Paper No. 262-6
Presentation Time: 9:00 AM-6:30 PM
INVESTIGATION OF AUBRITES THROUGH INTEGRATION OF 3D MODAL MINERALOGY WITH X-RAY MICRO-COMPUTED TOMOGRAPHY AND GEOCHEMISTRY
WILBUR, Zoë E.1, UDRY, Arya2, COLEFF, Daniel M.3, VANDER KAADEN, Kathleen E.4, MCCUBBIN, Francis M.5, ZEIGLER, Ryan A.6, MCCOY, Timothy J.7, ZIEGLER, Karen8, GROSS, Juliane9 and DEFELICE, Christopher2, (1)Department of Geoscience, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154; Jacobs- JETS Contract, NASA Johnson Space Center, Houston, TX 77058, (2)Department of Geoscience, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154, (3)HX-5-JETS Contract, NASA Johnson Space Center, Houston, TX 77058, (4)Jacobs- JETS Contract, NASA Johnson Space Center, Houston, TX 77058, (5)NASA Johnson Space Center, 2101 E NASA Parkway, Houston, TX 77058, (6)Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, 2101 E NASA Parkway, Houston, TX 77058, (7)Mineral Sciences, Smithsonian Institution, PO Box 37012, MRC 119, Washington, DC 20013, (8)Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, (9)Dept. of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854; Dept. of Earth and Planetary Sciences, The American Museum of Natural History, New York, NY 10024
The aubrites (~30 known meteorites) are a unique group of differentiated meteorites that formed on parent bodies with oxygen fugacities (ƒO
2) ~2 to ~6 log units below the iron-wüstite buffer. At these highly reduced conditions, elements deviate from the geochemical behavior exhibited at terrestrial
fO
2, including the formation of FeO-poor silicates and exotic sulfides. Geochemical examinations of aubrites, such as mineral major-element compositions, bulk-rock compositions, O isotopes, and crystallization ages, are crucial to understand their formation and evolution at extreme ƒO
2 conditions. While previous studies have described the petrology and 2D modal abundances of aubrites, this work investigates the 3D modal mineralogies of silicate, metal, and sulfide phases in aubrite samples, which are compared to the available 2D data. We utilize X-ray computed tomography (XCT) to non-destructively analyze the distribution and abundances of mineral phases in aubrites and locate composite clasts of metal and sulfide grains for future analytical study. This study offers the first 3D modal mineralogical data for a representative suite of aubrites.
Currently, we have produced 3D scans of the Norton County aubrite. We have scanned 8- and 17-gram samples at 165 keV and 90 µA as well as 180 keV and 115 µA, respectively. The results of the XCT data have allowed for the determination of the abundances of silicate groundmass (i.e., enstatite, forsterite, albite, and diopside), light (based on electron density) sulfides (i.e., alabandite [MnS], and daubréelite [FeCr2S4]), heavy sulfides (i.e., troilite [FeS]), and Fe,Ni metal by segmenting a density histogram in Volume Graphics Studio software. XCT scans of the Peña Blanca Spring aubrite are currently underway. By combining the 3D representation of the exotic phases found in aubrites with existing 2D characterizations, we are able to better determine modal abundances. By integrating 3D and 2D modal abundances and geochemistry, we can ultimately better constrain aubrite petrogenesis and elemental partitioning. Furthermore, application of this new 3D approach offers the opportunity to identify and select clasts for future study prior to cutting the sample, which will minimize sample loss of this precious material.
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