U th he dating of apatite a potential thermochronometry validating microsoft office license
2009), e U and grain age should have a positive correlation if the dispersion is derived from radiation damage (cf Fig. Within samples, we adopted grain ages that overlapped with the other grain ages within ±3σ to calculate the weighted mean age of each sample (Table 3; Fig. For A02-ST03, grain ages present a cluster ranging 80–50 Ma, except for one grain yielding an age of ~225 Ma.
b Topographic cross-sections across the study area.
Simultaneous measurement of age standards, namely Durango apatite and Fish Canyon Tuff zircon, yielded reasonable ages overlapping with the reference ages within ±1σ (Tables 2 and 3), indicating accuracy of the dating results. The vertical error bars denote the ±1σ, ±2σ, and ±3σ ranges.
Although most of the samples indicated reasonable reproducibility of the grain ages, a few samples showed age dispersion greater than expected from the analytical uncertainties and statistical errors (Tables 2, 3; Figs. Apatite and zircon He ages represent the integration of different parameters, such as, grain size (Farley 2000), possible zoning of the parent nuclides (Hourigan et al. The two horizontal red lines indicate the weighted mean age 95% confidence interval (CI) and −95% CI, respectively For apatite samples, grain ages generally reproduced reasonably well (Fig.
Apatite grains were outgassed under vacuum at ~900 °C for 5 min, by using a Coherent Quattro FAP 820 nm diode laser with fiber-optic coupling to the sample chamber.
Helium content was determined by isotope dilution against a pure He standard and measured using a Balzers quadrupole (Prisma QMS 200) mass spectrometer.