Eclogite


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Related to Eclogite: Blueschist, granulite, Greenschist

eclogite

[′ek·lə‚jīt]
(petrology)
A class of metamorphic rocks distinguished by their composition, consisting essentially of omphacite and pyrope with small amounts of diopside, enstatite, olivine, kyanite, rutile, and rarely, diamond.

Eclogite

 

a metamorphic rock, composed chiefly of clinopy-roxene and garnet. The clinopyroxene (omphacite) is a mixture of diopside, hedenbergite, and jadeite components; the mixed-composition garnet contains pyrope and almandine, as well as variable amounts of grossularite and andradite. Eclogite varieties with significant amounts of grossularite and disthene (kyanite) are called grospydites.

Various types of eclogite are distinguished according to the content of secondary minerals, including amphibole, enstatite, olivine, plagioclase, kyanite (disthene), corundum, rutile, graphite, and diamond-containing eclogites. Three types are distinguished on the basis of geological conditions of occurrence: the eclogites of the metamorphic zone, which are associated with glaucophane schists and alpine-type hyperbasites; the eclogites of granulite, gneiss, and amphibolite metamorphic complexes; and eclogites that form inclusions (xenoliths) in kimberlites and alkali basaltoids. The first two are formed within the crust; the last is of mantle origin. Deposits of rutile are associated with eclogite, and diamonds are found among the most deep-seated eclogites in kimberlite pipes.

A. A. MARAKUSHEV

References in periodicals archive ?
Except for blueschist and eclogite, the rocks used in the experiment are readily available in school rock collections or from Australian outcrops (Figure 6).
But other researchers have suggested some alternative explanations: Perhaps, these cratonic rocks are cooler than what the literature suggests, which means the rock will be stiffer -- and thus, seismic waves will travel more quickly through them -- even without the diamond or eclogite rocks, Garber added.
12a, b, samples fall mostly in the field of adakites derived from the partial melting of the thick lower crust and metabasaltic and eclogite fields, rather than in that of adakite rocks derived from the partial melting of the delaminated lower crust.
Diamond-bearing eclogite xenoliths * Cat's-eye calcite from Pakistan * Large chatoyant Brazilian emerald * Nonbeadcultured pearls from Strombus gigas * Purple scapolite * Synthetic star sapphire with diffusion-induced colour and star * Partially filled blue chalcedony * Presumably oiled ruby * Inclusions in synthetic star sapphire * Diamond slices * Large Namibian demantoid * Nephrite from British Columbia * Baroque cultured pearls * Ruby from Namya, Myanmar * Rock Creek sapphire update * Unusual tourmaline necklace * Conference reports.
Upper mantle consist mostly of olivine, pyroxene, spinel-structure minerals, and garnet; [31] typical rock types are thought to be peridotite, dunite, and eclogite. Between ~400 km and 650 km depth, olivine is not stable and it is replaced by high pressure polymorph is wadslevite and or ringwoodite.
This recycled oceanic crust was present in the plume as eclogite, a very dense rock that made the hot mantle plume less buoyant.
and Hirschmann, M.M., 2003, Anhydrous partial melting experiments on MORB-like eclogite: Phase relations, phase compositions and mineral-melt partitioning of major elements at 2-3 GPa: Journal of Petrology, v.
Further, Nordic Mining is undertaking large-scale project development at Engebo (Engebofjellet) in Sogn og Fjordane, western Norway, where it has rights to a substantial eclogite deposit with rutile and garnet.
Early core drilling strongly suggested that the EJF Inner of ON-K120 was prospective for diamonds due to the abundance of eclogite xenoliths and coarse kimberlite texture.