Hi Tracy,
Being the lucky owner of slices if similar size (about 2x2 cm) of Itqiy and
Zaklodzie, I can tell you (qualitatively) that their textures are
definitely different.
However we all know that a macroscopic texture is very seldom
characteristic of a meteorite type (most of the ordinary chondrites are the
best examples).
For "odd" meteorite types, as I am not at all expert, just curious, I love
to browse through the wonderful web site of David Weir:
http://www.meteoritestudies.com/
David reports (among other features) that, although Itqiy was classified in
Met. Bull as "EH7-an", "while similarities do exist between Itqiy and EH or
EL chondrites, the many inconsistencies make a definitive assignment (to EH
group) tenious..."
Founded upon the recent report published by "Keil & Bischoff, 2008" (so
cited), he also states that:
"Itqiy is very similar to NWA 2656 (btw classified as "E-achon" in Met.
Bull.) "with which it shares many textural and morphological
characteristics"...and also:
"that both may have formed on the same parent body, distinct from that
associated with EH, EL, Shallowater and aubrites"...
We all know that one should only rely on the officially published data in
Met. Bull. database.
However as, on one hand, Weir very often reports data from recent
publications (that he obviously summarizes or to which he possibly
sometimes just adds some (to me always pertinent) comemnts) and, on the
other hand, such data are not (always) reported in the database that, as
one can understand, are not easy to update continuously, I like to keep
Weir's updatings in mind for my best understanding, hoping that the new
publications will sooner or later be taken into account officially.
This being, I don't have the paper of Keil and Bischoff on hand to better
compare.
Perhaps Bernd can help ?
Regarding similarities between Zaklodzie (classified in Met. Bull. as "E
achon-ung" but that recent studies by Keil (2007) and Keil & Bischoff
(2008) rather classify as E imb chondrite) and Itqiy, I encourage you to
read the very informative statements Weir reports regarding Zaklodzie.
He concludes:
"...despite the very close similarities between Zaklodzie and the ungrouped
enstatite achondrite Itqiy, their chemical end mineral compositions, noble
gas contents and terrestrial ages EXCLUDE an origin of both meteorites from
a common parent body".
I am just reporting here some published data and my poor expertise in that
domain does not pretend to solve the question. As a scientist, I learned
that we should be cautious with new data but that, on the other hand, there
can also be always some (minor or major) thruth behind.
Assembling and summarizing (with expertise) such data is, among many other
merits, the deep interest of David Weir's statements.
I hope this helps.
My best,
Zelimir
A 01:25 13/12/2008 +0000, tracy latimer a écrit :
I have now heard from at least 3 parties who say that Itqiy is closest in
composition to Zaklodzie (and a couple of people who gently corrected my
typewriter dyslexia, Saint-Sauveur rather than Saint-Severin!). The
pictures I have been able to find of Zaklodzie, however, don't show the
texture very well; to my uneducated eye, it looks more like a common H5
(heresy!). One of the things I find striking about Itqiy is the coarse
grained crystals that look almost like commercially available black
granite slab. Anyone who has access to both Itqiy and Zaklodzie slices,
do they actually look similar in section?
I have to do more research into the processes that produce 2 so dissimilar
textures with almost the same chemical makeups...
Tracy Latimer
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Prof. Zelimir Gabelica
Université de Haute Alsace
ENSCMu, Lab. GSEC,
3, Rue A. Werner,
F-68093 Mulhouse Cedex, France
Tel: +33 (0)3 89 33 68 94
Fax: +33 (0)3 89 33 68 15
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