the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Jun 2024
Influence of water on crystallographic preferred orientation patterns in a naturally-deformed quartzite
Abstract. Laboratory experiments demonstrate that intragranular water exerts an important control on deformation within quartz, causing weakening and promoting plasticity. The role of water on natural quartz deformation, however, remains unclear, as recent studies find an inverse relationship between water content and the magnitude of plastic strain. Furthermore, little work has investigated the effects, if any, of water on the relative activity of various slip systems in quartz. We focus on a naturally-strained quartzite from the Antietam Formation of the Blue Ridge in Virginia, USA. Quartz water content ranges from <50 to >2000 ppm H2O. Water content and crystallographic data were correlated for 968 grains, enabling us to explore the relationship between water content and quartz crystallographic preferred orientation (CPO) patterns. “Dry” (<150 ppm H2O) and “wet” (>500 ppm H2O) subsets show distinct CPOs; c-axes of dry grains define a cross-girdle oriented perpendicular to the extension direction (X), whereas c-axes of wet grains are concentrated along the perimeter of the pole figure. All water content subsets show grains clustered near the direction of maximum shortening (Z), consistent with activity of the basal ˂a˃ slip system. The cross girdle in the driest grains suggests activity of prism ˂a˃ and possibly rhomb ˂a˃, whereas the orientation of the wettest grains implies a contribution from prism ˂c˃ slip. These slip system interpretations are supported by analyses of intragranular misorientations. These results indicate that water content impacts the relative activity of various slip systems in natural quartz, potentially affecting application of the quartz opening angle thermometry.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(9346 KB) - Metadata XML
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Supplement
(1133 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-1567', James Gilgannon, 01 Jul 2024
Please find my review in the attached PDF. The paper is excellent and I only have some minor comments. The only thing that might require some larger adjustment of the paper relates to my comment on figure 4.
Best,
James Gilgannon
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AC2: 'Reply on RC1', Jeffrey Rahl, 24 Jul 2024
Dear Dr. Gilgannon,
We appreciate the time you have taken to assess our manuscript and provide constructive feedback.
We have improved the manuscript in response to your specific comments, as detailed below.
Thank you,
Jeffrey Rahl (on behalf of all authors)
Reviewer comments and responses:
- Figure 1 - I think that an overview image that shows the overall quartzite microstructure would be of benefit to give the reader a sense of what kind of rock they are looking at. I read Singleton et al. (2020) so I have a rough idea but I think it would be better to see the specific rock microstructure you are analysing and discussing alongside the other detailed panels you present.
This request was made by both reviewers; we have added a figure to illustrate the microstructure.
- Figure 4 - I think that the colour coded figure in D should come first as it sets the key for all of the other plots. I also wasn’t sure of how you got your slip system label for grains in this figure: does it come from pole figure fibre analysis (cf. Kilian and Heilbronner 2017 [doi:10.5194/se-8-1095-2017]) or your misorientation axes analysis? From how the text is written in section 5.1 it seems that the slip system labels in figure 4 are based on the IPF from figure 5. I wasn’t sure if I had misunderstood this. If I haven’t then I think you will need to change the order of the text to introduce the misorientation axes method results before figure 4.
Thank you for this comment. We had structured the paper with the idea that the misorientation analysis was not a result but rather a subsequent analysis, but we agree it is confusing and probably inappropriate to include interpretations in a figure that are not explained until a later figure. To address this, we moved the text explaining this analysis into the Methods section (which does seem appropriate) and text describing these results from the Discussion section into the Results section. We feel this will make the manuscript more intelligible.
- Supplement. As it is, the supplement is unusable. I think you should provide the tabulated data in csv or excel files. PDF is the wrong format for that data.
We have made an Excel file with the data available on the Zenodo database, as well as a new animation showing the impact of water content on quartz CPO.
- Specific comments. Line 75: In the methods I would state how you calculated the ODFs: did you use a constant halfwidth or did you optimise between subsets?
The pole figures shown are based on contouring the orientation data, rather than being constructed from an ODF. This is noted in the text. However, we did construct ODFs for the a-axes opening angle analysis and added text noting this in our description of the opening angle analysis.
- Line 147: “This framework implies that that the drier grains…” feels like the wrong phrasing. It took me a while to clearly understand the sentence. I think you mean the framework of interpreting pole figures? What about something like: “Plotting our data in pole figures with a strain axes reference frame implies that…
Thanks for the helpful suggestion, an improvement we have adopted.
