Chromite Paleoplacer in the Permian Sediments at the East Edge of the East European Platform: Composition and Potential Sources
Round 1
Reviewer 1 Report
There are some language or spelling errors (in mineral names, for instance) which are repetitive (e.g. brukite instead of brookite) or inconsequent (e.g. chromian spinel - chromespinel - chrome-spinel - chromspinel - chomspinel).
Chapter 2: Do you have any dip data? Or an estimation, at least?
Rows 243-244: The authors surely do not want to mean the quality of the observation here, but the low grade of abrasion. However, a quantitative study of this parameter could contribute to the estimation of the transport distance.
Sections 4.4, 5.2: As concentrations are continuous variables, histograms may be used for visualization, but it would be more accurate to perform normality tests and characterize the distributions by standardized moments. Even more important is that comparison with distributions from published datasets could be also validated by using hypothesis tests.
Row 480: "Major" should be the adjective of 'rock forming minerals', obviously.
Row 617: This statement can be true for an exposure, but in general only if the surface is parallel with the bedding. Do the authors mean that?
Rows 648-650: It is the closest one, but is it really close enough to be the only suitable source worth mentioning in the conclusions?
Author Response
There are some language or spelling errors (in mineral names, for instance) which are repetitive (e.g. brukite instead of brookite) or inconsequent (e.g. chromian spinel - chromespinel - chrome-spinel - chromspinel - chomspinel).
Done. In the manuscript we use name chromspinel, but in the titles of some papers in the reference list contain "chromian spinel" and "chrome-spinel" names, that we can not change
Chapter 2: Do you have any dip data? Or an estimation, at least?
The chromspinel-rich layer occurs sub-horizontally. We have added this information (line 93).
Rows 243-244: The authors surely do not want to mean the quality of the observation here, but the low grade of abrasion. However, a quantitative study of this parameter could contribute to the estimation of the transport distance.
This sentence was changed
Sections 4.4, 5.2: As concentrations are continuous variables, histograms may be used for visualization, but it would be more accurate to perform normality tests and characterize the distributions by standardized moments. Even more important is that comparison with distributions from published datasets could be also validated by using hypothesis tests.
Yes, it is right. But the investigations now are in the first stage and we demonstrate the results only for four studied samples. When the amount of data will increase, we will use more powerful statistical facilities.
Row 480: "Major" should be the adjective of 'rock forming minerals', obviously.
Yes, we have changed
Row 617: This statement can be true for an exposure, but in general only if the surface is parallel with the bedding. Do the authors mean that?
Yes, the chromite-rich horizon occurs sub-horizontally, approximately at the same depth in different points of this area.
Rows 648-650: It is the closest one, but is it really close enough to be the only suitable source worth mentioning in the conclusions?
We can't say that the Kraka ophiolite allochthon is only one source for the Sabantuy chromite paleoplacer, despite it is closest and extremely big - about 900 sq.km. We have noted that the all Uralian ophiolite complexes spread along the Main Uralian Fault in the South Urals could be a provenance and Kraka peridotite massif is only one of them, the closest and biggest. We also noted a volcanic source for the Sabantuy paleoplacer.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Subject: “Chromite paleoplacer in the Permian sediments at the East edge of the East European platform: composition and potential sources” by Ildar R. Rackimov, Evgeneii V. Pushkarev and Irina A. Gottman.
This manuscript focuses on the mineralogical and geochemical study of a chromite paleoplacer in sediments of Permian age belong to the Uralian orogeny (East European Platform). The chromite-paleoplacer called “Sabantuy” was discovered and presented for the first time with the aim to provide information about the source of the detrital chrome-spinel. The studied sediments have been characterized from the petrographic, mineralogical and chemical point of view, using SEM-EDX and XRF analyses. The results indicate that ophiolite peridotites and chromite associated with oceanic and volcanic arc rocks can be considered as the main source for the detrital chrome-spinel of the Sabantuy paleoplacer.
In general, structure of the paper draft is adequate to the guidelines of the journal and all the main sections are quite well discussed. The paper contains good data and quality in the results. It is well written and rather logically constructed. The scientific results are almost correctly described and discussed and the various employed scientific methods are appropriate to achieve the objectives of the proposed study. The manuscript can be suitable for publication on “Minerals”, but some minor revisions are requested.
Specific comments:
- Figure 2 – Replace “stratigraphical” with “stratigraphic” in the figure caption.
- Figure 3 - More details are necessary about figures 3b and c, specify if they are photomicrographs and the mode of the observations if it is made in plane polarized light…
- Figure 4 – change in the caption “ternary classification diagram”.
- Modify caption of Table 1 as “Bulk chemical composition or XRF chemical data”
- Table 2 – modify caption, the reported data are “Selected SEM-EDX analyses”. About this table, have the authors applied the spinel formula calculation? It would be interesting to report the results of the formula calculation for spinel and also for the other mineral phases. Values of all the discussed ratios and parameters considered to classify the Cr-spinel, such as Mg/(Mg+Fe2+), Cr/(Cr+Al) and Mg#, should be shown in the table (Calculation formulae).
