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 ….
Strategy:
Focus on the Rainbow and Lucky Strike vent
fields:
• IODP instrumented drilling at Rainbow
• multiscale long-term monitoring at
Lucky Strike.
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.
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.
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.
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
MoMAR region
Menez Hom
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……..