Lherzolite

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Lherzolite is a type of ultramafic igneous rock. It is a coarse grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser calcic chromium rich clinopyroxene. Minor minerals include chromium and aluminium spinels and garnets. Plagioclase can occur in lherzolites and other peridotites that crystallize at relatively shallow detphs (20 - 30 km). At greater depth plagioclase is unstable and is replaced by spinel. At approximately 90 km depth, pyope garnet becomes the stable aluminous phase. Garnet lherzolite is a major constituent of the Earth's upper mantle (extending to ~300 km depth). Lherzolite is known from ultramafic ophiolites and as xenoliths in kimberlite pipes and alkali basalts. Partial melting of spinel lherzolite is one of the sources of basaltic magma.

The name is derived from the Lherz Massif, an ophiolite complex, (the type locality) at Lherz in the French Pyrenees.

[edit] Reference

• Blatt, Harvey and Robert J. Tracy, 1996, Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed., Freeman, ISBN 0-7167-2438-3