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Type: Artigo de periódico
Title: New constraints on ages of glasses proposed as reference materials for fission-track dating
Author: Laurenzi, MA
Balestrieri, ML
Bigazzi, G
Neto, JCH
Iunes, PJ
Norelli, P
Oddone, M
Araya, AMO
Viramonte, JG
Abstract: New analyses have been performed in order to enhance the data-set on the independent ages of four glasses that have been proposed as reference materials for fission-track dating. The results are as follows. Moldavite - repeated (40)Ar/(39)Ar age determinations on samples from deposits from Bohemia and Moravia yielded an average of 14.34 +/- 0.08 Ma. This datum agrees with other recent determinations and is significantly younger than the (40)Ar/(39)Ar age of 15.21 +/- 0.15 Ma determined in the early 1980s. Macusanite (Peru) -four K-Ar ages ranging from 5.44 +/- 0.06 to 5.72 +/- 0.12 Ma have been published previously. New (40)Ar/(39)Ar ages gave an average of 5.12 +/- 0.04 Ma. Plateau fission-track ages determined using the IRMM-540 certified glass and U and Th thin films for neutron fluence measurements agree better with these new (40)Ar/(39)Ar ages than the previously published ages. Roccastrada glass (Italy) - a new (40)Ar/(39)Ar age, 2.45 +/- 0.04 Ma, is consistent with previous determinations. The Quiron obsidian (Argentina) is a recently discovered glass that has been proposed as an additional reference material for its high spontaneous track density (around 100 000 cm(-2)). Defects that might produce "spurious" tracks are virtually absent. An independent (40)Ar/(39)Ar age of 8.77 +/- 0.09 Ma was determined and is recommended for this glass. We believe that these materials, which will be distributed upon request to fission-track groups, will be very useful for testing system calibrations and experimental procedures.
Subject: fission-track dating
(40)Ar/(39)Ar dating
natural glasses
age standards
Country: EUA
Editor: Wiley-blackwell
Citation: Geostandards And Geoanalytical Research. Wiley-blackwell, v. 31, n. 2, n. 105, n. 124, 2007.
Rights: fechado
Identifier DOI: 10.1111/j.1751-908X.2007.00844.x
Date Issue: 2007
Appears in Collections:Unicamp - Artigos e Outros Documentos

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