Spatial Relationship between Eclogite and Copper-Nickel Mineralization in East Kunlun, China

Round 1

Reviewer 1 Report

The discovery of big Cu-Ni deposits in the Kunlun orogenic belt is undoubtedly expected to encourage the authors to thoroughly analyze its origin and evolution and to reveal relationship with relevant geodynamic processes. The map presented shows that eclogites, well-known in the study region, sometimes occur together with mafic-ultramafic complexes, but they are not a prospecting sign of the presence of ore. 

The authors have not noted in their manuscript that the timing of formation of the mafic-ultramafic complexes is estimated at 424-378 Ma and that associated with them is granulite-, rather than  eclogite-facies, metamorphism (Wang et al., 2022 https://doi.org/10.1016/j.gsf.2021.101271).

However, the authors have correctly emphasized the assumption that the dragging of sediments with sulphur into the mantle was associated with early subduction processes. The suphur could have triggered the mobilization of ore elements by gabbroic rocks. In such interpretation, the authors should have given more attention to the sediments which form part of the subducting continental crust, rather than eclogites.

When assessing the timing of eclogite-facies metamorphism, the authors do not support their statement that it is Silurian, rather than Triassic, zircons which are simultaneous with it. To support their arguments, it would be sufficient to study the geochemistry of zircons. Furthermore, while describing the eclogites, the authors say nothing about the composition of plagioclase. Is it a relict or metamorphic-formed mineral? This fact can be of key value when discussing the eclogites.

Thus, the manuscript submitted has been poorly worked-out and should be prepared more thoroughly with regard for all available facts. Obviously, the relationship of ore mineralization with the eclogites is not as straightforward as the authors try to demonstrate.

 

Author Response

We feel great thanks for your professional review work on our article. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made corrections to our previous draft, the detailed corrections and explanations are listed below.

1. The map presented shows that eclogites, well-known in the study region, sometimes occur together with mafic-ultramafic complexes, but they are not a prospecting sign of the presence of ore.

“eclogite can be used as an indirect prospecting markers in searching for these types of deposits.”is deleted in the conclusion.

2. The authors have not noted in their manuscript that the timing of formation of the mafic-ultramafic complexes is estimated at 424-378 Ma and that associated with them is granulite-, rather than  eclogite-facies, metamorphism (Wang et al., 2022 https://doi.org/10.1016/j.gsf.2021.101271).

We think that mafic-ultramafic complexes, granulite and eclogite may be an organic whole, which is the product of continental subduction collision process system. Fig. 11c of Wang et al. (2022) is similar to Fig. 9 of this paper, and emphasize that the upwelling of asthenospheric mantle causes partial melting of metasomatic lithospheric mantle after the subduction plate break-off.

Only the depth of their formation is different. Fig. 11 (Wang et al., 2022) shows that the metamorphism of eclogite-facies occurred in the asthenosphere, the mafic-ultramafic magma formed at the bottom of the mantle wedge, and the granulite occurred in the continental crust.

3. When assessing the timing of eclogite-facies metamorphism, the authors do not support their statement that it is Silurian, rather than Triassic, zircons which are simultaneous with it. To support their arguments, it would be sufficient to study the geochemistry of zircons.

It's a disadvantage that we didn't test the geochemistry of the zircons. Although the peak metamorphic age of the eclogite from obtained here is 415Ma, which is Devonian, we support that eclogite metamorphism continued from Silurian to Devonian. Because eclogite is formed through two stages of retrogression and metamorphism, it usually takes several to tens of millions of years to form. The dates of metamorphic peak ranges from 426 to 402Ma, and some of the data have shown that metamorphism occurred in Silurian. Meanwhile, Zhang et al.(2017) also obtained that the prograde metamorphic age of Xiarihamu eclogite is 436Ma.

4. Furthermore, while describing the eclogites, the authors say nothing about the composition of plagioclase. Is it a relict or metamorphic-formed mineral? This fact can be of key value when discussing the eclogites.

