Experimental Studies of Trace Water in the Mantle

California Institute Of Technology, Pasadena CA

Investigators

Abstract

This is a proposal to carry out experiments in a new high-pressure research lab at Caltech. The lab is equipped with two multi-anvil presses. Asimow proposes to use this equipment to carry out experiments on the solubility of water in mantle systems under conditions of less-than-water-saturated ("damp" conditions with water 50-500 ppm levels). These are probably realistic for the in situ mantle undergoing melting below ridges and hot spots. This is an ambitious project and consists of numerous elements. Among these are to determine the solubility of H2O in mantle phases olivine, Opx, Cpx, Ga and eclogite phases (Cpx, Ga, rutile) and how solubility changes as a function of T, P, and system composition, including fO2. Actual melting experiments will be carried out to 5-6 GPA in order to determine the melt chemistry at small melt fractions and small H2O contents. These experiments may be applicable to the mantle's low-velocity zone at pressures of ~6 GPA (~200 km depth) The experiments will be done by the diamond aggregate technique and include determination of a range of mantle solidi under variable water conditions. The proposal is for two years and comprises post-doc salary for Jed Mosenfelder and supplies needed to carry out the experiments. The PI is aware that two years is not enough time to carry out the full program of work proposed- the goals are listed for illustrative reasons only.