Amphibole Group Minerals in the Ozren Massif Ophiolites of Bosnia and Herzegovina as Petrogenetic Indicators

Round 1

Reviewer 1 Report

The manuscript describes features of rock-forming amphiboles from various parts of the Ozren ophiolite association. The authors carried out comprehensive studies, including petrographic description of rocks, morphological characteristics of amphibole group minerals, their chemical composition and Raman spectra. Based on the composition of minerals and host rocks, the authors divided all amphiboles into six types. The chemical composition of studied amphiboles provided a very good correlation with analyzed Raman-spectra. The genesis of each amphibole type has been interpreted. The data presented by the authors are fairly original and can be useful for comparison with amphiboles of other ophiolites.

Key notes on the manuscript:

1) One of the main drawbacks is the lack of information about the PT conditions for the formation of various types of the amphiboles studied, though there are various geothermometers and geobarometers based on the composition of amphiboles (Anderson, Smith, 1995; Hammarstrom, Zen, 1986; Holland, Blundy, 1994; Schmidt, 1992). Except the classification diagrams used by the authors, there are important discriminatory diagrams, which should have been applied as the basis for interpretation of the minerals genesis (Czamanske and Wones, 1973; Ernst and Liu, 1998; Anderson and Smith, 1995; Changyi and Sanyuan, 1984). This leads to many other questions. In particular, how do the authors justify classifying amphiboles into “magmatic”, “late magmatic”, “percolation”, “post-magmatic alteration”, etc.?

2) The manuscript contains no sufficient information about amphiboles in the mantle section. It is known that amphiboles can be formed during the deformation-induced decomposition of orthopyroxene in peridotites and occur as lamellae (sometimes together with diopside and Cr-spinel) in the host mineral (Saveliev et al., 2017).

3) Fig. 2 should be improved. It is necessary to indicate more clearly various categories of rocks on the map and in symbols. The markings should be more readable. Some categories have letter suffixes in the legend, but they are missing on the map. This should be brought into compliance. In addition, I haven’t found sole amphibolites on the map.

4) Among the six types of amphiboles identified by the authors, type 1 and type 6 are almost the same (magnesian hornblende, pargasite). The authors should explain in the text on what basis these amphiboles were divided into different types. Is it only because they refer to different rocks? Or are there some other mineralogical and geochemical differences?

5) Fig. 4 is difficult to read (the font should be larger) and requires ordering (e.g. panel designations should be arranged uniformly).

6) Table 2 says “Amp-P21 (from percolating melt)”. Question: how can the authors prove that these amphiboles were formed specifically in result of melt percolation, and not, say, in result of deformation decomposition of Opx or their replacement in a regressive process? I haven’t found any BSE-images of amphiboles from peridotites in Fig.3.

7) The same table shows amphiboles from harzburgite, dunite and troctolite with the same interpretation. However, I have found no indication on how the troctolites were formed, i.e. did they result from crystallization of the mantle melt, cumulates, or something else?

8) The manuscript does not contain a generalized cross-section with the position of the studied samples. It is crucial to understand where exactly certain samples of different mafic rocks (troctolites, gabbros, dolerites) occur in the ophiolite section. Are they the derivatives from the single magma chamber or is it a later melt intrusion?

In general, the manuscript needs major revision, including the design of the figures, addition to the description of amphiboles from peridotites, and, most importantly, a stronger justification of the genesis of the identified types of amphiboles. To do this, it is necessary to add discrimination diagrams and data on the PT conditions of mineral formation. A figure with optical images of each type of amphiboles in thin sections must be added to the manuscript.

References

Anderson J.L., Smith D.R. 1995. The effects of temperature and fO2 on the Al-in-hornblende barometer. American Mineralogist, 80(5-6):549-559.

Changyi J, Sanyuan A (1984) On chemical characteristics of calcic amphiboles from igneous rocks and their petrogenesis significance. J Mineral Petrol 3:1–9

Czamanske G.K., Wones D.R. 1973. Oxidation during magmatic differentiation,Finnmarks Complex, Oslo Area, Norway: Part 2, the mafic silicate. Journal of Petrology, 14(3):349-380.

Ernst, W.G.; Liu, J. Experimental Phase-Equilibrium Study of Al- and Ti-contents of Calcic Amphibole in MORB—A Semiquantitative Thermobarometer. Am. Mineral. 1998, 83, 952–969.

Holland T., Blundy J. Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. Contrib. Mineral. Petrol. 1994. Vol. 116. P. 433–447.

Hammarstrom, J .M., and Zen, E-an (1986) Aluminum in hornblende: An empirical igneous geobarometer. American Mineralogist, V. 71. P. 1297–1313.

Schmidt, M.W. Amphibole composition in tonalite as a function of pressure: An experimental calibration of the AI-in-hornblende barometer. Contributions to Mineralogy and Petrology, 1992, V. 110. P. 304–310.

Saveliev D.E., Puchkov V.N., Sergeev S.N., Musabirov I.I. Deformation-induced decomposition of enstatite in mantle peridotite and its role in partial melting and chromite ore formation. Doklady Earth Sciences, 2017, Vol. 476, Part 1, pp. 1058–1061. DOI: 10.1134/S1028334X17090161

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The presented manuscript presents the results of a solid set of analysis of the mineral chemistry of amphiboles from different type of rocks collected in the Ozren ophiolite located in Bosnia and Herzegovina. The collected mineralogical data are successfully used as petrogenetic indicators and to provide more information regarding the Raman technique applied to a group of complicate minerals such as amphiboles.

