Re: [meteorite-list] Acapulcoite/Lodranite Parent-body
Wow... thanks for all of those references and for the info below Jason. And thanks also to everyone else who replied both on and off list with their helpful input. It's very much appreciated! Thanks, Jeff - Original Message - From: Jason Utas meteorite...@gmail.com To: Meteorite-list meteorite-list@meteoritecentral.com; Jeff Kuyken i...@meteorites.com.au Sent: Tuesday, July 20, 2010 1:54 PM Subject: Re: [meteorite-list] Acapulcoite/Lodranite Parent-body Hello Jeff, There is a great deal of literature online that addresses this topic -- in addition to the McCoy research. The general consensus is that the Acapulcoite/Lodranite parent body was heterogeneously metamorphosed (impact-melted or partially-differentiated, depending on which paper you read) and was then largely broken up by an impact(s) nearly 4.6 billion years ago. Lodranites and Acapulcoites have been differentiated in the past almost solely based on structural observations/grain size. The trouble is that the cutoff between the two has traditionally been determined by grain size and is not clearly defined - check out the discussion section of this paper (also in the list of sources below) for a good summary: http://www.lpi.usra.edu/meetings/LPSC98/pdf/1237.pdf Here's the meat of it: Acapulcoites experienced only low degrees of Fe,Ni- FeS cotectic melting and have maintained essentially chondritic troilite and plagioclase abundances, whereas lodranites experienced higher degrees of melting that included partial silicate melting with subsequent loss of troilite and/or plagioclase fractions. If you keep reading through the discussion, you'll find that the authors call at least a few of McCoy's analyses into question because they haven't been as mineralogically metamorphosed as their large grain size would seemingly suggest. In other words, they're large-grained acapulcoites. Or maybe they're transitional. It just depends on how you want to break things up. It's another example of how meteoritics is still a science begging for a better classification system. Do we use the degree of metamorphosis or grain size to determine the class? Who knows... Here are some related docs about the classes and parent body - the first one [ending with 1237.pdf] was the one I noted above: http://www.lpi.usra.edu/meetings/LPSC98/pdf/1237.pdf http://www.lpi.usra.edu/meetings/metsoc97/pdf/5200.pdf http://aaa.wustl.edu/Work/pub_files/acapulcoite_lodranite.html http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6V66-3SVR613-1M_user=10_coverDate=02%2F28%2F1997_rdoc=1_fmt=high_orig=search_sort=d_docanchor=view=c_acct=C50221_version=1_urlVersion=0_userid=10md5=eaea4c9e7fbd30d2ba053bedb0883412 http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060024503_2006090520.pdf http://adsabs.harvard.edu/abs/2009M%26PS...44.1151C http://cat.inist.fr/?aModele=afficheNcpsidt=16823360 http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6WGF-45FCNK6-5_user=10_coverDate=11%2F30%2F2000_rdoc=1_fmt=high_orig=search_sort=d_docanchor=view=c_acct=C50221_version=1_urlVersion=0_userid=10md5=7f6c0ded981b140af26e95baafd2d055 http://www4.nau.edu/meteorite/Meteorite/Book-PrimitiveAchond.html Regards, Jason Utas On Mon, Jul 19, 2010 at 8:15 PM, al mitt alm...@kconline.com wrote: Hi Jeff, Here is what McSween has to say about these two classes. Distinct in appearance but form a coherent group with continuously varying characteristics. They share simular mineralogies, both being composed largely of olivine and pyroxene, with minor plagioclase, iron-nickel metal, and troilite. They have similar oxygen isotopic composition, however they don't define a clear mass-fractionation line. He states that Tim McCoy and colleges shown that the acapuloite-lodranite achondites represent sesidues from varying degrees of partial melting of chondrites, ranging from less than 1% to as great as 25%. It is thought that the lodranite material formed deeper in the parent body, and rising melts generated from them passed through fractures in the overlying acapulites on the way to the surface. An age of 4.56 billion years has been determained for the Acapulco-lodranite parent body from percise lead isotop chronometer. Partial melting occured shortly after accretion. Spectra of acapulcoites are similar to those of ordinary chondrites and lodranites have spectra similar to a variety of S subtype asteroids, suggestions include S(III), S(IV), and S(V) depending on the amount of melt extracted. --AL Mitterling - Original Message - From: Jeff Kuyken To: Meteorite List Sent: Monday, July 19, 2010 7:23 AM Subject: [meteorite-list] Acapulcoite/Lodranite Parent-body Hi all, Does anyone know enough about the Acapulcoite/Lodranite Parent-body to know what the main differences between the classifications are? Is it just the grain size or is there a composition difference etc too? Any paper references would be appreciated. Thanks, Jeff
