Tracking and Evaluating the Concentrations of Natural Radioactivity According to Chemical Composition in the Precambrian and Mesozoic Granitic Rocks in the Jangsu-gun Area, Central Southwestern South Korea
Franz Neubauer
Round 1
Reviewer 1 Report
The aims of the paper are not in perfect harmony with the applied methods. Petrogenesis of an igneous-metamorphic assemblage cannot be based on geochemistry alone, without any mineralogical tests and textural observations. Because of this, the conclusions cannot be accepted as valid. However, the dataset presented is worth for interpretation, if the authors change the focus from the petrographic characterization of the rocks to the identification of geochemical factors controlling the gamma activity of the natural rocks.
Remarks on the chapters on geological settings, methods and results are given below.
Chapter "Discussion" is, in fact, not a proper discussion of the results described previously in the paper. All geochemical data are treated as original magmatic compositions, although there are metamorphic rocks with probable sedimentary protoliths and, according to the tace element patterns, even in igneous rocks there is a high probability of postmagmatic alterations. Effects of these things should be considered here. Several things come as assumptions not supported by any observations (like monazite should be the main host of Th and U), or from unreferenced sources (like topographical factors). On the other hand, there is nothing about the correlation of the radiometric properties and the chemical composition, although Figure 8 in the results chapter shows at least U and Th concentrations (but not K). Consequently, the outlier values (like measured 226Ra activity of sample JS-68 not supported by measured U concentration) are also not discussed. The data provide a possibility to test how far the stratigraphic group or other factors (like local or regional alterations with special geochemical fingerprints) determine the potential activity, but such things are not discussed - except in the abstract, which is therefore also not harmonized with the text (there is even a literature reference included in the abstract, which is not occurring elsewhere in the text). Instead of this, fractional crystallization is treated without knowing anything from the actual mineral composition of the samples. Plots like figures 10 and 12 cannot be interpreted without this. This part should be completely reconsidered and rewritten, realizing the combined interpretation of the chemical (with emphasis on the trace element geochemistry) and the radiometric test results. The word "petrogeneses" in the title should be changed to "chemical composition". The other possibility is to complete the results with mineralogical tests, e.g., heavy mineral separation and EPMA yielding data on the composition of the U-Th bearing accessories.
Rows 109-112: This information does not belong to the geology; it can be left out, or, if necessary, moved to the last paragraph of the introduction.
Rows 119-132: It is not clear if the information described here comes from the literature referred to in the previous sentences containing the age data. The appropriate sources have to be given for this part too, even if it is partly the same as before.
Row 133: The red hues cannot be distinguished in the image (maybe because of low resolution of the downloaded file). Numbers of the insert map should be enlarged, leaving the superfluous 0 minutes and seconds. There is a contradiction with the map of Figure 1: it indicates extended outcrops of "Middle Paleoproterozoic paragneiss" in the area, while the legends of this map only show orthogneiss varieties. The last item ("granitic orthogneiss") should be paragneiss?
Authors should find an appropriate and consequently used name to distinguish the "granite/granitic (ortho)gneiss" units, even if they don't are sure of the metasedimentary origin stated in their description in this chapter; in some other cases both are named "orthogneiss" (Fig. 4), or simply "gneiss" (Supp. Table 1), or named as "orthogneiss" and "gneiss" respectively (Supp. Table 2), distinguished by age data. This is confusing.
Row 136: Here starts a new chapter without title, which should be "Materials and methods".
Authors should write also about their sampling strategy. Some stratigraphic units are represented with 3-5 samples only, although these may be quite heterogeneous: e.g., KJS-08 for leucogranite gneiss is Ti-depleted and has a positive Eu anomaly, in contrast with the other two samples of this unit.
Row 141: The Suppl. Tables 1 and 2 contain 77 samples, not 78.
Row 165: Overprinted white text should be removed from the photos e, f and i (with captions corrected where necessary), and an appropriate scale bar applied to each.
Row 188-189: It is not a straigthforward thing to apply TAS diagram (designed for unaltered volcanic rocks) to intrusives, and, what's more, to metamorphic gneiss. It should be indicated that "with fields defined by [25]".
