Talk:Metamorphism

Redirects: Etymology:from Gk. metamorphosis "a transforming," and "-ism"; from metamorphoun "to transform," from meta- "change" (see meta-) + morphe "form" (see Morpheus),Metamorphism (geology), Regional metamorphism, Contact metamorphism, Hydrothermal metamorphism, Impact metamorphism

Removed redirect because i intend to write something about this. Muriel Gottrop 15:25, 1 Aug 2003 (UTC)

The concept of metamorphic sequence is missing:


 * pelitic sequence (where the concept of metamorphic zones -chlorite, biotite, garnet, staurolite, kyanite, sillimanite- is usually applied)
 * mafic (or basic) sequence (where the concept of facies is usually applied
 * ultramafic (or ultrabasic) sequence
 * Carbonate sequence
 * Quartzo-feldspathic sequence

Also the term of Barrovian metamorphism for regional metamorphism should be added

Moumine 23:32, 15 Mar 2005 (UTC)

Barrovian metamorpism is only one type of prograde sequence, and it is wrong to class blueschist and eclogite in with it. Also, I will attempt to work on a more thorough definition of metamorphic facies which includes what they are, mineral assemblages, etc. Also, I can't believe that prehnite-pumpellyite facies was missing entirely....oh well. Rolinator 05:52, 24 December 2005 (UTC)

Done Blueschist facies, under Blueschist and Greenschist facies under Greenschist and Amphibolite Facies under Amphibolite. Will also be attempting to bring together the materials science links to put together the whole equilibrium assemblage thing; also the thermomechanical reasons behind metamorphism, and work on rock microstructure metamorphic section as part of this. Rolinator 08:51, 27 December 2005 (UTC)

Dynamic metamorphism
Dynamic metamorphism should not be confusedwith brecciation; the former is a metamorphic event (thermal and textural) and the latter is just a result of faulting. In brittle conditions, you are unlikely to see any change of mineral assemblages, because the rocks are too cool to undergo retrogression. I'll grant that a lot of large fault systems have clay gouges etc, in the upper crustal zones, but most of this is a result of metasomatism not metamorphism.

Dynamothermal metamorphism is also not to be confused with mylonitisation; mylonites are a textural response to ductile deformation, resulting in comunition via grain size reduction and mineral reconfiguration, most often without changing the mineral assemblage. That's not metamorphism, it's shearing. The other problem with confabulating mylonites and dynamothermal metamorphism is that mylonites don't neccessarily get heated up enough above the background because shear dislocation is shared across a very large cross section of he shear zone. In the brittle-ductile transition, however, heat is able to be focused more efficiently into thin fault zones because the confining pressure keeps the hangingwall and footwall pressed together enough to mitigate milling, and the rock isn't ductile enough to deform via pure ductile smearing...so it tends to, in the rare cases, form thick shear bands of pseudotachlyltes and disturbed milled ductile melanges and fault gouges. In these zones the frictional heat is often enough to not only heat the rock up to melt it, but also change the mineral assemblage, hence causing definite metamorphism not just textural reorganisation.Rolinator 04:08, 23 April 2006 (UTC)

we need some diagrams to get towards a B class Graeme Bartlett 06:16, 9 November 2007 (UTC)

The image
The image does nothing but detract from the legitimacy (actual AND factual aspects) of this Encylopedic entry. The symbol used in the image (opposed chevrons with attached tails) is not a chemistry symbol for reaction equations. Sources which incorporate aspects such as using a false symbol in a reaction equation screams that the depiction is not true or at the very least, an entry which should be ignored as it includes information that is not from a reputable source. Wikipedia does NOT have to be in the same reference category as the Urban Dictionary, it does so by choice. The Weasel colors do nothing to communicate the meaning without be labeled as the true colors they depict; that of weasels - Dirtclustit (talk) 21:52, 24 September 2014 (UTC)

External links modified (January 2018)
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image Petrogenetic grid for Metapelites.png
I removed image https://commons.wikimedia.org/wiki/File:Petrogenetic_grid_for_Metapelites.png from the Introduction section of this article because i think it is is much too complicated and unclear. I think viewers will not be able to see the wood for the trees. I think it is a very unsuitable image to be the second image about metamorphism that 99 percent of readers will have seen in their lifetime and I expect it would scare viewers and readers away from this article. The pressure-temperature ranges of metamorphic facies are already shown in the much simpler and clearer image https://commons.wikimedia.org/wiki/File:Metamorphic_Facies.jpg in the Metamorphic facies section of this article.

