Hello Dr Balcewicz,
I have now had the opportunity to examine the two reviews for your manuscript, your responses to their criticisms, and your revised version. Based on those, I am issuing a decision of “Major Revisions”. We will reconsider your manuscript once you have addressed the following points. Depending on the state of any further revised version you submit, an additional round of peer review may be required.

There are currently two problems with the current version of the manuscript that prevent its publication. The first concerns the quality of the presentation / writing. There are some sections of the text where far more detail than necessary is provided. Other sections of importance do not include nearly enough. As an example of the latter, important corrections and quantitative methodologies simply refer to a previous publication. You cannot of course fully redescribe methodologies produced by others here, but at least a general description of their function and purpose is required for the reader to grasp your work. In addition, the discussion often refers to the results section in only a qualitative manner (i.e. this location had higher 2D fracture connectivity than another location). Ideally, these metrics are all included in a figure or table that the reader can be referred to when making these and similar statements. Alternatively, the actual values can be reiterated in the discussion for clarity. In the current version, neither is done, which requires the reader to either remember the values or flip back through the paper. Both are troublesome given that the text is really quite verbose and long. There are also many grammatical mistakes with respect to english language grammar. Admittedly, most of these mistakes are minor, but there is a sufficient amount of them that makes reading difficult at times. I have noted many of these instances below, but the list is not exhaustive. I understand that Solid Earth is an international journal, and many of the authors do not have english as their native language. This is not inherently a problem, but I would ask that you attempt to address some of these issues in your next version.

The second issue concerns the length of the manuscript with respect to its “scope” or conclusions. I would like to see this manuscript be greatly shortened and streamlined. As it currently stands, the length is far above what is reasonable for the amount of data, their complexity, and what can be confidently concluded. Too much extraneous detail is included. For example, the geologic setting section is very detailed (although a bit difficult to follow), but very few of these details are referred back to in framing the results and subsequent discussion. This suggests that the level of detail included is more than what is required. The fracture fill and roughness data are similarly interesting, but do not seem to play a major role in your overall conclusions. Veining in particular is tough to extrapolate, because assuming that the veins do not predate the fold, then there is a difference in burial between the observed outcrops and the subsurface reservoir of 4 to 6 km. This would result in huge differences in local geochemical conditions, mineral kinetics, etc. The relevant story, as I see it from your data and conclusions, is: 1) the matrix permeability of the unit that is extrapolated into the subsurface is insufficient for energy production; 2) the unit at depth is likely fractured, where fractures parallel to the max horizontal stress may still be open; 3) the length, density, and orientation of fractures at the surface suggests good connectivity at depth, assuming the network is similar there; 4) Thus, the unit has potential for geothermal energy production. In that way, the study is useful and therefore deserving of eventual publication. Assuming that I understand these central conclusions correctly, the manuscript should be greatly streamlined around these ideas to emphasize them. My estimate is that the length of this manuscript could reasonably decrease by as much as 30% without sacrificing detail or clarity. In fact, I think the clarity would be greatly improved as a result.

Please do not hesitate to let me know if you have questions. There is definite potential for this manuscript to make a good addition to the special issue, and we appreciate your submitting it here. That being said, a bit more work needs to be done before it is ready to proceed.

Randy Williams
Topical Editor

4-5: Please revise this sentence for grammar/clarity. Please pluralize “depth”. What is a permeability “rate”? How does one study “permeability rates with sufficient conductivity”?

Introduction: This is generally well written from a language clarity perspective. It is also, however, a bit less focused than would be ideal. I think the paper would be very well served by a judicious rewrite of the introduction, with a specific emphasis on getting to the “point” of this study a bit more quickly and with only the relevant information included. At the very least, some additional figures (e.g. maps) would be very helpful in making the first paragraph accessible to the reader.

51: Please change “associate” to “associated”.

55: What exactly is meant by “mechanical conditions”?

57: Please change to “...geological ambiguity and to characterize…”.

63: What exactly is meant by “stability” in this case?

73: Please change to “...at outcrop and sample scales”.

74: Please change “fractured” to “fracture”.

77: I do not understand this line as written.

82-84: I am not sure this foreshadowing is necessary, but ultimately it is your choice.

87: Please revise for language clarity.

Geological Setting: As stated above, I think this paper would benefit from some streamlining. Part of that would involve considering exactly which aspects of the geologic history are strictly relevant. If kept more or less as is, substantial revising for english-language clarity will be required.

