A Trace Element Classification Tree for Chalcopyrite from Oktyabrsk Deposit, Norilsk–Talnakh Ore District, Russia: LA-ICPMS Study

Round 1

Reviewer 1 Report

The article is interesting for the reader dealing with the problem of distribution of trace elements in chalcopyrites. In this case, the authors present the results of the LA-ICP MS analyses with the use of BSE images of chalcopyrite ores from the PGE-Cu-Ni Oktyabrsk deposit in the Norilsk-Talnakh Ore District in Russia. According to the authors, the basic statistical analysis performed did not enable the separation of groups of trace elements typical for chalcopyrites from different ores. However, in Fig. 9, which shows the correlation matrices, some elements show a very high correlation coefficient, e.g. Zn and Cd and Zn and Pb in disseminated ores as opposed to the other ore types.

According to the authors, the proposed and conducted more advanced statistics, such as cluster analysis, made it possible to separate chalcopyrites into different groups of elements for each ore types. They recognized different distribution of elements such as: Se, Te, Cd and Pb at the success rate of 86%. However, in the Discussion chapter, the authors should provide precise numerical data and an explanation of the differences in the above-mentioned elements distribution.

In addition, the article requires some more explanations:

• It is necessary to include the basic analytical data from LA-ICP MS in the form of supplementary file (table). The background data will be very useful for other authors to compare data with chalcopyrites from other deposits.
• The issue of the selection of elements for LA-ICP MS requires clarification. Why were elements from the PGE group, such as Pt and Pd, omitted?
• The authors should also explain the results of the analysis a bit more for individual factors such as e.g. Ti-Mn (Table 1).
• The analysis also draws attention to the fact that in massive ores only 16 analyses were performed, which is almost 3x smaller number of measurements than for veinlets-disseminated ores. This requires clarification and / or supplementation.
• In figure 1a, there is no description for separating blue fields. In figures 2g-j, the description of ore mineralization host rocks needs to be completed.
• The main issue that the authors do not address is the source of metals for 3 different types of Cu-Ni ores. The described division of ore types relates mainly to the form of the mineralization occurrences, and not to the differential source of metals that appears to have been common. This is probably the reason for the lack of a marked differentiation in the trace element distribution in the chalcopyrites tested. The authors did not discuss the results in this respect and this also requires supplementing and presenting in the form of a short discussion.
• The above comments and other suggestions were made directly on the text of the manuscript. The article is well edited and illustrated with good quality graphics.

Comments for author File: Comments.pdf

Author Response

Thank you very much for the consideration of our m/s. Your comments and remarks are very useful. In Table of an attached file, you will find answers on the remarks point by point. As to your general comments, we answer onwards.

1. "High correlation coefficient, e.g. Zn and Cd and Zn and Pb in disseminated ores as opposed to the other ore types."

 

We agree with this note and added it to the figure captions. However, regarding, for example, Zn-Cd. Using only these two elements does not allow differentiation between different ore types as exemplified by Zn vs Cd diagram.  We added a few sentences in the discussion.

 

2. "Explanation of the differences in the elements distribution (Se, Te, Cd и Pb)."

We added a paragraph to Discussion.

 

3. "Why were elements from the PGE group, such as Pt and Pd, omitted?"

We tried to determine PGE concentrations. Unfortunately, the results from the analytical point of view were not satisfactory for chalcopyrite. In general, pentlandite is enriched by Pd. Chalcopyrite is characterized by low and very unstable PGE concentrations.

 

4. "Ti-Mn correlation."

Yes, you were right. Ti-Mn correlation could be controlled by rutile, ilmenite and Ti-magnetite. We added it to Table 1.

 

5. "The analysis also draws attention to the fact that in massive ores only 16 analyses were performed, which is almost 3x smaller number of measurements than for veinlets-disseminated ores."

Chalcopyrite of massive ore was analyzed by Mansur et al., 2019. Our data for massive or concur with their results. Thus we do not analyzed massive ores at the same extent as the other two ore types. Major focus was done to veinlet-disseminated ore because they were expected to be more diverse. 

 

6. "In figure 1a, there is no description for separating blue fields."

It is lakes. We edited Fig. 1.

 

7. " In figures 2g-j, the description of ore mineralization host rocks needs to be completed."

Yes, we agree. We added the information. See Table.

