The Geochemical Features and Genesis of Ferromanganese Deposits from Caiwei Guyot, Northwestern Pacific Ocean
Round 1
Reviewer 1 Report
The authors studied the ferromanganese deposits from Caivai Guyot. The main conclusions are drawn by comparing the chemical, mineral, and textural features of two crusts from the mountain edge and nodules from the slope. This is not correct, since crusts and nodules are fundamentally different deposits. Unlike crusts, nodules are affected by the substrate and pore water, which affects their chemical and mineral composition. Nodules always contain more copper than crusts. The authors erroneously attribute this to the influence of ocean currents. This basic error calls into question many of the conclusions made by the authors.
Todorokite was incorrectly identified in the mineral composition of the studied crusts and nodules. It does not occur in hydrogenous crusts; 10A minerals are represented by buserite or asbolane-buserite. The todorokite peak is not visible on presented XRD patterns. Its appearance usually indicates the presence of a hydrothermal source of Fe-Mn oxyhydroxides.
This work includes valuable data on the composition of the ferromanganese deposits of the Caivai Guyot, but no new regularities are described based on this.
The growth rate of nodules was estimated using the Co chronometer. This method is indirect, and is applicable only for crusts; it cannot be used for nodules.
Pearson's coefficients tables can be placed in the supplementary materials.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors collected three ferromanganese deposits from the Caiwei Guyot in the Magellan seamount chain and investigated them in detail. Although their mineralogical and geochemical approaches are conventional, the data are useful to publish. My main concern is Section 5.3. The authors concluded that deeper ferromanganese deposits have higher Cu contents, reflecting dissolved Cu variation in water column. This logic is not convincing considering small number of the samples. The authors refer two papers (Josso et al., 2021; Hein et al., 2012) as examples showing same phenomena. However, Cu enrichments in ferromanganese crusts in the Northwest Pacific was not attributed to dissolved Cu profile in water column, rather to diagenetic input. In addition, ferromanganese crusts from 1000 to 3000 m water depth on Takuyo-Daigo seamount in the Northwest Pacific did not show Cu increase trend with depth (Usui et al., 2017). More careful discussion is needed for this section. Another my propose is combining of sections 5.4. and 5.5. The authors should illustrate that paleoceanic history reconstructed from shallow and deep ferromanganese deposits is consistent. Schematic diagram showing changes in oceanic conditions is also helpful for reader's understanding. After minor revisions addressing above suggestions, I think this manuscript would be ready to proceed publication processes.
[specific comments]
L570: hydrogenetice -> hydrogenetic
L658: decline -> decline.
L726-727: The meaning of this sentence is unclear. The chemistry of pore water in the past might be different from recent.
L730-731: This sentence is tricky. Be simple.
L756: ferromanganese -> Ferromanganese
L783: stage II -> stage II.
Fig 2e: Illustrate layers 1 to 5 in the cross section of C9.
Table 2: Add unit % to major elements.
Table 3: Add unit % and ppm to major and trace elements, respectively.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors, thank you for editing the manuscript.
Dear authors, thank you for editing the manuscript.
The article may be published in present form.
There is a note about factor analysis. REY are usually included in the group of iron and (or) manganese, but not aluminosilicates. Please check or give an explanation.
