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 depths (20 – 30 km). At greater depth plagioclase is unstable and is replaced by spinel. At approximately 90 km depth,
pyrope 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 the lower ultramafic part of
ophiolite complexes (although harzburgite is more common in this setting), from alpine-type peridotite massifs, from fracture zones adjacent to mid-oceanic ridges, and as
xenoliths in
kimberlite pipes and
alkali basalts. Partial melting of spinel lherzolite is one of the primary sources of
basaltic magma.