THE STABILITY OF HYDROUS MANTLE PHASES

Abstract

It is widely recognized that hydrous minerals are involved in a number of geochemical processes in the Earth’s mantle. Their presence affects the onset of melting and can control the partitioning of trace elements during partial melting. They have accordingly been implicated in the source regions of many types of magmas including alkaline basalts and highly-potassic lavas. As well as being intimately linked with the occurrence of mantle metasomatism, hydrous phases can also buffer fluid compositions in the mantle and consequently dictate the style of metasomatism. The dehydration or melting of hydrous minerals in subducting lithosphere and associated infiltration of hydrous solutions (fluids or melts) into the overlying mantle wedge are important steps in the production of island arc magmatism.