Experimental Investigation of Mineral-Fluid Equilibria at High Pressure

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Manning EAR-0337170 Water-rich fluids are common in the deep crust and upper mantle. Because mineral solubilities are high in these environments, liberation and migration of such fluids causes significant mass transfer. Fluids generated by subducting lithosphere transfer solutes from the slab and therefore play a fundamental role in mediating chemical cycling in the Earth. Xenolith suites show that significant regions of the upper mantle may be modified by passage of H2O-CO2-NaCl fluids. During crustal metamorphism, solute-rich fluids may play a crucial role in the redistributing matter. Quantitative understanding of the processes by which fluids transport material requires accurate knowledge of mineral solubility. At high pressures (>5 kbar), experimental challenges have previously limited the availability of key data; however, new techniques now make it possible to carry out studies on important model systems. This project involves three sets of experimental studies of aimed at better understanding high-pressure mineral-fluid equilibria: (1) studies of silica-polymer formation over a broad range of pressure and temperature; (2) experiments on the changes in solute chemistry associated with the second critical end-point in the system albite-water; and (3) characterization of the solubility of the volatile-bearing phases calcite and anhydrite. The intellectual merit of the proposed investigation will be quantitative constraints on the chemistry of aqueous species at high pressure, where existing data are limited. Such data are critical for understanding how fluids participate in the material cycling in the Earth. Broader impacts will include student training and mentoring. The proposed experiments on albite- paragonite-quartz are a component of Ph.D. studies of A. Antingano. The PI has also included undergraduates from diverse backgrounds in petrologic research at UCLA, resulting in published abstracts at professional meetings.