Komatiite
Komatiite is a type of ultramafic extrusive rock with a high magnesium oxide (MgO) content. Generally, MgO content is >18% (18-33%). It is rich in Ni and Cr, with a CaO/Al2O3 ratio of usually >0.8. In contrast, it is lacking in Na, K, Ti, and incompatible elements. The Archean Eon minerals present in komatiite are mainly fine skeletal or dendritic olivine or clinopyroxene phenocrysts, with nearly parallel spinifex structure, interspersed with small amounts of chrome spinel, chromite, and glass substrate. Spinifex structural distribution is in the upper part of the komatiite lava flow. It is an important rock feature that marks komatiite, implying that the temperature of Earth’s early curst was relatively high and there was rapid condensation.