Rows 200-201: The references [26,27,28] does not seem appropriate. A/CNK ratio was defined by Shand (1927), A/NK vs A/CNK diagram also was designed by him later and widely used since then without reference (like in [26]). However, if the rock contains accessory apatite, aluminium saturation index (ASI) should be used, corrected by phosphorus content.
Rows 222-223: The caption of Fig. 4 is repeated here, correct caption of Fig. 6 is missing.
Row 243: "Sampes" has to be corrected, and the numbers applied on the diagram axis should be the same sample identifiers as in other figures and tables. Legends indicates 226Ra and 228Ra, while the caption and text says 226Ra and 232Th. (A similar discrepancy also occurs in Supp. Table 2.)
Row 244: The diagrams also show U and Th concentrations not mentioned in the caption; do these come from the chemical analysis?
Author Response
We would like to submit the revised version entitled "Tracking and evaluating the concentrations of natural radioactivity according to chemical composition in the Precambrian and Mesozoic granitic rocks in the Jangsu-gun area, central southwestern South Korea". The original manuscript is revised by following most of the comments of the review 1, and gave our detailed reply to the review comments below.
Reviewer 1: The aims of the paper are not in perfect harmony with the applied methods. Petrogenesis of an igneous-metamorphic assemblage cannot be based on geochemistry alone, without any mineralogical tests and textural observations. Because of this, the conclusions cannot be accepted as valid. However, the dataset presented is worth for interpretation, if the authors change the focus from the petrographic characterization of the rocks to the identification of geochemical factors controlling the gamma activity of the natural rocks.
Remarks on the chapters on geological settings, methods and results are given below.
Chapter "Discussion" is, in fact, not a proper discussion of the results described previously in the paper. All geochemical data are treated as original magmatic compositions, although there are metamorphic rocks with probable sedimentary protoliths and, according to the trace element patterns, even in igneous rocks there is a high probability of post magmatic alterations. Effects of these things should be considered here. Several things come as assumptions not supported by any observations (like monazite should be the main host of Th and U), or from unreferenced sources (like topographical factors). On the other hand, there is nothing about the correlation of the radiometric properties and the chemical composition, although Figure 8 in the results chapter shows at least U and Th concentrations (but not K). Consequently, the outlier values (like measured 226Ra activity of sample JS-68 not supported by measured U concentration) are also not discussed. The data provide a possibility to test how far the stratigraphic group or other factors (like local or regional alterations with special geochemical fingerprints) determine the potential activity, but such things are not discussed - except in the abstract, which is therefore also not harmonized with the text (there is even a literature reference included in the abstract, which is not occurring elsewhere in the text). Instead of this, fractional crystallization is treated without knowing anything from the actual mineral composition of the samples. Plots like figures 10 and 12 cannot be interpreted without this. This part should be completely reconsidered and rewritten, realizing the combined interpretation of the chemical (with emphasis on the trace element geochemistry) and the radiometric test results. The word "petrogeneses" in the title should be changed to "chemical composition". The other possibility is to complete the results with mineralogical tests, e.g., heavy mineral separation and EPMA yielding data on the composition of the U-Th bearing accessories.
Response: In general, we have focused on the revision of 1216044 manuscript to examine the correlation between the protolith age, petrological characteristics and the gamma activity of rocks in the Jangsu-gun area. This study is the first to be studied in South Korea, and it has been reviewed to harmonize the methods and contents applied in the manuscript as much as possible. Especially, we have carefully modified discussion part following the reviewer comment and also added geochronology part to the manuscript because it is worth interpreting the protolith age of rocks in the Jangsu-gun area.
Comment: Rows 109-112: This information does not belong to the geology; it can be left out, or, if necessary, moved to the last paragraph of the introduction.
Response: We have removed rows 109-112 following the review’s comment.
Comment: Rows 119-132: It is not clear if the information described here comes from the literature referred to in the previous sentences containing the age data. The appropriate sources have to be given for this part too, even if it is partly the same as before.
Response: There is misunderstanding here. We have only cited ages by previous reported age dating of the studied rocks. The sentences in rows 119-132 have provided geological information on the occurrences and mineral assemblages of the various rocks investigated during the presented study.
