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Petrogenesis of angrites |
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| Authors: | Christine Floss Ghislaine Crozaz Takashi Mikouchi |
| Institution: | 1 Laboratory for Space Sciences and Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA 2 Mail Code SN2, NASA Johnson Space Center, Houston, TX 77058, USA 3 Department of Earth and Planetary Science, University of Tokyo, Hongo Bunkyo-ku, Tokyo 113-0033, Japan 4 Southwest Meteorite Laboratory, P.O. Box 95, Payson, AZ 85547, USA |
| Abstract: | The recent discovery of two new angrites, Sahara 99555 and D'Orbigny, has revived interest in this small group of achondrites. We measured trace element abundances in the individual minerals of these two angrites and compared them with the three Antarctic angrites, LEW 86010, LEW 87051 and Asuka 881371. Trace element variations in four of these meteorites (LEW 87051, Asuka 881371, Sahara 99555 and D'Orbigny) indicate rapid crystallization under near closed system conditions, consistent with their mineralogical and textural features. All four appear to be closely related and crystallized from very similar magmas. Discrepancies between their bulk REE compositions and melts calculated to be in equilibrium with the major phases may be due in part to kinetic effects of rapid crystallization. Prior crystallization of olivine and/or plagioclase may also account for the elevated parent melt composition of clinopyroxene in some of the angrites such as Asuka 881371.LEW 86010 also crystallized from a melt and represents a liquid composition, but trace element trends in clinopyroxene and olivine differ from those of the other angrites. This meteorite seems to have crystallized from a different source magma. |
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