(I have also removed the image from the Metamorphic rock and Metamorphic facies articles for similar reasons). GeoWriter (talk) 17:10, 26 February 2019 (UTC)


 * While it may be useless for the layman, petrogenetic grids are the bread and butter of metamorphic petrologists, and this petrogenetic grid is one of the best looking ones I've ever seen. It deserves to be easily available for all. Besides, this page really needs to be expanded. There's quite a bit of work to do. Can we compromise and put it closer to the bottom, by the facies or metamorphic processes/reactions? It may look a bit confusing now, but I'm currently in the process of developing a page on petrogenetic grids to explain them.  RockingGeo (talk) 17:46, 26 February 2019 (UTC)

I think the diagram is much worse than "a bit confusing now". I think the diagram is a mass of data - too much for almost everyone, including novices and even some experts. Even if it is accompanied by an explanation, the diagram is so cluttered that I think it is very unlikely to be useful to the average reader/viewer. The creator of the diagram has favoured quantity of data at the expense of clarity of information. It may be one of the most complete available examples of a petrogenetic grid but that does not necessarily make it suitable for a Wikipedia article. Diagrams should bring clarity and improve a reader/viewer's understanding of a subject - this correlates closely with simplicity. Wikipedia editors should not be trying to impress people with an overly-complicated diagram, which looks authoritative and comprehensive but which is also likely to overwhelm and intimidate people. Diagrams should be accurate and useful but they do not have to be impressive or comprehensive. Wikipedia articles do use and should use diagrams to help the reader to understand a concept. Wikipedia articles do not have to include a diagram just because it "deserves to be easily available for all".

Although this diagram contains much interesting data, which could be useful to professional metamorphic petrologists (whom I suspect will account for only a very tiny minority of the people who will ever look at this diagram on Wikipedia), professional metamorphic petrologists are very much more likely to find petrogenetic grids elsewhere e.g. in academic journals. Professional metamorphic petrologists should not use this diagram in their academic research because the diagram's creator did not give sources.

As you are proposing to create an article about petrogenetic grids, I recommend that you describe/explain simple examples with about 3 to 10 mineral P-T stability fields, not the ~150 fields of this diagram. — GeoWriter (talk) 15:37, 28 February 2019 (UTC)


 * Have you ever studied metamorphic petrolgy? I don't mean to insult you, but petrogenetic grids are introduced in the beginning chapters of any good textbook on metamorphism, and they're also as complicated as this or more (much less pretty too). It's impossible to learn about or understand metamorphism without knowing how to read petrogenetic grids (among other basic things that frustratingly aren't yet explained here, like compatibility diagrams.) If you're a geologist, you should easily make sense of this diagram. When I first posted this nice image, I didn't think there would be any problems, especially since a much more complicated image is the first thing on the geology article.


 * This diagram matches all criteria for new encyclopedic content. It is notable, verifiable (While the author didn't cite his sources, I've already found and cited articles that match the content and verify it to be true.), and  "aims to convey the important accumulated knowledge for its subject domain." The fact that a layman cannot figure out what a certain diagram (or any subject matter) means on Wikipedia is no reason to delete it, but it is a perfect reason to explain it and expand the article. In fact, that is what I am currently doing. I welcome and encourage you to help me find simpler petrogenetic grids and explain how and why they are used in metamorphic petrology. I'm wanting to create a small section in this article, and I've already created an article on them: Petrogenetic grid. (I'm not the best geo-writer, after all).


 * That said, I will refrain from posting this amazing image until a sufficient explanation for petrogenetic grids has been created. Deal? RockingGeo (talk) 21:10, 28 February 2019 (UTC)

I think the average Wikipedia reader not understanding the diagram when it had no explanation was a very good reason for removing the image. This situation no longer exists because you subsequently created the petrogenetic grid article on 28 February. Thanks for creating this new article, which provides an explanation of petrogenetic grids that allows readers to at least begin to understand the diagram and concepts. The explanation changes the suitability of the diagram for inclusion in Wikipedia articles. Although I would still prefer that a simpler diagram should be used if created or found in the future, the explanation in the petrogenetic grid article is enough to persuade me to now withdraw my objections about the use of this diagram. — GeoWriter (talk) 16:49, 1 March 2019 (UTC)

Metamorphism versus metamorphic rock
I got looking at these two articles, which overlap quite a lot, and briefly flirted with the idea of proposing a merge. However, I think the topics are sufficiently different to warrant two articles, as long as each article does not try to comprehensively cover both topics.

It seems to me that the typical reader searching for Metamorphic rock wants to know about gneisses, schists, marbles, and so on, and where they are found and what they are good for. A reader searching for Metamorphism -- this is about three or four times less common than a visit to Metamorphic rock -- is probably more technically oriented, wanting to know about regional versus contact metamorphism, metasomatism, and other interesting bits of physics, chemistry and petrology. This doesn't mean that Metamorphic rock doesn't mention these things, but that they are covered briefly, with suitable links. Likewise, Metamorphism will mention metamorphic rock types and their tectonic settings, but briefly, with suitable links.

I'm thinking aloud here. But would appreciate observations on how to better distinguish and define the scopes of the two related articles. --Kent G. Budge (talk) 21:57, 23 February 2021 (UTC)


 * I agree with your assessment of how the two articles should be differentiated. I'll think about details. GeoWriter (talk) 17:18, 26 February 2021 (UTC)