The EPAM data and composition of plagioclase are supplemented. The plagioclase of Xiarihamu is mainly andesine and labradophyre, isoligoclase and andesine in Langrimu. It is added that plagioclase is metamorphic-formed mineral.

We have tried our best to improve the manuscript, but due to the current research situation, there are still some problems that are not easy to explain, and we hope to get your understanding. Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Yon Zhang et al., ,

First of all I wish you Happy New Year 2023. Please find below my  comments and suggestions on the paper Manuscript Number: Minerals-2108033

 

Comments and suggestions on

Manuscript Number: Minerals-2108033

Title : Coupling relationship between eclogite and copper-nickel min-2 eralization in East Kunlun, China

Authors and affiliations :  Yong Zhang1, Tong Pan2*, AiKui Zhang1*, ShuYue He1, Ye Qian3 and Yong Shan Bai 4

1. The Third Geological Exploration Institute of Qinghai Province, Xining 810029, Qinghai, China

2. Bureau of Geology and Mineral Exploration and Development of Qinghai province, Xining 810001, Qinghai, China

3. College of Earth Sciences, Jilin University, Changchun, 130061, Jilin, China

4. Qinghai Geological Survey Institute, Xining 810012, Qinghai, China

 

 

Yong Zhang et al., investigated the relationship between eclogite and copper-nickel mineralization in East Kunlun, China. Further, eclogite protolith properties, formation environment, and metallogenic mechanism were also investigated. They used petrography, geochemistry, U-Pb zircon geochronology, and electron probe mineral analysis. The geochemical characteristics of eclogite indicated that the protolith is highly differentiated Fe gabbro that formed in a continental margin type of rift environment. The electron probe analysis showed that the composition of garnet ranges from almandine -calcium almandine, and omphacite is mainly containing augite. Geochronological investigations showed that the peak  metamorphic age of eclogite in Xiarihamu and Langmuri 415.6 ± 2.7 Ma (MSWD = 0.43, n = 16) and 449.1±8.5 Ma (MSWD = 0.88, n = 19).

The paper is conclusive and provides interesting insights for the scientific community working on eclogite and copper-nickel mineralization. The paper fit also in the scope of Minerals. However, I have two comments and suggestions on the paper

(1) Comment 1

The introduction needs to be rewritten.

The introduction to a research paper is where you set up your topic and approach for the reader. It has several key goals:

(a)     Present your topic and get the reader interested

(b)   Provide background or summarize existing research

(c)    Position your own approach

(d)   Detail your specific research problem and problem statement

(e)    Give an overview of the paper’s structure

(2) Comment 2

I have a problem of the structure of the manuscript. I suggest to add a section in 5. Results

5.1. Petrography

Move to this section

Lines 137-183

Lines 191-201

5.1. Petrogeochemistry change to 5.2 Geochemistry

 

I suggest to change 7. Conclusions to 7. Concluding remarks

(3) Comment 3

I suggest to put the U-Pb geochronology tables in supplementary material

 

Author Response

We feel great thanks for your professional review work on our article. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made corrections to our previous draft, the detailed corrections and explanations are listed below.

1. The introduction needs to be rewritten.

The introduction to a research paper is where you set up your topic and approach for the reader. It has several key goals:

(a)  Present your topic and get the reader interested

(b)  Provide background or summarize existing research

(c)  Position your own approach

(d)  Detail your specific research problem and problem statement

(e)  Give an overview of the paper’s structure

We sincerely thank the reviewer for careful reading. According to your suggestion, we have rewritten the introduction, and the research methods, research questions and research significance are supplemented.

2. I have a problem of the structure of the manuscript. I suggest to add a section in 5. Results

5.1. Petrography

Move to this section, Lines 137-183 and Lines 191-201

5.1. Petrogeochemistry change to 5.2 Geochemistry

Section 5.1 Petrography has been added to the results, and lines 150-183 and 191-201 are moved to that section, but ines 137-149 are not moved, because the geological map of the mining area and the column chart of rock sequences are added here, based on the opinion of Reviewer 3.

