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

From: Jörn Koblitz <koblitz_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:50 2004
Message-ID: <E5E6112EA31FA24CB448E091C6883C050EBB6E_at_server2000.microfab.de>

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
_________________________________________________________________________=
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> -----Urspr=FCngliche Nachricht-----
> Von: bernd.pauli_at_paulinet.de [mailto:bernd.pauli@paulinet.de]
> Gesendet: Montag, 15. M=E4rz 2004 21:20
> An: Meteorite-list_at_meteoritecentral.com
> Betreff: [meteorite-list] Amgala, Tsarev and Zag
>=20
>=20
> Adam wrote:
>=20
> > I do not believe it is going to classify as a
> > regolith breccia but rather a polymict breccia.
>=20
> Adam also wrote:
>=20
> > I thought one distinction made for a regolith breccia is that
> > there are signs of crystal damage caused by the solar wind
>=20
> Martin A. chirped:
>=20
> > Tsarev which is brecciated but not polymict
> > is also altered by solar winds, isn't it?
>=20
> Hello Adam, Martin, and List,
>=20
> There are 3 types of inert and/or noble gases in some meteorites:
>=20
> (1) those produced by cosmic ray bombardment (cosmogenic);
> (2) those resulting from radioactive decay of elements (radiogenic)
> in the meteorite;
> (3) those present originally (=3D trapped or primordial gases).
>=20
> 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.
>=20
> These gases are 4^He, 20^Ne, 36^Ar, 84^Kr, 132^Xe.
>=20
> There are two different sources for these inert/noble gases:
>=20
> (a) solar-type gas
> (b) planetary-type gas
>=20
> To find out "what is what" and "which is which", meteoriticists
> consider the relative amounts and, above all, ratios of a number
> of isotopes.
>=20
> J.T. Wasson proposed the following arbitrary
> definition of a solar gas-rich meteorite:
>=20
> - 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
>=20
> 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).
>=20
> There is an abstract paper by Honda et al. but they only discuss
> cosmogenic nuclides (see: Reference) - again of little help.
>=20
> 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":
>=20
> t1 =3D 8 million years, radius ca. 200 cm
> t2 =3D ca. 0.3 million years, radius ca. 140 cm
>=20
>=20
> Best wishes,
>=20
> Bernd
>=20
>=20
> References:
>=20
> VOGT S.K. et al. (1993) On the Bur Ghelulai H5 chondrite and other
> meteorites with complex exposure histories (Meteoritics 28,=20
> 1993, 71-85).
>=20
> HONDA M. et al. (1992) Cosmogenic nuclides in the
> Tsarev chondrite (Meteoritics 27-3, 1992, 234-235).
>=20
> WASSON J.T. (1974) Meteorites Classification and Properties
> (Springer-Verlag, Berlin, Heidelberg, New York, pp. 97-109).
>=20
> SEARS D.W. (1978) The Nature and Origin of
> Meteorites (Adam Hilger Ltd. Bristol, pp. 110-115).
>=20
> McSWEEN H.Y. (1999) Meteorites and Their Parent Planets
> (Cambridge University Press, Glossary, pp. 41-44, 111-112, 244-248).
>=20
>=20
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>=20
Received on Tue 16 Mar 2004 01:12:18 PM PST