AW: WG: [meteorite-list] Classification question

Jörn Koblitz koblitz at microfab.de
Thu May 13 02:31:11 EDT 2004 

Correct. It simply mean that no finer classification has been done. It's just a bit more work to get the subtype classification. A 3.0 is actually the most primitive, most unequilibrated and rarest type of unequilibrated ordinary chondrite. 

BTW: A petrologic type 2 has never been assigned to any ordinary chondrite. Only to carbonaceous chondrites.

Jörn


> -----Ursprüngliche Nachricht-----
> Von: Nicholas Gessler [mailto:gessler at ucla.edu]
> Gesendet: Donnerstag, 13. Mai 2004 02:30
> An: Jörn Koblitz; meteorite-list at meteoritecentral.com
> Betreff: Re: WG: [meteorite-list] Classification question
> 
> 
> While we're at it, what's the difference between a "3" and a "3.0?"
> Does a "3" imply that no one made any finer discrimination?
> Or does a "3" imply that it's really a "3.0?"
> Cheers,
> Nick
> 
> At 08:23 AM 4/14/2004, Jörn Koblitz wrote:
> >Dear Pierre,
> >
> > > I've got a (stupid ?) question about the classification of
> > > the chondrites.
> > >
> > > What is the difference between this kind of classification :
> > > For example L3.6, L3-6 or H5/6
> > >
> > > Is the sign "-" the same as "/" or "." in this case  ?
> >
> >Regarding the use of hyphens and slashes, see the postings 
> to the list of 
> >March 19 to 23 (pasted below).
> >
> >The use of "." in the classification (e.g. L3.6) is used in 
> case that a 
> >petrologic SUBtype has been obtained, either by measuring 
> the induced 
> >thermoluminescence (TL) or by calculation of the percentage 
> mean deviation 
> >(PMD) of the fayalite and ferrosilite contents of olivine 
> and pyroxene, 
> >respectively, measured by microprobe (EPMA). The subtype is 
> just a finer 
> >subdivision and is only used for unequilibrated (i.e. type 
> 3) chondrites. 
> >It is a scale for the amount of thermal metamorphism a chondrite has 
> >experiences since its accretion. In this respect, a 3.0 
> indicate the least 
> >metamorphosed (or most primitive / less heated) type 3 
> chondrite. On the 
> >other hand, a type 3.9 chondrite is almost chemically 
> equilibrated like 
> >type 4 and higher, as it has experienced considerable 
> heating (e.g. by 
> >impact shock) during its lifetime on the parent-body 
> (planetesimal or 
> >asteroid).
> >
> >Hope this answers your question.
> >
> >Best regards,
> >
> >Joern
> >
> >_____________________________________________________________
> __________________
> >Joern Koblitz
> >MetBase Editor
> >The MetBase Library of Meteoritics and Planetary Sciences
> >Benquestrasse 27
> >D-28209 Bremen, Germany
> >phone: +49 421 24 100 24
> >fax: +49 421 24 100 99
> >email: info at metbase.de
> >_____________________________________________________________
> __________________
> >
> >
> >
> >
> >
> >
> >
> >
> >Hello John, David and Bernd,
> >
> >Sorry for my late reply - I'm not online on weekends.
> >
> >You are right, it's a messy situation with the use of 
> slashes "/" and 
> >hyphens "-" and as Jeff outlined long time ago, it actually 
> depends on the 
> >research group who does the classification. With MetBase, I 
> stick to the 
> >presently preferred rules that "/" indicates a transitional 
> type and "-" a 
> >breccia. However, as complicated as it could be, imagine that a 
> >transitional group like H/L contains clasts of different 
> petrologic types, 
> >e.g. 4 and 6: should it then be designated H/L4-6 or 
> (H/L)4-6 or H4-6/L4-6?
> >Regarding the transitional petrologic type designations, 
> e.g. H5/6: beware 
> >that there is always a personal bias by the person who did the 
> >classifications: one researcher will classify an H chondrite 
> H5, another 
> >researcher the same chondrite H6 and a third person would 
> give it H5/6: 
> >there is always an uncertainty of +/- 0.5 for equilibrated ordinary 
> >chondrites. That's why some researchers think that it is always 
> >appropriate to assign straight numbers and to prevent transitional 
> >numbers, which is rather a sign of shakiness. Regarding the use of 
> >parentheses, e.g. "LL/(L)3" or "LL(L)3": this problem is 
> rather restricted 
> >to very unequilibrated chondrites as Jeff pointed out. Since highly 
> >unequilibrated chondrites show large variations in mineral 
> chemistry (e.g. 
> >wide ranges of olivine, pyroxene or metal compositions), one 
> has to do a 
> >large number of microprobe and (oxygen) isotopic 
> measurements to gain 
> >certainty on the classification. This is very time-consuming and 
> >expensive. Further, many hot-desert finds are higly 
> weathered which makes 
> >it difficult to classify them based on chemical compositions 
> (terrestrial 
> >contamination).
> >
> >David: Regarding the differences in designations beween Met. 
> Bulletin and 
> >MetBase, I have to check the literature sources of the 
