Review Reports - Geology, Geochronology and Geochemistry of Weilasituo Sn-Polymetallic Deposit in Inner Mongolia, China

Round 1

Reviewer 1 Report

Review of manuscript “Geology, geochronology and geochemistry of Weilasituo Sn-polymetallic deposit in Inner Mongolia, China” by Fan Yang, Jinggui Sun, Yan Wang, Junyu Fu, Fuchao Na, Zhiyong Fan, Zhizhong Hu for Minerals (MDPI) - minerals-405571

The manuscript is well written and organized and it is easy to follow author’s ideas. They combine zircon U-Pb dating, Hf isotopic, geochemical and molybdenite Re-Os isotopic measurements with geology, ore mineralogy, petrology and whole-rock geochemistry, in order to decipher genesis of Sn-polymetallic porphyry-type deposit. The genesis of a deposit is related to the Cretaceous (at a time of transition from post-orogenic compression to extension following the subduction) large-scale orogenic movements in that part of Asia.

I have no significant objections to the manuscript. However, I am not an isotopic geologist so I am not fully qualified to evaluate some parts of the manuscript.

Description of collected data together with interpretation and discussion have potential to add on knowledge of a geology in the area. New data combined with an evaluation of so far known literature data may represent welcome contribution that deserves to be published.

Furthermore, I have some small suggestions that may be of some help for authors as specific remarks:

l. 21 mainly peraluminous

l. 24 basic or mafic instead basaltic(?)

Fig. 1B typo Sn in legend; suggest to have 1A as inset map and 1B as main map, legend not need to be marked

l. 61, 62 how can you be so precise in estimated reserves?

l 75, 76 be careful with succession of figures Fig. 1A, 1B, 1C…

l. 110 amphibole-plagioclase and biotite-plagioclase (as in Fig. 2 caption; btw is it gneiss or schist?)

Fig. 2 gneiss - in text is schist

l. 143 #200

l. 148 Please, use standard set of abbreviations (for example Kretz, or Whitney and Evans,…)

Fig. 3 here you have Q for quartz and Qz in Fig 4B

l. 170 typo Amazonite

l. 173 typo sphalerite

l. 210 Plešovice

l. 298 suggestion -> make order (succession) of diagrams to follow text Fig. 8A, 8B, 8C…

l. 326 those elements also imply subduction zone processes

l. 392 typo significance … so that one can…

l. 412-414 what are FG, OGT, I, S, A…?

Fig 10 and 11 etc. unify A and (A), B and (B)… on figures

l. 438 mineralization

l. 443 …W, Rb…

l.472 … Sn, W, ….

l. 476 … (Fig 12A).

I did not check references.

Author Response

Dear reviewer,

Thank you for the comments provided by the reviewer concerning our manuscript entitled “Geology, Geochronology and Geochemistry of Weilasituo Sn-Polymetallic Deposit in Inner Mongolia, China” (ID: Minerals-405571). Those comments have proven valuable and helpful in both revising our manuscript and guiding our research. We have studied the comments carefully and have made corresponding modifications on the manuscript. Revised parts of the text are marked in red. The main corrections and responses to the reviewers’ comments are as follows:

Point 1: l. 21 mainly peraluminous

Response 1: This phrase has been modified as suggestion by the reviewer.

Point 2 l. 24 basic or mafic instead basaltic(?)

Response 2: Basaltic has been instead of basic.

Point 3 Fig. 1B typo Sn in legend; suggest to have 1A as inset map and 1B as main map, legend not need to be marked

Response 3: The “sn-polymetallic” in legend has been modified by “Sn-polymetallic”. Fig 1A is an inset and 1B is the main map. Legend didn’t marked.

Point 4 l. 61, 62 how can you be so precise in estimated reserves?

Response 4: The estimated reserves is quoted from Wang et al. 2017.

Point 5 l 75, 76 be careful with succession of figures Fig. 1A, 1B, 1C…

Response 5: The order of Fig 1A, 1B, 1C has been adjusted.

