Alteration of Feldspathoids Changes pH of Late-Magmatic Fluids: A Case Study from the Lovozero Peralkaline Massif, Russia
Tingting Shen
Round 1
Reviewer 1 Report
Review of manuscript “Alteration of feldspathoids changes Ph of late-magmatic fluids: a case study from the Lovozero peralkaline massif, Russia” by Mikhailova et al.
Dear authors,
I am very interested in this manuscript, the paper described in detail about the late-stage metasomatic alteration of rock forming minerals Nph and Sdl. This alteration leads to an increase in the Na/Cl ratio and pH of the fluid. And the increase in pH stabilizes hyperagpaitic minerals. The paper is well written, and the method of analysis and the data are well presented and described. I suggested to publish this paper in Minerals after minor revision.
General comments:
Throughout the text, the information about the minerals (nepheline and sodalite) alteration in several kinds of rocks from the Lovozero peralkaline massif, Russia was described comprehensive and discussed the principle about hyperagpaitic minerals’ formation. The data presented and methods used are reasonable and diversiform. One problem should come into notice is that, there are some duplication in the text. Such as, in the Abstract part, Line 20 to Line 23, the two sentences stated the same thing.; Line 57 to Line 67 the same reactions are repeated three times throughout the text. And every time, the abbreviations of the minerals are listed. Because the abbreviations are listed in Table 2, with no need for describing them everytime. Above all, regroup the text a bit to make it more succinct.
There are still some small mistakes listed as following, please check.
Specific comments:
Line 98: here use 360-370 million years, while in Line 11 using 360-370-Ma; Line 97 use 650 km2, while in Line 100, Line 107 using 1700 meters, 100 to 800 meters, Line 124 using 5 m. Please make these units keep consistent.
Line 183: here should be Table 2
Line 190:cited “Table 2”, I think should be Table 1,Yes?
Line 193: here use 15 modal %, while in Line 131 Table 1 use mod.%, please be consistent.
Line 252: use Figure 5c to replace “Fig. 5c“, to keep consistent.
Line 313: here cite (Figure 4f, g)
Line 358: Table 6, please change it a bit, because the readers could not distinguish which ones belong to “Fresh urtite” and which ones belong to “ Altered urtite”.
Line 378: please add more explaination about Figure. 8b, I feel confused about this figure.
Author Response
We appreciate the time and effort that the reviewer has dedicated to providing your valuable feedback on our manuscript.
Point 1. One problem should come into notice is that, there are some duplication in the text. Such as, in the Abstract part, Line 20 to Line 23, the two sentences stated the same thing.; Line 57 to Line 67 the same reactions are repeated three times throughout the text. And every time, the abbreviations of the minerals are listed. Because the abbreviations are listed in Table 2, with no need for describing them everytime. Above all, regroup the text a bit to make it more succinct.
Response 1. We shortened the text, removed duplications and unnecessary abbreviations.
There are still some small mistakes listed as following, please check.
Specific comments:
Point 2. Line 98: here use 360-370 million years, while in Line 11 using 360-370-Ma; Line 97 use 650 km2, while in Line 100, Line 107 using 1700 meters, 100 to 800 meters, Line 124 using 5 m. Please make these units keep consistent.
Response 2. Corrected.
Point 3. Line 183: here should be Table 2
Response 3. Corrected.
Point 4. Line 190:cited “Table 2”, I think should be Table 1,Yes?
Response 4. Corrected.
Point 5. Line 193: here use 15 modal %, while in Line 131 Table 1 use mod.%, please be consistent.
Response 5. Corrected.
Point 6. Line 252: use Figure 5c to replace “Fig. 5c“, to keep consistent.
Response 6. Corrected.
Point 7. Line 313: here cite (Figure 4f, g)
Response 7. Corrected.
Point 8. Line 358: Table 6, please change it a bit, because the readers could not distinguish which ones belong to “Fresh urtite” and which ones belong to “ Altered urtite”.
Response 8. Table 6 has been changed.
Point 9. Line 378: please add more explaination about Figure. 8b, I feel confused about this figure.
Response 9. We removed Figure 8b because it did not contain essential information needed to represent this study.
