AW: AW: [meteorite-list] Amgala, Tsarev and Zag

From: Adam Hupe <adamhupe_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:51 2004
Message-ID: <031801c40d57$927259e0$ad971018_at_attbi.com>

Hi John and group,

I enjoyed the reading when I returned this afternoon. I was unaware that
polymict breccia chondrites were rarer than regolithic breccias. I guess
there is always room to learn something new and when the List is used
properly it can provide educational gems such as this. I think the term
transitional is used to describe an H/L classification. This means to me
that the chondrite came from a completely different parent body than an H or
an L therefore it is not the mixing of two parent bodies. Since I never
studied the H/L designation and only a few exist there is room here for
something to be learned.

Sounds like an interesting subject,

Adam


----- Original Message -----
From: <j.divelbiss_at_att.net>
To: "Jörn Koblitz" <koblitz_at_microfab.de>
Cc: <Meteorite-list_at_meteoritecentral.com>
Sent: Thursday, March 18, 2004 5:51 PM
Subject: Re: AW: AW: [meteorite-list] Amgala, Tsarev and Zag


> Joern,
>
> Thanx a lot for the great answers. I think many will benefit from this
exchange.
> I know Adam will be happy that you helped his cause to highlight the
uniqueness of the polymict chondrite feature of Amgala. Now we'll wait for
those results...How about it Adam?
>
> Couldn't the H/L's get mixed together in space to create a
polymict...seems reasonable, even if we don't have a good example
yet...maybe Amgala will be just that.
>
> Regards,
> John
> > Dear John,
> >
> > I think, for chondrites, regolith breccias (monomict or genomict) are
quite more
> > abundant than polymict breccias. The opposite is true for achondrites.
Polymict
> > breccias, especially eucrites (howardites are polymict by definition!)
are quite
> > often polymict (there is an unusual high fraction of polymict eucrites
from
> > Antarctica), whereas regolith breccias are rather common only for
lunaites (e.g.
> > anorthositic highland breccias), which are - by definition -
achondrites. A nice
> > example for another regolithic achondrite is the howardite Kapoeta
(higly
> > solar-gas-rich material).
> >
> > Regarding the H/Ls (Bremervoerde, NWA 1955, Tieschitz...): these aren't
polymict
> > breccias containing H and L lithologies, but members of a group
intermediate
> > between H and L chondrite in terms of composition and isotopic
signatures. They
> > likely come from a parent body (PB) distinct from the PBs of both, the L
and H
> > chondrites. Though they are breccias, they are not mixing products of L
and H
> > material.
> >
> > Best wishes,
> > Joern
> >
> >
____________________________________________________________________________
___
> > Joern Koblitz
> > MetBase Editor
> > The MetBase Library of Meteoritics and Planetary Sciences
> > Benquestrasse 27
> > D-28209 Bremen, Germany
> > phone: +49 421 24 100 24
> > fax: +49 421 24 100 99
> > email: info_at_metbase.de
> >
____________________________________________________________________________
___
> >
> >
> >
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: j.divelbiss_at_att.net [mailto:j.divelbiss@att.net]
> > > Gesendet: Dienstag, 16. März 2004 19:44
> > > An: Jörn Koblitz
> > > Cc: bernd.pauli_at_paulinet.de; Meteorite-list@meteoritecentral.com
> > > Betreff: Re: AW: [meteorite-list] Amgala, Tsarev and Zag
> > >
> > >
> > > Joern,
> > >
> > > Thanx for the clarification on regolith versus the basic
> > > breccia types.
> > >
> > > As far as chondrites go...is a genomict breccia with a
> > > regolith history like Zag more or less unusual when compared
> > > to a polymict breccia for chondrites, as in the supposed case
> > > for Amgala? I ask this since you did point out that
> > > achondrites are the ones that usually have the polymict
> > > breccias, and not chondrites.
> > >
> > > Does this make NWA 1955 (H/L 3-4) a polymict breccia also? Or
> > > does its classification as being unequilibrated chondrite
> > > make it different than a breccia per say?
> > >
> > > John
> > >
> > > > Tsarev noble gas data data:
> > > >
> > > > he_3 he_4 ne_20 ne_21 ne_22 ar_36 ar_38 ar_40
> > > > 1,58 121 0,54 0,54 0,60 0,42 0,11 575
> > > > 2,07 108 0,78 0,82 0,88 0,83 0,20 1635
> > > > all values: x 10E-8 cc STP/g
> > > >
> > > > Reference: Herzog G. F., Vogt S., Albrecht A., Xue S., Fink
> > > D., Klein J.,
> > > > Middleton R., Weber H. W. and Schultz L. (1997) Complex
> > > exposure histories for
> > > > meteorites with "short" exposure ages. Meteoritics 32, 413-422.
> > > >
> > > > According to this, Tsarev isn't a regolith breccia.
> > > >
> > > > BTW: A regolith breccia can be either polymict (different
> > > source types of
> > > > clasts, e.g., H3 + L6), xenolithic (some minor exotic
> > > (non-host type) clasts,
> > > > e.g. CM clasts in L6 host), genomict (same material type
> > > but different
> > > > petrologic grades, e.g. H3 + H5), or monomict (e.g. light
