Formation
(1) Magmatic, by fractional crystallization from ultramafic to mafic, silica-undersaturated melts at high temperatures (1200–1890 °C) in the upper mantle as well as in basalts and gabbros; (2) Contact metamorphism, by thermal decarbonation and silicification of impure, siliceous dolomites at low to medium pressures; (3) Regional metamorphism, by prograde dehydration of serpentinites at pressures and temperatures of the amphibolite to granulite facies (peridotite formation)
