[meteorite-list] H2 or L2 CLASS METEORITES

From: tett <tett_at_meteoritecentral.com>
Date: Thu, 29 Mar 2007 21:31:42 -0400
Message-ID: <002101c7726b$2c852960$6400a8c0_at_tettenborn>

Doug,

Does petrologic grade 3, in essence, mean little to no thermal alteration?
If so, then there can not be a type 2 even with a nice heat sink to protect
these primordial chondrules. In fact, McSween's chart on pg 63 2nd ed.
shows type 3 as neither aqueous altered or thermally altered. However, he
does mention that these classifications are simplifications and intended to
represent a range of alteration. Why we now have LL3.7's etc.

Although I have not found this plainly stated, I believe the intent of the
classification system was that H3.0 or L3.0 or LL3.0 are thermally unaltered
and hence have pristine baby fresh chondrules.

The parent bodies for the carbonaceous chondrites did not experience the
same temperatures leading to thermal alteration of their chondrules. At
least, I guess this is so.

Cheers,

Mike Tettenborn


----- Original Message -----
From: "MexicoDoug" <MexicoDoug at aim.com>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Thursday, March 29, 2007 9:05 PM
Subject: Re: [meteorite-list] H2 or L2 CLASS METEORITES


> "I was thinking about this today and I have not had time to research it."
>
> Hello Steve,
>
> I hope you can do some research sometime, Steve. As "H" and "L" are
> thought
> to be two unique and real parent bodies, your question can be stated
> alternately:
>
> "Were there any places on the H parent body or the L parent body that did
> not experience the thermally-induced alteration characteristic of
> unequilibrated chondrites "3", and if so, did any residue from them reach
> earth and drop meteorites?"
>
> I think the answer is "no". Harry McSween explains that on these parent
> bodies, especially with reference to the onion-skin model of asteroids,
> the
> incubation caused by radioactive disintegration warmed the whole of the
> parent body uniformly enough to cook all of our H- and L-chondrites enough
> according to 'current' understanding. But that doesn't mean chance could
> have thermally isolated or provided a shady heat sink somewhere on the
> surface where the legendary H2 or L2 could have been protected from its
> mother planetoid.
>
> Carbonaceous chondrites meteorites show "2" and essentially "1" not
> because
> they were heated, but rather because of their setting of primordial
> material, like celestial cementing that formed them, altered them to
> varying
> degrees with water, but not the heat on the H- and L- assumed to be larger
> parent bodies.
>
> Note since there are just two parent bodies here, it is easy to write off
> the possibility of H2 and L2 just by saying, these bodies were simply too
> warm for this to occur. If you calculate an asteroid diameter to explain
> the H3-6 distributions we know, for example, you can say how big the
> parent
> body was, and once you say how big it was, you can argue by its thermal
> properties how it all got warm and sufficiently metamorphic.
>
> But this is all still conjecture. The University of Chicago is always in
> need of a few good men!! Go Steve!!
>
> Best Wishes and Best Health,
> Doug
>
> ----- Original Message -----
> From: "steve arnold" <stevenarnold60120 at yahoo.com>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Thursday, March 29, 2007 5:57 PM
> Subject: [meteorite-list] H2 or L2 CLASS METEORITES
>
>
>> Hi list.I was thinking about this today and I have not
>> had time to research it.Are there any H2 or L2 class
>> meteorites that have been classified?This is a real
>> must thread for me.Any help would be welcome.
>>
>>
>>
>>
>> steve arnold,chicago
>>
>> Steve R.Arnold,chicago,Ill,Usa!!
>> Collecting Meteorites since 06/19/1999!!
>> www.chicagometeorites.net
>> Ebay I.D. Illinoismeteorites
>>
>>
>>
>>
>>
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Received on Thu 29 Mar 2007 09:31:42 PM PDT