Rapid Exploration Using pXRF Combined with Geological Connotation Method (GCM): A Case Study of the Nuocang Cu Polymetallic District, Tibet
, Song Wu 1,*, Zezhang Yu 2, Yu Liu 2, Jianbing Li 2, Lei Zheng 3, Hao Chen 1, Xiaoxia Li 4 and Gongwen Shi 4
Round 1
Reviewer 1 Report
3.2. QA/QC
3.2.1. Accuracy and Precision
The CCRMP (Canadian certified reference materials project) soil reference material
TILL-4, CCRMP was used for checking the accuracy and precision. But how the calibration of the instrument was performed is not clear.
The following related recent review may be cited at an appropriate place in the text for completeness
Balaram, V.; Sawant, S.S. Indicator Minerals, Pathfinder Elements, and Portable Analytical Instruments in Mineral Exploration Studies. Minerals 2022, 12, 394. https://doi.org/10.3390/min12040394
Author Response
Response to Reviewer 1 Comments
Point 1: TILL-4, CCRMP was used for checking the accuracy and precision. But how the calibration of the instrument was performed is not clear.
Response 1: We have added some details about calibrating the pXRF before testing and drawn the calibration curve (3.2.1. Accuracy and Precision on page 5). Thank you for your detailed guidance.
Point 2: The following related recent review may be cited at an appropriate place in the text for completeness: Balaram, V.; Sawant, S.S. Indicator Minerals, Pathfinder Elements, and Portable Analytical Instruments in Mineral Exploration Studies. Minerals 2022, 12, 394. https://doi.org/10.3390/min12040394
Response 2: This review introduces the principles and application areas of various types of portable analytical instruments, which is a great inspiration for our future work methods. We have read this review carefully and supplemented the manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper presents a method for determining the presence of certain minerals by combining the use of pXRF and GCM. It establishes the necessity of a portable, fast technique due to “in field” conditions, it could be of interest as a combined method for providing fast accurate results on prospection of minerals for a particular region.
I recommend the following issues to be addressed prior to publication:
1.
pXRF. Instrument principle.
An important factor in the XRF method is the system response to different photon energies, which in turn correspond with different elements. It is commonly affected by conditions such as distance from the detector to the sample, detector efficiency, solid angle, presence of different material windows. Most of these parameters are usually fixed in a portable device, therefore one can forget about them, but I consider important at least to mention how the system is calibrated, and how to take into account some of such parameters, being of paramount importance the response of the detector, commonly known as efficiency. This could help in turn to establish a proper limit of detection on the elements of interest as well as to correctly estimate the amount of a given element.
2.
Figure 6. Three-dimensional score plot of principal components for different formations. The plot is hard to read. Consider adding (or even replacing the plot by) a couple of projection over different axes of the plot (e.g. plot PC2 vs PC1; PC3 vs. PC2)
3.
Multivariable analysis is a powerful tool, usually provides a way to distinguish features that other way could remain hidden. Together with ternary plots it commonly provides a way of clustering data, thus allowing to clearly determine different mineral phases, or as in this paper the denudation degree. However, Figure 7 could be misread since it seems that only basalt formation is generating a cluster, while all the other data sets seem to be scattered all over the plot. Does this figure really provide essential information? Could be better some kind of “density plot” in order to provide an easier way to read the information?
4.
Page 8. Last paragraph. “According to the inflection point of the scree plot (Figure 6c),” do you mean Figure 6a?
5.
Consider bringing together figures 9 and 10, it could be easier for the reader to confront the information. Also consider drawing the gray level curves from figure 9 into figure 10.
Author Response
Response to Reviewer 2 Comments
Point 1: An important factor in the XRF method is the system response to different photon energies, which in turn correspond with different elements. It is commonly affected by conditions such as distance from the detector to the sample, detector efficiency, solid angle, presence of different material windows. Most of these parameters are usually fixed in a portable device, therefore one can forget about them, but I consider important at least to mention how the system is calibrated, and how to take into account some of such parameters, being of paramount importance the response of the detector, commonly known as efficiency. This could help in turn to establish a proper limit of detection on the elements of interest as well as to correctly estimate the amount of a given element.
Response 1: We have added some details about calibrating the pXRF before testing and drawn the calibration curve (3.2.1. Accuracy and Precision on page 5). Thank you for your detailed guidance.
Point 2: Figure 6. Three-dimensional score plot of principal components for different formations. The plot is hard to read. Consider adding (or even replacing the plot by) a couple of projection over different axes of the plot (e.g. plot PC2 vs PC1; PC3 vs. PC2).
Response 2: We have added two sets of projections to make the figure easier to read.
Point 3: Multivariable analysis is a powerful tool, usually provides a way to distinguish features that other way could remain hidden. Together with ternary plots it commonly provides a way of clustering data, thus allowing to clearly determine different mineral phases, or as in this paper the denudation degree. However, Figure 7 could be misread since it seems that only basalt formation is generating a cluster, while all the other data sets seem to be scattered all over the plot. Does this figure really provide essential information? Could be better some kind of “density plot” in order to provide an easier way to read the information?
Response 3: We have switched to different colors to distinguish the tuff formation soil samples on the north and south slopes of the mountain. As can be seen from the figure, in the same case of anomalies, the anomalies on the north slope are closer to the sub-ore halo. But making density plots is indeed a more intuitive and easier way to read. There are many density maps in this manuscript, so we request to correct the ternary plots instead of replacing them.
Point 4: Page 8. Last paragraph. “According to the inflection point of the scree plot (Figure 6c),” do you mean Figure 6a?
Response 4: We have corrected the figure number. Thank you very much for your careful correction, you saved us a great deal of embarrassment!
Point 5: Consider bringing together figures 9 and 10, it could be easier for the reader to confront the information. Also consider drawing the gray level curves from figure 9 into figure 10.
Response 5: We have brought together these two figures and added grids and coordinates for easier reading.
Author Response File: Author Response.docx
Reviewer 3 Report
Let me congratulate the authors for their work. A pXRF instrument is used to make prospection in an area of copper sulphur deposits. The paper has a good introduction, beautiful figures and a concise and clear writing.
Regarding the scientific analysis, my understanding is, summarizing, that the way to check the goodness of the measures obtained by the pXRF instrument is by comparing the anomalies map of the figure 9 (calculated according to the GCM method) against the instrument results as they appear in figure 10. Although authors show that "the position with the highest metallogenic intensity is also the position with the most prominent anomaly" i would like to see some sort of grid in both graphics that allows the reader to check by himself this assertion. Global coordinates are not needed, if authors want to maintain some sort of secrecy in the deposit location, but at least a local grid, the same in both figures 9 and 10, is mandatory, in my view.
Author Response
Response to Reviewer 3 Comments
Point 1: Regarding the scientific analysis, my understanding is, summarizing, that the way to check the goodness of the measures obtained by the pXRF instrument is by comparing the anomalies map of the figure 9 (calculated according to the GCM method) against the instrument results as they appear in figure 10. Although authors show that "the position with the highest metallogenic intensity is also the position with the most prominent anomaly" i would like to see some sort of grid in both graphics that allows the reader to check by himself this assertion. Global coordinates are not needed, if authors want to maintain some sort of secrecy in the deposit location, but at least a local grid, the same in both figures 9 and 10, is mandatory, in my view.
Response 1: We have brought together these two figures and added grids and coordinates to each figure for easier comparison. Thank you very much for your guidance, which has greatly improved the accuracy and legibility of the figures.
Author Response File: Author Response.docx