Furthermore, As suggested by the reviewer, we have corrected the “5.1 Petrogeochemistry” into “5.2 Geochemistry”, and “7. Conclusions” into “7. Concluding remarks”.

3. I suggest to put the U-Pb geochronology tables in supplementary material.

The zircon U-Pb data have been deleted and are attached in table 1.

We appreciate for your warm work earnestly, and hope the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx

Reviewer 3 Report

 

Article title: Coupling relationship between eclogite and copper-nickel mineralization in East Kunlun, China.

Journal: MDPI-minerals.

The issue of this article is important, as this article is dealing with the use of eclogite as an exploration marker for the Co-Ni deposits in China. The researchers discuss the spatial linkage between these deposits and eclogite in East Kunlun, China based on field, geochemistry, mineral chemistry, and geochronology. I agree the general concepts and conclusions of this article. However, in my opinion there are several issues that require major revision. Specifically:

1-      The language needs improvement and there are some technical terms must be deleted. I tried to help about this issue and you can find some comments in the attached pdf.

2-      It is better to change the word “coupling” in the title into “Spatial”. Spatial relationship between eclogite and copper-nickel mineralization in East Kunlun, China.

3-      Please, provide us with some more information about field frameworks and tectonics, rock sequences in East Kunlun, not just eclogite.

4-      In mineralogy, there are some technical terms in description of minerals. When you talk about minerals, use crystals or grains not pieces. Besides, Figure-2, you put the caption as a part of the article text.

5-      Sample collection part in methodology. For better, put this description of samples in a table. The sample, brief description, and coordinates.

6-      What are the calibration and spectral lines used in Electron probe microanalysis (EPMA)?.

7-      In this part, 5.3. U-Pb zircon age. Add some recent references about magmatic zircons as I suggested in the pdf, if the range of U and Th in measured zircons is very large, the average cannot be calculated. Delete the average, as the average can be calculated for the most numbers that have small range. Besides, use always dates for individual and spot analyses, and ages for Concordia or mean weight ages.

 

8-      There are some analyses in zircons that show U/Th ratios of magmatic zircons and others related to hydrothermal zircons (> 1). In addition, some U-Pb dates range from 1600 to 1900 Ma, what it means in term of petrology. Please, give us a clear interpretation for those dates, precisely, some of them show U/Th ratios for magmatic zircons.

9-      Please, I have some additional comments in the attached pdf.

Comments for author File: Comments.pdf

Author Response

We feel great thanks for your professional review work on our article. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made corrections to our previous draft, the detailed corrections are listed below.

1. The language needs improvement and there are some technical terms must be deleted. I tried to help about this issue and you can find some comments in the attached pdf.

We were really sorry for our careless mistakes. Thank you for your reminder. According to the attached pdf comments, the language has been improved and some technical terms have been deleted.

2. It is better to change the word “coupling” in the title into “Spatial”. Spatial relationship between eclogite and copper-nickel mineralization in East Kunlun, China.

We have corrected the title of the paper is changed to “Spatial relationship between eclogite and copper-nickel mineralization in East Kunlun, China”.

3. Please, provide us with some more information about field frameworks and tectonics, rock sequences in East Kunlun, not just eclogite.

“Figure 2. Geological maps of Xiarihamu and Langmuri Cu-Ni mining area” are added to the distribution characteristics of eclogite in Section 3. The figure includes a column chart of rock sequences.

4. In mineralogy, there are some technical terms in description of minerals. When you talk about minerals, use crystals or grains not pieces. Besides, Figure-2, you put the caption as a part of the article text.

According to your suggested, we have corrected the “pieces” into “grains”. Besides, In Figure 3, change the caption to be part of the title.

5. Sample collection part in methodology. For better, put this description of samples in a table. The sample, brief description, and coordinates.

