Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry
Round 1
Reviewer 1 Report
The manuscript gathers the available information on the main deposits of bentonites in Spain, including geology, mineralogy and crystalchemistry. It will be a relevant contribution for all readers interested in these deposits. The title suggests the inclusion of new data and I expected additional information or conclusions. But it simply gathers the information available in the literature in a comprehensible way. That's why I recommend remove and "new data" from the title.
In my opinion the manuscript is well written and only minor corrections are necessary before Editor acceptance. Please, considered the following comments:
L93: You mention Aguila and Magan hills, but in table 1 there are samples only from Magan Hill. Please clarify.
L104: correct feldspart to feldspar
Table 1: Please identify sample TAM5 in table, for consistency with Figure 9.
L122-124. Did you coated samples with Au instead of C?
L190. Mg source is a recurrent topic in literature. Any suggestion for the Mg source?
L418. Try to use international references, in English, better than PhD dissertations. Delgado could be change to Cuadros et al. Clays Clay Min. 29 (1994) 297-300. There are other cases through the text.
L477: change prensent to contain?
L504: correct Caballero
L506: correct biotite
L543: Correct whit to with
L551: Change SEMECTITE TO SMECTITE
SECTION 5. The authors introduce an interesting discussion about the structural formulae of smectites, concerning the present of Mg in both octahedral and interlayer positions. That is already known. I expected any suggestion at least in the sample they analyzed. Mentioning a problem does not solve it. The most paradigmatic case is sample RESQ with an octahedral occupancy >6. I am sure all the analyses with Si>8 were discarded, but why did you not correct So>6? The discussion is interesting, but the problem remains unsolved.
Table III. AlIV in sample CarbF11 is wrong.
L624: Check the second montomrillonite
Table IV. I guess that the formulae correspond to bulk analyses as well as TEM. I think they should be differentiate. TEM-AEM corresponds to single particle analyses, but bulk may include the presence of minor amount of accompanying minerals that distort the result.
Figure 12. I suggest to use different symbols for the different deposits.
Author Response
RESPONSE TO REVIEWER 1 COMMENTS
The manuscript gathers the available information on the main deposits of bentonites in Spain, including geology, mineralogy and crystalchemistry. It will be a relevant contribution for all readers interested in these deposits. The title suggests the inclusion of new data and I expected additional information or conclusions. But it simply gathers the information available in the literature in a comprehensible way. That's why I recommend remove and "new data" from the title.
The manuscript contains new data because a group of representative samples of each deposit (Table 1) have been studied under the same procedure, by XRD, AEM HR-TEM, and geochemical analysis of major and traces elements. These new data are discussed in the framework of those are in bibliography.
In my opinion the manuscript is well written and only minor corrections are necessary before Editor acceptance. Please, considered the following comments:
L93: You mention Aguila and Magan hills, but in table 1 there are samples only from Magan Hill. Please clarify. In the new version is clarified, we refer to the area “del Águila and Magán Hills” but the samples studied, as it appears in Table I, only come from De Magán Hill.
L104: correct feldspart to feldspar Done
Table 1: Please identify sample TAM5 in table, for consistency with Figure 9. Done. Label of Figure 9 is changed because it was a mistake, it appears TAM5 instead NAV5. In the new version it is OK
L122-124. Did you coated samples with Au instead of C? It was a mistake, obviously it is C. It has been corrected.
L190. Mg source is a recurrent topic in literature. Any suggestion for the Mg source? This is an open question as it is pointed in L182-185 that refers to [74], a paper in which this question is widely discussed.