Comment: Row 133: The red hues cannot be distinguished in the image (maybe because of low resolution of the downloaded file). Numbers of the insert map should be enlarged, leaving the superfluous 0 minutes and seconds. There is a contradiction with the map of Figure 1: it indicates extended outcrops of "Middle Paleoproterozoic paragneiss" in the area, while the legends of this map only show orthogneiss varieties. The last item ("granitic orthogneiss") should be paragneiss? Authors should find an appropriate and consequently used name to distinguish the "granite/granitic (ortho)gneiss" units, even if they don't are sure of the metasedimentary origin stated in their description in this chapter; in some other cases both are named "orthogneiss" (Fig. 4), or simply "gneiss" (Supp. Table 1), or named as "orthogneiss" and "gneiss" respectively (Supp. Table 2), distinguished by age data. This is confusing.
Response: We have revised Figures 2 and 3 following the review’s comment.
Comment: Row 136: Here starts a new chapter without title, which should be "Materials and methods". Authors should write also about their sampling strategy. Some stratigraphic units are represented with 3-5 samples only, although these may be quite heterogeneous: e.g., KJS-08 for leucogranite gneiss is Ti-depleted and has a positive Eu anomaly, in contrast with the other two samples of this unit.
Response: We have added 3. Analytical Methods and sampling strategy following the review’s comment. As for the number of samples of some lithological units that are sufficient in this study, we will study with detailed samples in the next study.
Comment: Row 141: The Suppl. Tables 1 and 2 contain 77 samples, not 78.
Response: We have revised the number of analyzed samples.
Comment: Row 165: Overprinted white text should be removed from the photos e, f and i (with captions corrected where necessary), and an appropriate scale bar applied to each.
Response: We have revised Figure 3 following the review’s comment.
Row 188-189: It is not a straigthforward thing to apply TAS diagram (designed for unaltered volcanic rocks) to intrusives, and, what's more, to metamorphic gneiss. It should be indicated that "with fields defined by [25]".
Response: We have revised rows 188-189 following the review’s comment.
Comment: Rows 200-201: The references [26,27,28] does not seem appropriate. A/CNK ratio was defined by Shand (1927), A/NK vs A/CNK diagram also was designed by him later and widely used since then without reference (like in [26]). However, if the rock contains accessory apatite, aluminium saturation index (ASI) should be used, corrected by phosphorus content.
Response: We have revised rows 188-189 following the review’s comment: The Middle Paleoproterozoic orthogneisses and granitic orthogneisses have most weakly peraluminous in an aluminum saturation index (ASI) de-fined by Shand [30], that ranged from 0.95 to 1.20 (Figure 8). The Late Triassic porphyritic biotite granite and Early Jurassic biotite, and two-mica granites are also weakly peraluminous (ASI = 1.00 to 1.39), with the exception of one low ASI (0.7). The Erly Jurassic hornblende-biotite granites ranged from metaluminous to weakly peraluminous (ASI = 0.93 to 1.13).
Comment: Rows 222-223: The caption of Fig. 4 is repeated here, correct caption of Fig. 6 is missing.
Response: We have revised rows 222-223 following the review’s comment.
Comment: Row 243: "Sampes" has to be corrected, and the numbers applied on the diagram axis should be the same sample identifiers as in other figures and tables. Legends indicates 226Ra and 228Ra, while the caption and text says 226Ra and 232Th. (A similar discrepancy also occurs in Supp. Table 2.)
Response: We have revised Figure 10 and Table S3 following the review’s comment.
Comment: Row 244: The diagrams also show U and Th concentrations not mentioned in the caption; do these come from the chemical analysis?
Response: We have revised Figure 10 following the review’s comment.
Reviewer 2 Report
In order to have statistically more significant results and thus to be better focus to your subject, will be needed to take and analyze more samples (at least the double, or better 3-folds more) for the gamma nuclide purpose. So, will be needed more samples for the following rock classes: 1) Middle Paleoproterozoic leucogranitic orthogneiss; 2) Middle Paleoproterozoic porphyritic orthogneiss; 3) Late Triassic porphyritic biotite granite and 4) Early Jurassic two mica granite.
Overall, the descriptions are more shifted to petrological concepts rather than to radioactivity ones, and thus nearly the whole has to be redirected to the later ones.
