[meteorite-list] Gebel Kamil iron is official now - 1.6metrictons!?!?

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Tue, 13 Jul 2010 17:47:01 -0400
Message-ID: <4C3CDED5.4080004_at_usgs.gov>

The analysis in the Meteoritical Bulletin shows this meteorite to have
20% Ni. I don't think any meteorites with this much Ni managed to
develop Widmanstatten patterns during cooling. So unless there is a
large range of composition, which would be very unusual, don't expect to
find any octahedrites here.

Jeff

On 2010-07-13 2:35 PM, Martin Altmann wrote:
> Hi there,
>
>
>> Your base this claim on heat-altered Canyon Diablo 'rim' specimens.
>>
> .....Etc.
>
> No no.. you're interpreting much too much.
>
> It was an example, like Sikhote was an example - that it happens sometimes
> with larger iron falls. That there can be specimens with structure as well
> as specimens, which have lost their structure.
>
> With that Gebel Kamil I didn't want to speculate about the genesis of
> ataxitic irons,
> I simply wanted to say, that IMHO - as so often - there is no urge for a
> hurry, to claim the whole iron to be ataxitic already.
> Because what I heard so far is: there were only (sikhote-like) shrapnels
> found and that 83kg lump. So maybe the latter has some structure preserved.
> Just let's wait.
>
> That I meant. Not more, not less.
>
> Hence quite similarly like e.g. with El Haggouina& pairs. Thousands of
> fragments,
> and those the classifiers had first had no chondrules preserved, hence it
> was classified as an AUB - but later pieces with chondrules showed up, so it
> became evident, that?s an E-chondrite.
>
> Best!
> Martin
>
>
>
>
> -----Urspr?ngliche Nachricht-----
> Von: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Jason
> Utas
> Gesendet: Dienstag, 13. Juli 2010 20:06
> An: Martin Altmann; Meteorite-list
> Betreff: Re: [meteorite-list] Gebel Kamil iron is official now -
> 1.6metrictons!?!?
>
> Martin,
>
> I have two problems with what you're saying. Firstly, you're saying
> that shrapnel doesn't exhibit a widmanstatten pattern in general.
> Your base this claim on heat-altered Canyon Diablo 'rim' specimens.
>
> I'd like to point out that we don't know whether or not there exist
> any true pieces of shrapnel from the Canyon Diablo impact event. I
> have seen heat-altered pieces of Canyon Diablo, but I have never seen
> *shrapnel* pieces of Canyon Diablo (individuals/fragments are too
> weathered to tell original surface features, and I have never seen a
> piece of Canyon Diablo that displayed a mechanically distorted
> pattern).
>
> To be frank, I doubt that any true shrapnel exists from the event.
> The energy released by the event was more than enough to simply melt
> and vaporize the entire impactor.
>
> Which is why I have a problem with your equating the Sikhote-Alin
> impact event to the Canyon Diablo event.
>
> I'm really surprised that you would call the two events similar - one
> was a large scale vaporization event and the other was a simple
> explosive event in which individuals shattered. They're really quite
> different.
>
> And yes, I know about Morasko and Seel?sgen shrapnel - both of which
> *also* display a widmanstatten pattern when cut.
> Thomasz sent me some excellent photos this morning, but I didn't feel
> like getting them up to post to the list.
> In retrospect, I recall that Marcin used to have some on his site:
>
> http://www.polandmet.com/_seelasgen.htm
>
> Wha-la.
>
> So I've posted numerous photos of distorted (but existing)
> widmanstatten patterns of cut shrapnel for you to look at, and yet you
> seem set on insisting that shrapnel doesn't exhibit a widmanstatten
> pattern!
>
> "Well, for me - maybe I'm there conservative - a shrapnel is a totally
> destroyed and tattered lump of an iron meteorite, which fully has lost its
> original structure due to the forces of a major explosion."
>
> To my knowledge, this sort of meteorite *does not exist.* Heat-altered
> specimens of Canyon Diablo show no physical distortion (just a
> watering-down of the pattern), suggesting that they are not shrapnel,
> but that they are rather pieces of the meteorite that simply fell near
> the crater itself as it was forming (and were thus exposed to the heat
> released by the explosion). They do not appear to be explosively
