Geochemical characterisation and protolith restoration of metamorphic rocks at Lazishao graphite mine, Sichuan

Cheng, Wenqi; Yu, Haijun; Wang, Xue; Kong, Decai; Long, Bo

doi:https://doi.org/10.5194/egusphere-2023-1528

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https://doi.org/10.5194/egusphere-2023-1528

Preprints

31 Jul 2023

| 31 Jul 2023

Status: this preprint is open for discussion.

Geochemical characterisation and protolith restoration of metamorphic rocks at Lazishao graphite mine, Sichuan

Wenqi Cheng, Haijun Yu, Xue Wang, Decai Kong, and Bo Long

Abstract. This study determined the deposit characteristics and geochemical features of metamorphic rocks from the Lazishao graphite deposit in order to reconstruct the metamorphic protoliths and palaeo-sedimentary environment. The results show that the SiO₂ content of the metamorphic rocks is high (55.60 % to 77.94 %), while Na₂O is 0.22 % to 1.85 %, K₂O is 1.87 % to 3.45 %, K₂O > Na₂O, and K₂O/Na₂O + K₂O > 0.5. The fractionation degree of light rare earth elements (LREEs) is greater than that of heavy rare earth elements (HREEs), with LREE/HREE ratios of 3.09 to 8.77; La_N/Yb_N is 2.72 to 10.75, with a mean value of 9.69. The rocks have moderate negative Eu anomalies (δEu = 0.50 to 0.89, mean = 0.64). Ionic lithophile elements (e.g., Rb, Ba, and K) are relatively enriched, but Sr is relatively depleted. The graphite-bearing metamorphic rocks in the study area originated from sedimentary rocks, mainly mudstone and greywacke. The palaeo-sedimentary environment was a low-salinity terrestrial freshwater body in a cold or moderately cold climatic zone.

Received: 06 Jul 2023 – Discussion started: 31 Jul 2023

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Wenqi Cheng et al.

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RC1:
'Comment on egusphere-2023-1528', Anonymous Referee #1, 30 Aug 2023 reply
Review on the paper submitted to the Solid Earth by Wenqi Cheng, Haijun Yu, Xue Wang, Decai Kong, Bo Long "Geochemical characterisation and protolith restoration of metamorphic rocks at Lazishao graphite mine, Sichuan ".

General Comments
The manuscript presents detail petrographic description and geochemical data on major and trace elements of samples of sericite–quartz schist and two-mica–quartz schists from Lazishao graphite mine (Renhe District, Panzhihua City). The authors apply multiple discrimination diagrams to recreate the protolith of the graphite-bearing rocks, and conclude that organic-rich claystone and greywacke were deposited over a long period and then subjected to regional metamorphism during which organic carbon was recrystallized into graphite.

This English is generally good, only a few sentences need to be polished. However, I have several concerns, which are listed in the Specific Comments. Overall, the manuscript can be accepted for publication on Solid Earth, hence a medium revision is recommended.

Specific Comments
The study is related toone of the huge ore-bearing formation of the graphite deposits. Please provide more detailed discussion on the geochemistry of thegraphite-bearing rocks in the formation, based on the results, implications and conclusions of other previous studies in the same area.

The formatsof some reference need to be corrected.

Small annotation errors

Line 12, change “high” to “relatively higher”;
Line 25, change “desirable” to “remarkable”;
Line 94, change “directional” to “oriented”;
Line 97, change “interstitial between” to “interstitial to”;
Line 113, change “favourable” to “economically valuable”;
Line 122, change “Major elements compositions” to “Major element compositions”;
Line 154, change “μg/g” to “ppm”;
Line 159, “δC”, typo;
Line 217, change “apparent” to “evident”;

Table.1, please list the detection limit of each analytical method;
Tables.2-4, please note the significant digit of data;
Fig.1, the legend of Fig.1b is too small;
Fig.5, the labels are too small;
Fig.13, check the typos in labels.

