by the minerals chlorite, serpentine-antigorite and brucite. Traces of talc, tremolite and dolomite may be present, as it is very rare that no carbon dioxide is present in metamorphic fluids. At higher metamorphic grades, anthophyllite, enstatite, olivine and diopside dominate as the rock mass dehydrates. Mineralogic variations in komatiite flow facies Komatiite tends to fractionate from high-magnesium compositions in the flow bases where olivine cumulates dominate, to lower magnesium compositions higher up in the flow. Thus, the current metamorphic mineralogy of a komatiite will reflect the chemistry, which in turn represents an inference as to its volcanological facies and stratigraphic position. Typical metamorphic mineralogy is tremolite-chlorite, or talc-chlorite mineralogy in the upper spinifex zones. The more magnesian-rich olivine-rich flow base facies tend to be free from tremolite and chlorite mineralogy and are dominated by either serpentine-brucite +/- anthophyllite if hydrated, or talc-magnesite if carbonated. The upper flow facies tend to be dominated by talc, chlorite, tremolite, and other magnesian amphiboles (anthophyllite, cummingtonite, gedrite, etc.). For example, the typical flow facies (see below) may have the following mineralogy; Geochemistry Komatiite can be classified according to the following geochemical criteria; SiO2; typically 40–45% MgO greater than 18% Low K2O (<0.5%) Low CaO and Na2O (<2% combined) Low Ba, Cs, Rb (incompatible element) enrichment; ΣLILE <1,000 ppm High Ni (>400 ppm), Cr (>800 ppm), Co (>150 ppm) The above geochemical classification must be the essentially unaltered magma chemistry and not the result of crystal accumulation (as in peridotite). Through a typical komatiite flow sequence the chemistry of the rock will change according to the internal fractionation which occurs during eruption. This tends to lower MgO, Cr, Ni, and increase Al, K2O, Na, CaO and SiO2 toward the top of the flow. Rocks rich in MgO, K2O, Ba, Cs, and Rb may be lamprophyres, kimberlites or other rare ultramafic, potassic or ultrapotassic rocks. Morphology and occurrence Komatiites often show pillow lava structure, autobrecciated upper margins consistent with underwater eruption forming a rigid upper skin to the lava flows. Proximal volcanic facies are thinner and interleaved with sulfidic sediments, black shales, cherts and tholeiitic basalts. Komatiites were produced from a relatively wet mantle. Evidence of this is from their association with felsics, occurrences of komatiitic tuffs, niobium anomalies and by S- and H2O-borne rich mineralizations. Textural features A common and distinctive texture is known as spinifex texture and consists of long acicular phenocrysts of olivine