Variety of Iron Oxide Inclusions in Sapphire from Southern Vietnam: Indication of Environmental Change during Crystallization
Round 1
Reviewer 1 Report
Minerals - Open Access Journal
MDPI journal
Subject: Review of: “Variety of Iron Oxide Inclusions in Sapphire from Southern Vietnam: Indication of Environmental Change during Crystallization” (minerals-1046385-peer-review-v1-1) submitted by Vu et al.
Submitted manuscript “Variety of Iron Oxide Inclusions in Sapphire from Southern Vietnam: Indication of Environmental Change during Crystallization” Vu et al. describes primary wüstite, hercynite, titanohematite and titanomagnetite inclusion in sapphires from Southern Vietnam placer deposits and draw conclusions based on EMPA and micro Raman data.
Numerous inconsistencies are found Geological setting, Methodology, Results and Discussion chapters that needs to be clarified/corrected priori to acceptance of the manuscript as follows:
Clarifications
1st clarification – terminology
Authors wrongly use term “syngenetic” referring to primary origin of inclusions. Syngenetic and the opposite term epigenetic are used for description of relationship between time of formation of the ore deposit and the host rocks. Solid inclusions in minerals by definition are primary. Due to p/t/c changes primary solid inclusions can decompose to other minerals. This needs to be clarified throughout the manuscript.
2nd clarification - Geological setting
There is a long-lasting scientific discussion on the origin of sapphires and associated zircon placer deposit from Central Highlands, Vietnam, with only weak relation of these deposits to Cenozoic alkali basalts in the region. Authors failed to summarise important facts from previous studies, whereas an important work of international group of scientists published in Minerals had been completely omitted (Sinh et al., 2019 Gem-Quality Zircon Megacrysts from Placer Depositsin theCentral Highlands, Vietnam—Potential Sourceand Linksto Cenozoic Alkali Basalts). Geological section need to be rework and extended, and important conclusion from previous research clearly stated.
3rd clarification - Materials and Methods
General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1). Each and every figure in the manuscript must contain sample names – which again should be related to the geological map. We are missing a comprehensive table with sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results.
4th clarification – Results
My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section.
Conclusions are weak and basically represent a summary of the previous extensive research in the region.
Table 1
Several analyses have total wt% between 91.6 and 95.9 wt% are unreliable and should be repeated or omitted.
Figure 1
Authors are advised to insert location of the collected samples following aberrations in Tables 1 NS 2
Figure 2, 3, 8
Please insert sample names for each of the presented microphotographs.
Figure 4 to 7
Please insert sample names for each of the presented Raman spectra.
Figure 7
Please insert sample names for each of the presented spinel composition.
English is below internationally recommended level.
Submitted MS could potentially rise an interest of the international audience, however due to described inconsistencies, it is not publishable in a current form and I recommend reworking it according to instructions and resubmit after major revision.
Yours sincerely
15th of December, 2020
Author Response
Responses to Reviewers
We would like to thank all reviewers for very their kind support and very constructive comments. All the comments and suggestion were taken for revision of the manuscript.
1. Classification – Terminology: the syngenetic inclusion are change to primary inclusion. Therefore, we revise some sentence to classification for the inclusion on lines 103-104.
2. Geological setting: more information of metamorphic, sedimentary and igneous rocks in the study area are added and properly discussed. To describe for geological setting, we have added figure 1 which showed the study area and tectonic structures in Southern Vietnam. According to above requirements of reviewer, we have changed geological map (figure 2) which showed all geological formations in the study area as well as revise some sentence to describe about geology of area study on lines 41-53.
3. Materials and Methods: - General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1): sampling points are given in the figure 1 (figure 2). - Each and every figures in the manuscript must contain sample names– which again should be related to the geological map: all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217. - Sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results: all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A.
4. My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section: more information about the discussion from the results is moved to the discussion.
5. For laser irradiation means when dealing with Raman spectroscopy: more information about the usefulness of laser irradiation as below - Record the Raman pattern and its alteration in wüstite - Detection the structures and compositional variants of ilmenite and hercynite We also revise some sentence to describe the usefulness of laser irradiation on lines 89-94.
