Static Compression of Hydrous Silicate Liquids

University Of New Mexico, Albuquerque NM

Investigators

Abstract

The primary goal of this project is to determine the density and compressibility of hydrous silicate liquids at high-pressure. This will be accomplished by performing static compression sink/float experiments in piston-cylinder and multi-anvil devices at pressures from 0.5 to 20 GPa. The sink/float technique has been used by this group in previous studies to determine high-pressure density and compressibility of anhydrous liquids that include peridotite, komatiite, terrestrial and lunar basalt, and Fe2SiO4. This study will build on this database and extend it to hydrous compositions by investigating these same liquids with added H2O. The proposed measurements will give new insight into the structure and physical properties of hydrous silicate liquids, and the mobility of water-bearing magmas in the Earth's mantle. Hydrous silicate liquid isothermal bulk moduli (KT) and the pressure derivative (K'), once established by these experiments, can then be applied to determine if equilibrium crystal-liquid density inversions exist during wet melting of the mantle. There is a growing realization that mantle magmatism, both primordial and recent, may frequently happen in the presence of water. This phenomenon could affect a wide range of the Earth's interior processes, from shallow crustal levels to the deep region at the boundary between the mantle and core. The main focus of this study is determine if there are regions in the Earth where certain magmas with dissolved water, also called hydrous silicate liquids, will become trapped or even sink, rather than rising buoyantly to the surface. We know from earlier experimental studies that some magmas, without water, become negatively buoyant at high pressure and can sink deep in the interiors of the Earth and the Moon, but this has never been determined for water-bearing or "hydrous" magmas. Therefore, this is to be one of the first systematic studies to determine the density and compressibility of hydrous silicate liquids at high pressures and temperatures in the laboratory that recreate conditions of magmatism in the Earth's mantle. This project is co-funded by the following programs: Petrology and Geochemistry, and Geophysics programs in the Division of Earth Sciences (GEO) together with the EPSCoR program (EHR).