- Line 252: change “an” with “a”.
- Line 440-441 - delete the initials of the authors names cited in the text, only surname.
- Line 503 - “geotectinic” should be corrected to “geotectonic?”.
- Line 577 - “Thouse?”
Author Response
Figure 2 – Replace “stratigraphical” with “stratigraphic” in the figure caption. Done
- Figure 3 - More details are necessary about figures 3b and c, specify if they are photomicrographs and the mode of the observations if it is made in plane polarized light…Done
- Figure 4 – change in the caption “ternary classification diagram”. Done
- Modify caption of Table 1 as “Bulk chemical composition or XRF chemical data” Done
- Table 2 – modify caption, the reported data are “Selected SEM-EDX analyses”. About this table, have the authors applied the spinel formula calculation? It would be interesting to report the results of the formula calculation for spinel and also for the other mineral phases. Values of all the discussed ratios and parameters considered to classify the Cr-spinel, such as Mg/(Mg+Fe2+), Cr/(Cr+Al) and Mg#, should be shown in the table (Calculation formulae). The big table with chromite compositions and important coefficients has uploaded to supplementary.
- Line 252: change “an” with “a”. Done
- Line 440-441 - delete the initials of the authors names cited in the text, only surname. Done
- Line 503 - “geotectinic” should be corrected to “geotectonic?”. Done
- Line 577 - “Thouse?” Corrected
Author Response File: Author Response.docx
Reviewer 3 Report
The work submitted by Rakhimov et al. intends to investigate the composition of chromspinels (and other critical mineral phases) from the Sabantuy paleoplacer (Southern Pre-Ural region) and discuss the source rocks of this unusual occurrence.
The study is interesting and data-rich. Petrographic observations and analytical data are suitably and convincingly reported. The available database which is also comprehensively explored, leading to a well-supported discussion that delivers interesting indications regarding the sources of chromspinels found in the Permian sediments. In my opinion, the work deserves publication in MINERALS after minor revision
I’m not a native English speaker, but in my opinion a careful revision of writing should be made. Please find some suggestions (as well as several minor comments) below; I hope that these suggestions could be useful.
Please, review carefully Table formatting according to the rules provided by the “guide to the authors”. Tables 2 to 6 should be improved by adding the cationic distributions per formula unit.
Line 42: replace “occuring” by “occurring”
Line 44: “orogeny which was” or “mountains/highlands located to the eastward that…”?
Line 47: “host also”
Line 52: consider the replacement of “The Urals in own evolution passed…” by “The geodynamic evolution of Urals embraced…”
Line 132: remove “black”
Line 134: remove “The Most…”
Line 136: “few other oxide phases…”
Line 141: replace “are as follows” by “were as follows” and in the netx lines (141 and 142) replace “is” by “was”
Line 159: replace “:” by “are”
Line 202: remove “a” from “have a high…”
Line 210: replace “while” by “whereas” (the context in not time-dependent)
Line 216: “an incline of the trend”? Do you mean a different slope/tilt?
Lines 220/221: … but data-points representing the composition of this oxide are far above the trend and should not influence its direction.
Line 251: “weakly zonation” or “are weakly zoned”
Line 264: replace “differ” by “differences”
Line 275: correct the typo error “distribution” instead of “distrubution"
Line 279: “the elements are less than”
Line 293: Some references should be quoted to support this statement. These references are in captions of figures 9 and 10 but, in my opinion, they have to come with text.
Line 314: “The most inclusions” or “Most of these inclusions…”
Line 319: replace “discovered” by “identified”
Lines 320/321: “and it was recognized in…”
Lines 334/335: remove “compositionally corresponds to”
Line 336: replace “with” by “and”
Line 340: “of electron probe microanalyses” instead of “in microprobe analyses”
Line 439: correct the typo error “copmpletely” (completely)
Line 452: “in the supply…”
Line 455: replace “while” by “whereas”
Line 480: replace “while” by “whereas”
Line 482: “presents”? do you mean “occurs”?
Line 483: Established or observed/identified?
Line 500: replaced “governed” by “ruled”
Line 503: correct the typo error “geotectinic” (geotectonic)
Line 505: replace “while” by “whereas”
Line 534: replace “while” by “whereas”
Line 535: “make the same conclusion” or “reach similar conclusion”?
Line 544: replace “while” by “whereas”
Line 547: “This trend picks up all the more” ? I do not understand what you mean.
Line 577: Thouse?
Line 621: “thinlayred”?
Author Response
Please, review carefully Table formatting according to the rules provided by the “guide to the authors”. Tables 2 to 6 should be improved by adding the cationic distributions per formula unit. The addition of coefficients per formula unit to the tables will strongly increase of the manuscript volume. The big table with chromite compositions and important coefficients has uploaded to supplementary.
