Galapagos hydrothermal alteration zone found


  • Robert W. Embley

    1. National Oceanic and Atmospheric Administration, Marine Resources Research Division, Hatfield Marine Science Center, Oregon State University, Newport
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In October 1985, a unique outcrop of an alteration zone beneath an extinct massive sulfide deposit was discovered by ALVIN on the Galapagos Ridge at 0°45′N, 85°50′W. This location is about 20 km east of the easternmost of the warm water Galapagos vents (the original ridge crest vent site discovered in 1977). The massive sulfide body, discovered in 1980, consists primarily of pyrite, chalcopyrite, and minor sphalerite. At that time the site was recognized to offer great potential for examining the third dimension of a ridge crest sulfide deposit because of the extensive syn- and postdepositional faulting that had taken place in the area. The 1985 expedition was designed to map the deposit in detail and to examine the fault scarps for stockworklike alteration zones. In addition, deep tow magnetics and ALVIN-based electrical resistivity experiments were carried out.