Chromite Mineralization in the Sopcheozero Deposit (Monchegorsk Layered Intrusion, Fennoscandian Shield)

Round 1

Reviewer 1 Report

Review on the article

Chromite mineralization in Sopcheozero deposit (Monchegorsk layered intrusion, Fennoscandian Shield)

By Artem V. Mokrushin *, Valery F. Smol’kin

He paper is devoted to the interesting problem that concerns the variations of the Cr-spinels from the layered Sopcheozero deposit. But It is clear that it should be essentially rewritten.

The amount of analyses >100 is not sufficient for such paper? Because even the variations in one sample which should be checked first should include about ten analyses.

The language is far from the professional English and even terminology is not good. For example microprobe – it is not clear commonly this is EPMA electron microprobe analyses.

The Introduction actually contain a lot of material that should be in Geological Background part.

From the description it is not completely clear what authors think about the relationships of the layered part and the chromite ores.  The later are clearly veins or dikes, which cut the structure of the massif.

It is necessary to divide the units at first and study the mineralization separately.

The methodology of the analyses using Cameca MS-46 (produced 55 years ago) should be described more detail standards, precision etc (I was used such device in Ulan-Ude 40 y.a ) because it is rather complicated method.

The references of literature is very scarce and did not allow even list the works devote to this massif.

The paper is not clearly divided in the parts the results and descriptions are mixed.

The thermobarometry is not used at all. Nothing is clear about the PT parameters of each unit and chromite ores.  The oxygen regime also is simply postulated.  But what are the methods used,

I suggest that the paper should be completely reconstructed and then resubmitted.

It clearly contains interesting geological observations and some interesting

Major revision

Best wishes 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript reports a mineralogical study on chromite mineralization located in the Fennoscandian Shield. The topic of the paper is of great interest for the international scientific community, therefore the manuscript can be accepted after moderate revision. Here are some comments.
Please refer to the paper and compare you results presented: Chistyakova et al. 2015 Chromitite Dykes in the Monchegorsk Layered Intrusion, Russia: In Situ Crystallization from Chromite-Saturated Magma Flowing in Conduits. J. Petrol. Volume 56, Issue 12, December 2015, Pages 2395–2424, https://doi.org/10.1093/petrology/egv079.
Lines 20 and 21 magno-alumo-chromite and magno-chromite are not used to define the composition of the spinel.
Introduction. This chapter is too long and lacks of the aim of the paper. Please make it shorter and at the end explain the target of your work.
A lot of intrusions are mentioned in the text. I suggest to summarize them in a table providing age, country and the hosted ore mineralization and also in a figures showing their location.
Regarding the chromite composition, I recommend to the authors to classify the chromite ores i.e. metallurgical, refractory, and chemical ores based on their major applications.

Figure 1. Please insert a box with showing the location in the Fennoscandian Shield of the studied pluton and the geographical coordinates

Line 254. Tension or current?
Lines 264-267. Not very clear.
Table 1 I guess that these data refers to whole rock analyses. Please specify. The very high SiO2 content is clearly related with the abundance of interstitial silicates.

Plot the chromite composition is the typical diagram to classify it.

Table EPMA Results? Why the Fe2O3 values are not reported as in Table 3?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Review of Chromite mineralization in Sopcheozero deposit (Monchegorsk layered intrusion, Fennoscandian Shield) by A.V. Mokrushin and V.F. Smol’kin.

The manuscript reports the geochemical characterization of a chromatite mineralization in Sopcheozero deposit. It is clear that the Authors did a detailed work and efforts to characterize both geologically and geochemically this deposit. However, in the manuscript there are some issues which make the manuscript difficult to follow and affect its quality. Therefore, I suggest a major revision for this manuscript.