Line 42: replace “occuring” by “occurring” Done
Line 44: “orogeny which was” or “mountains/highlands located to the eastward that…”? Corrected
Line 47: “host also” Corrected
Line 52: consider the replacement of “The Urals in own evolution passed…” by “The geodynamic evolution of Urals embraced…” Corrected
Line 132: remove “black” Removed
Line 134: remove “The Most…” Done
Line 136: “few other oxide phases…” Done
Line 141: replace “are as follows” by “were as follows” and in the netx lines (141 and 142) replace “is” by “was” Done
Line 159: replace “:” by “are” Done
Line 202: remove “a” from “have a high…” Done
Line 210: replace “while” by “whereas” (the context in not time-dependent) Done
Line 216: “an incline of the trend”? Do you mean a different slope/tilt? Corercted
Lines 220/221: … but data-points representing the composition of this oxide are far above the trend and should not influence its direction. Corrected
Line 251: “weakly zonation” or “are weakly zoned” Corrected
Line 264: replace “differ” by “differences” Corrected
Line 275: correct the typo error “distribution” instead of “distrubution" Corrected
Line 279: “the elements are less than” Corrected
Line 293: Some references should be quoted to support this statement. These references are in captions of figures 9 and 10 but, in my opinion, they have to come with text. Done
Line 314: “The most inclusions” or “Most of these inclusions…” Corrected
Line 319: replace “discovered” by “identified” Replaced
Lines 320/321: “and it was recognized in…” Corrected
Lines 334/335: remove “compositionally corresponds to” Corrected
Line 336: replace “with” by “and” Corrected
Line 340: “of electron probe microanalyses” instead of “in microprobe analyses” Corrected
Line 439: correct the typo error “copmpletely” (completely) Corrected
Line 452: “in the supply…” Corrected
Line 455: replace “while” by “whereas” Done
Line 480: replace “while” by “whereas” Done
Line 482: “presents”? do you mean “occurs”? Corrected
Line 483: Established or observed/identified? Corrected
Line 500: replaced “governed” by “ruled” Corrected
Line 503: correct the typo error “geotectinic” (geotectonic) Corrected
Line 505: replace “while” by “whereas” Done
Line 534: replace “while” by “whereas” Corrected
Line 535: “make the same conclusion” or “reach similar conclusion”? Corrected
Line 544: replace “while” by “whereas” Done
Line 547: “This trend picks up all the more” ? I do not understand what you mean. Corrected
Line 577: Thouse? Corrected
Line 621: “thinlayred”? Corrected
Author Response File: Author Response.docx
Reviewer 4 Report
The manuscript № 1254531 “Chromite paleoplacer in the Permian sediments at the east edge of the East European Platform: composition and potential sources” is an important and good organized fundamental research. The significance of this topic is not in doubt since much attention is paid to the study of relative new Cr-placer deposit. This is a logical continuation of recent research by the authors. The undoubted merit of the authors is the detailed study of the main minerals with inclusions of the Cr placer with an objective assessment of the original sources of minerals and metals. This paper deserves to be published after minor revision, and I think that the manuscript would be a valuable contribution to the Minerals.
Major comments
- What is the relevance of this research to global issues of ore deposits? Authors should try to expand the relevance of the research.
- What do authors have under the term “representative samples”? What is this outcrop, core, trench or other? What weight were representative samples? Where were they collected? Show the sampling site on a map and/or section/log.
- The study of trace elements would be useful to assess the conclusions about sources of sediments and mineral. This is a recommendation.
- How was the LOI determined? This must be indicated in the methodology. What do the authors associate with the high LOC values (above 20%)? Could this be related to the research methodology? It is recommended to check the calibration curves that were used for XRF.
Minor comments
- Figure 12. “SSZ”, Figure 17. “IAB”, Figure 18. “OIB” and “ARC” should be deciphered.
Author Response
Major comments
- What is the relevance of this research to global issues of ore deposits? Authors should try to expand the relevance of the research.
We added a sentence in the Conclusions. In your manuscript we describe a newly discovered chromite paleoplacer in sedimentary deposit of the Permian age westward of the Ural folded belt. This is the first example of such placer close to the orogen. Taking into account the detritic nature of the chromites and probably their different sources, we can't discuss the problem of formation of ore deposits. The main target of this study is to find the potential sources for detritic chromites and shortly describe paleogeographical conditions of this deposit formation.
- What do authors have under the term “representative samples”? What is this outcrop, core, trench or other? What weight were representative samples? Where were they collected? Show the sampling site on a map and/or section/log.
The requested information was added to the text (chapter 2) and to the Fig 1.
- The study of trace elements would be useful to assess the conclusions about sources of sediments and mineral. This is a recommendation.
Thank you. We will use it in the next stage of investigation and exploration.
- How was the LOI determined? This must be indicated in the methodology. What do the authors associate with the high LOC values (above 20%)? Could this be related to the research methodology? It is recommended to check the calibration curves that were used for XRF.
We add some requested information in the Chapter 3 “Analytical Methods” and 4.2.
Minor comments
- Figure 12. “SSZ”, Figure 17. “IAB”, Figure 18. “OIB” and “ARC” should be deciphered. Done
Author Response File: Author Response.docx
