[meteorite-list] H2 or L2 CLASS METEORITES

From: tett <tett_at_meteoritecentral.com>
Date: Thu, 29 Mar 2007 22:06:33 -0400
Message-ID: <004801c77270$0a658f00$6400a8c0_at_tettenborn>

Doug,

I think in this debate there is no clear winner. You did yield but perhaps
too easily. Like you said, a chondrite could be found that is even more
pristine than the current most pristine LL3.0 and then, besides sell it for
$1000/gram, what do we do?

The convention system is a little hard to understand and could be simplified
but I kinda like it the way it is.

As for the 4 billion year old ausie rocks, my 4.03 billion year old CANADIAN
acasta gneiss is still the oldest found terrestrial rock to date. My little
25 gram chip sits contently amongst a pair a 7 year old Guatemalan lava
rocks from Mount Pacaya.

Cheers,

Mike


----- Original Message -----
From: "MexicoDoug" <MexicoDoug at aim.com>
To: "tett" <tett at rogers.com>; "Meteorite Mailing List"
<meteorite-list at meteoritecentral.com>
Sent: Thursday, March 29, 2007 9:43 PM
Subject: Re: [meteorite-list] H2 or L2 CLASS METEORITES


> Hi Mike,
>
> In light of Jeff's post I'd tend to yield if I were in an argument and
> just
> agree. But if the purpose is to get a feel for what is happening and why,
> it's more fun to keep these ideas alive.
>
> Scientists can make conventions, and it is very hard to keep conventions
> written in stone. Until a new stone causing them to go back to the
> drawing
> board. The purpose of my post was to complement your ideas and get an
> understanding of the processes. If the scientists want to define 3.0 as
> the
> lowest and take into consideration a well thought out scheme, that's fine.
> Then, someone, somewhere, will come up with something that doesn't fit
> some
> class and it will be worth $1000/gram and have everyone buzzing.
>
> Yielding with a good fight, and remembering the 4 billion year old rocks
> found in Australia,
> Doug
>
> PS as to McSween's chart, I think that is a red herring. After all, if
> you
> were to interpret it literally as you do, type "I" carbonaceous would be
> more altered by water than type "2"!!
>
> ----- Original Message -----
> From: "tett" <tett at rogers.com>
> To: "MexicoDoug" <MexicoDoug at aim.com>; "Meteorite Mailing List"
> <meteorite-list at meteoritecentral.com>
> Sent: Thursday, March 29, 2007 7:31 PM
> Subject: Re: [meteorite-list] H2 or L2 CLASS METEORITES
>
>
>> 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
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
> ____________________________________________________________________________
>> > ________
>> >> The fish are biting.
>> >> Get more visitors on your site using Yahoo! Search Marketing.
>> >> http://searchmarketing.yahoo.com/arp/sponsoredsearch_v2.php
>> >> ______________________________________________
>> >> Meteorite-list mailing list
>> >> Meteorite-list at meteoritecentral.com
>> >> http://six.pairlist.net/mailman/listinfo/meteorite-list
>> >>
>> >
>> > ______________________________________________
>> > Meteorite-list mailing list
>> > Meteorite-list at meteoritecentral.com
>> > http://six.pairlist.net/mailman/listinfo/meteorite-list
>> >
>>
>>
>
>
Received on Thu 29 Mar 2007 10:06:33 PM PDT