Origin and Evolution of Ore-Forming Fluid and Metallogenic Mechanism of the Baoshan Cu-Pb-Zn Deposit, South China: Constraints of Fluid Inclusion and C-H-O Isotopes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents the C-H-O isotopes and the characteristics of fluid inclusions of the Baoshan Cu-Pb-Zn deposit in the Southern Hunan Province. These data presented here are of good quality, and contribute to our understanding of the metallogenic mechanism. I believe that this MS will be of interest to international community, so presumably suitable for publication. I therefore recommend the paper be accepted after Major Revision, and my major comments are listed below:

 

1. Line 12, change ‘analysis’ to ‘study’.

2. Line 14, revise ‘large-scale’ into ‘large’.

3. Line 13-15, reorganize this sentence please.

4. Line 18, “precipitation is still unclear”, “precipitation are still unclear”.

5. Line 36-38, what do you mean? Please clarity this sentence.

6. Line 54-56, what’s the relationship with this study? It’s abrupt! The Baoshan deposit in this study do not include W-Sn mineralization.

7. Line 59-69, what is the relationship between the Xianghualing and Hehuaping Sn deposit with this Baoshan deposit? Why did you mention Xianghualing and Hehuaping Sn deposits here suddenly? They are different metal deposits with this study.

8. English expression is too bad, and needs more improvement, and many sections or sentences also need to be reorganized.

9. There are many mistakes in the text, please check all text and revise these obvious error.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English expression need be improved

Author Response

Reviewer #1: This manuscript presents the C-H-O isotopes and the characteristics of fluid inclusions of the Baoshan Cu-Pb-Zn deposit in the Southern Hunan Province. These data presented here are of good quality, and contribute to our understanding of the metallogenic mechanism. I believe that this MS will be of interest to international community, so presumably suitable for publication. I therefore recommend the paper be accepted after Major Revision, and my major comments are listed below:

1. Line 12, change ‘analysis’ to ‘study’.

Response: Thank you very much for your careful review of the manuscript. We have changed " analysis " to " study " in line 12. Please see the attachment.

2. Line 14, revise ‘large-scale’ into ‘large’.

Response: Thank you very much for your careful review of the manuscript. We have revised " large-scale " to " large " in line 14. Please see the attachment.

3. Line 13-15, reorganize this sentence please.

Response: Thank you for your constructive suggestion. We have reorganized the sentence, please see the lines 13-16. The Baoshan deposit is a large Cu-Pb-Zn polymetallic deposit in southern Hunan Province with obvious zoning of Cu mineralization and Pb-Zn mineralization: the central of the Baoshan deposit is contact metasomatic (skarn) Cu mineralization, and the western, northern and eastern are hydrothermal vein Pb-Zn mineralization.

4. Line 18, “precipitation is still unclear”, “precipitation are still unclear”.

Response: Thank you very much for your careful review of the manuscript. We have revised " precipitation is still unclear " to " precipitation are still unclear " in line 18. Please see the attachment.

5. Line 36-38, what do you mean? Please clarity this sentence.

Response: Thank you very much for your careful review of the manuscript. Based on the study of fluid inclusions and C-H-O isotopes in the Baoshan Cu-Pb-Zn deposit, we suggest that there are differences in the mineralization mechanism between the Cu mineralization area and the Pb-Zn mineralization area in the Baoshan deposit. Therefore, we would like to highlight that different mineralization mechanisms may have significant effects on the precipitation of metal elements in the multi-stage mineralization events. However, it may not be appropriate and we have removed the sentence.

6. Line 54-56, what’s the relationship with this study? It’s abrupt! The Baoshan deposit in this study do not include W-Sn mineralization.

Response: Thank you for your constructive suggestion. We have removed sentences that have little relevance to the topic of the manuscript. Please see the attachment.

7. Line 59-69, what is the relationship between the Xianghualing and Hehuaping Sn deposit with this Baoshan deposit? Why did you mention Xianghualing and Hehuaping Sn deposits here suddenly? They are different metal deposits with this study.

Response: Thank you for your constructive suggestion. We have removed sentences that have little relevance to the topic of the manuscript. Please see the attachment.

