[meteorite-list] "Iron" Breccias

From: meteorites_at_space.com <meteorites_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:56 2004
Message-ID: <20020131153909.21701.c000-h015.c000.wm_at_mail.space.com.criticalpath.net>

On Thu, 31 January 2002, Mark Fox wrote

>
> January 31, 2002
>
> Greetings Meteorite Enthusiasts!
>
> Here is a question to spur the noodle.
>
> Has anyone discovered or identified an iron breccia
> meteorite yet, in which two different irons unite in
> a cosmic collision? I have not heard of such a
> meteorite, although I am quite aware of mesosiderites
> --- which describe the event of what occurs when an
> iron asteroid (or at least one predominantly iron)
> crashes into a stony parent body or vice versa.
>
> Such an iron breccia, I can imagine, would consist of
> fewer iron-nickel clasts (of foreign parent body
> origin), due to the malleability of the metallic
> elements involved, than stony clasts in stony
> breccias. Also, when etched, the borders between
> the impactor and the host meteorite, even if it they
> are of the same class, would be noticed since the
> instant heat caused by the shock would not only bond
> the two, but mix the metals adjacent to the borders.
> Thus, in those areas the metals may form a slightly
> different alloy or disrupt the pattern if both
> individual asteroids are octahedritic in origin.
> This is all quick speculation, mind you.
>
> Enjoy, and long strewn fields!
>
> Mark Fox
> Newaygo, MI USA


This is one of the questions that I was hoping to
resolve in my Meteor Crater study involving the
collection of irons and documenting their exact
positions of find.

I started this project in 1992 and after a few seasons
and searching 6 miles away with little results, we ran
into the Bar-T-Bar roadblock-- they were not willing to
allow such a collection.

It is amazing to think that not one single documented
collection with exact locations has ever been done at
Meteor Crater--- NOT ONE!

(Unless one considers the Holsinger effort of 1909 to
be it-- and that was pretty shoddy work if you ask me--
and few of the pieces survive)

But with regards to the question of iron breccias,
Nininger noted that there are three iron meteorite
types which he identified as "Type I" "Type II" and
"III"

These irons have different patterns, and I encountered
one very strange iron in the midst of a group of irons
that were collected from Meteor Crater back in the
1950's.

This iron was sectioned and it had the distinct coarse
pattern of CD irons on one half an then on the other,
its pattern was much finer, almost like Toluca. And
topping it off were two peanut sized silicate
inclusions right in the middle and on the dividing line.

This piece was sent to UCLA and is currently in their
collection.

The question that Nininger had and verbally expressed
to me was did the different types he and other
encountered represent an "iron breccia?"

In other words, was the impactor that made Meteor
Crater a breccia?

And another question yet to be resolved-- is the so
called Winona Meteorite actually a silicate inclusion
to this impactor?

Twenty-five years ago, while a student at NAU I was
hiking around Meteor Crater out on the plains a good
distance away, when I encountered what I thought to be
a "shale ball"

But this was not like any shale ball that I had ever
seen. It weighed about 20 lbs and was partly buried, I
removed it and examined it closely. What impressed me
was the streaks of dark oxide in an otherwise tan
matrix covered with green streaks.

I thought it a strange rock, and was not certain that
it was in fact meteorite oxide. I broke it by slamming
it onto another rock to see what it looked like on a
fresh broken surface. Again it had what looked like
dark oxide streaks in a matrix that was dark tan, and
in places with green spots.

I should have taken it for further test, but left it
where I found it.

Then many years later I, and Dr. John Wasson were given
the opportunity to see the Winona Meteorite crypt from
which this meteorite was found (It is still preserved
and at the Museum of Northern Arizona). And I was also
very surprised to see that it had inside it perhaps ten
or more pounds of the Winona Meteorite.

I was stunned by what I saw-- IT WAS EXACTLY SAME ROCK
THAT I HAD ENCOUNTERED more than twenty years earlier,
out on the plains of Meteor Crater.

Unfortunately-- the spot is on Bar-T-Bar lands and they
will not allow anyone to invest gate this further.

And that is a shame-- for according to Dr. Wasson and
others that I have communicated with, the meteorite
that made Meteor Crater, SHOULD have silicate
inclusions-- like the so called WINONA METEORITE.

And this is something that SHOULD be investigated
further, as it will shed light on the origin of this
enigmatic group of meteorites called the "Winonites"

(I know precisely where I left the pieces that I found
and am currently working with someone to invest gate it
further-- I hope that it is still there)

I think though, that the different patterns that
Nininger and others noted with regards to the Meteor
Crater impactor, and the possibility that the Winona
Meteorite is related indicates that there might very
well be "iron breccias"

Further study of Meteor Crater, its irons and possible
silicate inclusions are in order.

(But only if the powers to be out there can be
convinced that it is important to do so)

Steve Schoner, AMS

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Received on Thu 31 Jan 2002 06:39:06 PM PST