Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

I have read your fruitfull review, but unfortunately couldn't  find in it any information about  Kara-Bogaz-Gol  deposit. I think that addition of some information about this  deposit could improve your review. Information about it you can take for example in the paper of Kosarev et al. (2009).

 

Kosarev, A.N., Kostianoy, A.G. & Zonn, I.S. Kara-Bogaz-Gol Bay: Physical and Chemical Evolution. Aquat Geochem 15, 223–236 (2009). https://doi.org/10.1007/s10498-008-9054-z

Author Response

Thank you very much for your review and suggestion to include information in our article about the Kara-Bogaz-Gol deposit. We agree that this might be an very interesting example of salts formed at present by solar evaporation of relatively fresh waters. We completely agree that solar evaporation of saline waters might be involved in the forming of many salt deposits albeit for reasons given in our article, not the only process of importance. In our article, we have chosen to present evidence where the current theory of solar evaporation of water from the ocean does not provide a satisfactory explanation. We feel that, although Kara-Bogaz-Gol being a very interesting case, it does not fit the scope of our article.

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript detailed reviewed some published papers in terms of solid evaporate, brines, and fluids with high salinity in deeper Earth. I agree with the authors' idea that solar evaporation is not the only way to form evaporites and hydrothermal in the deep crust and mantle would be an alternative way. However, the evidence in this paper doesn't seem to support the current conclusion.

(1) Salts in seawater are not only sourced from water-rock interaction but most likely from the riverine input.  And these solutes are large from the continental weathering of outcropped rocks and then input into the river water. Thus, it is inappropriate to overemphasize the contribution of the deep crust and mantle to the salt content of seawater.

(2) Solutes from brines in deep-seated basins are difficult to trace their sources, but more papers indicate that water-rock interaction is the main contribution. Thus, nobody would say the deep brines are the result of solar evaporation.

(3) Evaporites will be formed when the brines beyond the concentration of ions precipitated by crystallization either by solar evaporation to lose the water content or add the solutes in water mass. From the observation in modern salt lakes, solar evaporation and increased solutes would help to evaporate precipitation. Thus, hydrothermal probably promotes the evaporate forming, especially to those salt giants. But it is not a common way to form evaporites. 

(4)  By the way, I don't like the lengthy expression in the text and wordy sentences from one or two citations. To prove their ideas, authors usually use one or two references and cite them in large paragraphs.

Author Response

Thank you very much for your review and detailed comments. Our reply are as follows:

1. The main topic of our article is to present evidence that does fit the current theory of salt giants forming by solely by solar evaporation of seawater. Salts in the sea ultimately must have come from the interior of the Earth due to water-rock interaction. There are direct ways and indirect ways for this to happen and during the processes, salt may exist as solids, as HP/HT vapours and as brines. Sediments or igneous rocks might serve as intermediate "storage sites" for salts where rivers may indeed contribute in transporting salts back to the sea.
2.  We agree on this point however, we would argue that the ultimate source for the rock salinity deserves more attention.
3. We agree that solar evaporation is a fact involved in most salt deposits and also working actively on saline fluids not sourced directly from the sea. We think the latter source is somewhat underestimated and under-published. Salt deposition might also occur at considerable depth, due to thermodynamical properties of salt-water solutions at elevated temperatures.
4.  Our choice of citations was motivated by our wish to enhance readability  and reduce the need for readers to go into all the references themselves. We probably have not found the best way to achieve this.

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript Review: Minerals-2890108, A Challenged Evaporite Paradigm?

I have carefully read the manuscript (minerals-2890108) titled "A Challenged Evaporite Paradigm?" by Johnsen et al. The manuscript has been submitted for publication in the Special Issue: Gypsum Crystals: The Importance and the Role of Calcium Sulphate in Past and Modern Environments. In special issues, review papers are generally welcome. The authors present a modest review on evaporites, consulting 54 articles. The text is well-written and clear, although the presentation of the references does not comply with the requirements of Minerals.

The authors provide a superficial analysis of some solid salt deposits, aiming to support the view that the formation of salt accumulations occurred due to causes other than evaporation generated by climatic processes (sun). They advocate for a new model to explain large salt accumulations in different tectonic and environmental settings. The authors also use noble gas data observed in brine inclusions to support this thesis. However, these gases are generated by the direct decay of uranium, thorium, radium, potassium, and other radioactive isotopes present in rocks on the planet. They are usually dissolved in bodies of water before being released into the atmosphere.

Furthermore, the authors use associations of hydrothermal minerals to defend the thesis that large salt deposits have a significant contribution from mantle-derived hydrothermal waters. However, they do not delve into explaining this model or present the relationships between these minerals and the analyzed deposits (reworked, in situ generated, syn-depositional, post-depositional?) and mineral paragenesis.

