Eclogite Guide, Meaning , Facts, Information and Description
Eclogite is a coarse grained mafic to ultramafic metamorphic rock. The fresh rock can be very striking in appearance with red to pink garnets, almandine-pyrope, in a green matrix of sodium rich pyroxene, omphacite. Accessory minerals are kyanite, rutile, occasional quartz, hornblende, olivine, phengite, paragonite, zoisite, dolomite, corundum, and, rarely, diamonds.Eclogite typically results from low-medium temperature and high pressure metamorphism of mafic igneous rocks (typically basalt) as it plunges into the mantle in a subduction zone. Under mantle conditions from 30 to 100km depth at 500 - 1000 oC and > 20 kBar the basic mineralogy is transformed into the eclogite assemblage. If the eclogite melts it can then be treated as an igneous rock on solidification. Some consider eclogite to be representative of upper mantle and see the tholeiitic basalt volcanism typical of eclogite melts. Eclogite that is brought to shallow conditions is quite unstable and retrograde metamorphism often occurs with secondary amphibole and plagioclase forming reaction rims on the primary pyroxene minerals. Xenoliths of eclogite reportedly occur in the kimberlite pipes of the diamond mines of South Africa.
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