Geochemical Insights from Clinopyroxene Phenocrysts into the Magma Evolution of an Alkaline Magmatic System from the Sanshui Basin, South China

Round 1

Reviewer 1 Report

Comments:

Article: Geochemical insights from clinopyroxene phenocrysts into the magma evolution of an alkaline magmatic system from the Sanshui Basin, South China is well written according to the templates indicated by Minerals. The article makes an essential contribution to the description of the petrogenetic processes in Sanshui Basin, South China based on the petrographic and mineralogical study with special regard to clinopyroxenes.

The abstract is summative and indicates the summary of the result. The objectives of the article are clearly presented in the introduction. Geological setting is described in detail and gives a good picture of the studied area.

Analytical methods are appropriate for the study of clinopyroxene phenocrysts. For major elements the authors used electronic microprobes (EMPA) -1600 Su-104 probes. For and REEs they used Bruker M90 ICP-112 MS and LA -ICP-MS.

The mineralogy chapter describes the main types of basalt clinopyroxenes, trachyandesite and comenditic trachyte. 9 types of clinopyroxenes were separated based on optical characteristics, major elements and REEs.

The authors identified that clinopyroxenes type B1, B2, and T2 are in equilibrium with magma in a closed system. Green core type B3 clinopyroxenes and multiple zoning type B4 clinopyroxenes are crystallized in the open system during magma evolution. Clinopyroxenes type A1 and T1 indicate magma mixing. Based on the analytical data, temperature and pressure calculations and thermobarometric calculations were performed.

Based on the composition of clinopyroxene in the rocks of Sanshui Basin, South China and the thermobaric data, the authors made a schematic model of the magmatic processes. The authors separated for the first time for this area 4 stages of magma evolution. Thermobaric calculations performed by the author indicate that basaltic magma reservoir is distributed in the lithospheric mantle (~ 40 km) to upper crust (~ 10 km), and comenditic trachyte reservoir is distributed in the upper crust (5 - 10 km).

Suggestions:

1. The 4.1. Characteristics of petrography (p. 4) should have presented a classification of rocks on a mineralogical or chemical basis.
2. In Figure 4. Clinopyroxene compositions plotted into the ternary (line 179), please explain the significance of the abbreviations in the figure: Wo, En, Fs, Aeg, Di, Hd.

Author Response

We appreciate your positive evaluation of our study and your suggestion for us to improve the manuscript.

Response to Reviewer 1 Comments

     1. The 4.1. Characteristics of petrography (p. 4) should have presented a classification of rocks on a mineralogical or chemical basis.

Response 1: Thank you for this suggestion. The geochemical compositions were listed in Table.1S. We added the lithology description in Table.1S.

     2. In Figure 4. Clinopyroxene compositions plotted into the ternary (line 179), please explain the significance of the abbreviations in the figure: Wo, En, Fs, Aeg, Di, Hd.

Response 2: Thank you for the careful checking. We added the description for these abbreviations below the Fig.4 and line 165 in manuscript.

Reviewer 2 Report

The experimental construct presented by the authors is reasonably sound. It cannot work out if there is a widely accepted model for the bimodality of the lavas and volcanic rocks in the Sanshui basin, and therefore this is a good locality to test the applicability of pyroxene geochemistry, or, if the pyroxene composition/geochemistry is being used to test models for the origins of the bimodal volcanic product.

The experimental design is sound and reasonably well developed. However, there is a population of clynopyroxene that is invoked by the authors (B4), which is never described or analysed. This must be addressed - do you have data for these minerals or not? If no data was collected in this study, then the inclusion of the data into this study must be better demonstrated.

The quality of written language varies. Some sections are not bad, others require a lot of work. I have done my best to make some recommendations, particularly in the earlier parts of the manuscript, but additional input is required.

There are several sections of data presentation, or outcomes of calculation that are monotonous and repetitive and can be shortened and/or consolidated, or presented using an alternative medium - e.g. a table or figure. There is also some superfluous text in the Discussion and I think with some careful consideration it may be possible to shorten the manuscript by 2-3 pages (at least).

Otherwise, this is a study that is reasonably sound, from a scientific and execution perspective. Just needs some shaping of its presentation. See feedback in annotated PDF for more information.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx