Geophysical and Petrological Constraints on Ocean Plate Dynamics

Emily Sarafian, Ph.D., 2017
Rob Evans, Co-advisor
Glenn Gaetanni, Co-advisor

This thesis investigates the formation and subsequent motion of oceanic lithospheric plates through geophysical and petrological methods. Ocean crust and lithosphere forms at mid-ocean ridges as upwelling asthenosphere melts and flows away from the ridge axis. In Chapters 2 and 3, I present the results from partial melting experiments of peridotite to examine the mantle melting point, or solidus, beneath a mid-ocean ridge. These chapters conclude that the mantle solidus is hotter than currently estimated. Once formed, the oceanic plate moves atop the underlying asthenosphere away from the ridge axis. Chapter 4 uses seafloor magnetotelluric data to investigate the mechanism responsible for plate motion at the lithosphere-asthenosphere boundary. By applying petrological constraints, I conclude that either a thermal or hydration mechanism supports plate motion. Oceanic plate motion has dramatically changed the surface of the Earth over time, and evidence for ancient plate motion is obvious from detailed studies of the continental lithosphere. In Chapter 5, I invert magnetotelluric data collected over eastern Zambia. This chapter elucidates the geometry of the tectonic elements in the region, which collided as a result of past oceanic plate motion. Combined, the chapters of this thesis provide critical constraints on ocean plate dynamics.