CONNECTIVITY OF AQUEOUS FLUID IN THE EARTHS UPPER-MANTLE

The geometrical distribution of the aqueous fluid ih textural equilibr ium with forsterite has been investigated by measurements of the dihed ral angle, theta, at pressures of 3 and 5 GPa and at 1000 degrees C. T he measured a at 3 and 5 GPa are 48 degrees and 40 degrees to 42 degre es, respectively. Since a value of theta smaller than 60 degrees indic ates that the aqueous fluid can form an interconnected network along t he three-grain and through the four-grain junctions, the existing aque ous fluid in the mantle can migrate by percolation even at the small v olume fractions in the pressure range. Combining these results with pr eviously published results at lower pressure, it is suggested that the interconnected network of aqueous fluid is stable only at higher pres sure than 2 Cpa for the commonly accepted water content of the upper m antle. The present results show that the large scale transport of aque ous fluid is possible above 2 GPa, and that the physical properties of the upper mantle may change drastically at that pressure.