of ore formation are encompassed within this larger problem. 

 These processes are investigated from the seaward side along 

 the Peru-Chile Trench, which forms the east boundary of the 

 Nazca Plate and also parallels the major copper deposits of 

 Peru and Chile. 



The major Transects in the SEATAR area are the Sunda, 

 Banda, and Mariana-Philippine cross active subduction zones 

 and areas of significant minerals and hydrocarbons accumu- 

 lation. 



Galapagos Rift Hydrothermal Processes 



The Galapagos Rift, an active spreading center that forms 

 the boundary between the Cocos Plate on the north and the 

 Nazca Plate on the south, is the site of hot springs on the deep- 

 sea floor produced by convective circulation of seawater through 

 newly formed oceanic crust. This conclusion was drawn by a 

 group of U.S. scientists who investigated this area using a num- 

 ber of methods culminating in a program of deep diving by 

 the manned submersible, Alvin. (For a list of projects, see 

 table 1 1.) For several years, surface ship investigations of deep- 

 sea rocks, heat-flow patterns near spreading centers, and metal- 

 rich sediments, all suggested that these seawater hydrothermal 

 systems might be a previously unsuspected process of great 

 importance in controlling the composition of seawater and deep- 

 sea deposits. In addition, there was increasing evidence that 

 a variety of economically important metal deposits on the con- 

 tinents are produced directly or indirectly by this process. 



A joint research effort of scientists from Oregon State Univer- 

 sity (OSU), Woods Hole Oceanographic Institution (WHOI), 

 U.S. Geological Survey (USGS), Massachusetts Institute of 

 Technology (MIT), and Scripps Institution of Oceanography 

 (SIO) was funded in 1976. The project was conceived as a broad 

 study of the phenomena related to hydrothermal activity. 



A preliminary study of 10mi- identified the most promising 

 areas for investigating hydrothermal activity. The submersible 

 work was successfully completed in March 1977 during two 

 20-day legs as indicated from the following list of accomplish- 

 ments: 



1) The first direct observation of deep-sea hydrothermal 

 vents was made. Four major hydrothermal areas were dis- 

 covered, each containing many individual vents. Three 

 extinct vent areas were also found. 



2) Direct temperature measurements from these vents indi- 

 cate that water as much as 15°C warmer than bottom 

 water is issuing from the bottom at the spreading center. 



3) A data acquisition system using the GEOSECS Conduc- 

 tivity/Temperature/Depth (CTD) package and data log- 

 ger was developed for Alvin, which could continuously 

 measure and record in situ oxygen, pH, salinity, and tem- 

 perature of the hydrothermal vents. This package also 

 recorded altitude, depth, gyro, and time from the sub- 

 marine. 



4) Continuous temperature measurements were recorded at 

 one vent for about 10 days. 



5) Eighty-eight 8-1 samples of water were collected from and 

 around the vents, using a newly developed contamination- 

 free sampling system. Literally thousands of subsamples 

 were taken for isotopic and chemical shore-based analyses. 



6) These water samples were analyzed while at sea for alka- 

 linity, ammonia, calcium, chlorinity, hydrogen, hydrogen 

 sulfide, magnesium, nitrates, nitrites, oxygen, pH, phos- 

 phates, radon-222, salinity, and silicon, providing real- 

 time data for guiding the sampling program. 



Table 11.— U.S. institutions, investigators, and projects in the Galapagos Rift Hydrothermal Processes Study 



Institutions 



Investigators 



School of Oceanography, 

 Oregon State University 



Massachusetts Institute 



of Technology 



Woods Hole Oceanographic Institution 



Stanford University 

 U.S. Geological Survey 



J. Corliss 



J. Edmond 



R. P. Von Herzen 

 R. Ballard 



Tj. vanAndel 



D. Williams 



Projects 



Solid Phase Studies: Chemical and Mineralogic 



Studies of Suspended Particulate Material Metal 



Rich Sediments, Manganese Crusts, and Basalt 



Samples 



Chemical Study of Hydrothermal Fluids 



Heat Flow Studies 



Geologic Structure and Tectonic History of Gala- 

 pagos Spreading Center 



Geologic Structure and Tectonic History of Gala- 

 pagos Spreading Center 

 Heat Flow Studies 



57 



