Seeps and Tectonic Structure of the Hydrothermal System of the Panarea Volcanic Complex (Aeolian Islands, Tyrrhenian Sea)

Round 1

Reviewer 1 Report (Previous Reviewer 1)

The manuscript "Seeps and tectonic structures of the hydrothermal systems ... " by F. Spagnoli and others is a major improvement over an earlier version.  Each of the several problems pertaining to the earlier version have been adequately addressed.  I am particularly impressed with the revised introduction and the important information added to the end of the discussion section. The current version is important and will be of interest to volcanologists, environmental geologists, and anyone interested in the release of carbon dioxide from the sea floor.

PS: the reverence you asked about is G. N. Eby (2006) on the lakes of Cameroon. There are also some interesting carbon dioxide papers by M. Eby.

The English is OK but there are still a few typos.  For example, on line 89 it should be bacterial mats not bacterial maths.

Reviewer 2 Report (Previous Reviewer 2)

Dear editor,

I was satisfied with the changes that the authors made

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript "Seeps and geological set up of the hydrothermal system of the Panarea volcanic complex ..." by F. Spagnoli and others is interesting and important. It is well written, well organized, and the product of considerable effort using state of the art technology. As is always the case there are, however, some improvements that could be made. I have some questions and suggestion that should be addressed in order to accomplish such improvement.

Line 2 – "set up" should probably changed to "structure".

Line 16 – Insert "measurement of " after "with"

Line 17 – Change "allowed describing" to "allow descriptions of"

Line 25 – Change "allowed to" to "allowed us to". This mistake is found throughout the manuscript.

Line 28 – Change need to needed.

Line 30 – Change "setup" to "development" or "application".

Note: only a few of the grammar mistakes will be made beyond this point.

Line 36 – What kind of volcanic rock is it? basalt, andesite, rhyolite? How permeable is it? vesicular, pyroclastic, or massive?

Line 54 – Describe the "massive sulfides". One of my biggest disappointments in this manuscript is the near absence of mineralogical information. Most readers seeing "hydrothermal system" in the title will be looking for hydrothermal minerals and metal content.  

Line 56 – What are the Ba, Pb, and Zn minerals and is there any Mn build-up?

Line 57 – What are the iron minerals? Most readers will want to know.

Line 58 – "recent volcanic outcrops" ??;  I thought the whole area including most of Italy was made up of recent volcanic outcrops.

Line 106 – Yes, there needs to be the addition of good descriptions of the mineralogical and geochemical characteristics. (Figure 18c is not enough).

Line 381 – Change "tectonical" to "tectonic" here and throughout the manuscript.

Line 384 – How can the authors distinguish between "sea level rise" and submergence? Isn't submergence quite likely in an extensional setting with common grabens?

Line 417 – Re-word "...also to a less or deep hydrothermal fluid circulation.."

Line 418 – Change ad to and

Line 475 – Change "extent" to "extend"

Line 497 – Name the hydrate oxides.

Lines 502-505. This is very important and can have very dangerous consequences. Carbon dioxide in high concentrations can quickly kill fish and people. The authors might want to point this out and read about cases where this has happened. Eby is one good source. Acidification can also cause "dead zones". Is this a problem?

Lines 519-521 – This is interesting and should be expanded.  What is the area that is generating the 1500 tons/year? Can the authors describe a comparable source of CO2, for example the amount of gasoline or coal consumption? This might increase the interest among readers.

Line 554 – Change budged to budget.

Line 554 – One factor that is ignored is temperature.  Warm water can hold much less CO2 than cold water. How will the global warming of sea water change its ability to absorb the hydrothermal CO2 described by the authors?

Another question pertains to the amount of CO2 generated by the Panarea volcanic complex compared with others. Is it unique, relatively high or low?  And have the authors thought about the source of the carbon? Are there any known limestone, dolomite, coal, oil shale, or marble formations that were buried or subducted under the volcanics, or any marine carbonate sediments? Are there any calcite filled vesicles in the basalt?

The quality of the English needs to be improved.  It is readable but there are several mistakes. 

Reviewer 2 Report

Dear Editor! I carefully read Spagnoli et al.'s manuscript on the hydrothermal system of the Panarea volcanic complex. The authors have done interesting work and provided excellent images of the seabed and hydrothermal structures. They proposed an original model for the unloading of CO2-seeps. However, I have a few comments that could improve the manuscript. It also feels like the authors were in a hurry when preparing the manuscript, so it is not very well edited.

The title of the work uses the word "geological", but the manuscript contains very little information about the geological structure of the region. The available information concerns mainly the tectonics of the region. I believe it would be correct to replace the word “geological” with the word “tectonical” in the title of the manuscript.

Figure 1. I don't see any geological information in the picture - only bathymetry and tectonic elements. Remove the word “geological” from the caption. Explain in the legend the meaning of the red arrows and lines in the inset in the figure.

Line 63: "on the" repeated twice

Line 90: The authors report carbon dioxide emissions from seeps, but hydrothermal seeps are known to often contain methane plumes. Was methane detected in your research? Methane can be generated due to CO2 reduction, since CO2 is unloaded in seeps. You should write at least a few lines about methane: is it present or absent and why?

Figure 4: It probably doesn't make much sense to plot salinity on a graph since it is a straight line at the specified vertical scale. You can simply indicate the salinity value in the text of the ms.

Figure 5: Move the "red dot" to Fig 5a) from Fig 5b) in caption.

Figure 8: What about fig 8c in caption?

Line 262: It is written “see 3.2 for >0 definition” but this text is already inside 3.2! Where >0 definition here?

Line 269: Fig 7 do not contain the g-j figures

Figure 19b. Instead of "light blue dotted lines", you should write "dark blue ones". And vice versa - instead "dark blue dotted-dashed lines" - "light blue...".

Doesn't sea water penetrate down through faults?

I believe that the manuscript would have benefited from a more detailed description of the geological structure of the rocks in which hydrothermal activity occurs. What kind of rocks are these, what age are they, how were they formed? At least half a page of geological information would be very helpful to readers who are not familiar with the geology of the region.

In conclusion, I would like to say that the work is interesting and can be published in Geosciences after some improvement.