[meteorite-list] Ordinary chondrites - decimal metamorphic grade question

From: Darryl Pitt <darryl_at_meteoritecentral.com>
Date: Wed, 16 Dec 2009 12:12:36 -0500
Message-ID: <DE614257-3EC0-4374-B8F9-BE908F5630EC_at_dof3.com>

Hey Matt,

5717 is not an LL, one of the lithologies has more in common with an
H---except that it has almost no metal.
The topic raised is indeed very, very interesting. Best/ d,


On Dec 16, 2009, at 11:04 AM, Matt Morgan wrote:

> Since Darryl brought up his incredible LL3.05, I have to ask how
> does/can one classify the metamorphic grade to the to the tenths or
> now the hundredths of a decimal? I have had some tell me this is
> subjective and others say you need specialized equipment. Please,
> any researchers, explain.
>
> Darryl-
> I don't mean to pick on your material, but it is a question that has
> been nagging me for sometime and you stirred my brain!
>
> Thanks in advance!
> Matt
> ----------------------
> Matt Morgan
> Mile High Meteorites
> http://www.mhmeteorites.com
> P.O. Box 151293
> Lakewood, CO 80215 USA
>
> -----Original Message-----
> From: Darryl Pitt <darryl at dof3.com>
> Date: Wed, 16 Dec 2009 10:35:38
> To: Jeff Grossman<jgrossman at usgs.gov>
> Cc: <Meteorite-list at meteoritecentral.com>
> Subject: Re: [meteorite-list] Ordinary chondrites - rarest to the most
> common classes
>
>
>
> Get ready for NWA 5717.....
>
> Initially "anomalous," the classification had to be changed to
> "ungrouped" as it was too difficult to determine what it was anomalous
> to. 3.05 subtype. More to follow....
>
>
>
>
>
> On Dec 16, 2009, at 10:26 AM, Jeff Grossman wrote:
>
>> At 09:27 AM 12/16/2009, Chladnis Heirs wrote:
>>> Indeed,
>>>
>>> it's for the first time, that I read that R-chondrites are included
>>> in the
>>> OC-group. If so, why exactly them and not the K-chondrites, the
>>> Carbonaceous
>>> from grade 3-6, the ungrouped and the enstatite chondrites too?
>>
>> I didn't say they ARE included in the OCs... I said that I thought
>> they should be. As far as I know, I am alone in this opinion. There
>> are only two Kakangari-like chondrites, and I am not prepared to put
>> them anywhere. I'm not sure what the rest of the question means,
>> but many ungrouped chondrites can be and are associated with a major
>> class, as in "ungrouped carbonaceous chondrite".
>>
>> jeff
>>
>>
>>>
>>>> valuable type of OC from a
>>>> scientific perspective is petrologic type 3.00-3.01
>>>
>>> Where one has to say, that it's maybe too early to say that,
>>> Because the classification with decimal places, (even with two!),
>>> is a
>>> relatively new occurrence - most classifiers seems still to prefer
>>> to use a
>>> simple "3" - so that in case, there are still a lot known type-3ers
>>> awaiting
>>> to be revisited regarding the degree of their (un)equilibration.
>>>
>>> But I agree - "Ordinary" is a somewhat misleading term,
>>> - as the ordinary chondrites have told us most about the origin and
>>> formation of the solar system, the planets and ourselves, more than
>>> any iron
>>> or any lunar rock!
>>>
>>> Keep that always in mind, if you are tempted, now in the end of the
>>> desert-era and the decreed end of meteorite finding in so many
>>> countries,
>>> with all their weird and fancy exotic types, to wrinkle your nose
>>> about the
>>> "ugly" ordinary 25$-a-kilo-chunk from NWA-wonderland!
>>> Rare as brilliants they are - and they were our beginnings!
>>>
>>> Happy holidays to all!
>>> Martin
>>>
>>>
>>> -----Urspr?ngliche Nachricht-----
>>> Von: meteorite-list-bounces at meteoritecentral.com
>>> [mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von
>>> Jeff
>>> Grossman
>>> Gesendet: Mittwoch, 16. Dezember 2009 11:33
>>> An: Meteorite-list
>>> Betreff: Re: [meteorite-list] Ordinary chondrites - rarest to the
>>> most
>>> common classes
>>>
>>> I agree with Doug... the rarest and most valuable type of OC from a
>>> scientific perspective is petrologic type 3.00-3.01, from any of the
>>> chemical groups. Only one is known... Semarkona. If we take a more
>>> expansive definition of "ordinary chondrite" than most of my rather
>>> conservative colleagues are normally willing to accept, I would say
>>> that
>>> the rarest group of OCs is the R chondrites (only ~100 are known and
>>> many of those are paired). In addition, a number of unique
>>> ungrouped
>>> meteorites are OC-like. But again, I don't know of any colleagues
>>> who
>>> agree with me that R chondrites are in the OC class. [I would say
>>> that
>>> the OC class has two clans, the H-L-LL clan and the R clan].
>>>
>>> Jeff
>>>
>>> Mexicodoug wrote:
>>>> Hi Melanie and thanks for the enthusiasm you add to the list ...
>>>>
>>>> Here's a high to low sorting of the "ordinary chondrites", for over
>>>> 32,000 meteorites:
>>>>
>>>> 22.0% L6 ("most common")
>>>> 19.9% H5
>>>> 12.9% L5
>>>> 12.3% H4
>>>> 11.5% H6
>>>> 7.8% LL5
>>>> 4.2% LL6
>>>> 3.3% L4
>>>> 2.2% H3
>>>> 2.0% L3
>>>> 0.8% LL4
>>>> 0.8% LL3
>>>> 0.1% L7
>>>> 0.1% LL7
>>>> 0.03% H7 ("least common")
>>>>
>>>> But this "common" and "rare" is a misleading label. That is a
>>> harder
>>>> question if you look too closely at the deails and consider
>>>> inhomogeneous and brecciated ordinary chondrites. That can all
>>> become
>>>> somewhat unique if you ask the right person. Then there are the
>>> motley
>>>> crew of ungrouped ordinary chondrites where it is hard to
>>> generalize.
>>>> Some may be a weak classification while others might truly be weird
>>>> ("rare").
>>>>
>>>> Just a few notes: the H7, L7, LL7 types are not widely used in the
>>>> literature and border on impact melts, so I'd take them with a
>>> grain
>>>> of salt unless someone goes postal on me in which case they are
>>> right
>>>> in whatever they say. The way I listed these, the meteorites are
>>>> counted by the lowest number and won't show up in the higher
>>> thermal
>>>> (metamorphosed) levels. In other words, for example, an LL3.8-6 is
>>>> counted with the LL3's.
>>>>
>>>> If you have a special meteorite, it can sometimes be a "rarer"
>>> type if
>>>> you start to split hairs, like H3.8 instead of just grouping it
>>> within
>>>> the H3's, but there is some degree of arbitrariness to this. The
>>>> tendency is that more virgin Solar system stuff (closer and closer
>>>> 3.00) is more special and like a holy grail ("rare" in a sense) to
>>>> some who study that - since it is more representative of the
>>> original
>>>> material before water and heat were added and did their thing. From
>>>> hat we can try to get the proof we need to work out early formation
>>>> processes and theorize on the related dynamics happening. By this
>>>> logic, and considering it is a very studied meteorite, the precious
>>>> meteorite SEMARKONA (LL3.00 or is it 3.01 :-)), a witnessed fall
>>> from
>>>> India, is rather unique being the only one with that 3.00
>>>> classification, which makes it super intact since formation and
>>>> especially interesting to experts, and most notably Dr. Jeff
>>> Grossman
>>>> who reviewed and updated its classification upon careful study.
>>>>
>>>> By another measure, the "common" ordinary chondrite, L5, Canadian
>>>> witnessed fall, VILNA, is one of those very few special meteorites
>>>> that was imaged during atmospheric entry and a precise orbit was
>>>> determined. It was not too far from Buzzard Coulee, and what
>>> makes it
>>>> even more special is that it was classified from a (although
>>> witnesses
>>>> heard pieces whizzing around) 94 milligram fragment with fusion
>>> crust.
>>>> The only other specimen found was a 48 milligram piece! This
>>> becomes a
>>>> wild anecdote of a meteorite tale when one considers that the
>>> bolide
>>>> passed directly over the only camera recording the sky for 500
>>> miles
>>>> (over 800 km) and headed for the newly constructed and world's only
>>>> UFO landing site which had been built for the Canadian Centennial
>>>> exposition in St. Paul, Alberta, where it showered sparks
>>>> ("retro-rockets" to some folks). In case you wondered, I believe
>>> the
>>>> Japanese classified on Antarctic meteorite with 10 milligrams, if
>>> you
>>>> can believe that!
>>>>
>>>> So what actually makes a meteorite rare can turn into a matter of
>>>> semantics and who you ask. Even the scale of 3 to 6 (or 7) is
>>> somewhat
>>>> arbitrary and just looks for convenient thermally changed cairns
>>> along
>>>> the path toward melting. So if we went the other way, if H, L,
>>> and LL
>>>> correspond to only three parent bodies, the frequency of the types
>>>> follows:
>>>>
>>>> H 45.0%
>>>> L 40.6%
>>>> LL 14.3%
>>>>
>>>> Hope this helps a little with that general question!
>>>>
>>>> Kind wishes,
>>>> Doug
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Melanie Matthews <miss_meteorite at yahoo.ca>
>>>> To: meteorite-list at meteoritecentral.com
>>>> Sent: Tue, Dec 15, 2009 7:01 am
>>>> Subject: [meteorite-list] Ordinary chondrites - rarest to the most
>>>> common classes
>>>>
>>>>
>>>> G'mornin' listites,,
>>>> What is the least common type of ordinary chondrite, as well as the
>>>> most common?
>>>>
>>>>
>>>>
>>>> Thanks
>>>> -----------
>>>> Melanie
>>>> IMCA: 2975
>>>> eBay: metmel2775
>>>> Known on SkyRock Cafe as SpaceCollector09
>>>>
>>>> Unclassified meteorites are like a box of chocolates... you never
>>> know
>>>> what
>>>> you're gonna get!
>>>>
>>>>
>>>>
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>>>
>>>
>>> --
>>> Dr. Jeffrey N. Grossman phone: (703) 648-6184
>>> US Geological Survey fax: (703) 648-6383
>>> 954 National Center
>>> Reston, VA 20192, USA
>>>
>>>
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>>
>> Dr. Jeffrey N. Grossman phone: (703) 648-6184
>> US Geological Survey fax: (703) 648-6383
>> 954 National Center
>> Reston, VA 20192, USA
>>
>>
>> ______________________________________________
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>
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Received on Wed 16 Dec 2009 12:12:36 PM PST