The manuscript is well organized in most of its parts and, although I am not a native speaker, in my opinion English is good. For these reasons I recommend the publication of this manuscript after minor revision. Finally, considering the topic of the manuscript, may I suggest to the Authors, if accepted, to publish their paper in the following S.I. of Minerals? https://www.mdpi.com/journal/minerals/special_issues/790B3P73PB.  

Here are some specific comments that I hope will help the Authors to improve their contribution.

1) The Authors must follow the citation style requested by the journal. i.e. use the numbers and not the names of the authors.

2) Line 46 resolved?

3) Line 66 peridote?

4) Figure 1. The Authors report in this figure the names of the countries, but the borders among them are not visible. Please indicate the legend for the dotted area and the light green. What is the number (4) in the caption?

5) Line 98. Sheeted dyke complex.

6) Lines 99-100. I suggest to remove this sentence.

7) Figure 2 is very complicate and must be corrected and revised. For example, pillow basalts are not visible, as well as listwanite. Some formations are not reported in the legend. What and where are the exploring borehole? The names reported refer to cities, villages, etc. etc.? Please explain.

8) Line 111. Subjected?

9) Line 117. Amp?

10) Line 118. WDS analyses? Please specify

11) Lines 123-124. Please provide the detection limits for each analyzed elements or remove this sentence.

12) Lines 124-128. In bracket also the analyzing crystals are reported. Please write it.

13) Move lines 155-162 at the beginning of the sub chapter Methodical approach for the calculation of amphiboles. This subchapter needs a number.

14) Chapter 4.1. In this chapter the Authors must add transmitted-light optical images showing the described textures and minerals.

15) Line 296. Do not.

16) sub-chapter 5.2 I suggest to the Authors do add some information regarding the peak of OH, that is very variable in the analyzed amphibole and to verify is this related with a compositional effect.

17) Conclusion 4. According to line 28, some of the analyzed rocks are related to the presence of ‘dry’ and ‘hydrated’  percolating melts generated in an extensional subridge setting. In the conclusion is reported: The formation of Amp-bearing rocks may have been influenced by arc-type magmas and fluids. The Authors must explain this change in the geodynamic setting from an extensional ridge to a compressive zone such as subduction as typical of the arc-type magmas.

With best regards.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The data presented are sound but understandingly disappointing as regards deducing the very different physical conditions in which such a varied set of very different amphiboles crystallized because it is difficult to derive the precise P-Temps of crystallization. Clearly however, there was both magmatic and several metamorphic influences & probably very low temperature late tremolite. The paper would be improved in its usefulness if you could add any even broad information but it is accepted that little may be possible as the exact P-T ranges of many of the amphiboles described are unknown.  

There are only minor points of mis-expression listed below:

 Line 23 where is  should be either where it is if sadanagaite is only present in the dolerites OR if it also applies to the Px & Amp1 then replace it is with they are

Lines 373-476 and in text,. The references are not in the usual alphabetical style which the journal has used so unless they have changed the journal style they will need to be changed; the Editor will know.

Line 48 Insert r into Honblende

65 Delete t in commont

66 Insert ite in peridotite

67 Delete the first the and add s to layer

103 What is Lishwanite? Needs an explanation.

Fig.2 Ornament key AAA has a much smaller A than the map. 112  Delete the first s in miscroscope

117 Use amphibole not Amp until after you've given the abbreviations on lines 155-162.

169 Amphibole should be Amp

174 micro-needle without the ous.

Excellent

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors and Editor, the revised manuscript under review has been significantly improved; important additions, clarifications and corrections have been made. In my opinion, the paper can be published after some minor additions and corrections.

The main problem unsolved is classification of amphiboles. Types of amphiboles appear in the Results section already, and criteria of their classification are unclear. I found no precise indications of amphiboles belonging to one group or another in the text. This information is also incomplete in tables. For example, in Table 2 first three analyses are not referred to any type, there is no Amp6 analysis; in Table 3 the Amp5 and Amp6 compositions are missing; Table 4 shows no Amp4, the type of amphibole from the inclusions is not indicated. In the text, amphiboles are divided into six types, while subsections 4.4.1, 4.4.2 and 4.4.3 state three types. It is unclear how these classifications relate to each other. In addition, it is necessary to provide the author’s definitions of notions “secondary” and “metamorphic”. In this regard, it is unclear how amphiboles from inclusions in the Opx from harzburgites (Fig. 4g) got into the “secondary” ones, if conditions of their formation were T = 780-1000C and P = 0.64 GPa (this corresponds to the conditions of the upper mantle plagioclase peridotite facies)? Authors must answer this question in the manuscript. In general, terms “igneous”, “secondary” and “metamorphic” are interpretation, and their use in the Results section should be avoided. It is better to interpret the terms in the Discussion section, if possible.

Given the above, I suggest that the authors add a table along the following lines to the text:

In addition, there are some minor comments:

Fig. 4. I would recommend that the authors replace Fig. 4g with another one focused on amphibole grains. In its present form, the focus is on Cpx and spinel grains, which are not discussed in the text.

Fig. 5. 1) markers a, b, c and d must be placed uniformly, it is best to place them in the upper right corners of the panels; 2) labels for the axes and some inscriptions are still hard to read; they should be corrected.

Line 279-281. You write: “The group of secondary Amp3, 4 was not suitable for any Amp geothermobarometric method, because of these amphiboles' specific chemical composition that falls outside of their calibration constraints.” But the table shows data on “Amph(3)”. This should be commented on somehow, the text and table must be brought into conformity. And again, this indicates the need to provide clear criteria for classifying amphiboles.

Comments for author File: Comments.pdf

Author Response

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