90: Revise for clarity/grammar.

92-93: Revise for clarity/grammar.

Study Areas: I feel there are many redundancies between this section and the previous. Ultimately, the could be easily combined and substantially reduced in length.

135: How is a tectonic setting “massively affected” by an anticline? This seems to be putting the cart before the horse.

171-174: I am having a great deal of trouble understanding these lines as written. Also, I am not sure I would describe beds with a dip direction of ~330 as comparable to those with a dip direction of ~020. That is nearly 50 degrees of difference.

176-179: I think you could reasonably just call them “fractures”, specifying that the term includes veins but does not include open space along bedding planes or schistosity. It is in the title of the paper afterall. I appreciate the attempts to be explicit, but this is a journal for geoscientists.

193-194: Please revise for clarity.

203: Again, this is a journal for geoscientists. You could very easily just say “The dip and dip direction of the intersecting fractures were recorded”.

305-310: Suggest using azimuth ranges for fracture sets, as they are far easier to understand than long strings of NNW-SSE, NE-SW, etc.

313: “Paleofilled”?

319: What is the differentiation between a filled fracture and a closed fracture?

320: Does the use of the term significant imply that a statistical analysis was applied?

Field Discontinuity Observations: In light of the provided tables, this exhaustive description of the data really does not seem necessary. A general overview of the relevant findings would suffice.

397-409: No tables or figures to cite with this information?

410-411: Sorry, but I am unable to follow this sentence?

423-448: So you also did all these analyses on a single vein sample? Can you provide some text justification for why? What was the goal?

470-485: The reader cannot reasonably assess your interpretations regarding the relative geometry of the fractures and regional structures unless you reference some stereonets that also include the orientation of the regional structures. Reviewer #1 suggested that the fracture orientations be restored to their “original” orientations through an unfolding procedure. This is a good suggestion, and it is not clear to me why that was not done? I do not agree that this “exceeds” the scope of the study as stated in the response letter. It would seem to be well within the scope of the study.

541-543: Please be more specific as to why this interpretation is valid. Only a citation is given. Evidence should also be provided.

546-547: So, you feel that this fracture set is most promising for exploiting geothermal energy, but you also think it is “highly probably” filled with calcite cements? I`m confused. Are the calcite cements only occluding a small portion of the fracture porosity? Else, sealed fractures generally make for poor conduits, no?

562-563: What is the typical aperture of these fractures? Seems like the probability of detecting them seismically is extremely low? There is almost certainly information already out there that would allow you to evaluate this claim.

565: What does the percentage of calcite filled fractures have to do with any specific tectonic origin?

Section 4.2.2: This is really quite difficult to follow.

566: A “slight” rotation. Did you evaluate statistically if there is a significant difference between the two orientations. Lots of methods are available to do this. See paper by Roberts et al. JSG, 2019 on statistical analysis with structural data. Figure 7 seems to show a slight rotation only at Honnetal?? The other two cites seem essentially the same.

580: Field scale?

587: Seems highly probably that they are underestimated rather than “might be”.

585: That analysis needs to be summarized. This manuscript has too much of a tendency to just refer the reader to other sources on important points of methodology or conclusion. That is reasonable to do only in some cases. This is not one of them, as the reader cannot be expected to read so much external material in order to understand what was done here.

593: I never saw a probability of interconnection listed, so it is not clear what “comparable” to that would be.

594: Again, this statement seems very qualitative. You have quantitative estimates. Please refer back to them here explicitly (i.e. the actual values). Better still, refer to a figure or table that includes them.

597: Again, please reference the actual estimates. Moreover, why do these metrics not appear in any figures or tables?

605: Not overly clear to me what this paragraph has to do with fracture connectivity?

635: This is one vein. How do we use it to infer anything about a target horizon?

640: So to summarize results: 1) matrix permeability would be insufficient for geothermal energy production; 2) Fractures may be present at depth based on outcrop, and those parallel to the max horizontal stress are most likely to be open and therefore productive; 3) Based on fracture length and orientation observed at the surface, there may be a well connected network at depth. These are useful conclusions, but they could be stated much more succinctly.

