On the reproducibility of FT plateau-age determinations

On the reproducibility of FT plateau-age determinations

428 APPENDIX Abstract reproduced from the unrefereed volume "The Fourth International Fission-Track Dating Workshop." ON THE R E P R O D U C I B I ...

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428

APPENDIX

Abstract reproduced from the unrefereed volume "The Fourth International Fission-Track Dating Workshop."

ON THE R E P R O D U C I B I L I T Y OF FT P L A T E A U - A G E DETERMINATIONS G. POUPEAtL*'t" G. BIGAZZ],++§J. ('. HADLER,+ + A. FONSI';('A*! and M. t l ) ~ SIL\A* *Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud, 150, Rio de Janeiro, Brazil, t( NRS-ORSTOM, Paris, France, ~Raios Cosmicos, Cronologia, Altas Energias e Leptons, Instituto de Fisica, UNICAMP, Campinas, Brazil, ~CNR, Pisa, Italia and [Departamento de Geologia, Universidadc Federal do Rio de Janeiro, Brazil THERE IS presently no consensus about the way of calculating FT-ages. This comes in part from the lack of a sufficient data bank. In this work, we tested the experimental reproducibility of FT plateau-ages of apatites from metamorphic and plutonic rocks, obtained via the population method. For each sample, individual ages were measured from 5 to 20 different epoxy mounts, allowing both isothermal and isochronal plateau-ages to be calculated. For each age, the spontaneous and induced track densities were determined from ~>20 to nearly 100 crystals. According to the samples, from 4 to 7 observers performed age determinations. Model ages were calculated either as (i) isochron ages or (ii) weighted plateau-ages. The producibility of individual ages and model-age calculations will be discussed at the meeting.