ARE UNDISCOVERED HYDROTHERMAL VENTS IN THE SOUTHERN RED-SEA THE MAIN SOURCE OF SILICA AND HELIUM-3 FOR THE RED-SEA DEEP-WATER

Geochemical Ocean Sections Study (GEOSECS) Indian Ocean Expedition dat a show that silica and He-3 in the Red Sea Deep Water are linearly cor related, suggesting a common hydrothermal source. Silica sections for the Red Sea from the GEOSECS and Mer Rouge (MEROU) expeditions show a strong vertical silica maximum centered at 500 to 600 m depth. The MER OU sections, which have higher horizontal resolution than the GEOSECS sections, suggest that the primary silica source lies in the south at that depth. The interpretation is that the large-scale silica and He-3 distributions are due to the dispersal in the Red Sea Deep Water of w arm or hot hydrothermal vent waters associated with the seafloor sprea ding center of the southern Red Sea. The helium- and silica-rich hot b rines of the central Red Sea probably cannot provide the large fluxes of silica or He-3 required to maintain the inventory of either of thes e deep water properties in steady state. The hypothesis of a common hy drothermal source for silica and He-3 can most readily be tested by me asurements of the germanium-silicon ratio in Red Sea Deep Water.