Deciphering Iberian Variscan Orogen Magmatism Using the Anisotropy of Magnetic Susceptibility from Granites

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The objective of this paper summarizes the Anisotropy of Magnetic Susceptibility (AMS) studies that have been carried out in Portuguese Variscan granites.

This is an interesting and well-structured paper. All necessary sections (Introduction and objectives, Anisotropy of Magnetic susceptibility (AMS), Iberian Variscan belt, Variscan magmatism, AMS data integration, Understanding the magmatism of the Iberian Variscan: AMS contribution, Understanding the magmatism of the Iberian Variscan: AMS contribution, Conclusions) have been considered, while most of them are divided into subsections, providing additional details. Moreover, the provided data is valid, as well as all Figures, Diagrams and Tables, which are consistent with the detailed analysis, provided in the manuscript. The methodological part is described in detail and finally the concluding remarks highlight sufficiently the major findings of the paper.

 

Based on all above, I suggest accepting the paper in its current form.

Author Response

Please see file attached and manuscript with track changes.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

 Abstract

Line 18.

What is the meaning of decimals here? Why not round it up to an integer?

Lines 18-20

 “Mostly granites…”.  I'm not sure if the structure of this sentence is grammatically correct. Please check it out.

Line 28

“emplacementchanges” –  a space is needed

Lines 29-30

This sentence seems a little bit awkward. Could you reformulate it, please?

Introduction and objectives

Lines 52-56.

This sentence looks a little “heavy”. Could you reformulate it, please?

 Anisotropy of Magnetic susceptibility

Line 84-85

“This tensor is represented by a triaxial ellipsoid” - this is a repeating what was said two lines above

 Lines 90-92

I'm not sure that the explanation of what linearity and foliation are is perfectly correct.  Would it be worth considering the use of term “magnetic foliation plane” instead of “magnetic foliation” and “magnetic lineation axes” instead of “magnetic lineation” so as not to confuse them with the numerical parameters of AMS – foliation and lineation- as well as with phenomena foliation and lineation themselves?

Lines 100-101

“The principle of AMS is based…” - this sentence seems awkward to me.

Lines 104-106.

Could you please split this phrase into two sentences or, maybe, reformulate it?

 Line 115

What does “the direction of the plane containing the borehole” mean?

 

Figure 2f and its caption are difficult to understand

 

Lines 131-147.  AMS parameters.

What do the site's AMS parameters actually mean? Are they the average values calculated based on the parameters of the individual samples' AMS?

But what in this case K1, K2 and K3 mean? Average values calculated for all samples taken from the site? The same question for the parameter P(%).

How many samples do you collect from the site? How do you calculate the mean direction of the axes K1, K3? Why don't you talk about the confidence angle?

What does ”the matrix mean of all the samples” mean?

Why do you calculate directions “relative to Magnetic North” and not relative to true North?

 

Iberian Variscan belt

Line 149

SE or SW?

Line 150

Carbonic or Carboniferous?

 Lines 149-152

Are you sure this sentence is written in good English?

 Line 176

responsible by or responsible for?

 

Variscan magmatism

Lines 182-183

This sentence doesn't seem very clear to me.

  

AMS data integration

Line 211

Again – how many samples per site you have taken?

 

Table 1.

I believe that the methods, used to date the plutons presented in the table, should be noted.

Lines 262-263

“showing a paramagnetic behavior, being the biotite the main Fe carrier” -what does it mean? Are you saying that K values below 10^-3SI represent an unambiguous indication that 1) paramagnetic minerals are mainly responsible for magnetic susceptibility here and 2) biotite is the main mineral responsible for the measured magnetic susceptibility?  I am not sure that the K value alone can be enough for this statement.

 

 Table 2

Sorry, I can’t understand which way you calculate K, P% , K1d,  K1i,  Magnetic lineation,  K3d, K3i, Magnetic foliation  values for plutons.  The explanations provided in section 2.3 seem to me to be insufficient.

Maybe you calculate average of the sample’s values to get the every site’s mean and, then you average the sites' means to get a mean values on pluton’s level?

Although this is a very important point, it is completely unclear from your previous text.

Moreover, if you provide averages for scalar quantities and directions, why don't you provide the appropriate standard deviations and confidence angles?

