Fluid Inclusions and S–Pb Isotopes of the Reshui Porphyry Mo Deposit in East Kunlun, Qinghai Province, China

Round 1

Reviewer 1 Report

Overall, the manuscript is written in good quality English and I did not notice any grammatical errors.  In some places the sentences appeared a little clumsy, requiring the sentence to be read twice before the correct meaning was apparent.

I found it particularly interesting that this deposit formed during collision or post-collision evolution whereas so many other classic Mo-porphyry systems formed in rift environments.  This is a point that the authors could use to attract attention to this deposit. However, a comparison with rift-related Mo systems would add length to the manuscript and might detract from their message.  Nevertheless, it might be worth pointing out that a difference occurs.

The fluid inclusion microthermometry work has been thorough and support the author’s genetic model.  The Raman spectroscopy appeared to present data and mention that N2, CO2, and CH4 were detected but there was no follow-through with interpretation, other than suggest CH4 was deep.

I found glaring point that could have enhanced the manuscript and I suggest that the authors spend some time to address this point. There was no application of isochores to improve upon the estimate of trapping temperatures and pressures.  The bimodal fluid inclusion population in stage 2 is solid evidence for boiling and this will give the trapping temperature convincingly.  However, fracturing can cause pressures to change from lithostatic to hydrostatic and it will be worth investigating whether there was a progression over time that resulted in changes to PT conditions. Using estimated depths and isochores can provide insight and I would suggest the authors use this opportunity to enhance the manuscript. I also recommend that they be given time to investigate the use of isochores prior to returning the manuscript to the journal.

Below are items that I caught and recommend editing these minor points.

 

 

Line 47 – do the authors mean “publications” instead of “literatures”?

Line 95 – Swap “mainly comprises” and type “comprises mainly”

Line 111 – authors have already used the word “flaky” hence I suggest replacing “molybdenite is flaky and unevenly…” with “molybdenite is unevenly …”

Line 135 – I suggest changing “.. mainly molybdenite and minor chalcopyrite and pyrite” to mainly molybdenite with minor chalcopyrite and pyrite”

Line 141 – what specifically was the modification and destruction?

Line 194 – Did the CO2 homogenize to the liquid or vapor? This is critical data for density determination.

Line 226 – hyphenate “ice melting” to give “ice-melting”

Line 239 – how is the gas derived from halite or other minerals? This does not make sense.

Line 250 onwards – the authors report 0.005% analytical error but then give too many significant figures in Pb isotope values in per mil.  If value was 15.723 per mil then adjust to 15.72 per mil.  This goes for all Pb isotope analyses. Perhaps they meant 0.005 per mil instead of percent.

 

Comments for author File: Comments.pdf

Author Response

Thank you for your constructive comments and helpful suggestions that improved the manuscript.

The point-by-point response to your comments as follows:

The Reshui Mo deposit formed during collision or post-collision tectonic setting, it different from the Climax-types deposit in rift environments. And we compared their setting and added related content in manuscript.

we use the Flincor software calculated the pressure, and estimated the depths. The related connet in 6.2 chapter. The pressure and depths also indicate the CH4 was deep.

Line 47 –“publications” instead of “literatures”

Line 95 – Swap “mainly comprises” and type “comprises mainly”

Line 111 – The molybdenite generally has a flaky…

Line 135 –the ore minerals were mainly molybdenite with minor chalcopyrite and pyrite

Line 141 – I delete destruction

 

I edited the reference format.

We use the ‘’Track changes’’ function revise the manuscript in Microsoft word. Please check the attachment for details.  

