Genesis of Chaxi Gold Deposit in Southwestern Hunan Province, Jiangnan Orogen (South China): Constraints from Fluid Inclusions, H-O-S-Pb Isotopes, and Pyrite Trace Element Concentrations

Round 1

Reviewer 1 Report

Dear authors

I have gone through the paper. The comments are given as followings:

The authors present fluid inclusions, and H-O-Pb-S isotopes to address ore genesis of the Chaxi Au deposit. These data support most interpretation, and their discussion do make sense, thus, the it could be a valuable contribution to Minerals. There are some key adjustments that need to be made to the manuscript prior to acceptance. For example, discussion on deposit type is confusing, the Chaxi deposit is neither similar to Carlin nor epithermal Au deposits. The proposed intracontinental reactivation type is also difficult to reconcile, because no re-activated faults filled by later mineralization can be observed in the Chaxi deposit. Therefore, discussion on this issue should be remained open.

 

Abstract

 

1. tetrahedrite is sulfosalt rather than sulfide

2. The alteration includes beresite and carbonate? Confusing. These are rocks rather than hydrothermal alteration.

3. The Chaxi gold mineralization shares certain geological and geochemical similarities with typical orogenic, epithermal and Carlin-type gold deposits, and is best classified as an ‘‘intracontinental reactivation” type closely related to regional folding and shearing deformation, as proposed for many other gold deposits in the Jiangnan Orogen. This should be kept to be consistent with the discussion section.

 

Introduction

 

Various metallogenic models have been proposed for these Au deposits in the JOB, such as the magmatic-hydrothermal related model proposed for the Gutaishan and the Yuhengtang deposits by Li et al. (2016, 2018, 2019, 2021). These four articles should be cited.

 

Geological background

 

1. In Fig.1 the Yuechengling-Maoershan granite intrusions were mainly emplaced during Paleozoic rather than Neoproterozoic. In fact, they are composed intrusions composed of Paleozoic and Triassic ages.

2. Native gold is mostly irregular granular, fine-vein, and honeycomb-shape (Fig. 4). Visible gold is mainly coarse-grained and minor fine-grained electrum is hosted in the sulfides. CONFUSING. Reworded.

 

Results

 

1. H-O-S-Pb isotope should be stage-based, and stage information must be added in tables and figures.

2. These vary large temperature ranges is problematic. Caution should be taken when handling the data as I propose many secondary inclusions were analyzed.

3. Gold concentrations detected by EPMA method is unreliable. Discussion on associated sentences should be removed from the text.

4. References listed in Fig. 11 legend should be given in the reference list.

 

Discussion

 

1. Quartz may have precipitated from a homogeneous fluid source? ore-forming fluids was magmatic water and mixed with meteoric water during water-rock interaction, with involvement of the minor metamorphic component? Confusing.

2. Sulfur isotopic composition of sedimentary pyrite from the Lengjiaxi Group have provided in Li et al. (2018, 2021). Comparison between the Gutaishan, Yuhengtang and Chaxi should be added.

3. Lead from mantle. This is interesting and more explanation is needed.

4. 5.3. Sulfide major element compositions should be deleted.

5. Discussion on the Carlin and epithermal should be removed. And discussion on ore genesis should remain an open topic as data presented here is not straightforward enough.

 

Add some references

 

Li W, Xie GQ, Zhang ZY and Zhang XK. Constraint on the genesis of Gutaishan gold deposit in central Hunan province: Evidence from fluid inclusion and C-H-O isotopes (in Chinese with English abstract)

Li Wei, Cook Nigel, Xie Guiqing, Mao Jingwen, Ciobanu Cristiana, Fu Bin. 2021. Complementary textural, trace element and isotope analysis of sulfides constrain ore-forming processes for the slate-hosted Yuhengtang Au deposit, South China. Economic Geology, 116（8）: 1825–1848.

Li Wei, Cook Nigel, Xie Guiqing, Mao Jingwen, Ciobanu Cristiana,·Li Jianwei, Zhang Zhiyuan. 2019. Textures and trace element signatures of pyrite and arsenopyrite from the Gutaishan Au–Sb deposit, south China. Mineralium Deposita, 54（4）: 591–610.

Li Wei, Xie Guiqing, Mao Jingwen, Zhang Zhiyuan, Fu Bin, Lu Song. 2018. Muscovite 40Ar/39Ar and in situ sulfur isotope analyses of the slate-hosted Gutaishan Au–Sb deposit, south China: Implications for possible Late Triassic magmatic-hydrothermal mineralization. Ore Geology Reviews, 101: 839–853.

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Reviewer 2 Report

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Round 2

Reviewer 1 Report

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Reviewer 2 Report

Despite the fact that the authors agreed with a gross error in the The Figure 6 (Mineral paragenetic sequence for the Chaxi gold deposit) such as absence of quartz, the error was not corrected in the revised version of the article. It should be corrected.

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Round 3

Reviewer 1 Report

Dear author

It is OK for acceptance from my side. Before print it is necessary to delete reference 24 since it is the same with 32.

Best regards, Jingwen Mao

Author Response

Thank you, we have deleted the Ref. 24 and revised the sequence of related Ref.

Best regards

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