Reviewer 2 Report
Dear the editor, I went through the manuscript titled "Alteration of feldspathoids changes pH of late-magmatic fluids: a case study from the Lovozero peralkaline massif, Russia," written by Julia A. Mikhailova and others. The manuscript provided petrographic descriptions of the altered peralkaline igneous rocks collected from the Lovozero massif in Russia. The petrographic observations revealed the relationship between pre- and post-alteration minerals, i.e. those including primary natrolite and sodalite and those including secondary natrolite and hydro-Al-oxide. The petrographic description includes SEM-EDS and Raman analyses, thus provide a precise discriminations of the Na-Al-silicates. In contrast, the discussion sections seems too much speculative. To discuss about the mass-influx/outflux, they construct an isocon diagram comparing fresh and altered urtite samples (Fig. 8), however, the isocon analysis was performed based on an incorrect assumption. Although the authors stated the meaning of the slope of an isocon (line 366-), it seems that the authors sought the elements that occur around the line of y=x (slope = 1). The reason I thought so is that the authors did not show any rationale for choosing "immobile elements." Based on the assumption above, the authors recognized Al, Si, Na, K, and P are immobile, however, the alteration reactions described later should indicate that Na is released into fluid phase. Although there are some possibilities that Na is fixed in some alteration products, they should consider about this contradiction. They should define isocon by more proper reasons, otherwise they cannot discuss about mass-flux of the alteration reactions. Discussion about the alteration reactions are further speculative. The conclusion of the manuscript is designed completely following the study of Markl and Baumgartner (2002 Contrib. Min. Pet.) [9] without sufficient evidence. The authors' observations showed Al-hydro-oxide (nordstrandite and beohmite) as alteration products, which could not be explained by the generally-recognized zeolite-formation reactions of (1)-(3) (lines 59-61). Na-releasing reactions (4)-(7) can be candidates for Al-hydro-oxide and zeolite forming reactions. However, it seems that discussion about how it is adequate is insufficient. Modal analysis of nepheline and nortdtrandite (Fig. 7) and its correlation to the reaction (5) (Fig. 9a) is a good dataset, although it is unclear that the authors want to emphasize reaction (4) or (5) or others. In addition, there are several mistakes in English grammars and logics, which brings the difficulty in following the manuscript. At this stage, I recommend "reject" for this manuscript rather than "major revision" as it requires reconstruction and rewriting. Nov. 5Author Response
We appreciate the time and effort that the reviewer has dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewer for their insightful comments on our paper.
Point 1. The petrographic observations revealed the relationship between pre- and post-alteration minerals, i.e. those including primary natrolite and sodalite and those including secondary natrolite and hydro-Al-oxide.
Response 1. In this article, we do not discuss the relationship between (quote) “primary natrolite and sodalite and secondary natrolite and hydro-Al-oxide”. In this article, we present the results of studies of alteration products of rock-forming nepheline and sodalite from various lithologies of the Lovozero massif. We found that nepheline and sodalite are intensively replaced by an association of secondary minerals, namely natrolite, paranatrolite, nordstrandite, and böhmite. Below are some quotes from the article that support the above.
Lines 13-14: We have studied the products of alteration of nepheline and sodalite by microtextural, microprobe, and spectroscopic methods.
Lines 60-62: We have studied the products of alteration of nepheline and sodalite from various lithologies of the Lovozero massif by microtextural, microprobe, and spectroscopic methods.
The petrographic description includes SEM-EDS and Raman analyses, thus provide a precise discriminations of the Na-Al-silicates. In contrast, the discussion sections seems too much speculative.
Point 2. To discuss about the mass-influx/outflux, they construct an isocon diagram comparing fresh and altered urtite samples (Fig. 8), however, the isocon analysis was performed based on an incorrect assumption. Although the authors stated the meaning of the slope of an isocon (line 366-), it seems that the authors sought the elements that occur around the line of y=x (slope = 1). The reason I thought so is that the authors did not show any rationale for choosing "immobile elements."
Response 2. We are very grateful for this important comment. Indeed, in the text of the manuscript, the description of the method of constructing of the isocon diagram was not clearly presented. We have now completely rewritten this section. In constructing the isocon diagram, we were guided by the works of Grant (Grant, 1986, 2005), Mori and co-authors (Mori et al., 2003) as well as Baumgartner and Olsen (Baumgartner & Olsen, 1995).
