Hydrothermal Alteration Mapping Using Landsat 8 and ASTER Data and Geochemical Characteristics of Precambrian Rocks in the Egyptian Shield: A Case Study from Abu Ghalaga, Southeastern Desert, Egypt
, Ahmed M. Abdel-Rahman 1, Antoaneta Ene 3,*, Hamdy A. Awad 4, Wael Fahmy 1, Hamada El-Awny 1 and Hesham M. H. Zakaly 5,6
Round 1
Reviewer 1 Report
good job of re-writing paper from an earlier version I reviewed for a different journal
Author Response
Reviewer 1Comment:
Good job of re-writing paper from an earlier version I reviewed for a different journal.
The authors would like to thank reviewer for their comments and recommendations that have helped to improve the clarity, readability and academic standing of this paper.
Author Response File: 
Author Response.docx
Reviewer 2 Report
1. This research combines remote sensing image analysis, geology, geochemistry and petrology to conduct Hydrothermal Alteration Mapping, which is relatively rare in the field of satellite image analysis, and is also a relatively new research in the field of earth science, so it has a certain degree of innovative. However, since there are too many professional terms, and most people are not familiar with the geology and environment of the eastern desert in Egypt, it is necessary to write it in a simpler and easier-to-understand way.
2. In this study, the common band selection and principal component analysis of remote sensing image analysis are used for image classification, and the recommended band and band combination methods are obtained. However, the research lacks indexes and evaluation data for checking the accuracy of interpretation with the real data of hydrothermal alteration and tectonic outline. The contribution of using remote sensing imagery is quite limited if future research still needs to be completed through a large number of ground surveys.
3. If you want to use remote sensing images for change analysis, whether the object is land cover, geological structure outline or geological attributes, the sensitivity test of band combination or index will generally be imported. However, it is a pity that no relevant content was evaluated in this study.
4. The combination of specific bands of Landsat 8 images can be used to display changes in specific formations in research, for example; 6/7 band ratio is used to display clay changes, 6/5 is used to distinguish ferrous alteration zones, and 4/2 band ratio Used to highlight differences in ferric iron. But what I am curious about is whether this conclusion can be effectively applied to other areas outside the study area, and this part lacks verification and explanation.
5. I believe that this article has a considerable contribution to the connection and value-added application of the band properties of satellite images and hydrothermal alteration mapping, but it will be difficult to convince relevant scholars if there is no convincing or specific evidence attached .
6. In this study, in addition to extracting structural line types, do DTM and related indicators also have the effect of adjusting hydrothermal alteration and structural contour classification in different topographical regions?
7. How hyperspectral satellite imagery can be applied to vertical non-planar structural classification, and whether there are some limitations in use deserve to be explained.
Author Response
Review Report (2)
We would like to thank you for giving us the opportunity to resubmit a revised copy of our manuscript “Hydrothermal Alteration Mapping Using Landsat-8&ASTER 2 Data and Geochemical Characteristics of Precambrian Rocks in 3 the Egyptian Shield: A Case study from Abu Ghalaga, Southeastern Desert, Egypt". We would also like to express our thanks and appreciate the interest that reviewers have taken in our manuscript and the constructive criticism they have given.
It is our belief that the manuscript is substantially improved after making the suggested edits. The manuscript has been revised to address the reviewer’s comments, also we have attached a point-by-point response to reviewer’s concerns.
Reviewer 2 Comments:
- This research combines remote sensing image analysis, geology, geochemistry and petrology to conduct Hydrothermal Alteration Mapping, which is relatively rare in the field of satellite image analysis and is also relatively new research in the field of earth science, so it has a certain degree of innovative. However, since there are too many professional terms, and most people are not familiar with the geology and environment of the eastern desert in Egypt, it is necessary to write it in a simpler and easier-to-understand way.
Answer: Thank you for your suggestion, have done.
- In this study, the common band selection and principal component analysis of remote sensing image analysis are used for image classification, and the recommended band and band combination methods are obtained. However, the research lacks indexes and evaluation data for checking the accuracy of interpretation with the real data of hydrothermal alteration and tectonic outline. The contribution of using remote sensing imagery is quite limited if future research still needs to be completed through a large number of ground surveys.
