Grain boundary melt films in an experimentally deformed olivine- orthopyroxene rock

Abstract

An unexpected microstructure, with important implications for melt distribution in the upper mantle, has been found in a 70% olivine +30% orthopyroxene rock experimentally deformed at 1500K, 300 MPa, where incipient partial melting occurred. As found in previous studies of comparable systems, most melt in the olivine-orthopyroxene sample resided in a network of grain-edge tubes and occasional thick layers. Using electron microscopy at its highest resolution, it is infered that melt also existed in another form as glass films 1.0-1.5 nm thick, along all grain boundaries. All of these melts are unusually SiO2-rich. If thin high-silica melt films are stable they might influence physical properties and melt extraction processes in regions of incipient melting and metasomatism in the upper mantle. -from Authors Show more