Hi Ruben,
Both of the researchers, based on Dr. Bunch's work seem too agree it is
a chondrite.
So if I were representing it based on the work cited, I'd say:
The definitive classification is still pending, as the initial LL
classification has been shown not to be the case, but instead it is
"thought to be highly evolved chondrite, possibly related to a deeper
excavation from the carbonaceous CR parent body." You could fit in
"likely type 6" if you wanted.
I guess that's why nomenclature is such a fun issue. Once we can put a
nickname on it, suddenly it is compartmentalized into its own flock of
sheep and we all speak of it as if we knew what we were talking about,
but easily can miss out on subtile differences that could be much more
remarkable. Reminds me of the story in the Little Prince when no one
took seriously the Turkish astronomer who discovered the asteroid until
he put a suit on himself and gave it a name "B612" and everyone
suddenly understood everything ;-)
Kindest wishes
Doug
-----Original Message-----
From: Ruben Garcia <[email protected]>
To: John Lutzon <[email protected]>
Cc: meteorite-list <[email protected]>; jngrossman
<[email protected]>
Sent: Mon, Dec 5, 2011 11:02 pm
Subject: Re: [meteorite-list] Primitive Achondrite Question
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 <[email protected]> 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" <[email protected]>
To: "Jeff Grossman" <[email protected]>;
<[email protected]>
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" <[email protected]> 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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--
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
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