Aubrites: Their origin and relationship to enstatite chondrites
نویسندگان
چکیده
All ten known aubrites (enstatite achondrites) as well as Happy Canyon and Mt. Egerton, related anomalous meteorites, have been studied in order to understand their origin and relationship to enstatite chondrites. Mineralogically, aubrites contain 75-9B% enstatite (En98.76-99.54), 1-16% plagioclase (Anl.S-B.:), O.Z-K.l^r diopside (Wo40.1-46.1). 0.3-10.07f olivine (Fo99.79-99,99), <0.l3.7% metallic Fe-Ni(Ni, 3.7-6.8^^^1 Si, 0,1-2,4'îf), <0.1-7.1% Ti bearing troiUte(Ti, 0.6-5.7%). and trace amounts of oldhamite, daubréelite, ferromagnesian alabandite and schreibersite. Generally, the silicate and sulfide portions of Happy Canyon and Mt. Egerton showstrongsimilarities to the aubrites. Based on similarities in bulk chemistry of the silicate portions, major and minor phases and inferred oxygen fugacity, we conclude that the most likely parent material for the aubrites are E6 chondrites, REE data on the aubrites shows negative Eu anomalies. This indicates thai the aubrites formed through fractional crystallization. The addition of 10% plagioclase of An 15 composition (avg. E6 plagioclase) to the bulk composition of the silicate ponion of the aubrites results in good agreement with that of E6 chondrites.
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