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Eclogite

Pictures of Metamorphic Rock Types

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Eclogite ("ECK-lo-jite") is an extreme metamorphic rock, formed by regional metamorphism of basalt under very high pressures and temperatures. Eclogite is the name of highest-grade metamorphic facies. (more below)
From very deep subduction
Photo (c) 2005 Andrew Alden, licensed to About.com (fair use policy)
Click the photo to see the larger version. This eclogite specimen from Jenner, California, consists of high-magnesium pyrope garnet, green omphacite (a high-sodium/aluminum pyroxene), and deep-blue glaucophane (a sodium-rich amphibole). It was part of a subducting plate during Jurassic times, about 170 million years ago, when it formed. Much more recently, during the last few million years, it was raised and mixed into younger subducted rocks of the Franciscan complex. The body of eclogite is no more than 100 meters across today.

For more photos see the Eclogite Gallery.

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