Talk:Eclogite

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I would be pleased to add a picture of an eclogite sculpture, but i do not know how to proceed.

Wiki Education Foundation-supported course assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 23 August 2021 and 10 December 2021. Further details are available on the course page. Student editor(s): Catherinepeshek. Peer reviewers: KRose4, Zanvit, Hamsquirrel.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 20:02, 16 January 2022 (UTC)

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Eclogite is not an igneous rock. I removed that category. Siim 20:27, 13 August 2005 (UTC)

I put it back because I'm not sure but I've never heard that eclogite can be igneous rock. Siim 20:35, 13 August 2005 (UTC)

OK, took it out as eclogite is almost always discussed as a metamorphic rock. However, the mantle plumes page (external links) does mention the possibility of eclogites as mantle igneous cumulates - still questionable. Vsmith 01:16, 14 August 2005 (UTC)

Eclogite is definitivelty NOT an igneous rock. Eclogite xenoliths are present in kimberlites, lamproites and the like and come from mantle depths. As garnet is a prime eclogitic mineral, and the rock is not silica undersaturated (unlike garnet-bearing lamproites), it cannot be the result of crystal accumulation; the number of silica-undersaturated ultramafic intrusions can be counted on an amputee's hand. Similarly, almost all eclogite is extrmely coarse grained, so it would have to be a cumulate. So it should definitely stay OUT of igneous terminology except as mentioned, as a xenolith.Rolinator 08:56, 24 December 2005 (UTC)

I removed the idea that eclogite can be formed by magma which crystallises within the mantle. A) given the mantle melts to produce magma, how is it supposed to crystallise within the mantle? The mantle is hot. One would think that you'd have to cool the mantle somehow to promote crystallisation of a magma. And secondly, b) how does it get metamorphosed, since it's already in excess of 1000°C, it hasn't got a lot of thermal leverage to metamorphose, let alone the water needed to do this and finally c) have you got any proof of this? For example, where is the chunk of the mantle which has been pushed up onto the earth's surface? I thought we needed to study eclogites and mantle xenoliths because we didn't actually have any mantle on the surface, so where's the evidence of the intusive rocks crystallised in the mantle we don't have? Eclogite isn't a typical constituent of ophiolites for very good reasons; its a prograde metamorphic rock, not a retrograde rock. So the idea that a basaltic or, most likely, ultramafic magma crystallising at depth in the mantle will produce eclogite is as fanciful as anything else in Wikipedia.

Finally, I shall also be reverting some of my stuff because it is valid to talk about eclogite as a source of melts (or not), and the Benioff zone being related to eclogites. I admit it was poorly worded, so as to make it fit in with the remainder of wikipedia, but I shall redo it and present it anew. I do agree that diamonds and coesite are exciting things to find in eclogite, but to restrict eclogite to being some "elucidating" chunk of phlogiston within which diaomonds settle is ridiculous. Rolinator 07:03, 24 January 2006 (UTC)

I have reverted your edits because, if you actually read what I wrote and refered to your textbooks as I have done, you cannot produce basalt from eclogite,because eclogite is basalt. To produce basalt from basalt you have to fully melt it. See magma. Rolinator 01:45, 29 January 2006 (UTC)

Article Evaluation

The article contains relevant information but is confusing in terms of the overall eclogitization process. Reference to the eclogitization page could be included. There is some detail on specific types of eclogite (as defined by accessory mineral assemblages) that relate to formation conditions where the information is spread out between different sections and does not clearly support a single overriding idea that the constituent minerals are indicative of formation processes. Because there are many eclogite facies rocks, there could be a single section describing formation based on rocks from specific localities, which includes using a general geochemical framework for identification and distinction between types.

The article uses cited material ranging from 1995-2017 and is mostly up to date but lacks citations in every section. Material that could be added includes: the subduction origin controversy as well as the distribution of mantle eclogite xenoliths, their occurrence, and a relationship to cratonic lithosphere. A more detailed explanation on the carbon isotopic ratio could be included in the ‘eclogite diamonds’ subsection as well as the importance of eclogite as a diamond source rock.

The overall article could use more citations to support claims that are being made and could be re-written in a more organized manner. This is especially true in the ‘Importance of eclogite’ section which redundantly states the high-pressure conditions that are previously described in both the ‘Origins’ and ‘Eclogite facies’ sections. Citations for the usefulness of eclogite in understanding plate tectonic processes are needed as well as the partial melting models in the ‘Formation of igneous rocks from eclogite’ subsubsection. This section clearly describes that eclogite can only produce basalt at 100% melt conditions but needs citations. Further discussion on partial melting describes adakite and TTG formation and is cited from a single publication from 2003.

The idea that eclogite derives from subducted oceanic crust is important and mostly accepted in the geologic community, however this topic is controversial for mantle eclogite xenoliths and both sides of the argument could be presented, including why it is difficult to understand their affinity/protolith.

The citation links are working and support claims in the article. They include several peer-reviewed publications. There are many pieces of information that are represented as facts but do not include citations.

Questions:

Can Oxygen isotope data be included to support the idea that eclogite derives from oceanic crust? Are there other ideas to support this conclusion?

Should this idea be presented clearly in its own section?

Catherinepeshek (talk) 16:47, 15 October 2021 (UTC)

Bibliography

Coleman, C.G., Lee, D.E., Beatty, L.B., Brannock, W. W. (1965). Eclogites and Eclogites: Their Differences and Similarities. 39, 1965.

Ireland, T.R., Rudnick, R.L., Spetsius, Z., 1994. Trace elements in diamond inclusions from eclogites reveal link to Archean granites. Earth and Planetary Science Letters 128, 199–213.

MacGregor, I. D., & Manton, W. I. (1986). Roberts victor eclogites: Ancient oceanic crust. Journal of Geophysical Research, 91(B14), 14063. https://doi.org/10.1029/jb091ib14p14063

Gurney, J. J., and B. Harte. "Chemical variations in upper mantle nodules from southern African kimberlites." Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 297.1431 (1980): 273-293.

Muehlenbachs, Karlis. "Alteration of the oceanic crust and the 18O history of seawater." Stable isotopes in high temperature geological processes (2018): 425-444. — Preceding unsigned comment added by Catherinepeshek (talk • contribs) 19:21, 30 October 2021 (UTC)

Source

If any of the geologists want to evaluate it. I have nothing to do with it because I am not competent in this field. Mesoarchean subduction processes: 2.87 Ga eclogites from the Kola Peninsula, Russia Sciencia58 (talk) 20:48, 14 December 2021 (UTC)