Zircon U–Pb Geochronology, Whole-Rock Geochemistry and Petrogenesis of Biotite Granites in the Gaudeanmus Area, Namibia
Round 1
Reviewer 1 Report
The paper are very interesting and important, but are needed some descriptions . In the abstract should write the name of the continent after Damara Orogen (12)line. Then in the abstract...ancient Nd isotope ...should write Sm-Nd isotope crust model ages instead of Nd crust model ages(21)line. In 1 introdaction should write zircon U-Pb isotope age instead of radiometric age(47) line.In 3 Analytical methods in line 103 should write after crushed samples (10, or another kg?) in order to understand about correstion materials to dating.
Table 3 are needed to discribed how results were done, from previous works ,or referenses materials from another papers. So the table are a very strange. Should write name of the mass-spectrometers, spike or another methods were used to isotope initial rations Nd and Sr,so these methods are needed spike calibration and high mashines or mass-spectrometric studyes.It is a most important comments in this paper so all conclusios based on precise isotope data. The referenses materias (more than 3/4) contan more papers from 20 century instead of 21.
Author Response
Response to Reviewer 1 Comments
Point 1: In the abstract should write the name of the continent after Damara Orogen (12)line. Then in the abstract...ancient Nd isotope ...should write Sm-Nd isotope crust model ages instead of Nd crust model ages(21)line. In 1 introdaction should write zircon U-Pb isotope age instead of radiometric age(47) line.In 3 Analytical methods in line 103 should write after crushed samples (10, or another kg?) in order to understand about correstion materials to dating.
Response: As you suggested we have revised it.
Point 2: Table 3 are needed to discribed how results were done, from previous works ,or referenses materials from another papers. So the table are a very strange. Should write name of the mass-spectrometers, spike or another methods were used to isotope initial rations Nd and Sr,so these methods are needed spike calibration and high mashines or mass-spectrometric studyes.
Response: As you suggested we have revised it. In the part of 3.2 geochemical analysis, we have described in detail.
Reviewer 2 Report
The manuscript represents zircon U-Pb geochronology, whole-rock geochemistry and assumption on petrogenesis of biotite granites in the Gaudeanmus area, Namibia. In total the aim of the research is obtained. But the manuscript contains a lot of misprints and mistakes (especially in reference list). The main remark from the reviewer is too limited quantity of studied samples, only five. In Discussion too many repeats from Analitical results. The manuscript needs in moderate revision.
Comments by lines:
1 = ArticAL replace to Article.
15 and other = age 540.2+/-3.9 replace to 540+/-4 because the accuracy of the LA-ICP-MS method is not better than 1-2% (5-10 Ma for 540 Ma).
18 and other = Th is not LILE, it’s HFSE.
21 = ɛNd(t) cannot be initial (in Abstract intial (!). It’s a shift of Nd-ratio for rock regarding CHUR.
Fig. 1 = SCSLE replace to SCALE.
82 = wang replace to Wang.
93 = post-crystalization replace to after crystallization.
Fig. 3 = Use abbreviations for names of rock-forming minerals after Whitney and Evans (American Mineralogist, Volume 95, pages 185–187, 2010). E.g. Srt replace to Ser, and so on.
116 = Jaekson is absent in reference list.
Table 1 and other = content (*10-6) replace to content (ppm). Add D (discordance, %) and Rho parameters.
150 and other = Calculate concordant age using Isoplot.
153 and other = 1907.1 and 1033. Why not 1907 and 1033. See comment to line 15.
165 = Ti2O replace to TiO2.
Table 2 = Two analysis have sum 105% and 103%. They should be rejected. But authors have only 5 analysis. δEu replace to Eu/Eu*. It is not necessary to explain what is REEN. But author should explain what REE are LREE, and HREE, in their opinion.
205 = What is the link between Nb and P and plagioclase? Above authors write that P is caused by apatite.
261-269 = Direct repeat from the Results text.
302 = crustally derived replace to derived from the crust.
References are not formatted at all.
Author Response
Response to Reviewer 2 Comments
Point 1: Line 1. ArticAL replace to Article. Line 15 and other = age 540.2+/-3.9 replace to 540+/-4. Line 21. ɛNd(t) cannot be initial (in Abstract intial (!). It’s a shift of Nd-ratio for rock regarding CHUR. Fig. 1 SCSLE replace to SCALE. Line. 82 wang replace to Wang. Line 93 post-crystalization replace to after crystallization. Fig. 3 Use abbreviations for names of rock-forming minerals after Whitney and Evans (American Mineralogist, Volume 95, pages 185–187, 2010).
Response: As you suggested we have revised it.
Point 2: Line. 116 Jaekson is absent in reference list. Table 1 and other content (*10-6) replace to content (ppm). Add D (discordance, %) and Rho parameters. Line 165 Ti2O replace to TiO2.
Response: As you suggested we have revised it.
Point 3: Table 2 = Two analysis have sum 105% and 103%. They should be rejected. But authors have only 5 analysis. δEu replace to Eu/Eu*. It is not necessary to explain what is REEN. But author should explain what REE are LREE, and HREE, in their opinion. Line. 302 crustally derived replace to derived from the crust.
Response: As you suggested we have revised it. Fe2O3T in Table 2 is the sum of Fe2O3 and FeO converted to Fe2O3. So the TOTAL in Table 2 is wrong and I have corrected the calculated data. At the same time, the related description is made in the analytical method.
Reviewer 3 Report
This manuscript presents new U-Pb zircon age and whole rock geochemical data on Cambrian granitoids in the Damara Orogen, Namibia. The results are new, and the interpretations are mainly consistent with the data. The manuscript is not a major advancement in the science but does present some useful data for understanding the Damara Orogen and crustal magmatism. The main problem with the manuscript is that the sample locations are not given in any of the tables or on the maps. The paper should not be accepted for publication until precise location data are provide. Otherwise the results will have no long-term use for the scientific community. The writing / syntax needs some attention and revision before publication. There are numerous sentence fragments and awkward phrases that should be cleaned up.
