OCE-RIG: Crustal and Mantle Processes at Gorda Ridge Based on Olivine-Hosted Melt Inclusion Compositions

The goal of this project is to determine the depths and distribution of crystallization of magmas within the oceanic crust at mid-ocean ridges. The release of latent heat during crystallization of magmas that forms the oceanic crust is a primary mechanism by which heat is transferred from the Earth's interior to the oceans and atmosphere, and it drives the hydrothermal circulation that sustains chemosynthetic life on the seafloor. Thus, determining where crystallization occurs within the magmatic system and how magmas are distributed to the oceanic crust is critical for our understanding of global geochemical cycles and mid-ocean ridge systems as a whole. This project will provide funding and research experience for a graduate and undergraduate student at Boise State University (BSU) and results will be incorporated into a new marine geosciences course at BSU.

The primary goal of this project is to determine how variations in spreading rate, ridge axis morphology, and lithospheric thicknesses influence crystallization depths and magma compositions along Gorda Ridge. The investigator will use major, trace and volatile compositions of olivine-hosted melt inclusions to address three questions regarding melting and crystallization: (1) How do crystallization depths vary along Gorda Ridge and what does this indicate about lithospheric thickness? (2) Are there variations in magma compositions and melting systematics that correlate with ridge morphology? (3) How do melting systematics and crystallization depths beneath North Gorda compare to the Cleft segment on the Juan de Fuca Ridge? To address these questions, the investigator will determine the pressures/depths of crystallization of each melt inclusion using vapor-saturation pressures derived from volatile contents. Next, major and trace element concentrations will be used to determine how magma compositions vary along the ridge axis. These results will be incorporated into numerical calculations to determine how mantle source compositions and total extents of melting vary along axis. Finally, crystallization depths and melting models will be compared to previous studies of melt inclusions from a variety of ridges to determine how variations in spreading rate, magma supply and lithospheric thickness influence melting and crystallization beneath mid-ocean ridges.