Phase Relations Between Silicate Melts and Crustal Brines

点击翻译按钮获取中文摘要

The ultimate objective of the proposed study is to understand the role of saline crustal fluids on melting processes and material transport in Earth's deeper crust and upper mantle. Experiments proposed will enhance the current understanding of magmatic processes in subduction zones and gauge the contribution of saline fluids on the stability of granitic-forming melts at shallow crustal environments. The proposed study will promote understanding on the mass and heat transfer associated with the deep Earth's hydrological cycle, wherein water is carried into the mantle at subduction zones and released back to the surface at volcanoes. Understanding the introduction, transport, and storage of C-O-H volatiles in the interiors of terrestrial-like planets is profoundly linked to the nature of habitability, the origin of life, and the external evidence of conditions favorable for life. Structural characterization of silicate melts and their glass-forming abilities are directly relevant to materials and glass science. Experimental data will be made available to the public through the Library of Experimental Phase Relations, and a data repository hosted within the institution's web infrastructure. A series of lectures and lab demonstrations/tours will be delivered to George Mason University (GMU) undergraduate/graduate students, and some undergraduate students from GMU will participate in the project during a 10-week summer internship program, creating a strong partnership between a research-institution (CIW) and a public state-funded University (GMU).The solubility and solution mechanisms of volatiles in silicate melts and aqueous fluids governs mantle fluxes, and affects the properties of coexisting phases such as diffusivity, electrical conductivity and viscosity. This has a profound effect on the physical and chemical heterogeneities between the magmatic systems developed along mid-ocean ridges, shallow continental crust and subduction zones. Very little is known, however, about the silicate melt-fluid phase relations, especially for saline fluids enriched in dissolved alkalis, alkaline earths, and halogen ions. This proposal aims to explore the effect of dissolved salts, fluid pH and melt peralkalinity on the phase relations between silicate melts and crustal brines to better understand melt polymerization and C-O-H solubility in the coexisting phases. This project will constrain the melt-fluid relationships as function not only of pressure/temperature but also of relative abundances and compositional variability of the coexisting phases. In a series of hydrothermal diamond anvil cell experiments, Raman vibrational/Infrared spectroscopy will be employed for the in-situ and real-time investigation of the structure, volatile composition and properties of silicate melts coexisting with electrolyte-enriched aqueous solutions. Experiments will reveal the interplay between CO2 solubility, network-modifying cations and extent of melt polymerization. The in-situ studies will be complimented by bulk CO2 solubility measurements in glasses quenched from melt-fluid equilibria at high temperatures and pressures. At the core of this effort is an innovative integration of ex-situ and in-situ experimental protocols along with real-time chemical and spectroscopic analysis. In this study, use of ultrapure synthetic diamond anvils will increase tremendously the effectiveness of analytical methods that monitor in-situ melt-fluid interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.