Zircon as a Mineral Indicating the Stage of Granitoid Magmatism at Northern Chukotka, Russia
Round 1
Reviewer 1 Report
The paper "Zircon as a mineral indicating stage of granitoid magmatism at Northern Chukotka, Russia" submitted by Viktor I. Alekseev and Ivan V. Alekseev presents textural and compositional relationships of zircon from three facies of Late Cretaceous magmatism from the Chaun area, Chukotka (Russia). This topic is interesting and suitable for the journal.
However, English style is very poor and many sentences need rephrasing. Indeed, some parts of text are incomprehensible. In addition, technical terms do not fit the normal use in geological journals (see detailed comments). The work also presents deficiencies in manuscript organization, rock facies classification, and mineral compositions that are commented below (see also the annotated pdf).
Because of these deficiencies, I recommend major revisions.
Best regards
Detailed comments
1.- English
1.1- Pleae use:
trace-elements instead of microimpurities or impurity elements
texture or habit of zircon instead of anatomy of zircon
grains or crystals instead of individuals
microinclusions instead of microminerals
magmatic core instead of core of protolith
1.2.- Please, use other terms for:
non-formal or informal impurities (uncommon trace elements?)
"captive” minerals (mineral inclusions?)
1.3.- Please, explain:
1.3.a.-Hyacinth habit: in which sense do you use this term? According to the Encyclopaedia Britannica, hyacinth, also spelled jacinth, means a red, orange, or yellow variety of the gemstone zircon. Accordingly it should be more correct to use hyacinth color. Furthermore, since hyacinth is a variety of zircon expressions like " hyacinth- and zircon-like" (e.g. line 184) are unmeaninful.
1.3.b.-What do mean the terms "Cyrtolite-like appearance" and "powerful rare-metal shells of cyrtolite"? Cyrtolite is used for metamict zircon as well as for a chemical variety of zircon that contains uranium, yttrium, and other rare elements (and, hence, any old zircon containing uranium will be metamict). Then, I imagine that cyrtolite-like appearance means metamict, but what does mean "rare-metal shells of cyrtolite"? Uranium rich, metamict shells? Then, I don't understand why "powerful"
1.3.c.- zircondomatic: domatic zircon?
1.3.d.- Ontogenic criteria?
1.3.e.- gravitating?
1.3. f.- Typomorphic impurities ?
2.-Manuscript organization
Lines 41 to 106 should be in a section named Geological setting and petrography or something like this; whereas lines 107 to 137 properly represet the section on Materials and methods
3.-Rock facies
Rock facies classification presents obvious inconsistencies:
The authors distinguishs three rock facies: biotitic granites, biotitic monzogranites and zinnwaldite granites. However, since monzogranite is a type of granite, the biotitic monzogranite should belong to the biotitic granite. Therefore, other term should be used for the monzogranite facies. According to the petrographic description, the term "biotitic monzonites" will be more appropriate.
4.- Rock composition
4.1.- The references where whole-rock compositions are presented must be cited.
4.2.-The composition of MG facies must be described in a more detailed way indicating the silica range. Given the relatively high alkali contents, I have some doubts on its subalkaline character; I think a TAS diagram would be necessarily.
5.-Zircon composition
5.1-The chondrite normalized REE diagrams must be shown and the REE compositions presented in Table 1.
5.2.- I think thar emprical formulas of zircon should be deleted.
5.3.-Given that Ti zircon contents are reported, temperatures estimated with the Ti in zircon thermometer should be presented.
6.- Abstract and conclusions:
How growing complexity of crystallography and individual structure are determined?
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for Authors
This is good paper with a lot of new results, but it needs major restructuring.
Geological map and regional geology commonly is presented as Geological background, so you better to separate them, for example as “2. GEOLOGICAL SETTING”
Your Fig. 1 needs coordinates, because not everyone knows where is Chaun bay.
If you use in the text “Chaun complex”, “Ichuveen complex” and “Perkakay complex”, they must be clearly seen on your map.
Line 107-110 – your paper presents the results of a zircon study not granitoids, and since you have studied 220 zircon specimens it is a good reason to make a new Fig 2 (see below).
- MATERIALS AND METHODS
In MATERIAL I would suggest you to describe your rock samples 4063, 4105, ets. Since your BG, MG and ZG granites are rock series and phases, write which rocks were used here.
In METHODS describe only those methods which you use in this paper, not all you have used for 220 zircon samples. For example you don’t show the results of TOF mass-spectrometry in the manuscript, so don’t write about it in Methods. You may use the results of mapping in the DISCCUSION.
- RESULTS
General remark - only the obtained results should be presented here. Your interpretation of the results, for example, that the cores are xenogenic, or REE pattern (obtained earlier) corresponds to magmatic zircon should be in the DISCUSSION section.
Line 142-143 – incorrect reference 1-3, northern Chukotka zircon hardly was described in “Zircon” volume.