Answer: We thank you for your concern with respect to validation of remote sensing results using field studies. However, geological studies on structures and alteration mapping have been previously investigated for the study location Kindly refer to Shanein et.al 2015 and Amin et.al 2022. The report from these studies is clearly in line with our observation and have been used as evidence to validate information from remote sensing observations. Please consider line 540 to 543 and line 632 and 633.
- If you want to use remote sensing images for change analysis, whether the object is land cover, geological structure outline or geological attributes, the sensitivity test of band combination or index will generally be imported. However, it is a pity that no relevant content was evaluated in this study.
Answer: Dear Sir. We appreciate you for your relevant suggesting with regards to the testing of sensitivity for different bands in order to pre determine their suitability for mapping hydrothermal alterations. We will, however, draw your attention to the fact that the suitability of these bands used in the band ratio process for alteration mapping has been well established based on the spectral attributes of the alteration mineral under investigation. For your reference kindly consider Mia and Fujimitsu, 2012, Sabins 1999 for more clarification. However, trying to predetermine the suitability of these bands may be irrelevant to the research.
- The combination of specific bands of Landsat 8 images can be used to display changes in specific formations in research, for example, 6/7 band ratio is used to display clay changes, 6/5 is used to distinguish ferrous alteration zones, and 4/2 band ratio Used to highlight differences in ferric iron. But what I am curious about is whether this conclusion can be effectively applied to other areas outside the study area, and this part lacks verification and explanation.
Answer: Thank you for your suggestion, remote sensing methods applied to mineral exploration have been very successful and applied to different geological environment. The application of these ratios (6/7, 6/5 and 4/2) will be consistent in areas out of the study location. The use of geochemical data and petrographical methods are acceptable techniques for validating hydrothermal alterations observed from satellite data and this has been established in this study.
- I believe that this article has a considerable contribution to the connection and value-added application of the band properties of satellite images and hydrothermal alteration mapping, but it will be difficult to convince relevant scholars if there is no convincing or specific evidence attached.
Answer: Thank you very much, Previous studies have revealed the presence of hydrothermal alteration within the study location. A good coherence between these studies and satellite observation can serve as a valid justification for the reliability of remote sensing tool used in the study. Please consider line 540 – 543
- In this study, in addition to extracting structural line types, do DTM and related indicators also have the effect of adjusting hydrothermal alteration and structural contour classification in different topographical regions?
Answer: We thank you for the question. Geological structures have a pivotal role in the migration of hydrothermal fluids. However, DTM are mainly topographic data and remains an irrelevant attribute for mapping hydrothermal alterations.
- How hyperspectral satellite imagery can be applied to vertical non-planar structural classification, and whether there are some limitations in use deserve to be explained.
Answer: Dear reviewer, we thank you for your enquiry, however, the use of hyperspectral data is not within the scope of study.
Author Response File: Author Response.docx
Reviewer 3 Report
Here you can find the review of the manuscript remotesensing-1784777. The manuscript is conforming to the journal requirements and formats, and a suitable quality data have been included. Major recommendations are related to manuscript organisation and data presentation. Authors are also encouraged to take into account some comments and considerations.
I hope the following comments can help authors to improve the present manuscript.
MAJOR RECOMMENDATIONS
- “Section 2. Materials & Methods” should be divided in two sections: “Section 2. Materials” including the actual subsection 2.4, and “Section 3. Methodology” including actual sections 2.1, 2.2, 2.3 and 2.5. T. In this way only 3 subheadings are necessary, and not 4.
- Petrographical and geochemical characterisation must be relocated before sections 3.1, 3.2 and 3.3. In this manner, the results from applying Landsat and ASTER imagery can be deduced, highlighted and discussed.
MINOR SUGGESTIONS
- Figure 1. Scale and coordinates at the left image.
- Figure 3, photo 3. Correct: “foliation”, not exfoliation.
- Section 4 is not a real discussion. It is more likely a data presentation than a real discussion.
- Nothing is said about the petrographical and geochemical techniques in the methodology section: number of samples, analysis equipments, laboratory, why these elements have been analysed, …
- Figure 12. Complete page figure, please. If not, the lettering is unreadable.