L418. Try to use international references, in English, better than PhD dissertations. Delgado could be change to Cuadros et al. Clays Clay Min. 29 (1994) 297-300. Done. Reference has been changed to Cuadros el al. 1994
L477: change present to contain? Done
L504: correct Caballero Done
L506: correct biotite Done
L543: Correct whit to with Done
L551: Change SEMECTITE TO SMECTITE Done
SECTION 5. The authors introduce an interesting discussion about the structural formulae of smectites, concerning the present of Mg in both octahedral and interlayer positions. That is already known. I expected any suggestion at least in the sample they analyzed. Mentioning a problem does not solve it. The most paradigmatic case is sample RESQ with an octahedral occupancy >6. I am sure all the analyses with Si>8 were discarded, but why did you not correct So>6? The discussion is interesting, but the problem remains unsolved. It is an interesting comment, we only point the problem because other studies are needed to solve it.
Table III. AlIV in sample CarbF11 is wrong. Done
L624: Check the second montomrillonite Done
Table IV. I guess that the formulae correspond to bulk analyses as well as TEM. I think they should be differentiate. TEM-AEM corresponds to single particle analyses, but bulk may include the presence of minor amount of accompanying minerals that distort the result. Ok, We have indicated in the Table by mean of * the analyses obtained by AEM.
Figure 12. I suggest to use different symbols for the different deposits. As pointed in the figure caption, each colour corresponds to different deposit.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The work by Garcia-Romero et al. is an extensive study on geology, mineralogy and crystal chemistry of Spanish bentonites. I selected the two latter aspects for detailed assessment, as they fit my professional expertise. In suggest minor revision, because the manner of XRD data presentation and their interpretation require improvement, and additional information is needed on the uncertainty of crystallochemical formulae.
In the mineralogical part, the Authors attempt to find relations between the mineral composition of investigated bentonites and the geological processes responsible for the formation of 3 parent deposits. Detailed comments to this part are given below:
40: bentonites are rocks, not minerals 105-124: Description of methods includes X-ray examination of oriented samples (fraction smaller than 2 µm), saturated with ethylene glycol, calcined; however, in the whole paper there is no reference to materials treated in such a way. 467-512: Section „Mineralogy and chemistry of bentonites” contains description of XRD analysis of selected bentonites. In relation to the previous comment, it is not clear what was the manner of sample preparation for XRD analysis – this should be clearly stated both in the text and in the caption to Figure 9.
The XRD patterns presented in Figure 9 are very poorly described. For instance, the reflections visible in patterns of CAR2 and LTBV samples lack any description. In the remaining diffractograms only some reflections are described. In the case of ROS sample, only Miller indices of planes 060 and 001, attributed by the Authors to a trioctahedral smectite, are given. All XRD peaks should be described.
In ROS sample, the elevated background in the range of d001 from 10 to 15 Å, interpreted by the Authors as reflecting poor order of the trioctahedral smectite, may also stem from the presence of smectite-illite mixed-layered minerals. This can be distinguished by performing XRD of sedimented samples saturated with ethylene glycol. Since the Authors appear to be familiar with the glycolation technique, the experiment should be carried out, and its result included and discussed in the revised version.
Also, lack of appropriate description of XRD reflections in Figure 9 makes the statement in l. 480 unclear.
Figure 9 contains XRD pattern of sample TAM5, not listed in Table 1.
l.551: Typo error: should be SMECTITE
Chapter "Smectite crystal-chemistry" is based on discussion of EDX point tests results. Analysis of the data in Table III shows that in many cases standard deviations are very high. In view of this the uncertainties of the calculated values of crystalochemical formulae should be given. Moreover, all abbreviations used in Table III should be explained in caption to this table (M, SD, n).
Author Response
RESPONSE TO REVIEWER 2 COMMENTS
The work by Garcia-Romero et al. is an extensive study on geology, mineralogy and crystal chemistry of Spanish bentonites. I selected the two latter aspects for detailed assessment, as they fit my professional expertise. In suggest minor revision, because the manner of XRD data presentation and their interpretation require improvement, and additional information is needed on the uncertainty of crystallochemical formulae.
