The acid sulfate zone and the mineral alteration styles of the Roman Puteoli (Neapolitan area, Italy): clues on fluid fracturing progression at the Campi Flegrei volcano

Piochi, Monica; Mormone, Angela; Strauss, Harald; Balassone, Giuseppina

doi:https://doi.org/10.5194/se-10-1809-2019

Articles | Volume 10, issue 6

https://doi.org/10.5194/se-10-1809-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/se-10-1809-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 10, issue 6

Research article

|

30 Oct 2019

Research article |

| 30 Oct 2019

The acid sulfate zone and the mineral alteration styles of the Roman Puteoli (Neapolitan area, Italy): clues on fluid fracturing progression at the Campi Flegrei volcano

Monica Piochi, Angela Mormone, Harald Strauss, and Giuseppina Balassone

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Final revised paper (published on 30 Oct 2019)
Supplement to the final revised paper
Preprint (discussion started on 08 May 2019)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of manuscript solid earth 2019-53', Anonymous Referee #1, 16 Jun 2019
- AC2: 'Response to reviewers within the interactive comment section on “The acid-sulfate zone and the mineral alteration styles of the Roman Puteolis (Neapolitan area, Italy): clues on fluid fracturing progression at the Campi Flegrei volcano” by Monica Pioc', Monica Piochi, 17 Jul 2019
RC2: 'Piochi et al', Franco Pirajno, 19 Jun 2019
- AC1: 'Response to Pirajno Referee #2', Monica Piochi, 17 Jul 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Monica Piochi on behalf of the Authors (17 Jul 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Jul 2019) by Kei Ogata

RR by Franco Pirajno (06 Aug 2019)

RR by Anonymous Referee #1 (16 Aug 2019)

Suggestions for revision or reasons for rejection

I went through the revised version of the manuscript. The authors have made most of the suggested modifications and the manuscript has been improved. Nevertheless, there are still some points related to the interpretation of the XRD and FTIR data which need to be considered prior to acceptance. Also I still have reservations about the use of the term realm in the text. The points which need to be revised are the following.
1. XRD results. Firstly, there are XRD traces or patterns not spectra. There is no smectite present in figure S1f. The diffraction maxima at 25.5 °2θ and 30 °2θ belong to alunite (the authors should look carefully at the reference XRD pattern of alunite in S1e). The hump at low angle (~3 °2θ) corresponds to a d-spacing of ~30 Å. Such a d-spacing is not rational for this type of materials because it is indicative of a superstructure. Such a phase which corresponds to certain types of clay minerals is highly unlikely to form in this environment. The hump at this low angle is an artifact (i.e. continuous radiation). Also, in Fig. S1d all samples contain alunite. Illite/mica might be present only in sample MP-24-09-14 (Fig. S1d). I suggest that the authors look at their XRD traces again and modify the text accordingly.
2. FTIR results. The interpretations in the NIR region are erroneous. The bands in the area 4520-4610 cm-1 are combination modes i.e. neither OH-stretching nor OH-bending modes. Both bands in this region belong to kaolinite not alunite. This can be easily observed if one combines the OH-stretching modes at 3695 cm-1 and 3620 cm-1 with the bending mode at 915 cm-1. There is no solid evidence for the presence of other clay minerals in the FTIR spectra provided. On the other hand alunite is identified positively by the band sharp at ~3500 cm-1 as the authors correctly mentioned. The main text and the supplement should be modified accordingly.
3. The use of term realm: The definition provided by the authors for realm in the text is identical to what is known as alteration zone. I am not convinced that it should be used.
4. A few minor points have been highlighted in the attached script.

Referee Report: PDF

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ED: Publish subject to minor revisions (review by editor) (21 Aug 2019) by Kei Ogata

AR by Monica Piochi on behalf of the Authors (27 Aug 2019) Author's response Manuscript

ED: Publish as is (28 Aug 2019) by Kei Ogata

ED: Publish as is (16 Sep 2019) by Joachim Gottsmann (Executive editor)

AR by Monica Piochi on behalf of the Authors (20 Sep 2019) Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Monica Piochi on behalf of the Authors (28 Oct 2019) Author's adjustment Manuscript

EA: Adjustments approved (28 Oct 2019) by Kei Ogata

Short summary

The Campi Flegrei volcano in Italy displays hot fumarolic solfataras famous since Roman times. We use the solfataric mineralizations to investigate the local setting, evolution and geohazards. These provide information on hydrothermal activities that have been stable over the past 20 years. They reflect extreme conditions associated with the fluid overflow from subsurface and surface waters through a fracturing conduit. The solfataras are toxic and represent an extreme environment for life.