8. English expression is too bad, and needs more improvement, and many sections or sentences also need to be reorganized.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We worked on the manuscript for a long time and the repeated addition and removal of sentences and sections obviously led to poor readability. We have now worked on both language and readability and have also improved the language using a professional language editing service. We really hope that the language level has been substantially improved.

9. There are many mistakes in the text, please check all text and revise these obvious errors.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We made major revisions to the article in combination with the opinions of the editors and another two anonymous reviewers, and carefully checked the errors in the manuscript and revised it accordingly. Please see the attachment.

We hope that the revised manuscript is acceptable for publication in Minerals.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper presents fluid inclusion microthermometry and stable isotope data for ore samples from different ore-forming stages of the zoned Baoshan deposit. It is a more comprehensive study than previous research on the deposit. Previous data is described and included in diagrams. The results are presented and discussed in detail and the conclusions are broadly compatible with the data, and are expressed in a manner appropriate for the target audience.

That said, there is considerable scope for improvement in the presentation and interpretation. The metal zonation is mentioned early in the paper but is not illustrated until near the end of section 2.2 Deposit geology: it would help to provide an illustration of the zonation much earlier. Mineralization is not clearly shown on the figures as the color for mineralization is similar to colors of rock formations or faults. The location of the 23 samples that were analysed is not shown on any figure: are these from drillcore or from underground exposures?

There seems to be a presumption that skarn-related metallogenesis occurred at the same depth as the igneous intrusion. However, Figures 4 and 10 show that very little (if any) of the intrusion is at the level of the ore deposit; it mostly crystallized at a much greater depth. The depths of crystallization /ore formation, derived from pressure estimates, appear to be based on unsound evidence. As the depth range for skarn mineralization at Baoshan is stated as being greater than for other skarn deposits, this aspect of the study needs to be carefully considered and revised where necessary. In section 5.3 the authors state that the skarn stage pressure was 105-125 MPa corresponding to a depth of up to 4.6km, so subsequently when discussing the later Pb-Zn mineralization it is unclear how 70 MPa could indicate a depth up to 7km. Please review and change this.

'Atmospheric precipitation' is incorrectly used when the authors mean 'meteoric water' that occurs underground. Figure 10 is a nice 3D block diagram of the deposit and its host rocks: the top of the block shows the present-day outcrop. However, presumably a significant amount of overburden rock above the deposit has been removed by weathering and erosion. Therefore the atmospheric precipitation would not be on the top surface as shown. This reviewer suggests the authors delete the cloud and rain symbols and instead add downward-pointing blue arrows labeled 'Circulating meteoric water'.

An annotated copy of the submitted manuscript is attached. The authors should read and respond to the added further comments.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

There are issues with English language throughout the paper. This reviewer has commented on some of these, but the entire manuscript does need to be checked. In places the meaning is unclear or ambiguous. Some words and phrases are inappropriate for the context.

Author Response

Reviewer #2: Comments and Suggestions for Authors：

This paper presents fluid inclusion microthermometry and stable isotope data for ore samples from different ore-forming stages of the zoned Baoshan deposit. It is a more comprehensive study than previous research on the deposit. Previous data is described and included in diagrams. The results are presented and discussed in detail and the conclusions are broadly compatible with the data, and are expressed in a manner appropriate for the target audience. That said, there is considerable scope for improvement in the presentation and interpretation.

1. The metal zonation is mentioned early in the paper but is not illustrated until near the end of section 2.2 Deposit geology: it would help to provide an illustration of the zonation much earlier.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We have moved the sentence in Section 2.2 about the metal zonation of the Baoshan deposit to the introduction in the hope that it will better interest the reader. Please see the attachment.

2. Mineralization is not clearly shown on the figures as the color for mineralization is similar to colors of rock formations or faults.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We adjusted the color of mineralization to make it more distinguishable from the color of rock formations or faults, hoping to show the mineralization characteristics of the Baoshan deposit more clearly on the figures. Please see the Fig. 4 and Fig. 10.

3. The location of the 23 samples that were analysed is not shown on any figure: are these from drillcore or from underground exposures?

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We have labeled the locations where samples were collected in Fig. 4, and all of these analyzed samples came from underground exposures.

