Preprints
https://doi.org/10.5194/gchron-2020-35
https://doi.org/10.5194/gchron-2020-35

  14 Nov 2020

14 Nov 2020

Review status: this preprint is currently under review for the journal GChron.

Simulating sedimentary burial cycles: Investigating the role of apatite fission track annealing kinetics using synthetic data

Kalin T. McDannell1 and Dale R. Issler2 Kalin T. McDannell and Dale R. Issler
  • 1Department of Earth Sciences, Dartmouth College, Hanover NH, 03755, United States
  • 2Geological Survey of Canada, Natural Resources Canada, Calgary AB, T2L 2A7, Canada

Abstract. Age dispersion is a common feature of apatite fission track (AFT) and apatite (U-Th)/He (AHe) thermochronological data and it can be attributed to multiple factors. One underappreciated and underreported cause for dispersion is variability in apatite composition and its influence on thermal annealing of fission tracks. Here we investigate, using synthetic data, how multikinetic AFT annealing behaviour (defined using the rmr0 parameter) can be exploited to recover more accurate, higher resolution thermal histories than are possible using conventional interpretation and modelling approaches. Our forward model simulation spans a 2 Gyr time interval with two separate heating and cooling cycles and generates synthetic AFT and AHe data for three different apatite populations with significantly different annealing kinetics. The synthetic data are used as input for inverse modelling (Bayesian QTQt model) that attempts to recover thermal history information under various scenarios. Results show that essential features of the dual peak thermal history are captured using the multikinetic AFT data alone, with or without imposed constraints. Best results are achieved when the multikinetic AFT data are combined with the AHe data (using varying rmr0 values from the AFT data for the He radiation damage model) and constraints are included. In contrast, a more conventional monokinetic interpretation that ignores multikinetic AFT behaviour yields incorrect thermal solutions that fail to adequately reproduce all the data. The AFT data are reproduced well but the AHe data are not. Under these conditions, incorporation of constraints can be very misleading and fail to improve model results. In general, a close fit between observed and modelled parameters is no guarantee of a robust thermal-history solution if data are incorrectly interpreted. For the case of overdispersed AFT data, it is strongly recommended that elemental data be acquired to investigate if multikinetic annealing is the cause of the age scatter. A future companion paper will explore multikinetic AFT methodology and application to detrital apatite samples from Yukon, Canada.

Kalin T. McDannell and Dale R. Issler

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Kalin T. McDannell and Dale R. Issler

Kalin T. McDannell and Dale R. Issler

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Short summary
We generated a synthetic dataset applying published kinetic models and distinct annealing kinetics for the apatite fission-track and (U-Th)/He methods using a predetermined thermal history. We then tested how well the true thermal history could be recovered under different data interpretation schemes and geologic constraint assumptions using the Bayesian QTQt software. Our results demonstrate that multikinetic data increase time-temperature resolution and can constrain complex thermal histories.