Line 74. There are additional data on the crystallization ages on the basement in Foster et al., 2015.
Line 77. A reference should be added for the Damara Stratigraphy
Figure 1. Check spelling of Karibib
Figure 2. This map is a low-resolution reproduction of a published map and needs to be redrafted with sample locations from this study. Label the Gaudenmus area on the map so readers know where it is. A statement of what defines the Gaudeanmus area should also be included in the introduction. Readers will not know where it is or what it represents.
Line 88. This fragment is an example of some of the syntax issues with the text. I did not attempt to correct the English writing, but it does need to be addressed and corrections made throughout. The following sentence is also awkward and should be re-phrased.
Line 151. The concordance filter for the zircon data needs to be defined. There were about 30 zircon grain analyzed and only about 10 are used for the crystallization age calculation. Please define the procedure for identifying discordant grains and ignoring them.
Line 176. It is highly unlikely that this is due to magmatic differentiation as these elemental trends are expected with any increase in SiO2 in a granitic suite. With the different generations of melt, cross cutting and intruding one another it is more likely that the apparent trends are just different batches of partial melt of different source compositions.
Table 2. These samples should be identified on the map in Figure 2.
The coordinates of the sample locations also need to be included in this or another table. The paper cannot be accepted for publication without inclusion of the sample locations.
Line 205. These anomalies could also be due to apatite and oxide remaining in the source.
Lines 340-347. There is mainly speculation in this paragraph about the changing tectonic settings before and after 540 Ma, and what processes could have driven partial melting. Perhaps the authors could put their interpretation into a broader tectonic context e.g. Goscombe et al., 2017 a,b, or another.
Foster, D.A., Goscombe, B.D., Newstead, B., Mapani, B., Mueller, P.A., and Gregory, L., Muvangua, E., 2015, U-Pb age and Lu-Hf isotopic data of detrital zircons from Neoproterozoic Damara sequence: implications for pre-Gondwana proximity of Congo and Kalahari. Gondwana Research, v. 28, p. 179-190, http://dx.doi.org/10.1016/j.gr.2014.04.011.
Goscombe, B., Foster, D.A., Gray, D., Wade, B., Marsellos, A., and Titus, J., 2017, Focus Paper: Deformation correlations, stress field switches and evolution of an orogenic intersection: the Pan-African Kaoko-Damara orogenic junction, Namibia: Geoscience Frontiers, 8, 1187-1232, http://dx.doi.org/10.1016/j.gsf.2017.05.001.
Goscombe, B., Foster, D.A., Gray, D., Wade, B., 2017, GR Focus Review: Metamorphic response and crustal architecture in a classic collisional orogen: The Damara Belt, Namibia: Gondwana Research, 52, 80-124, http://dx.doi.org/10.1016/j.gr.2017.07.006.
Author Response
Response to Reviewer 3 Comments
Point 1: Line 74. There are additional data on the crystallization ages on the basement in Foster et al., 2015. Line 77. A reference should be added for the Damara Stratigraphy. Figure 1. Check spelling of Karibib.
Response: As you suggested we have revised it.
Point 2: Line 74. There are additional data on the crystallization ages on the basement in Foster et al., 2015. Line 77. A reference should be added for the Damara Stratigraphy. Figure 1. Check spelling of Karibib.
Response: As you suggested we have revised it.
Point 3: Figure 2. This map is a low-resolution reproduction of a published map and needs to be redrafted with sample locations from this study. Label the Gaudenmus area on the map so readers know where it is. A statement of what defines the Gaudeanmus area should also be included in the introduction. Readers will not know where it is or what it represents.
Response: As you suggested we have revised it. Figure 2 was redrawn and the approximate location of the Gaudeanmus area was marked.
Point 4: Line 151. The concordance filter for the zircon data needs to be defined. There were about 30 zircon grain analyzed and only about 10 are used for the crystallization age calculation. Please define the procedure for identifying discordant grains and ignoring them.
Response: As you suggested we have revised it. The description of the zircon U-Pb chronology results is redefined.
Point 5: Table 2. These samples should be identified on the map in Figure 2. The coordinates of the sample locations also need to be included in this or another table. The paper cannot be accepted for publication without inclusion of the sample locations.
Response: As you suggested we have revised it. In Figure 2, the sample location is marked and the sample coordinate table is added.
Round 2
Reviewer 1 Report
The paper are a very interesting and after some revision which coauthor were done will be soon published!Please accept many thanks for nice isotope results and important geology!
Best wishes!
Author Response
Dear Sir/Madam
Thank you for your review of our manuscript. We greatly appreciate the opportunity that we have been given to further revise the manuscript. The thoughtful comments and specific suggestions provided by you have helped us tremendously to improve the quality of our manuscript. We are really grateful for the excellent suggestions we have received.
Best wishes!
Reviewer 2 Report
I have few remarks to the manuscript still.
Authors have to correct:
Value of the age everywhere. E.g. 540 Ma instead 540.2. On the Fig. 4 too. Line 18 in abstract - U is not LILE, it's HFSE. Change Jaekson to Jackson (Line 115).Comments for author File: 
Comments.pdf
Author Response
Dear Sir/Madam
Thank you for your review of our manuscript. We greatly appreciate the opportunity that we have been given to further revise the manuscript. The thoughtful comments and specific suggestions provided by you have helped us tremendously to improve the quality of our manuscript. We are really grateful for the excellent suggestions we have received. Thorough and extensive revisions have been made throughout the manuscript following the comments and suggestions from you.
Best wishes!