Why don’t you discuss the within pluton variability of these values?  As far as I understand, it can be huge. If so, what is the point of averages? If not – I think you should demonstrate it.

I believe that this issue should be discussed.

 

 Lines 287-295

What is the level of the K value to be sure that susceptibility is due to ferromagnetic grains? What is the level of the K value to be sure that susceptibility is due solely to paramagnetic grains? Does this latter level really exist? I’m not sure. Could you explain, please?

Lines 296-298

Did you try to get IRM curves for granites that you call paramagnetic? I’m almost sure that for them you would obtain similar curves.

 

“…and magnetite was also identified…” – where? In these plutons?

 

Line 311.

“In paramagnetic granites (i.e., magnetite is absent)…” – where above you have shown that in these granites magnetite is absent?

 

Figure 6.

Indicate please in the fig.6 caption what does the dashed line show.

 

Lines 381-382

“minimum extension direction (e3) is parallel to K1”, “maximum extension (e1) will be parallel to K3” – is it right? It seems like it should be the other way around, I am not right?

 

Figure 9.

Do these color stereograms represent the distribution of the anisotropy axes of the individual samples taken from each pluton? Could you please indicate on stereograms the number of samples used to characterize each pluton?

 

Could you please specify the color code?

 

Angles’ marks on stereograms are difficult to distinguish.

 

Plutons Vieira do Minho, Serra da Estrela - nowhere above in the text I didn’t see any explanation why this kind of AMS should be interpreted as the manifestation of  the strike-slip fault.

 

Lines 407-408

Why the figure caption is placed in the middle of the figure?

 

I don’t see much difference between AMS of the Valpacos and Vieira do Minho plutons, but you suggest the different interpretation for them. Could you explain why?

 

Line 422.

Sorry, I didn’t understand: are you saying that “moderate compression” regime and strike-slip fault regime are the same?  Could you specify, please?

 

Figure 10.

What do the crossed out square and rectangles under the sign “Pure Shear” mean?

 

Again, the same request – please explain how you calculate P (%) for the entire pluton?

 

Understanding the magmatism of the Iberian Variscan: AMS contribution

Lines 491-494.

Could you split this phrase into two sentences please or reformulate it? Sorry, I have managed to find what does “binomial granite/minerlisation” mean.

 

Lines 508-510

This sentence is difficult to understand.

 

Lines 544-545

“The dominant paramagnetic behavior of the granite plutons presented in this work

reflects the presence of ilmenite as the main iron oxide and the biotite as the more

important ferromagnesian mineral.”  Where does this come from? Why do relatively low susceptibility values directly indicate this? - as can be understood from your statement.

 

Conclusions

Lines 553-554

The sentence is difficult to understand.

 

Line 568

It seems to me that it is too risky to deduce this statement only from the fact of the relatively low magnetic susceptibility of these granites.

 

Lines 581-582

The sentence is difficult to understand.

Line 588 -590

Could you please simplify this phrase?

Comments on the Quality of English Language

See comments and Suggestions for Authors above

Author Response

Please see file attached and manuscript with track changes.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This is an extensive compilation of a very large amount of anisotropy data.  Overall, this work will be a valuable contribution.  I urge the authors to be accurate and consistent in their use of stress and strain terms.  For example, a tensile stress state results in extension, a strain.  In the crust, a vertical to sub-vertical sigma 1 stress typically results in horizontal to sub-horizontal extension.  

Comments for author File: Comments.pdf

Comments on the Quality of English Language

I have made numerous comments via hand in the attached pdf.  I hope that the authors will find these of assistance!

Author Response

Please see file attached and manuscript with track changes.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear editor,

The authors have carefully considered my previous comments and have done a lot of work to improve their article. My opinion is that the manuscript is almost ready for publication in its current state, however, I would ask the authors to take into account several of my new comments, which are listed in the margins of the revised version of the manuscript. I hope this can make the data description and interpretation clearer.

No need to return the final version to me for re-reviewing.

Yours very sincerely,

Vladimir Pavlov

Comments for author File: Comments.pdf

Comments on the Quality of English Language

I believe there are a few minor corrections left to make (see my comments in the revised version).

Author Response

Please see file attached.

Author Response File: Author Response.pdf