[meteorite-list] Chondritic parent bodies: Clarification

[Jeff Grossman]

Yes, it's the same idea.  Usually, the L(LL) notation is used for highly 
unequilibrated (petrologic type type 3.0-3.4)  ordinary chondrites.  
I've been studying these things for decades and I still don't know of 
any way to distinguish a low type L from LL chondrite using an optical 
microscope, SEM, or electron microprobe.  Even O isotopes don't always 
tell you.  You have to do bulk chemistry, which is rarely done anymore 
on OCs, and certainly not in the initial classification. 

Take, for example, one that I've worked on: NWA 1756.  It is classified 
as LL3.10.  In my opinion it could just as easily be an L3.10, as nobody 
(to my knowledge) has done the chemistry to provide a definitive answer. 
To me, such meteorites are all uncertain.  If I was the original 
classifier of this meteorite and I thought the properties looked more 
LL-like, I'd have called it LL(L).  If I was totally unsure, I'd have 
called it L/LL. The 3.10 pet-type, on the other hand, is independent of 
chemical group.

This brings up one last issue.  If NWA 1756 could be called L/LL because 
a classifier cannot tell which it is, but Bjurböle is called L/LL 
because it is truly intermediate, then this is two completely different 
uses of the same symbol.  John Wasson and I want to propose a new 
nomenclature: Bjurböle should be changed to L^LL4, where the caret 
indicates known intermediate properties.  One day we'll get around to 
proposing it.

Jeff G.

Jeff Kuyken wrote:
> And there are also quite a few with L(LL) for example. I always 
> thought this was the classifier saying they were not totally sure for 
> some reason but their 'best guess' was the first class outside of the 
> brackets. Is this similar to L/LL?
>
> Cheers,
>
> Jeff
>
>
> ----- Original Message ----- From: <bernd.pauli at paulinet.de>
> To: <Meteorite-list at meteoritecentral.com>
> Sent: Thursday, September 10, 2009 6:22 AM
> Subject: [meteorite-list] Chondritic parent bodies: Clarification
>
>
>> Tracy writes:
>>
>> "Oog. I agree with Bernd; classification is currently a mess."
>>
>> Sorry, I forgot the inverted commas => " ... "
>>
>> Those were Jeff's remarks / comments!
>>
>> Bernd
>>
>> ______________________________________________
>> http://www.meteoritecentral.com
>> Meteorite-list mailing list
>> Meteorite-list at meteoritecentral.com
>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>>
>>
>
> ______________________________________________
> http://www.meteoritecentral.com
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>


-- 
Dr. Jeffrey N. Grossman       phone: (703) 648-6184
US Geological Survey          fax:   (703) 648-6383
954 National Center
Reston, VA 20192, USA