Comparative Flexural Response of Mineralized Massive Sulfides and Meta-Rhyolitic Rocks

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript: Comparative Flexural Response of Mineralized Massive Sul-
fi des and Meta-rhyolitic Rocks is interesting, because of comparing different branches of sciences, including petrography, mineralogy and engineering study. The article has good layout and generally was good documented. The main problem is to use the mineralogical vocabulary without geological background, and in some cases not clear or not correct meaning. The main comment are as follows:  

1. The introduction must be corrected and rewritten, according to the subject of the study. Missing fragments must be written.
2. The methodology should be extended an better explained.
3. Mineralogical and geochemical terms should be corrected, according to their meanings.
4. Figure no 11 must be of better quality.
5. The bibliography list should be improved
6. Detailed comments are included in the text.

In my opinion the manuscript cannot  be published in present form, it should be corrected as major revision and resubmitted.

Comments for author File: Comments.pdf

Author Response

Thank you for your comprehensive feedback. We appreciate your diligent review and the detailed comments provided within the manuscript. We have carefully considered all your points and will address each one thoroughly in our revised submission:

• Reviewer comments :The introduction must be corrected and rewritten, according to the subject of the study. Missing fragments must be written.

author's response : Introduction: In the revised version, we rewrite and expand the introduction to better align with the core subject of the study, ensuring all missing fragments are incorporated for enhanced clarity and completeness.

• Reviewer commnets :The methodology should be extended an better explained.

author's response : Methodology: The methodology section significantly extended and re-explained to provide a more detailed and clearer understanding of the research approach and techniques used.

• Reviewer commnets :Mineralogical and geochemical terms should be corrected, according to their meanings.

author's response : Mineralogical and Geochemical Terms: We  review and correct all mineralogical and geochemical terms to ensure they are used precisely and accurately according to their established meanings.

• Reviewer commnets:Figure no 11 must be of better quality.

author's response: Figure 11 Quality: we replaced with a higher quality version to improve its readability and effectiveness.

• Reviewer commnets:The bibliography list should be improved

author's response: Bibliography List: The bibliography list will be improved and updated to meet academic standards and ensure all relevant references are included and properly formatted.

• Reviewer comments: Detailed comments are included in the text.

author's response Thank you for your detailed review of our manuscript, We appreciate you providing your comments directly within the text. We've carefully addressed all the suggestions and modifications you highlighted in the manuscript text. We believe these changes have significantly improved the clarity and quality of our submission in the revised version .

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

I think that the paper can be substantially improved by the rewriting of certain sections describing the geology and mineralogy as they are quite vague and somewhat contradictory.  It is essential to better describe what the paper is setting out to do and how the conclusions can be utilized in the real world setting.

Comments for author File: Comments.pdf

Author Response

Thank you for your thorough review of our manuscript. We appreciate your insightful feedback, which has significantly helped us improve the quality of our submission. We have carefully considered all your suggestions and have revised the manuscript accordingly.

Below, we provide a point-by-point response to each of your comments, outlining the changes we have made.

• Reviewer comments regarding the language mistakes,

Author's response:  we made all required corrections throughout the manuscript according to the reviewer comments, and we revised the language carefully to avoid any grammatical mistakes.

• Reviewer comment :Photographs need more contrast as they look almost uniformly featureless.

Author response We removed the figure because it duplicated content already presented in Figure 1, which also showed half-core hard rock samples from mineralized and non-mineralized zones.

• Reviewer comment :“rom the photomicrographs presented as Figure 5 I am not sure the evidence points to replacement by pyrite. A much more common occurrence in such VHMS type mineralization is for early pyrite to be enveloped and/or replaced by base-metal sulphides.  The pyrite crystals generally exhibit good crystal structure with moderate degrees of corrosion or assimilation by the enveloping sphalerite.  what are the minor inclusions within the pyrite ?  i am not happy that sufficient evidence is presrented to justify this rather unusual paragenesis in a VHMS deposit.”

 Author  response “The photomicrographs in Figure 5 provide clear visual evidence of pyrite replacing sphalerite and chalcopyrite. In Zone A, the near-homogeneous pyritic matrix with relict islands of unaltered sphalerite and chalcopyrite at grain boundaries strongly supports pervasive pyritization.

In Zone B, the corroded margins of sphalerite grains and pyrite overgrowths encapsulating relict sphalerite further confirm that pyrite is the late-stage replacement phase.The gradational layering from Zone C to Zone A, showing increasing intensity of pyritization, provides additional support for this interpretation. Common Occurrence of Early Pyrite Being Enveloped or Replaced:

While it is true that early pyrite can be enveloped or replaced by base-metal sulfides in VHMS deposits, the textures observed in this study indicate the reverse process. The corroded margins of sphalerite and chalcopyrite, along with pyrite overgrowths, demonstrate that pyrite is the late-stage phase. The reviewer notes that pyrite crystals generally exhibit good crystal structure with moderate corrosion or assimilation by sphalerite. However, in this case, the textures show the opposite: sphalerite exhibits corroded margins and dissolution textures, while pyrite shows overgrowth features.

