Geochronology, Geochemistry, and Lu-Hf Isotopic Compositions of Monzogranite Intrusion from the Chang’anpu Mo Deposit, NE China: Implications for Tectonic Setting and Mineralization

Round 1

Reviewer 1 Report

Reviewed paper presents the results of a predominantly geochemical study of granitoids hosting Chang’anpu Mo deposit in Northern China. Study is based on seventeen samples of monzogranites investigations. The paper contain new data on the granitioids geochemistry and can be published in Minerals after some corrections. Some general comments:

1. Not all lines are numbered, which makes it difficult to review the manuscript;

2. Geological structure of studied deposit is described too briefly, it is better to give a more complete description;

3. It is necessary to describe monzogranites petrography more detail;

4. Fugure 3 need some corrections (see attached PDF file);

5. The authors argue that the granitoid source is only the partial melting of the thickened lower crust. However, they do not pay attention to the fact that the subducting slab can also melt and form a granitoid melt (lines 84-85, 114-115);

6. More detail comments are shown at the attachtd PDF file of the manuscript.

Comments for author File: Comments.pdf

Author Response

Dear reviewer:

I am very grateful to your comments for the manuscript. According with your comment and request, we amended the relevant part in manuscript. Here, we attached revised manuscript in the formats of MS word, for your approval.

 

 

 

Thank you very much.

 

Sincerely

Yanchen Yang

Author Response File: Author Response.doc

Reviewer 2 Report

 

The work pretends to be a synthesis of available data and ideas on the Mo porphyry deposits in the Lesser Khingan Mountains-Zhangguangcai Mountains metallogenic belt in addition to the original data on one of these deposits that” is not only helpful to understand the process of diagenesis and mineralization, but also can reflect the tectonic evolution process controlling the formation of intrusions and ore deposits”.

The data are presented in six well organized tables. Figures are also well done, though Figs. 2 and 9 should be slightly corrected. The language needs many corrections and significant polishing. Some phrases are unclear. For example, the phrase at the end of first paragraph on Page 7 “The granitoids are mainly composed of Late Triassic-Middle Jurassic syenogranite, alkali-feldspar granite, monzogranite and granodiorite, and the emplacement time of a limited number of local areas was earlier in the Early Paleozoic” is absolutely unclear. The first paragraph of Section 6.1.1 is not readable, needs reformatting. More comments may be found in the attached pdf file.

The authors’ conclusion that the studied rocks are peraluminous I-type granite resulted from partial melting of juvenile lower crust followed by fractional crystallization is solid, but not new. Meanwhile, Fig. 7, which illustrates the discussion on fractionation, does not shows SiO2 values above 80%. If does, correlations of SiO2 with TiO2, P2O5, Rb/Ba, Rb/Sr, Nb and Eu will not be so clear. The latter two are not even shown. The suggested partial melting is not well discussed. The work by Chappel et al. (2012) may help this.

Most of the studied rocks have adakitic signatures, while adakites are commonly associated with Cu-Mo porphyry deposits throughout the world and in NE China particularly (Castillo, 2011). This matter is not discussed.

Section 6.3 “Diagenetic and metallogenic model” is a statement based on the selected literature. No discussion, nothing new.

Section 6.4 “Geodynamic setting” is also trivial, showing that the Chang’anpu monzogranite formed on the active continental margin of the Pacific realm. No possible relation to “the Early Cretaceous giant igneous event” (Wu et al., 2005) is discussed. The illustrating scheme (Fig. 10) shows an ordinary subduction model that does not help to understand why “The molybdenum deposits in China are … different from the late Cretaceos-Oligocene molybdenum deposits in foreign countries” as stated in Introduction.

Overall, this study presents the data that may be of use in future reviews of regional geology and metallogeny as well as for purposes of local geochemical exploration. However, the discussion may be significantly improved. The text needs significant editing and language polishing.

References

Castillo, P.R., 2012. Adakite petrogenesis. Lithos, 135: 304–316.

Chappell, B. W., Bryant, C. J., & Wyborn, D. (2012). Peraluminous I-type granites. Lithos, 153, 142–153.

Wu, F.Y., Lin, J.Q., Wilde, S.A., Zhang, X.O., Yang, J.H., 2005. Nature and significance of the Early Cretaceous giant igneous event in eastern China. Earth and Planetary Science Letters, 233(1-2): 103–119.

Comments for author File: Comments.pdf

Author Response

Dear reviewer:
I am very grateful to your comments for the manuscript. According with your comment and request, we amended the relevant part in manuscript. Here, we attached revised manuscript in the formats of MS word, for your approval.

 

 

Thank you very much.