- Tables 11 and 12. Only representative analysis are necessary.
- Last, but not least, I recommend to improve the format of the text: subheadings, tables, lettering size, … in order to get a unbeatable reader first look.
I urge the authors not to view this solely as a critique but a chance to improve this paper to convey their ideas and data in the best possible and most accurate manner.
Warm regards
Author Response
Review Report (3)
We would like to thank you for giving us the opportunity to resubmit a revised copy of our manuscript “Hydrothermal Alteration Mapping Using Landsat-8&ASTER 2 Data and Geochemical Characteristics of Precambrian Rocks in 3 the Egyptian Shield: A Case study from Abu Ghalaga, Southeastern Desert, Egypt". We would also like to express our thanks and appreciate the interest that reviewers have taken in our manuscript and the constructive criticism they have given.
It is our belief that the manuscript is substantially improved after making the suggested edits. The manuscript has been revised to address the reviewer’s comments, also we have attached a point-by-point response to reviewer’s concerns.
#-Reviewer 3 Comments:
1 - “Section 2. Materials & Methods” should be divided in two sections: “Section 2. Materials” including the actual subsection 2.4, and “Section 3. Methodology” including actual sections 2.1, 2.2, 2.3 and 2.5. T. In this way only 3 subheadings are necessary, and not 4.
Answer: Thank you, we did add each section in the suitable place. Also, we did arrange the figures and tables.
2 - Petrographical and geochemical characterisation must be relocated before sections 3.1, 3.2 and 3.3. In this manner, the results from applying Landsat and ASTER imagery can be deduced, highlighted and discussed.
Answer: Thank you, we did add each section in the suitable place. Also, we did arrange the figures and tables.
3-Figure 1. Scale and coordinates at the left image.
Answer: Thank you, done.
4-- Figure 3, photo 3. Correct: “foliation”, not exfoliation.
Answer: Thank you, Excuse me sir, the foliation is common in the metamorphic rocks especialized foliated rocks (schist) and it is a planar arrangement of structural or textural features in any rock type but particularly that resulting from the alignment of constituent mineral grains of a metamorphic rock of the regional variety along straight or wavy planes. But on the figure 3 it is the Exfoliation is a form of mechanical weathering in which curved plates of rock are stripped from rock below and common in igneous rocks such as (granite). This results in exfoliation domes or dome-like hills and rounded boulders. Exfoliation domes occur along planes of parting called joints, which are curved more or less parallel to the surface.
5- Section 4 is not a real discussion. It is more likely a data presentation than a real discussion.
Answer: Thank you very much, we agree with you, we preferred that the discussion of the research in terms of data presentation would be better.
6- Nothing is said about the petrographical and geochemical techniques in the methodology section: number of samples, analysis equipment, laboratory, why these elements have been analysed,….
Answer: Thank you, we mentioned these techniques in section (2.6) which is called (fieldwork and laboratory techniques).
7- Figure 12. Complete page figure, please. If not, the lettering is unreadable.
Answer: Thank you, the image has been placed 12 on a full page so that the letters are clear
8- Tables 11 and 12. Only representative analysis are necessary.
Answer: Thank you, I agree with you, the representative analyses (major and REE) are necessary. but we used one diagram (Or-An-Ab) which extracted from the CIPW normative minerals.
9- Last, but not least, I recommend improving the format of the text: subheadings, tables, lettering size, … in order to get a unbeatable reader first look.
Answer: Thank you, done.
10- I urge the authors not to view this solely as a critique but a chance to improve this paper to convey their ideas and data in the best possible and most accurate manner.
Answer: Thank you, sir, for giving us the opportunity to draw from your knowledge. I was very pleased with these valuable comments that enriched our paper.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
1. The authors have made complete and comprehensive revisions to the article, and the readability of the paper has also been greatly improved.
2. The authors have responded to the review comments and are acceptable.
3. The presentation of the description of professional terms has been greatly improved.
Reviewer 3 Report
Dear authors.
All suggestions and comments have taken into account. Only one minor comment: Section Results must be renumered as 4, and renamed as "Results & discussion".
Regards.
