Mathematics – Logic
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29..461e&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 461-462
Mathematics
Logic
4
Abundance, Lithology, Meteoritic Composition, Spinel, Trace Elements, Cooling, Ion Probes, Melting, Petrology, Pyroxenes
Scientific paper
Eframovka E49 is a triangular 2-mm segment from a Compact Type A (CTA) inclusion with large portions of intact core and rim sequence. It is probably a fragment from an originally round approximately equal to 4-mm Ca-Al rich Inclusion (CAI). The core consists of two lithologically different assemblages: (1) The major portion of the CAI contains melilite sprinkled with rare spinel, perovskite, and the new Ca-Ti silicate. It is covered by a six-layer rim consisting of (from the interior outward): two layers of Zr- and Y-rich perovskite, spinel, Al-diopside, diopside, and forsteritic olivine. (2) A 650-micron wide complex xenolith contains coarse spinel, melilite, perovskite, and metal in its interior, surrounded by a broad shell of Al-diopside, diopside, and minor fassaite and anorthite, and in the rim fassaite yields Al-diopside yields diopside. Coarse spinels abundantly display resorbtion outlines and some of the grains have been broken down to several amoeboid fragments floating in the eutectic assemblage. All these textures are evidence of local melting of the xenolith followed by fast cooling. No such features are observed in the host CAI. Since melting is confined to the xenolith, the melt event must have predated its capture into the core of E49. Ion microprobe trace-element studies reveal distinct differences between Rare Earth Element (REE) abundances in perovskites in the xenolith and the host CAI. Perovskites in the xenolith display REE patterns with prominent Yb and small Ce excesses and large Eu depletions. Perovskites in the xenolith show higher abundances of Nb, Zr, and V. Magnesium in xenolith and the host is almost unfractionated. Excesses of Mg-26 are found both in the xenolith and the host with data points plotting along a line with a slope of 4 x 105. This is in accord with the petrographic interpretation and indicates that the melting of the xenolith and its capture in E49 took place early.
El Goresy Ahmed
Zinner Ernst K.
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