> ejected fragments as we see with Henbury and Sikhote-Alin. Such
> fragments exhibit violently twisted patterns (see Henbury photo from
> my last email).
>
> So, with regards to your statement:
> Seeing as there are no known low-nickel (meteorites that would
> otherwise form a widmanstatten pattern) "ataxites" (meaning, in this
> case, a widmanstatten-less iron, regardless of nickel content) related
> to known impact events on earth, there likely exist no shrapnel
> meteorites in the world, according to your definition.
>
> And, yes, I suppose they might find pieces of this Egyptian meteorite
> that exhibit a widmanstatten pattern.
> This seems, however, to be highly unlikely, for three reasons:
> 1) This was a simple explosion event in which little vaporization and
> thus general heating of the meteorite fragments took place. In other
> words, this was a hell of a lot smaller than the Canyon Diablo event,
> and is much more in line with a Sikhote-like event. As we can see
> with Sikhotes, true shrapnels show violent signs of deformation and
> compression, but no signs of pattern erasure due to impact. If you've
> never seen an etched piece of Sikhote shrapnel in all your years of
> dealing with meteorites, I really don't know what to say to you - I
> couldn't find any good examples of photos online, but you must have
> seen some in the past. I've seen many.
> 2) The only crater that we know of that has actually produced
> heat-altered irons amongst a field of otherwise unaltered irons - is
> Canyon Diablo. Seeing as the Henbury impact event was larger than
> this one (the largest Henbury craters were larger than 40m) -- and the
> specimens created were shrapnels with preserved widmanstatten patterns
> -- we can draw a conclusion.
> It's a smaller crater. Less kinetic energy was released in this
> event, and if there wasn't enough released at Henbury to erase the
> pattern contained within the shrapnel there, I think it's safe to
> assume that the same didn't happen here.
> 3) You should also note that such a melting/reheating event would
> significantly alter the pattern that we would see:
>
> http://tin.er.usgs.gov/meteor/metbull.php?code=52031
>
> A flash-reheating capable of erasing the meteorite's structure would
> erase a plessitic pattern, FYI. It takes an extremely long period of
> time for such crystals to form out of solidified Taenite, and they
> could not form on earth.
>
> In summation -
>
> I disagree with your notion of shrapnel, because if I were to believe
> it, I would have to say that meteoric shrapnel likely does not exist
> on earth. I also find it highly unlikely that this 'Gebel Kamil'
> exhibited a different widmanstatten pattern prior to impact because
> the pattern that it exhibits could not have formed during or post
> impact.
>
> Regards,
>
> Jason
>
> On Tue, Jul 13, 2010 at 10:09 AM, Martin Altmann
> <altmann at meteorite-martin.de> wrote:
>
>> Hi Jason,
>>
>> well and the Sikhote-shrapnels?
>> Or remember these Canyon Diablos, found on one side of the crater rim,
>>
> where
>
>> the pattern was completely annihilated by heat and which are completely
>> recrystallized.
>>
>> If one would had only such examples of Canyon and Sikhote, undoubtedly
>>
> they
>
>> would be given the structural type: ataxite.
>>
>> (Btw. the Bavarian iron find Inningen, which still hasn't been removed
>>
> from
>
>> the Bulletin, which has identical values like Sikhote, got as structural
>> type also ataxite, cause it was a shrapnel. ...a Sikhote-like shrapnel,
>> havig the same trace element data like Sikhote and found without any other
>> pieces nor any impact structures or pits lying on a road - ouch! That
>> hurts...).
>>
>> All I'm telling is, that it might be too early to commit to that
>>
> structural
>
>> type with the Egypt iron, as maybe there will be still found (or examined)
>> more intact pieces.
>>
>> Like so many in this thread I know Gebel Kamil only from the loads our
>> Russian finder kings brought to light and to Ensisheim.
>>
>> They were all extremely stressed, sharp-edged, tattered and torn frazzles
>>
> of
>
>> iron - just like the shrapnels we all know from Sikhote-Alin.
>>
>> How distorted and stressed they are, you can observe on the extremely
>> disturbed and deformed schreibersites in Mirko's slices, if you compare
