Review Reports - Detrital Zircon Geochronology and Tectonic Evolution Implication of the Middle Jurassic Zhiluo Formation, Southern Ordos Basin, China

Round 1

Reviewer 1 Report (New Reviewer)

This manuscript by Cui et al. is potentially a good paper. The subject matter of the research has certain guiding and reference significance for studying the sedimentary evolution and tectonic evolution of the Zhiluo Formation in the basin and even the Jurassic in North China, and for these reasons it represents an important work. I suggest that it be accepted after Minor Revision, Thank you.

Specific comments are as follows:

1. Line 20: Modify as “an integrated analysis”

2. Line 52: Modify as “the detrital zircon dating”

3. Line 93: Figure 1, the alignment is centered

4. Line 511: Delete should.

5. Line 599: “6.2.5. From 461.04 to 412.61 Ma, the strong peak is 432.5 Ma. The zircon age in this range corresponds to the Late Caledonian tectonic event.” and “6.2.4" are repeated or written incorrectly, please check!

6. Line 648: Figure 10, the alignment is centered

7.Line 714-732: The number format of the conclusion is 1. 2. 3... or 7.1. 7.2 ...?

Author Response

Response to Reviewers’ Comments

Dear Editor and Reviewers,

Thank you for your helpful comments on our manuscript “Detrital zircon geochronology and tectonic evolution implication of the Middle Jurassic Zhiluo Formation, southern Ordos Basin, China”. After considering all issues mentioned in the reviewers’ comments, we made careful revisions, and replied all comments one by one. Every change made in response to the reviewers’ comments are outlined in the tracked version of our revised manuscript. Here are the details.

Comments from Reviewer #1

Specific comments are as follows:

Comment 1: Line 20: Modify as “an integrated analysis”

Reply: Thank you for the suggestion! “an analysis” has been modified to “an integrated analysis” (Line 20).

Comment 2: Line 52: Modify as “the detrital zircon dating”

Reply: Thank you for the suggestion! “a detrital zircon experiment” has been modified to “the detrital zircon dating experiment” (Line 51).

Comment 3: Line 93: Figure 1, the alignment is centered

Reply: Thank you for the suggestion! Figure 1, the alignment is already centered (Line 92).

Comment 4: Line 511: Delete should

Reply: Thank you for the suggestion! “should be” has been deleted and changed to “was”. (Line 511)

Comment 5: Line 599: “6.2.5. From 461.04 to 412.61 Ma, the strong peak is 432.5 Ma. The zircon age in this range corresponds to the Late Caledonian tectonic event.” and “6.2.4" are repeated or written incorrectly, please check!

Reply: We are very sorry for the mistake! “6.2.5. From 461.04 to 412.61 Ma, the strong peak is 432.5 Ma. The zircon age in this range corresponds to the Late Caledonian tectonic event.” has been changed to “From 257.65 to 208.44 Ma, the strong peak is 218.7 Ma. The zircon age in this range corresponds to the Late Caledonian tectonic event”. (Line 558,559)

Comment 6: Line 648: Figure 10, the alignment is centered

Reply: Thank you for the suggestion! Figure 10, the alignment is already centered (Line 648).

Comment 7: Line 714-732: The number format of the conclusion is 1. 2. 3... or 7.1. 7.2 ...?

Reply: Thank you for the suggestion! The number format of the Conclusion is 1. 2. 3. ...

Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

The work is well organised and the presented data are consistent with the interpretations. I suggest including a petrographic description of the studied samples to better constrain the palaeogeographical evolution of the basin.

In the attached PDF file some suggestions.
The manuscript may be accepted after minor revisions

Comments for author File: Comments.pdf

Author Response

Response to Reviewers’ Comments

Dear Editor and Reviewers,

Comments from Reviewer #2

The manuscript may be accepted after minor revisions

In the attached PDF file some suggestions.

Detailed comments are as follows:

Comment 1: Words and sentences errors.

Reply: We have revised the whole manuscript in English for words, and sentences, etc.

“peripheral tectonism” has been changed to “surrounding tectonism”. (Line 11, Line 101)

“peak” has been changed to “peaks”. (Line 16, Line 470)

“based on the basin’s sand-stone thickness and net–sand ratio maps” has been deleted.

“Achaean” has been changed to “Archean”. (Line 98)

“terrestrial” has been changed to “continental”. (Line 99)

“histogram” has been changed to “evolution”. (Line 153)

“CL was used to image the zircons” has been changed to “CL was used to obtain the images of zircons”. (Line 220)

“analyte” has been changed to “analytical”. (Line 230)

“and Th/U ratios” has been deleted.

“graphic” has been deleted.