Author Response
Reviewer 2: The original manuscript is revised by following most of the comments of the review 2, and gave our detailed reply to the review comments below.
In order to have statistically more significant results and thus to be better focus to your subject, will be needed to take and analyze more samples (at least the double, or better 3-folds more) for the gamma nuclide purpose. So, will be needed more samples for the following rock classes: 1) Middle Paleoproterozoic leucogranitic orthogneiss; 2) Middle Paleoproterozoic porphyritic orthogneiss; 3) Late Triassic porphyritic biotite granite and 4) Early Jurassic two mica granite.
Overall, the descriptions are more shifted to petrological concepts rather than to radioactivity ones, and thus nearly the whole has to be redirected to the later ones.
Response: In general, we have focused petrological concepts rather than to radioactivity ones following the reviewer comment (see manuscript). Regarding the insufficient number of analysis samples, it is true that the analysis samples of some rocks distributed in the Jangsu-gun area are statistically insufficient. In a future study, we will proceed with the study by supplementing these points.
Reviewer 3 Report
Very interesting manuscript and study, which could represent a well presented case study on concentrations of natural radioactivity in grenites, which is a problem worldwide. The text is well written and presented, the intention of the study is clear and conclusions are well presented.
Most of text is written is written in past. The observations given in the study are still correct, and therefore, presence would be appropriate, e.g., from L. 27 onwards.
Specific remarks
- 20: No citation in the abstract.
L.. 38: What do you mean with high potential element?
- 49-50: “However, the natural radioactivity in some rocks can also cause high radiation exposure”: Add a reference to the statement.
- 91: “The recommended standards for 226Ra, 232Th, and 40K”: Add a reference to the statement.
- 109-112: “On the other hand, the administrative district of South Korea consists of 1 special city 109 (Seoul), 6 metropolitan cities, 8 provinces, 1 special autonomous city and 1 autonomous 110 province. The 4 metropolitan cities and 8 provinces consist of 80 guns, including Jangsu-111 gun (Fig. 2)” I find that this statement is not needed except saying that S Korea consists of 80 guns, where a gun corresponds approximately to a county.
- 121-122: “with metasedimentary rocks (biotite gneiss with granitic gneiss, schist, and 121 marble) and minor pegmatitic dikes and amphibolites“: Express this statement more distinct. A significand part is not metasedimentary.
- 141: “Analytical uncertainties ranged from 1% to 3%”: Add more details, e.g. background values, e.g. in the Supplementary Table 1.
- 166-169: four times “showing”: Replace some of them by another word.
- 208: “common light REE enrichments with (La/Yb)N ratios of 2.0–112.4”: variation is very large, try to explain values explicitely.
- 261-265: Sentence sounds somehow circular. Give more details on NORM values of each of the granite suites of different ages.
- 412-413: “that monazite is the main accessory mineral controlling the concentration of NORMs”: Give more details why monazite.
Fig. 2: Correct in legend to dikes (as in the text. Correct Leucoranitic
Author Response
The original manuscript is revised by following most of the comments of the review 3, and gave our detailed reply to the review comments below.
Reviewer 3: Very interesting manuscript and study, which could represent a well presented case study on concentrations of natural radioactivity in granites, which is a problem worldwide. The text is well written and presented, the intention of the study is clear and conclusions are well presented.
Comment: Most of text is written is written in past. The observations given in the study are still correct, and therefore, presence would be appropriate, e.g., from L. 27 onwards.
Response: We have revised manuscript following the review’s comment.
Specific remarks
Comment: 1p. line 20: No citation in the abstract.
Response: We have removed citation in the abstract.
Comment: 1p. line 38: What do you mean with high potential element?
Response: We have replaced element with area.
Comment: 2p. lines 49-50: “However, the natural radioactivity in some rocks can also cause high radiation exposure”: Add a reference to the statement.
Response: We have cited references to the statement.
Comment: 3p. lines 94-96: “The recommended standards for 226Ra, 232Th, and 40K”: Add a reference to the statement.
Response: We have cited a reference to the statement following the review’s comment.