6. How laser power affects the samples under examination by means of oxidation and phase transformations: Raman spectra of wüstite can be permanently transformed in their structures from magnetite structure (Fe3O4 ) to hematite structure (Fe2O3) under effect of high laser power.
7. Figures 4a, b, c (Figures 5a, b, c): frequencies of the peaks are added into these Figures. We also revise some sentence to describe these frequencies of the peaks on lines 189-193.
8. Figure 4a (Figure 5a) shows the Raman spectra characteristic of wüstite with structure in non-equivalent sites of nonstoichiometry wüstite which looks very similar to the magnetite (Fe3O4). Therefore, we also revise some sentence to describe this spectra on lines 235-259.
9. Unreliable total wt% between 91.6 and 95.9 wt% of several analyses are replaced or omitted. Therefore, we also revise some sample data (i.e., KN20a, KN05, GL85) in Table 1 to describe new data on lines 154-155.
10. Grammatical and typographical errors as well as spelling mistakes are revised and corrected, accordingly.
Reviewer 2 Report
In general. well written and researched.
Given that these are isolated crystals, their context is difficult to describe. A bit more of the geology of the deposits would be of interest to a wider audience.
Overall it is well written and composed. The work is supported by a good presentation of the results. A few more comparisons with other examples of metallic inclusions in sapphires on a global basis would be helpful. But this is a pretty small population so there may not be many more.
Minor issues with the English but in general quite readable and comprehensible.
I am not qualified to review the Raman work however and I recommend another reviewer be selected for that task.
Comments for author File: 
Comments.pdf
Author Response
Responses to Reviewers
We would like to thank all reviewers for very their kind support and very constructive comments. All the comments and suggestion were taken for revision of the manuscript.
1. Classification – Terminology: the syngenetic inclusion are change to primary inclusion. Therefore, we revise some sentence to classification for the inclusion on lines 103-104.
2. Geological setting: more information of metamorphic, sedimentary and igneous rocks in the study area are added and properly discussed. To describe for geological setting, we have added figure 1 which showed the study area and tectonic structures in Southern Vietnam. According to above requirements of reviewer, we have changed geological map (figure 2) which showed all geological formations in the study area as well as revise some sentence to describe about geology of area study on lines 41-53.
3. Materials and Methods:
- General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1): sampling points are given in the figure 1 (figure 2).
- -Each and every figures in the manuscript must contain sample names– which again should be related to the geological map: all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217.
- Sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results: all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A.
4. My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section: more information about the discussion from the results is moved to the discussion.
5. For laser irradiation means when dealing with Raman spectroscopy: more information about the usefulness of laser irradiation as below - Record the Raman pattern and its alteration in wüstite - Detection the structures and compositional variants of ilmenite and hercynite We also revise some sentence to describe the usefulness of laser irradiation on lines 89-94.
6. How laser power affects the samples under examination by means of oxidation and phase transformations: Raman spectra of wüstite can be permanently transformed in their structures from magnetite structure (Fe3O4 ) to hematite structure (Fe2O3) under effect of high laser power.
7. Figures 4a, b, c (Figures 5a, b, c): frequencies of the peaks are added into these Figures. We also revise some sentence to describe these frequencies of the peaks on lines 189-193.
8. Figure 4a (Figure 5a) shows the Raman spectra characteristic of wüstite with structure in non-equivalent sites of nonstoichiometry wüstite which looks very similar to the magnetite (Fe3O4). Therefore, we also revise some sentence to describe this spectra on lines 235-259.
9. Unreliable total wt% between 91.6 and 95.9 wt% of several analyses are replaced or omitted. Therefore, we also revise some sample data (i.e., KN20a, KN05, GL85) in Table 1 to describe new data on lines 154-155.
10. Grammatical and typographical errors as well as spelling mistakes are revised and corrected, accordingly.
Reviewer 3 Report
The present manuscript, no. 1046385, describes some iron-oxides inclusions in sapphires from Vietnam.