[meteorite-list] Acapulcoite/Lodranite Parent-body
Hi all, Does anyone know enough about the Acapulcoite/Lodranite Parent-body to know what the main differences between the classifications are? Is it just the grain size or is there a composition difference etc too? Any paper references would be appreciated. Thanks, Jeff __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Acapulcoite/Lodranite Parent-body
Hi Jeff and List, Jeff wrote: Any paper references would be appreciated. Here are a few that might be of help: McCOY T.J. et al. (1992) Petrogenesis of the Lodranite-Acapulcoite parent body (Meteoritics 27-3, 1992, A258). P. Pellas et al. (1994) Thermal Evolution of Acapulcoite-Lodranite Parent Body (Meteoritics 29-4, 1994, A517). McCOY T.J. et al. (1996) A petrologic, chemical, and isotopic study of Monument Draw and comparison with other acapulcoites: Evidence for formation by incipient partial melting (GCA 60, 2681- 2708). TERRIBILINI D. et al. (2000) Evidence for common breakup events of the acapulcoites-lodranites and chondrites (MAPS 35-5, 2000, pp. 1043-1050). FLOSS C. (2000) Complexities on the acapulcoite-lodranite parent body: Evidence from trace element distributions in silicate minerals (MAPS 35-5, 2000, pp. 1073-1085). MITTLEFEHLDT D.W. (2003) Acapulcoite-lodranite clan achondrites: How many parent bodies? (MAPS 38-7, 2003, A095). PATZER A. et al. (2004) Evolution and classification of acapulcoites and lodranites from a chemical point of view (MAPS 39-1, 2004, 61-85). EUGSTER O. et al. (2004) Evidence for a two-layer structure of the Acapulco/Lodranite parent asteroid and 5 ma CRE age of four new acapulcoites (MAPS 39-8, 2004, A038). CROWTHER S.A. et al. (2009) Collisional modification of the acapulcoite/lodranite parent body revealed by the iodine-xenon system in lodranites (MAPS 44-8, 2009, 1151-1159). __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoite/Lodranite Parent-body
Hi Jeff, Here is what McSween has to say about these two classes. Distinct in appearance but form a coherent group with continuously varying characteristics. They share simular mineralogies, both being composed largely of olivine and pyroxene, with minor plagioclase, iron-nickel metal, and troilite. They have similar oxygen isotopic composition, however they don't define a clear mass-fractionation line. He states that Tim McCoy and colleges shown that the acapuloite-lodranite achondites represent sesidues from varying degrees of partial melting of chondrites, ranging from less than 1% to as great as 25%. It is thought that the lodranite material formed deeper in the parent body, and rising melts generated from them passed through fractures in the overlying acapulites on the way to the surface. An age of 4.56 billion years has been determained for the Acapulco-lodranite parent body from percise lead isotop chronometer. Partial melting occured shortly after accretion. Spectra of acapulcoites are similar to those of ordinary chondrites and lodranites have spectra similar to a variety of S subtype asteroids, suggestions include S(III), S(IV), and S(V) depending on the amount of melt extracted. --AL Mitterling - Original Message - From: Jeff Kuyken i...@meteorites.com.au To: Meteorite List meteorite-list@meteoritecentral.com Sent: Monday, July 19, 2010 7:23 AM Subject: [meteorite-list] Acapulcoite/Lodranite Parent-body Hi all, Does anyone know enough about the Acapulcoite/Lodranite Parent-body to know what the main differences between the classifications are? Is it just the grain size or is there a composition difference etc too? Any paper references would be appreciated. Thanks, Jeff __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoite/Lodranite Parent-body
Hi Jeff, Here is what McSween has to say about these two classes. Distinct in appearance but form a coherent group with continuously varying characteristics. They share simular mineralogies, both being composed largely of olivine and pyroxene, with minor plagioclase, iron-nickel metal, and troilite. They have similar oxygen isotopic composition, however they don't define a clear mass-fractionation line. He states that Tim McCoy and colleges shown that the acapuloite-lodranite achondites represent sesidues from varying degrees of partial melting of chondrites, ranging from less than 1% to as great as 25%. It is thought that the lodranite material formed deeper in the parent body, and rising melts generated from them passed through fractures in the overlying acapulites on the way to the surface. An age of 4.56 billion years has been determained for the Acapulco-lodranite parent body from percise lead isotop chronometer. Partial melting occured shortly after accretion. Spectra of acapulcoites are similar to those of ordinary chondrites and lodranites have spectra similar to a variety of S subtype asteroids, suggestions include S(III), S(IV), and S(V) depending on the amount of melt extracted. --AL Mitterling - Original Message - From: Jeff Kuyken To: Meteorite List Sent: Monday, July 19, 2010 7:23 AM Subject: [meteorite-list] Acapulcoite/Lodranite Parent-body Hi all, Does anyone know enough about the Acapulcoite/Lodranite Parent-body to know what the main differences between the classifications are? Is it just the grain size or is there a composition difference etc too? Any paper references would be appreciated. Thanks, Jeff __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Acapulcoite/Lodranite Parent-body