Point 6 l. 110 amphibole-plagioclase and biotite-plagioclase (as in Fig. 2 caption; btw is it gneiss or schist?). Fig. 2 gneiss - in text is schist

Response 6: The phrase in the text “amphibole plagioclase and biotite plagioclase schist” has been modified by “amphibole-plagioclase and biotite-plagioclase gneiss”. The phrase of gneiss in Fig 2 is right.

Point 7 l. 143 #200

Response 7: 200 is preceded by a #.

Point 8 l. 148 Please, use standard set of abbreviations (for example Kretz, or Whitney and Evans,). Fig. 3 here you have Q for quartz and Qz in Fig 4B

Response 8: Qz has been used for quartz in both Fig 3 and Fig 4B.

Point 9 l. 170 typo Amazonite, 173 typo sphalerite

Response 9: The words amazonite and sphalerite have been corrected correctly, as suggested by the reviewer.

Point 10 l. 210 Plešovice

Response 10: The word Plešovice is the name of zircon standard.

Point 11 l. 298 suggestion -> make order (succession) of diagrams to follow text Fig. 8A, 8B, 8C…

Response 11: The order of Fig 8A, 8B and 8C have been adjusted.

Point 12 l. 326 those elements also imply subduction zone processes

Response 12: The sentence “those elements also imply subduction zone processes” has been added in the text as suggested by the reviewer.

Point 13 l. 392 typo significance … so that one can…

Response 13: The word significance has been corrected.

Point 14 l. 412-414 what are FG, OGT, I, S, A…?

Response 14: FG=fractionated I-type granite; OGT=unfractionated I, S and M type granite; A=A-type granite; I=I-type granite; S=S-type granite.

Point 15 Fig 10 and 11 etc. unify A and (A), B and (B)… on figures

Response 15: I have unified A and (A) in Fig 10 and Fig 11 into A.

Point 16 l. 438 mineralization, 443 …W, Rb…, 472 … Sn, W, …., 476 … (Fig 12A).

Response 16: I have corrected the errors as suggested by the reviewer.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript is potentially an important contribution to understanding of a large tin resource. The U-Pb and Re-Os geochronology are significant, although there are significant shortcomings that make this manuscript not yet ready for publication. The plan versus the cross section are not linked, which is a problem in presenting detailed geological data. The cupola of the (apo)granite/alaskite that is mineralized does not show any drill hole into it on the cross section shown, which is important information to convey. The cross section shown shows the shallowly dipping veins, but there is no obvious mechanism for the fluid flow in that system to mineralize those veins unlike most tin mineralized vein systems worldwide; it seems there maybe another cupola feeding those veins versus the cupola immediately under those veins.

With respect to this highly fractionated granite, it is not well described in relation to the petrogenesis of the cupola related mineralization or the immediately adjacent veins. The analysis of fractionation is weak relatively, with no Tzr or Tmz calculation (of T). Obviously the very low Zr & REE mean extensive low T fractionation. Also no low P calculation (Yang, 2008 Lithos) using SiO2 content. In addition the higher Nb (& Ta) & U are key as well, which has been recently prominent in the literature, i.e., Nb/Ta ratio (see GEOLOGY 2016); Although I don't find arguements about fluid fractionation vs extensive low T crystal fractionation (enhanced by higher F, Li, etc (fluxes)), these arguements are not made, but can be. Also, detailes about degree of alteration of the granitic rocks analysed was not very robust. Perphosphoric or not ?

In addition, only Hf isotopic evidence is presented for a mafic crustal or mantle origin; this is based on Lu contents in the source, which should be questioned (i.e., crust vs mantle). If a mafic origin is to be proposed more compelling Nd & Sr initial isotopic evidence is needed I think. Also, how is very selective partial melting (of protolith?) vs extensive fractional crystallization (to very low T & low P) etc responsible for the high Sn in the melt & then fluids. Eugster (1985) in Mineralogical Magazine may help.

This is a great mineralized system that should be published, but with considerable further analysis of the system in order to get the impact this paper should have.

Significant English editing is also needed.

I hope this review helps, as this manuscript has significant potential; a very interesting & significant new tin deposit as well.

