T34B-01 INVITED
Focusing in on Mid-Ocean Ridge Segmentation
A fundamental characteristic of the globe-encircling Mid Ocean Ridge is the segmentation observed across a range of scales defined by transform and smaller non-transform offsets of the axis. The heterogeneous crustal section inherited from this segmentation during crustal formation influences the subsequent deformation and hydrothermalism of the crust and upper mantle as the plate ages and is subducted at the trenches. There is long-standing debate regarding the origin and significance of mid-ocean ridge segmentation. Does it arise from lithospheric sources or is it controlled by convective flow patterns in the underlying asthenosphere? Lithospheric stresses may dominate at the smallest scales of segmentation (5- 10's of kilometers), whereas mantle processes control the larger scale structures (100's km). The availability of multi-disciplinary datasets from the region of focused investigation at the East Pacific Rise 8°-10° N provides a new perspective on segmentation across a range of scales. Mapping and seafloor observational studies constrain the surficial volcanic segmentation of the ridge. Microseismicity and fluid geochemical studies define segmentation in the ridge axis hydrothermal system within the upper crust. Seismic tomography and other geophysical studies constrain the distribution of melt within the mantle. Newly acquired three-dimensional seismic imaging studies of crustal structure allow us to directly link the magmatic system within the mid-crust to the volcanic and hydrothermal segmentation above and the shallow mantle segmentation below. Focused investigation in this region has spanned two dike intrusion and volcanic eruption events, providing time series information on the evolution of the system through these primary crustal accretion events. Implications of these integrated high-resolution studies will be considered in light of existing models for segmentation.