Unfortunately, the study presentation is of low quality, with unorganized illustrations and tables. Also, I will recommend extensive English revision of this manuscript. All of these aspects make the text very difficult to read and follow. With all due respect to the Authors this manuscript left me the feeling that it was written in a hurry without too much care on the details.
As for the scientific part, there are also here some inconsistences. The Authors seem to not understand very well what laser irradiation means when dealing with Raman spectroscopy and how laser power affects the samples under examination by means of oxidation and phase transformations.
The minerals identification rises some uncertainties. For instance, wustite Raman spectrum is showed in Figure 4 where no frequencies of the peaks are indicated, only the assignment to other minerals (hematite, magnetite, wustite). Figure 4a shows the spectrum of wustite or magnetite? As the authors cite good papers on Raman of iron-oxides, they should know that wustite spectrum shows no additional bands and the main one appears at aprox. 650 cm-1, while in magnetite it is observed at 663 cm-1. I know that this is not a very easy task, but some X-ray diffraction would be necessary to confirm the structural data and to be correlated with the chemical results. This is just one example, I have doubts also on the other minerals described here. Therefore, the discussions and conclusions are not supported enough by the results.
Author Response
Responses to Reviewers
We would like to thank all reviewers for very their kind support and very constructive comments. All the comments and suggestion were taken for revision of the manuscript.
1. Classification – Terminology: the syngenetic inclusion are change to primary inclusion. Therefore, we revise some sentence to classification for the inclusion on lines 103-104.
2. Geological setting: more information of metamorphic, sedimentary and igneous rocks in the study area are added and properly discussed. To describe for geological setting, we have added figure 1 which showed the study area and tectonic structures in Southern Vietnam. According to above requirements of reviewer, we have changed geological map (figure 2) which showed all geological formations in the study area as well as revise some sentence to describe about geology of area study on lines 41-53.
3. Materials and Methods:
- General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1): sampling points are given in the figure 1 (figure 2).
- -Each and every figures in the manuscript must contain sample names– which again should be related to the geological map: all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217.
- Sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results: all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A.
4. My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section: more information about the discussion from the results is moved to the discussion.
5. For laser irradiation means when dealing with Raman spectroscopy: more information about the usefulness of laser irradiation as below - Record the Raman pattern and its alteration in wüstite - Detection the structures and compositional variants of ilmenite and hercynite We also revise some sentence to describe the usefulness of laser irradiation on lines 89-94.
6. How laser power affects the samples under examination by means of oxidation and phase transformations: Raman spectra of wüstite can be permanently transformed in their structures from magnetite structure (Fe3O4 ) to hematite structure (Fe2O3) under effect of high laser power.
7. Figures 4a, b, c (Figures 5a, b, c): frequencies of the peaks are added into these Figures. We also revise some sentence to describe these frequencies of the peaks on lines 189-193.
8. Figure 4a (Figure 5a) shows the Raman spectra characteristic of wüstite with structure in non-equivalent sites of nonstoichiometry wüstite which looks very similar to the magnetite (Fe3O4). Therefore, we also revise some sentence to describe this spectra on lines 235-259.
9. Unreliable total wt% between 91.6 and 95.9 wt% of several analyses are replaced or omitted. Therefore, we also revise some sample data (i.e., KN20a, KN05, GL85) in Table 1 to describe new data on lines 154-155.
10. Grammatical and typographical errors as well as spelling mistakes are revised and corrected, accordingly.
Author Response File: Author Response.pdf
Reviewer 4 Report
The article presents the results of a study of mineral inclusions in sapphires from alluvial deposits associated with Cenozoic basalts in southern Vietnam. As a result of a detailed study of inclusions composition using Raman Spectroscope and Electron Probe Micro Analyzer, it was found that the inclusions consist of intermediate members of an isomorphic series between wustite, hercynite and ilmenite. Using the data obtained, the authors constructed a model that explains the conditions for the sapphirine. The data interpretations seem to have been done well, also the experimental data obtained. So, the paper adds valuable new information and can recommend the paper for publication in Minerals but with minor revisions.
