41Ca, 26Al, and 10Be in lunar basalt 74275 and 10Be in the double drive tube 74002/74001

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dc.contributor.authorFink, Den_AU
dc.contributor.authorKlein, Jen_AU
dc.contributor.authorMiddleton, Ren_AU
dc.contributor.authorVogt, Sen_AU
dc.contributor.authorHerzog, GFen_AU
dc.contributor.authorReedy, RCen_AU
dc.date.accessioned2021-10-28T04:40:21Zen_AU
dc.date.available2021-10-28T04:40:21Zen_AU
dc.date.issued1998-07en_AU
dc.date.statistics2021-10-25en_AU
dc.description.abstractWe report depth profiles of the cosmogenic radionuclides 10Be, 26Al, and 41Ca in the titanium-rich lunar basalt 74275. The 10Be profile is flat: 10Be activities are confined to a narrow range between 9.6 and 11.2 dpm/kg but are nonetheless consistent with a small contribution of about 1–2 dpm/kg from solar cosmic rays. The 26Al profile shows the steep decrease with increasing depth that is characteristic of nuclides whose production is dominated by solar cosmic rays. 41Ca activities decrease from about 22 dpm/kg at the surface to a minimum of ∼9 dpm/kg at a depth of 4.7 g/cm2 and then increase to ∼11 dpm/kg at a depth of 15.8 g/cm2. The sharp decrease near the surface identifies for the first time production of 41Ca by solar cosmic rays. We also report 10Be measurements for six samples from lunar core 74002/1. The 10Be activities range from approximately 8 to 14 dpm/kg. We model the production of 10Be, 26Al, and 41Ca in lunar rock 74275 by including published data that indicate a long exposure to galactic cosmic rays at a depth of 140 g/cm2 followed by one at the surface lasting 2.8 Ma. Cosmogenic radionuclide production by galactic cosmic rays, and, in the case of 41Ca, by thermal neutrons is estimated from published measurements and semi-empirical calculations. Our model includes a new calculation of production rates due to solar cosmic rays and incorporates recently published cross section measurements. Although many parameterizations of the flux of solar energetic particles give acceptable fits to the experimental data for 74275, we prefer a best fit obtained for 10Be and 26Al alone, which incorporates an erosion rate of ∼2 mm/Ma, a rigidity of 100 MV, and a 4π flux of protons with energies greater than 10 MeV of 89 cm−2 s−1. For 41Ca alone, the corresponding values are 2 mm/Ma, 80 MV, and 198 cm−2 s−1. The differences between the two sets of parameters may reflect uncertainties in the calculations of 41Ca production or a secular change in the solar cosmic ray flux. Calculations for a slab and for a hemispherical knob with a radius of 23 cm yield similar results. © 1998 Elsevier Science Ltd.en_AU
dc.identifier.citationFink, D., Klein, J., Middleton, R., Vogt, S., Herzog, G. F., & Reedy, R. C. (1998). 41Ca, 26Al, and 10Be in lunar basalt 74275 and 10Be in the double drive tube 74002/74001. Geochimica et Cosmochimica Acta, 62(13), 2389-2402, doi:10.1016/S0016-7037(98)00134-3en_AU
dc.identifier.issn0016-7037en_AU
dc.identifier.issue13en_AU
dc.identifier.journaltitleGeochimica et Cosmochimica Actaen_AU
dc.identifier.pagination2389-2402en_AU
dc.identifier.urihttps://doi.org/10.1016/S0016-7037(98)00134-3en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12165en_AU
dc.identifier.volume62en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectRadioisotopesen_AU
dc.subjectLunar materialsen_AU
dc.subjectThermal neutronsen_AU
dc.subjectProtonsen_AU
dc.subjectExperimental dataen_AU
dc.subjectIsotopesen_AU
dc.subjectTitaniumen_AU
dc.subjectCosmic ray fluxen_AU
dc.subjectCosmic radiationen_AU
dc.title41Ca, 26Al, and 10Be in lunar basalt 74275 and 10Be in the double drive tube 74002/74001en_AU
dc.typeJournal Articleen_AU
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