New constraints on ages of glasses proposed as reference materials for fission-track dating

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Data

2007-06-01

Autores

Laurenzi, Marinella A.
Balestrieri, Maria Laura
Bigazzi, Giulio
Neto, Julio C. Hadler
Iunes, Pedro J.
Norelli, Pio
Oddone, Massimo
Osorio Araya, Ana Maria
Viramonte, Jose G.

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Título de Volume

Editor

Wiley-Blackwell

Resumo

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.

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Palavras-chave

fission-track dating, (40)Ar/(39)Ar dating, natural glasses, age standards

Como citar

Geostandards and Geoanalytical Research. Malden: Wiley-blackwell, v. 31, n. 2, p. 105-124, 2007.