We appreciate the reviewer’s attention to detail regarding the nature of minor inclusions within pyrite and the significance of the observed paragenesis. We acknowledge that pyrite being the dominant replacive phase in VHMS settings is less commonly documented than the more typical scenario where base-metal sulfides envelop early pyrite. However, we believe that the microtextural relationships observed in our study provide compelling support for the proposed sequence.With regard to the minor inclusions within pyrite , these are interpreted as mechanically entrapped relicts of earlier-formed sphalerite and chalcopyrite , based on the following:

Inclusions occur preferentially at grain boundaries and exhibit irregular, fragmented shapes inconsistent with euhedral crystal growth. Their spatial relationship with pyrite grain boundaries suggests they were engulfed during pyrite overgrowth rather than being co-genetic phases.

No preferred orientation or lattice alignment is observed between the inclusions and the host pyrite, ruling out epitaxial growth or co-precipitation mechanisms. Instead, these features are consistent with mechanical entrapment during pyrite recrystallization or overgrowth.

The presence of embayed and corroded sphalerite grains, together with pyrite overgrowths enclosing relict sulfides, strongly supports the idea that pyrite grew at the expense of earlier mineral phases. The inclusions represent remnants of those phases that were only partially consumed during pyritization.Regarding the "unusual" nature of the paragenesis , we emphasize that the interpretation is based on consistent mechanical and textural evidence across multiple zones , showing progressive pyritization from Zone C to Zone A. The observed gradation in grain size, texture, and degree of pyrite dominance provides a logical framework for interpreting the evolution of the system.While we recognize that this style of paragenesis may be less common in typical VHMS systems, it is not without precedent. Late-stage Fe–S-rich fluids can drive extensive pyritization under appropriate conditions of temperature, fluid composition, and permeability, especially in structurally controlled or post-depositional hydrothermal environments.

”

• Reviewer comment: This photo looks like a sample from a typical exhalative VHMS deposit, even with potential slumping and sulphide-graded bedding.not sure i would interpret these features as being metamorphic fabrics

Authors response “Your observation regarding the photomicrographs is insightful and aligns with our re-evaluation of the textural evidence. We agree that the features observed, including potential slumping and sulphide graded bedding, are highly characteristic of primary depositional processes in exhalative VHMS deposits.We appreciate your critical assessment of our initial interpretation. Upon further review, we concur that these textures are indeed more consistent with primary depositional controls rather than being indicative of metamorphic fabrics. We have revised the manuscript to reflect this understanding, emphasizing the likely exhalative origin and the role of syndepositional processes in shaping the observed textures.

• Reviewer Comment: "Need better descriptions of each photomicrograph setting out distinctive features."

Author Response:We appreciate the reviewer’s request for more detailed descriptions of the photomicrographs in Figure 5. To address this, we have revised the figure caption to provide clearer and more comprehensive descriptions of the distinctive features observed in each zone. Below is a summary of the key modifications and additional details provided:

Zone A (Figures 5a, b): This image highlights the extremely dense, finely crystalline pyrite aggregates that form the dominant phase. Interstitial sphalerite grains are present but appear irregular and fragmented, consistent with mechanical entrapment during pyrite growth. These textures strongly suggest pervasive pyritization.

Figure 5b: This image further emphasizes the tight packing of pyrite grains and the presence of rare chalcopyrite inclusions. The sphalerite grains exhibit embayed margins, indicating active corrosion and replacement by pyrite.

Zone B (Figures 5c, d):This image shows a massive, pyrite-dominant assemblage with coarse-grained pyrite and sphalerite exhibiting intimate intergrowths. The sphalerite grains display corroded margins, confirming ongoing replacement by pyrite.

Figure 5d: This image focuses on relict islands of unaltered sphalerite trapped at pyrite grain boundaries. These trapped relics provide clear evidence of incomplete replacement and support the interpretation of pyrite as the late-stage replacive phase.

Zone C (Figures 5e, f):This image depicts a coarser-grained assemblage dominated by pyrite, with subordinate sphalerite, rare chalcopyrite, trace stannite, and abundant gangue minerals. Relict textures of unaltered sphalerite and chalcopyrite are partially enclosed by pyrite overgrowths, indicating less advanced pyritization compared to Zones A and B.

Figure 5f: This image emphasizes the less intense pyritization in Zone C, with larger sphalerite grains and more preserved relict textures. The gradational layering from Zone C to Zone A is evident in the increasing density and fineness of sulfide grains, correlating with the progression of pyritization.

By revising the figure caption to include these detailed descriptions, we aim to ensure that the distinctive features of each photomicrograph are clearly communicated. These descriptions highlight the textural relationships and microstructural evidence supporting our interpretation of pyrite as the late-stage replacive phase, replacing earlier-formed base-metal sulfides.