Author Response

Dear reviewer,

Point 1 The plan versus the cross section are not linked, which is a problem in presenting detailed geological data. The cupola of the (apo)granite/alaskite that is mineralized does not show any drill hole into it on the cross section shown, which is important information to convey. The cross section shown shows the shallowly dipping veins, but there is no obvious mechanism for the fluid flow in that system to mineralize those veins unlike most tin mineralized vein systems worldwide; it seems there maybe another cupola feeding those veins versus the cupola immediately under those veins.

Response 1: I have added exploration line to the plan and also added drill hole into the cross section. At present, the deposit is still in the exploration stage, the overall morphology of quartz porphyry is still not controlled, and there may be hidden quartz porphyry bodies in the southeast direction.

Point 2 With respect to this highly fractionated granite, it is not well described in relation to the petrogenesis of the cupola related mineralization or the immediately adjacent veins. The analysis of fractionation is weak relatively, with no Tzr or Tmz calculation (of T). Obviously the very low Zr & REE mean extensive low T fractionation. Also no low P calculation (Yang, 2008 Lithos) using SiO2 content. In addition the higher Nb (& Ta) & U are key as well, which has been recently prominent in the literature, i.e., Nb/Ta ratio (see GEOLOGY 2016); Although I don't find arguements about fluid fractionation vs extensive low T crystal fractionation (enhanced by higher F, Li, etc (fluxes)), these arguements are not made, but can be. Also, detailes about degree of alteration of the granitic rocks analysed was not very robust. Perphosphoric or not ?

Response 2: As suggested by reviewers, I have added the description of the relationship between quartz porphyry and mineralization. The zircon-saturation temperatures (T_Zircon) of quartz porphyry range from 616° to 727°（average 678°），which is relatively low. In general, highly fractionated granitic magmas are generally high in primary temperature or high with various volatiles during the later stage. Although the T_Zircon of quartz porphyry is low, the hydrothermal fulid of Weilasituo was characterized by high-Na and high-F content, which is favorable for the differentiation of quartz porphyry. In addition, volatiles in the residual melt, such as H2O, Li, F, and Cl, tend to increase with crystallization [Zhu et al., 2002], thus promoting the differentiation of magma. The quartz porphyry analysied was unaltered. The quartz porphyry is low phosphorus.

Point 3 In addition, only Hf isotopic evidence is presented for a mafic crustal or mantle origin; this is based on Lu contents in the source, which should be questioned (i.e., crust vs mantle). If a mafic origin is to be proposed more compelling Nd & Sr initial isotopic evidence is needed I think. Also, how is very selective partial melting (of protolith?) vs extensive fractional crystallization (to very low T & low P) etc responsible for the high Sn in the melt & then fluids. Eugster (1985) in Mineralogical Magazine may help.

Response 3: The Hf isotopes and Sr-Nd isotopes show the same conclusion that the materials in the source region mainly came from the juvenile lower crust and the mixing of mantle source materials. Under the condition of low T and low P, if there is a large amount of volatile matter, it can be highly differentiated. The difference between partial melting and fractional crystallization has been determined by trace elements. It is generally agreed that Sn-W deposits are associated with granites or rhyolites derived by partial melting of continental crust (Taylor, 1979).

Author Response File: Author Response.docx

Reviewer 3 Report

The paper has good data for the region, and will certainly be of interest of regional geochronological interpretations. I have attached a PDF with editorial comments and suggestion. There are several references to peridotite replacing the magma that I think needs to be adressed as well as questions regarding figures that need to be addressed. I would also suggest expanding the conclusion a bit to include some the authors interpretations.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Point 1 how was it replaced by peridotite? how was the magma replaced by a peridotite rock? this process is still unclear.

Response 1: The above three questions are the same question about the sentence “it was intensely replaced by peridotite in the mantle”. This sentence has been modified to “it was reacted with peridotite in the mantle”.

Point 2 Does the size of the symbol represent something about the size of the deposit or volume of Sn, or? At this point in the manuscript t=does that add value for the reader? I would suggest more visible simple symbols for the locations, the three color symbols become harder to see with the granitoid colors and distribtion on the map.

Response 2: The size of the symbol represent the size of the deposit. I have changed symbols as the review suggested.

