Premium
Electrodynamic Disaggregation: Does it Affect Apatite Fission‐Track and (U‐Th)/He Analyses?
Author(s) -
Giese Jörg,
Seward Diane,
Stuart Finlay M.,
Wüthrich Eliane,
Gnos Edwin,
Kurz Daniel,
Eggenberger Urs,
Schreurs Guido
Publication year - 2010
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2009.00013.x
Subject(s) - apatite , fission track dating , muscovite , fission , geology , mineralogy , geochemistry , materials science , nuclear physics , paleontology , quartz , physics , neutron
Apatite fission‐track and (U‐Th)/He analyses require the liberation of intact idiomorphic apatite grains from rock samples. While routinely being carried out by mechanical methods, electrodynamic disaggregation (ED) offers an alternative approach. The high‐voltage discharges produced during the ED process create localised temperature peaks (10000 K) along a narrow plasma channel. In apatite, such high temperatures could potentially reduce the length of fission tracks, which start to anneal at temperatures > 60 °C, and could also enhance He diffusion, which becomes significant at 30–40 °C over geological time scales. A comparison of fission‐track analyses and (U‐Th)/He ages of apatites prepared both by mechanical (jaw crusher, disk mill) and ED processing provides a way of determining whether heating during the latter method has any significant effect. Apatites from three samples of different geological settings (an orthogneiss from Madagascar, the Fish Canyon Tuff, and a muscovite‐gneiss from Greece) yielded statistically identical track length distributions compared to samples prepared mechanically. Additionally, (U‐Th)/He ages of apatites from a leucogranite from Morocco prepared by both methods were indistinguishable. These first results indicated that during electrodynamic disaggregation apatite crystals were not heated enough to partially anneal the fission tracks or induce significant diffusive loss of He.