> > > H3 + dark H3
> > > > (irradiated) lithologies). Usually, regolith breccias are
> > > monomict or genomict
> > > > breccias. Achondrites are often polymict breccias (e.g.
> > > howardites, eucrites,
> > > > diogenits, ureilites, lunaites).
> > > >
> > > > Regards,
> > > > Joern
> > > >
> > > >
> > > ______________________________________________________________
> > > _________________
> > > > Joern Koblitz
> > > > MetBase Editor
> > > > The MetBase Library of Meteoritics and Planetary Sciences
> > > > Benquestrasse 27
> > > > D-28209 Bremen, Germany
> > > > phone: +49 421 24 100 24
> > > > fax: +49 421 24 100 99
> > > > email: info_at_metbase.de
> > > >
> > > ______________________________________________________________
> > > _________________
> > > >
> > > >
> > > >
> > > > > -----Ursprüngliche Nachricht-----
> > > > > Von: bernd.pauli_at_paulinet.de [mailto:bernd.pauli@paulinet.de]
> > > > > Gesendet: Montag, 15. März 2004 21:20
> > > > > An: Meteorite-list_at_meteoritecentral.com
> > > > > Betreff: [meteorite-list] Amgala, Tsarev and Zag
> > > > >
> > > > >
> > > > > Adam wrote:
> > > > >
> > > > > > I do not believe it is going to classify as a
> > > > > > regolith breccia but rather a polymict breccia.
> > > > >
> > > > > Adam also wrote:
> > > > >
> > > > > > I thought one distinction made for a regolith breccia is that
> > > > > > there are signs of crystal damage caused by the solar wind
> > > > >
> > > > > Martin A. chirped:
> > > > >
> > > > > > Tsarev which is brecciated but not polymict
> > > > > > is also altered by solar winds, isn't it?
> > > > >
> > > > > Hello Adam, Martin, and List,
> > > > >
> > > > > There are 3 types of inert and/or noble gases in some meteorites:
> > > > >
> > > > > (1) those produced by cosmic ray bombardment (cosmogenic);
> > > > > (2) those resulting from radioactive decay of elements
> > > (radiogenic)
> > > > > in the meteorite;
> > > > > (3) those present originally (= trapped or primordial gases).
> > > > >
> > > > > No. (3) is what we are interested in to find out if Amgala, Tsarev
> > > > > and Zag have or have not been altered by solar wind particles.
> > > > >
> > > > > These gases are 4^He, 20^Ne, 36^Ar, 84^Kr, 132^Xe.
> > > > >
> > > > > There are two different sources for these inert/noble gases:
> > > > >
> > > > > (a) solar-type gas
> > > > > (b) planetary-type gas
> > > > >
> > > > > To find out "what is what" and "which is which", meteoriticists
> > > > > consider the relative amounts and, above all, ratios of a number
> > > > > of isotopes.
> > > > >
> > > > > J.T. Wasson proposed the following arbitrary
> > > > > definition of a solar gas-rich meteorite:
> > > > >
> > > > > - The 20^Ne/22^Ne ratio should be greater than 2.5
> > > > > - Ne isotopic data should plot above the dashed line
> > > > > you find on p. 102 and on p. 111 of Wasson's and
> > > > > Sears' books (see: Reference)
> > > > > - The 4^He content should exceed 2 x 10^-5 cm^3 g^-1
> > > > > - The 20^Ne / 36^Ar ratio should be greater than 0.3
> > > > >
> > > > > Unfortunately, I don't have any of these isotope data handy for
> > > > > Tsarev :-( What I do have are some 3^He and 21^Ne data from
> > > > > the MPI Mainz but they are of little help at the moment).
> > > > >
> > > > > There is an abstract paper by Honda et al. but they only discuss
> > > > > cosmogenic nuclides (see: Reference) - again of little help.
> > > > >
> > > > > Anyway, Tsarev is a special case and as such mentioned in a
> > > > > research article by S.K. Vogt et al. The authors group Tsarev
> > > > > with a number of other H and L chondrites that underwent a
> > > > > complex "two-stage exposure history":
> > > > >
> > > > > t1 = 8 million years, radius ca. 200 cm
> > > > > t2 = ca. 0.3 million years, radius ca. 140 cm
> > > > >
> > > > >
> > > > > Best wishes,
> > > > >
> > > > > Bernd
> > > > >
> > > > >
> > > > > References:
> > > > >
> > > > > VOGT S.K. et al. (1993) On the Bur Ghelulai H5 chondrite and other
> > > > > meteorites with complex exposure histories (Meteoritics 28,
> > > > > 1993, 71-85).
> > > > >
> > > > > HONDA M. et al. (1992) Cosmogenic nuclides in the
> > > > > Tsarev chondrite (Meteoritics 27-3, 1992, 234-235).
> > > > >
> > > > > WASSON J.T. (1974) Meteorites Classification and Properties
> > > > > (Springer-Verlag, Berlin, Heidelberg, New York, pp. 97-109).
> > > > >
> > > > > SEARS D.W. (1978) The Nature and Origin of
> > > > > Meteorites (Adam Hilger Ltd. Bristol, pp. 110-115).
> > > > >
> > > > > McSWEEN H.Y. (1999) Meteorites and Their Parent Planets
> > > > > (Cambridge University Press, Glossary, pp. 41-44,
> > > 111-112, 244-248).
> > > > >
> > > > >
> > > > > ______________________________________________
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> > > > >
> > > >
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> > >
> >
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Received on Thu 18 Mar 2004 09:12:02 PM PST