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Compositions of three low-FeO ordinary chondrites: Indications of a common origin with the H chondrites |
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| Authors: | Julianne Troiano Mark L Rivers |
| Institution: | a Department of Chemistry, Fordham University, Bronx, NY 10458, United States b Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, United States c Consortium for Advanced Radiation Sources, University of Chicago, Argonne, IL 60439, United States d Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY 10024, United States |
| Abstract: | Burnwell, EET 96031, and LAP 04575 are ordinary chondrites (OC) that possess lower than typical olivine Fa content than has been established for the H chondrites (<∼17 mol%). Mean low-Ca pyroxene Fs contents are typically lower than mean Fa content, with generally ?16 mol% Fs. We have investigated these three low-FeO chondrites by measuring their trace element abundances, oxygen isotopic compositions, and examining their three-dimensional (3D) petrography with synchrotron X-ray microtomography. We compare our results with those established for more common OC. The low FeO chondrites studied here have bulk trace element abundances that are identical to the H chondrites. From bulk oxygen isotopic analysis, we show that Burnwell, EET 96010, and LAP 04757 sampled oxygen reservoirs identical to the H chondrites. Burnwell, EET 96031, and LAP 04575 possess common 3D opaque mineral structures that could be distinct from the H chondrites, as evidenced by X-ray microtomographic analysis, but our comparison suite of H chondrites is small and unrepresentative. Overall, our data suggest a common origin for the low-FeO chondrites Burnwell, EET 96010, and LAP 04757 and the H chondrites. These three samples are simply extreme members of a redox process where a limiting nebular oxidizing agent, probably ice, reacted with material containing slightly higher amounts of metal than typically seen in the H chondrites. |
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