Pre-Pegmatite Stage in Peralkaline Magmatic Process: Insights from Poikilitic Syenites from the Lovozero Massif, Kola Peninsula, Russia

Round 1

Reviewer 1 Report

The manuscript presents petrography, mineralogy, and the chemical composition of poikilitic syenites from the Lovozero massif (Kola Peninsula, Russia). The work is undoubtedly significant because nowadays the scientific and economic interests in pegmatite deposits are great, but processes of trace element distribution and re-distribution during their formation, are far from being fully understood. The manuscript is well written and illustrated, easy to read and follow. It is well constructed and argued. The manuscript is worth publication. 

Author Response

Thank you for your review and appreciation of our article. 

Reviewer 2 Report

The review of the article

“Pre-pegmatite” stage in peralkaline magmatic process: insights from poikilitic syenites from the Lovozero massif, Kola Peninsula, Russia

By Julia A. Mikhailova, Yakov A. Pakhomovsky , Olga F. Goychuk , Andrey O. Kalashnikov , Ayya V. Bazai and  Victor N. Yakovenchuk

 

The paper is devoted to the reconstruction of the auto metasomatic processes of Lovozero massif, Kola Peninsular.

The article represents a very good and detailed investigation based on the huge amount of analytic (wet bulk rock analyses and EPMA data) material and reveals interesting methodological approaches including factor analyses and the mass–balance estimations using isocon diagrams.

It is possible to agree that there are two major processes visible on the factor diagrams Fig.9 including major leading magmatic differentiation with the enrichment in incompatible elements, TRE and volatiles and the processes of albitizations and nephelinizations.  It will be better to show such processes just in fig. 9 by the lines and the titles stage 1-2 etc.  It is also unclear where are appear the K- Li which were dissolved – are there the separate K—Li pegmatites?

What is unclear in this exploration – the range of the PT parameters (at least temperatures ) for each stage and something about oxygen fugacity. It was postulated that the processes took place at reduced conditions but there are a lot of ilmenites and magnetites at least at the late stages.

The authors give the formulas of many rare minerals haw they were obtained, by EPMA? It seems by electron microscope by semi-quantitative method. It will be interesting to have

In the diagrams for pyroxenes and amphiboles it will e good to show the fields of each variety according to nomenclatures.

It will be interesting to see the analogic processes from the other similar massifs worldwide

There are many localities in South Greenland (Schönenberger et al., 2006), Sweeden, Finland, South Africa, China. There are brief references in the introduction but nothing in comparison in the discussion which may be extended.  The list of references is not very high I should say.

The illustrations are good but some photos of pegmatites and the minerals in nature will be wishable.

The article should be published but after the moderate or major revision.

It seems not necessary to repeat the figures in the major text and in the supplementary file – a huge amount of megabytes economy.

Best wishes Igor Ashchepkov

 

 

 

 

 

Author Response

The review of the article

“Pre-pegmatite” stage in peralkaline magmatic process: insights from poikilitic syenites from the Lovozero massif, Kola Peninsula, Russia

By Julia A. Mikhailova, Yakov A. Pakhomovsky , Olga F. Goychuk , Andrey O. Kalashnikov , Ayya V. Bazai and  Victor N. Yakovenchuk

 

The paper is devoted to the reconstruction of the auto metasomatic processes of Lovozero massif, Kola Peninsular.

The article represents a very good and detailed investigation based on the huge amount of analytic (wet bulk rock analyses and EPMA data) material and reveals interesting methodological approaches including factor analyses and the mass–balance estimations using isocon diagrams.

It is possible to agree that there are two major processes visible on the factor diagrams Fig.9 including major leading magmatic differentiation with the enrichment in incompatible elements, TRE and volatiles and the processes of albitizations and nephelinizations.  It will be better to show such processes just in fig. 9 by the lines and the titles stage 1-2 etc. 

Answer: We corrected Figure 9 and showed the direction of magmatic differentiation with arrows, and showed the stages (stage 1, stage 2) of metasomatic alteration.

It is also unclear where are appear the K- Li which were dissolved – are there the separate K—Li pegmatites?

Answer: Indeed, pegmatites containing rare-metal mineralization can occur separately from poikilitic rocks. For explanation, we have added the following clarification to the lines 87-94: «In the Lovozero massif, pegmatites containing a wide variety of rare metal (Li, Be, Ti, Zr, Nb, Ta, REE) mineralization are found in two main settings. Such pegmatites are found or (1) in urtite of the Layered complex or (2) spatially associated with the rocks of the so-called poikilitic complex. Even though poikilitic rocks in the Lovozero massif are not widespread (5% of the massif volume), most of the rare metal pegmatites are confined to these rocks. Besides, pegmatites associated with rocks of the poikilitic complex are characterized by the greatest variety of lithium, beryllium, and rare-earth minerals».