Sincerely
Yanchen Yang

 

Author Response File: Author Response.doc

Reviewer 3 Report

My main problem with this paper is that the authors completely overlook the fact that most of their samples display very strong adakitic signature: Y = 5.3 - 11.7 ppm, Yb < 1 ppm and Sr/Y = 70-85 for most samples. which requires garnet-bearing metabasaltic source in either downgoing slab or mafic lower crust. This is not surprising at all,  taking into account close association of Cu-Au-Mo porphyry deposits with adakites and adakite-like (high Sr/Y) rocks in both magmatic arcs and orogenic belt. I suggest that the authors take a look at the recent review by Kepezhinskas et al. (2022). Adakites, high-Nb basalts and copper-gold deposits in magmatic arcs and collisional orogens: an overview. Geosciences, v. 12, 29, https://doi.org/10.3390/geosciences12010029. 

I suggest that the authors re-evaluate their data using chemical plots and petrogenetic concepts presented in the paper above as well as the following papers:

Drummond M.S. et al. (1996). Petrogenesis of slab-derived trondhjemite-tonalite-dacite/adakite magmas. Earth Environ. Sci. Trans. R. Soc. Edinburgh, v. 87, p. 205-215.

Defant M.J., Xu J.F. et al. (2002). Adakites: some variations on a theme. Acta Petrologica Sinica, v. 18, p. 129-142.

I would like also to make the following additional remarks:

Paragraph 2 in the Introduction - Most porphyry deposits in both oceanic (e.g. Philippines, Indonesia) and continental (Andes) magmatic arcs as well as accretionary belts of different age are related one way or another to adakitic (high Sr/Y) magmatic rocks. Again, please refer to Kepezhinskas et al. (2022) for the review of various geologic environments of adakite-related porphyry formation. 

Regional setting - numerous Cu-Au-Mo deposits in the Central Asian Orogenic Belt (CAOB) are related to adakite magmatism. Again, Kepezhinskas et al. (2022) contains a comprehensive review, but the authors also might want to consider the following references: 

Shen P. et al. (2018). Large Paleozoic and Mesozoic porphyry deposits in the Central Asian Orogenic Belt: geodynamic settings, magmatic sources, and genetic models. Gondwana Research, v. 58, 161-194.

Cao M.J. et al. (2016). Assessing the magmatic affinity and petrogenesis of granitoids at the giant Aktogai porphyry Cu deposit, Central Kazakhstan. American Journal of Science, v. 316, 614-688.

Zhang L. et al. (2006). The adakite connection of the Tuwu-Yandong copper porphyry belt, eastern Tianshan, NW China: trace element and Sr-Nd-Pb isotope geochemistry. Mineralium Deposita, v. 41, 188-200.

Regional setting, paragraph 2 - for the Lesser Khingan geology, stratigraphy, ages and mineralization please refer to the following papers:

Berdnikov N. et al. (2020). PGE mineralization in andesite explosive breccias associated with the Poperechnoye iron-manganese deposit (Lesser Khingan, Far East Russia): whole-rock geochemical, 190Pt-4He isotopic, and mineralogical evidence. Ore Geology Reviews, v. 118, 3352.

Berdnikov N. et al. (2021). Gold in mineralized volcanic systems in the Lesser Khingan Range (Russian Far East): textural types, composition and possible origins. Geosciences, v. 11(2), 103.

Figure 2 - what are the top layers in Figure 2B? Please define in the legend.

Figure 3 - scale is almost invisible in Figures 3C and 3D.

 

Author Response

Dear reviewer:
I am very grateful to your comments for the manuscript. According with your comment and request, we amended the relevant part in manuscript. Here, we attached revised manuscript in the formats of MS word, for your approval.

 

 

Thank you very much.

Sincerely
Yanchen Yang

 

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

The manuscript has been significantly improved. The authors’ suggestions on the origin of the Jurassic Mo-porphyry ores are much clearer now. However, the compressional tectonism that the authors associate with these ores in contrast to the extensional environment associated with the E. Cretaceous Cu-Au ores is doubtful. Both ore types are related to adakitic intrusions that, as the authors suggested, are a major indicator of compressive conditions. Anyway, the authors’ idea is clearly presented now and has the right to be published.

Some text editing is still necessary. Particularly, some spaces between worlds should be added, especially in the new (highlighted) parts of the MS. Fig. 2 needs ages of the alkali-feldspar granite, monzogranite and plagiogranite shown in the map.

Overall, I recommend publication after a minor editing.

Author Response

Dear Reviewer:

 

Thank you again for your valuable suggestions on the revision of the article.

 

Point 1: Some text editing is still necessary. Particularly, some spaces between worlds should be added, especially in the new (highlighted) parts of the MS. Fig. 2 needs ages of the alkali-feldspar granite, monzogranite and plagiogranite shown in the map.

 

Response 1: Some text editing has already been done, the ages of the alkali-feldspar granite, monzogranite and plagiogranite have been added to the Figure 2.

Author Response File: Author Response.doc

Reviewer 3 Report

The authors did in excellent job in revising their manuscript. This paper is now ready for publication.

Author Response

Thank you again for your valuable suggestions on the revision of the article.