4.3 Thermal modeling
Thermal histories predicted by QTQt satisfactorily reproduced AHe and
AFT data for each profile (Fig. 4). The ZHe thermochronometer has a wide
range of temperature sensitivity depending on the radiation damage of
the zircons (e.g., Ault et al., 2019). As our ZHe data show no clear
correlation between the single-grain ages and eU (Figs. S5-S7), we were
not able to reproduce the measured ZHe ages with the diffusion model
included in QTQt (i.e., Guenthner et al., 2013); thus the ZHe data were
excluded from the thermal modeling.
The thermal histories that best predict the AHe and AFT data from
inversion of the three age-elevation profiles indicate rapid cooling
immediately after the emplacement of intrusions
(~100°C/Myr); this was followed by residence of the
samples at temperatures of ~100°C from 15 to 6 Ma and
from 11 to 6 Ma, for the northern and the southern profiles,
respectively. The final cooling phase of the overall thermal history
initiated between ~6 and 5 Ma, and continues to the
present-day (~15°C/Myr). Although the Garanda profile
exhibits a similar early cooling history, the older, high-elevation AHe
ages cannot resolve the late Miocene cooling history.