Zircon U–Pb Ages and Geochemistry of Granitoid in the Yuejinshan Copper–Gold Deposit, NE China: Constraints on Petrogenesis and Metallogenesis

Round 1

Reviewer 1 Report

Dear Authors,

The paper is properly organized and the new results and discussion are correctly integrated with previous information. I suggest Minor revisions.

Best regards

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report

The paper proposed by the authors focuses on U-Pb dating on zircons and on the geochemical and petrological characterization of Mesozoic granitoids linked to a copper-gold mineralized district in north-east China. Geochronology and whole-rock geochemistry allow to reconstruct the timing and the plate subduction geodynamic context in which the magmatic activity developed and (albeit in quite speculative terms) to define the chronology of metallogenic events. The structure of the work and the analytical methods used are certainly adequate to correctly develop the geochronology of the intrusions and the petrological topic, however, various problems must be highlighted that affect entire parts of the manuscript and require an in-depth revision; the most important in particular concern the lack of correspondence between text, figures and captions of the figures which makes an entire paragraph (whole-rock geochemistry) almost illegible. For the same reasons, the discussion must be revised in several parts. References in the text do not follow the recommendations for Minerals. English is generally fair, although it can be improved. See the attached file for my (numerous) annotations.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Wang and co-authors,

You investigate the geochemical features and temporal timeline of a series of igneous intrusive rocks from a copper-gold deposit in NE-China. You aim to decipher the tectonic setting of magma origin, generation and emplacement together with its timing, to better understand the potential copper-gold prospect.

Your geochemical whole rock data appear sound and of quality, supporting your interpretation concerning tectonic setting. However, you propose that two distinct melts mix to form the intrusive bodies, one with a mantle origin and one with a crustal origin. I beleive it would be more reasonable to assume a subduction realted melt generation with subsequent crustal interaction and assimilation, coupled with subtantial fractioantion. I would encourage you to perform crystallisation fractionation models (e.g. Rayleigh) to estimate the extent of melt modification. Your geochemical proxies presented and discussed would align well with such. One considerable flaw is that some of your ocncentrations are reported without units. This has to be rectified, otherwise the manuscript can only be rejected. I would encourage you to use the wt%, ppm, ppb or g/kg, mg/g etc. terminology.

As for the interpretation of your in-situ zircon U-Pb data, the majority seem plausible. However, you neglect some aspects which may help understand some of the more complex data. For example, sample YJS-2 shows clear evidence for Pb-loss due to e.g. zircon metamictisation. In your honest display of thoughts on the discussion you seem to believe that this is primarily a function of poor laboratory performance, I invite you to study some more literature on the topic. Some recommended articles for your study could be https://doi.org/10.1130/G46312.1 or https://doi.org/10.1016/j.chemgeo.2015.02.028  or https://link.springer.com/article/10.1007/BF01173760 . I do believe that you are not rigorous enough in your selection of analyses included in your weighted mean ages, at least your figures make me believe so. in e.g. Fig. 7a and b, you seem to include analyses that could be interpreted as inherited core ages and metamict pb-loss in you weighted mean, which inflates the MWSD. Try to refine these ages by a more selective appraoch to find the yougnest population of zircons. Start by rejecting those analyses that are discordant and those which are to old (e.g. when the odler ages do not overlap with the weighted mena age. Currently, your age interpretation is not convicing to me. Please make your primary and secondary standard analyses available. Your data tables seem to contain the most relevant data, but consult the paper by Horstwood on the community guidline for LA-ICP-MS data reporting to improve it (https://doi.org/10.1111/j.1751-908X.2016.00379.x).

introduction and Geological setting:

There is some redundant information reported in these paragraphs. the first paragraph of the geological setting may be delted, since it is reported in the Introduction already. A larger scale map showcasing the location of the study area and the most important geographic and geological features would be beneficial.

methodology:

parts of the methodlogy section are difficult to follow, try to be more concise and explain e.g. why you mention 29Si and its role in your monitoring and data reduction.

what is your flux medium for the WR analyses, what is the ratio of flux to sample? This is critical information and necessary.

Results:

You make some interpretations in your results already. Restrict yourself to reporting the data only, so the reader can study it un-biased. Your interpreations follows later anyways, which creates redunances and make the article unnecessarily longer.

general remarks:

There is a larger number of formatting mistakes, which are easy fixes. Please carfully read your manuscript and keep reference formats consistent. the grammar sometimes is poor, but overall good.

Overall, the manuscript looks promising and should be reconsidered after you have thoroughly revised it, corrected inconsistentcies and abiguities.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

All the main problems highlighted in the first version of the text have been revised and corrected by the Authors and the paper seems to me compressively much improved, also with regard to English. 

Author Response

Dear reviewer, thank you for your valuable comments on the paper. 

Reviewer 3 Report

Dear Wang and co-authors,

thank you for submitting a revised version of the manuscript. After some more (minor) adjustments, I think this is acceptable, but in some places still controversial.

There is still units missing, such as in line 100-101 where you refer to grade, which is still unit-less.

In the results section of the zircon U-Pb you already make interpretation, this should be saved for the discussion (line 181-184). Same applies for lines 193-194 and more. 

Line 196 "Due to zircon metmorphic overgrowth,..."

Line 201 (suggestion) "which were initially interpreted as crystallization age of the granite porphyry, but later revised to be inacurrate."

Lines 223-224 lacks units: "The contents of Th and U are 187.73×10-6 to 2830.67×10-6 and 391.22×10-6 to 2923.92×10-6 "is this ppm?

Figure 5: You have revised your selection of zircon for the age interpretation, which improved the MSWD, but the figure only reflects this in the fine number print. please mark out rejected analyses in the age interpretation, as you have done previously in red coloring.

Line 244-245 lacks units (ppm?)

Line 297-304 please provide uncertainty estimates on the ages 114 Ma, 116 Ma, 124 Ma, 111 Ma and so on, where possible.

Line 337 - 341 You speak about the Yuejinshan granitic intrusion to be homogenous/similar in composition. In the following you speak about granitoids which are distinct. You must specify which granitoids, else this is highly confusing and contradicting the previous sentence. If you mean that the granitoids and granite are discussed distinctly, this has to be made clear. This would be surprising however, if they both belong to Yuejinshan.

Your discussion on the petrogenesis of the intrusive rocks remains difficult to follow. Given the geochemical trends in Figure 9, I am surprised to hear that fractional crystallisation does not appear to have any significant role.

Author Response

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Author Response File: Author Response.pdf