Comment: 3p. lines 109-112: “On the other hand, the administrative district of South Korea consists of 1 special city 109 (Seoul), 6 metropolitan cities, 8 provinces, 1 special autonomous city and 1 autonomous 110 province. The 4 metropolitan cities and 8 provinces consist of 80 guns, including Jangsu-111 gun (Fig. 2)” I find that this statement is not needed, except saying that S Korea consists of 80 guns, where a gun corresponds approximately to a county.
Response: We have removed the statement in the lines 109-112.
Comment: 3p. lines 123-133: “with metasedimentary rocks (biotite gneiss with granitic gneiss, schist, and 121 marble) and minor pegmatitic dikes and amphibolites“: Express this statement more distinct. A significant part is not metasedimentary.
Response: We have revised the statement in the lines 109-112 as follows: The Middle Paleoproterozoic gneisses consist mainly of orthogneisses (granite orthogneiss, leucogranitic orthogneiss, and porphyritic orthogneiss) with metasedimentary rocks (biotite gneiss and schist) and minor pegmatitic dikes and amphibolites (Figure 3a–f). The Middle Paleoproterozoic biotite gneisses also include granitic gneiss and minor pegmatitic dikes and amphibolites.
Comment: 5p. lines 141: “Analytical uncertainties ranged from 1% to 3%”: Add more details, e.g. background values, e.g. in the Supplementary Table 1.
Response: We have added the statement in the lines 153-155 as follows: Detailed analytical procedures, conditions, and detection limits for major, trace and REE elemental analyses are summarized in http:www.actlabs.com.
Comment: 6p.182-188: four times “showing”: Replace some of them by another word.
Response: We have replaced “showing” with “having or with” following the review’s comment.
Comment: 7p. line 226: “common light REE enrichments with (La/Yb)N ratios of 2.0–112.4”: variation is very large, try to explain values explicitly.
Response: The large wide range of summarized (La/Yb)N ratios for eight rocks seems to degrade the reliability of the analyses. We have removed the statement in the line 226.
Comment: 8.261-265: Sentence sounds somehow circular. Give more details on NORM values of each of the granite suites of different ages.
Response: For the detailed NORM values of each of the granite suites of different ages, we have already suggested in gamma nuclide analysis part.
Comment: 9p. lines 412-413: “that monazite is the main accessory mineral controlling the concentration of NORMs”: Give more details why monazite.
Response: We have revised sentence following the review’s comment: The compositional trends of trace elements (e.g., U, Th, Zr, and Y, and REEs) from the Middle Paleoproterozoic orthogneisses and Late Triassic and Early Jurassic granitic rocks in the Jangsu-gun area indicates that monazite is the main accessory mineral controlling the concentration of NORMs in peraluminous Middle Paleoproterozoic orthogneiss and Early Jurassic biotite and two mica granites. In contrast, allanite is main accessory minerals in metaluminous Early Jurassic hornblende-biotite granite.
Comment: Fig. 2: Correct in legend to dikes (as in the text. Correct Leucoranitic)
Response: We have revised terms in legend following the review’s comment.
Round 2
Reviewer 1 Report
Spell checks may be useful also on images (Fig. 2: "sample lacations").
Author Response
The followings are the point-by-point responses:
Comment: Replace “sample lacations” with “sample locations” in figure 2;
Response: We have replaced sample lacations with sample locations following the review’s comment.
Comment: In the text and captions, choose between “granitic orthogneiss” and “granite orthogneiss” and use the same expression throughout the manuscript;
Response: We have used granite orthogneiss throughout the manuscript following the review’s comment.
Comment: In line 364, replace “common” with “commonly” and “unranite” by “uraninite”.
Response: We have replaced “common” with “commonly” and “unranite” by “uraninite” following the review’s comment.
Comment: In lines 374-376, the sentence has no meaning. Do you mean that the correlation between the activity of the nuclides and the concentration of the elements are the consequence of fractionation processes and post-orogenic events? If so, please rephrase the sentence.
Response: We have removed “resulting in various partial melted migmatization or post orogenic event” (Line 374-375)
Comment: Line 391, replace “although zircon, apatite, titanite, and monazite” by “although zircon, apatite, and titanite. As you mentioned monazite as the main accessory mineral in line 389, it does not make sense to invoke monazite again as a possible accessory mineral.
Response: We have replaced “although zircon, apatite, titanite, and monazite” with “although zircon, apatite, and titanite.
