Review of Short communication concerning experimental factors affecting fission-track counts in apatite

Aslanian C, Jonckheere R, Wauschkuhn B and Ratschbacher L.

This manuscript reports two different experiments on track counting in Durango apatite and uses a recent etch model to explain how the track counts change in different observation criteria. The first experiment is track count and etch pit measurement analysis of fossil tracks in three different sections of Durango apatite; the second one is a further counting analysis of unannealed, annealed, induced and fossil tracks in c-axis parallel section of Durango apatite.

The text is well written, the figures are clear, the tables and supplementary file contain almost all the analysis data, excluding etch pit/track opening length measurements.

Analyst bias and track selection criteria have significant impact on fission track data analysis and ultimately affect the modeling results. After adding suggested figures, a new table and supplementary data for etch pit/track opening lengths and rearranging the format from short communication to regular manuscript (with more discussion and conclusion part), this work should be resubmitted as a regular manuscript.

Please find the specific comments and suggestions in annotated pdf.

Regards,

Murat Tamer

October 2, 2021

Comments to the Authors

This paper reported experiments concerning the effects of grain orientation, polishing, etching and observation on fission-track counts in apatite. The paper also showed results were systematically obtained and theoretically explained in the framework of a recent etch model. I think this is an article worth reading for FT researchers, therefore my recommendation would be publish this paper as a short communication. The following comments should be further developed for publication.

Fig.1

• Explanation for regression line is needed in the caption.

Table 1

• The track densities of B00 and B60 are clearly smaller than those of P00. Is this a difference due to U concentration? If not, which one is closer to the true track density?

Fig.5

• I am amazed at the number of track-shaped pits in the reflected image. Of course the authors counted them as a fission track. What are the criteria for track identification? Please describe them for each (TL and RL). If there are several etch pits detected by apatite that is totally annealed at 450 ° C, I think it can be set as the minimum noise to identify (count) fission tracks. Additional images of totally annealed samples are needed and helpful.

Fig.6

• Between 0.7 and 1.0, track density for RL is higher than TL. This means that the track identification criteria are different. Please describe the identification criteria for minimum track, at least.

Table 3 and Figure 6

• Are there data at 450 ° C for total annealing?  I am very concerned about the density of track-like defects.