Initial Reports of the Deep Sea Drilling Project - Volume 92

This volume covers Leg 92 of the cruises of the Drilling Vessel Glomar Challenger. Leg 92 was undertaken primarily to determine the nature and history of basalt-seawater (or hydrogeology) interactions at and on the flanks of the East Pacific Rise (EPR). The sites surveyed as potential drill sites for the leg lay west of the EPR crest and at 19°S. Placing the transect at 19°S made it possible to investigate hydrothermal activity at the fastest-spreading portion of the world's rift system while avoiding excessive dilution of the hydrothermal sediment component by either terrigenous or biogenic sediment and the resulting complication of the pore water and sediment chemistry by the reducing conditions associated with organic diagenesis. To relate hydrothermal fluid and sediment chemistry to the basalt crust and its structure, we planned to drill a re-entry hole to recover samples of and to complete a logging program in the basalts, which despite their proximity to a fast-spreading ridge were old enough to have undergone alteration. We planned to recover some basalt from each drill site for comparison. The logging program was designed to continue the efforts of the site surveys to locate evidence of ridge flank hydrothermal activity and included the measurement of heat flow and the analysis of pore waters for evidence of fluid advection. A final objective of Leg 92 was to reoccupy Hole 504B, the deep re-entry site in the Panama Basin, for the purpose of downhole temperature measurement, water sampling, a borehole-seismometer refraction survey, and logging and packer experiments. Leg 92 of the Deep Sea Drilling Project traversed the southeast Pacific Ocean from Papeete, Tahiti, to Balboa, Panama. The Glomar Challenger sailed from Papeete on 23 February 1983 and arrived at the entrance to the Panama Canal on 18 April.