Below is our responses (in italics) and the comments made by Reviewer 1 (not in italics). All of the changes described in our response have been made to the manuscript. We thank Reviewer 1 for their helpful comments and positive and enthusiastic feedback.

Response to Reviewer 1:

This is a really nicely written paper, with excellent levels of detail on the data collection, well-evidenced discussion and clear conclusions.  The manuscript sets out a sensible workflow and best practices for other researchers looking to date garnet by U-Pb methods. I enjoyed reading this and consider it an important contribution to the geochronology literature as well as resolving some of the longstanding debate around the timing and timescales of HP metamorphism in Oman.

Thank you for your positive comments!

I struggled to find many suggestions for improvements.  The following suggestions linked to line number are very minor suggested edits for clarity and precision. Overall the data appear sound, the figures clear and the writing of a very high standard.

Thank you again!

Line-by-line comments:

79 suggest re-wording sentence so that emphasis is on the scientific result and not on the author name via the citation (best practice not to start sentences with the citation)

Fixed.

119 I think there are also some data in the Warren thesis from a felsic tuff in the Hulw window that yield ca 290 Ma ages.

Added.

166 The dates themselves aren't spurious - they have been calculated correctly from the U-Pb ratios.  Suggest changing to "the dates are not geologically meaningful" or "have no meaning in a geological timeframe supported by other geochronometers"

Fixed.

285 the data for CWO21 are likely in the Warren thesis or in one of the Oman Warren et al publications.

The propagated uncertainty is the garnet Si contents between samples would bias the absolute trace element contents by less than 1 %. We have not adjusted the Si content used in this calculation as it is far below other sources of uncertainty and will not effect the data in any meaningful way.

355 suggest removing the "and" between "petrograpically and by EPMA"

We rewrote the sentence to “Micro-inclusions of zircon, as well as abundant inclusions of rutile, Ti-hematite, and ilmenite were observed by optical microscopy, EPMA imaging, and by LA-ICPMS mapping.”

357 Suggest the sentence that starts with "Here..." is redundant and could be deleted with no loss of information. Ditto line 397

Fixed.

512 Suggest "timing of garnet growth during eclogite facies metamorphism"

Fixed.

561 rather than "the growth/crystallisation of" eclogitic garnet

Fixed.

614 word missing between CWO21 and "that" - "suggest" or "show" maybe?

Fixed.

619 and elsewhere, suggest "presented or provided" rather than "given".

Fixed throughout.

685 Suggest slight amend: not precise enough to resolve outstanding questions about the timing of "garnet growth during" HP-LT metamorphism

Fixed.

710-715 I think it would also be useful to reflect on when in PT space garnet would start to grow along an idealised As Sifah thermobarometric path (the already-referenced Warren et al 2006 paper might help with that), and how long it commonly takes garnets to grow (2-10 Ma ish?)

Thank you for this suggestion. The garnet in reaction was calculated at 450 °C, just 50-100 °C below the peak T. Also, the 81-77 Ma Sm-Nd garnet ages are narrowly defined. If the core was very different from the rim and Sm is biased to the core, the ages would be biased to prograde metamorphism. However, the Sm-Nd ages overlap with the U-Pb matrix rutile ages. This suggests to me that the entirety of garnet growth occurred within 50 or so degrees of the peak. Therefore a gap of 10 million years or so must have occurred between the formation of the zircons and their inclusion into the garnet.

Below we provide detailed replies (in italics) to each comment by Reviewer 2 (non-italics). We thank Reviewer 2 for their helpful and insightful comments, as well as their positive feedback on our article. All of the described changes have been made to the manuscript. 

Online comment:

This is a timely and well-presented study of the influence of micro-inclusions in garnet and their impact on U-Pb ages using in situ LA ICP-MS techniques.  The study and concluding recommendations are broadly applicable to other potential low-U geochronometers where careful assessment of micro-inclusion suites is necessary prior to dating attempts.  The same logic applies to Lu-Hf of garnet where zircon micro-inclusions will skew Hf-isotope ratios (this should probably be highlighted in this study). 

Added a mention of zircon ablation during in situ Lu-Hf garnet geochronology to the introduction.

With a few small edits this should be a very impactful study that should be published.

Thank you very much for this comment.

Overall this is a carefully crafted study with clearly defined methodology and appropriate use of analytical tools, data reduction, and interpretation. 

Again, thank you.

 There several technical edits required that are highlighted in the attached annotated .pdf.  The figures and tables are of overall high quality (although the figure text is sometimes challenging to see). 

The figure text has been improved in several figures. Others we hope will be more easily read at their full size following type setting.

I note in the U-Pb isotope tables that there is no column for 204Pb and 204Pb is not really mentioned anywhere in the manuscript.  Considering the venue I'd recommend a statement about why the convention of recording net 204Pb is not used.

204Pb is not measured since it is not used in the isochron intercept age calculation using the Tera-Wasserburg approach. We also do not measure 202Hg.  Some Hg contamination exists in the gas and the 204Hg would need to be subtracted from the 204(Pb + Hg) signal. This is now mentioned in the text.  

Line by line comments (from the pdf):

11 - please check for consistent use of this term (italic vs. regular)

Fixed.

15 – I think you could argue that apatite should be in this list.

Added.

24 – indent please

Fixed.

41 – the earliest work was done on highly radioactive complex oxides like samarskite and pyrochlore

Fixed the next sentence. We do not aim to provide that historical of a review.

42 – This is not really historical (like previous sentence)...more like 'most contemporary' U-Th-Pb geochronology

Changed to contemporary.

86 – Small inclusions

Fixed.

90 – Note that the same observation was made by Hollinetz et al 2022 JMG in their study of micro-inclusions in chloritoid

Hollinetz was cited in the discussion, but we also cite it in the introduction now.

352 – some folks would not consider this small.  What was the motivation for choosing 33um? why not 10um if you really wanted to avoid inclusion? I assume this is a balance between spatial resolution and LOD?

We added the following sentence, “We found that 33-mm-diameter spot analyses are sufficiently small for inclusions to appear as sharp peaks in the time resolved data while maintaining sufficiently low limits of detection.”

513 – this is an odd usage to me.  Why not, 1) a reason and, 2) a tectonic...

Changed to using parentheses.

590 – check use of hyphen here...inconsistent use

Fixed here and throughout. At some point we changed from LA-ICP-MS to LA-ICPMS and did not catch every previous usage.

626 – superscripts please

Fixed.

724 – might want to be specific here in that FEG-SEM is really the ideal tool because of need to resolve inclusions down to sub-micron sizes.

Added.

749 – this might lead to rejection of all data in some labs with inefficient smoothing or noisy ablation cells.  Is there another way to write this?

We added that this approach should be taken as a last resort. Other approaches should normally be available (e.g., determining carefully the background U, Th, and Pb contents of the garnet in a clean area).

Figure comments (from the pdf):

Figure 3 – really hard to see the element labels.  To make this simpler couldn't you just put each element in the upper left (dark) corner and identify what elements are wt% vs. ug/g in the caption?

Fixed.

The masking of Pb map is strange...was Si or Al used to mask these?

The map was created using a gride of square spots instead of a raster. In addition to Pb, the regions at the grain edge appear high in Li, Na, Mg, Si, Ca, Sr, Nd, and Sm. Either the laser drilled through the edge of the garnet into matrix phases like epidote, chlorite, and mica, or drilled into these phases directly. This is now mentioned in the figure caption.