Cosmic-ray exposure history of the Norton County enstatite achondrite

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dc.contributor.authorHerzog, GFen_AU
dc.contributor.authorAlbrecht, Aen_AU
dc.contributor.authorMa, Pen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorKlein, Jen_AU
dc.contributor.authorMiddleton, Ren_AU
dc.contributor.authorBogard, DDen_AU
dc.contributor.authorNyquist, LEen_AU
dc.contributor.authorShih, CYen_AU
dc.contributor.authorGarrison, DHen_AU
dc.contributor.authorReese, Yen_AU
dc.contributor.authorMasarik, Jen_AU
dc.contributor.authorReedy, RCen_AU
dc.contributor.authorRugel, Gen_AU
dc.contributor.authorFaestermann, Ten_AU
dc.contributor.authorKorschinek, Gen_AU
dc.date.accessioned2021-12-21T00:11:34Zen_AU
dc.date.available2021-12-21T00:11:34Zen_AU
dc.date.issued2011-01-28en_AU
dc.date.statistics2021-11-09en_AU
dc.description.abstractWe report measurements of cosmogenic nuclides in up to 11 bulk samples from various depths in Norton County. The activities of 36Cl, 41Ca, 26Al, and 10Be were measured by accelerator mass spectrometry; the concentrations of the stable isotopes of He, Ne, Ar, and Sm were measured by electron and thermal ionization mass spectrometry, respectively. Production rates for the nuclides were modeled using the LAHET and the Monte Carlo N-Particle codes. Assuming a one-stage irradiation of a meteoroid with a pre-atmospheric radius of approximately 50 cm, the model satisfactorily reproduces the depth profiles of 10Be, 26Al, and 53Mn (<6%) but overestimates the 41Ca concentrations by about 20%. 3He, 21Ne, and 26Al data give a one-stage cosmic-ray exposure (CRE) age of 115 Ma. Argon-36 released at intermediate temperatures, 36Arn, is attributed to production by thermal neutrons. From the values of 36Arn, an assumed average Cl concentration of 4 ppm, and a CRE age of 115 Ma, we estimate thermal neutron fluences of 1–4 × 1016 neutrons cm−2. We infer comparable values from ε149Sm and ε150Sm. Values calculated from 41Ca and a CRE age of 115 Ma, 0.2–1.4 × 1016 neutrons cm−2, are lower by a factor of approximately 2.5, indicating that nearly half of the 149Sm captures occurred earlier. One possible irradiation history places the center of proto-Norton County at a depth of 88 cm in a large body for 140 Ma prior to its liberation as a meteoroid with a radius of 50 cm and further CRE for 100 Ma. © The Meteoritical Society, 2011en_AU
dc.identifier.citationHerzog, G., Albrecht, A., Ma, P., Fink, D., Klein, J., Middleton, R., Bogard, D. D., Nyquist, L. E., Shih, C.-Y., Garrison, D. H., Reese, Y., Masarik, J., Reedy, R. C., Rugel, G., Faestermann, T., & Korschinek, G. (2011). Cosmic-ray exposure history of the Norton County enstatite achondrite. Meteoritics & Planetary Science, 46(2), 284-310. doi:10.1111/j.1945-5100.2010.01154.xen_AU
dc.identifier.issn1945-5100en_AU
dc.identifier.issue2en_AU
dc.identifier.journaltitleMeteoritics & Planetary Scienceen_AU
dc.identifier.pagination284-310en_AU
dc.identifier.urihttps://doi.org/10.1111/j.1945-5100.2010.01154.xen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12602en_AU
dc.identifier.volume46en_AU
dc.language.isoenen_AU
dc.publisherWileyen_AU
dc.subjectAcceleratorsen_AU
dc.subjectMass spectroscopyen_AU
dc.subjectIsotopesen_AU
dc.subjectMeteoroidsen_AU
dc.subjectBeryllium 10en_AU
dc.subjectAluminium 26en_AU
dc.subjectCalcium 41en_AU
dc.subjectChlorine 36en_AU
dc.titleCosmic-ray exposure history of the Norton County enstatite achondriteen_AU
dc.typeJournal Articleen_AU
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