IUGS reclassification of the high-Mg and picritic volcanic rocks

The 1989 IUGS classification of the igneous rocks for the high-Mg and picri tic volcanic rocks has been revised. Instead of an 18 wt % MgO minimum limi t being applied for all high-Mg and picritic volcanic rocks, that is note, applicable only to the high-Mg rocks such as komatiite and meimechite. The minimum MgO requirement for picrite is reduced to 12 wt %. The SiO2 former boundary figure between boninite and komatiite-meimechite-picrite, which wa s 53 wt %, is reduced to 52 wt %, and the total alkali content for komatiit e and meimechite is increased to 2% and for picrite to 3%.