According to Grant (Grant, 2005), (quote) «equation for composition–volume relations in metasomatic alteration was rewritten as CiA = MO/MA(CiO + ΔCi), where Ci is the concentration of species “i”, “O” refers to the original rock and “A” to the altered rock, MO and MA are equivalent masses before and after alteration. ΔCi is the change in concentration of species “i”. For each species there is an equation of this form in which MO/MA is constant. If one can identify immobile species, for which ΔCi=0, MO/MA can be obtained by solving the set of simultaneous equations of the form CiA = (MO/MA)CiO. This may be done graphically by plotting the analytical data against, in which case the immobile species define a straight line through the origin. This is the isocon, whose equation is CA = (MO/MA)CO. The slope of the isocon yields the overall change in mass relative to MO.
This slope may be determined from: (a) the clustering of CiA/CiO data, (b) a best fit of data forming a linear array through the origin on an isocon diagram (the graphical equivalent of the first method), (c) the a priori assumption that certain components were immobile, (d) the assumption of constant mass during alteration, or (e) the assumption of constant volume during alteration. »
When constructing the isocon diagram shown in Fig. 8, we determined the slope from a best fit of data forming a linear array through the origin. In order to establish the best fit line, we used the Statistica 12 program. Using the data shown in Table 6, we construct a scatterplot comparing the concentrations of components in the chemical composition of fresh urtite (average of three chemical analyses) and altered urtite (average of four chemical analyses). Line of best fit is y=1.0031*x. We found it possible to reduce 1.003 to 1.00. Thus, the equation of the line of best fit has the following form: y=x.
Point 3. Based on the assumption above, the authors recognized Al, Si, Na, K, and P are immobile, however, the alteration reactions described later should indicate that Na is released into fluid phase. Although there are some possibilities that Na is fixed in some alteration products, they should consider about this contradiction.
Response 3. We are very grateful for this important comment. Indeed, according to the proposed reactions, sodium passes into the fluid. However, this fluid is not removed from the rock and hyperagpaitic minerals crystallize in close proximity to pseudomorphized nepheline or sodalite. This is written in the manuscript on the lines 21-22, 497-500:
Lines 21-22: «An increase in pH stabilizes hyperagpaitic minerals (e.g., ussingite, villiaumite, thermonatrite, trona), which can crystallize in close proximity to pseudomorphized nepheline and sodalite».
Lines 497-500: «The fluid can remain in the rock, then hyperagpaitic minerals crystallize in the immediate vicinity of the destroyed nepheline. It is for this reason that sodium loss is not observed when comparing the compositions of fresh and altered urtite using the isocon method (Figure 8a)».
To construct the isocon, the chemical compositions of the rocks obtained by the wet chemistry method were used. In order to carry out chemical analysis by wet chemistry method, the rock sample must first be crushed. For crushing, we took samples of urtite about 10 cm in diameter. Considering that hyperagpaitic minerals crystallize in close proximity to pseudomorphized nepheline and sodalite, these hyperagpaitic minerals were located in samples that were crushed. Thus, despite the fact that NaOH pass into the fluid, it is not removed from the rock.
They should define isocon by more proper reasons, otherwise they cannot discuss about mass-flux of the alteration reactions.
Discussion about the alteration reactions are further speculative.
Point 4. The conclusion of the manuscript is designed completely following the study of Markl and Baumgartner (2002 Contrib. Min. Pet.) [9] without sufficient evidence.
Response 4. The conclusions of the manuscript are based on our petrographic, mineralogical and spectroscopic studies. As the reviewer rightly noticed above (quote), “The petrographic description includes SEM-EDS and Raman analyses, thus provide a precise discriminations of the Na-Al-silicates”. The results of these studies are given in the lines 160-376.
The authors' observations showed Al-hydro-oxide (nordstrandite and beohmite) as alteration products, which could not be explained by the generally-recognized zeolite-formation reactions of (1)-(3) (lines 59-61).
Na-releasing reactions (4)-(7) can be candidates for Al-hydro-oxide and zeolite forming reactions.
Point 5. However, it seems that discussion about how it is adequate is insufficient.
Response 5. For a discussion regarding the adequacy of response (4) see Markl and Baumgartner (2002 Contrib. Min. Pet.) [9]. In our article, we only discuss reactions (5), (6), (7). Unfortunately, the review does not indicate what should be considered sufficient discussion. Therefore, we rewrote the discussion and changed the sequence of presentation of the results.