> MetBase information 
> >and let you know lateron if I can clearify.
> >
> >Joern
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: j.divelbiss at att.net [mailto:j.divelbiss at att.net]
> > > Gesendet: Freitag, 19. März 2004 22:27
> > > An: bernd.pauli at paulinet.de
> > > Cc: dgweir at earthlink.net; Jörn Koblitz;
> > > meteorite-list at meteoritecentral.com
> > > Betreff: Re: [meteorite-list] Hyphens / Slashes
> > >
> > >
> > > Bernd. Dave, Joern and others,
> > >
> > > Bernd, thanx for the previously submitted info from Jeff on
> > > slashes and dashes.
> > >
> > > That should certainly clear it up the confusion, right Dave. :)
> > >
> > > John
> > >
> > > BTW: Joern...in all seriousness I really appreciate you
> > > responding to this thread.
> > >
> > >
> > > > > For chondrite groups, petrologic types, shock stages, and
> > > weathering
> > > > > grades, slashes (e.g., H5/6) indicate transitional
> > > assignments. Hyphens
> > > > > in petrologic type assignments for chondrites (e.g.,
> > > H5-6) indicate the
> > > > > range of types observed in breccias. Group names such as
> > > "L(LL)" indicate
> > > > > uncertain assignments, with the less probable group in
> > > parentheses.
> > > >
> > > > Hello All,
> > > >
> > > > I was waiting for Jeff Grossman to chime in here, because
> > > > on Monday, 07 Sep 1998, Jeff wrote to this to the List 
> (excerpts):
> > > >
> > > > Right now we have a literature polluted with this and other
> > > nomenclatures
> > > > (like using a "/" instead of a "-" for the same thing), and
> > > the community has
> > > > no way of looking at a catalog and knowing what's what. The
> > > Meteorite
> > > > Nomenclature committee has no jurisdiction over meteorite
> > > classification;
> > > > it just oversees meteorite names. It's just a mess.
> > > >
> > > > There is NO convention for naming brecciated chondrites.
> > > Many, including the
> > > > group at Muenster, like to use a slash to separate
> > > components of a breccia.
> > > > However, nobody has ever written a paper on the subject,
> > > and the rules are up
> > > > for grabs. I happen to be of the opinion that the slash is
> > > ridiculous for many
> > > > reasons,
> > > > including the one brought up here: we will always need to
> > > be reclassifying
> > > > breccias
> > > > whenever somebody finds a new lithology among the clasts.
> > > This is not feasible.
> > > >
> > > > These parentheses are used by some researchers when they
> > > cannot determine with
> > > > certainty the group assignment of a meteorite. L(LL)3 means
> > > that they lean
> > > > towards
> > > > L3, but it could be an LL3. Indeed, it is very difficult to
> > > differentiate
> > > > between L3 and LL3
> > > > chondrites, as they may have similar sized chondrules,
> > > similar metallography,
> > > > similar
> > > > silicate compositions (i.e., highly heterogeneous), and
> > > even oxygen isotope
> > > > compositions
> > > > and trace elements cannot always resolve them well.  Even
> > > some of the most
> > > > famous, best
> > > > studied meteorites have been given various classifications
> > > in different parts of
> > > > the literature
> > > > (e.g., Tieschitz, Krymka, Bishunpur).
> > > >
> > > > If any meteorite has been called "LL/(L)3", I have no clue
> > > what this means.
> > > >
> > > >
> > > > To: dgweir at earthlink.net
> > > >     koblitz at microfab.de
> > > > Cc: meteorite-list at meteoritecentral.com
> > > >
> > > >
> > > > ______________________________________________
> > > > Meteorite-list mailing list
> > > > Meteorite-list at meteoritecentral.com
> > > > http://www.pairlist.net/mailman/listinfo/meteorite-list
> > >
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: Pierre-Marie PELE [mailto:pierre.pele at voila.fr]
> > > Gesendet: Mittwoch, 14. April 2004 08:15
> > > An: meteorite-list at meteoritecentral.com
> > > Betreff: [meteorite-list] Classification question
> > >
> > >
> > > Hello to the List !
> > >
> > > I've got a (stupid ?) question about the classification of
> > > the chondrites.
> > >
> > > What is the difference between this kind of classification :
> > > For example L3.6, L3-6 or H5/6
> > >
> > > Is the sign "-" the same as "/" or "." in this case  ?
> > >
> > > Thanks a lot,
> > >
> > > Pierre
> > > ------------------------------------------
> > >
> > > Faites un voeu et puis Voila ! www.voila.fr
> > >
> > >
> > >
> > > ______________________________________________
> > > Meteorite-list mailing list
> > > Meteorite-list at meteoritecentral.com
> > > http://www.pairlist.net/mailman/listinfo/meteorite-list
> > >
> >
> >______________________________________________
> >Meteorite-list mailing list
> >Meteorite-list at meteoritecentral.com
> >http://www.pairlist.net/mailman/listinfo/meteorite-list
> 
> 
>

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