Deep Ocean Tracers and Hydrothermal Vents

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Dr. Craig's research in this program has been concerned with the colatile and isotopic chemistry of hydrothermal vents along the Mid-ocean Ridge spreading centers, the fluxes of these fluids into the deepsea, and the study of the deep circulation by use of these tracers (3He) combines with natural radioactive isotopes. During the past two years he has extended the known occurrences of hydrothermal vents to the Back-arc basins of the SW Pacific (Lau, North Fiji, and Manus Basins), to the western Pacific in the Mariana Trough, and to volcanic hotspots such as Loiji Seamount on the Hawaiian hotspot, and East Pacific Rise vents at the Pascua hotspot on the Eastern microplate. This year in two ALVIN diving programs he has sampled 30'C vents in Loihi caldera, and 285'C vents ("clear smokers") in two major hydrothermal areas we discovered in the Mariana Trough. Before the end of 1987 he will run an expedition transect across the two Pacific zonal helium jets in the North and South Pacific, to begin the detailed mapping of these major features of the deep Pacific circulation, New results reported here include details of the 3He, CH4, and Mn relationships in MOR, Hotspot, and Back-arc vents, radiocarbon and stable carbon isotopes in vent fluids, 39Ar and N and O isotopes in N2O, etc. A detailed 77-page Data Report on the SW Pacific Basin studies (Papatua Expedition) has been issued. No new expedition work is planned after 1987, for the next two years. Rather, he intends to complete all the analytical work on the expedition samples and ALVIN programs of 1986-87, and to concentrate on onterpretation and synthesis of the MOR, hotspot, Back-arc, and deep-ocean isotopic and chemical studies.