Incompletely compacted equilibrated ordinary chondrites |
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| Authors: | Matthew R Sasso Robert J Macke Joseph S Boesenberg Daniel T Britt Mark L Rivers Denton S Ebel Jon M Friedrich |
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| Institution: | 1. Department of Chemistry, Fordham University, Bronx, New York 10458, USA;2. Department of Physics, University of Central Florida, Orlando, Florida 32816, USA;3. Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York 10024, USA;4. Consortium for Advanced Radiation Sources, University of Chicago, Argonne, Illinois 60439, USA |
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| Abstract: | Abstract— We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high‐resolution synchrotron X‐ray microtomography (μCT) and helium pycnometry. We found total porosities ranging from ～10 to 20% within these chondrites, and with μCT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1‐S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not “fluffed” on their parent body by impact‐related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt. |
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