Tectonic Denudation of Upper Mantle Along Passive Margins: A Model Based on Drilling (ODP Leg 103) and Diving (Galinaute Cruise) Results, Western Galicia Margin, Spain

G. Boillot, E. L. Winterer, M. Recq, J. Girardeau, J. Kornprobst, J. P. Loreau, J. Malod, D. Mougenot

During ODP Leg 103 (April-June 1985) and the Galinaute cruise (June-July 1986), serpentinized peridotite (clinopyroxene-spinel harzburgite) was recovered within the basement approximately at the boundary between the North Atlantic ocean crust to the west and the thinned continental crust of the Galicia passive margin (Spain) to the east. The exposure of mantle-derived periodotite on the sea floor occurred at the end of the period of rifting, roughly 110 Ma. Ductile shear zones observed in the peridotite are consistent with movements along a deep, low-angle normal fault rooted within the upper mantle and dipping eastward beneath the Galicia margin. To explain the tectonic denudation of the mantle at the ocean-continent boundary, we use a nonuniform stretching model for the lithosphere, set up from Wernicke's model.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.