[meteorite-list] Ensisheim as an IMB?

From: Martin Horejsi <martinh_at_meteoritecentral.com>
Date: Thu Apr 22 10:13:10 2004
Message-ID: <BAD065E3.1E74%martinh_at_isu.edu>

Hi John,

Thanks for the explanation.

You asked the question if there can be impact melts without brecciation? I
suspect that Felt (b) is an example of this. Here is a photo of my slice:

http://aristotle.isu.edu/felt_b.jpg

The region at the bottom is clearly different material separated from the
chondrule-rich area above the line. But no brecciation is visible anywhere
on my piece. However, maybe the large regions are brecciation of some sort
on a much greater scale.

Is this what you were taking about?

Cheers,

Martin



On 4/25/03 2:39 PM, "j.divelbiss_at_att.net" <j.divelbiss@att.net> wrote:

> Martin,
>
> I just read a section on breccias in Norton's book(pg 96-99). It makes it
> pretty clear that all breccias are from impacts...and for the most part, most
> chondrites have some evidence of brecciation (evidence of impact). As you know
> the list of breccia variations is a bit confusing. Application to Chondrites
> versus Achondrites is probably a little different...not sure. I'll give it a
> try for chondrites, please correct where needed.
>
> Monomict - A mixing of the same textures and compositions (ie. L6 with L6 for
> chondrites)
>
> Polymict - A mixing of different textures but the same compositions (L5 light
> with L6 dark)
>
> Genomict - A mixing of different petrologic stages of same composition (L3.8
> and L6)
>
> Regolith - Mixing of different compositions and/or petrologic stages with a
> fine matrix at the surface of an asteroid, or moon, etc. Measurement of solar
> radiation is involved to show surface exposure implying multiple events at
> surface. (H3-6 Zag!)
>
> Impact Melt - Large energy impacts causing great shock and mixing of materials
> to create materials of different shades (darker material for melts). The
> changing of minerals...olivine to spinel, etc. (Park Forest? L6 IMB ?)
>
> The answer is yes about Ensisheim, I think...but when does a chondrite become
> a breccia or even an impact melt breccia? And can there be just impact melts
> (Chico L6 IM)...impact without brecciation????
>
> That clears it up,
>
> John
>
> John
>> Hello All,
>>
>> I was looking at my slice of Ensisheim, and it looks to me like there is
>> little river of lighter material with some islands of darker breccia flowing
>> through it?
>>
>> It sure looks like at least an melt breccia, but how else besides impact
>> would a chondrite become melted?
>>
>> Here is a pic of what I am talking about:
>>
>> http://aristotle.isu.edu/ensisheim.jpg
>>
>> As before, the blue cube is 1cm^3.
>>
>> Cheers,
>>
>> Martin
>>
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Received on Sat 26 Apr 2003 06:35:46 PM PDT