Talk:Eclogite

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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)