Talk:Subduction zone metamorphism

Review by Jiawei Zuo

General

This article is informative. Though some minor format issues needs to be corrected, it provides a view to the metamorphic facies change during the subduction process. I think the author can add the information of the density of subducted crust after each facies change (Like eclogite facies change could be a driving force of subduction).

Images

Tags showing different mineral compositions of rock samples can be added.

Format

I think the "reference" can be a main title. Just use ("==Reference==")/

• In this article, some Celsius Degrees are "C"s rather than °C. Fix it.
• H2O rather than H₂O. Use the subscript tool while editing (Advanced → Subscript).

MichaelZuo (talk) 01:00, 14 October 2014 (UTC)

Review by Andrew Webb

Overall, great article. It's a nice compilation of data about a specific type of metamorphism, which is very useful for practical applications. I have some improvements on the article below, followed by some potential ideas for adding to it for the final version.

Improvements

I found there actually is a page for the Prehnite-pumpellyite facies, so you can use that in the first section, since it is not linked. I don't think the subsection titles need a semicolon at the end. The references section can be a section header, like Jaiwei said.

I only found one typos, in the Zeolite facies section: "Zeolite facies conditions typically only affect pelitic sediments undergoing burial, but it is commonly produces zeolite minerals within the vesicles of vesicular basalt."

And Jaiwei mentioned the missing degree symbols for some of the temperatures, and how to make the subscript 2 in H2O (you type H₂O to display H₂O).

Is there a format for including formulae into Wikipedia? Maybe like centering the formula in under the paragraph, like you would a quote, or putting it in a box to separate it from the text. Just an idea to make it easier to pick out the formula from the body of the article.

Ideas

I think the article could be expanded a little (just some ideas, not necessary to do these):

You go into detail about hydrous minerals and that they can be created and destroyed during subduction. I would suggest adding a section about the influence of water to metamorphism. You could discuss how melting of hydrous minerals releases water and could increase the rate of metamorphism or could change the chemical composition of a system. I see that you include how the release of water can initiate melting, but maybe you could discuss how this happens? You could even go a bit further and add a section about the factors that contribute to metamorphism (temp, pressure, and fluids) and discuss each in more detail.

Another idea is to talk about the implications of these facies. For example, it's kind of inferred from the article (and the fact that we are geologists), but you could just straight up say that the minerals present can be used to determine the pressure and temperature conditions that the subducting plate is experiencing. A more specific example would be how the transition of a rock from blueschist to eclogite facies can affect the subduction rate because its density is so high (Jaiwei totally beat me to this one). Stuff like that.

Also, could you possibly get pictures of zeolite and P-P facies rocks? The 3 sample pictures you have are awesome, I'd like to see some for the other two if it's possible.

Awebb6 (talk) 02:56, 14 October 2014 (UTC)

Minor issue fixed (HTML _... syntax shown properly with <nowiki>...</nowiki> tag).

Yes, you can add more sophisticated formatting with <math>...</math> tags, which are primarily user for mathematic equations and symbols, but they use LaTeX, so they allow chemical equations, too. --CiaPan (talk) 11:18, 20 October 2014 (UTC)

Comments from Graeme Bartlett

• In each of the facies sections describe in words the temperature and pressure conditions for its formation and presence. It can also include the depth in the earth for this.
• Is there anything to say about carbonates/carbon dioxide as a volatile in these conditions? As Michael's sandbox made mention of CO₂ release.
• Are there differences between slabs subducting at different rates? Or differences when subducting under continents or other ocean floor?
• How long do these changes in facies take? (If slow then there may be lag if slab sinking is fast).
• Is there a way to quantify the water activity, eg pressure of water, % of water? Does this make any difference or is water always present to the maximum extent anyway?
• How do rocks from these subduction zones end up at the surface where people can see them? Does the metamorphism reverse when the rock comes back up?
• You use the term Protolith in a heading but it is not use in the text, so perhaps you could use a simpler term, or explain it in the paragraph.
• For Inside the Subduction Factory: Thermal Structure and Metamorphic Evolution of Subducting Slabs I am not sure what this is, is it a book or a chapter in a book or an article? A url or isbn or DOI would be good.
• Perhaps a graph showing stability ranges of the minerals could be good too.

Review by Martial Morrison

General

Great article Elly! The main thing that sticks out to me about your article, particularly the last few sections, is that uses many geologic terms. Blueschist facies, amphibole, glaucophane, phyllosilicates, plagioclase...these are just a few of the examples that I'm referring to. As I read through your article, I feel like it's pretty intimidating. I'm more of the geophysicist, so possibly it's just that I don't have the necessary background to digest the article as a whole, at the moment. The thing is, I feel like the average high school student probably also wouldn't have the background. I'm not sure if there's anything that you can do about this aside from blue-linking the terms; the thing is, there are lots of those terms to read through to get a proper background. Maybe you could include a really generic paragraph that gives a bit of background on all the terms. It doesn't have to be specific; maybe just something like "all these different minerals are formed in subduction zones".

Specifics

In the first paragraph, "creates and destroys" should be "create and destroy". In the first paragraph, "Understanding the timing and conditions in which these dehydration reactions occur, is key to interpreting mantle melting and the subsequent volcanic arc magmatism." has an awkward phrasing. I would say either remove the comma, or flip-flop the sentence (aka: "The key to interpreting mantle melting is....") In the Oceanic Crust section, words like "ultramafic" may be too complex for high school students, who don't have geology courses. If there a way to link words like that?

In the "Hydrous minerals of a subducting slab" section, you've blue-linked "ultramafic rocks". Instead of blue-linking it here, link it in the "Oceanic Crust" section, where you first use the term.

References

I think the reference section could use just a few more. It's good to be safe!

Mmorr42 (talk) 22:54, 15 November 2014 (UTC)

Matt O'Leary review

Hey Elly! Loved the article, and I don't think I can add much that already hasn't been said after reading the reviews from our peers. However, I will have to agree with Martial. I did find it harder to digest the numerous facies you detail, but I'm not sure how else you can explain it without losing the information behind the terms. Your diagrams are large and understandable. Make sure to bracket terms related to Wikipedia the first time they appear. You could also " * " your mineral formulas: "Tremolite + Chlorite + Albite = Glaucophane + Lawsonite" to make them stand out a little more. Maybe a small explanation of what those mean too. Overall, everything looks great -- keep up the good work!