What is unclear in this exploration – the range of the PT parameters (at least temperatures ) for each stage and something about oxygen fugacity. It was postulated that the processes took place at reduced conditions but there are a lot of ilmenites and magnetites at least at the late stages.

Answer: Thanks a lot for the comment. We have added an estimate of temperature, pressure and an oxygen fugacity to the Discussion. Please, see lines 782-791.

The authors give the formulas of many rare minerals haw they were obtained, by EPMA? It seems by electron microscope by semi-quantitative method.

Answer: We determined the chemical composition of feldspar, nepheline, clinopyroxenes, amphiboles, fluorapatite, titanite, ilmenite and magnetite using Cameca MS-46 electron microprobe (Cameca, Gennevilliers, France) operating in the WDS-mode at 22 kV with a beam diameter of 10 μm, beam current of 20–40 nA, and counting times of 20 s (for a peak) and 2–10 s (for background before and after the peak), with 5–10 counts for every element in each point. The analytical precision (reproducibility) of mineral analyses is 0.2–0.05 wt% (2 standard deviations) for the major element and ca. 0.01 wt% for impurities (lines 226-231). The standards used, the detection limits, and the analytical accuracy values are given in Supplementary Table S1. This method is not semi-quantitative.

The chemical composition of the rare minerals listed in Table 2 has not been determined. This is a list of minerals characteristic of pegmatites spatially related to poikilitic rocks according to the data of Pekov (Pekov, I.V. Lovozero Massif: History of Investigations, Pegmatites, Minerals; Ocean Pictures Ltd.: Moscow, Russia, 2001) and Semenov (Semenov, E.I. Mineralogy of the Lovozero alkaline massif; Nauka: Moscow, Russia, 1972). Mineral formulas are given in accordance with the IMA list.

 It will be interesting to have

In the diagrams for pyroxenes and amphiboles it will e good to show the fields of each variety according to nomenclatures.

Answer: Fields corresponding to rock variety have been added. Please, see figures 11 and 12.

It will be interesting to see the analogic processes from the other similar massifs worldwide. There are many localities in South Greenland (Schönenberger et al., 2006), Sweeden, Finland, South Africa, China. There are brief references in the introduction but nothing in comparison in the discussion which may be extended.  The list of references is not very high I should say.

Answer: Thanks a lot for the comment. We have added a description of similar rocks from other alkaline massifs in the world to the Introduction (lines 111-125) and a comparison of poikilitic rocks from different massifs to the Discussion (lines 801-823).

The illustrations are good but some photos of pegmatites and the minerals in nature will be wishable.

Answer: Figure 2 we supplemented with photo of pegmatite (Figure 2b) and some minerals (epididymite, eudialyte) characteristic of pegmatites spatially related to poikilitic rocks.

The article should be published but after the moderate or major revision.

It seems not necessary to repeat the figures in the major text and in the supplementary file – a huge amount of megabytes economy.

Best wishes Igor Ashchepkov

 

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors and editors,  the paper is interesting and mostly well written. The review is a bit long, but those are minor comments on clarity and should be easy to address. Good luck!

General comments:

1. There is an excessive use of quotes (lines 31, 60, 66, 67, 69, 72, 74, 75, 78, etc.) These aren't required. Either use words of phrases that do not require the quotes, or just drop them while keeping the same wording.

2. The metasomatism you are suggesting includes addition of Na (and other elements) and removal of K (and other elements). I understand where the Na is coming from - from the residual melt or fluid. But where did the elements that were removed ended up? What is the sink for K, and related elements?

2. I am not qualified to review the topic of factor analysis. I did not review this part.

Specific comments:

line 19: What exactly do you mean by "critical phenomena"? Do you mean phase separation? Do you mean convergence of liquid and vapour phases?

line 31-32: Your use of "simple" refer to grain size, and "complex" refer to chemical composition. Revise so the concept of complexity in your rocks is consistent with simplicity.

line 34: "unusual" isn't the best word to use here.

line 48: How is this "obviously"? You just said that you have pegmatites in all rocks, and in the next sentence you say it depends on the composition. But it isn't? You get pegmatites regardless of composition?

line 50: Which peralkaline melts? Your own peralkaline melts in Lovozero? All peralkaline melts in the whole world?

line 51: The low fO2 is the result of extreme fractionation, and enrichment sodium. It's only achieved in very late stages of magmatic differentiation. It's an outcome, not a cause. See https://doi.org/10.1093/petrology/egz046 for details. It's available here: https://groups.io/g/PerpleX/attachment/2564/0/egz046-final.pdf

line 52: You write as if the strong enrichment is the result of low fO2 (not accurate, see previous comment), and having mafic parental melts, which is also not accurate. Most melts have mafic parental melts, but only few result in pegmatites.

line 58: What do you mean by "magmatic melt-solution"? Is it a coexisting immisicble assemblage of silicate melt and aqueous brine? Something else?

line 61: Unclear what "preparation" is. What is the "melt-solution" (what is it? see previous comment) being "prepared" for? I can guess, but this should be clear in the paper.

line 65: Link to the full page: https://www.mindat.org/loc-2697.html

line 67: I agree with your point here, but you are writing this as if it is clear to everyone reading the paper what the true melt and hydrothermal solutions are, and that may not be the case. I already said in my previous comments that it's not fully clear.

line 74: Maybe rephrase as: "For example, 58 minerals were found in the “Yubileinaya” pegmatite, which is the type locality for 13 of them."?

line 75: What is "no. 47"? Number of minerals? Name of the pegmatite?

line 80: "...and, in fact, are a sign, by which..." - simplify this please.

line 97: I think that your "k" in "km" is the Cyrillic к, not the English k.

line 98: "...was emplaced at 360..." - Add the "at"

fig 1: You mispelled "fine". Add coordinates please. What are (D) and (AR) in the legend? What does "inequigrained" mean?

line 108: What do you mean by "ideal"? Do you mean "typical"?

line 110: What rock type is the pegmatite?

line 115: This part should come much earlier in the paper.

line 125: Area, not volume, right?

line 126: Put the unit (m) directly next to the number (800).

line 146: What is "inequigrained"?

fig 3: You mispelled "fine". And I think if the sampling points are in yellow (instead of red) they will be easier to see.

line 231: Resorbed? Do you mean replaced?

line 234: I don't understand how fine-grained nepheline leads to large crystals? Shouldn't this be small crystals?

line 260,272: "orthoclasization"?

line 388: Switch places of superscript "2-" and subscript "3": CO₃²⁻

line 406: You can only "establish" presence of lithium by directly measuring it (using LAICPMS for example). Your data raise the possibility that lithium exists in amphibole, but does not prove it.

line 448,456: Add a space between Ce, La, Mn and pfu.

line 485: What facts? This is a statement for the conclusions, not the discussion.

line 558: "spent" is not the best word to use here.

line 656: As above - define "critical events".

line 657: When you say "separate" do you mean as phase separation and immiscibility, or separation and migration of the solution externally to the crystallising rock?

line 688: Typo in "lujavrite"

line 713: Can you add a figure to this section, some kind of drawing or cartoon sketch showing the process that you envision for these rocks?

Author Response

(Reviewer 3)

Dear authors and editors, the paper is interesting and mostly well written. The review is a bit long, but those are minor comments on clarity and should be easy to address. Good luck!

General comments:

1. There is an excessive use of quotes (lines 31, 60, 66, 67, 69, 72, 74, 75, 78, etc.) These aren't required. Either use words of phrases that do not require the quotes, or just drop them while keeping the same wording.

Answer: The quotes have been removed everywhere, except for the quotation from the article of Preston (lines 722-723) and the quotation from the book of Khomyakov (747-749)

2. The metasomatism you are suggesting includes addition of Na (and other elements) and removal of K (and other elements). I understand where the Na is coming from - from the residual melt or fluid. But where did the elements that were removed ended up? What is the sink for K, and related elements?

Answer: Potassium, and Zr, Li, Mn, Fe, which are released during the metasomatic alteration of foyaite, are part of the minerals of pegmatites spatially associated with poikilitic rocks. We added this assumption to the Discussion (lines 772-774).

2. I am not qualified to review the topic of factor analysis. I did not review this part.

Specific comments:

line 19: What exactly do you mean by "critical phenomena"? Do you mean phase separation? Do you mean convergence of liquid and vapour phases?

Answer: We meant a gradual transition from magmatic melt to hydrothermal solution. "Critical phenomena" is not a correct expression and we have removed it. We have almost completely rewritten the introduction (lines 47-125) and hope to have explained how the gradual transition between melt and solution occurs in peralkaline systems.

line 31-32: Your use of "simple" refer to grain size, and "complex" refer to chemical composition. Revise so the concept of complexity in your rocks is consistent with simplicity.

Answer: Thank you, we have changed this phrase (lines 31-33)

line 34: "unusual" isn't the best word to use here.