>> these to the large, angular skeletonised schreibersite crystals in
>> Sikhote-individuals or in Guanaco e.g.
>>
>>
>> You could add also Morasko to your list.
>>
>> Well, for me - maybe I'm there conservative - a shrapnel is a totally
>> destroyed and tattered lump of an iron meteorite, which fully has lost its
>> original structure due to the forces of a major explosion.
>> I guess, that's why also the military term "shrapnel" was used as an
>> analogue for this type of iron meteorites.
>>
>> Those which you mean, which show a partial deformation, I wouldn't call in
>> my personal use "shrapnels", at best maybe partial shrapnels.
>> But that depends on one's individual interpretation, I omit,
>> because "shrapnel" is a not exactly defined term, similar as we have it
>>
> with
>
>> "orientation" or more recently with the "hammer stones".
>>
>> Best!
>> Martin
>>
>>
>>
>>
>>
>>
>>
>>
>> -----Urspr?ngliche Nachricht-----
>> Von: meteorite-list-bounces at meteoritecentral.com
>> [mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Jason
>> Utas
>> Gesendet: Dienstag, 13. Juli 2010 15:23
>> An: Meteorite-list
>> Betreff: Re: [meteorite-list] Gebel Kamil iron is official now - 1.6
>> metrictons!?!?
>>
>> Hello Mirko, All,
>> That's just not true at all - plenty of irons have seen plastic
>> deformation without becoming ataxites.
>>
>>
>> Seymchan:
>>
>>
>>
> http://www.carionmineraux.com/mineraux/Mineraux_Juillet_aout_2008/meteorite_
>
>> seymchan_1.jpg
>>
>> http://www.imca.cc/insights/2007/II06-img/Seymchan.jpg
>>
>>
>> Henbury:
>>
>> http://www.minresco.com/meteor/meimages/me606d.jpg
>>
>>
>> Uruacu:
>>
>>
>>
> http://cgi.ebay.com/LOW-PRICE-URUACU-IRON-METEORITE-BRAZIL-END-CUT-804-GMS-/
>
>>
> 200446229790?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item2eab86bd1e#ht_1622w
>
>> t_906
>>
>>
>>
> http://cgi.ebay.com/LOW-PRICE-URUACU-IRON-METEORITE-BRAZIL-END-CUT-514-GMS-/
>
>>
> 200421205241?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item2eaa08e4f9#ht_1579w
>
>> t_906
>>
>>
>> - I've also seen examples of similar features in Sikhote-Alin,
>> Boxhole, Gibeon, and Campo del Cielo.
>>
>> Plastic deformation due to impact does not result in the complete loss
>> of widmanstatten pattern. The only plastically deformed ataxites that
>> lack any true pattern (that I can think of) are Chinga (deformed
>> schlieren) and this new Egyptian iron, neither of which appear to have
>> had widmanstatten patterns before entering the atmosphere.
>>
>> Regards,
>> Jason
>>
>> On Tue, Jul 13, 2010 at 5:30 AM, Martin Altmann
>> <altmann at meteorite-martin.de> wrote:
>>
>>> But is there a finest octahedrite among the chemical
>>>
>> IAB/IIICD-complex....?
>>
>>> And are there coarsest octahedrites to be found among the IVAs?
>>>
>>> I think, it's quite reasonable, not to give a structural type at that
>>>
>> point
>>
>>> of time for the Egypt iron, if there were only shrapnels found,
>>>
>> respectively
>>
>>> analyzed.
>>> Shrapnels by their nature are always ataxitic.
>>>
>>> Or was meanwhile a not so damaged individual found and examined?
>>>
>>> Best!
>>> Martin
>>>
>>>
>>> -----Urspr?ngliche Nachricht-----
>>> Von: meteorite-list-bounces at meteoritecentral.com
>>> [mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Jeff
>>> Grossman
>>> Gesendet: Dienstag, 13. Juli 2010 13:48
>>> An: meteorite-list at meteoritecentral.com
>>> Betreff: Re: [meteorite-list] Gebel Kamil iron is official now - 1.6
>>>
>> metric
>>
>>> tons!?!?
>>>
>>> "Ataxite" is a structural term, like octahedrite and hexahedrite.
>>> Modern classification of iron meteorites is based on the chemical group,
>>> which can tell you something about the parent asteroid. The structural
>>> classification is quasi-independent of the chemical classification,
>>> inasmuch as members of each structural group can belong to multiple
>>> chemical groups. So "ataxite" has not been replaced with "iron,
>>> ungrouped." Both are correct.
>>>
>>> When I used to edit MetBull, the heading on the description of this
>>> meteorite would have said "Iron, ataxite (ungrouped)", but other editors
>>> have abandoned this.
>>>
>>> Jeff
>>>
>>>
>>>
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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

Received on Tue 13 Jul 2010 05:47:01 PM PDT