Point 6. Modal analysis of nepheline and nortdtrandite (Fig. 7) and its correlation to the reaction (5) (Fig. 9a) is a good dataset, although it is unclear that the authors want to emphasize reaction (4) or (5) or others.
Response 6. Figure 7 shows the modal analysis of natrolite, nordstrandite and böhmite, but not the modal analysis of nepheline and nortdtrandite. Therefore, unfortunately, it is absolutely not clear what exactly the reviewer means.
In addition, in the article we do not discuss the adequacy of reaction (4), nor do we provide data confirming this particular reaction. For a discussion regarding the adequacy of response (4) see Markl and Baumgartner (2002 Contrib. Min. Pet.) [9].
Point 7. In addition, there are several mistakes in English grammars and logics, which brings the difficulty in following the manuscript.
Response 7. We would be very grateful if the reviewer would point out at least one of these several mistakes in English. The English has now been checked and corrected by two native speakers and we hope these several mistakes have been corrected as well.
At this stage, I recommend "reject" for this manuscript rather than "major revision" as it requires reconstruction and rewriting. Nov. 5
Reviewer 3 Report
Alteration of feldspathoids changes pH of late-magmatic flu-2 ids: a case study from the Lovozero peralkaline massif, Russia
This manuscript discussed the alteration of peralkaline intrusions. The alteration of nepheline generated zeolite minerals and can release Na into the fluid system and change the PH condition of the fluid. The manuscript provided clear geological background and detailed petrographic information. The results of mineral and whole-rock chemistry support the conclusion that the PH in fluid can increase by the alteration of nepheline to zeolite. The manuscript is well prepared. A few suggestions is listed in the pdf file.
Comments for author File: 
Comments.pdf
Author Response
We appreciate the time and effort that the reviewer has dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewer for their comments on our paper. We were guided by the pdf file to make corrections to the text of the article.
The attached pdf file contains answers to all the comments of the reviewer.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments on Mikhailova et al . Alteration of feldspathoids changes pH minerals-1954464
Journal: Minerals
Manuscript ID: minerals-1954464
Title: Alteration of feldspathoids changes pH of late-magmatic fluids: a case
study from the Lovozero peralkaline massif, Russia
Authors: Julia A. Mikhailova *, Yakov A. Pakhomovsky, Lyudmila M. Lyalina,
Ekaterina A. Selivanova
This manuscript describes late stage alteration mineralogy in a peralkaline pluton in the Kola peninsula, Russia.
Comments:
The presentation of the geological and mineralogical background and the data in this manuscript is very good. It is well written, well organized and has appropriate references.
The conclusions are stated with a lot of certainty – starting with the title itself. This certainty could be improved upon, by carrying out geochemical modeling along the lines of Markl and Baumgartner (2002) that would support the authors' excellent mineralogic observations. In line 80, the authors do use the word "indicate" which itself indicates(!) the authors are aware of some uncertainty and they also use "assume" in parts of the manuscript. In any case, the observations made by the authors do support the conclusions of this very interesting study.
Minor Text Comments
Line number, comment
18: delete "a"
171: Petersburg?
456: reference style
Author Response
Point 1. The presentation of the geological and mineralogical background and the data in this manuscript is very good. It is well written, well organized and has appropriate references.
Response 1. We are very grateful for the appreciation of our work. We appreciate the time and effort that the reviewer has dedicated to providing your valuable feedback on our manuscript.
Point 2. The conclusions are stated with a lot of certainty – starting with the title itself. This certainty could be improved upon, by carrying out geochemical modeling along the lines of Markl and Baumgartner (2002) that would support the authors' excellent mineralogic observations. In line 80, the authors do use the word "indicate" which itself indicates(!) the authors are aware of some uncertainty and they also use "assume" in parts of the manuscript. In any case, the observations made by the authors do support the conclusions of this very interesting study.
Response 2. Thank you very much for this comment. We believe that geochemical modeling will greatly increase the length of the article and make it difficult to read. Therefore, in the proposed article, we restrict ourselves to presenting only mineralogical and petrographic results.
Minor Text Comments
Line number, comment
Point 3. 18: delete "a"
Response 3. Deleted.
Point 4. 171: Petersburg?
Response 4. Corrected.
Point 5. 456: reference style
Response 5. Corrected.
Round 2
Reviewer 2 Report
-
Author Response
Unfortunately, the reviewer did not provide any new comments. However, we took into account all the previous comments of the reviewer and completely revised the manuscript.