Fig. 2 must be improved since it is lack informative and does not correspond to the descriptions of zircon in the text. There are at least two zircon generations in each type of granites, but they are not shown, inclusions are not signed, CL images are not presented. There are inconsistencies also – line 153-154 – “metamict rim of variable thickness” is not presented at Figure 2a.
Table 1. According to Fig 2, sample 2739 is a xenogenic core, why do you use it as typical MG zircon composition?
If you will add to Fig 2 all zircon types according to you own text, add to Table 1 relevant data (on cores, rims and zircon generations).
Description of ZG zircon is impossible to understand without a good illustration, it is about Fig 2 again.
Lines 214-216 – to DISCUSSION, but I don’t understand why zircon “with the oscillatory-zonal nuclei is the product of the regeneration of zircon protolith”?
- DISSCUSSION
Here you should explain first genesis of your zircon types, why do you consider some cores or grains to be xenogenic or magmatic, rims - hydrothermal or what ever. Then it will be more understandable why the studied zircon forms a generation series, because now it is not obvious.
REFERENCES.
Number 9 – incorrect page numbers in the reference.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The paper "Zircon as a mineral indicating stage of granitoid magmatism at Northern Chukotka, Russia" submitted by Viktor I. Alekseev and Ivan V. Alekseev has been significantly improved, but there are still many sentences that need rephrasing. In the annotated pdf I present many suggestions and corrections.
Additionally, the following issues must be solved:
1) The map is confusing, numbers can indicate two different things. Please use Roman numbers for referring to the intrusions.
2) The methods must be rephrased. See comments in the annotated pdf.
3) The composition of MG facies must be described in more detail; silica range and total alkali contents must be given for each rock type forming the association (i.e. monzogabbros, monzodiorites, quartz monzonites, granosyenites and monzogranites).
4) Full representative analyses of REE in zircon and REE chondrite-normalized diagrams of zircon must be given.
The answer provided by the authors is not satisfactory. The authors indicate in their comments that "The concentrations and the REE distribution spectra are given in [Alekseev et al., 2012; Alekseev, 2014]. Corresponding references have been made."
However, in the paper from Alekseev et al. (2012), it is reported zircon compositions from biotite granites and lithium–fluorine granite of the Severny pluton. The biotite granite is significantly older (126.8 ± 8.6 Ma) than this presented in the work (89.4 ± 0.7Ma), therefore, they are not comparable. Furthermore, I don't see the labels of samples reported in Table 1 from the ms in that paper.
Regarding to the paper by Alekseev (2014) , it is not indicated where it was published. I couldn't find it in the web.
5) In section 5.1, the methods for temperature estimations must be clearly indicated. Note that zircon morphology also depends on composition, and it is not a reliable method for thermometry. What are the apparent temperatures obtained by the Ti-in-zircon thermometer?.
6) Check the format of references
Since this is a second cycle of revision, I consider that these problems must be solved in the next corrected version, otherwise the paper should be rejected.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
No comments, corrected version suits me.
Author Response
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Round 3
Reviewer 1 Report
Dear authors,
The work still presents many problems that have not been solved during revision process.
Ii is poorly organized and description and presentation of analytical data are deficient. English style remains poor; many sentences need rephrasing; some examples are given below:
"Modern methods of local chemical analysis have established that concentration of trace elements and types of mineral inclusions in the same minerals of similar rocks varies depending on their age and geological position" This expressions is quite confusing and imprecise.
"intrusions of zinnwaldite granites are formed after intrusions of quartz monzonites and monzogranites: MG → ZG". It is not necessary 《MG → ZG》, it is redundant. This sentence also presents repetitions that could be easily avoided, the authors could just indicate:"zinnwaldite granites intruded after quartz monzonites and monzogranites"
"the composition of zircon is complicated from early granitoids to late stages" This sentence is confusing. etc
The conclusions are poorly expressed or confusing. In which sense are Hf, U, Y, Th, Nb and Ti isomorphic rare? The authors should also consider that some of these elements are not trace, but minor elements in zircon.
On the other hand, now it is clearly indicated that U-Pb ages of zircon were determined in more than 50 grains (lines 113-114 ); but where are the data?; we have again the same problem as with REE. Where is the Table with the analyses? Where are the concordia diagrams? How many data are concordant? There is no description of these data.
Furthermore, I indicated in my last report that " zircon morphology also depends on composition, and it is not a reliable method for thermometry". So, zircon morphology depends not only on temperature but also on many other factors as composition and crystallization rates; see for example discussion in Benisek and Finger (1993; Factors controlling the development of prism faces in granite zircons: A microprobe study. Contrib Mineral Petrol 114:441-451). In this work, the authors concluded that:" The first major conclusion of this study is that the prism morphology of accessory granite zircons does not constitute a reliable geothermometer for granitic rocks". Accordingly, it should be deleted the sentence in lines 256-257 "zircon crystallization temperature was determined from its morphology using a diagram of J.P. Pupin", as well as any reference to temperature estimates deduced from morphology.
Afer this third round of revisions, I'm afraid that I have to propose that the work should be rejected.
Best regards
Author Response
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Author Response File: Author Response.docx
