A Review of the G4 “Tin Granites” and Associated Mineral Occurrences in the Kivu Belt (Eastern Democratic Republic of the Congo) and Their Relationships with the Last Kibaran Tectono-Thermal Events

Round 1

Reviewer 1 Report

This is an interesting manuscript, which provides information about the geological structure and history of the development of a region in Central Africa, which is rather poorly studied. At the same time, this region is well known for its rare metal deposits (Au, Sn, W, Nb, Ta) presumably associated with granites. The authors reviewed the geological and some geochronological data and formulated some important unresolved issues.

I have a few general comments that I think will help improve the manuscript:

1) The manuscript lacks an abstract. In the abstract, one can briefly focus on the main issues related to G4 granites. This will draw readers' attention to the article.

2) The authors pay great attention in the text to the age of the rocks. The ages ​​determined by different methods are constantly mentioned. It will be clearer to readers if these ages ​​(at least for granites) are indicated on the map (Figure 3)

3) One of the fundamental questions raised by the authors concerns the differences between G2, G3 and G4 granites. It would be better if the authors tried to indicate these different types of granites on a map (Figure 3).

4) An important difference criterion is the geochemical composition of granites. I recommend the authors to supplement the manuscript with a review of geochemical data (author's or already published data) about the composition of granites of various types (G2, G3, G4). In this case it will probably be possible to speak more reasonably about the differences between these types of granites.

Smaller remarks are indicated in the PDF-file as comments.

 

 

Comments for author File: Comments.pdf

Author Response

Our answers for the four reviewers are grouped in the cover letter - answers to the reviewers. See attached file

Author Response File: Author Response.docx

Reviewer 2 Report

3 It is better not to use abbreviations in the title.

In the conclusion there is interesting information that should be in the abstract.

15, 38 Central African Mesoproterozoic Kibaran Belt  =  Mesoproterozoic Kibaran belts?

55-56 …the mineral resources associated with the G4 granites, which provide 60 to 80% of the 55 world’s niobium-tantalum reserves…(What is the source of information?)

Fig.1 Drawing quality needs to be improved (for example, lines 10 – thrusts). 2a, 2b - ?

103 Ky1 stage-?

Author Response

Our answers to the four reviewers are grouped in the attached file. See below

Author Response File: Author Response.docx

Reviewer 3 Report

There are some questions in your paper that needs revision. See the attached PDF file.

-Send the manuscript to a native English-speaker. There a several grammar errors along the text.

Comments for author File: Comments.pdf

Author Response

Ours answers to the four reviewers are grouped in the attached cover letter. see below

Author Response File: Author Response.docx

Reviewer 4 Report

General comments

This manuscript is a compilation of information about the tin granites from the Kivu Belt, one of the three belts from the Kibarant belt, located in the Democratic Republic of Congo. A review about these granites is interesting because of the economic interest of the tin granites associated to the Kibaran belt. The compilation is exhaustive, however, there are many consecutive citations, but it is not clear to the reader what is provided in each of them. It would be better to indicate the most important ones, to which the reader should refer if he or she wishes to go deeper into the aspect cited.

I consider that this can be a good article but minor changes should be necessary. I indicate some suggestions here.

In all the manuscript: please avoid the use of coltan, this is a colloquil terminology. Moreover, the use of columbite-tantatite is also not completely correct, it is better to use the name “columbite-group minerals”.

Specific comments

Line 36. You do not need to use the term mineralized before occurences.   

Line 37. Replace “columbite-tantalite” by “columbite group minerals”.

Line 38. Include a citation for the age of the G4 granites.

Line 46. Change the verbal tense, you use past tense in this paragraph excerpt here that is a gerund.

Line 47-48. I don't think it is necessary to use inverted commas here.

Line 55-56. ¡Very important!. The 60-80% of world reserves are of tantalum, not of niobium, more than 90 % of the world reserves of niobium are in Barazil. The, delete niobium from this sentence.

Line 68-71 and in all the document. When there are several consecutive numbers use the first number followed by a hyphen and the last number, e.g. [6-8].

Line 73, 90, 115 and others. The reference to a figure begins by a capital letter eg. Fig.

Figure 1. A map of Africa with the indication of the study area should be very useful for the readers.

Improve the drawing of the legend of this figure and of Figure 4.

The a and b part of the figure should be indicated.

Liner 92-93. All authors? If not, please indicate some references.

Line 101. Explain briefly what this new model consists of.

Line 130. The citation must be indicated in order and without parenthesis, eg. Instead of “950 Ma ([28], [7], [34], [17], [4]) or“ this should be “950 Ma [4,7,17,28,34] or“.

Line 136-137 “Noteworthy, only the G4 granites provide minerals of interest at high economic levels like tin (mainly from cassiterite), columbite-tantalite (coltan),….”

Tin is not a mineral, delete this and replace “columbite-tantalite” by “columbite group minerals” and delete (coltan).

This should be: ““Noteworthy, only the G4 granites provide minerals of interest at high economic levels like cassiterite, columbite-group minerals,….”

Line 147. This should be “..by Varmaloff [40-47], who…”

Line 152 Similar change than in line 147.

Line 134-177, Too long paragraph.

Line 189. Rewrite this sentence; The main litostratigraphic units of……are shown in Figre 3.

Line 284. Delete this extra line.

Line 333. Delete the full stop

Line 345. “Mineralizations are mainly located in pegmatites, Quartz-veins, greisens, cleavages, diaclases or in fold apexes”, here you mix concepts of different type: “Mineralizations are mainly  located in pegmatites, quartz-veins and greisens associated with granites, where they occur in cleavages, diaclases or in fold apexes”. I think that also they are disseminated.

Line 465. Explin more clearly what are the thermal events.

Line 472-474. “According to several informative sources, the Kibaran belts and 472 particularly the KVB contain 60 to 80% of the world reserves in coltan and thus, will be a  target for explorations in the near future.”

(???) There are many reserves in Australia and Canada. Indicate reference of these sources.

In the discussion point 10 should be more developed.

Line 567. Avoid references in the conclusions section.

Delete lines 571-574.

Author Response

Our answers to the four reviewers are grouped in the cover letter in attached file.see below

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has improved significantly compared to the previous version after correcting the comments.

Just one remark:

Caption to Figure 4 should be corrected: 

Line 241 - Instead "7 - granitic bodies" it should be "7 - granites of __some type__ and 8 - granites of __another type__"

Also accordingly, the caption should have 15 points, not 14

Author Response

see attached file

Author Response File: Author Response.docx

Reviewer 4 Report

Authors modified the drawing of legend in Figure 1, but not that of Figure 4. I think this also should be improved. I accept the paper because this is part of the edition details.

Author Response

see attached file

Author Response File: Author Response.docx