The authors analyze papers that present geophysical observations investigating deep zones of the crust and mantle in compressional tectonic settings using magnetotelluric and seismology data. They bring interesting observations about these environments but explore geochemical modeling processes and mineral content superficially for the Minerals Journal.

In one of the paper's conclusions, the authors cite the article by Esedo et al., 2012 (not listed in the references), demonstrating difficulties in understanding the processes of basin formation and accumulation space generation for sediments.

Moreover, the authors do not explore the concepts of cyclicity or the processes of sedimentary basin formation in various tectonic contexts and their impact on the formation of different minerals. They do not present models for salt precipitation in various sedimentary environments, their associated sequence, and hydrochemistry, nor the ideal cycles of evaporitic sequence deposition or salt deposition rates. Additionally, they do not provide a classification of evaporitic deposits and their controversies. The authors also fail to explore the relationship between evaporites and sequence stratigraphy and/or plate tectonics. They do not delve into the topic of salt tectonics.

Based on the above, I do not recommend the publication of the manuscript in this Special Issue, as suggested by the authors. In my opinion, it is an incipient review for such a broad and controversial topic as the disposition of large evaporitic deposits. Additionally, this Special Issue is specifically focused on the topic "Gypsum Crystals: The Importance and the Role of Calcium Sulphate in Past and Modern Environments."

Best regards.

Author Response

Thank you very much for thorough comments to our article. The intention of the article was to present important observations that are not supporting the current theory for the formation of giant salt deposits by solar evaporation of seawater.

If we were to include all the subjects you miss in our article, it would have been much larger and the intended message substantially diluted.

Regarding your comment on noble gas data. We feel that your comment: "They are usually dissolved in bodies of water before being released into the atmosphere"  in addition to the actual data presented in our article, kills your argument. The observed concentrations are way off if your model was correct.

It was not the intention in this article to present an alternative model for the formation of salt deposits. The intention was to promote the need for a revised model - based on the observations that were the prime subjects of our article. Comments related to an anticipated model are not valid in our view. As they say: The devil is in the detail- and we have not presented the details.

We do indeed understand the formation of sedimentary basins - also when including isostasy and different reasons for subsidence- or apparent subsidence, that are currently overlooked by many.

Regarding salt tectonics - to stick to our scope, we concentrated only on the observations that might not be entirely explained by the current paradigm.

We have presented several observations and subjects where even one of them would be sufficient to question the current evaporite paradigm. This is in accordance with the theory of science. We cannot see that you have refuted or eplained away any of these observations/subjects.

We will check the reference list one more time to make sure that all references are included.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors presented their responses, but I still argue the absolutist statements. Yes, the evidence they presented shows the underestimated mechanism from the deep earth, but we don't preclude solar evaporation. Just mentioned in lines 917-919, no marine fossils may relate to the salt tolerance of marine species and pollen can be transported by river or airflow. And you can't just conclude that it ruled out the seawater solar evaporation. So in the whole text, you can show the author evidence from the literature, but most importantly, your statements and conclusions should be cautious and leave room. I encourage you to revise and recommend publishing after minor revisions.  

Author Response

Thank you for your recommendations and comments. I will go over the ms once more and moderate "absolutist statements" that are unwarranted.

As stated before, we do believe that solar energy is involved in creating many of the giant salt deposits. Our main argument is that the evaporating brine did not come directly from the sea. We have presented evidence from many fields of science that are indicative of another mechanism that provides another source for the evaporating brines. The evidence does not constitute unrefutable proof but it significantly weaken the current theory.

Regarding the question of "no marine species" in the salt , there is lot to be said. Normally salt is used to preserve food because very few bacteria thrive in very salt waters and among the few are those that harvest energy from sunlight via carotenoid-based capture of light (those that make some salts and Flamingos red). Red salt therefore is proof that the salt surface was exposed to sunlight. However, all salts are not red and anyway, this evidence does not impy that seawater is the only possible source for the salinity.

If a whole ocean basin is evaporated to such an extent that solid salts form at the bottom, inevitable some of the very varied marine life will die and end up in the salt layers. The fact that pollen is found in salt, is a proof of the resilience of pollen, but also proof of the possibility for preservation of oranic matter in general within the salts. Of course, pollen can be found anywhere. We must  assume that all evaporating basins started their life as a normal sea before being secluded from the oceans. There should therefore be lots of marine lifeforms available to die and produce fossils or imprints, as the salinity became toxic.

In addition to this, the combination of isostatic considerations and the requirement for special tectonic mechanisms and restricted seawater transport channels into the evaporating basin (that would leave both erosional and depositional evidence related to distance from inlet) are problematic for the theory of direct evaporation of seawater.

However, is is physically possible and an opening should be made in our ms for this to be the case.