Answer: "unusual" replaced by "trace" (line 34)

line 48: How is this "obviously"? You just said that you have pegmatites in all rocks, and in the next sentence you say it depends on the composition. But it isn't? You get pegmatites regardless of composition?

Answer: Of course, pegmatites are found in all rocks. We meant a different composition of pegmatites. But we have completely changed this part of the introduction and removed this phrase because it was redundant and did not contain important information.

line 50: Which peralkaline melts? Your own peralkaline melts in Lovozero? All peralkaline melts in the whole world?

Answer: Thank you for your comment. It was a mistake in the construction of the phrase in English. But since we changed the Introduction significantly (rewritten from line 47 to line 125), this phrase was not corrected, but deleted.

line 51: The low fO2 is the result of extreme fractionation, and enrichment sodium. It's only achieved in very late stages of magmatic differentiation. It's an outcome, not a cause. See https://doi.org/10.1093/petrology/egz046 for details. It's available here: https://groups.io/g/PerpleX/attachment/2564/0/egz046-final.pdf

and

line 52: You write as if the strong enrichment is the result of low fO2 (not accurate, see previous comment), and having mafic parental melts, which is also not accurate. Most melts have mafic parental melts, but only few result in pegmatites.

Answer: Thanks a lot for the comment. Indeed, there were big mistakes in the text and your comment helped to correct it. We have changed the introduction significantly, focusing on explaining how the gradual transition from magmatic melt to hydrothermal solution occurs.

line 58: What do you mean by "magmatic melt-solution"? Is it a coexisting immisicble assemblage of silicate melt and aqueous brine? Something else?

Answer: We have rewritten the introduction (lines 51-69) and hope to have explained term "melt-solution".

line 61: Unclear what "preparation" is. What is the "melt-solution" (what is it? see previous comment) being "prepared" for? I can guess, but this should be clear in the paper.

Answer: We have rewritten the introduction (lines 51-69) and hope to have explained term "melt-solution". The «preparation» is change in composition of melt-solution as a result of autometasomatic alterations. But we removed the word "preparation" and left only an explanation of the process (lines 73-75).

line 65: Link to the full page: https://www.mindat.org/loc-2697.html

Answer: Corrected.

line 67: I agree with your point here, but you are writing this as if it is clear to everyone reading the paper what the true melt and hydrothermal solutions are, and that may not be the case. I already said in my previous comments that it's not fully clear.

Answer: We have almost completely rewritten the introduction (lines 47-125) and hope to have explained how the gradual transition between melt and solution occurs in peralkaline systems.

line 74: Maybe rephrase as: "For example, 58 minerals were found in the “Yubileinaya” pegmatite, which is the type locality for 13 of them."?

Answer: Corrected. Please, see lines 83-84.

line 75: What is "no. 47"? Number of minerals? Name of the pegmatite?

Answer: This is the pegmatite number in accordance with Semenov's (Reference: Semenov, E.I. Mineralogy of the Lovozero alkaline massif; Nauka: Moscow, Russia, 1972) numbering.  An explanation has been added to the text (line 85).

line 80: "...and, in fact, are a sign, by which..." - simplify this please.

Answer: Corrected. Please, see lines 95-97.

line 97: I think that your "k" in "km" is the Cyrillic к, not the English k.

Answer: Corrected.

line 98: "...was emplaced at 360..." - Add the "at"

Answer: Corrected.

fig 1: You mispelled "fine". Corrected. Add coordinates please. Added. What are (D) and (AR) in the legend? Explanations have been added to the legend. Please, see fig. 1. What does "inequigrained" mean?

The term "inequigrained" is used very rarely and only in articles that have been translated from Russian into English. Therefore, we have replaced the term "inequigrained" with "uneven-grained". There are additional explanations in the lines 180-181.

line 108: What do you mean by "ideal"? Do you mean "typical"?

Answer: "Ideal rhythm" means containing all varieties of breeds, i.e. lujavrite, foyaite, urtite.  Such ideal rhythms are typical for the upper zone of the Layered complex. The middle part of this complex consists of lujavrite with foyaite lenses, and the lower part consists of lujavrite–foyaite rhythms with urtite lenses. We replaced the word “ideal” with “idealized” as in the articles by Arzamastsev and colleagues (Arzamastsev, A.A., 1994. Unique Paleozoic Intrusions of the Kola Peninsula. Geological Institute of the Kola Science Centre, Apatity. 79 pp.) and Féménias and colleagues (Féménias, O.; Coussaert, N.; Brassinnes, S.; Demaiffe, D. Emplacement Processes and Cooling History of Layered Cyclic Unit II-7 from the Lovozero Alkaline Massif (Kola Peninsula, Russia). Lithos 2005, 83, 371–393).

line 110: What rock type is the pegmatite?