Hello Jeff, There is a great deal of literature online that addresses this topic -- in addition to the McCoy research. The general consensus is that the Acapulcoite/Lodranite parent body was heterogeneously metamorphosed (impact-melted or partially-differentiated, depending on which paper you read) and was then largely broken up by an impact(s) nearly 4.6 billion years ago. Lodranites and Acapulcoites have been differentiated in the past almost solely based on structural observations/grain size. The trouble is that the cutoff between the two has traditionally been determined by grain size and is not clearly defined - check out the discussion section of this paper (also in the list of sources below) for a good summary: http://www.lpi.usra.edu/meetings/LPSC98/pdf/1237.pdf Here's the meat of it: Acapulcoites experienced only low degrees of Fe,Ni- FeS cotectic melting and have maintained essentially chondritic troilite and plagioclase abundances, whereas lodranites experienced higher degrees of melting that included partial silicate melting with subsequent loss of troilite and/or plagioclase fractions. If you keep reading through the discussion, you'll find that the authors call at least a few of McCoy's analyses into question because they haven't been as mineralogically metamorphosed as their large grain size would seemingly suggest. In other words, they're large-grained acapulcoites. Or maybe they're transitional. It just depends on how you want to break things up. It's another example of how meteoritics is still a science begging for a better classification system. Do we use the degree of metamorphosis or grain size to determine the class? Who knows... Here are some related docs about the classes and parent body - the first one [ending with 1237.pdf] was the one I noted above: http://www.lpi.usra.edu/meetings/LPSC98/pdf/1237.pdf http://www.lpi.usra.edu/meetings/metsoc97/pdf/5200.pdf http://aaa.wustl.edu/Work/pub_files/acapulcoite_lodranite.html http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6V66-3SVR613-1M_user=10_coverDate=02%2F28%2F1997_rdoc=1_fmt=high_orig=search_sort=d_docanchor=view=c_acct=C50221_version=1_urlVersion=0_userid=10md5=eaea4c9e7fbd30d2ba053bedb0883412 http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060024503_2006090520.pdf http://adsabs.harvard.edu/abs/2009M%26PS...44.1151C http://cat.inist.fr/?aModele=afficheNcpsidt=16823360 http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6WGF-45FCNK6-5_user=10_coverDate=11%2F30%2F2000_rdoc=1_fmt=high_orig=search_sort=d_docanchor=view=c_acct=C50221_version=1_urlVersion=0_userid=10md5=7f6c0ded981b140af26e95baafd2d055 http://www4.nau.edu/meteorite/Meteorite/Book-PrimitiveAchond.html Regards, Jason Utas On Mon, Jul 19, 2010 at 8:15 PM, al mitt alm...@kconline.com wrote: Hi Jeff, Here is what McSween has to say about these two classes. Distinct in appearance but form a coherent group with continuously varying characteristics. They share simular mineralogies, both being composed largely of olivine and pyroxene, with minor plagioclase, iron-nickel metal, and troilite. They have similar oxygen isotopic composition, however they don't define a clear mass-fractionation line. He states that Tim McCoy and colleges shown that the acapuloite-lodranite achondites represent sesidues from varying degrees of partial melting of chondrites, ranging from less than 1% to as great as 25%. It is thought that the lodranite material formed deeper in the parent body, and rising melts generated from them passed through fractures in the overlying acapulites on the way to the surface. An age of 4.56 billion years has been determained for the Acapulco-lodranite parent body from percise lead isotop chronometer. Partial melting occured shortly after accretion. Spectra of acapulcoites are similar to those of ordinary chondrites and lodranites have spectra similar to a variety of S subtype asteroids, suggestions include S(III), S(IV), and S(V) depending on the amount of melt extracted. --AL Mitterling - Original Message - From: Jeff Kuyken To: Meteorite List Sent: Monday, July 19, 2010 7:23 AM Subject: [meteorite-list] Acapulcoite/Lodranite Parent-body Hi all, Does anyone know enough about the Acapulcoite/Lodranite Parent-body to know what the main differences between the classifications are? Is it just the grain size or is there a composition difference etc too? Any paper references would be appreciated. Thanks, Jeff __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http
