Origin of the Xulaojiugou Pb–Zn Deposit, Heilongjiang Province, NE China: Constraints from Molybdenite Re–Os Isotopic Dating, Trace Elements, and Isotopic Compositions of Sulfides

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript provides valuable geochronological (Re-Os) and geochemical (S isotopes, trace elements) data to resolve conflicting ages and clarify the genesis of the Xulaojjugou Pb-Zn deposit. Its linkage to Jurassic magmatism and Paleo-Pacific subduction enhances understanding of regional metallogeny in NE China. However, the broader implications for exploration in the Xing’an-Mongolia Orogenic Belt could be emphasized further.

1. Data and Methods
   Analytical methods (Re-Os, LA-ICP-MS, EPMA) are well-described, and quality control using reference materials (e.g., GBW04435, NIST 610) is appropriately noted. However, details on laser ablation parameters (e.g., spot size for sulfur isotopes) and calibration standards for trace elements should be expanded for reproducibility.

2. Age Discrepancies and Re-Os Reliability
   The Re-Os age (184.6 ± 3.0 Ma) is critical for resolving prior conflicting U-Pb ages. However, the manuscript should explicitly discuss why Re-Os dating (directly dating molybdenite) is more reliable than zircon U-Pb ages (which date magmatic crystallization, not mineralization). A comparative analysis of previous age data in Table format would strengthen this section.

3. Sulfur Isotope Interpretation
   The narrow δ³⁴S range (4.7–5.83‰) is convincingly attributed to a magmatic source. However, the slight difference between sphalerite (mean 5.63‰) and galena (mean 5.35‰) should be discussed in terms of equilibrium fractionation. Additionally, potential contributions from mantle-derived fluids or mixing with crustal sulfur are not addressed.

4. Trace Element Thermometry
   The use of Zn/Cd (mean 220.5) and Ga/In ratios to infer mesothermal conditions (248–262°C) is supported by references, but citing specific experimental studies  would bolster the argument. A discussion of uncertainties in these empirical models is also needed.

5. Genetic Model and Petrographic Evidence
   The skarn classification is well-supported by mineral assemblages and trace element signatures. However, the text lacks detailed petrographic descriptions of skarn minerals (e.g., garnet, pyroxene) and their spatial zonation. Including a schematic model illustrating the relationship between magmatism, skarn alteration, and mineralization would enhance clarity.

6. Figures: Figure 7 (histogram) is referenced before Figure 6 (isochron plot) in the text. Ensure all figures/tables are cited in sequential order.

7. Regional Tectonic Context
   The link to Paleo-Pacific subduction is plausible but requires deeper integration with regional studies. For example, how does the 184 Ma age correlate with subduction-related magmatic pulses in NE China? Citing recent geodynamic models would strengthen this section.

8. Paragenetic Sequence
   Describe how cross-cutting relationships or mineral textures (e.g., replacement features in Figure 4) validate the sequence.

9. Update references to include recent studies on skarn deposits (post-2020 works).

The manuscript presents robust data and a coherent narrative but requires minor revisions to maximize its impact.

Comments on the Quality of English Language

Language: Awkward phrasing (e.g., "vocanic" → volcanic).

Check carefully the grammers and improve language clarity through professional editing.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Here is my review of the Manuscript ID: minerals-3511965 – entitled: Origin of the Xulaojiugou Pb-Zn deposit, Heilongjiang Province, NE China: Constraints from molybdenite Re-Os isotopic dating and in-situ trace elements and isotopic compositions of sulfides and isotopic compositions of sulfides, by Gan Liu et al. Some new data on molybdenite Re-Os age, sulfur isotope composition of sulfides and major and trace contents for a Pb-Zn deposit are provided, to constrain the metallogenic age, ore-forming processes and sources of ore-forming materials. In my opinion, this manuscript is well written and organized and can be published in the MINERALS, after minor revision.

Comments

- Title: Origin of the Xulaojiugou Pb-Zn Deposit, Heilongjiang Province, NE China: Constraints from Molybdenite Re-Os Isotopic dating and In-Situ Trace Elements and Isotopic Compositions of Sulfides and Isotopic Compositions of Sulfides Proposed change to: Origin of the Xulaojiugou Pb-Zn Deposit, Heilongjiang Province, NE China: Constraints from Molybdenite Re-Os Isotopic dating, trace element and in situ sulfur isotope analysis.

- Figure 5. Mineral paragenesis for the Xulaojiugou Zn-Pb deposit. Please check again the term Grammite and provide alternative term.

- Figure 7. Histogram of δ34S values hydrothermal sulfides from Xulaojiugou Pb-Zn deposit. Please explain the symbols Gn and Pb. Are they correct abbreviations of minerals?

-Table 5. Trace element compositions(ppm) of sphalerite analyzed by LA-ICP-MS from the Xulaojiugou Pb-Zn deposit. Please, round off trace element values, because the analytical method used does not give you the possibility to express the results with such detail. For example, Mn 2460-44200 ppm, instead Mn 2464-44210 ppm, 350-870 ppm Se instead 352-871 ppm Se; 0.6-670 ppm Pb, instead 0.63-673 ppm Pb, etc. The number of digits given in the results must always be adjusted to analytical uncertainty.

In general, both terms content and concentration are used through the text. I would suggest the term content for solids since the term concentration is commonly used for liquids.

Figure 9. Zn/Cd ratios (a) and Fe/Zn ratios (b) for sphalerites from the Xulaojiugou Pb-Zn deposit. My suggestion is: Plot of Zn vs Cd (a) and……

Figure 10. In vs. Ge content of local trace elements In Xulaojiugou Pb-Zn deposit and other different …….. Again, Plot of In vs Ge…

- Highlights are missing. Please, add 4-5 short highlights, showing your new contribution.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

No comments

Author Response

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Author Response File: Author Response.pdf