Hello Dr Balcewicz,
Thank you for providing a revised version of your manuscript for review. I feel that substantial improvements have been made in this version. I do feel, however, that additional improvements are necessary before the manuscript can proceed to typesetting and publication. Please examine and address the comments below. These are relatively minor, and it is my hope that additional revisions will not be required after these are completed. As such, you should double check the entirety of the manuscript to be sure it is in a state you find acceptable, as you may not have the opportunity for additional changes once you submit revisions.

The official status of your manuscript is: "Publish subject to minor revisions".

Cheers,
Randy Williams

General comment: Joints versus discontinuities. Used interchangeably. Either stick with discontinuity throughout, being clear about which type in discussion when relevant, or discard discontinuity and simply reference the structure type (e.g. joint vs shear fracture vs vein) directly in each relevant instance.

6: “...FOR which…

10: “Discontinuities” is too vague for the abstract. Please state exactly what was measured / observed in a paranthetical.

21: Sorry, I do not follow the logic here of why filled fractures would be a particular aspect that one would want in a geothermal system. Hopefully that is explained later in the manuscript. No rationale is presented here as to why those fractures would necessarily be re-opened or experience any dissolution.

25: I think this last sentence is unnecessary. Moreover, I do not understand its link with the rest of the abstract. The fracture reactivation discussion here is presented without any background.

28-44: On some level I appreciate this background, but it really is not necessary. The introduction would be well served by being yet more focused (although I do appreciate your previous efforts to provide more focus relative to the original submission). Honestly, if you simply used the text in lines 46-69 as the introduction that would be sufficient, but adding in a few of the details from the preceding paragraphs would also be helpful. This is more a style issue than anything else so the choice is yours, but that is my recommendation.

55: Remove capitalization of “Since”.

63: Please adopt the English spelling of “facies” for this manuscript.

71-72: How does a mountain belt “result” from a shallow sea? Please revise for clarity.

77: Expansion of what? The sea? How is that differentiated from the idea of transgression which is subsequently mentioned? Eustatic sea rise vs subsidence related?

84: Crustal expansion? What exactly is meant by this?

114: How does a regional tectonic setting result in an anticline or any other specific structure?

174: If the fractures have any significant roughness at outcrop scale then the aperture by definition is variable. Can you elaborate on this measurement? Was it a minimum, maximum, or else somehow “representative”?

217: “Plane parallel”? Should this be “bedding parallel”, or perhaps more accurately cut perpendicular to the core axis?

276: Are these mean or average orientations? If so, please specify that.

368: “Highly related” is unclear. I would say they are “consistent with” folding.

383-384: First you say this is basically unknowable, but then you speculate on a cause. Why not just state more simply that the exact cause is unknown, but it may be due to local stress anomalies accumulated through time?

402: “Towards THE core of THE reef formation”??

461-462: I don’t get this comparison. Fractures that are filled with cement are by definition not open.

465: “Before utilizing” what, exactly?

472-473: Does a consideration of fracture connectivity not by definition require a consideration of dispensation in orientation? For example, fractures that have strongly consistent orientations are likely to exhibit poor connectivity.

505: Please change “conclude on” to “infer”.

517: Please restate the spatial scale of the wavelength so that the reader may consider the localization of fracture porosity in the rocks.

519-521: I do not follow this argument as written. Please clarify. How would locally distributed, heterogeneous fracture networks contribute to fluid flow? As written it sounds like fracture porosity at this scale is NOT connected?

530: I would rearrange to say its dipping at XX degrees and likely occurs at a depth of YYYY meters.

534-535: Suggest rephrasing to “Outcrop investigation suggests that this unit could act as a naturally fractured reservoir at depth”, or similar.

536-537: Why would numerous tectonic events and fracture reactivation necessarily produce smooth fractures?

538: Suggest rephrase to “We suggest that GEOTHERMAL EXPLORATION EFFORTS focus on …” or similar.

540: This sentence clashes with the one before it. First you argue they are likely open, not you say many are likely closed. Did examination of the calcite veins at the surface indicate a history of periodic reopening? This should be easily detectable from the morphology of the calcite crystals (i.e. crack seal veins?).

546: “Despite THIS”.

Dear Dr Balcewicz,
Thank you for preparing this most recent revised version. I am pleased to inform you that I am recommending publication of the manuscript without further revision. From here on you will work with the editorial office for any remaining issues, but please do not hesitate to reach out to me if I can be helpful in some way. Thank you for submitting this work to the special issue. I will look forward to seeing it published shortly.

Best,
Randy Williams
Topical Editor