Lherzolite
Lherzolite is a coarse-grained ultramafic igneous rock consisting of 40% to 90% olivine along with abundant orthopyroxene and lesser amounts of 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 layer 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.
Photographed by Tony Peterson
Garnet (Pyrope) Lherzolite
Mantle Xenolith
Kimberley
SOUTH AFRICA
Photographed by Tony Peterson
Garnet (Pyrope) Lherzolite
Mantle Xenolith
Kimberley
SOUTH AFRICA
