Origin of Komatiites

Studying the conditions of formation of komatiite magmas, a unique igneous rock type generated exclusively during the first 2 billion years of earth history, is the aim of this project. Komatiites have been interpreted to represent high temperature eruptive products, and as such provide the primary evidence for high temperatures in the Archean mantle and even the existence of an early whole earth magma ocean. Reevaluation of the 3.49 Ga Barberton Mountain komatiites in South Africa indicates that the komatiitic melts may have formed within a temperature and depth range similar to that present in the modern subduction zones. It also indicates that komatiite magma contained significant amounts of dissolved H2O, which resulted in a lowering of the melting temperature in the mantle source. Interestingly, the high-Mg basaltic komatiites that are the dominant volcanic rock type found in komattite occurrences are most similar in major and trace element composition to modern boninite magmas, a rare, but important subduction zone magma in modern subduction zone environments.