meteorite # 1257 : Estherville

Voici la suivante : (espérons qu'il y ait des participants !!!)

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Meso-sidérite ?? NWA??

Méso
NWA

A4 ?

USA style "la petite méso dans la prairie" ?

A4 pas tout à fait
Pour Serge oui
Je voudrais aussi connaître la nature de sa partie achondritique dans la famille des HED
énigme d'actualité donc !!!

Oui m'enfin, achondritique c'est quasi par définition puisque c'est de la stone sans chondres.

Estherville A3/4 et sa part "achondrite eucritique" ?

Eh eh j'en ai un frag, on jurerait de la Tata

Bravo vivien c'est bien Estherville, pour la nature il me semblait avoir lu quelque chose là dessus mais je ne retrouve pas le doc donc je ne sais plus bon je continue mes recherches, voici un lien qui parle de l'histoire de cette météorite si belle : [Vous devez être inscrit et connecté pour voir ce lien]

A toi Vivien, la suivante !!!

Au niveau de la famille de la partie achondritique, je me suis basé sur la géochronologie, voir cet abstract :


The Estherville mesosiderite: U---Pb, Rb---Sr, and Sm---Nd isotopic study of a polymict breccia

M Brouxel*, a and M Tatsumotoa
aUS Geological Survey, Branch of Isotope Geology, MS 963, PO Box 25046, Denver, CO 80225, USA
Received 27 August 1990; accepted 31 January 1991. Available online 14 April 2003.
Abstract
A systematic U---Pb, Sm---Nd, and Rb---Sr isotopic study shows that the Estherville mesosiderite was formed between 4.56 and 4.43 Ga. Observed isotopic heterogeneity is in agreement with multiple generations of meteoritic impacts described in other mesosiderites.
At least part of the Estherville silicate fraction was formed early in solar system history as indicated by the Pb-Pb (4555 ± 35 Ma), U---Pb (4560 ± 31 Ma), Rb---Sr (4542 ± 203 Ma), and Sm---Nd (4533 ± 94 Ma) ages. Mesosiderites therefore present not only petrological but also geochronological similarities with eucrites. The Pb isotopic composition of the metal phase plots on the same isochron as the silicates, indicating formation and subsequent mixing with silicates early in the history of the solar system. This is consistent with previous observations indicating that iron was reduced during the silicate-magmatic stage, most likely a consequence of mixing with metal.
In addition to these more-ancient portions of the Estherville breccia, other parts were formed later as suggested by the Pb-Pb (4422 ± 50 Ma) and U---Pb (4437 ± 11 Ma) ages observed in a second group of leaches and residues. This age is similar to some cumulate eucrite ages and may represent the formation of a second mesosiderite component.
The Sm---Nd and the Rb---Sr ages obtained on Estherville show large errors that may be a consequence of the mixing between the 4.56 and 4.43 Ga endmembers.
Estherville, like most mesosiderites, was affected by a major heating event around 3.5-3.7 Ga as shown by the Ar-Ar ages (Bogard et al., 1990). This heating event partially disturbed the Rb---Sr isotopic system (Rb---Sr metamorphic ages range between 3.81 and 4.08 Ga).

* Present address: DUNE Travaux Spéciaux, Laboratoire d'Analyses et de Recherches, C.E.I., Campus Universitaire de la Doua, BP 2132, 69603 Villeurbanne Cedex, France.
Geochimica et Cosmochimica Acta
Volume 55, Issue 4, April 1991, Pages 1121-1133