Point 3 The sketch maps don’t have coordinates, or any reference to location, without some of those details it doesn’t provide much value to the reader.

Response 3: I have added the relative position of figure 2 in figure 1.

Point 4 Just use the minimum number rather than generalizing with "dozens".

Response 4: I have used minimum number instead of dozens.

Point 5 I suggest using a color other than light blue/cyan, dark colors on a white background will be easier to view. The figure has A, B, C, D, and needs the figure caption to explain each, e.g. D has a range and average value, but no explanation...

Response 5: I have used red in the Concordia age diagram and given the explanation both Concordia ages and weighted mean ages.

Point 6 Although I appreciate the brief conclusions, they seem maybe a little too brief, without integrating some of the discussion points that that the authors suggest/conclude.

Response 6: As suggested by reviewers, I have added the conclusion.

Author Response File: Author Response.docx

Reviewer 4 Report

I have finished review the ms by Yang et al. Overall, the authors collectively utilized U-Pb geochronology and whole rock geochemistry methods to constrain timing and possible tectonic settings for a newly-discovered Sn deposit in NE China. Their data and conclusions may be helpful to better understand local and regional magmatism and their tectonic setting and genesis of hydrothermal deposits. However, there are numerous serious confusions, mistakes, and over interpretations in the paper, which make the ms less convincing and thus not suitable for publication in the journal. The most serious aspect is that the present data from this study have all been published before in several Chinese and international journals, and these is nothing new from this study as these data are entirely identical to previous published ones. Also, there are many parts in the ms that are wrongly stated, these are:

(1) the tectonic setting for the studied deposit related to subduction of the Paleo-Pacific Ocean, this is OK, however at the time of the studied ore formation there is no relevant to the Mongolia-Okhotsk Ocean;

(2) all the data in this paper have been published by previous studied, however, they did not fully compare their data to others, and what is the difference between them has not been described and discussed;

(3) the treatment of moly re-os data is wrong, in the text, they only give an isochron age and say that the common Os is higher than the 187Os, this is quite wrong as the age will be very bad quality; also in the table, they did not report the model ages for the data , making the readers hard to evaluate the quality;

(4) the writing is bad and many serious grammer errors existed, and this needs a native speaker to polish it.

Overall, though I did not fully read this ms, the above serious issues in the paper make it not suitable for publication in the journal.

Author Response

Dear reviewer,

Point 1 The tectonic setting for the studied deposit related to subduction of the Paleo-Pacific Ocean, this is OK, however at the time of the studied ore formation there is no relevant to the Mongolia-Okhotsk Ocean.

Response 1: As suggested by the reviewer, I have deleted the Mongolia-Okhotsk Ocean of the manuscript.

Point 2 All the data in this paper have been published by previous studied, however, they did not fully compare their data to others, and what is the difference between them has not been described and discussed.

Response 2: Some of the data have been published before, but the Hf isotope of zircon has not been published and I have compared the previous data.

Point 3 The treatment of moly re-os data is wrong, in the text, they only give an isochron age and say that the common Os is higher than the ¹⁸⁷Os, this is quite wrong as the age will be very bad quality; also in the table, they did not report the model ages for the data , making the readers hard to evaluate the quality

Response 3: The relative concentration of common Os is higher than that of ¹⁸⁷Os, the isochron age can be recognized as the formation time of the molybdenite, some scholars have dealt with this situation before, such as Wang et al., 2017.

Point 4 The writing is bad and many serious grammer errors existed, and this needs a native speaker to polish it.

Response 4: I have polished the manuscript through a professional polish company.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

I appreciate the changes that were made and modifications to diagrams that improved the manuscript considerably. One question that still seems unanswered is the "reacted with peridotite" (Response 1) statement. Its still not clear what this means, magma mixing? fluids from peridotite?. Rsponse 6. Conclusions are still very short, it seems that a simple bulleted list of some attention briefly describing the results of the study would expand it 2X.

Author Response

Dear reviewer,

Point 1 One question that still seems unanswered is the "reacted with peridotite" (Response 1) statement. Its still not clear what this means, magma mixing? fluids from peridotite?.

