lherzolite

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lherzolite A two-pyroxene- and olivine-bearing, coarse-grained, ultrabasic rock consisting of essential magnesium- rich olivine, chromium-magnesium clinopyroxene (Cr-diopside), magnesium orthopyroxene (enstatite), and garnet or spinel, which is found as xenoliths in basalts and as a component of Alpine ultramafic bodies. A mantle origin for many lherzolites is attested to by their metamorphic (see METAMORPHISM) texture, their high-pressure mineral assemblage, and their ultrabasic composition. Using evidence from experimental petrology, lherzolites are interpreted as examples of undepleted mantle (i.e. mantle which has not undergone partial melting to generate basalt magma). The name is taken from the type locality, at Lherz in the French Pyrenees.

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