title: Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities
abstract: Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.
authors.affiliation: Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla 92093, USA. gkent@ucsd.edu
authors.initials: GM
authors.lastname: Kent
authors.initials: SC
authors.lastname: Singh
authors.initials: AJ
authors.lastname: Harding
authors.initials: MC
authors.lastname: Sinha
authors.initials: JA
authors.lastname: Orcutt
authors.initials: PJ
authors.lastname: Barton
authors.initials: RS
authors.lastname: White
authors.initials: S
authors.lastname: Bazin
authors.initials: RW
authors.lastname: Hobbs
authors.initials: CH
authors.lastname: Tong
authors.initials: JW
authors.lastname: Pye