20th International Conference on Mathematical Geophysics; Villefrache-sur-mer, France; June 19-24, 1994

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9316137 Bjarnason This research is to demonstrate that melt flow patterns can be determined seismically by imaging the upper mantle beneath the mid- Atlantic in northern Iceland by deploying an array of 30 PASSCAL seismic instruments for 9 months. Oceanic crustal material is created by the pressure-release melting of upwelling mantle beneath mid-ocean ridges; however, the details of the mantle flow pattern and the processes by which melt segregates and ascends to crustal levels are poorly understood. From surface wave phase velocities and body wave travel time delays, the researchers will construct images of compressional and shear velocity in the upper mantle down to about 150 km. The objectives are: 1) to determine if mantle upwelling beneath the ridge is narrowly or broadly focused and to explore the effects of the Iceland hotspot, 2) to determine if retained partial melt exists within the shallow mantle beneath the ridge, 3) to define the depth range of any zone of retained partial melt, and 4) to distinguish among theoretical mantle flow and melt transport models on the basis of the width of the zones of upwelling and melt generation. ***