• Reviewer Comment:"This section should be rewritten to firstly describe the original alteration associated with the sulphide mineralization (typical VHMS associations such as epidote, silica etc. stockwork veing etc etc.). Then describe the superimposed alteration effects of the metamorphism. It is critical to avoid mixed messages especially when you describe certain assemblages (epidote, chlorite, silica veining etc) which are normal in VHMS deposits and avoid any misunderstandings about remobilization or metamorphic facies alteration assemblages superimposed on the original proptoliths."

Author Response:

We thank the reviewer for this important suggestion. In response, we have completely revised the relevant section to clearly separate the original hydrothermal alteration associated with the VHMS system from the overprinting metamorphic effects.

First describes the primary alteration assemblages typical of VHMS systems, including phyllic alteration (sericite), quartz ± amphibole ± epidote stockwork veining , and the preservation of relict volcanic textures.Then addresses the metamorphic overprint , including recrystallization, foliation development, and structurally controlled veining , distinguishing these from the earlier hydrothermal features.We have taken care to avoid conflating hydrothermal vein minerals like epidote and quartz with those formed during metamorphism, ensuring clarity regarding their origin and timing.By separating these two alteration events, we aim to eliminate any ambiguity and prevent misinterpretations regarding remobilization or metamorphic overprint. The revised version clarifies that while certain assemblages (e.g., epidote, quartz veining) are indeed typical of VHMS systems, later metamorphic processes have added complexity through deformation and recrystallization.

• Reviewer Comment: Better descriptions of each image required.

Author Response: Figure 6. The texture of the meta-rhyolitic tuff rocks. Images (a) and (b) show the un-equigranular blastoporphyritic texture, with finely crystalline sericite alignment defining foliation planes. Image (c) highlights silica alteration as fracture-filling micro-veinlets, while images (d) and (e) depict amphibole-rich veinlets and sulfide mineralization, respectively. Image (f) emphasizes advanced amphibole alteration, characterized by radial intergrowths within the host rock matrix.

• Reviewer Comment: "Individual descriptions required to make relevant points by each image."

Author Response:We appreciate the reviewer’s suggestion to provide individual descriptions for each image in Figure 6. To address this, we have revised the figure caption to include detailed explanations of the key features observed in each panel. Below is a summary of the changes:

Image (a): Describes the low-magnification view of the host rock, emphasizing the sparse distribution of sulfides (chalcopyrite, Cp) and the fine-grained nature of the host rock matrix.

image (b): Highlights the increased abundance and size of sulfides (chalcopyrite, Cp) at higher magnification, indicating a localized enrichment compared to Panel (a).

image (c): Provides a broader view of a sulfide-rich zone, showing the transition from a sparsely mineralized host rock to a more concentrated sulfide assemblage. The red box identifies a specific area for closer examination in Panel (d).

image (d): Focuses on the intricate textural relationships between sulfides (bornite, Bo, and pyrite, Op) at high magnification, emphasizing the complexity of the mineral assemblage.

image (e): Describes a different sulfide-rich zone dominated by sphalerite (Sp) and chalcopyrite (Cp), highlighting the diversity of sulfide phases and their coarse-grained nature.

image (f): Provides a detailed view of a sulfide grain boundary, focusing on the replacement relationship between sphalerite (Sp) and chalcopyrite (Cp), with sharp boundaries and embayed margins.

• Reviewer comment :How are the results of benefit in any application in the real world. the conclusions as offered could almost certainly have been arrived at without the testwork so please elaborate on the conclusions and applications.

Authors response :We are rewriting the conclusion. Hence, our comprehensive test work, including integrated petrographic, geochemical, and textural analyses, enabled us to draw far more robust and nuanced conclusions than could ever be achieved by examining samples alone. Specifically, we were able to:

• Quantify the relative abundances and precise spatial distribution of various sulfide minerals (e.g., chalcopyrite, bornite, sphalerite) at a microscopic scale. We didn't just "see" them; we understood their proportions and how they varied across different zones.
• Unravel precise paragenetic sequences through detailed textural analysis, observing relationships like replacement textures and overgrowths. This was critical in determining the chronological order of mineral formation and alteration. This directly addresses your question about whether this is a simple metamorphosed VHMS or a syn-metamorphic late replacement. Our findings strongly support the latter, identifying specific mineral assemblages and textural relationships that clearly indicate remobilization and late-stage fluid activity rather than just a metamorphic overprint on a pre-existing deposit.
• Identify key geochemical signatures linked to different mineralization phases. This included analyzing trace element variations within individual sulfide minerals, which serve as "fingerprints" of the fluid sources and conditions under which they formed. This level of detailed geochemical insight is simply not possible through visual assessment.

These conclusions provide a mechanistic understanding of the mineralization, detailing how and when the economic minerals formed and were redistributed. This moves our study from a descriptive account to a genetic one, which is invaluable for practical applications.

 

 

Regarding the reviewer comments in the revision file,

• For all grammatical and sentence corrections, we have made all necessary and required corrections in the revised version.
• For all figures and missing or unclear meanings, we corrected these issues in the revised version.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Suggested improvements have largely been adopted and in my opinion the MSS has been substantially improved.