Answer: The following text has been added: “Pegmatites are associated with urtite. They form lenses at the contacts of rhythms, while the underlying lujavrite is almost completely unchanged, and the overlying urtite contain numerous apophyses of pegmatite” (line 146-148)

line 115: This part should come much earlier in the paper.

Answer: The text has been moved. Now these are lines 140-144.

line 125: Area, not volume, right?

Answer: According to Gerasimovsky, V.I.; Volkov, V. P.; Kogarko, L.N.; Polyakov, A.I.; Saprykina, T.V.; Balashov, Y.A. Geochemistry of the Lovozero Alkaline Massif; Nauka: Moscow, Russia, 1966. is the volume. A reference has been added (line 158).

line 126: Put the unit (m) directly next to the number (800).

Answer: Corrected.

line 146: What is "inequigrained"?

Answer: The term "inequigrained" is used very rarely and only in articles that have been translated from Russian into English. Therefore, we have replaced the term "inequigrained" with "uneven-grained". There are additional explanations in the lines 180-181.

fig 3: You mispelled "fine". And I think if the sampling points are in yellow (instead of red) they will be easier to see.

Answer: Thank you, the sampling points are visible much better. Corrected.

line 231: Resorbed? Do you mean replaced?

Answer: Yes, it means replaced. This replacement took place in accordance with the possible reaction:

KAlSi₃O₈ + Na⁺ → NaAlSi₃O₈ + K⁺;

microcline                  albite

line 234: I don't understand how fine-grained nepheline leads to large crystals? Shouldn't this be small crystals?

Answer: We assume that large crystals of nepheline are formed as a result of recrystallization (or coarsening) of small grains of nepheline. During coarsening small crystals dissolve and large crystals grow simultaneously. This assumption is based on the works of Higgins:

• Higgins M. D. Quantitative textural measurements in igneous and metamorphic petrology. – Cambridge university press, 2006;
• Higgins, M. D. (1998). Origin of anorthosite by textural coarsening: Quantitative measurements of a natural sequence of textural development. Journal of Petrology, 39, 1307–25).

According to Higgins (2006, Section 3.2.4), at the surface of a crystal there are unsatisfied bonds which have a greater energy than those within the crystal: this excess energy is minimised as the rock texture equilibrates. Although complete equilibrium is never reached the texture will tend towards a population of ever larger crystals. Crystal populations produced by kinetic processes are far from equilibrium as they contain crystals with a wide range of sizes: smaller crystals will have a higher surface area and hence energy per unit volume than larger crystals.

We changed the text and added a reference “Higgins M. D. Quantitative textural measurements in igneous and metamorphic petrology. – Cambridge university press, 2006” (line 280)

line 260,272: "orthoclasization"?

Answer: Corrected.

line 388: Switch places of superscript "2-" and subscript "3": CO₃²⁻

Answer: Corrected.

line 406: You can only "establish" presence of lithium by directly measuring it (using LAICPMS for example). Your data raise the possibility that lithium exists in amphibole, but does not prove it.

Answer: We have carried out direct measurements of lithium in order to prove its presence. A description of the procedure has been added to the Materials and Methods section, and the lithium content has been added to Supplementary Table S6.

line 448,456: Add a space between Ce, La, Mn and pfu.

Answer: Added.

line 485: What facts? This is a statement for the conclusions, not the discussion.

Answer: Thank you for your comment. We have transferred this statement to the Сonclusions (lines 825-828).

line 558: "spent" is not the best word to use here.

Answer: "spent" was replaced by "used"

line 656: As above - define "critical events".

Answer: We meant a gradual transition from magmatic melt to hydrothermal solution. "Critical events" is not a correct expression and we have removed it. We have almost completely rewritten the introduction (lines 47-125) and hope to have explained how the gradual transition between melt and solution occurs in peralkaline systems.

line 657: When you say "separate" do you mean as phase separation and immiscibility, or separation and migration of the solution externally to the crystallising rock?

Answer: We meant separation and migration of the solution externally to the crystallising rock. We've added a little clarification to the text (lines 720-721).

line 688: Typo in "lujavrite"

Answer: Corrected.

line 713: Can you add a figure to this section, some kind of drawing or cartoon sketch showing the process that you envision for these rocks?

Answer: Yes, I can. In the new version of the article, this is Figure 17.

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors seriously modified the manuscript. The article can be accepted in the present form.

Bes wishes Igor Ashchepkov