Response 1: Partial melting of delaminated lower crust formed magmas, which may have reacted with surrounding mantle peridotite during ascent.

Point 2 Conclusions are still very short, it seems that a simple bulleted list of some attention briefly describing the results of the study would expand it 2X.

Response 2: As suggested by the reviewer, I have added the conclusion.

Reviewer 4 Report

firstly I received a revised version that is not suitable for further review as the current form is not the final edited form, there is still numerous errors in the text. however, this is not the main factor that could lead to a rejection to this paper, the most significant field is that there is nothing new from this study to previously published ones, and the similar data have been published in many papers, as well as the discussions and conclusions in this ms have not been well considered. thus in the sense of science and topic, a rewriting is required.

Author Response

Dear reviewer,

Point 1 Firstly I received a revised version that is not suitable for further review as the current form is not the final edited form, there is still numerous errors in the text.

Response 1:. The editor requires that any revisions should be clearly highlighted, for example using the "Track Changes" function in Microsoft Word, so that changes are easily visible to the editors and reviewers. The errors proposed by reviewers have already been corrected.

Point 2 However, this is not the main factor that could lead to a rejection to this paper, the most significant field is that there is nothing new from this study to previously published ones, and the similar data have been published in many papers, as well as the discussions and conclusions in this ms have not been well considered. thus in the sense of science and topic, a rewriting is required.

Response 2: In the past, some geological, geochemical, metallogenic age and metallogenic mechanism studies have been carried out in order that the deposit forming process can be characterized in this deposit (Liu et al, 2014, 2016; Zhai et al., 2016; Wang et al., 2017). Previous studies on the diagenetic and ore-forming chronology of Weilasituo Sn-polymetallic deposit have done some isotopic dating. The zircon LA-ICP-MS U-Pb ages of quartz porphyry are 138±2 Ma and 135.7±0.9 Ma (Liu et al, 2016; Zhai et al., 2016 ). Molybdenite Re-Os isotopic ages are 135±11Ma and 125.7±3.8Ma (Liu et al, 2016; Zhai et al., 2016 ). Cassiterite U-Pb age of the disseminated mineralization is 138±6 Ma and the vein-like mineralization is 135±6 Ma (Wang et al., 2017). The metallogenic epoch is still controversial. At the same time, the mechanism of diagenesis and mineralization is not been well constrained.

The zircon LA-ICP-MS U-Pb ages we obtained are 138.0±1.1 Ma and 138.6±1.1 Ma, which agree with the U-Pb age of zircon of the quartz porphyry (138±2 Ma and 135.7±0.9 Ma) and the cassiterite age of the disseminated mineralization (138±6 Ma) obtained by previous studies (Liu et al, 2016; Zhai et al., 2016 ). In addition, the molybdenite Re-Os isochron age (135±7 Ma) we obtained also agrees with the molybdenite Re-Os isochron age (135±11Ma), and the cassiterite U-Pb age of the vein-like mineralization (135±6 Ma) obtained by previous studies. Taking into account previous findings, we assume a diagenetic age range of 138.0-138.6 Ma, which almost coincides with the disseminated mineralization (138±6 Ma). The vein-like mineralization took place at 135±7 Ma, which was slightly later than the disseminated mineralization. These results indicate that the diagenesis, as well as the metallogenesis, of the deposit occurred during the early Early Cretaceous.

Some scholars have studied quartz porphyry which is closely related to mineralization and consider it as highly differentiated I-type granite by crystallization differentiation (Wang et al. 2017). In this study, it is considered that quartz porphyry is highly differentiated I-type granite by partial melting and discussed how did magma differentiate at low temperature.

The Hf isotope of zircon has not been published before and combined with previous published Sr-Nd isotopes, it is believed that the magmas were sourced from the juvenile lower crust mixed with mantle.

Based on geochronological and geochemical research of the intermediate-acidic intrusive rocks exposed in the area and given the deposit geology and regional tectonics, we assumed the diagenetic and metallogenic dynamic processes.

The above makes the manuscript of scientific significance. Meanwhile, the research achievements of predecessors have been compared in the manuscript.