Melt Connectivity and Its Effect on Grain Growth in Natural Olivine Aggregates: An Experimental Study

Tuesday, 16 December 2014
Leila Hashim1, David Sifre1, Jacques Précigout1, Emmanuel Gardés2, Emmanuel Le Trong1 and Fabrice Gaillard1, (1)ISTO Institut des Sciences de la Terre d'Orléans, Orléans Cedex 2, France, (2)Commissariat à l’Énergie Atomique-CNRS-Ganil, Caen, France
To better constrain the rheology of the mantle, experimental studies on olivine grain growth have been conducted (Faul and Scott, 2006; Karato, 1989; Nichols and Mackwell, 1991) since the grain size is an important parameter under dynamic regimes (e.g. diffusion creep and grain boundary sliding). In order to better define the melt effect on the rheological response of a partially molten olivine aggregate, we have experimentally investigated the effect of melt on olivine grain growth and the connectivity of this melt phase. Experiments were performed in 3/4” piston cylinders at 500 MPa confining pressure, different temperatures (i.e. 1100°C, 1250°C and 1400°C) and four durations (1h, 12h, 72h and 15 days). Starting material was composed of natural San Carlos olivine (5 μm<grain size<15 μm) containing different amounts (0 wt%, 0.2 wt%, 1 wt% and 10 wt%) of volatile-free basalt (Sifré et al., 2014). San Carlos olivines were previously handpicked and annealed under controlled oxygen fugacity conditions close to the FMQ buffer. After the experiments, the melt connectivity was assessed through scanning electron microscope (SEM) images in backscattered electron mode. Electron backscatter diffraction (EBSD) maps of each sample were also collected in order to determine the olivine grain sizes as a function of time and melt content.


Faul, U. H., Scott, D., 2006. Grain growth in partially molten olivine aggregates. Contributions to Mineralogy and Petrology 151 (1), 101–111.

Karato, S.-I., 1989. Grain growth kinetics in olivine aggregates. Tectonophysics 168 (4), 255–273.

Nichols, S. J., Mackwell, S. J., 1991. Grain growth in porous olivine aggregates. Physics and Chemistry of Minerals 18 (4), 269–278.

Sifré, D., Gardés, E., Massuyeau, M., Hashim, L., Hier-Majumder, S., Gaillard, F., 2014. Electrical conductivity during incipient melting in the oceanic low-velocity zone. Nature 509 (7498), 81-85.