TrekGEO > Mineral Trail > Occurrence > Peridotite

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Chemical Process (Liquid-phase Growth) - Closed system under ground (Melt precipitation)


Ultramafic rock

Mineral composition

Mafic minerals > 70 vol% (Mafic)

Chemical composition

SiO2 < 45 wt% (Basic).


Equigranular texture composed of grains more than a few mm.

Equigranular texture composed of grains more than a few mm, associated with larger euhedral phenocrysts.

Required Geological Setting

Accretionary complexes, Island arc volcanoes


Rock forming minerals in peridotite, mafic (basic) plutonic rock formed from magma under ground. Peridotite is the major constituent of mantle, and also formed by differentiation of basaltic magma. Peridotites originated from mantle and oceanic plates were accreted as parts of accretionary complexes. Peridotite also observed as accidental fragments associated with pyroclastics and xenoliths in basalt. Mantle is composed of pyroxenites and lherzolite, refractory material of the upper mantle after forming tholeiitic magma is composed of harzburgite. Cumulate rocks by differentiation in magma chambers are composed of wehrlite and dunite. Very rarely, dunite is also formed as serpentinite subjected to contact metamorphism.

Mineral Assemblages

Dunite: Forsterite

Harzburgite: Forsterite, Orthopyroxene (Enstatite)

Wehrlite: Forsterite, Clinopyroxene (Diopside)

Lherzolite: Forsterite, Orthopyroxene (Enstatite), Clinopyroxene (Diopside), Pyrope

Pyrxenite: Orthopyroxene (Enstatite), Clinopyroxene (Diopside)

Accessary minerals: Plagioclase (Low-P), Spinel (Chromite, Moderate-P), Pyrope (High-P)

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