An aenigmatite-richterite-olivine trachyte from Puu Koae, West Maui, Hawaii

The Puu Koae trachyte forms a conspicuous bulbous dome on the north shore of West Maui. This trachyte has a peraluminous composition, but contains alkali amphibole, aenigmatite, iron-rich olivine, and sodic clinopyroxene. This mineralogical association indicates that the trachyte crystallized from a peralkaline melt, and that its composition changed at the time of crystallization by loss of sodium. The conclusion is that peralkaline salic liquids have been produced at one stage of the evolution of the island of Maui.