In the mineralogical part, the Authors attempt to find relations between the mineral composition of investigated bentonites and the geological processes responsible for the formation of 3 parent deposits. Detailed comments to this part are given below:
40: bentonites are rocks, not minerals. Done. Changed to rocks
105-124: Description of methods includes X-ray examination of oriented samples (fraction smaller than 2 µm), saturated with ethylene glycol, calcined; however, in the whole paper there is no reference to materials treated in such a way. The mineralogical characterization was done following the routine procedures for the clay minerals study, the information on the impurities found in the samples by XRD (both from whole rock and oriented aggregate) is in Table I.
467-512: Section „Mineralogy and chemistry of bentonites” contains description of XRD analysis of selected bentonites. In relation to the previous comment, it is not clear what was the manner of sample preparation for XRD analysis – this should be clearly stated both in the text and in the caption to Figure 9. Done, In new text L461-462 and L487 in the caption of Figure 9 is now clarified.
The XRD patterns presented in Figure 9 are very poorly described. For instance, the reflections visible in patterns of CAR2 and LTBV samples lack any description. In the remaining diffractograms only some reflections are described. In the case of ROS sample, only Miller indices of planes 060 and 001, attributed by the Authors to a trioctahedral smectite, are given. All XRD peaks should be described. Done. The interpretation of all visible peaks have been done and labeled in the Figure 9
In ROS sample, the elevated background in the range of d001 from 10 to 15 Å, interpreted by the Authors as reflecting poor order of the trioctahedral smectite, may also stem from the presence of smectite-illite mixed-layered minerals. This can be distinguished by performing XRD of sedimented samples saturated with ethylene glycol. Since the Authors appear to be familiar with the glycolation technique, the experiment should be carried out, and its result included and discussed in the revised version. A new phrase (L475-477) is added in the text and new figure to clarify this is now as supplementary material.
Also, lack of appropriate description of XRD reflections in Figure 9 makes the statement in l. 480 unclear. It was a mistake in the label that now is corrected.
Figure 9 contains XRD pattern of sample TAM5, not listed in Table 1. It was a mistake in the label that now is corrected.
l.551: Typo error: should be SMECTITE . Done
Chapter "Smectite crystal-chemistry" is based on discussion of EDX point tests results. Analysis of the data in Table III shows that in many cases standard deviations are very high. In view of this the uncertainties of the calculated values of crystalochemical formulae should be given. Moreover, all abbreviations used in Table III should be explained in caption to this table (M, SD, n). All abbreviations used have been explained in the new caption of table.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article gives data on Spanish bentonites. As authors themselves also state the article is synthesis of a review of available data and some additional data collected within the scope of the current investigation.
In my opinion the presented text is generally well written, it gives adequate background, the results are appropriately presented, and the conclusions are reasonable and in accordance with results. I have several smaller suggestions which are given in the attached .pdf file.
In spite of the fact that I am not an native English speaking person I think that some changes in language and style are necessary and will improve the text.
In addition to pdf file which I uploaded into the system there is supplementary file in which I also have some suggestions. I tried to upload both but unsuccessfully therefore I will send it by e-mail.
At the end I suggest acceptance of the paper after minor modifications, which are explained in the attached file.
Comments for author File: Comments.pdf
Author Response
RESPONSE TO REVIEWER 3 COMMENTS
We would like thanks to the reviewer 3 the detailed and constructive revision made. Their suggestions have helped to improve the text. We have accepted almost all of them. In addition we have made the changes suggested by the reviewer in the figures 1 and 2. We are attaching attach new figures 1 and 2.
We indicate we indicate below the only that we do not changed:
Table I: “The order of localities is not the same as in the text, I suggest changing of order in the Table”
We do not change the order of the localities in the table because since also the orden of the descriptions in the text change. The order of the localities in the table agrees with the previous paragraphs altrhougth it doesn't agree with other parts of the work.
About the question in line 381: “why the order of groups is different from that in Figure 7”: In figure 1 are indicated the studied deposits and the numbers coincide with the order of their description in the text, while in line 381 refers to a classification made by other authors. We do not have described the deposits i the same order. It could be unified but we do not think it would be necessary.
Author Response File: Author Response.pdf
