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Durham University

Department of Earth Sciences


Publication details for Professor Richard Hobbs

Singh, S. C., Harding, A. J., Kent, G. M., Sinha, M. C., Combier, V., Bazin, S., Tong, C. H., Pye, J. W., Barton, P. J., Hobbs, R. W., White, R. S. & Orcutt, J. A. (2006). Seismic reflection images of the Moho underlying melt sills at the East Pacific Rise. Nature 442: 287-290.

Author(s) from Durham


The determination of melt distribution in the crust and the nature
of the crust–mantle boundary (the ‘Moho’) is fundamental to the
understanding of crustal accretion processes at oceanic spreading
centres. Upper-crustal magma chambers have been imaged
beneath fast- and intermediate-spreading centres1–4 but it has
been difficult to image structures beneath these magma sills.
Using three-dimensional seismic reflection images, here we report
the presence of Moho reflections beneath a crustal magma
chamber at the 98 030 N overlapping spreading centre, East Pacific
Rise. Our observations highlight the formation of the Moho at
zero-aged crust. Over a distance of less than 7 km along the ridge
crest, a rapid increase in two-way travel time of seismic waves
between the magma chamber and Moho reflections is observed,
which we suggest is due to a melt anomaly in the lower crust. The
amplitude versus offset variation of reflections from the magma
chamber shows a coincident region of higher melt fraction
overlying this anomalous region, supporting the conclusion of
additional melt at depth.