Presentation on theme: "MoMAR* : suivi à long terme des systèmes hydrothermaux de la dorsale Médio Atlantique près des Açores. * Monitoring the Mid Atlantic Ridge."— Presentation transcript:
MoMAR* : suivi à long terme des systèmes hydrothermaux de la dorsale Médio Atlantique près des Açores. * Monitoring the Mid Atlantic Ridge
Objectifs : dynamique des systèmes (écosystèmes) hydrothermaux de la dorsale Médio-Atlantique Approche : Observations/échantillonnage répétés et Suivi temporel des processus
Axial hydrothermal circulation ….
The objective there is to turn the vent field into a natural laboratory for the study of ultramafic-hosted, iron-rich hydrothermal ecosystems. The experimental design at Rainbow involves instrumented IODP drilling of the hydrothermal stockwerk, as well as extensive site surveys and repeated sampling. Rainbow is an exceptionnal target for the study of ultramafic-hosted ridge hydrothermal systems. This site is characterized by the abundance of iron, an element which plays a major role at all scales in the ecosystem. Rimicaris exoculata: a new type of symbiosis based on iron oxidation Strategy: Focus on the Rainbow and Lucky Strike vent fields: IODP instrumented drilling at Rainbow multiscale long-term monitoring at Lucky Strike.
Strategy: Focus on the Rainbow and Lucky Strike vent fields: IODP instrumented drilling at Rainbow multiscale long-term monitoring at Lucky Strike. Lucky Strike central volcanoe (bathymetry, viewed from SW, east wall of rift valley in background) Lucky Strike : segment center & basalt-hosted hydrothermal site. The objective there is to set up a permanent seafloor observatory to record and relate seismicity, seafloor deformation, fluid flow, temperature and composition, with the dynamics of vent communities (including microbes)
Lucky Strike …. The heat source ….. may be a melt-rich crustal body….. Recent seismic results indicate mid-crustal, « axial magma chamber-type » reflector around at about 3 km depth beneath volcanoe ……. And possible connection with the axial valley bounding faults….. (Singh, Crawford et al., SISMOMAR cruise, in preparation)
MAR (slow) type Hydrothermal vents have been discovered at segment centers (Menez Gwen, Lucky Strike, Broken Spur, Snake Pit), and at segment ends (Menez Hom, Saldanha, Rainbow, Lost City, TAG, Logatchev)…. …. Vents at segment centers are set on a basaltic seafloor…… most segment ends vents are set on serpentinized peridotites…….. Menez Hom MoMAR region