Citation: https://doi.org/10.5194/egusphere-2024-1567-AC2
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AC2: 'Reply on RC1', Jeffrey Rahl, 24 Jul 2024
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RC2: 'Comment on egusphere-2024-1567', Florian Fusseis, 13 Jul 2024
Review
Rahl et al. Influence of water on crystallographic preferred orientation patters in a naturally-deformed quartzite
The authors present a combination of EBSD and FTIR measurements from a statistical set of quartz grains from a deformed quartzite from the Blue Ridge Anticlinorium in Virginia, USA. They find a correlation between water content and crystallographic orientation of the grains, which suggests that water content controls the activation of a specific slip system and thus challenges established assumptions concerning the controls on the emergence of crystallographic preferred orientations of quartz grains.
This is a well-written and -illustrated manuscript that reports relevant observations that contribute to a small chorus of studies that challenge established assumptions about the controls on crystallographic preferred orientations. The paper was originally written for publication in Geology, with the corresponding restrictions on word count and figure numbers. I would recommend this paper for publication in SE, pending some minor amendments:
- Provide a figure that shows the microstructure and establishes context.
- Figure caption of Fig. 1 refers to a panel G which doesn’t exist. The statement “almost all grains exhibit…” is misleading, as only the grains in Fig. 1D-F show deformation lamellae, and in E and F these are practically not visible. Consider correcting the white balance on these photomicrographs?
- Provide details on how exactly the opening angle of the a-axis girdle was measured.
- How many datapoints have been contoured in Figs. 5b-d?
- Provide adequate and usable supplements with the necessary commenting.
Citation: https://doi.org/10.5194/egusphere-2024-1567-RC2 -
AC1: 'Reply on RC2', Jeffrey Rahl, 24 Jul 2024
Dear Dr. Fusseis,
We appreciate the time you have taken to assess our manuscript and provide constructive feedback.
We have improved the manuscript in response to your specific comments, as detailed below.
Thank you,
Jeffrey Rahl (on behalf of all authors)
Specific comments and responses
- Provide a figure that shows the microstructure and establishes context.
This request was made by both reviewers; we have added a figure to illustrate the microstructure.
- Figure caption of Fig. 1 refers to a panel G which doesn’t exist. The statement “almost all grains exhibit…” is misleading, as only the grains in Fig. 1D-F show deformation lamellae, and in E and F these are practically not visible. Consider correcting the white balance on these photomicrographs?
The erroneous reference to the wrong panel has been corrected. We have adjusted the text you highlight so it is not as misleading. Additionally, we have tinkered with the image properties (including the white balance) to try and better draw out these features.
- Provide details on how exactly the opening angle of the a-axis girdle was measured.
Text more clearly defining what is meant by an “a-axis opening angle” has been added.
- How many datapoints have been contoured in Figs. 5b-d?
These numbers have been added to the figure.
- Provide adequate and usable supplements with the necessary commenting.
We have made an Excel file with the data available on the Zenodo database, as well as a new animation showing the impact of water content on quartz CPO.
Citation: https://doi.org/10.5194/egusphere-2024-1567-AC1
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-1567', James Gilgannon, 01 Jul 2024
Please find my review in the attached PDF. The paper is excellent and I only have some minor comments. The only thing that might require some larger adjustment of the paper relates to my comment on figure 4.
Best,
James Gilgannon
-
AC2: 'Reply on RC1', Jeffrey Rahl, 24 Jul 2024
Dear Dr. Gilgannon,
We appreciate the time you have taken to assess our manuscript and provide constructive feedback.
We have improved the manuscript in response to your specific comments, as detailed below.
Thank you,
Jeffrey Rahl (on behalf of all authors)
Reviewer comments and responses:
- Figure 1 - I think that an overview image that shows the overall quartzite microstructure would be of benefit to give the reader a sense of what kind of rock they are looking at. I read Singleton et al. (2020) so I have a rough idea but I think it would be better to see the specific rock microstructure you are analysing and discussing alongside the other detailed panels you present.
This request was made by both reviewers; we have added a figure to illustrate the microstructure.
- Figure 4 - I think that the colour coded figure in D should come first as it sets the key for all of the other plots. I also wasn’t sure of how you got your slip system label for grains in this figure: does it come from pole figure fibre analysis (cf. Kilian and Heilbronner 2017 [doi:10.5194/se-8-1095-2017]) or your misorientation axes analysis? From how the text is written in section 5.1 it seems that the slip system labels in figure 4 are based on the IPF from figure 5. I wasn’t sure if I had misunderstood this. If I haven’t then I think you will need to change the order of the text to introduce the misorientation axes method results before figure 4.
