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Cosmic-ray exposure age and preatmospheric size of the Bunburra Rockhole achondrite
- Source :
- Meteoritics & Planetary Science. 47:186-196
- Publication Year :
- 2011
- Publisher :
- Wiley, 2011.
-
Abstract
- – Bunburra Rockhole is the first meteorite fall photographed and recovered by the Desert Fireball Network in Australia. It is classified as an ungrouped achondrite similar in mineralogical and chemical composition to eucrites, but it has a distinct oxygen isotope composition. The question is if achondrites like Bunburra Rockhole originate from the same parent body as the howardite-eucrite-diogenite (HED) meteorites or from several separate, differentiated parent bodies. To address this question, we measured cosmogenic radionuclides and noble gases in the Bunburra Rockhole achondrite. The short-lived radionuclides 22Na and 54Mn confirm that Bunburra Rockhole is a recent fall. The concentrations of 10Be, 26Al and 36Cl as well as the 22Ne/21Ne ratio indicate that Bunburra Rockhole was a relatively small object (R approximately 15 cm) in space, consistent with the photographic fireball observations. The cosmogenic 38Ar concentration yields a cosmic-ray exposure (CRE) age of 22 ± 3 Myr, whereas 21Ne and 3He yield approximately 30% and approximately 60% lower ages, respectively, due to loss of cosmogenic He and Ne, mainly from plagioclase. With a CRE age of 22 Myr, Bunburra Rockhole is the first anomalous eucrite that overlaps with the main CRE peak of the HED meteorites. The radiogenic K-Ar age of 4.1 Gyr is consistent with the U-Pb age, while the young U,Th-He age of approximately 1.4 Gyr indicates that Bunburra Rockhole lost radiogenic 4He more recently.
- Subjects :
- Eucrite
Radionuclide
Radiogenic nuclide
010504 meteorology & atmospheric sciences
Geochemistry
engineering.material
010502 geochemistry & geophysics
01 natural sciences
Isotopes of oxygen
Parent body
Astrobiology
Geophysics
Meteorite
Space and Planetary Science
engineering
Plagioclase
Achondrite
Geology
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 10869379
- Volume :
- 47
- Database :
- OpenAIRE
- Journal :
- Meteoritics & Planetary Science
- Accession number :
- edsair.doi...........6fc2e9005878fea03e8b8ff9822b9c9a