Investigating the Shallow to Mid-Depth (>100–300 °C) Continental Crust Evolution with (U-Th)/He Thermochronology: A Review
Round 1
Reviewer 1 Report
Investigating the shallow to mid-depth (>100-300°C) continental crust evolution with (U-Th)/He thermochronology: A Review
Gautheron et al. review and summarize the major advancements in (U-Th)/He dating methods in the past 20 years including: 1) high-temp thermochronometers for typical phases of igneous and metamorphic rocks (e.g., zircon and titanite) or mafic and ultramafic rocks (e.g., magnetite); and 2) a better understanding of how radiation damage affects He diffusion and retention for (U-Th)-poor and -rich minerals. Gautheron et al. present how this information combined with low-temp results and previously established methods can be useful as inputs to constrain different modelling to evaluate different thermal histories for the rocks/minerals in question. The combination of these approaches allows for a much better understanding of complex processes involved in crustal evolution.
Before I comment further, I want to briefly describe my experience in the field of (U-Th)/He dating: I have performed single crystal dating using the (U-Th)/He method on zircon, apatite and abraded titanite, all in association with hypervelocity impact cratering events. As a result, I have experience with 1) partial resetting of pre-existing grains; 2) crystals grown in impact melt sheets; 3) intrasample date variability/data dispersion; and 4) radiation damage in metamorphosed titanite (in the central uplift of the Manicouagan Impact structure). However, I don’t have any experience with the modeling methods described in this paper (HeFTy, QTQt, PECUBE, RDAAM, etc.), but I find the material presented to be very interesting and well thought out.
This paper is very well written with excellent attention to detail and readability. I am pleasantly surprised by how well edited this manuscript is. The review of the (U-Th)/He method is complete and well cited and the organization of information is logical and easy to follow. I really like the advice against developing weighted means from overly dispersed data sets in the 3rd conclusion/recommendation!
In my opinion, this manuscript should be published after some very minor corrections.
Requested Corrections/Considerations:
Line 246 (add “a”): itself a function of the thermal
Line 383 (remove “s”): represents a significant
Line 593 (consider rewording): be reconstructed in forwards modelling
Line 614 (consider rewording - of the study area?): AHe ages the study area fall outside
Line 639 (change first interpretation): can add valuable information for the interpretation of
Line 644 (make plural): Recommendations
Line 707 (consider rewording): show good promise for new applications and should be watched closely
END – 4/4/2022
Author Response
Dear reviewer,
Thanks for the constructive feedback and suggestions
We corrected all the raised point in the manuscript and corrections were marked in the ms and a complete editing of the manuscripts has been performed.
Sincerely,
Cécile Gautheron on behalf of the co-authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
It is a good review paper with rigid structure, refined language, and novel content. It quotes important and recently published articles in this field, gives good comments and suggestions for future work. It will benefit greatly not only to methodological researchers but also to geological application researchers in this field, so more people will pay attention to this amazing new field.
Apatite has been the main mineral for (U-Th)/He dating, focusing on exhumation and burial processes in the upper levels of continental crust, the development of He dating for typical phases of igneous and metamorphic rock (e.g. zircon and titanite) or mafic and ultramafic rocks (e.g. magnetite) has geological applications at a higher temperature. The successful applications are based on the study of Helium diffusion and retention by radiation damage. The authors review some significant research processes of helium diffusion studies and related applications at shallow to middle-crustal depths. And also the authors provide many useful recommendations for data interpretation and thermal history determination for Helium dating. Many readers will benefit greatly from these suggestions. I strongly recommend that this paper will be published in this journals.
Some suggestions for the authors:
Line 33 recoil damage or radiation damage，which one is better for keywords?
Line 228, 229, 230 the number ****/g, some symbols appear abnormal.
Line 163, 300 et al. The symbol display of the diffusion parameter is abnormal.
Line 342, 343 what does ‘analytical 1 error’ mean? Does it mean ‘1 standard error‘?
Fig 7 titles display three font styles.
Author Response
Dear reviewer,
Thanks for the constructive feedback and suggestions
We corrected all the raised point in the manuscript, modified a keyword, corrected all the small edits mistakes with symbols, corrected the standard error and modified Fig 7. In addition, corrections were marked in the ms and a complete editing of the manuscripts has been performed.
Sincerely,
Cécile Gautheron on behalf of the co-authors
Author Response File: Author Response.pdf
