Stealth Metasomatism in Granulites from Ivrea (NW Italy): Hydration of the (Variscan) Lower Crust by Melt Flow

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study seeks to understand chemical and rheological variations in the lower crust of the Ivrea-Verbano Zone that could be relevant for geodynamic implication. The study combines field, macro, micro and chemical (major and trace-element mineral composition) data for this purpose. Such a study is welcomed as there are few places in the world where the lower crust can be observed and studied in situ. The Kohistan-Ladakh, Talkeetna and Gangdese arc crust sections represent the other main examples of well preserved lower crust.

This contribution should be accepted for publication are the implementation of moderate revisions. I have some significant concerns about the grammar in and the clarity of this manuscript. The text in general needs to be more coherent, concise and clear to the point. Addressing these concerns will make this contribution better and more readable. It is a shame that there are no whole-rock major and trace element geochemical data available as these data would shed significant light on the geodynamic setting of the IVZ.

I have provided line-by-line comments on the text below.

Line 20 - relatively few, deformation-assisted channels

Line 31 - Wilson Cycle (e.g., continental drifting is still poorly

Line 33 - Perhaps replaced "relevant" with "associated".

Lines 34-35 - consequences for the distribution of stress fields, but also for the genesis

Line 35 - Nevertheless, evidence for melt-rock

Line 40 - IVZ in northern Italy (Figure 1) is a 

Line 42 - What you mean by 'almost integrated'? You have to make sure that the text in the manuscript is coherent and clear.

Lines 43-44 - infiltrated a Variscan lower crust during Permian

Lines 44-45 - evidence of

Line 46 - Which unit? Do you mean the IVZ? Please be more clear.

Line 47 - concentrated

Line 55 - a combination

Line 59 - strip

Line 70 - the Insubric

Line 72 - named the

Line 73 - into three

Line 82 - been shown to

Lines 86-87 - Perhaps move 'respectively' to the end of the sentence.

Lines 89-92 - Please rephrase this sentence to make it more clearer.

Line 94 - event as the

Line 96 - for this hypothesis

Line 97 - progressive consumption of amphibole to

Line 100 - amphibole-facies metamorphism

Line 101 - granulite-facies metamorphism

Line 102 - was considered to be responsible

Line 106 - synchronous with

Line 107 - to have overprinted the

Line 115 - due to crustal

Line 118 - amphibole gabbros

Line 122 - 1-2 km-wide

Line 127 - during the early Permian

Line 128 - Moreover, SHRIMP

Line 140 - evidence suggest that the mantle peridotites have an igneous contact with the igneous rocks of the Mafic 

Lines 144-177 - Any abbreviations used should be written out in full when first used  followed by the abbreviation in parentheses.  Please rephrase some of the sentences in the Methods (e.g., Lines 153-155). It would be great if some whole-rock major and trace element data were included in this study. Such data would shed a lot of light on the geodynamic setting of the IVZ.

Line 156 - The structural 

Line 160 - determined using a LA-ICP-MS

Lines 169-170 - as a primary standard; as a secondary standard, which

Line 171 - The data quality

Line 176 - diagrams have

Line 184 - town. These rocks cover

Line 187 - bodies that are

Line 189 - and sporadically outcrop

Line 193 - in a SW-NE direction,

Line 194 - ), the lithologies

Line 200 - The mineral abbreviations used in the text and the figures are

Line 209 onwards - I know it is stated that in Lines 200-201 that the mineral abbreviations used in the text and figures are from Whitney and Evans but it would be great if each mineral abbreviation could be written out in full followed by the mineral abbreviation in parentheses upon the first mention of each mineral.

Line 210 - amphibole gabbronorite

Line 220 - Since when is clinopyroxene grey in the field or in hand specimen?

Line 222 - di S. Lucia

Line 227 - The mineral abbreviations are after; Is it necessary to cite a paper for mineral abbreviations? Your mineral abbreviations could be included in the text and relevant figure captions after each mineral is written in full when first mentioned.

Line 231 - regardless of the grain size of these rocks

Line 233 - coarser-grained enderbites

Line 247 - compared to the enderbites outcropping 

Line 254 - Amphibole-rich

Line 257 - What is being referred to when 'they' is used here? Please be clearer.

Line 259 - 'Their'? What is being referred to here?