Comment:
According to the reviewer, the Fe2+/Fe3+- ratios can be calculated using the following method. Using the criteria from the article (Droop,1987), we first calculate the formula by the number of cationic positions in the formula, and then redistribute the Fe2+ and Fe3+ until the electroneutrality will be observed.
Author Response
Responses to Reviewers
We would like to thank all reviewers for very their kind support and very constructive comments. All the comments and suggestion were taken for revision of the manuscript.
1. Classification – Terminology: the syngenetic inclusion are change to primary inclusion. Therefore, we revise some sentence to classification for the inclusion on lines 103-104.
2. Geological setting: more information of metamorphic, sedimentary and igneous rocks in the study area are added and properly discussed. To describe for geological setting, we have added figure 1 which showed the study area and tectonic structures in Southern Vietnam. According to above requirements of reviewer, we have changed geological map (figure 2) which showed all geological formations in the study area as well as revise some sentence to describe about geology of area study on lines 41-53.
3. Materials and Methods:
- General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1): sampling points are given in the figure 1 (figure 2).
- -Each and every figures in the manuscript must contain sample names– which again should be related to the geological map: all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217.
- Sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results: all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A.
4. My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section: more information about the discussion from the results is moved to the discussion.
5. For laser irradiation means when dealing with Raman spectroscopy: more information about the usefulness of laser irradiation as below - Record the Raman pattern and its alteration in wüstite - Detection the structures and compositional variants of ilmenite and hercynite We also revise some sentence to describe the usefulness of laser irradiation on lines 89-94.
6. How laser power affects the samples under examination by means of oxidation and phase transformations: Raman spectra of wüstite can be permanently transformed in their structures from magnetite structure (Fe3O4 ) to hematite structure (Fe2O3) under effect of high laser power.
7. Figures 4a, b, c (Figures 5a, b, c): frequencies of the peaks are added into these Figures. We also revise some sentence to describe these frequencies of the peaks on lines 189-193.
8. Figure 4a (Figure 5a) shows the Raman spectra characteristic of wüstite with structure in non-equivalent sites of nonstoichiometry wüstite which looks very similar to the magnetite (Fe3O4). Therefore, we also revise some sentence to describe this spectra on lines 235-259.
9. Unreliable total wt% between 91.6 and 95.9 wt% of several analyses are replaced or omitted. Therefore, we also revise some sample data (i.e., KN20a, KN05, GL85) in Table 1 to describe new data on lines 154-155.
10. Grammatical and typographical errors as well as spelling mistakes are revised and corrected, accordingly.
Round 2
Reviewer 1 Report
Minerals - Open Access Journal
MDPI journal
Subject: Second review of: “Variety of Iron Oxide Inclusions in Sapphire from Southern Vietnam: Indication of Environmental Change during Crystallization” (minerals-1046385-peer-review-v2-1) submitted by Vu et al.
1st clarification – terminology
Authors wrongly use term “syngenetic” referring to primary origin of inclusions. Syngenetic and the opposite term epigenetic are used for description of relationship between time of formation of the ore deposit and the host rocks. Solid inclusions in minerals by definition are primary. Due to p/t/c changes primary solid inclusions can decompose to other minerals. This needs to be clarified throughout the manuscript.
Authors answer
Classification – Terminology: the syngenetic inclusion are change to primary inclusion. Therefore, we revise some sentence to classification for the inclusion on lines 103-104.
Reviewer comment:
Corrected
2nd clarification - Geological setting
There is a long-lasting scientific discussion on the origin of sapphires and associated zircon placer deposit from Central Highlands, Vietnam, with only weak relation of these deposits to Cenozoic alkali basalts in the region. Authors failed to summarise important facts from previous studies, whereas an important work of international group of scientists published in Minerals had been completely omitted (Sinh et al., 2019 Gem-Quality Zircon Megacrysts from Placer Deposits in the Central Highlands, Vietnam—Potential Source and Links to Cenozoic Alkali Basalts). Geological section need to be rework and extended, and important conclusion from previous research clearly stated.
