provide clues relating to the processes of seafloor spreading which 

 operated at the time of continental separation. Yet except in 

 regions of extensive oil development, the continental margins of 

 the world are largely unknown. 



The continental margin studies, begun in 1971, have concentrated 

 on the margins of the South Atlantic because these were among 

 the least known. Comprehensive geophysical and geological data 

 have been obtained in portions of the eastern Atlantic extending 

 from South Africa to Portugal (completed in 1973), and along 

 the coast of South America from its southern tip to the Caribbean 

 (still underway). These studies are expected to provide insight 

 into the processes of oil field formation during the early stages 

 of seafloor spreading. They have akso identified specific areas off 

 the coasts of Africa and South America where the nature of 

 the sediments indicate the possibility of substantial accumulations 

 of oil and gas, sufficient to justify opening up these locations to 

 oil exploration. 



Metallogenesis and Plate Tectonics: The Mid-Atlantic Ridge and 

 the Nazca Plate 



Studies in mining areas suggest that metallic ores may have 

 formed under conditions similar to those now operating along the 

 mid-oceanic ridges and active trenches. To verify this, investiga- 

 tions into the relationship between metallogenesis and plate tec- 

 tonics have been carried out along the Mid-Atlantic Ridge since 

 1972, and on the Nazca Plate since 1971. 



In the French-American Mid-Ocean Undersea Study (FAMOUS), 

 jointly funded with ONR and NOAA (and coordinated with 

 NSF's Deep Sea Drilling Project), French and American scientists 

 investigated processes along the Mid-Atlantic Ridge using manned 

 submersible vehicles. Rock samples, sediments, and water collected 

 during this effort suggest that metalbearing solutions are coming 

 to the surface at selected points on the ridge valley and on the 

 adjacent fracture zones. 



Teams of geologists and geophysicists are making an intensive 

 study of the processes operating along the edges of the Nazca 

 Plate in the eastern South Pacific and their relationship to the 

 extensive copper deposits in the Andes. These processes appear to 

 carry metalliferous sediments under the Andes where they are 

 concentrated into mineral dej^osits and subsequently uplifted and 

 eroded to the point where they are available for exploitation. The 

 project has found evidence of extensive faulting associated with 

 accretion of sediments in the Peru-Chile Trench, and of metal-rich 



34 