Comment: Line 415, replace “have weak to medium fractional crystallization of degree” by “have weak to medium degree of fractional crystallization”.
Response: We have replaced “have weak to medium fractional crystallization of degree” with “have weak to medium degree of fractional crystallization”.
Comment: In addition, special attention is required for remark #9 of reviewer #3 regarding monazite. The reviewer asked for more details on monazite to explain why this mineral is the main accessory mineral that controls the concentration of NORMs. The text has been modified to meet the reviewer´s request, but in my opinion, this point has not been sufficiently explained. As this is one of your main findings of the study, which is highlighted in the conclusion, I suggest providing more solid arguments to support this conclusion. I think that the reviewer was waiting for a more detailed explanation based on the geochemical characteristics of monazite which could justify this assertion, in particular on the content of Th.
Response: We have inputted more detailed explanation on monazite following the review’s comment: This reason can be assumed that monazite is the main accessory mineral controlling the concentrations of NORMs in Middle Paleoproterozoic and Early Jurassic rocks distributed in Jangsu-gun area, although zircon, apatite, and titanite can generally be produced as accessory minerals containing U and Th in the rocks. Monazite well exhibit strong compositional differences at a variety of scales in the granitic rocks [35]. In addition, monazite in peraluminous granites is reported to be of higher importance for the rock budget of all the investigated elements (etc. U, Th and Y) in peraluminous granites than zircon as an important carrier of Y and U [36].
Reviewer 2 Report
Some more text editing is required in order to be better understand the meaning of the phrases in different parts of the paper.
Author Response
The followings are the point-by-point responses:
Comment: Replace “sample lacations” with “sample locations” in figure 2;
Response: We have replaced sample lacations with sample locations following the review’s comment.
Comment: In the text and captions, choose between “granitic orthogneiss” and “granite orthogneiss” and use the same expression throughout the manuscript;
Response: We have used granite orthogneiss throughout the manuscript following the review’s comment.
Comment: In line 364, replace “common” with “commonly” and “unranite” by “uraninite”.
Response: We have replaced “common” with “commonly” and “unranite” by “uraninite” following the review’s comment.
Comment: In lines 374-376, the sentence has no meaning. Do you mean that the correlation between the activity of the nuclides and the concentration of the elements are the consequence of fractionation processes and post-orogenic events? If so, please rephrase the sentence.
Response: We have removed “resulting in various partial melted migmatization or post orogenic event” (Line 374-375)
Comment: Line 391, replace “although zircon, apatite, titanite, and monazite” by “although zircon, apatite, and titanite. As you mentioned monazite as the main accessory mineral in line 389, it does not make sense to invoke monazite again as a possible accessory mineral.
Response: We have replaced “although zircon, apatite, titanite, and monazite” with “although zircon, apatite, and titanite.
Comment: Line 415, replace “have weak to medium fractional crystallization of degree” by “have weak to medium degree of fractional crystallization”.
Response: We have replaced “have weak to medium fractional crystallization of degree” with “have weak to medium degree of fractional crystallization”.
Comment: In addition, special attention is required for remark #9 of reviewer #3 regarding monazite. The reviewer asked for more details on monazite to explain why this mineral is the main accessory mineral that controls the concentration of NORMs. The text has been modified to meet the reviewer´s request, but in my opinion, this point has not been sufficiently explained. As this is one of your main findings of the study, which is highlighted in the conclusion, I suggest providing more solid arguments to support this conclusion. I think that the reviewer was waiting for a more detailed explanation based on the geochemical characteristics of monazite which could justify this assertion, in particular on the content of Th.
Response: We have inputted more detailed explanation on monazite following the review’s comment: This reason can be assumed that monazite is the main accessory mineral controlling the concentrations of NORMs in Middle Paleoproterozoic and Early Jurassic rocks distributed in Jangsu-gun area, although zircon, apatite, and titanite can generally be produced as accessory minerals containing U and Th in the rocks. Monazite well exhibit strong compositional differences at a variety of scales in the granitic rocks [35]. In addition, monazite in peraluminous granites is reported to be of higher importance for the rock budget of all the investigated elements (etc. U, Th and Y) in peraluminous granites than zircon as an important carrier of Y and U [36].