Thank you for this comment. We had structured the paper with the idea that the misorientation analysis was not a result but rather a subsequent analysis, but we agree it is confusing and probably inappropriate to include interpretations in a figure that are not explained until a later figure. To address this, we moved the text explaining this analysis into the Methods section (which does seem appropriate) and text describing these results from the Discussion section into the Results section. We feel this will make the manuscript more intelligible.
- Supplement. As it is, the supplement is unusable. I think you should provide the tabulated data in csv or excel files. PDF is the wrong format for that data.
We have made an Excel file with the data available on the Zenodo database, as well as a new animation showing the impact of water content on quartz CPO.
- Specific comments. Line 75: In the methods I would state how you calculated the ODFs: did you use a constant halfwidth or did you optimise between subsets?
The pole figures shown are based on contouring the orientation data, rather than being constructed from an ODF. This is noted in the text. However, we did construct ODFs for the a-axes opening angle analysis and added text noting this in our description of the opening angle analysis.
- Line 147: “This framework implies that that the drier grains…” feels like the wrong phrasing. It took me a while to clearly understand the sentence. I think you mean the framework of interpreting pole figures? What about something like: “Plotting our data in pole figures with a strain axes reference frame implies that…
Thanks for the helpful suggestion, an improvement we have adopted.
Citation: https://doi.org/10.5194/egusphere-2024-1567-AC2
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AC2: 'Reply on RC1', Jeffrey Rahl, 24 Jul 2024
-
RC2: 'Comment on egusphere-2024-1567', Florian Fusseis, 13 Jul 2024
Review
Rahl et al. Influence of water on crystallographic preferred orientation patters in a naturally-deformed quartzite
The authors present a combination of EBSD and FTIR measurements from a statistical set of quartz grains from a deformed quartzite from the Blue Ridge Anticlinorium in Virginia, USA. They find a correlation between water content and crystallographic orientation of the grains, which suggests that water content controls the activation of a specific slip system and thus challenges established assumptions concerning the controls on the emergence of crystallographic preferred orientations of quartz grains.
This is a well-written and -illustrated manuscript that reports relevant observations that contribute to a small chorus of studies that challenge established assumptions about the controls on crystallographic preferred orientations. The paper was originally written for publication in Geology, with the corresponding restrictions on word count and figure numbers. I would recommend this paper for publication in SE, pending some minor amendments:
- Provide a figure that shows the microstructure and establishes context.
- Figure caption of Fig. 1 refers to a panel G which doesn’t exist. The statement “almost all grains exhibit…” is misleading, as only the grains in Fig. 1D-F show deformation lamellae, and in E and F these are practically not visible. Consider correcting the white balance on these photomicrographs?
- Provide details on how exactly the opening angle of the a-axis girdle was measured.
- How many datapoints have been contoured in Figs. 5b-d?
- Provide adequate and usable supplements with the necessary commenting.
Citation: https://doi.org/10.5194/egusphere-2024-1567-RC2 -
AC1: 'Reply on RC2', Jeffrey Rahl, 24 Jul 2024
Dear Dr. Fusseis,
We appreciate the time you have taken to assess our manuscript and provide constructive feedback.
We have improved the manuscript in response to your specific comments, as detailed below.
Thank you,
Jeffrey Rahl (on behalf of all authors)
Specific comments and responses
- Provide a figure that shows the microstructure and establishes context.
This request was made by both reviewers; we have added a figure to illustrate the microstructure.
- Figure caption of Fig. 1 refers to a panel G which doesn’t exist. The statement “almost all grains exhibit…” is misleading, as only the grains in Fig. 1D-F show deformation lamellae, and in E and F these are practically not visible. Consider correcting the white balance on these photomicrographs?
The erroneous reference to the wrong panel has been corrected. We have adjusted the text you highlight so it is not as misleading. Additionally, we have tinkered with the image properties (including the white balance) to try and better draw out these features.
- Provide details on how exactly the opening angle of the a-axis girdle was measured.
Text more clearly defining what is meant by an “a-axis opening angle” has been added.
- How many datapoints have been contoured in Figs. 5b-d?
These numbers have been added to the figure.
- Provide adequate and usable supplements with the necessary commenting.
We have made an Excel file with the data available on the Zenodo database, as well as a new animation showing the impact of water content on quartz CPO.
Citation: https://doi.org/10.5194/egusphere-2024-1567-AC1
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Cited
1 citations as recorded by crossref.
Brendan Moehringer
Kenneth S. Befus
John S. Singleton
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(9346 KB) - Metadata XML
-
Supplement
(1133 KB) - BibTeX
- EndNote
- Final revised paper