Hutchison (Meteorites: A Petrologic, Chemical, and Isotopic Syn- thesis ) shows. To make matters even worse: almost all cited properties overlap :-( Maybe the amount of troilite in NWA 725 could help here. According to Hutchison, acapulcoites have 3-6 vol% FeS whereas winoaites have 1-19 %. The mineral composition of NWA 725 may also be useful in determining whether it is a winonaite or an acapulcoite. Olivine Fo and orthopyroxene En have (slightly) higher values in winonaites, and the same is valid for plagioclase An. Unfortunately both acapulcoites and winonaites can have relict chondrules, so this doesn't help either. But what may help is the fact that winonaites are more depleted in 16-O and so plot closer to the terrestrial fractionation line than acapulcoites. Well, you are right ... a thin section will not disclose such information so I can only repeat what I already mentioned above: grain size and visual appearance of thin sections of winonaites and acapulcoites - they just look different to me and Hutchison also states: The winonaites are texturally similar to acapulcoites, but the winonaites contain coarser grains and abundant crosscutting metal-sulfide veins. So, maybe, the grain size of NWA 725 visible under the microscope does hold
[meteorite-list] Acapulcoites and NWA 725
FLOSS C. et al. (2002) Acapulcoite complexities: Clues from trace element distributions (MAPS 37-7, 2002, A047, excerpts): 1. Acapulcoites and lodranites are primitive achondrites from a common parent body that experienced variable degrees of partial melting and melt migration. 2. NWA 725 exhibits features suggesting it may be more primitive than other acapulcoites, including the presence of relict chondrules. 3. NWA 725 shows evidence of more extensive heating that may have included some silicate partial melting. 4. NWA 725 orthopyroxenes have Ti, Zr and REE abundances that fall within the ranges observed for lodranite orthopyroxenes. 5. NWA 725 does not appear to be depleted in plagioclase and troilite. Best wishes, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Acapulcoites and NWA 725
Stan and David kindly wrote: As for NWA 725, here are the details as Stan shared them with me: Recent O-isotopic analysis of a probable paired stone...by the Open University resolves the material clearly within the winonaite field. Hello List, Does anyone have a NWA 725 thin section and a winonaite thin section? Maybe they could share their observations and conclusions with the List! Just a few hours ago we were discussing the problems that may arise when trying to pair meteorites, especially NWA's (from multiple sources). The infamous NWA 869-ers I own and that I have seen look so different I can hardly believe all of them are NWA 869. So, maybe Stan's paired stone and the *original* Tissemoumine (NWA 725) are not the same material?!? Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
