Several people have informally suggested a two-tier system. It would work something like this. For example, on a metamorphic scale, Semarkona is type 3.00, but on an independent aqueous alteration scale it would be 2.8 or 2.9. Similarly, CR chondrites could all be 3.0 on a metamorphic scale, but range from 2.0 to 2.8 on an aqueous alteration scale. This is admittedly cumbersome, but it would be fairly useful. However, there are some carbonaceous chondrites that seem to have been altered and then metamorphosed; they would be hard to deal with. Also, if a rock is hydrothermally altered (i.e., subjected to metamorphic heating and aqueous alteration at the same time), that would also not be covered by such a scheme. Fitting complex rocks into classificatory straightjackets might obscure more than it reveals. Alan
Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 office phone: 310-825-3202 fax: 310-206-3051 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html -----Original Message----- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Mark Bowling Sent: Friday, April 11, 2014 10:01 PM To: meteorite-list@meteoritecentral.com Subject: Re: [meteorite-list] petrological type Are there any better alternatives that could someday replace the current one, and do you have any references/links for them? Thanks, Mark ________________________________ From: Jeff Grossman <jngross...@gmail.com> To: meteorite-list@meteoritecentral.com Sent: Friday, April 11, 2014 5:22 PM Subject: Re: [meteorite-list] petrological type Answer: you can't. The classification scheme is lousy. Jeff On 4/11/2014 1:21 PM, Michael Mulgrew wrote: > Two sequences, one for aqueous alteration and one for thermal > metamorphism (http://www.meteoritemarket.com/PetTypeGroup.jpg). Makes > one wonder how we would classify a meteorite that is both thermally > and aqueously altered... > > > Michael in so. Cal. > IMCA 3963 > > On Fri, Apr 11, 2014 at 10:14 AM, Francesco Moser <coj...@tiscali.it> wrote: >> Hello, I have a question about chondrites' petrological type number assigned >> after the letters (like H, L, CM or CR ...). >> I have just read something in internet but I think I have misunderstood >> something. >> >> Are the numbers from 1 to 7 in sequence or there are two different >> sequences: 1 to 2 - 3 to 7 ?? >> 1 to 2 is for the aqueous alteration degree in carbonaceous chodrites (1 >> high degree, 2 low degree) >> 3 to 7 is for thermal metamorphism degree? >> >> >> Thanks a lot >> >> Ciao >> >> <x>x<x>x<x> >> Francesco >> >> >> ______________________________________________ >> >> Visit the Archives at http://www.meteorite-list-archives.com/ >> Meteorite-list mailing list >> Meteorite-list@meteoritecentral.com >> http://six.pairlist.net/mailman/listinfo/meteorite-list > ______________________________________________ > > Visit the Archives at http://www.meteorite-list-archives.com/ > Meteorite-list mailing list > Meteorite-list@meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Visit the Archives at http://www.meteorite-list-archives.com/ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list