4. There seems to be a presumption that skarn-related metallogenesis occurred at the same depth as the igneous intrusion. However, Figures 4 and 10 show that very little (if any) of the intrusion is at the level of the ore deposit; it mostly crystallized at a much greater depth. The depths of crystallization /ore formation, derived from pressure estimates, appear to be based on unsound evidence. As the depth range for skarn mineralization at Baoshan is stated as being greater than for other skarn deposits, this aspect of the study needs to be carefully considered and revised where necessary. In section 5.3 the authors state that the skarn stage pressure was 105-125 MPa corresponding to a depth of up to 4.6 km, so subsequently when discussing the later Pb-Zn mineralization it is unclear how 70 MPa could indicate a depth up to 7 km. Please review and change this.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. As you say, most of the igneous intrusions at Baoshan mostly crystallize deeper than the ore bodies. However, the granodiorite samples used in this pressure estimation were taken from the same elevation as the Cu-Pb-Zn ore bodies. Therefore, we suggest that the pressure of biotite can be approximately representative of the pressure during the formation of the ore bodies. In addition, in section 5.3, the ore-forming pressure estimated by biotite is 105~125 Mpa, and the corresponding ore-forming depth is 3.89~4.63 km. However, from the skarn stage to the sulfide stage, the ore-forming pressure changes from the static rock pressure to the hydrostatic pressure, and the pressure estimated by the fluid inclusions is inferred to be in the range of 2-7 km. Of course, we also acknowledge the limitations of the depth estimation by biotite or fluid inclusions, and different reference standards may also have a certain impact on the depth estimation. However, combining biotite, fluid inclusions and geological phenomena, we speculate that the metallogenic depth of the Baoshan deposit is about 3~6 km. Please see the attachment.

5. 'Atmospheric precipitation' is incorrectly used when the authors mean 'meteoric water' that occurs underground. Figure 10 is a nice 3D block diagram of the deposit and its host rocks: the top of the block shows the present-day outcrop. However, presumably a significant amount of overburden rock above the deposit has been removed by weathering and erosion. Therefore, the atmospheric precipitation would not be on the top surface as shown. This reviewer suggests the authors delete the cloud and rain symbols and instead add downward-pointing blue arrows labeled 'Circulating meteoric water'.

Response: Thanks for your careful examination and constructive suggestions to improve our manuscript. We have deleted the cloud and rain symbols and instead add downward-pointing blue arrows labeled 'Circulating meteoric water'. In addition, based on your comments on the original manuscript, we have checked and revised the full text in detail (including but not limited to spelling and grammatical problems) and made corresponding marks in the revised draft. In addition, we made major revisions to the article in combination with the opinions of the editors and another two anonymous reviewers, and carefully checked the errors in the manuscript and revised it accordingly. Please see the attachment.

We hope that the revised manuscript is acceptable for publication in Minerals.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The publication deals with the origin and evolution of fluids involved in the formation of Cu-Pb-Zn mineralization at the Baoshan deposit in southern China. The publication is appropriately structured and the topic of the publication brings a number of new and valuable insights. In the abstract, I fail to state the specific temperatures and salinities of the measured inclusions. The introduction of the work and the description of the research methods are sufficient. The results of the work are clearly presented. Minor corrections and comments are marked directly in the attached pdf. The number of cited publications for discussion is adequate to the scope of the research.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

A minor revision of English would be appropriate. Chinese characters appear in the text, which must be corrected to English.

Author Response

Reviewer #3:

The publication deals with the origin and evolution of fluids involved in the formation of Cu-Pb-Zn mineralization at the Baoshan deposit in southern China. The publication is appropriately structured and the topic of the publication brings a number of new and valuable insights. In the abstract, I fail to state the specific temperatures and salinities of the measured inclusions. The introduction of the work and the description of the research methods are sufficient. The results of the work are clearly presented. Minor corrections and comments are marked directly in the attached pdf. The number of cited publications for discussion is adequate to the scope of the research.

Response: Thank you very much for your recognition of our research and for your careful review of the manuscript. Based on your comments on the original manuscript, we have checked and revised the full text in detail (including but not limited to spelling and grammatical problems) and made corresponding marks in the revised draft. In addition, we made major revisions to the article in combination with the opinions of the editors and another two anonymous reviewers, and carefully checked the errors in the manuscript and revised it accordingly. Please see the attachment.

We hope that the revised manuscript is acceptable for publication in Minerals.

Author Response File: Author Response.docx