The sample collection description is shown in Table 1.

6. What are the calibration and spectral lines used in Electron probe microanalysis (EPMA)?.

We have added the data correction method is ZAF and the spectral line system is Kα spectral line.

7. We have checked the literature carefully and added more references on Mahdy et al., 2015 and Mahdy, 2021 into the U-Pb zircon age part in the revised manuscript. The average Th and U contents are deleted. Date was used instead of age when describing the age of individual zircon.

We have checked the literature carefully and added more references on Mahdy et al., 2015 and Mahdy, 2021 into the U-Pb zircon age part in the revised manuscript. The average Th and U and Pb contents are deleted. “Date” was used instead of “age” when describing the age of individual zircon, .

8. There are some analyses in zircons that show U/Th ratios of magmatic zircons and others related to hydrothermal zircons (> 1). In addition, some U-Pb dates range from 1600 to 1900 Ma, what it means in term of petrology. Please, give us a clear interpretation for those dates, precisely, some of them show U/Th ratios for magmatic zircons.

The zircons with dates range from 1600 to 1900Ma and some zircons with magmatic characteristics are supplemented and explained. The former may be captured zircons from the Jinshuikou group, the latter is interpreted differently in Xiarihamu and Langmuri, residual Jinshuikou magmatic zircons(>1300Ma) or zircons(~250Ma) brought in by Triassic magmatic activity, residual magmatic zircons from protolite of eclogite, respectively.

9. Please, I have some additional comments in the attached pdf.

The attached comments are all revised in the attached PDF.

We tried our best to improve the manuscript and made some changes marked in revisions mode. We appreciate for your warm work earnestly, and hope the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Look please line 341-343 and table 3. There is not omphacite in this rock so there is not eclogite in Xiarihamu area. If there is no eclogite that is not present the main object for discussion.

Comments for author File: Comments.pdf

Author Response

We feel great thanks for your professional review work on our article. As you are concerned, it is impossible for omphacite to have such low Na₂O content and may not be omphacite. We were really sorry for our mistakes, and thank you for your reminder. According to your nice suggestions, we have made corrections to our previous draft, the detailed corrections and explanations are listed below.

1. Look please line 341-343 and table 3. There is not omphacite in this rock so there is not eclogite in Xiarihamu area. If there is no eclogite that is not present the main object for discussion.

After communicating with the laboratory, this test work first identified the pyroxene under the microscope, and then carried out the EPMA. Through the analysis of the data, pyroxenes were mainly diopsides, and only one omphacite data was obtained. Two omphacite data obtained by Qi et al.(2014) in Xiarihamu were collected, and replaced the original data of No. 6, 7 and 8 diopside. From the EPMA data, it can be seen that most of the omphacite has been retrograded to diopside. In addition, the presence of eclogite was confirmed in Xiarihamu(Qi et al., 2014; Zhang et al. 2017; Fan et al., 2018; Pan and Zhang, 2020; Guo et al., 2020).

This single mineral calculation of pyroxene was calculated by Geokit (2014) software, and the calculation result had no Jd component（Only Wo, En,Fs and Ac contents are provided）. The calculation method of Lindsley (1983) was adopted in this modification, the content of Jd in Xiarihamu and Langmuri is 24 mol% - 31 mol% and 36 mol% - 41 mol%, respectively. The composition diagram of pyroxene (WEF-Jd-Ae) was supplemented in fig. 5b.

We tried our best to improve the manuscript, and hope the correction will meet with approval. We sincerely thank you for your comments and suggestions.

Author Response File: Author Response.docx

Reviewer 3 Report

no comments

Author Response

Thank you very much for your approval of this revision, and thank you again for your comments and suggestions.

Round 3

Reviewer 1 Report

I recommend the manuscript for the publication as after three cycles of changes authors improved the manuscript and removed the most difficult questions.  However problem  of interrelation eclogites and Cu-Ni mineralizations it is not solved and demands the further analysis.