Authors answer
Geological setting: more information of metamorphic, sedimentary and igneous rocks in the study area are added and properly discussed. To describe for geological setting, we have added figure 1 which showed the study area and tectonic structures in Southern Vietnam. According to above requirements of reviewer, we have changed geological map (figure 2) which showed all geological formations in the study area as well as revise some sentence to describe about geology of area study on lines 41-53.
Reviewer comment:
Figure 1 had been added – however – authors had added general description of the older formations in the area instead of requested different interpretations of relation between sapphire deposits and Cenozoic alkali basalts. Important facts and conclusions from previous studies (for example https://www.mdpi.com/2075-163X/9/2/89) are again not included. Why?
Partially corrected
3rd clarification - Materials and Methods
General failure of the manuscript is unclear presentation of the collected materials starting from their geological positions on the map (Figure 1). Each and every figure in the manuscript must contain sample names – which again should be related to the geological map. We are missing a comprehensive table with sample locations, names, sapphire description and inclusion types – and I would strongly advise authors to prepare such a table (or an appendix) in order to clarify obtained results.
Authors answer
Sampling points are given in the figure 1 (figure 2).
Sample locations, names, sapphire description and inclusion types –all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A.
Reviewer comment:
Sampling points are given in the figure 1 (figure 2). Corrected
Sample locations, names, sapphire description and inclusion types –all information about sample location, names, sapphire descriptions and inclusions types is given in a Table in appendix A. Corrected
4th clarification – Results
My strongest objection is related to Results section. Authors need to separate results from the discussion which is in current MS merged together. Results needs to be presented in order: mineralogy (microphoto, BSE, Raman), mineral chemistry (EMPA) objectively. The discussion should follow reworked results section.
Conclusions are weak and basically represent a summary of the previous extensive research in the region.
Authors answer
No direct answer found.
Reviewer comment:
Results are separated from discussion and presented as requested. – Partially corrected. Fig 9 Microphotograph and BSE image with appropriate discussion should follow Figure 3.
Order of presentation of the result is (including corresponding Figures)
- Microphoto
- BSE
- Raman
- Mineral Chemistry
Figures 8 and 10 with corresponding text should go to discussion (it is already data interpretation).
Table 1
Several analyses have total wt% between 91.6 and 95.9 wt% are unreliable and should be repeated or omitted.
Authors answer
Unreliable total wt% between 91.6 and 95.9 wt% of several analyses are replaced or omitted. Therefore, we also revise some sample data (i.e., KN20a, KN05, GL85) in Table 1 to describe new data on lines 154-155.
Reviewer comment:
Corrected
Figure 1
Authors are advised to insert location of the collected samples following aberrations in Tables 1 NS 2
Authors answer
Sampling points are given in the figure 1 (figure 2)
Reviewer comment:
Corrected
Figure 2, 3, 8
Please insert sample names for each of the presented microphotographs.
Authors answer
all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217.
Reviewer comment:
all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Corrected
Figure 4 to 7
Please insert sample names for each of the presented Raman spectra.
Authors answer
all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Therefore, we revise some sentence to add the sample names for the inclusion on lines 109-113, 115116, and 216-217.
Reviewer comment:
all the sample names are given in figures comprising figure 2 (figure 3), figure 3 (figure 4) and figure 8 (figure 9). Corrected
Figure 7
Please insert sample names for each of the presented spinel composition.
Reviewer comment:
Corrected
English is below internationally recommended level.
Authors answer
Grammatical and typographical errors as well as spelling mistakes are revised and corrected, accordingly.
Reviewer comment:
Corrected
Submitted MS will potentially rise an interest of the international audience, however due to needed improvement in Geological section, Results and Discussion, it is still not publishable in a current form and I recommend reworking it according to instructions and resubmit after major revision.
Yours sincerely
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
My decision (minor changes) was made based on the initial available manuscript which was a document with marked changes. The clean version can be accepted in the present form.Author Response
Thank you very much for your kind support. We have revised the manuscript accordingly.
Round 3
Reviewer 1 Report
Dear Authors,
almost there. Small intervention still needed in Geological section.
With best regards,