Reply
Citation: https://doi.org/10.5194/egusphere-2023-1528-RC1
- CC1:
  'Reply on RC1', Haijun Yu, 26 Sep 2023 reply
  
  September 25(th), 2023
  Solid Earth
  Dear Reviewers,
  
  We are very grateful to Reviewer for reviewing the paper so carefully.We have tried our best to improve and made some changes in the manuscript. These changes will make the paper is more reasonable.
  Responds to the reviewers' comments:
  
  Reviewer #1
  Specific Comments
  1.The study is related to one of the huge ore-bearing formation of the graphite deposits. Please provide more detailed discussion on the geochemistry of thegraphite-bearing rocks in the formation, based on the results, implications and conclusions of other previous studies in the same area.
  Response：We value your feedback and suggestions , however, this is the first study of graphite deposits in this area.
  2.The formats of some reference need to be corrected.
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  
  Small annotation errors
  Line 12, change “high” to “relatively higher”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 25, change “desirable” to “remarkable”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 94, change “directional” to “oriented”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 97, change “interstitial between” to “interstitial to”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 113, change “favourable” to “economically valuable”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 122, change “Major elements compositions” to “Major element compositions”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 154, change “μg/g” to “ppm”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Line 159, “δC”, typo;
  Response：We are very sorry for our incorrect writing and it is rectified at Line.
  Line 217, change “apparent” to “evident”;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Fig.1, the legend of Fig.1b is too small;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Fig.5, the labels are too small;
  Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
  Fig.13, check the typos in labels.
  Response：We are very sorry for our incorrect writing and it is rectified at Line.
  
  Thank you for your consideration. I look forward to hearing from you.
  
  Sincerely,
  
  [Name] Haijun Yu
  [Address] 66 Xiangshulin Road, Jinjiang District, Chengdu City, Sichuan Province, China
  [Phone number] +8618109052790
  [Email address] yuhaijun0601@163.com
  
  Reply
  
  Citation: https://doi.org/10.5194/egusphere-2023-1528-CC1
  - AC1: 'Reply on CC1', Haijun Yu, 26 Sep 2023 reply
    
    September 25(th), 2023
    Solid Earth
    Dear Reviewers,
    
    We are very grateful to Reviewer for reviewing the paper so carefully.We have tried our best to improve and made some changes in the manuscript. These changes will make the paper is more reasonable.
    Responds to the reviewers' comments:
    
    Reviewer #1
    Specific Comments
    1.The study is related to one of the huge ore-bearing formation of the graphite deposits. Please provide more detailed discussion on the geochemistry of thegraphite-bearing rocks in the formation, based on the results, implications and conclusions of other previous studies in the same area.
    Response：We value your feedback and suggestions , however, this is the first study of graphite deposits in this area.
    2.The formats of some reference need to be corrected.
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    
    Small annotation errors
    Line 12, change “high” to “relatively higher”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 25, change “desirable” to “remarkable”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 94, change “directional” to “oriented”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 97, change “interstitial between” to “interstitial to”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 113, change “favourable” to “economically valuable”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 122, change “Major elements compositions” to “Major element compositions”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 154, change “μg/g” to “ppm”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Line 159, “δC”, typo;
    Response：We are very sorry for our incorrect writing and it is rectified at Line.
    Line 217, change “apparent” to “evident”;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Fig.1, the legend of Fig.1b is too small;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Fig.5, the labels are too small;
    Response：We appreciate it very much for this good suggestion, and we have done it according to your ideas.
    Fig.13, check the typos in labels.
    Response：We are very sorry for our incorrect writing and it is rectified at Line.
    
    Thank you for your consideration. I look forward to hearing from you.
    
    Sincerely,
    
    [Name] Haijun Yu
    [Address] 66 Xiangshulin Road, Jinjiang District, Chengdu City, Sichuan Province, China
    [Phone number] +8618109052790
    [Email address] yuhaijun0601@163.com
    
    Reply
    
    Citation: https://doi.org/10.5194/egusphere-2023-1528-AC1

Wenqi Cheng et al.

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Short summary

Lithogeochemical analysis shows that the metamorphic protoliths of the graphite deposit were sedimentary rocks whose lithology was dominated by carbonaceous claystone and greywacke. The palaeo-sedimentary environment was a low-salinity terrestrial freshwater body in a cold or moderately cold climatic zone. Sediments were sourced from the upper crust, and the main provenance components were argillaceous rock and sandstone from a felsic–intermediate source area.


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