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Published May 1977 | public
Journal Article

Experimental petrology of eucritic meteorites


Low pressure melting experiments on eucritic meteorites demonstrate that the compositions of most eucrites can be generated by low pressure fractionation of pigeonite and plagioclase from liquids similar in composition to the Sioux County and Juvinas eucrites. It is unlikely that the liquids with compositions similar to Sioux County and Juvinas were themselves residual liquids produced by extensive fractionation of more magnesian parental liquids. The compositions of Stannern and Ibitira cannot be produced by fractionation of liquids with compositions similar to other known eucrites. Liquid compositions similar to Stannern, Ibitira, and Sioux County could have been generated by increasing degrees of low pressure partial melting of source regions composed of olivine (~Fo65), pigeonite (~Wo5En65), plagioclase (~An94), Cr-rich spinel, and metal. These source assemblages may have been primitive, undifferentiated material of the basaltic achondrite parent body and the eucrites may represent melts produced in early stages of its melting and differentiation. Further melting in these source regions, after exhaustion of plagioclase, may have produced magnesian liquids from which the magnesian pyroxenes and olivines in howardites, diogenites, and mesosiderites crystallized in closed-system plutonic environments. Most of the cumulate eucrites (e.g. Moama, Moore County, Serra de Magé) could not have equilibrated with liquids similar in composition to known eucrites. These cumulates may have accumulated from liquids produced by extensive fractionation of advanced partial melts of the source regions of eucritic liquids. A depletion in Na, K, and Rb in Ibitira is noted.

Additional Information

© 1977 Elsevier Ltd. Received 21 June 1976. Accepted 12 November 1976. I thank R. A. Binns (Millbillillie), C. Frondel (Cachari, Juvinas, Pasamonte, Stannern), R. Hutchison (Béréba, Lakangaon, Sioux County), G. Kurat (Jonzac), J. F. Lovering (Moama), C. B. Moore (Haraiya), F. L. Sutherland (Binda. Emma ville), and H. Wänke (Ibitira) for generously providing meteorite specimens for use in this study. I also thank E. Anders, R. W. Bild, R. A. Binns, R. F. Dymek, D. J. Humphries, R. Hutchison, and D. Walker for unpublished manuscripts and analyses. I have benefitted from discussions with G. M. Biggar, R. A. Binns, M. J. Drake, R. F. Dymek, C. Ford, R. Hutchison, and M. J. O'Hara. This paper has benefitted from thorough reviews by D. Walker and R. Williams and comments from R. Brett. I also thank D. J. Humphries for the use of his least squares mass balance and electron microprobe data reduction computer programs. This work was carried out during the tenure of a Marshall Scholarship awarded by the Marshall Aid Commemoration Commission (U.K.). The equipment and facilities utilized in this study are maintained by the National Environmental Research Council (U.K.) and the University of Edinburgh.

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