Next-generation 3D imaging of the on- and off-axis mantle and crustal magmatic systems at the Endeavour segment

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

Next-generation 3D imaging of the on- and off-axis mantle and crustal magmatic systems at the Endeavour segment The global mid-ocean ridge seafloor spreading system accounts for ~85% of Earth's annual magma budget, dominating the mass and energy exchange between the solid earth and its hydrosphere. Magmatic systems beneath spreading centers drive high- and low-temperature hydrothermal activity that modulates the long-term chemistry of the oceans, hydrates the crust and mantle, supports novel ecosystems whose study has altered our view of the origin of life on Earth, and deposits valuable mineral resources. The fundamental unit of the global mid-ocean ridge system is a ridge segment. Within a single ridge segment there are systematic variations in tectonic, volcanic and hydrothermal processes. Ridge segments vary systematically with spreading rate with three basic types: fast-, intermediate- and slow-spreading. Understanding what governs spreading-center segmentation is to understand the fundamental unit of a globe encircling system. The broader significance and importance of the project will be to use next-generation seismic imaging methods to constrain the structure of the magmatic system beneath a well-studied mid-ocean ridge segment. The study site is located off the west coast of the US and is a focus area for international research with a seafloor observing node as part of Neptune Canada, which is allied with the US Ocean Observatory Initiative. The project will support a junior female researcher and a graduate student as part of the research. There is also significant international collaboration with United Kingdom researchers on innovative new seismic data analysis techniques. Understanding mass and energy transfer at mid-ocean ridges requires mapping mantle and crustal magmatic systems and their relationship to hydrothermal and tectonic processes. The location, size, shape, and longevity of magmatic systems depend on factors such as the patterns of melt delivery from the mantle to the crust, melt ascent pathways, and perhaps most importantly, the efficiency of heat removal. Hydrothermal flow patterns are in turn determined by the distribution of heat sources and crustal permeability. To understand these linkages, the project will more accurately map mantle and crustal magmatic systems at the Endeavour segment both on- and off-axis. The primary objectives are to determine (i) what controls the characteristics and distribution of crustal magma bodies both on- and off-axis, and (ii) how hydrothermal heat transfer interacts with and shapes crustal magmatic systems. These objectives will be accomplished by applying 3D anisotropic travel time tomography and 3D full-waveform inversion (FWI) to wide-angle seismic data from a seismic tomography experiment (ETOMO) at the Endeavour. Segment-scale compressional wave velocity images will be generated to map the distribution of crustal magma bodies, the pattern of melt transport from the shallow mantle through the lower crust, and to infer spatial variations in crustal temperature and melt fraction. The study is sited at the Endeavour Ridge where a wealth of previous results, high-quality seismic data, and recent advances in seismic imaging methods can be brought together at a segment where there are strong contrasts between the segment center and ends.