The Petrology of Oceanic Crust across Fracture Zones in the Atlantic Ocean: Evidence of a New Kind of Sea-Floor Spreading

New data from a region at 4° S on the Mid-Atlantic Ridge, in association with our studies of four other transform faults at 43° N, 9° N, 01° N, and 00° N, and with other workers' reported results, indicate exposure of a wide variety of rock types in fracture zones in the Atlantic Ocean. Rock types include extrusive and intrusive basic rocks as well as plutonic ultrabasic intrusions. Our findings suggest that new oceanic crust, both eruptive and plutonic, is being injected into transform faults. This new crust appears to have different petrologic and chemical characteristics from that formed during sea-floor spreading at normal ridge crests, and forms in response to sea-floor spreading in a direction normal to that which occurs at the ridge crest.