Line 266 - with a straight contact

Lines 274-275 - The inset shows a close up image of a quartz-feldspathic

Lines 276-277 - The grayish color of Qz is due

Line 285 - granulites, however, their contact is not visible. The stronalites exhibit

Lines 285-287 - Please rephrase this sentence so that it is more to the point.

Line 286 - structures, such as

Line 295 - of the stronalitic septa

Lines 300-301 - by the replacement; 'the mineral' - which mineral is being referred to here?

Line 304 - granulites display a medium-

Line 305 - texture that is locally polygonal, 

Line 306 - These rocks consist

Lines 314-330 - Please rewrite this figure caption so that it is more to the point and up to the standard of an international-level publication, such as Geosciences.

Line 334 - a granoblastic

Line 335 - cores whose compositions

Line 338 - cores of the porphyroclasts 

Line 342 - Please be more specific when using words such as 'they', 'their' and 'its'. You have to be absolutely clear what is being referred because parts of the text are a bit ambiguous at the moment. 

Line 349 - Ca contents; than the porphyroclastic rims

Line 350 - These Mg# values are similar to those of

Line 351 - The Al contents are (You have to use the plural of 'content' when discussing more than one Al content. Also, you have to use 'are' instead of 'is' when referring to something that is written in the plural. This applies to many other instances in the text).

Line 394 - 'the magmatic one' - what are you referring to here?

Line 413 - Ti contents

Line 416 - showing a granoblastic

Line 421 - pod

Line 467 - The clinopyroxenes (Which sample is being referred to here by the way?)

Line 471 - The amphiboles

Line 472 - with the clinopyroxenes ('the' should be used in front of the minerals being referred to in this paragraph where necessary)

Line 487 - amphibole as a geothermobarometer 

Line 488 - calculation, 1 

Line 489 - as the pegmatitic

Line 493 - between the mafic granulites and

Line 562 - the unexposed UMC

Line 567 - of the former

Line 568 - rather than being evidence of in situ

Lines 575-578 - Please rephrase this sentence.

Line 579 - contents

Line 595 - of the metasomatically-driven increase of the modal

Lines 661-662 - post-collisional basaltic magmas

Line 680 - granulites in the southern

Line 684 - IVZ, which is likely composed

Lines 707-713 - Please rephrase this paragraph so that it is more coherent.

Comment on the figures:

Whilst I think the figures are decent, it would be great if their quality and presentation could be improved where necessary. Please make sure that the axes labels in some of the plots (e.g., Figures 8-11) are spaced at the same distance from the number labels along the y and x axes.

Figures 14 and 17 - Why is there data missing in some of the diagrams in these figures?

Comments on the figure captions:

Please make sure that figure captions are written in a manner that is coherent, to the point and up to the standards of an international-level journal such as Geosciences.

Comments on the Quality of English Language

The quality of grammar and sentence structuring need to be improved. The text must be written in a more concise, clear and coherent manner. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is very well-written and the figures are all nice and appropriate to the study. Ther manuscript has a fairly large additional data base neccessary for the study.

I only have a few comments, see below.

Figure 1: The reviewer had difficulty separating the various “green” units in Figure 1. Please change the coloring or use some kind of pattern. What is the red/pink unit near the text Insubric Line?

Supp Table 1: Some of the pyroxene and plagioclase analyses have too low (less than 98.5) or too high (more than 101.5) oxide totals. Please remove or replace them.

Line 302: Beside the very nice Figure 8-11, the reviewer would consider adding the nomenclatural diagrams for plagioclase, pyroxene and amphibole.

Line 377: Did the authors have EPMA data from magnetite and spinel?

Line 486: Did you consider trying other thermobarometric methods? Maybe the Am-Pl thermometer of Blundy & Holland or Holland & Blundy or other methods will provide additional data. What is the authors’ opinion on phase equilibrium modeling? Is it possible to obtain a reliable bulk composition from these rocks considering the complex evolution (multiple generation of phases) and the presence of melting?

Line 641: ‘(‘ is missing from Figure 16)

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been sufficiently improved to warrant me to recommend that it should be accepted in its current form. I would like to suggest that in the case of Line 632, "Geodynamic meaning" should be replaced by "Geodynamic implications" during the proofing the uncorrected proofs stage.