Collaborative Research: From Silicate Melts Properties to the Dynamics and Evolution of an Early Basal Magma Ocean

Stanford University, Stanford CA

Investigators

Abstract

The goal of this project is to understand the potential role of a basal magma ocean in influencing magnetic field processes in the early Earth. A basal magma ocean arises when an initially molten mantle begins solidifying from the middle outwards, and a downward crystallizing basal magma ocean has been proposed as a mechanism to power an early magnetic field in our planet. The research team will collect key, currently missing measurements on the physical properties of iron-bearing silicate melts to better understand the dynamics and evolution of an early basal magma ocean and further evaluate the scenario that a basal magma ocean powered the early Earth's magnetic field. The main questions to be addressed are: What is the initial depth of the basal magma ocean? How long would a basal magma ocean exist? What affects the strength of a magnetic field generated within a basal magma ocean? Would the evolution of iron-enriched melts be consistent with seismic anomalies observed at the base of the mantle? This work represents a new, multidisciplinary collaboration between experimental mineral physics (dynamic and static compression techniques) and computational geodynamics to advance our understanding of deep and early Earth processes. This work will support the training of graduate students in a variety of experimental methods: dynamic and static compression techniques and X-ray and in-house characterization tools at unique world-class facilities, as well as modeling approaches to develop and refine models of planetary interiors that use state-of-the-art experimental constraints. This work will also support research experiences to undergraduate and high school interns, using a cohort-building model with multiple layers of support and mentoring. This project includes three crucial, collaborative research pieces: 1) dynamic compression experiments to measure iron spin state and liquid structure of dense melts; 2) static compression experiments in a laser-heated diamond-anvil cell measurements to constrain iron partitioning and melting temperature; 3) geodynamic modelling which will use the experimental constraints to understand the thermal and magnetic evolution of the coupled solid mantle-basal magma ocean system. The research team will collect new measurements on the physical properties of iron-bearing silicate melts which represent crucial experimental constraints for modeling the dynamics and evolution of an early basal magma ocean. These properties include iron-spin state (which has only recently become feasible for high pressure melts) and density of silicate melt, iron partitioning between silicate melt and lower-mantle minerals, and the effect of iron on melting temperature. These new measurements will provide a deeper understanding of the evolution of a basal magma ocean, from its initial conditions to properties and compositions of late-stage solidification products, which may still be present in the deep mantle. The team will further investigate the possibility that the Earth's magnetic field may have been generated from within the basal magma ocean. Evaluating the duration of time this might have occurred will be accomplished by supplying new geodynamic models of basal magma oceans with relevant, high-pressure, high-temperature physical properties measurements of constituent materials. 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.