Active oceanic detachment faulting, flexure of fault planes, gabbroic plutons and hydrothermal circulation

Abstract: Oceanic detachment faulting is responsible for the exposure of plutonic rocks at slow spreading ridges, and plays a significant part in the generation of new oceanic lithosphere. We examine the morphology of a newly-identified area of active and inactive detachment faults at 13-14_N, Mid-Atlantic Ridge.There it is possible to follow the evolution of the morphology of corrugated detachment faults from their birth within the median valley floor to their death as they spread away from the axis.The changes that take place set close limits on the nature of active detachment faulting, and allow the evolving morphology to be explained.The association of active detachment faulting with black smoker hydrothermal systems suggests a link between faulting and magmatic activity, as do the results from drilling older detachment fault surfaces.The faults may have been localized above gabbroic magma chambers intruded along the spreading axis, consistent with the origin of the corrugations by continuous casting. ------------------------------------------------------------------------ Séminaires Géosciences Marines ------------------------------------------------------------------------