Shape,metal abundance,chemistry, and origin of chondrules in the Renazzo (CR) chondrite |
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| Authors: | Denton S EBEL Michael K WEISBERG Jessica HERTZ Andrew J CAMPBELL |
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| Institution: | 1. Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York 10024, USA;2. Department of Physical Sciences, Kingsborough College and Graduate School of CUNY, 2001 Oriental Blvd., Brooklyn, New York 11235, USA;3. The Columbia Preparatory School, 5 W. 93rd St., New York, New York 10025, USA;4. Department of Geology, University of Maryland, College Park, Maryland 20742, USA |
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| Abstract: | Abstract— We used synchrotron X‐ray microtomography to image in 3‐dimensions (3D) eight whole chondrules in a ?1 cm3piece of the Renazzo (CR) chondrite at ?17 μm per volume element (voxel) edge. We report the first volumetric (3D) measurement of metal/silicate ratios in chondrules and quantify indices of chondrule sphericity. Volumetric metal abundances in whole chondrules range from 1 to 37 volume % in 8 measured chondrules and by inspection in tomography data. We show that metal abundances and metal grain locations in individual chondrules cannot be reliably obtained from single random 2D sections. Samples were physically cut to intersect representative chondrules multiple times and to verify 3D data. Detailed 2D chemical analysis combined with 3D data yield highly variable whole‐chondrule Mg/Si ratios with a supra‐chondritic mean value, yet the chemically diverse, independently formed chondrules are mutually complementary in preserving chondritic (solar) Fe/Si ratios in the aggregate CR chondrite. These results are consistent with localized chondrule formation and rapid accretion resulting in chondrule + matrix aggregates (meteorite parent bodies) that preserve the bulk chondritic composition of source regions. |
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