[meteorite-list] Ureilite Formation
Abdelfattah Gharrad
life19maroc at yahoo.fr
Mon Oct 6 21:31:06 EDT 2014
Thanks Bernd for your answer.
I was thinking about this type of meteorites and I think they are unique and it's like a kind of transition from a kind of chondrite-rich of carbon to primitive achondrite with absence of chondrules and high magnetism (pressure and temperature) . what let me to post this question on the list so I find that ureilites are typical.
this my opinion. I am not graduated on this field but always we want to learn as everytime some thing new appear and also we want really know about the meteorites.
I thank all the people whom writed me to guide me and share with me their information.
Thanks again,
Abdelfattah.
--------------------------------------------
En date de : Lun 6.10.14, Bernd V. Pauli via Meteorite-list <meteorite-list at meteoritecentral.com> a écrit :
Objet: [meteorite-list] Ureilite Formation
À: meteorite-list at meteoritecentral.com
Date: Lundi 6 octobre 2014, 23h13
Hello Abdelfattah and List,
In 1992, C.A. Goodrich wrote a very comprehensive paper
about ureilite
formation. If you have access to this invited review, I
strongly advise you
read it:
GOODRICH C.A. (1992) Invited Review - Ureilites: A critical
review
(Meteoritics 27-4, 1992, pp. 327-352).
It is almost impossible to explain in just a few words how
these coarse-grained, ultramafic, highly fractionated,
igneous rocks were formed. Mrs. Goodrich was
well aware that ureilites have some primitive
characteristics that are difficult to
reconcile with extensive igneous processing. Among these
are:
1) metal with high abundances of trace siderophile
elements,
2) carbon which contains planetary-type noble gases;
3) the oxygen isotopic signature of
primitive/unequilibrated
solar system materials.
Both (1) and (2) are typical of undifferentiated, chondritic
(!) materials but in
terms of mineralogy and lithophile element chemistry
ureilites are absolutely non-chondritic. They rather
resemble ultramafic rocks from the Earth and Moon.
Moreover, the presence of noble gases in near-chondritic
abundances is difficult
to explain because gases are expected to be lost at high
temperature. This is
especially difficult to explain because none of the other
major achondrite types
contain noble gases in chondritic or near-chondritic
abundances.
So you probably understand that there is no easy answer to
your question
but I am sure Mrs. Goodrich’s Review will “emlighten”
you!
Best regards,
Bernd
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