MoMAR : a coordinated and multidisciplinary long-term study of hydrothermal environments at the Mid-Atlantic Ridge / Mo

1. Lucky Strike MoMAR : a coordinated and multidisciplinary long-term study of hydrothermal environments at the Mid-Atlantic Ridge / MoMAR-Fr Poster presented by the national steering committee for the french participation to MoMAR * The MOMAR Area The MOMAR (“Monitoring the Mid-Atlantic Ridge”) project has been developed to promote a coordinated and multidisciplinary long-term study of hydrothermal environments at the Mid-Atlantic Ridge (MAR) near the Azores (36°N to 40°N). This poster gives an outline of the MoMAR project, as last updated in a recent InterRidge international workshop in Lisbon, and a brief update on cruises planned as part of the french participation to MoMAR. Two top targets for monitoring studies: • Slow-spreading Mid-Atlantic Ridge (12 mm/yr half-rate) • In proximity to the Azores • 36°to 40°N - consists of several ridge segments: good targets for establishing integrated studies at regional scale, segment scale, and individual vent sites The Lucky Strike vent field The Rainbow vent field . Mafic-seawater interaction (B, K, Cs, … enrichment) . Two possible circulation systems feeding the vents . Large variability in vent types, T, chemistry… . Large site, > 1 km2 . Marine Protected Area within portuguese EEZ . Ultramafic-mafic-seawater interaction . Low pH (~2.8) fluids, high Fe, H2 concentrations . Synthesis of organic compounds (CH4) . Single source for all fluids (small vent field, ~200 m) . In international waters Lucky Strikeis the selected MOMAR site for integrated & multiscale long-term monitoring of ridge hydrothermal processes and ecosystems. Hydrothermal circulation at mid-ocean ridges is a fundamental process that controls the transfer of energy and matter from the interior of the Earth to the crust, hydrosphere and biosphere. • 4 known vent sites, 3 distinct hydrothermal environments • Peridotite hosted, high T, end of segment - Rainbow • Peridotite hosted, diffuse low T, end of segment - Saldanha • Basalt-hosted, high T, center of segment - Menez Gwen and Lucky Strike Lucky Strike observatory design 2006-2010 The objective there is to set up a permanent seafloor observatory to record seismicity, seafloor deformation, fluid flow, temperature and composition, and the evolution of vent habitats (including microbes). The design shown above reflects planning by international partners at a recent MoMAR meeting in Lisbon. Implementation will begin in 2005-2006 for seafloor deformation and near vents habitat monitoring. In a first stage, sensors will be autonomous or linked acoustically to an ASSEM system. The objective is to provide larger energy supply and data transmission capability (cable system) by 2010. Humphris and McCollum, Oceanus, 41 (2), 1998 Rainbowis an exceptionnal target for the study of ultramafic-hosted hydrothermal systems. This site is characterized by the abundance of iron, an element which plays a major role at all scales in the ecosystem. Objective : to constrain the dynamics of hydrothermal vent ecosystems at mid-ocean ridges Dispersal The Lucky Strike vent field is set on top of a rifted volcanoe, in the centre of the Lucky Strike ridge segment. Hydrothermal Fluxes Hydrothermal Ecosystem Propagule input Photosynthetic seasonal input Magmatic Tectonic Events Biological Interactions Cruises planned & proposed in the french system for the 2005-2007 period: The objective there is to turn the site into a natural laboratory for the study of ultramafic-hosted, iron-rich hydrothermal ecosystems. The experimental design at Rainbow involves IODP drilling of the hydrothermal stockwerk, as well as extensive site surveys and repeated sampling. Planned: EXOMAR (2005, PI Godfroy): Bio/ecological studies of MOMAR sites SISMOMAR (2005, PI W. Crawford): 3D seismic structure of the Lucky Strike segment and central volcano: Porosity of the segment and central volcano, Presence of fluids and heat sources, Velocity structure for microseismicity studies GRAVILUCK (2005/2006, PI V. Ballu): Geodesy and seafloor gravity. Lucky Strike observatory design phase I (Long-term monitoring of seafloor vertical deformation and gravity) MOMARETO (2006, PI Sarradin): Ecosystem studies. Lucky Strike observatory design phase I (Visual and chemical monitoring of vent habitats). Proposed: MOMAR-DREAM (PIs J. Dyment&F. Gaill): site characterization at Rainbow in preparation for future IODP drilling & comprehensive, multidisciplinary study of the role of iron in geological, hydrological and biological processes. MOMARTHYNI (Pis J. Escartin&J. Sarrazin): Lucky Strike observatory design phase I (systematic mapping and visual imaging of vent habitats, geodesy, visual and chemical monitoring of vent habitats). Microbial activity *