Standardless fission-track ages of the IUGS age standards

Duluth Complex apatites: Age reference material for LA–ICP–MS‐based fission‐track dating

“…Concerning the LA analysis spots, a depth of ~ 8 μm, which is equivalent to half a length of FTs in apatite, is recommended for FT dating (Figure S3). As U standards, apatite samples analysed by the EDM technique (Enkelmann, Jonckheere, & Ratschbacher, ; Iwano, Danhara, & Hirata, ; Iwano et al, ; Jonckheere, Van den haute, & Ratschbacher, ), isotope dilution ID–ICP–MS or LA–ICP–MS (Soares, Mertz‐Kraus, Guedes, Stöckli, & Zack, ) were used.…”

“…Separated apatite minerals were mounted with epoxy for dating and track‐length measurement, and polished with diamond pastes. A 0.1 M HNO 3 etchant at 20°C (Iwano & Danhara, ) was adopted for the absolute age calibration based on the same condition of Iwano et al (); Iwano et al (). To reveal spontaneous‐track distributions for each sample, optimal etching time varied from 3 min for FC1 apatite to 6 min for Durango apatite probably due to effects of alpha damage and/or chemical composition.…”

“…To reveal spontaneous‐track distributions for each sample, optimal etching time varied from 3 min for FC1 apatite to 6 min for Durango apatite probably due to effects of alpha damage and/or chemical composition. IUGS apatite standards Fish Canyon Tuff, Durango Apatite and Mount Dromedary Banatite were used for comparison, most samples of which had been analysed by EDM with certified absolute ages and uranium contents (Iwano et al, ; Iwano, Danhara, & Hirata, ). Track counting employed a touch‐screen monitor (Danhara & Iwano, ).…”

“…The LA–ICP–MS instrumentation and operational settings are described in Table S2. The matrix‐matched U standard used was Durango apatite containing 14 (± 0.4) ppm U (Iwano et al, , ).…”

“…where t is the FT age (Ma), λ is the alpha decay constant of 238 U (1.55125 × 10 –10 yr –1 ; Jaffey, Flynn, Glendenin, Bentley, & Essling, ), λ f is the spontaneous fission decay constant of 238 U (8.5 ± 0.1 × 10 –17 yr –1 ; Holden & Hoffman, ), ρ s is the FT areal density on an internal mineral surface, 238 U is the U content in ppm and C is a constant combining 11 atomic, physical and nuclear parameters, including atomic mass, the Avogadro number (6.022 × 10 23 ), apatite density (3.2 g/cm 3 ); C = 1.59 × 10 –13 for apatite (see Table S3 for details) (Danhara & Iwano, ; Iwano et al, ).…”