Accessory Cr-Spinels in the Section of the Nude-Poaz Massif in the Monchegorsk (2.5 Ga) Mafic-Ultramafic Layered Complex (Kola Peninsula, Russia): Comparison with Ore-Forming Chromites
Round 1
Reviewer 1 Report
Review on the article
Accessory Cr-Spinels in the Section of the Nude-Poaz Massif in the Monchegorsk (2.5 Ga) Mafic-Ultramafic Layered Complex (Kola Peninsula, Russia): Comparison with Ore-Forming Chromites
By Tatiana Rundkvist and Pavel Pripachkin
The paper is devoted to rather interesting material – to the Cr- spinel mineralization of the Nude-Poaz Massif of the Monchetundra complex.
Despite on the interesting sample stuff it produces rather strange impression. Geology is given rather detail but mineralogy rather scarce.
- First question arisen is haw representative is this material. The amount of 39 EPMA analyses from 200 samples is not much. This is about 1 hour of common microprobe work. As it visible from the voltage 22 Kv these were high precision measurements, but why other trace elements were not analyzed. And what is strange nothing about the variations of the compositions within the same samples. They may exist. Why the major minerals in paragenetic associations were analyzed. Was electron microscope used only for photo?
- Not clear from the discussion what are the rocks of critical horizon (CH) in their origin? Are they mixed material of different magma portions as it commonly suggested for the critical horizons in Bushveld (Mcdonold et al., 2005) , Dovyren (Konnikov et al., 1995) and many other layered complexes. Or they are contaminated melt portions with the low crust or wall rocks? Or they are the last derivates that intruded at the contraction fractions. Or may be this rocks resulted from the fluid admixture from the metamorphic rocks at the surroundings. The description of Sharkov and colleagues shows that these rocks are deformed mixtured fractured and the character of sulfide veins suggest the intrusions
- The time span of rock formation in MCC is a (Kunnakkuzin et al., 2015) is rather wide 2551-2445 Where is the event referring to the CH creation?
- The PT FO2 parameters from the associations literature etc. I calculated FO2 using monomineral variant of FO2 (Taylor et al., 1998) received +2- -5 d logQMF. Did you try any modelling with Comagmat (Ariskin, Barmina, 2002)
- The role of the fluids and volatiles in chromite formation is rather high, H2O essentially expands the interval of Chr crystallization (Latypov et al., 2018). Is there correlations with the presence of Amph or Phl and chromites
- The relations between Chr? Sulfide ores and PGE are there correlations Of course better to have LA ICP analyses
- The difference in morphology of Chr1 and Chr2 means that the 1 one possibly are the grains transported by magma and 2 nd were crystallized from rapidly evolved hydrous intergranular melts (I have seen such in Ioko-Dovyren)
- The Mg’ demonstrate huge variations How they refer to the silicate minerals? For the 2nd variations means the crystallization from evolving remaining liquids in
- Language needs corrections from native speaker
- The list of references is too shot
And this is not complete list of queries
Major revision
Best wishes.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is well written and I am very happy with that. Some of my suggestions in improving the manuscript is as follows:
a) Section 2 i.e. 'Geological strucutre of the Monchegorsk Complex etc..' must to shorted to half to its present length. Otherwise, readers will loose their interest.
b) some punctuations are important, such as write 'Monche pluton' instead as 'Monchepluton' etc. The second spelling is incorrect.
c) The size of the geochemical diagrams must be little bigger, otherwise details are not clearly visible.
d) 'Discussion' part can please be shorten by 3/4 or less of its present length.
e) Please mind that you have analyzed only two samples, and hence everything will be in the strength of your present data.
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The paper represents interesting material. The authors partly improved the presentation. I’ll be But what is essential there is still nothing about thermobarometry and oxidation state. As I see from literature that it was already studied. For example, in the dissertation of Mokrushin A.V. (2005) there were estimates and some discussion. I suggest that it should be mentioned and discussed.
Best wishes.
Author Response
We are grateful to the reviewer for comments and excellent knowledge of the problem, including the geology of the Kola region.
Please see also the attachment.
Author Response File: Author Response.pdf