“magma” has been changed to “magmatic”. (Line 439)

“tonomagmatic ” has been changed to “tono-magmatic ”. (Line 440)

“occurrences” has been changed to “signatures”. (Line 441)

“tectonic magmatism” has been changed to “tectonism”. (Line 484)

“movement” has been deleted. (Line 494,507)

“Muscovite” has been changed to “muscovite”. (Line 498)

“S type” has been changed to “S-type ”. (Line 521)

“material sources for” has been changed to “materals to”. (Line 528)

“midlate” has been changed to “middle”. (Line 587)

“subtrachytal” has been changed to “trachyandensite”. (Line 601)

“docked” has been changed to “finally merged”. (Line 621)

“growth, and combination a new crust and formed a unified NCC basement” has been changed to “growth and convergence, and formed a unified NCC basement”. (Line 633)

“realized combination” has been changed to “overlapped”. (Line 637)

“excessive” has been deleted.

“mid” has been changed to “middle”. (Line 657,673)

Comment 2: What is experiment?

Reply: We are sorry for the unclear explanation. “a detrital zircon experiment” has been changed to “the detrital zircon dating experiment”. (Line 51)

Comment 3: add Fornelli et al. 2020 Building an Orogen: Review of U-Pb Zircon Ages from the Calabria–Peloritani Terrane to Constrain the Timing of the Southern Variscan Belt. Minerals 10, 944 and Fornelli et al. 2022 Detrital zircon ages of Oligocene to Miocene sandstone suites of the Southern Apennines foreland basin system, Italy. Journ. Paleog.

Reply: Thank you for the suggestion. We have added “References (Line 823-828)

Fornelli, A.; Festa, V.; Micheletti, F.; Spiess, R.; Tursi, F. Building an Orogen: Review of U-Pb Zircon Ages from the Calabria–Peloritani Terrane to Constrain the Timing of the Southern Variscan Belt. Minerals. 2020, 10(11), 944.

Fornelli, A.; Micheletti, F.; Gallicchio, S.; Tursi, F.; Criniti, S.; Critelli, S. Detrital zircon ages of Oligocene to Miocene sandstone suites of the Southern Apennines foreland basin system,Italy. Journal of Palaeogeography. 2022, 11(002): 222–237.

Comment 4: the form is not clear“a small number of sedimentary and volcanic rock lithologic assemblages from Sinian, Paleozoic, and Mesozoic–Cenozoic”

Reply: We are sorry for the unclear explanation. “a small number of sedimentary and volcanic rock lithologic assemblages from Sinian, Paleozoic, and Mesozoic–Cenozoic” has been changed to “a small number of Sinian, Paleozoic, and Mesozoic–Cenozoic sedimentary and volcanic rocks”. (Line 133,134)

Comment 5: Describe the internal textures of zircons. Some crystals show a magmatic origin, others are modified....

Reply: Thank you for the suggestion. The description have added.

In addition, some zircon crystals show magmatic origin with round or polygonal cores and present different gray characteristics, others have been modified due to metamorphic origin with lack of internal structures (Figure 4). (Line 258-260)

Comment 6: I suggest including a petrographic description of the studied samples.

Reply: Thank you for the suggestion. the description of the studied samples have added.

A set of gray-green and purple (fine) gravel-medium-coarse sandstone intercalated with green and purple mud gravel or lenticular silty sandstone was collected from the Zaoshugou section outcrop in the Yongshou area, southern Ordos Basin for this study. The outcrop has parallel bedding with poor sorting and medium roundness. Feldspathic quartz sandstone, feldspathic sandstone, and feldspathic lithic sandstone constitute the particle composition. (Line 203-208)

Comment 7: Figure 4, make the dimensions of image boxes equal

Reply: Thank you for the suggestion. We have revised the Figure 4. (Line 261)

Figure 4. CL images and age value (Ma) of representative detrital zircons from the lower member of the Zhiluo Formation.

Comment 8: add Fornelli et al. 2014 The role of trace element partitioning between garnet, zircon and orthopyroxene on the interpretation of zircon U–Pb ages:an example from high-grade basement in Calabria (Southern Italy). Intern J. earth Sc 103:487-507. Discuss the REE distribution of zircon with magmatic source

Reply: Thank you for the suggestion. We have added “Reference and discussed the REE distribution of zircon with magmatic source ”.

the REEs domains vary from 928.14 to 21,116.95 ppm and show a relatively steep pattern with low LREE (35.55 to 1,724.80 ppm), high HREE (918.75 to 20,636.48 ppm) contents,, negative Eu anomalies, positive Ce (Figure 5, Table S1), and high Th/U (between 0.30 and 1.31) ratios (Figure 6). It demonstrates that the majority of detrital zircons are magmatic in origin [71-73].(Line 275-279)

Fornelli, A.; Langone, A.; Micheletti, F.; Pascazio, A.; Piccarreta, G. The role of trace element partitioning between garnet, zircon and orthopyroxene on the interpretation of zircon U–Pb ages:an example from high-grade basement in Calabria (Southern Italy). Intern J. earth Sc. 2014. 103:487-507. (Line 938-940)

Comment 9: “6.2.1., 6.2.2., 6.2.3., 6.2.4., 6.2.5.” No sub section.