Here I report the main problems of this work

• writing of the manuscript is very redundant, and some parts are (unnecessarily) too detailed. The manuscript should be extensively re-organized before to be published, as some parts are located in the wrong sections (e.g., in the Introduction some parts are more appropriated in the Geological background section, and viceversa);
• the aim of this work is missing, which is the most important aspect of a manuscript.
• Lines 91-121: in final part of the introduction anticipates with too high detail the results of this work. A simple preview of the conclusion is useful, but a detailed summary is not appropriated.
• Lines 762-770: the conclusions reported in these lines were not supported by the results, neither discussed in a proper discussion section. The conclusion should report a summary of this work, but here the section reports interpretations totally new, which have not been discussed before.

Below I list some suggestion to improve the manuscript.

Abstract:

Lines 11-15:  are not necessary. Be more focused only on Sopchezero mineralization and on the results of your work. A good summary of this work, where you can “take” some sentences, is reported in lines 91-121.

Introduction:

• Here the aim of this work is missing
• Lines 49-78: the history of the studies and Authors, which investigated this area since 1970 is not necessary. Please summarize or even delete this part and focus only on the more recent studies.
• Lines 79-90: this part is more appropriated in the “geological background” section
• Lines 91-121: as I said before, the final part of the introduction anticipates too much the results of this work. See comments above.

Geological background:

In general, the “Geological background” section reports with too much detail the geological characteristics of the Fennoscandian layered intrusions, and only the last three lines discuss the geological background of the Sopcheozero deposit. I suggest to enlarge the geological background of Sopcheozero deposit (you can use information reported in lines 79-90) and remove other parts (see below)

• Lines 122-166: This part is not a geological background of the area. It could be used as introduction of the manuscript
• Line 136: write “whose” instead of “which”
• Lines 142-148; 155-160; 199-202; 224-229; 231: remove these parts. They are not necessary for this work

Results and observation:

This section should report new and personal results of the Author. However, the sub-section “3.1. Morphology, structure and zoning of the Sopcheozero chromite deposit” is a summary of the previous study. I suggest to remove this part or to use it to write the geological background of the Sopcheozero chromite deposit

Description of the ore composition of the Sopcheozero deposit:

• Lines 489-493: The presentation of the minerals should be insert at the begin of this subsection.
• Lines 503-599: The writing here is too long and redundant. I suggest to the author to divide this part in subsections, one for each type of Cr-spinel (e.g., 3.4.1. Accessory Cr-Spinel; 3.4.2. Ore Cr-spinel…) and to summarize their characteristics
• Line 730-733: remove this part. It is not necessary for the discussion, as you simply show the results without interpret the (missing) correlations between P2O5 and the minor elements with chromatite

Conclusions:

• Avoid the literature in conclusion
• Lines 762-770: as I commented above, here the section reports new interpretations, which were not discussed before. I suggest to implement the Discussion section about the genesis of the Sopcheozero

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I should say that despite the authors made significant modification there are still some  not clear things about the methods standards etc. And  the data  base is not  shown only averages. So I the primary material is  not presented. May be somebody including reviewers wants to calculate PTFO2 and check the conclusions.  It possible to place the data in supplementary file

Methods are  not described  - look at any international paper for example.

The associated  minerals are not

 characterized also interesting to see at least  variations of olivine   Mg’ in the section will be interesting

In abstracts commonly are writing the results and  conclusions in the short  but not what authors  they wanted to investigate  Better to rewrite it.

Yes the geological description and petrography are done in detail. But I should say that  calculations are less than  I student works.

I really am not sure about the very  low oxygen fugacity it should highly vary previous  investigators

From the diagram Figure 9. It is clear   that it was  essentially  vary.

There are  other methods  for calculation of the FO2 values  not only (Ballhause et al., 1991)   the method (Taylor et al., 1991)  uses Ol –Sp only and  possible to estimate  without olivines  also.

 So  this time  moderate revision

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The Authors satisfied all my requests. I considered this work acceptable for a publication.

Author Response

We pay Your attention that we have applied for the English Editing service for spell- and grammar-check. The paper has been carefully proof-read by an English expert with a decade-lond practice and sound experience in publishing in Minerals. The paper has been significantly improved and partly rewritten, when needed.