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a study of molybdenite saturation is veins in a porphyry system with supporting FLINCS & stable S and radiogenic Pb isotopic evidence. The ms is well written and quite well researched.  It is very common to have CO2 as a component gas in these systems, but much less so CH4. The CH4 may have affected the proportion of H2S (relative to low SO2/SO4) in the system, but Mo(OH)6 is the dominant fluid species typically and Moly porphyries are generally oxidized. Therefore the significance of CH4 with CO2 is key. Kim et al. (2016) Can. Min. speculated on this aspect before. Also, how does CO2-CH4 enhance phase separation (with H2O) & how does boiling affect Moly-Py & Quartz deposition with hydrofracturing and geostatic pressure changes (see Drummond and Ohmoto 1985), i.e., decreases solubility by decreasing P, boiling off CO2 that increases pH etc. S isitopic aspects support the reduced gas scenerio affecting Mo(OH)6 and the proportion of reduced S (H2S dominant).

Arc-Related Porphyry Molybdenum Deposit Model by Ryan D. Taylor, Jane M. Hammarstrom, Nadine M. Piatak, and Robert R. Seal, II

https://pubs.usgs.gov/sir/2010/5070/d/

This paper is very informative as well.

Pb isotopes are not normalized to CDT, so are not o/oo (per mil).

There are small technical issues in the ms and tables & figure labelling that should be fixed. Also there are issues with ref. formatting as well. Titles of papers are not in capitals, but books are in Capitals; I highlighted some issues.

Hope this review helps.

Respectfully

 

 

Comments for author File: Comments.pdf

Author Response

Thank you for your constructive comments and helpful suggestions that improved the manuscript.

We use the Flincor software calculated the pressure, and estimated the depths. The related content in 6.2 chapter.

 

I edited the reference format.

 

We use the ‘’Track changes’’ function revised the manuscript in Microsoft word. Please check the attachment for details.  

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

A minor cosmetic edit can be made at line 130. As the word "superficial" has been removed, the "a" at the end of the line becomes "an" due to the word "oxidation" beginning in a vowel.

Author Response

Thank you for your constructive comments and helpful suggestions that improved the manuscript.

The word "superficial" has been removed at line 130. This sentence edited that “The development of the deposit can be divided into the hydrothermal ore-forming period and a surficial oxidation period on the basis of the paragenetic mineral associations and vein-body relationships’’.

 

 

 

Reviewer 2 Report

There are still some issues with the manuscript in that the actually mechanisms for saturation of sulfides, in particular molybdenite, are not stated clearly enough. I suggest Drummond and Ohmoto (1985) and other Mo complexing studies [Mo(OH)6] (& like species) to enhance these aspects of the manuscript. Kim et al. (2016) in Canadian Mineralogist suggests some of these effects & effervescence better I think.

Comments for author File: Comments.pdf

Author Response

Thank you for your constructive comments and helpful suggestions that improved the manuscript.

According to Drummond and Ohmoto (1985) study, we edited the molybdenite mechanisms for saturation of sulfides in manuscript.

We use the ‘’Track changes’’ function revise the manuscript in Microsoft word. Please check the attachment for details. 

Round 3

Reviewer 2 Report

I accidently reedited v 2.

Please use those new suggestions I put on version 2 - but you also missed stuff from my version 2, including some mechanisms for molybdenite saturation. CH4 from the mantle is just not going to be acceptable & CH4-CO2 effervescence (boiling) is not explored enough as to its relation to molybdenite saturation. I had suggested a reference Kim et al. from Can Min (2016) to help with that.

Comments for author File: Comments.pdf

Author Response

Thank you for your constructive comments and helpful suggestions that improved the manuscript.

 

According to Kim et al.（2016) , we edited the Reshui deposit molybdenite mechanisms, the details please check the section 6.2  in manuscript . 

Also we edited the third conclusion about the molybdenite mechanisms “Fluid boiling changed the pH in stage 2 and temperature and pressure to drop sharply in stage 3 created favorable environments for the fundamental depositional mechanism, leading to the precipitation of molybdenum.  ”

 

We use the ‘’Track changes’’ function revise the manuscript in Microsoft word. Please check the attachment for details.  

 

Author Response File: Author Response.pdf