Reply: Thank you for the suggestion. We have deleted “6.2.1., 6.2.2., 6.2.3., 6.2.4., 6.2.5.”

Comment 10: Are these rocks metamorphites or sedimentary with a metamorphic component?

Reply: We are sorry for the unclear explanation. “metamorphic sandstone has been changed to “metasandstone”. (Line 482)

Comment 11: “The Rb–Sr dating” micas -whole rock?

Reply: It used the whole sample for Rb–Sr dating.

Comment 12: You discuss the late indosinian ages!!! “6.2.5. From 461.04 to 412.61 Ma, the strong peak is 432.5 Ma. The zircon age in this range corresponds to the Late Caledonian tectonic event.”

Comment 13: “magmatic activity was moderately weak”was missing? or no exposed

Reply: We are sorry for the unclear explanation. It was not exposed and has been changed to “indicating that magmatic activity was moderately weak and not exposed”. (Line 570)

Comment 14: “the QOB solely provides clastic materials”, this sentence is not clear. Clastic materials indicate source rocks

Reply: We are sorry for the unclear explanation. “the QOB solely provides clastic materials” has been changed to “the QOB solely provides a small amount of clastic materials”. (Line 580)

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

GENERAL COMMENTS

This paper reports the detrital zircon population from a Middle Jurassic sandstone from the southern Ordos Basin on the western margin of the North China block (NCB). The results are compared favourably with another detrital zircon population from the region and the combined result is compared to the surrounding tectonic terrains to determine provenance. This information is combined with paleocurrent data and sandstone/siltstone ratios to show that the provenance of the sediments is from the south, which is consistent with the detrital zircon populations being derived from the Qinling/Qilian orogenic belt to the south, following major uplift in the Early Mesozoic.

The paper also provides an extensive and informative review of the tectonic history of the surrounding tectonic entities, which date back to the Archean, and it discusses the potential contribution of these terrains to the Jurassic Zhiluo Fm, concluding that the only NCB might contribute some material, other than Qinling/Qilian. The authors use the tectonic evolution of the surrounding Phanerozoic orogens to combine with the sedimentological history of the Ordos basin to provide a comprehensive history of the evolution of the western NCB.

RECOMMENDATION

MINOR REVISION. I think the authors have achieved their aims. The paper reads well, is well organised and logical. It could be shortened somewhat, especially in relation to tectonic history of the surrounding regions, but overall is a nice piece of work.

Check for spelling errors and provide more information for the figure captions. Finally, put numerical values on the various geological periods that you use. Some are local, others are ambiguous, so numbers in Ma are important.

SPECIFIC COMMENTS

SPELLING ERRORS!!

13 Add Middle Jurassic before Zhiliuo

19 Early Luliang, Late Luliang–Early Jinning, Late Jinning are local terms for geological periods. Add age brackets

31 In geological terms, explain what is “energy formation”

47 Add (Fig. 1) at the end of the sentence.

59 “provided”.

72 “numerous”

96 Fig 1c needs to be explained in the caption

108 what age range for Yanshanian?

123 I thought SSZ refers to “suprasubduction zone” ophiolite

177 Can you be more specific about the “J2z1”, J2z2, etc periods. What is the age range in Ma?

387-391 I think you re taking the discrimination diagrams in Figs 9g & h too far. Unfortunately, the original authors of such diagrams (Belousova et al 2002) did not use a sufficiently broad dataset. Most of the diagrams show that the zircons come from continental arc granitoids and that is sufficient information to provide. I would delete Figs 9g and 9h as they are a distraction.

439 Label the relevant colour columns in Fig 10, Hercynian, etc.

438-448. There is a contradiction here. You state “the Hercynian magmatic rocks are the most common” but then say “However, the samples obviously lack Hercynian zircons”. Please clarify.

473 Where are the Helan and Luliang mountains in Fig 1?

561 “During this period “ WHEN??

661-2 I would say that the NCB contributed very little to the Zhilou Fm. The small 2.5 and 1.8 Ga peaks are much more similar to the Qilian/Qiling orogen.

684 When is Late Indosinian?

708 When is the Yan’an Formation’s sedimentary period?

718 You state “Based on the provenance analysis, the southern margin of the SNCB is thought to 718 represent the main provenance area of the Zhiluo Formation…”, but Fig. 10 shows the 1.8 and 2.5 peaks are absent/muted. I don’t see the SNCB source, especially as you say that the SNCB is the southern margin of the Zhiluo Fm (ie., it was underneath).

Reviewer 2 Report

Comments for author File: Comments.pdf