99= 



95' 



900 



30" 



25' 



20' 



VERACRUZ 



99« 



95° 



90O 



Figure 27. — Ship tracks for seismic data collected by Uni- 

 versity of Texas in Gulf of Mexico. 



Leyden, R. 1973. Salt distribution and crustal models for the 

 eastern Brazilian margin. Cong. Brasileiro de Geologia, 

 Anais, 26th, p. 159-168. 



McKenzie, D., and C. Bowin. 1976. The relationship between 

 bathymetry and gravity in the Atlantic Ocean. J. Geophys. 

 Res. 81: 1903-1915. 



Rabinowitz, P. D., S. C. Cande, and J. L. La Brecque. 1973. 

 The Falkland Escarpment and Agulhas Fracture Zone: 

 the boundary between oceanic and continental basement 

 at conjugate continental margins. Cong. Brasileiro de 

 Geologia, Anais, 26th, p. 241-251. 



Tatham, R. H., and P. L. Stoffa. 1976. Vp/Vs-A potential 

 hydrocarbon indicator. Geophysics 41: 837-849. 



Plate Tectonics and Metallogenesis Studies 



Studies of the origin of ore deposits received new impetus 

 when considered within the plate tectonic framework. The oc- 

 currences of ore deposits along past and present plate boun- 

 daries readily suggest some vital relationship. 



The ore deposit itself and the terrain in which it is found 

 however, is the end product of a long series of geological 

 events, traces of which have often disappeared from the geo- 

 logical record. A series of investigations under the Seabed As- 

 sessment Program are designed to reconstruct the sequence of 

 events that may have led to the concentration of some of the 

 most widely used minerals (especially copper) and thereby 

 provide economic geologists with some exploration tools in 

 the search of new, vital resources. Processes creating new sea 

 floor along the margins of spreading plates appear to generate 

 one type of ore deposit, and those along the margins of con- 

 verging plates appear to form another. Investigations of the 

 Mid-Atlantic Ridge and the Galapagos Spreading Center focus 

 on the sequence of rock units formed by the cooling crustal 

 material and the role of sea floor hydrothermal circulation in 

 the formation of metalliferous sediment deposits. The Nazca 

 Plate Program and the East Asia Study help scientists relate 

 the processes of subduction to the occurrences of mineral de- 

 posits in the adjacent overlying land masses. 



Gorini, M. A., and G. M. Bryan. 1973. The tectonic fabric 

 of the equatorial Atlantic and adjoining continental mar- 

 gins: Gulf of Guinea to northeastern Brazil. Cong. 

 Brasileiro de Geologia, Anais, 26th, p. 101-119. 



Kumar, N., G. M. Bryan, J. C. Carvalho, M. A. Gorini, and 

 J. E. Daniuth. 1974. Summary of REMAC-LDGO co- 

 operative research on the Brazilian continental margin. 

 Part I: Northeastern Brazilian margin. Trans. 28th 

 Brazilian Geol. Congress, Porta Alegre, Brazil, p. 323- 

 334. 



Kumar, N., G. M. Bryan, M. Gorini, and J. Carvalho. 1973. 

 Evolution of the continential margin off northern Brazil: 

 Sediment distribution and carbon potential. Cong. 

 Brasileiro de Geologia, Anais, 26th, 131-143. 



46 



Mid-Atlantic Ridge 



The French-American Mid-Ocean Undersea Study 

 (FAMOUS), a major international program, was the first at- 

 tempt to make first hand observations of the geologic setting 

 and processes of crustal formation along an active spreading 

 center. Investigation of the Mid-Atlantic Ridge was carried 

 out in the series of steps that culminated in 1974 with a deep 

 submersible diving program. In addition to the manned sub- 

 mersible activities, Leg 37 (Deep Sea Drilling Project) drilled 

 into the crustal material along the flank of the Ridge in the 

 FAMOUS area. As part of the comprehensive investigation, 

 deep holes were drilled in the Azores and suites of samples 

 were dredged from the Romanche Fracture Zone. 



The major results of Project FAMOUS are included in 

 April and May 1977 volumes of the Bulletin of the Geological 

 Society of America, vol. 88 nos. 4, 5. 



