The birth and death of the oceanic lithosphere: Geochemical and tectonic investigations of the Juan de Fuca Ridge and Mariana Trench

The research I conducted for my dissertation addresses specifically: (1) the role of fluid alteration of the ocean crust during its maturing stages near a spreading center using the Juan de Fuca Ridge as the model; and (2) the role of fluids in the demise of the crust as it is recycled within a subduction zone, using the non-accretioanry Mariana system as the model. The first 2 chapters detail the progressive alteration of a region of young oceanic crust (at the Juan de Fuca Ridge) by combining the results of multiple deep-sea drilling legs, long-term borehole observatory sampling, and hydrothermal vent chemistry. The third chapter examines fluid transfer during serpentinization of the suprasubduction lithosphere, based on the relationship between trace-element patterns and serpentine phases in serpentinite mud pore fluids and serpentinite mud/rocks collected at serpentinite mud volcanoes on the Mariana forearc. The final chapter presents detailed bathymetric and Hybrid Remote Operated Vehicle (HROV) Nereus surveys conducted in the deepest regions of the Mariana Trench (and therefore the world) that are interpreted to explain the regional tectonic processes and to guide future exploration efforts. These new efforts may lead to further discoveries of unique geologic features that will allow researchers to better understand the ongoing evolution of the Earth.