The Ultramicrochemical Analyses (UMCA) of Fluid Inclusions in Halite and Experimental Research to Improve the Accuracy of Measurement

Round 1

Reviewer 1 Report

Review of Galamay et al. “The ultramicrochemical analyses (UMCA) of fluid inclusions in halite, and determining the accuracy of a measurement”

 

The manuscript by Galamay et al. presents an upgraded approach to analyzing selected components of fluid inclusions hosted within halite by ultramicrochemical analyses (UMCA) as a means to the chemical composition of ancient seawater. The ions analyzed by the authors are K⁺, Mg⁺⁺, Ca⁺⁺ and sulphate. The authors describe in detail how the aqueous component of halite-hosted fluid inclusions is removed using tapered capillary tubes and the reagents used to precipitate species for analysis. Results are presented that provide improved detection for the selected species in addition to improved reproducibility.

 

Broad Comments:

The goals of the authors are definitely worthy of investigation and an upgraded approach will strengthen research into ancient seawater studies. The manuscript is written in good quality English and the manuscript is well structured with sections clearly presented. The methodology is satisfactorily described with some minor points that need addressing; these are raised below. The references are thorough and up to date.

There are some overall points that need addressing. I searched to see whether the errors were 1-sigma, 2-sigma or 3-sigma and this is not mentioned. The authors need to be clear about this because the reader needs to understand whether the analyses are at the detection limit or not. As I read it, the error could be 1-sigma and the analysis reported at the same value which would make their analysis meaningless. I suggest that the authors read Henry Longerich’s paper from 1996 to understand errors and their reporting. One point that was glaringly missing is the topic of blanks. In order for the authors to be rigorous and convincing, they need to examine blanks. There are two possible ways to evaluate blanks, they being 1) using quartz-hosted standards, or 2) precipitating halite from ultra-pure NaCl in the laboratory. Without analysis of blanks, this analytical method lacks rigor. Both the blanks and errors (in terms of sigma) should be addressed prior to acceptance.

 

Specific Comments:

It is worth mentioning that chevrons can also have trapped bubbles as I have seen this in some primary halite.

Line 76: A word is missing. I suggest changing the text to “makes it difficult to accurately determine their origin”.

Lines 86-87: Good observation.

Line 136: The authors say “immediately”. Could they give an estimate in seconds?

Line 140: How are the ends sealed? Can the authors prevent contamination during sealing?

Line 252: The authors give errors in this table but how many sigma are the errors?

Table 2: For the Laminated Green Salt, I see that some analyses have commas. I assume that the authors meant to type 12.7 instead of 12,7? In addition, the errors in this table are sometimes larger than the analyses. Again, it is important to state how many sigma are involved. It suggests that analyses are at the detection limit but the authors need to be clear.

How do the authors handle a situation when a daughter crystal is entrained within a fluid inclusion?

How does this change interpretation of the original seawater chemistry?

 

This manuscript will be valuable to the scientific community once revised.

 

Author Response

Thank you for your review. Some of the comments of the Reviewer were taken into account, which certainly improved the text.

We answer the Reviewer's general comments were on the statistical analysis (sigma values) and blank analyzes in the enclosed Word file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have modified the technique of microchemical analysis of fluid from fluid inclusions in the gallite.  Having studied natural samples of halite by means of the modified technique, they evaluated the accuracy of single analysis and showed that the modified technique is suitable for studying the composition of fluids in the natural halite. Fine work that may be of interest to other researchers.

The manuscript is well deserved to be published.

Author Response

Thank you for your review.

Round 2

Reviewer 1 Report

Following the edits made by the authors, I recommend this manuscript for publication.

Author Response

Thank you for your constructive comments on our manuscript.

Author Response File: Author Response.docx