[meteorite-list] Primitive Achondrite Question

From: Ruben Garcia <mrmeteorite_at_meteoritecentral.com>
Date: Mon, 5 Dec 2011 21:02:31 -0700
Message-ID: <CAH3bqe+XOFMGcF7aqJFn6T7O47nC4EQuRM7N3nmpv0Q6qW1UxQ_at_mail.gmail.com>

Hi all,

Thanks Jeff and Doug.

Sorry Ted, I've been out of town and haven't followed any other
similar conversation so I wasn't aware it was a touchy subject.

However, since we're here....... I still have one last question -
actually I need advice on what to call these slices when I advertise
them for sale.

Jeff says (and Ted seems to agree) "I think the Bunch et al.'s
conclusion that NWA 3100 is
a CR6 is the best we have right now, but I think you still have to
think of this as preliminary.

I bought this collection to sell so.... Can I call it a CR6 when I
sell it or should I call it a primitive achondrite?




On Mon, Dec 5, 2011 at 8:45 PM, John Lutzon <jl at hc.fdn.com> wrote:
>
> Thank you Jeff,
>
> Believe it or not, you enlightened my small small knowledge about this.
>
> Further sales of "metachondrite" terminology is hereby suspended until Ted's
> posterier heals.
>
> Sorry, just had to, John.
>
> ----- Original Message ----- From: "Ted Bunch" <tbear1 at cableone.net>
> To: "Jeff Grossman" <jngrossman at gmail.com>;
> <meteorite-list at meteoritecentral.com>
> Sent: Monday, December 05, 2011 10:00 PM
> Subject: Re: [meteorite-list] Primitive Achondrite Question
>
>
>
>> Well stated Jeff and I agree! Thank you. There is the thing about
>> "metachondrite" terminology, but we shall leave this "dead horse" alone
>> for
>> the time being.
>>
>> Two of these unremitting classification issues in 3 days is much too much
>> for me in one week, especially when my butt is tied to both of them.
>>
>> Ted
>>
>>
>> On 12/5/11 7:02 PM, "Jeff Grossman" <jngrossman at gmail.com> wrote:
>>
>>> Type 7 is considered by most of those who use it to represent the
>>> highest degree of thermal metamorphism that a chondrite can experience
>>> without melting. ?As implied in that first sentence, some petrologists
>>> don't distinguish these from type 6. ?The term "primitive achondrite" is
>>> widely taken to be the next stage: you make them when a chondrite
>>> partially melts, and the process of crystal-melt separation begins. ?The
>>> "primitive" part says that the bulk composition is still fairly close to
>>> chondritic. ?But these definitions are not used by everybody, and you
>>> will get arguments about them.
>>>
>>> Clearly, the "LL" part of an LL7 classification for NWA 3100 is
>>> unlikely. ?O isotopes are below the terrestrial fractionation line,
>>> which basically rules it out. ?So it is not an LL7. ?Bunch has shown
>>> that the O isotopes are closer to CR chondrites.
>>>
>>> The hard part is the type 7 vs. primitive achondrite distinction. ?Bunch
>>> et al.'s 2005 and 2008 LPSC abstracts do not report anything in NWA 3100
>>> that I take as evidence of melting or differentiation. ?So I don't see
>>> any reason to call these primitive achondrites, at least not based on
>>> these findings. ?I think the Bunch et al.'s conclusion that NWA 3100 is
>>> a CR6 is the best we have right now, but I think you still have to think
>>> of this as preliminary. ?Ted can correct me, but I think it was actually
>>> the nomcom that pushed for calling this a PAC, amid controversy on the
>>> committee.
>>>
>>> Jeff
>>>
>>>
>>> On 12/5/2011 8:23 PM, Ruben Garcia wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I just bought a smallish collection and several of the slices that
>>>> came with are NWA 3100. Mike Farmer's card was included and lists NWA
>>>> 3100 as an LL7. ?The Met-Bul calls NWA 3100 a Primitive achondrite -
>>>> not an LL7.
>>>>
>>>> My question is this,
>>>>
>>>> Does LL7 denote a particular Primitive achondrite? If so which one? If
>>>> not then what type is this?
>>>>
>>>> BTW - I think Ted Bunch did the classification
>>>>
>>>
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>>
>>
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-- 
Rock On!
Ruben Garcia
Website: http://www.mr-meteorite.net
Articles: http://www.meteorite.com/blog/
Videos: http://www.youtube.com/profile?user=meteorfright#p/u

Received on Mon 05 Dec 2011 11:02:31 PM PST