 

8. "The main issue that the authors do not address is the source of metals for 3 different types of Cu-Ni ores. The described division of ore types relates mainly to the form of the mineralization occurrences, and not to the differential source of metals that appears to have been common. This is probably the reason for the lack of a marked differentiation in the trace element distribution in the chalcopyrites tested. The authors did not discuss the results in this respect and this also requires supplementing and presenting in the form of a short discussion."

 

This is a really tough question to answer and there is no consensus between different researchers on the source of metals. Some consider the source of metals within mantle-derived magma itself, whereas others invoke unidentified crustal rocks. In general, it is logic to expect the same source of metals for disseminated and massive ores, because massive ores were formed by concentration of disseminated sulfide drops and somewhat different source of metals for veinlet-disseminated ore, because it is metamorphic in origin. We added a few phrases on this topic in the text. We also added a paragraph in Discussion on the process of fractionation of elements between different co-crystallized with chalcopyrite minerals.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript of Marfin A.E. and co-authors “A trace-element classification tree for chalcopyrite from Oktyabrsk deposit, Norilsk-Talnakh ore district: LA-ICP-MS in situ analysis. Geochemical and mineralogical studies of ca.12 Ma hydrothermal manganese ores in the provides well-documented insights into the complex mineralogy and chemistry of the sulfide ores. This is a high level mineralogical description. The authors discuss conditions and processes in the formation of the ore deposits to argue their hydrothermal nature. I think this is a well written, illustrated and insightful study that provides a range of information about this type of ore deposits. The most interesting data are concerned to finding of low Se chalcopyrite (in comparison to chalcopyrite of black smokers) in Cu-Ni deposits which is interpreted as high temperature variety. I can suggest some comments to improve this manuscript.

Line 2

R: Russia?

Line 3. …in-situ..

1. Of cause, the LA-ICP-MS analysis is carried in situ itself

Line 35-50

In introduction, the scientific problem which is resolved in the paper should be considered.

The reference amount for chalcopyrite study by LA-ICP-MS analysis is incomplete.

Line 62 “…petrographic varieties: contact…”

R: “Contact” is a petrographic varieties? Please, explain…

Line 65. “Here we focus on chalcopyrite from the sulfide ores”.

R: This information exists in the title  and Introduction of the paper and is not related to geological background, again.

Figure 1.

R: In captures, the composition of the rocks should be included

Line 71-74: “The massive (rich) copper-nickel ores are found…..within the Devonian sedimentary rocks…”  and  Line 76-77: The massive ores are also found in some other parts of the intrusion, where they are represented by small veinlet bodies up to first metres (R: meters) thick.

R: How these types of ms ores formed in context of “liquation” model? Please, explain.

Figure 2.

R: The description of the samples is very poor. Please, explain the components and textures.F.e.: What is the black nodule in the Fig 2a and 2c? It looks like primary sedimentary sulfide layers are replaced by pyrrhotite (photo2b) and pyrite (photo2c). Probably this is convergence of attributes, Please explain this textures in context of the “liquation” model. And so on.

Line 90-91”The disseminated type of ore is localized sometimes in contact rocks and olivine-free gabbrodolerites”

R: What is the name of the “rocks”?

Line 108-110: SEM EDS analyses and BSE images were used for the two reasons: first, for selection and a visual control of minerals for a LA-ICPMS study and, second, for determination of iron content used as an internal standard in LA-ICPMS.

R:  How is it possible to use? These methods have different beams sizes and depth of drilling and will show different contents of iron due to mineral inclusions in LA-ICP-MS analysis.

I think, this is “putative accuracy” of the analyses suggested.

Line 166: Concentrations of elements of chalcopyrite of different ore types fully overlap.

R: To many “of”. It is better to use passive form.

Line 192-198 and Figure 7.

R: The method to prepare this extraordinary tree should be explained carefully .

The main problem of the paper, that authors are not display own genetic model. They use references only This  is not high level of Science. This is the reason why the genetic geochemical interpretation is so poor. The concentration of trace elements in chalcopyrite different ore facies are almost the same. It should be explaned.

I suggest, that paper could be accepted after major revision.

Author Response

Thank you very much for the consideration of our m/s. Your comments and remarks are very useful. In Table attached as a separate file, you will find answers on the remarks point by point.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear authors

You formally responsed for my comments, of cause. I do not like to give You more comments.